WorldWideScience

Sample records for antarctic phytoplankton models

  1. Ozone depletion - Ultraviolet radiation and phytoplankton biology in Antarctic waters

    Science.gov (United States)

    Smith, R. C.; Prezelin, B. B.; Baker, K. S.; Bidigare, R. R.; Boucher, N. P.; Coley, T.; Karentz, D.; Macintyre, S.; Matlick, H. A.; Menzies, D.

    1992-01-01

    The near-50-percent thinning of the stratospheric ozone layer over the Antarctic, with increased passage of mid-UV radiation to the surface of the Southern Ocean, has prompted concern over possible radiation damage to the near-surface phytoplankton communities that are the bases of Antarctic marine ecosystems. As the ozone layer thinned, a 6-week study of the marginal ice zone of the Bellingshousen Sea in the austral spring of 1990 noted sea-surface and depth-dependent ratios of mid-UV irradiance to total irradiance increased, and mid-UV inhibition of photosynthesis increased. A 6-12 percent reduction in primary production associated with ozone depletion was estimated to have occurred over the course of the present study.

  2. Synchronicity between ice retreat and phytoplankton bloom in circum-Antarctic polynyas

    Science.gov (United States)

    Li, Yun; Ji, Rubao; Jenouvrier, Stephanie; Jin, Meibing; Stroeve, Julienne

    2016-03-01

    Phytoplankton in Antarctic coastal polynyas has a temporally short yet spatially variant growth window constrained by ice cover and day length. Using 18-year satellite measurements (1997-2015) of sea ice and chlorophyll concentrations, we assessed the synchronicity between the spring phytoplankton bloom and light availability, taking into account the ice cover and the incident solar irradiance, for 50 circum-Antarctic coastal polynyas. The synchronicity was strong (i.e., earlier ice-adjusted light onset leads to earlier bloom and vice versa) in most of the western Antarctic polynyas but weak in a majority of the eastern Antarctic polynyas. The west-east asymmetry is related to sea ice production rate: the formation of many eastern Antarctic polynyas is associated with strong katabatic wind and high sea ice production rate, leading to stronger water column mixing that could damp phytoplankton blooms and weaken the synchronicity.

  3. Southern Ocean phytoplankton turnover in response to stepwise Antarctic cooling over the past 15 million years

    Science.gov (United States)

    Crampton, James S.; Cody, Rosie D.; Levy, Richard; Harwood, David; McKay, Robert; Naish, Tim R.

    2016-06-01

    It is not clear how Southern Ocean phytoplankton communities, which form the base of the marine food web and are a crucial element of the carbon cycle, respond to major environmental disturbance. Here, we use a new model ensemble reconstruction of diatom speciation and extinction rates to examine phytoplankton response to climate change in the southern high latitudes over the past 15 My. We identify five major episodes of species turnover (origination rate plus extinction rate) that were coincident with times of cooling in southern high-latitude climate, Antarctic ice sheet growth across the continental shelves, and associated seasonal sea-ice expansion across the Southern Ocean. We infer that past plankton turnover occurred when a warmer-than-present climate was terminated by a major period of glaciation that resulted in loss of open-ocean habitat south of the polar front, driving non-ice adapted diatoms to regional or global extinction. These findings suggest, therefore, that Southern Ocean phytoplankton communities tolerate “baseline” variability on glacial–interglacial timescales but are sensitive to large-scale changes in mean climate state driven by a combination of long-period variations in orbital forcing and atmospheric carbon dioxide perturbations.

  4. Southern Ocean phytoplankton turnover in response to stepwise Antarctic cooling over the past 15 million years

    Science.gov (United States)

    Crampton, James S.; Cody, Rosie D.; Levy, Richard; Harwood, David; McKay, Robert; Naish, Tim R.

    2016-06-01

    It is not clear how Southern Ocean phytoplankton communities, which form the base of the marine food web and are a crucial element of the carbon cycle, respond to major environmental disturbance. Here, we use a new model ensemble reconstruction of diatom speciation and extinction rates to examine phytoplankton response to climate change in the southern high latitudes over the past 15 My. We identify five major episodes of species turnover (origination rate plus extinction rate) that were coincident with times of cooling in southern high-latitude climate, Antarctic ice sheet growth across the continental shelves, and associated seasonal sea-ice expansion across the Southern Ocean. We infer that past plankton turnover occurred when a warmer-than-present climate was terminated by a major period of glaciation that resulted in loss of open-ocean habitat south of the polar front, driving non-ice adapted diatoms to regional or global extinction. These findings suggest, therefore, that Southern Ocean phytoplankton communities tolerate “baseline” variability on glacial-interglacial timescales but are sensitive to large-scale changes in mean climate state driven by a combination of long-period variations in orbital forcing and atmospheric carbon dioxide perturbations.

  5. Southern Ocean phytoplankton turnover in response to stepwise Antarctic cooling over the past 15 million years.

    Science.gov (United States)

    Crampton, James S; Cody, Rosie D; Levy, Richard; Harwood, David; McKay, Robert; Naish, Tim R

    2016-06-21

    It is not clear how Southern Ocean phytoplankton communities, which form the base of the marine food web and are a crucial element of the carbon cycle, respond to major environmental disturbance. Here, we use a new model ensemble reconstruction of diatom speciation and extinction rates to examine phytoplankton response to climate change in the southern high latitudes over the past 15 My. We identify five major episodes of species turnover (origination rate plus extinction rate) that were coincident with times of cooling in southern high-latitude climate, Antarctic ice sheet growth across the continental shelves, and associated seasonal sea-ice expansion across the Southern Ocean. We infer that past plankton turnover occurred when a warmer-than-present climate was terminated by a major period of glaciation that resulted in loss of open-ocean habitat south of the polar front, driving non-ice adapted diatoms to regional or global extinction. These findings suggest, therefore, that Southern Ocean phytoplankton communities tolerate "baseline" variability on glacial-interglacial timescales but are sensitive to large-scale changes in mean climate state driven by a combination of long-period variations in orbital forcing and atmospheric carbon dioxide perturbations. PMID:27274061

  6. Effects of UV on photosynthesis of Antarctic phytoplankton: models and their application to coastal and pelagic assemblages Efecto de la radiación UV sobre la fotosíntesis de fitoplancton antártico: modelos y su aplicación a ensambles costeros y pelágicos

    OpenAIRE

    Neale, Patrick J.; JENNIFER J. FRITZ; Davis, Richard F.

    2001-01-01

    We have characterized the photosynthetic response to ultraviolet radiation (UV) of natural phytoplankton assemblages in Antarctic (Southern Ocean) waters. Biological weighting functions (BWFs) and exposure response curves for inhibition of photosynthesis by UV were measured during spring-time ozone depletion (October-November). Two different models were developed to relate photosynthesis to UV exposure. A model that is a function of the duration of exposure (BWF H) applied to assemblages in t...

  7. Controls of primary production in two phytoplankton blooms in the Antarctic Circumpolar Current

    NARCIS (Netherlands)

    Hoppe, C.J.M.; Klaas, C.; Ossebaar, S.; Soppa, M.A.; Cheah, W.; Laglera, L.M.; Santos-Echeandia, J.; Rost, B.; Wolf-Gladrow, D.A.; Bracher, A.; Hoppema, M.; Strass, V.

    2016-01-01

    The Antarctic Circumpolar Current has a high potential for primary production and carbon sequestration through the biological pump. In the current study, two large-scale blooms observed in 2012 during a cruise with R.V. Polarstern were investigated with respect to phytoplankton standing stocks, prim

  8. Phytoplankton abundance and community structure in the Antarctic polar frontal region during austral summer of 2009

    Institute of Scientific and Technical Information of China (English)

    SHRAMIK Patil; RAHUL Mohan; SUHAS Shetye; SAHINA Gazi

    2013-01-01

    The Antarctic polar front region in the Southern Ocean is known to be most productive.We studied the phytoplankton community structure in the Indian sector at this frontal location during late austral summer (February,2009) onboard R/V Akademic Boris Petrov.We used the phytoplankton and microheterotrophs abundance,as also the associated physico-chemical parameters to explain the low phytoplankton abundance in the study region.This study emphasizes the shift of phytoplankton,from large (>10 μm) to small (<10 μm) size.The phytoplankton abundance appears to be controlled by physical parameters and by nutrient concentrations and also by the microheterotrophs (ciliates and dinoflagellates) which exert a strong grazing pressure.This probably reduces small (<10 μm) and large (>10 μm)phytoplankton abundance during the late austral summer.This study highlights the highly productive polar front nevertheless becomes a region of low phytoplankton abundance,due to community shifts towards pico-phytoplankton (<10 μm) during late austral summer.

  9. Modelling the Antarctic Ice Sheet

    DEFF Research Database (Denmark)

    Pedersen, Jens Olaf Pepke; Holm, A.

    2015-01-01

    The Antarctic ice sheet is a major player in the Earth’s climate system and is by far the largest depository of fresh water on the planet. Ice stored in the Antarctic ice sheet (AIS) contains enough water to raise sea level by about 58 m, and ice loss from Antarctica contributed significantly...... Science) Antarctic Ice Sheet (DAIS) model (Shaffer 2014) is forced by reconstructed time series of Antarctic temperature, global sea level and ocean subsurface temperature over the last two glacial cycles. In this talk a modelling work of the Antarctic ice sheet over most of the Cenozoic era using...... the DAIS model will be presented. G. Shaffer (2014) Formulation, calibration and validation of the DAIS model (version 1), a simple Antarctic ice sheet model sensitive to variations of sea level and ocean subsurface temperature, Geosci. Model Dev., 7, 1803‐1818...

  10. Primary productivity, phytoplankton standing crop and physico-chemical characteristics of the Antarctic and adjacent central Indian Ocean waters

    Digital Repository Service at National Institute of Oceanography (India)

    JiyalalRam, M.

    Primary productivity, phytoplankton pigments and physico-chemical properties were studied in Antarctic waters and adjoining Indian Ocean between 11 degrees and 67 degrees E longitudes from polynya region (60 degrees S) to equator during the austral...

  11. The dynamics of nutrient, toxic phytoplankton, nontoxic phytoplankton and zooplankton model

    Directory of Open Access Journals (Sweden)

    Hasnaa Fiesal Mohammed Hussien

    2016-02-01

    Full Text Available The objective of this paper is to study the dynamical behavior of an aquatic food web system. A mathematical model that includes nutrients, phytoplankton and zooplankton is proposed and analyzed. It is assumed that, the phytoplankton divided into two compartments namely toxic phytoplankton which produces a toxic substance as a defensive strategy against predation by zooplankton, and a nontoxic phytoplankton. All the feeding processes in this food web are formulating according to the Lotka-Volterra functional response. This model is represented mathematically by the set of nonlinear differential equations. The existence, uniqueness and boundedness of the solution of this model are investigated. The local and global stability conditions of all possible equilibrium points are established. The occurrence of local bifurcation and Hopf bifurcation are investigated. Finally, numerical simulation is used to study the global dynamics of this model.

  12. Standing crop and growth rates of net phytoplankton and nanoplankton in Antarctic waters

    Digital Repository Service at National Institute of Oceanography (India)

    Goes, J.I.; Fondekar, S.P.; Parulekar, A.H.

    stream_size 16 stream_content_type text/plain stream_name Proc_Workshop_Antarct_Stud_1990_419.pdf.txt stream_source_info Proc_Workshop_Antarct_Stud_1990_419.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset...

  13. A vertically resolved model for phytoplankton aggregation

    Indian Academy of Sciences (India)

    Iris Kriest; Geoffrey T Evans

    2000-12-01

    This work presents models of the vertical distribution and flux of phytoplankton aggregates, including changes with time in the distribution of aggregate sizes and sinking speeds. The distribution of sizes is described by two parameters, the mass and number of aggregates, which greatly reduces the computational cost of the models. Simple experiments demonstrate the effects of aggregation on the timing and depth distribution of primary production and export. A more detailed ecological model is applied to sites in the Arabian Sea; it demonstrates that aggregation can be important for deep sedimentation even when its effect on surface concentrations is small, and it presents the difference in timing between settlement of aggregates and fecal pellets.

  14. Effects of UV on photosynthesis of Antarctic phytoplankton: models and their application to coastal and pelagic assemblages Efecto de la radiación UV sobre la fotosíntesis de fitoplancton antártico: modelos y su aplicación a ensambles costeros y pelágicos

    Directory of Open Access Journals (Sweden)

    PATRICK J. NEALE

    2001-06-01

    Full Text Available We have characterized the photosynthetic response to ultraviolet radiation (UV of natural phytoplankton assemblages in Antarctic (Southern Ocean waters. Biological weighting functions (BWFs and exposure response curves for inhibition of photosynthesis by UV were measured during spring-time ozone depletion (October-November. Two different models were developed to relate photosynthesis to UV exposure. A model that is a function of the duration of exposure (BWF H applied to assemblages in the well-mixed open waters of the Weddell-Scotia Confluence (WSC, 60° S, 50° W, since responses were a function of cumulative exposure and recovery rates were slow. These assemblages had a variable but generally high sensitivity to UV. A steady-state model (BWF E applied in the shallow waters near the Antarctic Peninsula (Palmer Station, 64° S, 64° W, where inhibition was a function of irradiance (reciprocity failed, and recovery was rapid. Using information on the time-dependence of photosynthesis in assemblages with active repair, inferences were drawn on the relative contribution of damage and recovery processes to the UV weights. BWFs for Palmer phytoplankton sampled during periods of pack-ice cover had both higher damage and higher repair than BWFs for WSC assemblages. BWFs for Palmer phytoplankton sampled during open water periods had about the same damage weights as Weddell-Scotia assemblages but had a higher repair rate. Solar exposures of more than 10 min were predicted to have generally less effect on Palmer phytoplankton than the WSC phytoplanktonSe caracterizó la respuesta fotosintética a radiación ultravioleta (RUV en poblaciones naturales de fitoplancton del Océano Antártico. Se midieron las funciones espectrales de peso biológico (BWFs y curvas de inhibición de fotosíntesis en respuesta a la exposición de RUV durante la temporada de mayor disminución de la capa de ozono (octubre-noviembre. Se desarrollaron dos modelos distintos que

  15. Phytoplankton-bacterial interactions mediate micronutrient colimitation at the coastal Antarctic sea ice edge.

    Science.gov (United States)

    Bertrand, Erin M; McCrow, John P; Moustafa, Ahmed; Zheng, Hong; McQuaid, Jeffrey B; Delmont, Tom O; Post, Anton F; Sipler, Rachel E; Spackeen, Jenna L; Xu, Kai; Bronk, Deborah A; Hutchins, David A; Allen, Andrew E

    2015-08-11

    Southern Ocean primary productivity plays a key role in global ocean biogeochemistry and climate. At the Southern Ocean sea ice edge in coastal McMurdo Sound, we observed simultaneous cobalamin and iron limitation of surface water phytoplankton communities in late Austral summer. Cobalamin is produced only by bacteria and archaea, suggesting phytoplankton-bacterial interactions must play a role in this limitation. To characterize these interactions and investigate the molecular basis of multiple nutrient limitation, we examined transitions in global gene expression over short time scales, induced by shifts in micronutrient availability. Diatoms, the dominant primary producers, exhibited transcriptional patterns indicative of co-occurring iron and cobalamin deprivation. The major contributor to cobalamin biosynthesis gene expression was a gammaproteobacterial population, Oceanospirillaceae ASP10-02a. This group also contributed significantly to metagenomic cobalamin biosynthesis gene abundance throughout Southern Ocean surface waters. Oceanospirillaceae ASP10-02a displayed elevated expression of organic matter acquisition and cell surface attachment-related genes, consistent with a mutualistic relationship in which they are dependent on phytoplankton growth to fuel cobalamin production. Separate bacterial groups, including Methylophaga, appeared to rely on phytoplankton for carbon and energy sources, but displayed gene expression patterns consistent with iron and cobalamin deprivation. This suggests they also compete with phytoplankton and are important cobalamin consumers. Expression patterns of siderophore- related genes offer evidence for bacterial influences on iron availability as well. The nature and degree of this episodic colimitation appear to be mediated by a series of phytoplankton-bacterial interactions in both positive and negative feedback loops. PMID:26221022

  16. An Inverse Modeling Approach to Estimating Phytoplankton Pigment Concentrations from Phytoplankton Absorption Spectra

    Science.gov (United States)

    Moisan, John R.; Moisan, Tiffany A. H.; Linkswiler, Matthew A.

    2011-01-01

    Phytoplankton absorption spectra and High-Performance Liquid Chromatography (HPLC) pigment observations from the Eastern U.S. and global observations from NASA's SeaBASS archive are used in a linear inverse calculation to extract pigment-specific absorption spectra. Using these pigment-specific absorption spectra to reconstruct the phytoplankton absorption spectra results in high correlations at all visible wavelengths (r(sup 2) from 0.83 to 0.98), and linear regressions (slopes ranging from 0.8 to 1.1). Higher correlations (r(sup 2) from 0.75 to 1.00) are obtained in the visible portion of the spectra when the total phytoplankton absorption spectra are unpackaged by multiplying the entire spectra by a factor that sets the total absorption at 675 nm to that expected from absorption spectra reconstruction using measured pigment concentrations and laboratory-derived pigment-specific absorption spectra. The derived pigment-specific absorption spectra were further used with the total phytoplankton absorption spectra in a second linear inverse calculation to estimate the various phytoplankton HPLC pigments. A comparison between the estimated and measured pigment concentrations for the 18 pigment fields showed good correlations (r(sup 2) greater than 0.5) for 7 pigments and very good correlations (r(sup 2) greater than 0.7) for chlorophyll a and fucoxanthin. Higher correlations result when the analysis is carried out at more local geographic scales. The ability to estimate phytoplankton pigments using pigment-specific absorption spectra is critical for using hyperspectral inverse models to retrieve phytoplankton pigment concentrations and other Inherent Optical Properties (IOPs) from passive remote sensing observations.

  17. Simulation of the effects of naturally enhanced UV-radiation on photosynthesis of Antarctic phytoplankton

    OpenAIRE

    Bracher, Astrid; Wiencke, Christian

    2000-01-01

    ABSTRACT: The effects of spectral exposure corresponding tonormal and depleted stratospheric ozone concentrations onphotosynthesis and mycosporine-like amino acids (MAAs)contents of different natural phytoplankton communities werestudied in early austral summer 1995/1996 during the JGOFS ANTXIII/2 cruise in the Atlantic Sector of the Southern Ocean. Theradiation conditions were simulated in a special solar simulator inwhich the same sample was incubated under 2 light regimesdiffering in UV-B ...

  18. Synergistic effects of iron and temperature on Antarctic phytoplankton and microzooplankton assemblages

    Directory of Open Access Journals (Sweden)

    J. M. Rose

    2009-12-01

    Full Text Available Iron availability and temperature are important limiting factors for the biota in many areas of the world ocean, and both have been predicted to change in future climate scenarios. However, the impacts of combined changes in these two key factors on microbial trophic dynamics and nutrient cycling are unknown. We examined the relative effects of iron addition (+1 nM and increased temperature (+4°C on plankton assemblages of the Ross Sea, Antarctica, a region characterized by annual algal blooms and an active microbial community. Increased iron and temperature individually had consistently significant but relatively minor positive effects on total phytoplankton abundance, phytoplankton and microzooplankton community composition, as well as photosynthetic parameters and nutrient drawdown. Unexpectedly, increased iron had a consistently negative impact on microzooplankton abundance, most likely a secondary response to changes in phytoplankton community composition. When iron and temperature were increased in concert, the resulting interactive effects were greatly magnified. This synergy between iron and temperature increases would not have been predictable by examining the effects of each variable individually. Our results suggest the possibility that if iron availability increases under future climate regimes, the impacts of predicted temperature increases on plankton assemblages in polar regions could be significantly enhanced. Such synergistic and antagonistic interactions between individual climate change variables highlight the importance of multivariate studies for marine global change experiments.

  19. Patchiness in a minimal nutrient – phytoplankton model

    Indian Academy of Sciences (India)

    Hiroshi Serizawa; Takashi Amemiya; Kiminori Itoh

    2008-09-01

    We present a minimal two-component model that can exhibit various types of spatial patterns including patchiness. The model, comprising nutrients and phytoplankton, includes the effect of nutrient uptake by phytoplankton as a Holling type II functional response, and also includes the effect of zooplankton grazing on phytoplankton as a Holling type II non-dynamical term. The mean-field model without the diffusion and advection terms shows both bistability and limit-cycle oscillations as a few parameters such as the input rate of nutrients and the maximum feeding rate of zooplankton are changed. If the parameter values are chosen from the limit-cycle oscillation region, the corresponding reaction–advection–diffusion equations show spatial pattern formations by the combined effects of advection and diffusion by turbulent stirring and mixing, and biological interactions. As the nutrient input is increased, the system behaviour changes from the extinction of the entire phytoplankton to the formation of filamentous patterns, patchiness patterns and homogeneous distributions. These observations suggest that the spatial pattern of phytoplankton can function as an indicator to evaluate the eutrophication level in aquatic ecosystems.

  20. Early spawning of Antarctic krill in the Scotia Sea is fuelled by “superfluous” feeding on non-ice associated phytoplankton blooms

    Science.gov (United States)

    Schmidt, Katrin; Atkinson, Angus; Venables, Hugh J.; Pond, David W.

    2012-01-01

    The spawning success of Antarctic krill ( Euphausia superba) is generally assumed to depend on substantial winter sea ice extent, as ice biota can serve as a food source during winter/spring and the seasonal ice melt conditions the upper water column for extensive phytoplankton blooms. However, direct observations during spring are rare. Here we studied krill body condition and maturity stage in relation to feeding (i.e. stomach fullness, diet, absorption of individual fatty acids and defecation rate) across the Scotia Sea in November 2006. The phytoplankton concentrations were low at the marginal ice zone (MIZ) in the southern Scotia Sea (Stn. 1, 2, and 3), high in open waters of the Southern Antarctic Circumpolar Current Front (SACCF) in the central Scotia Sea (Stn. 5), and moderate further north (Stn. 6 and 7). Krill had low lipid reserves (˜6.5% of dry mass, DM), low mass:length ratios (˜1.7 mg DM mm -1), and small digestive glands (˜7% of total DM) near the ice edge. The stomachs contained lithogenic particles, diatom debris, and bacterial fatty acids, but low proportions of diatom-indicating fatty acids, which suggest that these krill were feeding on detritus rather than on fresh ice algae. In the SACCF, krill had higher lipid reserves (˜10% of DM), high mass:length ratios (˜2.2 mg DM mm -1), and large digestive glands (˜16% of total DM). Stomach content and tissue composition indicate feeding on diatoms. In the north, moderate food concentrations co-occurred with low lipid reserves in krill, and moderate mass:length ratios and digestive gland sizes. Only in the phytoplankton bloom in the SACCF had the mating season already started and some females were about to spawn. Based on the way krill processed their food at the different stations, we indicate two mechanisms that can lead to fast regeneration of body reserves and oocyte maturation in E. superba. One is "superfluous" feeding at high food concentrations, which maximises the overall nutrient gain

  1. Dynamical Analysis of a Nitrogen-Phosphorus-Phytoplankton Model

    Directory of Open Access Journals (Sweden)

    Yunli Deng

    2015-01-01

    Full Text Available This paper presents a nitrogen-phosphorus-phytoplankton model in a water ecosystem. The main aim of this research is to analyze the global system dynamics and to study the existence and stability of equilibria. It is shown that the phytoplankton-eradication equilibrium is globally asymptotically stable if the input nitrogen concentration is less than a certain threshold. However, the coexistence equilibrium is globally asymptotically stable as long as it exists. The system is uniformly persistent within threshold values of certain key parameters. Finally, to verify the results, numerical simulations are provided.

  2. Modelling the production of dimethylsulfide during a phytoplankton bloom

    Science.gov (United States)

    Gabric, Albert; Murray, Nicholas; Stone, Lewi; Kohl, Manfred

    1993-12-01

    Dimethylsulfide (DMS) is an important sulfur-containing atmospheric trace gas of marine biogenic origin. DMS emitted from the oceans may be a precursor of tropospheric aerosols and cloud condensation nuclei (CCN), thereby affecting the Earth's radiative balance and possibly constituting a negative feedback to global warming, although this hypothesis is still somewhat controversial. The revised conceptual model of the marine pelagic food web gives a central role to planktonic bacteria. Recent experiments have shown that consumption of dissolved DMS by microbial metabolism may be more important than atmospheric exchange in controlling its concentration in surface waters and hence its ventilation to the atmosphere. In this paper we investigate the effect of the marine food web on cycling of dissolved DMS in surface waters during a phytoplankton bloom episode. A nitrogen-based flow network simulation model has been used to analyze the relative importance of the various biological and chemical processes involved. The model predictions suggest that the concentration of DMS in marine surface waters is indeed governed by bacterial metabolism. Environmental factors that affect the bacterial compartment are thus likely to have a relatively large influence on dissolved DMS concentrations. The ecological succession is particularly sensitive to the ratio of phytoplankton to bacterial nutrient uptake rates as well the interaction between herbivore food chain and the microbial loop. Importantly for the design of field studies, the model predicts that peak DMS concentrations are achieved during the decline of the phytoplankton bloom with a typical time lag between peak DMS and peak phytoplankton biomass of 1 to 2 days. Significantly, the model predicts a relatively high DMS concentration persisting after the phytoplankton bloom due to excretion from large protozoa and zooplankton, which may be an additional explanation for the lack of correlation between DMS and chlorophyll a

  3. Sensitivity in forward modeled hyperspectral reflectance due to phytoplankton groups

    Science.gov (United States)

    Manzo, Ciro; Bassani, Cristiana; Pinardi, Monica; Giardino, Claudia; Bresciani, Mariano

    2016-04-01

    Phytoplankton is an integral part of the ecosystem, affecting trophic dynamics, nutrient cycling, habitat condition, and fisheries resources. The types of phytoplankton and their concentrations are used to describe the status of water and the processes inside of this. This study investigates bio-optical modeling of phytoplankton functional types (PFT) in terms of pigment composition demonstrating the capability of remote sensing to recognize freshwater phytoplankton. In particular, a sensitivity analysis of simulated hyperspectral water reflectance (with band setting of HICO, APEX, EnMAP, PRISMA and Sentinel-3) of productive eutrophic waters of Mantua lakes (Italy) environment is presented. The bio-optical model adopted for simulating the hyperspectral water reflectance takes into account the reflectance dependency on geometric conditions of light field, on inherent optical properties (backscattering and absorption coefficients) and on concentrations of water quality parameters (WQPs). The model works in the 400-750nm wavelength range, while the model parametrization is based on a comprehensive dataset of WQP concentrations and specific inherent optical properties of the study area, collected in field surveys carried out from May to September of 2011 and 2014. The following phytoplankton groups, with their specific absorption coefficients, a*Φi(λ), were used during the simulation: Chlorophyta, Cyanobacteria with phycocyanin, Cyanobacteria and Cryptophytes with phycoerythrin, Diatoms with carotenoids and mixed phytoplankton. The phytoplankton absorption coefficient aΦ(λ) is modelled by multiplying the weighted sum of the PFTs, Σpia*Φi(λ), with the chlorophyll-a concentration (Chl-a). To highlight the variability of water reflectance due to variation of phytoplankton pigments, the sensitivity analysis was performed by keeping constant the WQPs (i.e., Chl-a=80mg/l, total suspended matter=12.58g/l and yellow substances=0.27m-1). The sensitivity analysis was

  4. Maneuver simulation model of an experimental hovercraft for the Antarctic

    Science.gov (United States)

    Murao, Rinichi

    Results of an investigation of a hovercraft model designed for Antarctic conditions are presented. The buoyancy characteristics, the propellant control system, and simulation model control are examined. An ACV (air cushion vehicle) model of the hovercraft is used to examine the flexibility and friction of the skirt. Simulation results are presented which show the performance of the hovercraft.

  5. Potential feedback mechanism between phytoplankton and upper ocean circulation with oceanic radiative transfer processes influenced by phytoplankton - Numerical ocean, general circulation models and an analytical solution

    Digital Repository Service at National Institute of Oceanography (India)

    Nakamoto, S.; Kano, M.; PrasannaKumar, S.; Oberhuber, J.M.; Muneyama, K.; Ueyoshi, K.; Subrahmanyam, B.; Nakata, K.; Lai, C.A.; Frouin, R.

    =UTF-8 Chapter 11 Potential Feedback Mechanism Between Phytoplankton and Upper Ocean Circulation with Oceanic Radiative Transfer Processes Influenced by Phytoplankton - Numerical Ocean General Circulation Models and an Analytical... isoPYcnal coordinate (BPYC) general circulation model (Oberhuber, 1993), Nakamoto et al. (2001) showed that surface chlorophyll pigments in the equatorial Pacific not only influence vertical penetration of solar ra- diation, but also modify...

  6. Tidal Prism Modeling of Phytoplankton and Nitrogen Concentrations in Narragansett Bay and its Sub-Embayments

    Science.gov (United States)

    A tidal prism model was developed to calculate temporal changes in the spatially averaged concentration of three state variables: phytoplankton, dissolved inorganic nitrogen, and detritus. Our main objective was to develop a model to help us understand the causes of phytoplankton...

  7. Antarctic deep-sea meiofauna and bacteria react to the deposition of particulate organic matter after a phytoplankton bloom

    Science.gov (United States)

    Veit-Köhler, Gritta; Guilini, Katja; Peeken, Ilka; Sachs, Oliver; Sauter, Eberhard J.; Würzberg, Laura

    2011-10-01

    During the RV Polarstern ANT XXIV-2 cruise to the Southern Ocean and the Weddell Sea in 2007/2008, sediment samples were taken during and after a phytoplankton bloom at 52°S 0°E. The station, located at 2960 m water depth, was sampled for the first time at the beginning of December 2007 and revisited at the end of January 2008. Fresh phytodetritus originating from the phytoplankton bloom first observed in the water column had reached the sea floor by the time of the second visit. Absolute abundances of bacteria and most major meiofauna taxa did not change between the two sampling dates. In the copepods, the second most abundant meiofauna taxon after the nematodes, the enhanced input of organic material did not lead to an observable increase of reproductive effort. However, significantly higher relative abundances of meiofauna could be observed at the sediment surface after the remains of the phytoplankton bloom reached the sea floor. Vertical shifts in meiofauna distribution between December and January may be related to changing pore-water oxygen concentration, total sediment fatty acid content, and pigment profiles measured during our study. Higher oxygen consumption after the phytoplankton bloom may have resulted from an enhanced respiratory activity of the living benthic component, as neither meiofauna nor bacteria reacted with an increase in individual numbers to the food input from the water column. Based on our results, we infer that low temperatures and ecological strategies are the underlying factors for the delayed response of benthic deep-sea copepods, in terms of egg and larval production, to the modified environmental situation.

  8. Effects of the feeding functional response on phytoplankton diversity and ecosystem functioning in ecosystem models

    OpenAIRE

    Prowe, Friederike

    2011-01-01

    The thesis presents simulations of phytoplankton diversity in the global ocean performed with a coupled ocean-ecosystem model. It demonstrates the effect of different zooplankton feeding formulations on phytoplankton diversity and its consequences for ecosystem productivity. In addition, a more sophisticated feeding formulation is presented.

  9. Modeling the influence from ocean transport, mixing and grazing on phytoplankton diversity

    DEFF Research Database (Denmark)

    Adjou, Mohamed; Bendtsen, Jørgen; Richardson, Katherine

    2012-01-01

    Phytoplankton diversity, whether defined on the basis of functional groups or on the basis of numbers of individual species, is known to be heterogeneous throughout the global ocean. The factors regulating this diversity are generally poorly understood, although access to limiting nutrients and...... light is known to influence distributions for certain groups of phytoplankton. Here, we develop a simple box model of biomasses and a limiting nutrient to describe the composition of phytoplankton communities in the euphotic zone. In addition to analyzing the relative importance of nutrient availability...... in generating and maintaining diversity, we apply the model to quantify the potential role of zooplankton grazing and ocean transport for the coexistence of competing species and phytoplankton diversity. We analyze the sensitivity of phytoplankton biomass distributions to different types of grazing...

  10. The South Atlantic in the Fine-Resolution Antarctic Model

    Directory of Open Access Journals (Sweden)

    D. P. Stevens

    Full Text Available The geographical area covered by the Fine-Resolution Antarctic Model (FRAM includes that part of the South Atlantic south of 24°S. A description of the dynamics and thermodynamics of this region of the model is presented. Both the mean and eddy fields in the model are in good agreement with reality, although the magnitude of the transients is somewhat reduced. The heat flux is northward and in broad agreement with many other estimates. Agulhas eddies are formed by the model and propagate westward into the Atlantic providing a mechanism for fluxing heat from the Indian Ocean. The confluence of the Brazil and Falkland currents produces a strong front and a large amount of mesoscale activity. In the less stratified regions to the south, topographic steering of the Antarctic circumpolar current is important.

  11. Dynamical Complexity of a Spatial Phytoplankton-Zooplankton Model with an Alternative Prey and Refuge Effect

    Directory of Open Access Journals (Sweden)

    Weiwei Zhang

    2013-01-01

    Full Text Available The spatiotemporal dynamics of a phytoplankton-zooplankton model with an alternative prey and refuge effect is investigated mathematically and numerically. The stability of the equilibrium point and the traveling wave solution of the phytoplankton-zooplankton model are described based on theoretical mathematical work, which provides the basis of the numerical simulation. The numerical analysis shows that refuges have a strong effect on the spatiotemporal dynamics of the model according to the pattern formation. These results may help us to understand prey-predator interactions in water ecosystems. They are also relevant to research into phytoplankton-zooplankton ecosystems.

  12. Effects of tidal shallowing and deepening on phytoplankton production dynamics: A modeling study

    Science.gov (United States)

    Lucas, L.V.; Cloern, J.E.

    2002-01-01

    Processes influencing estuarine phytoplankton growth occur over a range of time scales, but many conceptual and numerical models of estuarine phytoplankton production dynamics neglect mechanisms occurring on the shorter (e.g., intratidal) time scales. We used a numerical model to explore the influence of short time-scale variability in phytoplankton sources and sinks on long-term growth in an idealized water column that shallows and deepens with the semidiurnal tide. Model results show that tidal fluctuations in water surface elevation can determine whether long-term phytoplankton growth is positive or negative. Hourly-scale interactions influencing weekly-scale to monthly-scale phytoplankton dynamics include intensification of the depth-averaged benthic grazing effect by water column shallowing and enhancement of water column photosynthesis when solar noon coincides with low tide. Photosynthesis and benthic consumption may modulate over biweekly time scales due to spring-neap fluctuations in tidal range and the 15-d cycle of solar noon-low tide phasing. If tidal range is a large fraction of mean water depth, then tidal shallowing and deepening may significantly influence net phytoplankton growth. In such a case, models or estimates of long-term phytoplankton production dynamics that neglect water surface fluctuations may overestimate or underestimate net growth and could even predict the wrong sign associated with net growth rate.

  13. Ecological controls on biogeochemical lfuxes in the western Antarctic Peninsula studied with an inverse foodweb model

    Institute of Scientific and Technical Information of China (English)

    Hugh W Ducklow; S C Doney; S F Sailley

    2015-01-01

    Sea ice in the western Antarctic Peninsula (WAP) region is both highly variable and rapidly changing. In the Palmer Station region, the ice season duration has decreased by 92 d since 1978. The sea-ice changes affect ocean stratification and freshwater balance and in turn impact every component of the polar marine ecosystem. Long-term observations from the WAP nearshore and offshore regions show a pattern of chlorophyll (Chl) variability with three to ifve years of negative Chl anomalies interrupted by one or two years of positive anomalies (high and low Chl regimes). Both ifeld observations and results from an inverse food-web model show that these high and low Chl regimes differed significantly from each other, with high primary productivity and net community production (NCP) and other rates associated with the high Chl years and low rates with low Chl years. Gross primary production rates (GPP) averaged 30 mmolC.m-2.d-1 in the low Chl years and 100 mmolC.m-2.d-1 in the high Chl years. Both large and small phytoplankton were more abundant and more productive in high Chl years than in low Chl years. Similarly, krill were more important as grazers in high Chl years, but did not differ from microzooplankton in high or low Chl years. Microzooplankton did not differ between high and low Chl years. Net community production differed signiifcantly between high and low Chl years, but mobilized a similar proportion of GPP in both high and low Chl years. The composition of the NCP was uniform in high and low Chl years. These results emphasize the importance of microbial components in the WAP plankton system and suggest that food webs dominated by small phytoplankton can have pathways that funnel production into NCP, and likely, export.

  14. Global response to solar radiation absorbed by phytoplankton in a coupled climate model

    OpenAIRE

    Patara, L.; CMCC; Vichi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Masina, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Fogli, P. G.; CMCC; Manzini, E.; MPI, Hamburg

    2012-01-01

    The global climate response to solar radiation absorbed by phytoplankton is investigated by performing multi-century simulations with a coupled ocean–atmosphere-biogeochemistry model. The absorption of solar radiation by phytoplankton increases radiative heating in the near-surface ocean and raises sea surface temperature (SST) by overall ~0.5°C. The resulting increase in evaporation enhances specific atmospheric humidity by 2–5%, thereby increasing the Earth’s greenhouse effect and the atmos...

  15. A model of the Antarctic Ice Sheet

    NARCIS (Netherlands)

    Oerlemans, J.

    1982-01-01

    Numerical modelling of ice sheets and glaciers has become a useful tool in glaciological research. A model described here deals with the vertical mean ice velocity, is time dependent, computes bedrock adjustment and uses an empirical diagnostic relationship to derive the distribution of ice thicknes

  16. Antarctic clouds

    OpenAIRE

    Lachlan-Cope, Tom

    2010-01-01

    Sensitivity studies with global climate models show that, by their influence on the radiation balance, Antarctic clouds play a major role in the climate system, both directly at high southern latitudes and indirectly globally, as the local circulation changes lead to global teleconnections. Unfortunately, observations of cloud distribution in the Antarctic are limited and often of low quality because of the practical difficulty in observing clouds in the harsh Antarctic environment. The best ...

  17. Spatial modelling of wetness for the Antarctic Dry Valleys

    Directory of Open Access Journals (Sweden)

    Glen Stichbury

    2011-03-01

    Full Text Available This paper describes a method used to model relative wetness for part of the Antarctic Dry Valleys using Geographic Information Systems (GIS and remote sensing. The model produces a relative index of liquid water availability using variables that influence the volume and distribution of water. Remote sensing using Moderate Resolution Imaging Spectroradiometer (MODIS images collected over four years is used to calculate an average index of snow cover and this is combined with other water sources such as glaciers and lakes. This water source model is then used to weight a hydrological flow accumulation model that uses slope derived from Light Detection and Ranging (LIDAR elevation data. The resulting wetness index is validated using three-dimensional visualization and a comparison with a high-resolution Advanced Land Observing Satellite image that shows drainage channels. This research demonstrates that it is possible to produce a wetness model of Antarctica using data that are becoming widely available.

  18. The stationary distribution and ergodicity of a stochastic phytoplankton allelopathy model under regime switching

    Science.gov (United States)

    Zhao, Yu; Yuan, Sanling; Zhang, Tonghua

    2016-08-01

    The effect of toxin-producing phytoplankton and environmental stochasticity are interesting problems in marine plankton ecology. In this paper, we develop and analyze a stochastic phytoplankton allelopathy model, which takes both white and colored noises into account. We first prove the existence of the global positive solution of the model. And then by using the stochastic Lyapunov functions, we investigate the positive recurrence and ergodic property of the model, which implies the existence of a stationary distribution of the solution. Moreover, we obtain the mean and variance of the stationary distribution. Our results show that both the two kinds of environmental noises and toxic substances have great impacts on the evolution of the phytoplankton populations. Finally, numerical simulations are carried out to illustrate our theoretical results.

  19. Antarctic ice volume for the last 740 ka calculated with a simple ice sheet model

    NARCIS (Netherlands)

    Oerlemans, J.

    2005-01-01

    Fluctuations in the volume of the Antarctic ice sheet for the last 740 ka are calculated by forcing a simple ice sheet model with a sea-level history (from a composite deep sea δ18O record) and a temperature history (from the Dome C deuterium record). Antarctic ice volume reaches maximum values of a

  20. Improving dynamic phytoplankton reserve-utilization models with an indirect proxy for internal nitrogen.

    Science.gov (United States)

    Malerba, Martino E; Heimann, Kirsten; Connolly, Sean R

    2016-09-01

    Ecologists have often used indirect proxies to represent variables that are difficult or impossible to measure directly. In phytoplankton, the internal concentration of the most limiting nutrient in a cell determines its growth rate. However, directly measuring the concentration of nutrients within cells is inaccurate, expensive, destructive, and time-consuming, substantially impairing our ability to model growth rates in nutrient-limited phytoplankton populations. The red chlorophyll autofluorescence (hereafter "red fluorescence") signal emitted by a cell is highly correlated with nitrogen quota in nitrogen-limited phytoplankton species. The aim of this study was to evaluate the reliability of including flow cytometric red fluorescence as a proxy for internal nitrogen status to model phytoplankton growth rates. To this end, we used the classic Quota model and designed three approaches to calibrate its model parameters to data: where empirical observations on cell internal nitrogen quota were used to fit the model ("Nitrogen-Quota approach"), where quota dynamics were inferred only from changes in medium nutrient depletion and population density ("Virtual-Quota approach"), or where red fluorescence emission of a cell was used as an indirect proxy for its internal nitrogen quota ("Fluorescence-Quota approach"). Two separate analyses were carried out. In the first analysis, stochastic model simulations were parameterized from published empirical relationships and used to generate dynamics of phytoplankton communities reared under nitrogen-limited conditions. Quota models were fitted to the dynamics of each simulated species with the three different approaches and the performance of each model was compared. In the second analysis, we fit Quota models to laboratory time-series and we calculate the ability of each calibration approach to describe the observed trajectories of internal nitrogen quota in the culture. Results from both analyses concluded that the

  1. The role of organic ligands in iron cycling and primary productivity in the Antarctic Peninsula: A modeling study

    Science.gov (United States)

    Jiang, Mingshun; Barbeau, Katherine A.; Selph, Karen E.; Measures, Christopher I.; Buck, Kristen N.; Azam, Farooq; Greg Mitchell, B.; Zhou, Meng

    2013-06-01

    Iron (Fe) is the limiting nutrient for primary productivity in the Southern Ocean, with much of the dissolved iron (dFe) bound to organic ligands or colloids. A Fe model for the Southern Ocean (SOFe) is developed to understand the role of bacteria and organic ligands in controlling Fe cycling and productivity. The model resolves the classical food web and microbial loop, including three types of nutrients (N, Si, Fe) and two types of Fe ligands. Simulations of the zero-dimensional (0-D) model are calibrated with detailed results of shipboard grow-out incubation experiments conducted with Antarctic Peninsula phytoplankton communities during winter 2006 to provide the best estimate of key biological parameters. Then a one-dimensional (1-D) model is developed by coupling the biological model with the Regional Oceanic Modeling System (ROMS) for a site on the Antarctic Peninsula shelf, and the model parameters are further calibrated with data collected from two surveys (summer 2004 and winter 2006) in the area. The results of the numerical simulations agree reasonably well with observations. An analysis of the 1-D model results suggests that bacteria and organic ligands may play an important role in Fe cycling, which can be categorized into a relatively fast mode within the euphotic zone dominated by photo-reactions (summer d Fe residence time about 600 days) and complexation and a slow mode below with most of the dFe biologically complexed (summer dFe residence time >10 years). The dFe removal from the euphotic zone is dominated by colloidal formation and further aggregations with additional contribution from biological uptake, and an increase of organic ligands would reduce Fe export. The decrease of Fe removal rate over depth is due to the continuous dissolution and remineralization of particulate Fe. A number of sensitivity experiments are carried out for both 0-D and 1-D models to understand the importance of photo-reactive processes in primary productivity

  2. Phytoplankton Bloom Phenology near Palmer Station Antarctica

    Science.gov (United States)

    Crews, L.; Doney, S. C.; Kavanaugh, M.; Ducklow, H. W.; Schofield, O.; Glover, D. M.

    2015-12-01

    West Antarctic Peninsula (WAP) phytoplankton bloom phenology is coupled to growing season water column stratification precipitated by seasonal warming and the melting of winter sea-ice. Previous studies document declining bloom magnitude over decadal timescales in conjunction with decreasing sea-ice extent and duration in the Northern WAP, but less work has been to done explain the observed inter-annual variability in this region. Here we use a high-resolution in situ time series collected by the Palmer Station Antarctica Long Term Ecological Research program and satellite ocean color imagery to investigate the underlying mechanisms controlling phytoplankton bloom timing and magnitude near Palmer Station. We pair chlorophyll and CTD measurements collected twice per week during the austral summer, 1992—2003, with satellite ocean color and ice fractional cover data to examine bloom development and within-season trends in mixed layer depth. Initial results suggest a possible shift over time with spring/summer blooms occurring earlier in the growing season reflecting earlier sea-ice free conditions. Net phytoplankton accumulation rates are also computed and compared against growth estimates. Our results can be used to develop and validate models of coastal Antarctic primary production that better represent inter-annual primary production variability.

  3. MODELING INTERACTIONS BETWEEN PHYTOPLANKTON AND BACTERIA UNDER NUTRIENT-REGENERATING CONDITIONS

    NARCIS (Netherlands)

    IETSWAART, T; FLYNN, KJ

    1995-01-01

    The interactions of phytoplankton and bacteria in a nitrogen-limited steady-state system with an organic nitrogen compound or ammonium as the sole nitrogen source were modelled. The effects of various algal excretion rates and two different mathematical representations of excretion were examined. Th

  4. Impact of river discharge on phytoplankton bloom dynamics in eutrophic estuaries: A model study

    NARCIS (Netherlands)

    Liu, B.; de Swart, H.E.

    2015-01-01

    Field observations in estuaries reveal that phytoplankton blooms are strongly affected by advection processes related to river flow. To gain quantitative insight into this dependence, experiments were performed with a new idealised model that couples physical and biological processes. Advection of p

  5. Spatial distribution of the iron supply to phytoplankton in the Southern Ocean: a model study

    Directory of Open Access Journals (Sweden)

    C. Lancelot

    2009-05-01

    Full Text Available An upgraded version of the biogeochemical model SWAMCO is coupled to the ocean-sea-ice model NEMO-LIM to explore processes governing the spatial distribution of the iron supply to phytoplankton in the Southern Ocean. The 3-D NEMO-LIM-SWAMCO model is implemented in the ocean domain south of latitude 30° S and runs are performed over September 1989–December 2000. Model scenarios include potential iron sources (atmospheric deposition, iceberg calving and continental sediments as well as iron storage within sea ice, all formulated based on a literature review. When all these processes are included, the simulated iron profiles and phytoplankton bloom distributions show satisfactory agreement with observations. Analysis of simulations points to the key role played by continental sediments as a primary source for iron. Iceberg calving and melting contribute by up to 25% of Chl a simulated in areas under influence of icebergs while atmospheric deposition has little effect at high latitudes. Activating sea ice-ocean iron exchanges redistribute iron geographically. Stored in the ice during winter formation, iron is then transported due to ice motion and is released and made available to phytoplankton during summer melt, in the vicinity of the marginal ice zones. Transient iron storage and transport associated with sea ice dynamics stimulate summer phytoplankton blooming (up to 3 mg Chl a m−3 in the Weddell Sea and off East Antarctica but not in the Ross, Bellingshausen and Amundsen Seas. This contrasted feature results from the simulated variable content of iron in sea ice and release of melting ice showing higher ice-ocean iron fluxes in the continental shelves of the Weddell and Ross Seas than in the Eastern Weddell Sea and the Bellingshausen-Amundsen Seas. This study confirms that iron sources and transport in the Southern Ocean likely provide important mechanisms in the geographical development of phytoplankton blooms and

  6. Modeling Antarctic Subglacial Lake Filling and Drainage Cycles

    Science.gov (United States)

    Dow, Christine F.; Werder, Mauro A.; Nowicki, Sophie; Walker, Ryan T.

    2016-01-01

    The growth and drainage of active subglacial lakes in Antarctica has previously been inferred from analysis of ice surface altimetry data. We use a subglacial hydrology model applied to a synthetic Antarctic ice stream to examine internal controls on the filling and drainage of subglacial lakes. Our model outputs suggest that the highly constricted subglacial environment of our idealized ice stream, combined with relatively high rates of water flow funneled from a large catchment, can combine to create a system exhibiting slow-moving pressure waves. Over a period of years, the accumulation of water in the ice stream onset region results in a buildup of pressure creating temporary channels, which then evacuate the excess water. This increased flux of water beneath the ice stream drives lake growth. As the water body builds up, it steepens the hydraulic gradient out of the overdeepened lake basin and allows greater flux. Eventually this flux is large enough to melt channels that cause the lake to drain. Lake drainage also depends on the internal hydrological development in the wider system and therefore does not directly correspond to a particular water volume or depth. This creates a highly temporally and spatially variable system, which is of interest for assessing the importance of subglacial lakes in ice stream hydrology and dynamics.

  7. PhytoSFDM version 1.0.0: Phytoplankton Size and Functional Diversity Model

    OpenAIRE

    Acevedo-Trejos, Esteban; Brandt, Gunnar; Smith, S. Lan; Merico, Agostino

    2016-01-01

    Biodiversity is one of the key mechanisms that facilitate the adaptive response of planktonic communities to a fluctuating environment. How to allow for such a flexible response in marine ecosystem models is, however, not entirely clear. One particular way is to resolve the natural complexity of phytoplankton communities by explicitly incorporating a large number of species or plankton functional types. Alternatively, models of aggregate community properties focus on macroecological quantitie...

  8. Global response to solar radiation absorbed by phytoplankton in a coupled climate model

    International Nuclear Information System (INIS)

    The global climate response to solar radiation absorbed by phytoplankton is investigated by performing multi-century simulations with a coupled ocean-atmosphere-biogeochemistry model. The absorption of solar radiation by phytoplankton increases radiative heating in the near-surface ocean and raises sea surface temperature (SST) by overall ∼0.5 C. The resulting increase in evaporation enhances specific atmospheric humidity by 2-5%, thereby increasing the Earth's greenhouse effect and the atmospheric temperatures. The Hadley Cell exhibits a weakening and poleward expansion, therefore reducing cloudiness at subtropical-middle latitudes and increasing it at tropical latitudes except near the Equator. Higher SST at polar latitudes reduces sea ice cover and albedo, thereby increasing the high-latitude ocean absorption of solar radiation. Changes in the atmospheric baroclinicity cause a poleward intensification of mid-latitude westerly winds in both hemispheres. As a result, the North Atlantic Ocean meridional overturning circulation extends more northward, and the equatorward Ekman transport is enhanced in the Southern Ocean. The combination of local and dynamical processes decreases upper-ocean heat content in the Tropics and in the subpolar Southern Ocean, and increases it at middle latitudes. This study highlights the relevance of coupled ocean-atmosphere processes in the global climate response to phytoplankton solar absorption. Given that simulated impacts of phytoplankton on physical climate are within the range of natural climate variability, this study suggests the importance of phytoplankton as an internal constituent of the Earth's climate and its potential role in participating in its long-term climate adjustments. (orig.)

  9. Global response to solar radiation absorbed by phytoplankton in a coupled climate model

    Energy Technology Data Exchange (ETDEWEB)

    Patara, Lavinia [Centro Euro-Mediterraneo per i Cambiamenti Climatici (CMCC), Bologna (Italy); Helmholtz Centre for Ocean Research Kiel (GEOMAR), Kiel (Germany); Vichi, Marcello; Masina, Simona [Centro Euro-Mediterraneo per i Cambiamenti Climatici (CMCC), Bologna (Italy); Istituto Nazionale di Geofisica e Vulcanologia (INGV), Centro Euro-Mediterraneo per i Cambiamenti Climatici (CMCC), Bologna (Italy); Fogli, Pier Giuseppe [Centro Euro-Mediterraneo per i Cambiamenti Climatici (CMCC), Bologna (Italy); Manzini, Elisa [Centro Euro-Mediterraneo per i Cambiamenti Climatici (CMCC), Bologna (Italy); Max-Planck-Institut fuer Meteorologie, Hamburg (Germany)

    2012-10-15

    The global climate response to solar radiation absorbed by phytoplankton is investigated by performing multi-century simulations with a coupled ocean-atmosphere-biogeochemistry model. The absorption of solar radiation by phytoplankton increases radiative heating in the near-surface ocean and raises sea surface temperature (SST) by overall {approx}0.5 C. The resulting increase in evaporation enhances specific atmospheric humidity by 2-5%, thereby increasing the Earth's greenhouse effect and the atmospheric temperatures. The Hadley Cell exhibits a weakening and poleward expansion, therefore reducing cloudiness at subtropical-middle latitudes and increasing it at tropical latitudes except near the Equator. Higher SST at polar latitudes reduces sea ice cover and albedo, thereby increasing the high-latitude ocean absorption of solar radiation. Changes in the atmospheric baroclinicity cause a poleward intensification of mid-latitude westerly winds in both hemispheres. As a result, the North Atlantic Ocean meridional overturning circulation extends more northward, and the equatorward Ekman transport is enhanced in the Southern Ocean. The combination of local and dynamical processes decreases upper-ocean heat content in the Tropics and in the subpolar Southern Ocean, and increases it at middle latitudes. This study highlights the relevance of coupled ocean-atmosphere processes in the global climate response to phytoplankton solar absorption. Given that simulated impacts of phytoplankton on physical climate are within the range of natural climate variability, this study suggests the importance of phytoplankton as an internal constituent of the Earth's climate and its potential role in participating in its long-term climate adjustments. (orig.)

  10. Viable Bacteria in Antarctic Soils and - Two Models for Extraterrestrial Search of Life

    Science.gov (United States)

    Soina, Vera; Vorobyova, Elena; Lysak, Ludmila; Mergelov, Nikita

    Antarctic soils and permafrost are the most convenient models for search life preservation in extraterrestrial cryogenic environment. Study of life activity and preservation of prokaryotes in such extreme environment allow assuming, that those habitats must be viewed as two models for astrobiology extrapolations. Antarctic permafrost due to long term freezing can be regarded as the most stable environment for life preservation and expanding of potential physiological cell activity due to stabilization of cell structures and biomolecules. Antarctic soils seem to be not less attractive as a model for study of life on the surface of Antarctic rocks, but in contrast to permafrost are characterized by less stable external factors. Presumably, it is due to changing cycles of freezing and thawing and high doses of UV radiation, that make such biotopes more extreme for microbial survival. A combination of culture- depended and - independent techniques, including SEM and TEM methods were used to characterize bacteria community in earlier not investigated Antarctic soils in the oases of Larsemann Hills (East Antarctic Coast). Several important characteristics of Antarctic soil and permafrost bacteria as models for possible signs of life in extraterrestrial habitats are discussed (cytomorphological and physiological characteristics of bacteria both in situ, and cells isolated from permafrost and exposed to various external stress factors). Our data indicate that significant discrepancy between indexes of total and viable number of cells and irregularity of such indexes in horizons of developing soils and permafrost sediments can be explained by specification of physical and chemical processes in those habitats. Also, in Antarctic and extraterrestrial investigations is important to take into account the leading role of microbial biofilms, where microorganisms are intimately associated with each other and mineral particles through binding and inclusion within exopolymer matrix

  11. Model dependences of the deactivation of phytoplankton pigment excitation energy on environmental conditions in the sea

    Directory of Open Access Journals (Sweden)

    Mirosława Ostrowska

    2012-11-01

    Full Text Available A semi-empirical, physical models have been derived of the quantum yield ofthe deactivation processes (fluorescence, photosynthesis and heat productionof excited states in phytoplankton pigment molecules. Besides some alreadyknown models (photosynthesis and fluorescence, this novel approachincorporates the dependence of the dissipation yield of the excitation energyin phytoplankton pigment molecules on heat. The quantitative dependences ofthe quantum yields of these three processes on three fundamental parameters ofthe marine environment are defined: the chlorophyll concentration in the surface water layer Ca(0 (the basin trophicity,the irradiance PAR(z and the temperature temp(z at the study site.The model is complemented with two other relevant models describing thequantum yield of photosynthesis and of natural Sun-Induced Chlorophyll a Fluorescence (SICF in the sea, derived earlier by the author or with herparticipation on the basis of statistical analyses of a vast amount ofempirical material. The model described in the present paper enables theestimation of the quantum yields of phytoplankton pigment heat production forany region and season, in waters of any trophicity at different depths fromthe surface to depths of ca 60 m. The model can therefore be used to estimatethe yields of these deactivation processes in more than half the thickness ofthe euphotic zone in oligotrophic waters and in the whole thickness (anddeeper of this zone in mesotrophic and eutrophic waters. In particular theserelationships may be useful for a component analysis of the budget of lightenergy absorbed by phytoplankton pigments, namely, its utilization influorescence, photochemical quenching and nonphotochemical radiationlessdissipation - i.e. direct heat production.

  12. Model decay in the Australia-Antarctic basin

    Energy Technology Data Exchange (ETDEWEB)

    Weijer, Wilbert [Los Alamos National Laboratory; Gille, Sarah T [UCSD; Vivier, Frederic [LOCEAN-IPSL

    2008-01-01

    The barotropic intraseasonal variability in the Australia-Antarctic Basin (AAB) is studied in terms of the excitation and decay of topographically-trapped barotropic modes. The main objective is to reconcile two widely differing estimates of the decay rate of SSH anomalies in the AAB that are assumed to be related to barotropic modes. First, an Empirical Orthogonal Function (EOF) analysis is applied to almost 15 years of altimeter data. The analysis suggests that several modes are involved in the variability of the AAB, each related to distinct areas with (almost) closed contours of potential vorticity. Second, the dominant normal modes of the AAB are determined in a barotropic shallow-water (SW) model. These stationary modes are confined by the closed contours of potential vorticity that surround the eastern AAB, and the crest of the Southeast Indian Ridge. For reasonable values of horizontal eddy viscosity and bottom friction, their decay time scale is of the order of several weeks. Third, the SW model is forced with realistic winds and integrated for several years. Projection of the modal velocity patterns onto the output fields shows that the barotropic modes are indeed excited in the model, and that they decay slowly on the frictional O(3 weeks) time scale. However, the SSH anomalies in the modal areas display rapid O(4 days) decay. Additional analysis shows that this rapid decay reflects the adjustment of unbalanced flow components through the emission of Rossby waves. Resonant excitation of the dominant free modes accounts for about 20% of the SSH variability in the forced model run. Other mechanisms are suggested to explain the region of high SSH variability in the AAB.

  13. Antarctic ecosystems as models for extraterrestrial surface habitats

    Science.gov (United States)

    Wynn-Williams, D. D.; Edwards, H. G. M.

    2000-09-01

    Surface habitats in Antarctic deserts are near the limits of life on Earth and resemble those hypothesized for early Mars. Cyanobacteria dominate the transient riverbeds, stromatolitic sediments in ice-covered lakes, and endolithic communities in translucent rock. There is still no direct evidence of photosynthetic life on early Mars, but cyanobacteria are amongst the earliest microbes detectable in the fossil record for analogous habitats on Earth. Key biomolecules persist in Antarctic microbial habitats, even after extinction by excessive low temperatures, desiccation and UV-B stress within the Ozone Hole. Pigments (or their fossil residues), such as chlorophyll and the UV-protectants scytonemin, carotene and quinones, are good biomarkers. To show not only their presence but also their micro-spatial distribution in situ, we describe the use of FT-Raman spectroscopy with 1064 nm excitation to avoid autofluorescence from the pigments. We report not only the diversity of biomolecules that we have diagnosed from their unique Raman spectra of Antarctic cyanobacterial communities, but also their functional stratification in endolithic communities. Our analyses of Antarctic habitats show the potential of this remote, non-intrusive technique to probe for buried biomolecules on future Mars missions and in Antarctic Lake Vostok, >4 km beneath the Central Ice Sheet, with implications for the putative analogous sub-ice ocean on Europa.

  14. Modeling Antarctic subglacial lake filling and drainage cycles

    Directory of Open Access Journals (Sweden)

    C. F. Dow

    2015-11-01

    Full Text Available The growth and drainage of active subglacial lakes in Antarctica has previously been inferred from analysis of ice surface altimetry data. We use a subglacial hydrology model applied to a synthetic Antarctic ice stream to determine internal controls on the filling and drainage of subglacial lakes and their impact on ice stream dynamics. Our model outputs suggest that the highly constricted subglacial environment of the ice stream, combined with relatively high rates of water flow funneled from large catchments, can combine to create a system exhibiting slow-moving pressure waves. Over a period of years, the accumulation of water in the ice stream onset region results in a buildup of pressure creating temporary channels, which then evacuate the excess water. This increased flux of water through the ice stream drives lake growth. As the water body builds up, it too steepens the hydraulic gradient and allows greater flux out of the overdeepened lake basin. Eventually this flux is large enough to create channels that cause the lake to drain. Due to the presence of the channels, the drainage of the lake causes high water pressures around 50 km downstream of the lake rather than immediately in the vicinity of the overdeepening. Following lake drainage, channels again shut down. Lake drainage depends on the internal hydrological development in the wider system and therefore does not directly correspond to a particular water volume or depth. This creates a highly temporally and spatially variable system, which is of interest for assessing the importance of subglacial lakes in ice stream hydrology and dynamics.

  15. Model studies of the effects of global warming and Antarctic sea ice changes on Antarctic and global climates

    International Nuclear Information System (INIS)

    The authors discuss the results obtained in three experiments by changing the global ocean temperatures and the concentration and distribution of Antarctic sea ice in a General Circulation Model of July climate, with a view to determining the local and global impacts of Antarctic sea ice variations alone, as distinct with those coupled with global scale temperature changes which may be associated with global warming. In all cases there were significant changes in the upward flux of sensible heat over the sea ice zone associated with the reductions of sea ice. The response of weaker westerlies between 40 and 65 degree S was common to all three experiments. Their analyses suggest that a significant proportion of this is a response to the change in sea ice concentration alone. (Not surprisingly, further north of this region most of the changes induced in the wind structure in the global forcing experiment can be seen as due unambiguously to the differential changes in ocean temperatures.). This weakening of the westerlies means there is less mechanical forcing of the ocean in this region. From this they suggest that when consideration is given to the possible impact of feedbacks not considered in these experiments, sea ice changes alone, and particularly those in the Southern Hemisphere, have the potential to induce changes on a hemispheric scale

  16. Firn compaction modelling of the Antarctic ice sheet

    Science.gov (United States)

    Kallenberg, Bianca; Tregoning, Paul

    2013-04-01

    Satellite altimetry missions detect elevation changes in ice sheets that are not only related to variations in ice mass balance, but also to snow densification. The compaction of snow induces a change in thickness but not in mass and therefore has to be removed from the altimetry measurements when estimating mass loss from height changes. The densification of snow is time dependent and varies with temperature, accumulation rate and depth. Different types of densification processes occur in Antarctica due to the climatic differences from warm and moist coastal areas to a cold and dry desert in the Antarctic interior. The intermediate product between snow and ice is called firn and the transition from snow to ice is a slow process that can take up to millennia in some areas. During the compression snow grains undergo different stages with a density change from around 300 kg/m3 for fresh snow to around 900 kg/m3 for glacier ice. The change in density with temperature and depth is not well known and can only be compared with some snow pits that have been taken at a few locations in Antarctica, thus the density profile is of great importance. The lack of data complicates the generation of an accurate firn compaction model and so far only a few models have been established about expected firn densification processes in Antarctica. We present a time-dependent firn compaction model for Antarctica based on the standard heat-transfer equation after Paterson (1994)* for the temperature profile, and the concept of firn compaction after Zwally & Li (2002)*. By incorporating a time-dependent accumulation rate, our numerical multilayer model considers not only existing snow layers but also freshly deposited accumulation at the surface as a new introduced layer. The initial density profile as been obtained by spinning up the model until the entire firn layer is refreshed. We compare our results with previous firn compaction models and available in-situ measurements of snow pits

  17. A model study on carbon cycle and phytoplankton dynamical processes in the Bohai Sea

    Institute of Scientific and Technical Information of China (English)

    魏皓; 赵亮; 冯士筰

    2003-01-01

    The carbon cycle of lower trophic level in the Bohai Sea is studied with a three-dimension-al biological and physical coupled model. The influences of the processes (including horizontal advection,river nutrient load, active transport etc. ) on the phytoplankton biomass and its evolution are estimated.The Bohai Sea is a weak sink of the CO2 in the atmosphere. During the cycle, 13.7% of the gross pro-duction of the phytoplankton enter the higher trophic level and 76.8 % of it are consumed by the respira-tion itself. The nutrient reproduction comes mainly from the internal biogeochemical loop and the rem-ineralization is an important mechanism of the nutrient transfer from organic form to inorganic. Horizon-tal advection decreases the total biomass and the eutrophication in some sea areas. Change in the nutrientload of a river can only adjust the local system near its estuary. Controlling the input of the nutrient,which limits the alga growth, can be very useful in lessening the phytoplankton biomass.

  18. Modelling climate change, land-use change and phosphorus reduction impacts on phytoplankton in the River Thames (UK)

    Science.gov (United States)

    Bussi, Gianbattista; Whitehead, Paul; Dadson, Simon

    2016-04-01

    In this study, we assess the impact of changes in precipitation and temperature on the phytoplankton concentration of the River Thames (UK) by means of a physically-based model. A scenario-neutral approach was employed to evaluate the effects of climate variability on flow, phosphorus concentration and phytoplankton concentration. In particular, the impact of uniform changes in precipitation and temperature on five groups of phytoplankton (diatoms and large chlorophytes, other chlorophytes, picoalgae, Microcystis-like cyanobacteria and other cyanobacteria) was assessed under three different land-use/land-management scenarios (1 - current land use and phosphorus reduction practices; 2 - expansion of agricultural land and current phosphorus reduction practices; 3 - expansion of agricultural land and optimal phosphorus reduction practices). The model results were assessed within the framework of future climate projections, using the UK Climate Projections 09 (UKCP09) for the 2030s. The results of the model demonstrate that an increase in average phytoplankton concentration due to climate change is highly likely to occur, and its magnitude varies depending on the river reach. Cyanobacteria show significant increases under future climate change and land-use change. An expansion of intensive agriculture accentuates the growth in phytoplankton, especially in the upper reaches of the River Thames. However, an optimal phosphorus removal mitigation strategy, which combines reduction of fertiliser application and phosphorus removal from wastewater, can help to reduce this increase in phytoplankton concentration, and in some cases, compensate for the effect of rising temperature.

  19. Simulation of phytoplankton biomass in Quanzhou Bay using a back propagation network model and sensitivity analysis for environmental variables

    Institute of Scientific and Technical Information of China (English)

    ZHENG Wei; SHI Honghua; SONG Xikun; HUANG Dongren; HU Long

    2012-01-01

    Prediction and sensitivity models,to elucidate the response of phytoplankton biomass to environmental factors in Quanzhou Bay,Fujian,China,were developed using a back propagation(BP)network.The environmental indicators of coastal phytoplankton biomass were determined and monitoring data for the bay from 2008 was used to train,test and build a three-layer BP artificial neural network with multi-input and single-output.Ten water quality parameters were used to forecast phytoplankton biomass (measured as chlorophyll-a concentration).Correlation coefficient between biomass values predicted by the model and those observed was 0.964,whilst the average relative error of the network was-3.46% and average absolute error was 10.53%.The model thus has high level of accuracy and is suitable for analysis of the influence of aquatic environmental factors on phytoplankton biomass.A global sensitivity analysis was performed to determine the influence of different environmental indicators on phytoplankton biomass.Indicators were classified according to the sensitivity of response and its risk degree.The results indicate that the parameters most relevant to phytoplankton biomass are estuary-related and include pH,sea surface temperature,sea surface salinity,chemical oxygen demand and ammonium.

  20. Critical conditions for phytoplankton blooms

    OpenAIRE

    Ebert, Ute; Arrayás, M.; Temme, Nico; Sommeijer, Ben; Huisman, J.

    2001-01-01

    We motivate and analyze a reaction-advection-diffusion model for the dynamics of a phytoplankton species. The reproductive rate of the phytoplankton is determined by the local light intensity. The light intensity decreases with depth due to absorption by water and phytoplankton. Phytoplankton is transported by turbulent diffusion in a water column of given depth. Furthermore, it might be sinking or buoyant depending on its specific density. Dimensional analysis allows the reduction of the ful...

  1. Prediction and setup of phytoplankton statistical model of Qiandaohu Lake

    Institute of Scientific and Technical Information of China (English)

    严力蛟; 全为民; 赵晓慧

    2004-01-01

    This research considers the mathematical relationship between concentration of Chla and seven environmental factors, i.e. Lake water temperature (T), Secci-depth (SD), pH, DO, CODMn, Total Nitrogen (TN), Total Phosphorus (TP).Stepwise linear regression of 1997 to 1999 monitoring data at each sampling point of Qiandaohu Lake yielded the multivariate regression models presented in this paper. The concentration of Chla as simulation for the year 2000 by the regression model was similar to the observed value. The suggested mathematical relationship could be used to predict changes in the lakewater environment at any point in time. The results showed that SD, TP and pH were the most significant factors affecting Chla concentration.

  2. Formulation, calibration and validation of the DAIS model (version 1), a simple Antarctic ice sheet model sensitive to variations of sea level and ocean subsurface temperature

    OpenAIRE

    Shaffer, G.

    2014-01-01

    The DCESS (Danish Center for Earth System Science) Antarctic Ice Sheet (DAIS) model is presented. Model hindcasts of Antarctic ice sheet (AIS) sea level equivalent are forced by reconstructed Antarctic temperatures, global mean sea level and high-latitude, ocean subsurface temperatures, the latter calculated using the DCESS model forced by reconstructed global mean atmospheric temperatures. The model is calibrated by comparing such hindcasts for different model configurations w...

  3. To what extent does the salinity flux influence phytoplankton blooms? - Baltic Sea modeling study

    Science.gov (United States)

    Cieszyńska, Agata; Stramska, Małgorzata

    2016-04-01

    This work is focused on numerical modeling of biological-physical interactions and their influence on phytoplankton production and vertical distribution of biomass and its variability in the surface waters of the Baltic Sea. The area of interest is an inland sea with water salinity much smaller than observed in the global ocean (about one fifth of the open ocean value). Vertical distribution of the salinity has a significant influence on water column density stratification, and therefore influences intensity of mixing and the depth of mixed layer. This, in turn, defines environmental conditions for phytoplankton growth. Vertical distribution of water salinity in the basin is controlled by processes such as evaporation/precipitation, freezing/melting of sea ice and runoff of freshwater from land. There are a lot of different phytoplankton species in the area of the Baltic Sea. Every single one has its own characteristics and is sensitive to distinct complex environmental conditions. Biological-physical interactions controlling these microorganisms' life cycles are multiplicitous and because of their complexity difficult to quantify. The best and probably only way to study presented issue is the usage of numerical modeling tool. The results presented here are based on 1D numerical simulations carried out with Princeton Ocean Model (POM, http://www.ccpo.odu.edu/POMWEB/) merged with the Ecological Regional Ecosystem Model (ERGOM, http://ergom.net/) developed for the Baltic Sea research by German scientists from the Leibniz Institute for Baltic Sea Research in Warnemünde. In model simulations surface salinity flux was determined from the difference between the precipitation and evaporation rate at the air-sea interface. Data for parameterization of atmospheric forcing were defined based on data sets from National Centers of Environmental Prediction (NCEP). We carried out systematic calculations using different values of surface fluxes encompassing the range of

  4. Antarctic ice volume and deep-sea temperature during the last 50 Myr: a model study

    NARCIS (Netherlands)

    Oerlemans, J.

    2004-01-01

    A simple quasi-analytical model is used to study the sensitivity of the Antarctic ice sheet to climate change. The model is axisymmetrical and has a profile that only depends on the ice-sheet radius. The climatic conditions are represented by three parameters: the altitude of the runoff line, the ac

  5. Ecological niche model to predict the potential distribution of phytoplankton in the Aguamilpa Dam, Nayarit. Mexico

    Directory of Open Access Journals (Sweden)

    Humberto Macias-Cuellar

    2010-12-01

    Full Text Available Phytoplankton species are an important basis of the food web for various systems such as pelagic, coastal and lake. Due to their photosynthetic capacity, this community is sensitive to changes in light availability, temperature, nutrient concentrations, herbivores consumption, parasitism and competition. Therefore, they show a high spatial and temporal variability related to environmental changes both natural and anthropogenic. However, as any taxonomic group, phytoplankton species have environmental thresholds, ecological niches that define their distribution. This study was located in Aguamilpa Dam, an artificial aquatic reservoir which started operations in 1994 for electric energy production. In this system the potential distribution of the phytoplankton was evaluated, where the highest species richness and restricted distribution areas were identified. Potential distribution models based on ecological niche definition were generated using ArcMap 9.2® with Maxent (Maximun Entropy Method. The development of distribution maps was carried out using Digital Elevation Models in cells of 100 m x 100 m (1 ha, based on nine physico-chemical and biological water parameters monitored in the reservoir. The highest species richness areas were found in the Huaynamota river tributary and at the station called La Confluencia, while the less abundance areas were found in the Santiago river tributary during warm and cold dry seasons with a great abundance of cyanophyta. During the rainfall season, the Huaynamota river tributary diversity areas were extended and the presence of some dominant species of cyanophyta were indentified. These species can be associated with trophic processes related to anthropogenic pollutants in the reservoir. This study illustrates the potential application of niche modeling approach in aquatic ecosystems.

  6. The Effects of Climate Variability on Phytoplankton Composition in the Equatorial Pacific Ocean using a Model and a Satellite-Derived Approach

    Science.gov (United States)

    Rousseaux, C. S.; Gregg, W. W.

    2012-01-01

    Compared the interannual variation in diatoms, cyanobacteria, coccolithophores and chlorophytes from the NASA Ocean Biogeochemical Model with those derived from satellite data (Hirata et al. 2011) between 1998 and 2006 in the Equatorial Pacific. Using NOBM, La Ni a events were characterized by an increase in diatoms (correlation with MEI, r=-0.81, Pclimate variability. However, satellite-derived phytoplankton groups were all negatively correlated with climate variability (r ranged from -0.39 for diatoms to -0.64 for coccolithophores, P<0.05). Spatially, the satellite-derived approach was closer to an independent in situ dataset for all phytoplankton groups except diatoms than NOBM. However, the different responses of phytoplankton to intense interannual events in the Equatorial Pacific raises questions about the representation of phytoplankton dynamics in models and algorithms: is a phytoplankton community shift as in the model or an across-the-board change in abundances of all phytoplankton as in the satellite-derived approach.

  7. A Model Study on Dynamical Processes of Phytoplankton in Laizhou Bay

    Institute of Scientific and Technical Information of China (English)

    YU Lanlan; YANG Bo; JIANG Wensheng; LI Keqiang

    2014-01-01

    A three-dimensional ecosystem model, using a PIC (Particle-In-Cell) method, is developed to reproduce the annual cycle and seasonal variation of nutrients and phytoplankton biomass in Laizhou Bay. Eight state variables, i.e., DIN (dissolved inorganic nitrogen), phosphate, DON (dissolved organic nitrogen), DOP (dissolved organic phosphorus), COD (chemical oxygen demand), chlorophyll-a (Chl-a), detritus and the zooplankton biomass, are included in the model. The model successfully reproduces the ob-served temporal and spatial variations of nutrients and Chl-a biomass distributions in the bay. The nutrient concentrations are at high level in winter and at low level in summer. Double-peak structure of the phytoplankton (PPT) biomass exists in Laizhou Bay, corre-sponding to a spring and an autumn bloom respectively. Several numerical experiments are carried out to examine the nutrient limita-tion, and the importance of the discharges of the Yellow River and Xiaoqinghe River. Both DIN limitation and phosphate limitation exist in some areas of the bay, with the former being more significant than the latter. The Yellow River and Xiaoqinghe River are the main pollution sources of nutrients in Laizhou Bay. During the flood season, the algal growth is inhibited in the bay with the Yellow River discharges being excluded in the experiment, while in spring, the algal growth is enhanced with the Xiaoqinghe River ex-cluded.

  8. Simulation of phytoplankton distribution and variation in the Bering-Chukchi Sea using a 3-D physical-biological model

    Science.gov (United States)

    Hu, Haoguo; Wang, Jia; Liu, Hui; Goes, Joaquim

    2016-06-01

    A three-dimensional physical-biological model has been used to simulate seasonal phytoplankton variations in the Bering and Chukchi Seas with a focus on understanding the physical and biogeochemical mechanisms involved in the formation of the Bering Sea Green Belt (GB) and the Subsurface Chlorophyll Maxima (SCM). Model results suggest that the horizontal distribution of the GB is controlled by a combination of light, temperature, and nutrients. Model results indicated that the SCM, frequently seen below the thermocline, exists because of a rich supply of nutrients and sufficient light. The seasonal onset of phytoplankton blooms is controlled by different factors at different locations in the Bering-Chukchi Sea. In the off-shelf central region of the Bering Sea, phytoplankton blooms are regulated by available light. On the Bering Sea shelf, sea ice through its influence on light and temperature plays a key role in the formation of blooms, whereas in the Chukchi Sea, bloom formation is largely controlled by ambient seawater temperatures. A numerical experiment conducted as part of this study revealed that plankton sinking is important for simulating the vertical distribution of phytoplankton and the seasonal formation of the SCM. An additional numerical experiment revealed that sea ice algae account for 14.3-36.9% of total phytoplankton production during the melting season, and it cannot be ignored when evaluating primary productivity in the Arctic Ocean.

  9. Bioavailability of organically bound Fe to model phytoplankton of the Southern Ocean

    Directory of Open Access Journals (Sweden)

    C. S. Hassler

    2009-10-01

    Full Text Available Iron (Fe is known to be mostly bound to organic ligands and to limit primary productivity in the Southern Ocean. It is thus important to investigate the bioavailability of organically bound Fe. In this study, we used four phytoplankton species of the Southern Ocean (Phaeocystis sp., Chaetoceros sp., Fragilariopsis kerguelensis and Thalassiosira antarctica Comber to measure the influence of various organic ligands on Fe solubility and bioavailability. Short-term uptake Fe:C ratios were inversely related to the surface area to volume ratios of the phytoplankton. The ratio of extracellular to intracellular Fe is used to discuss the relative importance of diffusive supply and uptake to control Fe bioavailability. The effect of excess organic ligands on Fe bioavailability cannot be solely explained by their effect on Fe solubility. For most strains studied, the bioavailability of Fe can be enhanced relative to inorganic Fe in the presence of porphyrin, catecholate siderophore and saccharides whereas it was decreased in presence of hydroxamate siderophore and organic amine. For Thalassiosira, iron bioavailability was not affected by the presence of porphyrin, catecholate siderophore and saccharides. The enhancement of Fe bioavailability in presence of saccharides is presented as the result from both the formation of bioavailable (or chemically labile organic form of Fe and the stabilisation of Fe within the dissolved phase. Given the ubiquitous presence of saccharides in the ocean, these compounds might represent an important factor to control the basal level of soluble and bioavailable Fe. Results show that the use of model phytoplankton is promising to improve mechanistic understanding of Fe bioavailability and primary productivity in HNLC regions of the ocean.

  10. Response of the Antarctic Ice Sheet to a climatic warming: a model study

    NARCIS (Netherlands)

    Oerlemans, J.

    1982-01-01

    It is generally believed that the increasing C02 content of the atmosphere will lead to a substantial climatic warming in the polar regions. In this study the effect of consequent changes in the ice accumulation rate over the Antarctic Ice Sheet is investigated by means of a numerical ice flow model

  11. Antarctic ice sheet GLIMMER model test and its simplified model on 2-dimensional ice flow

    Institute of Scientific and Technical Information of China (English)

    Xueyuan Tang; Zhanhai Zhang; Bo Sun; Yuansheng Li; Na Li; Bangbing Wang; Xiangpei Zhang

    2008-01-01

    The 3-dimensional finite difference thermodynamic coupled model on Antarctic ice sheet, GLIMMER model, is described. An ide-alized ice sheet numerical test was conducted under the EISMINT-I benchmark, and the characteristic curves of ice sheets under steady state were obtained. Based on this, this model was simplified from a 3-dimensional one to 2-dimensional one. Improvement of the dif-ference method and coordinate system was proposed. Evolution of the 2-dimensional ice flow was simulated under coupled temperature field conditions. The results showed that the characteristic curves deriving from the conservation of the mass, momentum and energy agree with the results of ice sheet profile simulated with GLIMMER model and with the theoretical results. The application prospect of the simplified 2-dimensional ice flow model to simulate the relation of age-depth-accumulation in Dome A region was discussed.

  12. Climate Model Dependency and Understanding the Antarctic Ice Sheet during the Warm Late Pliocene

    Science.gov (United States)

    Dolan, Aisling; de Boer, Bas; Bernales, Jorge; Hunter, Stephen; Haywood, Alan

    2016-04-01

    In the context of future climate change, understanding the nature and behaviour of ice sheets during warm intervals of Earth history is fundamentally important. A warm period in the Late Pliocene (3.264 to 3.025 million years before present) can serve as a potential analogue for projected future climates. Although Pliocene ice locations and extents are still poorly constrained, a significant contribution to sea-level rise should be expected from both the Greenland ice sheet and the West and East Antarctic ice sheets based on palaeo sea-level reconstructions and geological evidence. Following a five year international project PLISMIP (Pliocene Ice Sheet Modeling Intercomparison Project) we present the final set of results which quantify uncertainty in climate model-based predictions of the Antarctic ice sheet. In this study we use an ensemble of climate model forcings within a multi-ice sheet model framework to assess the climate (model) dependency of large scale features of the Antarctic ice sheet. Seven coupled atmosphere-ocean climate models are used to derive surface temperature, precipitation and oceanic forcing that drive three ice sheet models (over the grounded and floating domain). Similar to results presented over Greenland, we show that the reconstruction of the Antarctic ice sheet is sensitive to which climate model is used to provide the forcing field. Key areas of uncertainty include West Antarctica, the large subglacial basins of East Antarctica and the overall thickness of the continental interior of East Antarctica. We relate the results back to geological proxy data, such as those relating to exposure rates which provide information on potential ice sheet thickness. Finally we discuss as to whether the choice of modelling framework (i.e. climate model and ice sheet model used) or the choice of boundary conditions causes the greatest uncertainty in ice sheet reconstructions of the warm Pliocene.

  13. Emergence and annihilation of localized structures in a phytoplankton-nutrient model

    CERN Document Server

    Zagaris, Antonios

    2010-01-01

    Co-limitation of marine phytoplankton by light and nutrient leads to complex dynamic behavior and a wide array of coherent patterns. The building blocks of this array can be considered to be deep chlorophyll maxima, or DCMs, which are structures localized in the vertical direction. From an ecological point of view, DCMs are evocative of a balance between the inflow of light from the water surface and of nutrients from the sediment. From a (linear) bifurcational point of view, they appear through a transcritical bifurcation in which the trivial, no-plankton steady state is destabilized. This article is devoted to the analytic investigation of the weakly nonlinear dynamics of these DCM patterns, and it has two overarching themes. The first of these concerns the fate of the destabilizing stationary DCM mode beyond the linear regime. Exploiting the natural singularly perturbed nature of the model, we derive an explicit reduced model of asymptotically high dimension which fully captures these dynamics. Our subsequ...

  14. A one-dimensional heat transfer model of the Antarctic Ice Sheet and modeling of snow temperatures at Dome A, the summit of Antarctic Plateau

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A vertical one-dimensional numerical model for heat transferring within the near-surface snow layer of the Antarctic Ice Sheet was developed based on simplified parameterizations of associated physical processes for the atmosphere, radiation, and snow/ice systems. Using the meteorological data of an automatic weather station (AWS) at Dome A (80°22′S, 70°22′E), we applied the model to simulate the seasonal temperature variation within a depth of 20 m. Comparison of modeled results with observed snow temperatures at 4 measurement depths (0.1, 1, 3, 10 m) shows good agreement and consistent seasonal variations. The model results reveal the vertical temperature structure within the near-surface snow layer and its seasonal variance with more details than those by limited measurements. Analyses on the model outputs of the surface energy fluxes show that: 1) the surface energy balance at Dome A is characterized by the compensation between negative net radiation and the positive sensible fluxes, and 2) the sensible heat is on average transported from the atmosphere to the snow, and has an evident increase in spring. The results are considered well representative for the highest interior Antarctic Plateau.

  15. Large-scale distribution analysis of Antarctic echinoids using ecological niche modelling

    OpenAIRE

    Pierrat, B.; Saucede, T.; Laffont, R.; De Ridder, C.; Festeau, A.; David, B.

    2012-01-01

    Understanding the factors that determine the distribution of taxa at various spatial scales is a crucial challenge in the context of global climate change. This holds particularly true for polar marine biota that are composed of both highly adapted and vulnerable faunas. We analysed the distribution of 2 Antarctic echinoid species, Sterechinus antarcticus and S. neumayeri, at the scale of the entire Southern Ocean using 2 niche modelling procedures. The performance of distribution models was ...

  16. Evaluating Antarctic sea ice predictability at seasonal to interannual timescales in global climate models

    Science.gov (United States)

    Marchi, Sylvain; Fichefet, Thierry; Goosse, Hugues; Zunz, Violette; Tietsche, Steffen; Day, Jonny; Hawkins, Ed

    2016-04-01

    Unlike the rapid sea ice losses reported in the Arctic, satellite observations show an overall increase in Antarctic sea ice extent over recent decades. Although many processes have already been suggested to explain this positive trend, it remains the subject of current investigations. Understanding the evolution of the Antarctic sea ice turns out to be more complicated than for the Arctic for two reasons: the lack of observations and the well-known biases of climate models in the Southern Ocean. Irrespective of those issues, another one is to determine whether the positive trend in sea ice extent would have been predictable if adequate observations and models were available some decades ago. This study of Antarctic sea ice predictability is carried out using 6 global climate models (HadGEM1.2, MPI-ESM-LR, GFDL CM3, EC-Earth V2, MIROC 5.2 and ECHAM 6-FESOM) which are all part of the APPOSITE project. These models are used to perform hindcast simulations in a perfect model approach. The predictive skill is estimated thanks to the PPP (Potential Prognostic Predictability) and the ACC (Anomaly Correlation Coefficient). The former is a measure of the uncertainty of the ensemble while the latter assesses the accuracy of the prediction. These two indicators are applied to different variables related to sea ice, in particular the total sea ice extent and the ice edge location. This first model intercomparison study about sea ice predictability in the Southern Ocean aims at giving a general overview of Antarctic sea ice predictability in current global climate models.

  17. Ecological niche modeling of sympatric krill predators around Marguerite Bay, Western Antarctic Peninsula

    Science.gov (United States)

    Friedlaender, Ari S.; Johnston, David W.; Fraser, William R.; Burns, Jennifer; Halpin, Patrick N.; Costa, Daniel P.

    2011-07-01

    Adélie penguins ( Pygoscelis adeliae), carabeater seals ( Lobodon carcinophagus), humpback ( Megaptera novaeangliae), and minke whales ( Balaenoptera bonaernsis) are found in the waters surrounding the Western Antarctic Peninsula. Each species relies primarily on Antarctic krill ( Euphausia superba) and has physiological constraints and foraging behaviors that dictate their ecological niches. Understanding the degree of ecological overlap between sympatric krill predators is critical to understanding and predicting the impacts on climate-driven changes to the Antarctic marine ecosystem. To explore ecological relationships amongst sympatric krill predators, we developed ecological niche models using a maximum entropy modeling approach (Maxent) that allows the integration of data collected by a variety of means (e.g. satellite-based locations and visual observations). We created spatially explicit probability distributions for the four krill predators in fall 2001 and 2002 in conjunction with a suite of environmental variables. We find areas within Marguerite Bay with high krill predator occurrence rates or biological hot spots. We find the modeled ecological niches for Adélie penguins and crabeater seals may be affected by their physiological needs to haul-out on substrate. Thus, their distributions may be less dictated by proximity to prey and more so by physical features that over time provide adequate access to prey. Humpback and minke whales, being fully marine and having greater energetic demands, occupy ecological niches more directly proximate to prey. We also find evidence to suggest that the amount of overlap between modeled niches is relatively low, even for species with similar energetic requirements. In a rapidly changing and variable environment, our modeling work shows little indication that krill predators maintain similar ecological niches across years around Marguerite Bay. Given the amount of variability in the marine environment around the

  18. Assessment of the Breakup of the Antarctic Polar Vortex in Two New Chemistry-Climate Models

    Science.gov (United States)

    Hurwitz, M. M.; Newman, P. A.; Oman, L. D.; Li, F.; Morgenstern, O.; Braesicke, P.; Pyle, J. A.

    2010-01-01

    Successful simulation of the breakup of the Antarctic polar vortex depends on the representation of tropospheric stationary waves at Southern Hemisphere middle latitudes. This paper assesses the vortex breakup in two new chemistry-climate models (CCMs). The stratospheric version of the UK Chemistry and Aerosols model is able to reproduce the observed timing of the vortex breakup. Version 2 of the Goddard Earth Observing System (GEOS V2) model is typical of CCMs in that the Antarctic polar vortex breaks up too late; at 10 hPa, the mean transition to easterlies at 60 S is delayed by 12-13 days as compared with the ERA-40 and National Centers for Environmental Prediction reanalyses. The two models' skill in simulating planetary wave driving during the October-November period accounts for differences in their simulation of the vortex breakup, with GEOS V2 unable to simulate the magnitude and tilt of geopotential height anomalies in the troposphere and thus underestimating the wave driving. In the GEOS V2 CCM the delayed breakup of the Antarctic vortex biases polar temperatures and trace gas distributions in the upper stratosphere in November and December.

  19. Identifying distinct phytoplankton regions based on ocean colour data supplemented by in-situ and model data

    Science.gov (United States)

    Eliasen, Solva; Hátún, Hjálmar; Margretha Larsen, Karin; Hansen, Bogi

    2016-04-01

    The Faroe Shelf hosts a rich and diverse marine ecosystem, which sustains a large portion of the economy of the Islands. The primary production, even though often referred to as being important to the higher trophic levels, is still not thoroughly understood. A high resolution chlorophyll time series from coastal station S, dating back to 1997, has given valuable information about the phytoplankton concentrations on the central shelf, and interannual fluctuations (with a factor of 4-5) in this time series have been linked to several other biological indicators. However, with regards to phytoplankton and primary production farther off-shore, only CTD fluorescence observations from research cruises are available and a thorough analysis of these temporally and spatially scattered data is difficult to conduct and yet to be done. Thus, the spatial extent of the region, for which the station S phytoplankton concentrations are representative, is not well defined. In this study we compare satellite ocean colour data from 1998-2015 with in-situ data from station S and identify the region which station S represents. Moreover, we use the ocean colour data to identity biogeographical regions in which phytoplankton is uniquely and coherently varying and compare these with the breeding and feeding grounds of commercially important fish stocks. The surface chlorophyll pattern does not necessarily represent the primary production in the water column. We therefore supplement the results with hydrographic observations and model simulations and from these extract information about the total carbon production in the various regions. The ocean colour data are consistent with the in-situ observations and the results from combining these with the other data types have enhanced our understanding of timing and strength of the phytoplankton spring bloom farther off-shore and contribute to the understanding of the shelf ecosystem in general.

  20. Large-Ensemble modeling of last deglacial and future variations of the Antarctic Ice Sheet

    Science.gov (United States)

    Pollard, David; DeConto, Robert; Chang, Won; Applegate, Patrick; Haran, Murali

    2015-04-01

    Recent observations of thinning and retreat of the Pine Island and Thwaites Glaciers identify the Amundsen Sea Embayment (ASE) sector of West Antarctica as particularly vulnerable to future climate change. To date, most future modeling of these glaciers has been calibrated using recent and modern observations. As an alternate approach, we apply a hybrid 3-D ice sheet-shelf model to the last deglacial retreat of Antarctica, making use of geologic data from ~20,000 years BP to present, focusing on the ASE but including other sectors of Antarctica. Following several recent ice-sheet studies, we use Large-Ensemble statistical techniques, performing sets of ~500 to 1000 runs with varying model parameters. The model is run for the last 40 kyrs on 10 to 20-km grids, both on continental domains and also on nested domains over West Antarctica. Various types of objective scores for each run are calculated using reconstructed past grounding lines, relative sea level records, measured uplift rates, and cosmogenic elevation-age data. Runs are extended into the future few millennia using RCP scenarios. The goal is to produce calibrated probabilistic ranges of model parameter values and quantified envelopes of future ice retreat. Preliminary results are presented for Large Ensembles with (i) Latin HyperCube sampling in high-dimensional parameter space, using statistical emulators and Markov Chain Monte Carlo techniques, and (ii) dense "factorial" sampling with a smaller number of parameters. Different ways of combining the types of scores listed above are explored. One robust conclusion is that for the warmer future RCP scenarios, most reasonable parameter combinations produce retreat deep into the West Antarctic interior. Recently proposed mechanisms of hydrofracturing and ice-cliff failure accelerate future West Antarctic retreat, and later produce retreat into East Antarctic basins.

  1. Present-day Circum-Antarctic Simulations using the POPSICLES Coupled Ice Sheet-Ocean Model

    Science.gov (United States)

    Asay-Davis, X.; Martin, D. F.; Price, S. F.; Maltrud, M. E.; Collins, W.

    2014-12-01

    We present POPSICLES simulation results covering the full Antarctic Ice Sheet and the Southern Ocean spanning the period 1990 to 2010. Simulations are performed at 0.1o (~5 km) ocean resolution and with adaptive ice-sheet model resolution as fine as 500 m. We compare time-averaged melt rates below a number of major ice shelves with those reported by Rignot et al. (2013) as well as other recent studies. We also present seasonal variability and decadal trends in submarine melting from several Antarctic regions. Finally, we explore the influence on basal melting and system dynamics resulting from two different choices of climate forcing: a "normal-year" climatology and the CORE v. 2 forcing data (Large and Yeager 2008).POPSICLES couples the POP2x ocean model, a modified version of the Parallel Ocean Program (Smith and Gent, 2002), and the BISICLES ice-sheet model (Cornford et al., 2012). POP2x includes sub-ice-shelf circulation using partial top cells (Losch, 2008) and boundary layer physics following Holland and Jenkins (1999), Jenkins (2001), and Jenkins et al. (2010). Standalone POP2x output compares well with standard ice-ocean test cases (e.g., ISOMIP; Losch, 2008) and other continental-scale simulations and melt-rate observations (Kimura et al., 2013; Rignot et al., 2013). BISICLES makes use of adaptive mesh refinement and a 1st-order accurate momentum balance similar to the L1L2 model of Schoof and Hindmarsh (2009) to accurately model regions of dynamic complexity, such as ice streams, outlet glaciers, and grounding lines. Results of BISICLES simulations have compared favorably to comparable simulations with a Stokes momentum balance in both idealized tests (MISMIP-3D; Pattyn et al., 2013) and realistic configurations (Favier et al. 2014).A companion presentation, "Response of the Antarctic Ice Sheet to ocean forcing using the POPSICLES coupled ice sheet-ocean model" in session C024 covers the ice-sheet response to these melt rates in the coupled simulation

  2. A biogeochemical model of Lake Pusiano (North Italy and its use in the predictability of phytoplankton blooms: first preliminary results

    Directory of Open Access Journals (Sweden)

    Alessandro OGGIONI

    2006-02-01

    Full Text Available This study reports the first preliminary results of the DYRESM-CAEDYM model application to a mid size sub-alpine lake (Lake Pusiano North Italy. The in-lake modelling is a part of a more general project called Pusiano Integrated Lake/Catchment project (PILE whose final goal is to understand the hydrological and trophic relationship between lake and catchment, supporting the restoration plan of the lake through field data analysis and numerical models. DYRESM is a 1D-3D hydrodynamics model for predicting the vertical profile of temperature, salinity and density. CAEDYM is multi-component ecological model, used here as a phytoplankton-zooplankton processes based model, which includes algorithms to simulate the nutrient cycles within the water column as well as the air-water gas exchanges and the water-sediments fluxes. The first results of the hydrodynamics simulations underline the capability of the model to accurately simulate the surface temperature seasonal trend and the thermal gradient whereas, during summer stratification, the model underestimates the bottom temperature of around 2 °C. The ecological model describes the epilimnetic reactive phosphorus (PO4 depletion (due to the phytoplankton uptake and the increase in PO4 concentrations in the deepest layers of the lake (due to the mineralization processes and the sediments release. In terms of phytoplankton dynamics the model accounts for the Planktothrix rubescens dominance during the whole season, whereas it seems to underestimate the peak in primary production related to both the simulated algal groups (P. rubescens and the rest of the other species aggregated in a single class. The future aims of the project are to complete the model parameterization and to connect the in-lake and the catchment modelling in order to gain an integrated view of the lake-catchment ecosystem as well as to develop a three dimensional model of the lake.

  3. Challenges in modelling spatiotemporally varying phytoplankton blooms in the Northwestern Arabian Sea and Gulf of Oman

    Directory of Open Access Journals (Sweden)

    S. Sedigh Marvasti

    2015-07-01

    Full Text Available We examine interannual variability of phytoplankton blooms in northwestern Arabian Sea and Gulf of Oman. Satellite data (SeaWIFS ocean color shows two climatological blooms in this region, a wintertime bloom peaking in February and a summertime bloom peaking in September. A pronounced anti-correlation between the AVISO sea surface height anomaly (SSHA and chlorophyll is found during the wintertime bloom. On a regional scale, interannual variability of the wintertime bloom is thus dominated by cyclonic eddies which vary in location from one year to another. These results were compared against the outputs from three different 3-D Earth System models. We show that two coarse (1° models with the relatively complex biogeochemistry (TOPAZ capture the annual cycle but neither eddies nor the interannual variability. An eddy-resolving model (GFDL CM2.6 with a simpler biogeochemistry (miniBLING displays larger interannual variability, but overestimates the wintertime bloom and captures eddy-bloom coupling in the south but not in the north. The southern part of the domain is a region with a much sharper thermocline and nutricline relatively close to the surface, in which eddies modulate diffusive nutrient supply to the surface (a mechanism not previously emphasized in the literature. We suggest that for the model to simulate the observed wintertime blooms within cyclones, it will be necessary to represent this relatively unusual nutrient structure as well as the cyclonic eddies. This is a challenge in the Northern Arabian Sea as it requires capturing the details of the outflow from the Persian Gulf.

  4. Subduction of Pacific Antarctic Intermediate Water in an eddy-resolving model

    Science.gov (United States)

    Hiraike, Yuri; Tanaka, Yukio; Hasumi, Hiroyasu

    2016-01-01

    The subduction process of Pacific Antarctic Intermediate Water (PAAIW) in the Pacific is investigated using output from an eddy-resolving ocean model. Focus is on contribution of eddies to the subduction process. To separate the subduction rate into contributions by eddies and mean flows, the temporal residual mean (TRM) velocity is used. In the mean subduction rate, lateral induction caused by the strong eastward flow of the Antarctic Circumpolar Current (ACC) is dominant. The largest rate is located in the Drake Passage. The estimated eddy-induced subduction rate is comparable with the mean subduction rate, and it tends to cancel the vertical mean component in many regions. In the west of the Drake Passage, however, the eddy-induced subduction is larger than the vertical mean component, and this eddy-induced subduction was not detected in previous studies using the thickness diffusion parameterization and an eddy-permitting model. Results of idealized sensitivity studies to model resolution suggest that the subduction rate would be larger using a model with higher vertical resolution. Therefore, the vertical resolution should be paid more attention in model studies investigating eddy-induced subduction, and not just the horizontal resolution.

  5. Polythermal modelling of steady states of the Antarctic ice sheet in comparison with the real world

    OpenAIRE

    Hansen, I.; Greve, Ralf

    1996-01-01

    An approach to simulate the present Antarctic ice sheet with respect to its thermomechanical behaviour and the resulting features is made with the three-dimensional polythermal ice-sheet model designed by Greve and Hutter. It treats zones of cold and temperate ice as different materials with their own properties and dynamics. This is important becausc an underlying layer of temperate ice can influence the ice sheet as a whole, e.g. the cold ice may slide upon the less viscous binary ice-water...

  6. Emergence of steady and oscillatory localized structures in a phytoplankton-nutrient model

    OpenAIRE

    Zagaris, Antonios; Doelman, Arjen

    2010-01-01

    Co-limitation of marine phytoplankton growth by light and nutrient, both of which are essential for phytoplankton, leads to complex dynamic behavior and a wide array of coherent patterns. The building blocks of this array can be considered to be deep chlorophyll maxima, or DCMs, which are structures localized in a finite depth interior to the water column. From an ecological point of view, DCMs are evocative of a balance between the inflow of light from the water surface and of nutrients from...

  7. Evidence for link between modelled trends in Antarctic sea ice and underestimated westerly wind changes

    Science.gov (United States)

    Purich, Ariaan; Cai, Wenju; England, Matthew H.; Cowan, Tim

    2016-02-01

    Despite global warming, total Antarctic sea ice coverage increased over 1979-2013. However, the majority of Coupled Model Intercomparison Project phase 5 models simulate a decline. Mechanisms causing this discrepancy have so far remained elusive. Here we show that weaker trends in the intensification of the Southern Hemisphere westerly wind jet simulated by the models may contribute to this disparity. During austral summer, a strengthened jet leads to increased upwelling of cooler subsurface water and strengthened equatorward transport, conducive to increased sea ice. As the majority of models underestimate summer jet trends, this cooling process is underestimated compared with observations and is insufficient to offset warming in the models. Through the sea ice-albedo feedback, models produce a high-latitude surface ocean warming and sea ice decline, contrasting the observed net cooling and sea ice increase. A realistic simulation of observed wind changes may be crucial for reproducing the recent observed sea ice increase.

  8. Evidence for link between modelled trends in Antarctic sea ice and underestimated westerly wind changes.

    Science.gov (United States)

    Purich, Ariaan; Cai, Wenju; England, Matthew H; Cowan, Tim

    2016-01-01

    Despite global warming, total Antarctic sea ice coverage increased over 1979-2013. However, the majority of Coupled Model Intercomparison Project phase 5 models simulate a decline. Mechanisms causing this discrepancy have so far remained elusive. Here we show that weaker trends in the intensification of the Southern Hemisphere westerly wind jet simulated by the models may contribute to this disparity. During austral summer, a strengthened jet leads to increased upwelling of cooler subsurface water and strengthened equatorward transport, conducive to increased sea ice. As the majority of models underestimate summer jet trends, this cooling process is underestimated compared with observations and is insufficient to offset warming in the models. Through the sea ice-albedo feedback, models produce a high-latitude surface ocean warming and sea ice decline, contrasting the observed net cooling and sea ice increase. A realistic simulation of observed wind changes may be crucial for reproducing the recent observed sea ice increase. PMID:26842498

  9. Numerical Modeling of the Effects of Nutrient-rich Coastal-water Input on the Phytoplankton in the Gulf of California

    Science.gov (United States)

    Bermudez, A.; Rivas, D.

    2015-12-01

    Phytoplankton bloom dynamics depends on the interactions of favorable physical, chemical, and biotic conditions, particularly on the available nutrients that enhance phytoplankton growth, like nitrogen. Costal and estuarine environments are heavily influenced by exogenous sources of nitrogen; the anthropogenic inputs include urban and rural wastewater coming from agricultural activities (i.e., fertilizers and animal waste). In response, new production is often enhanced, leading eutrophication and phytoplankton blooms, including harmful taxa. These events have become more frequent, and with it the interest to evaluate their effects on marine ecosystems and the impact on human health. In the Gulf of California the harmful algal blooms (HABs) had affected aquaculture, fisheries, and even tourism, thereby it is important to generate information about biological and physical factors that can influence their appearance. A numerical model is a tool that may bring key information about the origin and distribution of phytoplankton blooms. Herein the analysis is based on a three-dimensional, hydrodynamical numerical model, coupled to a Nitrogen-Phytoplankton-Zooplankton-Detritus (NPZD) model. Several numerical simulations using different forcing and scenarios are carried out in order to evaluate the processes that influence the phytoplankton growth. These numerical results are compared to available observations. Thus, the main environmental factors triggering the generation of HABs can be identified.

  10. Stochastic superparameterization in a quasigeostrophic model of the Antarctic Circumpolar Current

    Science.gov (United States)

    Grooms, Ian; Majda, Andrew J.; Smith, K. Shafer

    2015-01-01

    Stochastic superparameterization, a stochastic parameterization framework based on a multiscale formalism, is developed for mesoscale eddy parameterization in coarse-resolution ocean modeling. The framework of stochastic superparameterization is reviewed and several configurations are implemented and tested in a quasigeostrophic channel model - an idealized representation of the Antarctic Circumpolar Current. Five versions of the Gent-McWilliams (GM) parameterization are also implemented and tested for comparison. Skill is measured using the time-mean and temporal variability separately, and in combination using the relative entropy in the single-point statistics. Among all the models, those with the more accurate mean state have the less accurate variability, and vice versa. Stochastic superparameterization results in improved climate fidelity in comparison with GM parameterizations as measured by the relative entropy. In particular, configurations of stochastic superparameterization that include stochastic Reynolds stress terms in the coarse model equations, corresponding to kinetic energy backscatter, perform better than models that only include isopycnal height smoothing.

  11. Present-day and future Antarctic ice sheet climate and surface mass balance in the Community Earth System Model

    Science.gov (United States)

    Lenaerts, Jan T. M.; Vizcaino, Miren; Fyke, Jeremy; van Kampenhout, Leo; van den Broeke, Michiel R.

    2016-09-01

    We present climate and surface mass balance (SMB) of the Antarctic ice sheet (AIS) as simulated by the global, coupled ocean-atmosphere-land Community Earth System Model (CESM) with a horizontal resolution of {˜ }1° in the past, present and future (1850-2100). CESM correctly simulates present-day Antarctic sea ice extent, large-scale atmospheric circulation and near-surface climate, but fails to simulate the recent expansion of Antarctic sea ice. The present-day Antarctic ice sheet SMB equals 2280 ± 131 {Gt year^{-1}}, which concurs with existing independent estimates of AIS SMB. When forced by two CMIP5 climate change scenarios (high mitigation scenario RCP2.6 and high-emission scenario RCP8.5), CESM projects an increase of Antarctic ice sheet SMB of about 70 {Gt year^{-1}} per degree warming. This increase is driven by enhanced snowfall, which is partially counteracted by more surface melt and runoff along the ice sheet's edges. This intensifying hydrological cycle is predominantly driven by atmospheric warming, which increases (1) the moisture-carrying capacity of the atmosphere, (2) oceanic source region evaporation, and (3) summer AIS cloud liquid water content.

  12. The neglect of cliff instability can underestimate warming period melting in Antarctic ice sheet models

    CERN Document Server

    Ruckert, Kelsey L; Pollard, Dave; Guan, Yawen; Wong, Tony E; Forest, Chris E; Keller, Klaus

    2016-01-01

    The response of the Antarctic ice sheet (AIS) to changing climate forcings is an important driver of sea-level changes. Anthropogenic climate changes may drive a sizeable AIS tipping point response with subsequent increases in coastal flooding risks. Many studies analyzing flood risks use simple models to project the future responses of AIS and its sea-level contributions. These analyses have provided important new insights, but they are often silent on the effects of potentially important processes such as Marine Ice Sheet Instability (MISI) or Marine Ice Cliff Instability (MICI). These approximations can be well justified and result in more parsimonious and transparent model structures. This raises the question how this approximation impacts hindcasts and projections. Here, we calibrate a previously published AIS model, which neglects the effects of MICI, using a combination of observational constraints and a Bayesian inversion method. Specifically, we approximate the effects of missing MICI by comparing ou...

  13. MAGIC-DML: Mapping/Measuring/Modeling Antarctic Geomorphology & Ice Change in Dronning Maud Land

    Science.gov (United States)

    Rogozhina, Irina; Bernales, Jorge; Newall, Jennifer; Stroeven, Arjen; Harbor, Jonathan; Glasser, Neil; Fredin, Ola; Fabel, Derek; Hättestrand, Class; Lifton, Nat

    2016-04-01

    Reconstructing and predicting the response of the Antarctic Ice Sheet to climate change is one of the major challenges facing the Earth Science community. There are critical gaps in our knowledge of past changes in ice elevation and extent in many regions of East Antarctica, including a large area of Dronning Maud Land. An international Swedish-UK-US-Norwegian-German project MAGIC-DML aims to reconstruct the timing and pattern of ice surface elevation (thus ice sheet volume) fluctuations since the mid-Pliocene warm period on the Dronning Maud Land margin of the East Antarctic Ice Sheet. A combination of remotely sensed geomorphological mapping, field investigations, surface exposure dating and numerical modelling are being used in an iterative manner to produce a comprehensive reconstruction of the glacial history of Dronning Maud Land. Here we present the results from the first phase of this project, which involves high-resolution numerical simulations of the past glacial geometries and mapping of the field area using historic and recent aerial imagery together with a range of satellite acquired data.

  14. A coupled physical-biological model of the Northern Gulf of Mexico shelf: model description, validation and analysis of phytoplankton variability

    Directory of Open Access Journals (Sweden)

    K. Fennel

    2011-07-01

    Full Text Available The Texas-Louisiana shelf in the Northern Gulf of Mexico receives large inputs of nutrients and freshwater from the Mississippi/Atchafalaya River system. The nutrients stimulate high rates of primary production in the river plume, which contributes to the development of a large and recurring hypoxic area in summer, but the mechanistic links between hypoxia and river discharge of freshwater and nutrients are complex as the accumulation and vertical export of organic matter, the establishment and maintenance of vertical stratification, and the microbial degradation of organic matter are controlled by a non-linear interplay of factors. Unraveling these interactions will have to rely on a combination of observations and models. Here we present results from a realistic, 3-dimensional, physical-biological model with focus on a quantification of nutrient-stimulated phytoplankton growth, its variability and the fate of this organic matter. We demonstrate that the model realistically reproduces many features of observed nitrate and phytoplankton dynamics including observed property distributions and rates. We then contrast the environmental factors and phytoplankton source and sink terms characteristic of three model subregions that represent an ecological gradient from eutrophic to oligotrophic conditions. We analyze specifically the reasons behind the counterintuitive observation that primary production in the light-limited plume region near the Mississippi River delta is positively correlated with river nutrient input, and find that, while primary production and phytoplankton biomass are positively correlated with nutrient load, phytoplankton growth rate is not. This suggests that accumulation of biomass in this region is not primarily controlled bottom up by nutrient-stimulation, but top down by systematic differences in the loss processes.

  15. Phytoplankton's motion in turbulent ocean.

    Science.gov (United States)

    Fouxon, Itzhak; Leshansky, Alexander

    2015-07-01

    We study the influence of turbulence on upward motion of phytoplankton. Interaction with the flow is described by the Pedley-Kessler model considering spherical microorganisms. We find a range of parameters when the upward drift is only weakly perturbed or when turbulence completely randomizes the drift direction. When the perturbation is small, the drift is either determined by the local vorticity or is Gaussian. We find a range of parameters where the phytoplankton interaction with the flow can be described consistently as diffusion of orientation in effective potential. By solving the corresponding Fokker-Planck equation we find exponential steady-state distribution of phytoplankton's propulsion orientation. We further identify the range of parameters where phytoplankton's drift velocity with respect to the flow is determined uniquely by its position. In this case, one can describe phytoplankton's motion by a smooth flow and phytoplankton concentrates on fractal. We find fractal dimensions and demonstrate that phytoplankton forms vertical stripes in space with a nonisotropic pair-correlation function of concentration increased in the vertical direction. The probability density function of the distance between two particles obeys power law with the negative exponent given by the ratio of integrals of the turbulent energy spectrum. We find the regime of strong clustering where the exponent is of order one so that turbulence increases the rate of collisions by a large factor. The predictions hold for Navier-Stokes turbulence and stand for testing. PMID:26274279

  16. A decade of progress in observing and modelling Antarctic subglacial water systems.

    Science.gov (United States)

    Fricker, Helen A; Siegfried, Matthew R; Carter, Sasha P; Scambos, Ted A

    2016-01-28

    In the decade since the discovery of active Antarctic subglacial water systems by detection of subtle surface displacements, much progress has been made in our understanding of these dynamic systems. Here, we present some of the key results of observations derived from ICESat laser altimetry, CryoSat-2 radar altimetry, Operation IceBridge airborne laser altimetry, satellite image differencing and ground-based continuous Global Positioning System (GPS) experiments deployed in hydrologically active regions. These observations provide us with an increased understanding of various lake systems in Antarctica: Whillans/Mercer Ice Streams, Crane Glacier, Recovery Ice Stream, Byrd Glacier and eastern Wilkes Land. In several cases, subglacial water systems are shown to control ice flux through the glacier system. For some lake systems, we have been able to construct more than a decade of continuous lake activity, revealing internal variability on time scales ranging from days to years. This variability indicates that continuous, accurate time series of altimetry data are critical to understanding these systems. On Whillans Ice Stream, our results from a 5-year continuous GPS record demonstrate that subglacial lake flood events significantly change the regional ice dynamics. We also show how models for subglacial water flow have evolved since the availability of observations of lake volume change, from regional-scale models of water routeing to process models of channels carved into the subglacial sediment instead of the overlying ice. We show that progress in understanding the processes governing lake drainage now allows us to create simulated lake volume time series that reproduce time series from satellite observations. This transformational decade in Antarctic subglacial water research has moved us significantly closer to understanding the processes of water transfer sufficiently for inclusion in continental-scale ice-sheet models. PMID:26667904

  17. A decade of progress in observing and modelling Antarctic subglacial water systems.

    Science.gov (United States)

    Fricker, Helen A; Siegfried, Matthew R; Carter, Sasha P; Scambos, Ted A

    2016-01-28

    In the decade since the discovery of active Antarctic subglacial water systems by detection of subtle surface displacements, much progress has been made in our understanding of these dynamic systems. Here, we present some of the key results of observations derived from ICESat laser altimetry, CryoSat-2 radar altimetry, Operation IceBridge airborne laser altimetry, satellite image differencing and ground-based continuous Global Positioning System (GPS) experiments deployed in hydrologically active regions. These observations provide us with an increased understanding of various lake systems in Antarctica: Whillans/Mercer Ice Streams, Crane Glacier, Recovery Ice Stream, Byrd Glacier and eastern Wilkes Land. In several cases, subglacial water systems are shown to control ice flux through the glacier system. For some lake systems, we have been able to construct more than a decade of continuous lake activity, revealing internal variability on time scales ranging from days to years. This variability indicates that continuous, accurate time series of altimetry data are critical to understanding these systems. On Whillans Ice Stream, our results from a 5-year continuous GPS record demonstrate that subglacial lake flood events significantly change the regional ice dynamics. We also show how models for subglacial water flow have evolved since the availability of observations of lake volume change, from regional-scale models of water routeing to process models of channels carved into the subglacial sediment instead of the overlying ice. We show that progress in understanding the processes governing lake drainage now allows us to create simulated lake volume time series that reproduce time series from satellite observations. This transformational decade in Antarctic subglacial water research has moved us significantly closer to understanding the processes of water transfer sufficiently for inclusion in continental-scale ice-sheet models.

  18. Correlative and dynamic species distribution modelling for ecological predictions in the Antarctic: a cross-disciplinary concept

    Directory of Open Access Journals (Sweden)

    Thomas Saucède

    2012-05-01

    Full Text Available Developments of future scenarios of Antarctic ecosystems are still in their infancy, whilst predictions of the physical environment are recognized as being of global relevance and corresponding models are under continuous development. However, in the context of environmental change simulations of the future of the Antarctic biosphere are increasingly demanded by decision makers and the public, and are of fundamental scientific interest. This paper briefly reviews existing predictive models applied to Antarctic ecosystems before providing a conceptual framework for the further development of spatially and temporally explicit ecosystem models. The concept suggests how to improve approaches to relating species’ habitat description to the physical environment, for which a case study on sea urchins is presented. In addition, the concept integrates existing and new ideas to consider dynamic components, particularly information on the natural history of key species, from physiological experiments and biomolecular analyses. Thereby, we identify and critically discuss gaps in knowledge and methodological limitations. These refer to process understanding of biological complexity, the need for high spatial resolution oceanographic data from the entire water column, and the use of data from biomolecular analyses in support of such ecological approaches. Our goal is to motivate the research community to contribute data and knowledge to a holistic, Antarctic-specific, macroecological framework. Such a framework will facilitate the integration of theoretical and empirical work in Antarctica, improving our mechanistic understanding of this globally influential ecoregion, and supporting actions to secure this biodiversity hotspot and its ecosystem services.

  19. Uncertainties in Ensemble Predictions of Future Antarctic Mass Loss with the fETISh Model

    Science.gov (United States)

    Pattyn, F.

    2015-12-01

    Marine ice sheet models should be capable of handling complex feedbacks between ice and ocean, such as marine ice sheet instability, and the atmosphere, such as the elevation-mass balance feedback, operating at different time scales. Recent model intercomparisons (e.g., SeaRISE, MISMIP) have shown that the complexity of many ice sheet models is focused on processes that are either not well captured numerically (spatial resolution issue) or are of secondary importance compared to the essential features of marine ice sheet dynamics. Here, we propose a new and fast computing ice sheet model, devoid of most complexity, but capturing the essential feedbacks when coupled to ocean or atmospheric models. Its computational efficiency guarantees to easily tests its advantages as well as limits through ensemble modelling. The fETISh (fast Elementary Thermomechanical (marine) Ice Sheet) model is a vertically integrated hybrid (SSA/SIA) ice sheet model. Although vertically integrated, thermomechanical coupling is ensured through a simplified representation of ice sheet thermodynamics based on an analytical solution of the vertical temperature profile, including strain heating and horizontal advection. The marine boundary is represented by a flux condition similar to Pollard & Deconto (2012), based on Schoof (2007). Buttressing of ice shelves is taken into account via the Shallow-Shelf Approximation (SSA). The ice sheet model is solved on four staggered finite difference grids for numerical efficiency/stability. Numerical tests following EISMINT, ISMIP and MISMIP are performed as a prerequisite. The fETISh model is forced with different ice-shelf melt rates and basal sliding perturbations to allow comparison with recent model intercomparisons of the Antarctic ice sheet (e.g., SeaRISE, Favier et al. (2013)). These forcings are further completed with a set of scenarios involving ice-shelf buttressing and unbuttressing. All experiments are carried out on different spatial

  20. Simulation of upper-ocean biogeochemistry with a flexible-composition phytoplankton model: C, N and Si cycling and Fe limitation in the Southern Ocean

    Science.gov (United States)

    Mongin, Mathieu; Nelson, David M.; Pondaven, Philippe; Tréguer, Paul

    2006-03-01

    We previously reported the application of an upper-ocean biogeochemical model in which the elemental composition of the phytoplankton is flexible and responds to changes in light and nutrient availability [Mongin, M., Nelson, D., Pondaven, P., Brzezinski, M., Tréguer, P., 2003. Simulation of upper-ocean biogeochemistry with a flexible-composition phytoplankton model: C, N and Si cycling in the western Sargasso Sea. Deep-Sea Research I 50, 1445-1480]. That model, applied in the western Sargasso Sea, considered the cycles of C, N and Si in the upper 400 m and limitation of phytoplankton growth by N, Si and light. We now report a new version of this model that includes Fe cycling and Fe limitation and its application in the Southern Ocean. The model includes two phytoplankton groups, diatoms and non-siliceous forms. Uptake of NO 3- by phytoplankton is light dependent, but NH 4+, Si(OH) 4 and Fe uptake are not and can therefore continue through the night. The model tracks the resulting C/N and Fe/C ratios of both groups and Si/N ratio of diatoms, and permits uptake of C, N, Fe and Si to proceed independently when those ratios are close to those of nutrient-replete phytoplankton. When they indicate a deficiency cellular C, N, Fe or Si, uptake of the non-limiting elements is controlled by the content of the limiting element in accordance with the cell-quota formulation of [Droop, M., 1974. The nutrient status of algal cell in continuous culture. Journal of the Marine Biological Association of the United Kingdom 54, 825-855]. The model thus identifies the growth-limiting element and quantifies the degree of limitation from the elemental composition of the phytoplankton. We applied this model at the French KERFIX site in the Indian Ocean sector of the Southern Ocean, using meteorological forcing for that site from 1991 to 1995. As in the Sargasso Sea application, the flexible-composition structure provides simulations that are consistent with field data with only minimal

  1. Impact of surface wind biases on the Antarctic sea ice concentration budget in climate models

    Science.gov (United States)

    Lecomte, O.; Goosse, H.; Fichefet, T.; Holland, P. R.; Uotila, P.; Zunz, V.; Kimura, N.

    2016-09-01

    We derive the terms in the Antarctic sea ice concentration budget from the output of three models, and compare them to observations of the same terms. Those models include two climate models from the 5th Coupled Model Intercomparison Project (CMIP5) and one ocean-sea ice coupled model with prescribed atmospheric forcing. Sea ice drift and wind fields from those models, in average over April-October 1992-2005, all exhibit large differences with the available observational or reanalysis datasets. However, the discrepancies between the two distinct ice drift products or the two wind reanalyses used here are sometimes even greater than those differences. Two major findings stand out from the analysis. Firstly, large biases in sea ice drift speed and direction in exterior sectors of the sea ice covered region tend to be systematic and consistent with those in winds. This suggests that sea ice errors in these areas are most likely wind-driven, so as errors in the simulated ice motion vectors. The systematic nature of these biases is less prominent in interior sectors, nearer the coast, where sea ice is mechanically constrained and its motion in response to the wind forcing more depending on the model rheology. Second, the intimate relationship between winds, sea ice drift and the sea ice concentration budget gives insight on ways to categorize models with regard to errors in their ice dynamics. In exterior regions, models with seemingly too weak winds and slow ice drift consistently yield a lack of ice velocity divergence and hence a wrong wintertime sea ice growth rate. In interior sectors, too slow ice drift, presumably originating from issues in the physical representation of sea ice dynamics as much as from errors in surface winds, leads to wrong timing of the late winter ice retreat. Those results illustrate that the applied methodology provides a valuable tool for prioritizing model improvements based on the ice concentration budget-ice drift biases-wind biases

  2. Projecting Antarctic ice discharge using response functions from SeaRISE ice-sheet models

    Directory of Open Access Journals (Sweden)

    A. Levermann

    2012-08-01

    Full Text Available The largest uncertainty in projections of future sea-level change still results from the potentially changing dynamical ice discharge from Antarctica. While ice discharge can alter through a number of processes, basal ice-shelf melting induced by a warming ocean has been identified as a major if not the major cause for possible additional ice flow across the grounding line. Here we derive dynamic ice-sheet response functions for basal ice-shelf melting using experiments carried out within the Sea-level Response to Ice Sheet Evolution (SeaRISE intercomparison project with five different Antarctic ice-sheet models. As used here these response functions provide separate contributions for four different Antarctic drainage regions. Under the assumptions of linear-response theory we project future ice-discharge for each model, each region and each of the four Representative Concentration Pathways (RCP using oceanic temperatures from 19 comprehensive climate models of the Coupled Model Intercomparison Project, CMIP-5, and two ocean models from the EU-project Ice2Sea. Uncertainty in the climatic forcing, the oceanic response and the ice-model differences is combined into an uncertainty range of future Antarctic ice-discharge induced from basal ice-shelf melt. The additional ice-loss (Table 6 is clearly scenario-dependent and results in a median of 0.07 m (66%-range: 0.04–0.10 m; 90%-range: −0.01–0.26 m of global sea-level equivalent for the low-emission RCP-2.6 scenario and yields 0.1 m (66%-range: 0.06–0.14 m; 90%-range: −0.01–0.45 m for the strongest RCP-8.5. If only models with an explicit representation of ice-shelves are taken into account the scenario dependence remains and the values change to: 0.05 m (66%-range: 0.03–0.08 m for RCP-2.6 and 0.07 m (66%-range: 0.04–0.11 m for RCP-8.5. These results were obtained using a time delay between the surface warming signal and the subsurface oceanic warming as observed in the CMIP-5 models

  3. Parameter Estimations of Dynamic Energy Budget (DEB Model over the Life History of a Key Antarctic Species: The Antarctic Sea Star Odontaster validus Koehler, 1906.

    Directory of Open Access Journals (Sweden)

    Antonio Agüera

    Full Text Available Marine organisms in Antarctica are adapted to an extreme ecosystem including extremely stable temperatures and strong seasonality due to changes in day length. It is now largely accepted that Southern Ocean organisms are particularly vulnerable to global warming with some regions already being challenged by a rapid increase of temperature. Climate change affects both the physical and biotic components of marine ecosystems and will have an impact on the distribution and population dynamics of Antarctic marine organisms. To predict and assess the effect of climate change on marine ecosystems a more comprehensive knowledge of the life history and physiology of key species is urgently needed. In this study we estimate the Dynamic Energy Budget (DEB model parameters for key benthic Antarctic species the sea star Odontaster validus using available information from literature and experiments. The DEB theory is unique in capturing the metabolic processes of an organism through its entire life cycle as a function of temperature and food availability. The DEB model allows for the inclusion of the different life history stages, and thus, becomes a tool that can be used to model lifetime feeding, growth, reproduction, and their responses to changes in biotic and abiotic conditions. The DEB model presented here includes the estimation of reproduction handling rules for the development of simultaneous oocyte cohorts within the gonad. Additionally it links the DEB model reserves to the pyloric caeca an organ whose function has long been ascribed to energy storage. Model parameters described a slowed down metabolism of long living animals that mature slowly. O. validus has a large reserve that-matching low maintenance costs- allow withstanding long periods of starvation. Gonad development is continuous and individual cohorts developed within the gonads grow in biomass following a power function of the age of the cohort. The DEB model developed here for O

  4. A coupled physical-biological model of the Northern Gulf of Mexico shelf: model description, validation and analysis of phytoplankton variability

    Directory of Open Access Journals (Sweden)

    K. Fennel

    2011-01-01

    Full Text Available The Texas-Louisiana shelf in the Northern Gulf of Mexico receives large inputs of nutrients and freshwater from the Mississippi/Atchafalaya River system. The nutrients stimulate high rates of primary production in the river plume, which contributes to the development of a large and recurring hypoxic area in summer. The mechanistic links between hypoxia and river discharge of freshwater and nutrients are complex as the accumulation and vertical export of organic matter, the establishment and maintenance of vertical stratification, and the microbial degradation of organic matter are controlled by a non-linear interplay of factors. We present results from a realistic, 3-dimensional, physical-biological model that includes the processes thought to be of first order importance to hypoxia formation and demonstrate that the model realistically reproduces many features of observed nitrate and phytoplankton dynamics including observed property distributions and rates. We then contrast the environmental factors and phytoplankton source and sink terms characteristic of three model subregions that represent an ecological gradient from eutrophic to oligotrophic conditions. We analyze specifically the reasons behind the counterintuitive observation that primary production in the light-limited plume region near the Mississippi River delta is positively correlated with river nutrient input. We find that, while primary production and phytoplankton biomass are positively correlated with nutrient load, phytoplankton growth rate is not. This suggests that accumulation of biomass in this region is not primarily controlled bottom up by nutrient-stimulation, but top down by systematic differences in the loss processes. We hypothesize that increased retention of river water in high discharge years explains this phenomenon.

  5. Climate change impacts on net primary production (NPP and export production (EP regulated by increasing stratification and phytoplankton community structure in CMIP5 models

    Directory of Open Access Journals (Sweden)

    W. Fu

    2015-08-01

    Full Text Available We examine climate change impacts on net primary production (NPP and export production (sinking particulate flux; EP with simulations from nine Earth System Models (ESMs performed in the framework of the fifth Coupled Model Inter-comparison Project (CMIP5. Global NPP and EP are reduced considerably by the end of the century for the intense warming scenario of Representative Concentration Pathway (RCP 8.5. Relative to the 1990s, global NPP in the 2090s is reduced by 2.3–16 % and EP by 7–18 %. The models with the largest increases in stratification (and largest relative reductions in NPP and EP also show the largest positive biases in stratification for the contemporary period, suggesting some potential overestimation of climate impacts on NPP and EP. All of the CMIP5 models show an increase in stratification in response to surface ocean warming and freshening that is accompanied by decreases in NPP, EP, and surface macronutrient concentrations. There is considerable variability across models in the absolute magnitude of these fluxes, surface nutrient concentrations, and their perturbations by climate change, indicating large model uncertainties. The negative response of NPP and EP to stratification increases reflects a bottom-up control, as nutrient flux to the euphotic zone declines. Models with dynamic phytoplankton community structure show larger declines in EP than in NPP. This is driven by phytoplankton community composition shifts, with a reduced percentage of NPP by large phytoplankton under RCP 8.5, as smaller phytoplankton are favored under the increasing nutrient stress. Thus, projections of the NPP response to climate change in the CMIP5 models are critically dependent on the simulated phytoplankton community structure, the efficiency of the biological pump, and the resulting (highly variable levels of regenerated production. Community composition is represented relatively simply in the CMIP5 models, and should be expanded to

  6. Thin Layer Sensory Cues Affect Antarctic Krill Swimming Kinematics

    Science.gov (United States)

    True, A. C.; Webster, D. R.; Weissburg, M. J.; Yen, J.

    2013-11-01

    A Bickley jet (laminar, planar free jet) is employed in a recirculating flume system to replicate thin shear and phytoplankton layers for krill behavioral assays. Planar laser-induced fluorescence (LIF) and particle image velocimetry (PIV) measurements quantify the spatiotemporal structure of the chemical and free shear layers, respectively, ensuring a close match to in situ hydrodynamic and biochemical conditions. Path kinematics from digitized trajectories of free-swimming Euphausia superba examine the effects of hydrodynamic sensory cues (deformation rate) and bloom level phytoplankton patches (~1000 cells/mL, Tetraselamis spp.) on krill behavior (body orientation, swimming modes and kinematics, path fracticality). Krill morphology is finely tuned for receiving and deciphering both hydrodynamic and chemical information that is vital for basic life processes such as schooling behaviors, predator/prey, and mate interactions. Changes in individual krill behavior in response to ecologically-relevant sensory cues have the potential to produce population-scale phenomena with significant ecological implications. Krill are a vital trophic link between primary producers (phytoplankton) and larger animals (seabirds, whales, fish, penguins, seals) as well as the subjects of a valuable commercial fishery in the Southern Ocean; thus quantifying krill behavioral responses to relevant sensory cues is an important step towards accurately modeling Antarctic ecosystems.

  7. Climate change impacts on net primary production (NPP) and export production (EP) regulated by increasing stratification and phytoplankton community structure in the CMIP5 models

    Science.gov (United States)

    Fu, Weiwei; Randerson, James T.; Moore, J. Keith

    2016-09-01

    We examine climate change impacts on net primary production (NPP) and export production (sinking particulate flux; EP) with simulations from nine Earth system models (ESMs) performed in the framework of the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Global NPP and EP are reduced by the end of the century for the intense warming scenario of Representative Concentration Pathway (RCP) 8.5. Relative to the 1990s, NPP in the 2090s is reduced by 2-16 % and EP by 7-18 %. The models with the largest increases in stratification (and largest relative declines in NPP and EP) also show the largest positive biases in stratification for the contemporary period, suggesting overestimation of climate change impacts on NPP and EP. All of the CMIP5 models show an increase in stratification in response to surface-ocean warming and freshening, which is accompanied by decreases in surface nutrients, NPP and EP. There is considerable variability across the models in the magnitudes of NPP, EP, surface nutrient concentrations and their perturbations by climate change. The negative response of NPP and EP to increasing stratification reflects primarily a bottom-up control, as upward nutrient flux declines at the global scale. Models with dynamic phytoplankton community structure show larger declines in EP than in NPP. This pattern is driven by phytoplankton community composition shifts, with reductions in productivity by large phytoplankton as smaller phytoplankton (which export less efficiently) are favored under the increasing nutrient stress. Thus, the projections of the NPP response to climate change are critically dependent on the simulated phytoplankton community structure, the efficiency of the biological pump and the resulting levels of regenerated production, which vary widely across the models. Community structure is represented simply in the CMIP5 models, and should be expanded to better capture the spatial patterns and climate-driven changes in export

  8. Living in the twilight: estimating net phytoplankton growth in the Westerschelde estuary (The Netherlands) by means of an ecosystem model (MOSES)

    OpenAIRE

    Soetaert, K.; Herman, P.M.J.; Kromkamp, J

    1994-01-01

    Net phytoplankton productivity in the Westerschelde, a relatively deep. highly turbid and eutrophic estuary in the Southwest Netherlands, was examined by means of a 13-compartment dynamic simulation model. The description of the light-Iimited primary production was based on the model of Eilers and Peeters (1988. Ecol. Model., 42, 185-198). This light limitation was parameterized to the different model compartments by integrating the Eilers-Peeters model over a day and over depth taking into a...

  9. The measurement and modelling of light scattering by phytoplankton cells at narrow forward angles

    Science.gov (United States)

    MacCallum, Iain; Cunningham, Alex; McKee, David

    2004-07-01

    A procedure has been devised for measuring the angular dependence of light scattering from suspensions of phytoplankton cells at forward angles from 0.25° to 8°. The cells were illuminated with a spatially-filtered laser beam and the angular distribution of scattered light measured by tracking a photodetector across the Fourier plane of a collecting lens using a stepper-motor driven stage. The procedure was calibrated by measuring scattering from latex bead suspensions with known size distributions. It was then used to examine the scattering from cultures of the unicellular algae Isochrysis galbana (4 µm × 5 µm), Dunaliella primolecta (6 µm × 7 µm) and Rhinomonas reticulata (5 µm × 11 µm). The results were compared with the predictions of Mie theory. Excellent agreement was obtained for spherical particles. A suitable choice of spherical-equivalent scattering parameters was required to enable reasonable agreement within the first diffraction lobe for ellipsoidal particles.

  10. Antarctic Entomology.

    Science.gov (United States)

    Chown, Steven L; Convey, Peter

    2016-01-01

    The Antarctic region comprises the continent, the Maritime Antarctic, the sub-Antarctic islands, and the southern cold temperate islands. Continental Antarctica is devoid of insects, but elsewhere diversity varies from 2 to more than 200 species, of which flies and beetles constitute the majority. Much is known about the drivers of this diversity at local and regional scales; current climate and glacial history play important roles. Investigations of responses to low temperatures, dry conditions, and varying salinity have spanned the ecological to the genomic, revealing new insights into how insects respond to stressful conditions. Biological invasions are common across much of the region and are expected to increase as climates become warmer. The drivers of invasion are reasonably well understood, although less is known about the impacts of invasion. Antarctic entomology has advanced considerably over the past 50 years, but key areas, such as interspecific interactions, remain underexplored.

  11. Using Hyperspectral Remote Sensing Models to Determine Phytoplankton Density in the Coastal Waters of Long Bay, South Carolina

    Science.gov (United States)

    Harrington, J. E.; Ali, K.

    2013-12-01

    as an index for the estimation of phytoplankton density. Efficiency of the algorithms were evaluated through a least squares regression and residual analysis. Results show that for prediction models of chlorophyll a concentrations, the Oc4v4 by Reilly et al (2000), two -band blue-green empirical algorithm yielded coefficients of determination as high as 0.64 with RMSE=0.29μg/l for an aggregated dataset (n=62, P<0.05). The NIR-red -based two-band algorithm by Dekker et al. (1993) and Gitelson et al. (2000) gave the best chlorophyll a prediction model, with R2 =0.79, RMSE=0.19μg/l. The results illustrate the potential of remote sensing in accounting for the chlorophyll a variability in the turbid waters of Long Bay, SC.

  12. A 3-D model for the Antarctic ice sheet: a sensitivity study on the glacial-interglacial contrast

    OpenAIRE

    Huybrechts, Philippe

    1990-01-01

    On the longer climatic time scales, changes in the elevation and extent of the Antarctic ice sheet have an important role in modulating global atmospheric andoceanographic processes, and contribute significantly to world-wide sea levels. In this paper, a 3-D time-dependent thermomechanical model for the entire icesheet is presented that is subsequently used to examine the effects of glacial-interglacial shifts in environmental boundary conditions on its geometry. Themodel takes into account a...

  13. Distribution of phytoplankton functional types in high-nitrate, low-chlorophyll waters in a new diagnostic ecological indicator model

    Directory of Open Access Journals (Sweden)

    A. P. Palacz

    2013-11-01

    Full Text Available Modeling and monitoring plankton functional types (PFTs is challenged by the insufficient amount of field measurements of ground truths in both plankton models and bio-optical algorithms. In this study, we combine remote sensing data and a dynamic plankton model to simulate an ecologically sound spatial and temporal distribution of phyto-PFTs. We apply an innovative ecological indicator approach to modeling PFTs and focus on resolving the question of diatom–coccolithophore coexistence in the subpolar high-nitrate and low-chlorophyll regions. We choose an artificial neural network as our modeling framework because it has the potential to interpret complex nonlinear interactions governing complex adaptive systems, of which marine ecosystems are a prime example. Using ecological indicators that fulfill the criteria of measurability, sensitivity and specificity, we demonstrate that our diagnostic model correctly interprets some basic ecological rules similar to ones emerging from dynamic models. Our time series highlight a dynamic phyto-PFT community composition in all high-latitude areas and indicate seasonal coexistence of diatoms and coccolithophores. This observation, though consistent with in situ and remote sensing measurements, has so far not been captured by state-of-the-art dynamic models, which struggle to resolve this "paradox of the plankton". We conclude that an ecological indicator approach is useful for ecological modeling of phytoplankton and potentially higher trophic levels. Finally, we speculate that it could serve as a powerful tool in advancing ecosystem-based management of marine resources.

  14. Laurentian Great Lakes phytoplankton and their water quality characteristics, including a diatom-based model for paleoreconstruction of phosphorus.

    Science.gov (United States)

    Reavie, Euan D; Heathcote, Adam J; Shaw Chraïbi, Victoria L

    2014-01-01

    Recent shifts in water quality and food web characteristics driven by anthropogenic impacts on the Laurentian Great Lakes warranted an examination of pelagic primary producers as tracers of environmental change. The distributions of the 263 common phytoplankton taxa were related to water quality variables to determine taxon-specific responses that may be useful in indicator models. A detailed checklist of taxa and their environmental optima are provided. Multivariate analyses indicated a strong relationship between total phosphorus (TP) and patterns in the diatom assemblages across the Great Lakes. Of the 118 common diatom taxa, 90 (76%) had a directional response along the TP gradient. We further evaluated a diatom-based transfer function for TP based on the weighted-average abundance of taxa, assuming unimodal distributions along the TP gradient. The r(2) between observed and inferred TP in the training dataset was 0.79. Substantial spatial and environmental autocorrelation within the training set of samples justified the need for further model validation. A randomization procedure indicated that the actual transfer function consistently performed better than functions based on reshuffled environmental data. Further, TP was minimally confounded by other environmental variables, as indicated by the relatively large amount of unique variance in the diatoms explained by TP. We demonstrated the effectiveness of the transfer function by hindcasting TP concentrations using fossil diatom assemblages in a Lake Superior sediment core. Passive, multivariate analysis of the fossil samples against the training set indicated that phosphorus was a strong determinant of historical diatom assemblages, verifying that the transfer function was suited to reconstruct past TP in Lake Superior. Collectively, these results showed that phytoplankton coefficients for water quality can be robust indicators of Great Lakes pelagic condition. The diatom-based transfer function can be used in

  15. Spatial patterns of Antarctic surface temperature trends in the context of natural variability: Lessons from the CMIP5 Models

    Science.gov (United States)

    Smith, K. L.; Polvani, L. M.

    2015-12-01

    The recent annually averaged warming of the Antarctic Peninsula, and of West Antarctica, stands in stark contrast to very small and weakly negative trends over East Antarctica. This asymmetry arises primarily from a highly significant warming of West Antarctica in austral spring and a strong cooling of East Antarctic in austral autumn. Here we examine whether this East-West asymmetry is a response to anthropogenic climate forcings or a manifestation of natural climate variability. We compare the observed Antarctic surface air temperature (SAT) trends from five temperature reconstructions over two distinct time periods (1979-2005 and 1960-2005), and with those simulated by 40 coupled models participating in Phase 5 of the Coupled Model Intercomparison Project. We find that the observed East-West asymmetry differs substantially over the two time periods and, furthermore, is completely absent from the CMIP5 multi-model mean (from which all natural variability is eliminated by the averaging). We compare the CMIP5 SAT trends to those of 29 historical atmosphere-only simulations with prescribed sea surface temperatures (SSTs) and sea ice and find that these simulations are in better agreement with the observations. This suggests that natural multi-decadal variability associated with SSTs and sea ice and not external forcings is the primary driver of Antarctic SAT trends. We confirm this by showing that the observed trends lie within the distribution of multi-decadal trends from the CMIP5 pre-industrial integrations. These results, therefore, offer new evidence which points to natural climate variability as the more likely cause of the recent warming of West Antarctica and of the Peninsula.

  16. A glacial systems model configured for large ensemble analysis of Antarctic deglaciation

    Directory of Open Access Journals (Sweden)

    R. Briggs

    2013-04-01

    Full Text Available This article describes the Memorial University of Newfoundland/Penn State University (MUN/PSU glacial systems model (GSM that has been developed specifically for large-ensemble data-constrained analysis of past Antarctic Ice Sheet evolution. Our approach emphasizes the introduction of a large set of model parameters to explicitly account for the uncertainties inherent in the modelling of such a complex system. At the core of the GSM is a 3-D thermo-mechanically coupled ice sheet model that solves both the shallow ice and shallow shelf approximations. This enables the different stress regimes of ice sheet, ice shelves, and ice streams to be represented. The grounding line is modelled through an analytical sub-grid flux parametrization. To this dynamical core the following have been added: a heavily parametrized basal drag component; a visco-elastic isostatic adjustment solver; a diverse set of climate forcings (to remove any reliance on any single method; tidewater and ice shelf calving functionality; and a new physically-motivated empirically-derived sub-shelf melt (SSM component. To assess the accuracy of the latter, we compare predicted SSM values against a compilation of published observations. Within parametric and observational uncertainties, computed SSM for the present day ice sheet is in accord with observations for all but the Filchner ice shelf. The GSM has 31 ensemble parameters that are varied to account (in part for the uncertainty in the ice-physics, the climate forcing, and the ice-ocean interaction. We document the parameters and parametric sensitivity of the model to motivate the choice of ensemble parameters in a quest to approximately bound reality (within the limits of 31 parameters.

  17. Modeling of TOA radiance measured by CERES and SCIAMACHY over the East Antarctic Plateau

    Science.gov (United States)

    Radkevich, A.; Kato, S.; Lukashin, C.

    2015-12-01

    CERES and SCIAMACHY are satellite borne remote sensing instruments measuring solar-reflected and Earth-emitted radiation at the top-of-atmosphere (TOA). CERES instruments are designed to monitor the Earth's radiation budget by measuring radiation in 3 broad bands. SCIAMACHY sensor measured earth reflected radiation in the spectral range 0.24 to 2.38 um with fine spectral and coarse spatial resolutions. In this work we evaluate CERES shortwave (SW) TOA radiance over permanent clear sky snow in the East Antarctic Plateau to test consistency between modeled and observed radiances. We use SCIAMACHY observations to validate spectral performance of our radiative transfer (RT) model. We revisiting the issue reported by Hudson et al (2010) with another radiative transfer model and using instantaneous atmospheric profiles. That paper reported some overestimation of TOA albedo by their model in comparison with CERES observed SW radiances. As pointed out by Hudson et al., that comparison involves some uncertainties including errors in the modeled surface albedo and atmospheric properties. We use RT model based on DISORT coupled with a k-distribution approach (Kato et al 1999). We use the same approach for the lower boundary condition as in Hudson et al. (2010) with a modification related to modeling surface albedo. In this work we create atmospheric profiles for the individual CERES and SCIAMACHY observations from GEOS-4 reanalysis. A comparison between modeling and actual observations was performed for data from the CERES sensors onboard EOS Terra and Aqua, and Suomi-NPP. Similar to the study by Hudson et al. (2010), the model overestimates the TOA radiance. Modeled radiances are greater than observed ones from the CERES Single Satellite Footprint data by 4.6% for FM-1, 2, and FM-4, and by 3.6% for FM-5. Modeled and observed radiance correlates well: coefficient of determination R2 > 0.999. We compare modeled radiances SCIAMACHY radiances by spectrally integrating over the

  18. An Improved Method for Modeling Spatial Distribution of δD in Surface Snow over Antarctic Ice Sheet

    Institute of Scientific and Technical Information of China (English)

    WANG Yetang; HOU Shugui; Bjorn GRIGHOLM; SONG Linlin

    2009-01-01

    Using the recent compilation of the isotopic composition data of surface snow of Antarctic ice sheet, we proposed an improved interpolation method of δD, which utilizes geographical factors (i.e., latitude and altitude) as the primary predictors and incorporates inverse distance weighting (IDW) technique. The method was applied to a high-resolution digital elevation model (DEM) to produce a grid map of multi-year mean δD values with 1km spatial resolution for Antarctic& The mean absolute deviation between observed and estimated data in the map is about 5.4‰, and the standard deviation is 9‰. The resulting δD pattern resembles well known characteristics such as the depletion of the heavy isotopes with increasing latitude and distance from coast line, but also reveals the complex topographic effects.

  19. Modelling acoustic propagation beneath Antarctic sea ice using measured environmental parameters

    Science.gov (United States)

    Alexander, Polly; Duncan, Alec; Bose, Neil; Williams, Guy

    2016-09-01

    Autonomous underwater vehicles are improving and expanding in situ observations of sea ice for the validation of satellite remote sensing and climate models. Missions under sea ice, particularly over large distances (up to 100 km) away from the immediate vicinity of a ship or base, require accurate acoustic communication for monitoring, emergency response and some navigation systems. We investigate the propagation of acoustic signals in the Antarctic seasonal ice zone using the BELLHOP model, examining the influence of ocean and sea ice properties. We processed available observations from around Antarctica to generate input variables such as sound speed, surface reflection coefficient (R) and roughness parameters. The results show that changes in the sound speed profile make the most significant difference to the propagation of the direct path signal. The inclusion of the surface reflected signals from a flat ice surface was found to greatly decrease the transmission loss with range. When ice roughness was added, the transmission loss increased with roughness, in a manner similar to the direct path transmission loss results. The conclusions of this work are that: (1) the accuracy of acoustic modelling in this environment is greatly increased by using realistic sound speed data; (2) a risk averse ranging model would use only the direct path signal transmission; and (3) in a flat ice scenario, much greater ranges can be achieved if the surface reflected transmission paths are included. As autonomous missions under sea ice increase in scale and complexity, it will be increasingly important for operational procedures to include effective modelling of acoustic propagation with representative environmental data.

  20. Cascading water underneath Wilkes Land, East Antarctic Ice Sheet, observed using altimetry and digital elevation models

    Directory of Open Access Journals (Sweden)

    T. Flament

    2013-03-01

    Full Text Available We describe a major subglacial lake drainage close to the ice divide in Wilkes Land, East Antarctica, and the subsequent cascading of water underneath the ice sheet toward the coast. To analyze the event, we combined altimetry data from several sources and bedrock data. We estimated the total volume of water that drained from Lake CookE2 by differencing digital elevation models (DEM derived from ASTER and SPOT5 stereo-imagery. With 5.2 ± 0.5 km3, this is the largest single subglacial drainage event reported so far in Antarctica. Elevation differences between ICESat laser altimetry and the SPOT5 DEM indicate that the discharge lasted approximately 2 yr. A 13-m uplift of the surface, corresponding to a refilling of about 0.64 ± 0.32 km3, was observed between the end of the discharge in October 2008 and February 2012. Using Envisat radar altimetry, with its high 35-day temporal resolution, we monitored the subsequent filling and drainage of connected subglacial lakes located downstream. In particular, a transient temporal signal can be detected within the theoretical 500-km long flow paths computed with the BEDMAP2 data set. The volume of water traveling in this wave is in agreement with the volume that drained from Lake CookE2. These observations contribute to a better understanding of the water transport beneath the East Antarctic ice sheet.

  1. Modeling brine and nutrient dynamics in Antarctic sea ice: The case of dissolved silica

    Science.gov (United States)

    Vancoppenolle, Martin; Goosse, Hugues; de Montety, Anne; Fichefet, Thierry; Tremblay, Bruno; Tison, Jean-Louis

    2010-02-01

    Sea ice ecosystems are characterized by microalgae living in brine inclusions. The growth rate of ice algae depends on light and nutrient supply. Here, the interactions between nutrients and brine dynamics under the influence of algae are investigated using a one-dimensional model. The model includes snow and ice thermodynamics with brine physics and an idealized sea ice biological component, characterized by one nutrient, namely, dissolved silica (DSi). In the model, DSi follows brine motion and is consumed by ice algae. Depending on physical ice characteristics, the brine flow is either advective, diffusive, or turbulent. The vertical profiles of ice salinity and DSi concentration are solutions of advection-diffusion equations. The model is configured to simulate the typical thermodynamic regimes of first-year Antarctic pack ice. The simulated vertical profiles of salinity and DSi qualitatively reproduce observations. Analysis of results highlights the role of convection in the lowermost 5-10 cm of ice. Convection mixes saline, nutrient-poor brine with comparatively fresh, nutrient-rich seawater. This implies a rejection of salt to the ocean and a flux of DSi to the ice. In the presence of growing algae, the simulated ocean-to-ice DSi flux increases by 0-115% compared to an abiotic situation. In turn, primary production and brine convection act in synergy to form a nutrient pump. The other important processes are the flooding of the surface by seawater and the percolation of meltwater. The former refills nutrients near the ice surface in spring. The latter, if present, tends to expell nutrients from the ice in summer.

  2. Implications of seasonal mixing for phytoplankton production and bloom development

    OpenAIRE

    Peeters, Frank; Kerimoglu, Onur; Straile, Dietmar

    2012-01-01

    Based on a 1-dimensional model considering phytoplankton and nutrients in a vertical water column, we investigate the consequences of temporal and spatial variations in turbulent mixing for phytoplankton production and biomass. We show that in seasonally mixed systems the processes controlling phytoplankton production and the sensitivity of phytoplankton abundance to ambient light, trophic state and mixed layer depth differ substantially from those at steady state in systems with time-constan...

  3. Development of an Antarctic digital elevation model by integrating cartographic and remotely sensed data: A geographic information system based approach

    Science.gov (United States)

    Liu, Hongxing; Jezek, Kenneth C.; Li, Biyan

    1999-10-01

    We present a high-resolution digital elevation model (DEM) of the Antarctic. It was created in a geographic information system (GIS) environment by integrating the best available topographic data from a variety of sources. Extensive GIS-based error detection and correction operations ensured that our DEM is free of gross errors. The carefully designed interpolation algorithms for different types of source data and incorporation of surface morphologic information preserved and enhanced the fine surface structures present in the source data. The effective control of adverse edge effects and the use of the Hermite blending weight function in data merging minimized the discontinuities between different types of data, leading to a seamless and topographically consistent DEM throughout the Antarctic. This new DEM provides exceptional topographical details and represents a substantial improvement in horizontal resolution and vertical accuracy over the earlier, continental-scale renditions, particularly in mountainous and coastal regions. It has a horizontal resolution of 200 m over the rugged mountains, 400 m in the coastal regions, and approximately 5 km in the interior. The vertical accuracy of the DEM is estimated at about 100-130 m over the rugged mountainous area, better than 2 m for the ice shelves, better than 15 m for the interior ice sheet, and about 35 m for the steeper ice sheet perimeter. The Antarctic DEM can be obtained from the authors.

  4. The impact of tourists on Antarctic tardigrades: an ordination-based model

    Directory of Open Access Journals (Sweden)

    Sandra J. McInnes

    2013-05-01

    Full Text Available Tardigrades are important members of the Antarctic biota yet little is known about their role in the soil fauna or whether they are affected by anthropogenic factors. The German Federal Environment Agency commissioned research to assess the impact of human activities on soil meiofauna at 14 localities along the Antarctic peninsula during the 2009/2010 and 2010/2011 austral summers. We used ordination techniques to re-assess the block-sampling design used to compare areas of high and low human impact, to identify which of the sampled variables were biologically relevant and/or demonstrated an anthropogenic significance. We found the most significant differences between locations, reflecting local habitat and vegetation factor, rather than within-location anthropogenic impact. We noted no evidence of exotic imports but report on new maritime Antarctic sample sites and habitats.

  5. Response of the Antarctic ice sheet to ocean forcing using the POPSICLES coupled ice sheet-ocean model

    Science.gov (United States)

    Martin, D. F.; Asay-Davis, X.; Price, S. F.; Cornford, S. L.; Maltrud, M. E.; Ng, E. G.; Collins, W.

    2014-12-01

    We present the response of the continental Antarctic ice sheet to sub-shelf-melt forcing derived from POPSICLES simulation results covering the full Antarctic Ice Sheet and the Southern Ocean spanning the period 1990 to 2010. Simulations are performed at 0.1 degree (~5 km) ocean resolution and ice sheet resolution as fine as 500 m using adaptive mesh refinement. A comparison of fully-coupled and comparable standalone ice-sheet model results demonstrates the importance of two-way coupling between the ice sheet and the ocean. The POPSICLES model couples the POP2x ocean model, a modified version of the Parallel Ocean Program (Smith and Gent, 2002), and the BISICLES ice-sheet model (Cornford et al., 2012). BISICLES makes use of adaptive mesh refinement to fully resolve dynamically-important regions like grounding lines and employs a momentum balance similar to the vertically-integrated formulation of Schoof and Hindmarsh (2009). Results of BISICLES simulations have compared favorably to comparable simulations with a Stokes momentum balance in both idealized tests like MISMIP3D (Pattyn et al., 2013) and realistic configurations (Favier et al. 2014). POP2x includes sub-ice-shelf circulation using partial top cells (Losch, 2008) and boundary layer physics following Holland and Jenkins (1999), Jenkins (2001), and Jenkins et al. (2010). Standalone POP2x output compares well with standard ice-ocean test cases (e.g., ISOMIP; Losch, 2008) and other continental-scale simulations and melt-rate observations (Kimura et al., 2013; Rignot et al., 2013). A companion presentation, "Present-day circum-Antarctic simulations using the POPSICLES coupled land ice-ocean model" in session C027 describes the ocean-model perspective of this work, while we focus on the response of the ice sheet and on details of the model. The figure shows the BISICLES-computed vertically-integrated ice velocity field about 1 month into a 20-year coupled Antarctic run. Groundling lines are shown in green.

  6. An evaluation of the simulation of the edge of the Antarctic vortex by chemistry-climate models

    Directory of Open Access Journals (Sweden)

    H. Struthers

    2008-12-01

    Full Text Available The dynamical barrier to meridional mixing at the edge of the Antarctic spring stratospheric vortex is examined. Diagnostics are presented which demonstrate the link between the shape of the meridional mixing barrier at the edge of the vortex and the meridional gradients in total column ozone across the vortex edge. Results derived from reanalysis and measurement data sets are compared with equivalent diagnostics from five coupled chemistry-climate models to test how well the models capture the interaction between the dynamical structure of the stratospheric vortex and the chemical processes occurring within the vortex. Results show that the accuracy of the simulation of the dynamical vortex edge varies widely amongst the models studied here. This affects the ability of the models to simulate the large observed meridional gradients in total column ozone. Three of the models in this study simulated the inner edge of the vortex to be more than 7° closer to the pole than observed. This is expected to have important implications for how well these models simulate the extent of severe springtime ozone loss that occurs within the Antarctic vortex.

  7. Regulation of phytoplankton carbon to chlorophyll ratio by light, nutrients and temperature in the equatorial Pacific Ocean: a basin-scale model

    Directory of Open Access Journals (Sweden)

    X. J. Wang

    2008-09-01

    Full Text Available The complex effects of light, nutrients and temperature lead to a variable carbon to chlorophyll (C:Chl ratio in phytoplankton cells. Using field data collected in the equatorial Pacific, we derived a new dynamic model with a non-steady C:Chl ratio as a function of irradiance, nitrate, iron, and temperature. The dynamic model is implemented into a basin-scale ocean circulation-biogeochemistry model and tested in the equatorial Pacific Ocean. The model reproduces well the general features of phytoplankton dynamics in this region. For instance, the simulated deep chlorophyll maximum (DCM is much deeper in the western warm pool (~100 m than in the eastern equatorial Pacific (~50 m. The model also shows the ability to reproduce chlorophyll, including not only the zonal, meridional and vertical variations, but also the interannual variability. This study demonstrates that combination of nitrate and iron regulates the spatial and temporal variations in the phytoplankton C:Chl ratio. Particularly, nitrate is responsible for the high C:Chl ratio in the western warm pool while iron is responsible for the frontal features in the C:Chl ratio between the warm pool and the upwelling region. In addition, iron plays a dominant role in regulating the spatial and temporal variations of the C:Chl ratio in the central and eastern equatorial Pacific. While temperature has a relatively small effect on the C:Chl ratio, light is primarily responsible for the vertical decrease of phytoplankton C:Chl ratio in the euphotic zone.

  8. Large ensemble modeling of last deglacial retreat of the West Antarctic Ice Sheet: comparison of simple and advanced statistical techniques

    Directory of Open Access Journals (Sweden)

    D. Pollard

    2015-11-01

    Full Text Available A 3-D hybrid ice-sheet model is applied to the last deglacial retreat of the West Antarctic Ice Sheet over the last ~ 20 000 years. A large ensemble of 625 model runs is used to calibrate the model to modern and geologic data, including reconstructed grounding lines, relative sea-level records, elevation-age data and uplift rates, with an aggregate score computed for each run that measures overall model-data misfit. Two types of statistical methods are used to analyze the large-ensemble results: simple averaging weighted by the aggregate score, and more advanced Bayesian techniques involving Gaussian process-based emulation and calibration, and Markov chain Monte Carlo. Results for best-fit parameter ranges and envelopes of equivalent sea-level rise with the simple averaging method agree quite well with the more advanced techniques, but only for a large ensemble with full factorial parameter sampling. Best-fit parameter ranges confirm earlier values expected from prior model tuning, including large basal sliding coefficients on modern ocean beds. Each run is extended 5000 years into the "future" with idealized ramped climate warming. In the majority of runs with reasonable scores, this produces grounding-line retreat deep into the West Antarctic interior, and the analysis provides sea-level-rise envelopes with well defined parametric uncertainty bounds.

  9. Large ensemble modeling of last deglacial retreat of the West Antarctic Ice Sheet: comparison of simple and advanced statistical techniques

    Science.gov (United States)

    Pollard, D.; Chang, W.; Haran, M.; Applegate, P.; DeConto, R.

    2015-11-01

    A 3-D hybrid ice-sheet model is applied to the last deglacial retreat of the West Antarctic Ice Sheet over the last ~ 20 000 years. A large ensemble of 625 model runs is used to calibrate the model to modern and geologic data, including reconstructed grounding lines, relative sea-level records, elevation-age data and uplift rates, with an aggregate score computed for each run that measures overall model-data misfit. Two types of statistical methods are used to analyze the large-ensemble results: simple averaging weighted by the aggregate score, and more advanced Bayesian techniques involving Gaussian process-based emulation and calibration, and Markov chain Monte Carlo. Results for best-fit parameter ranges and envelopes of equivalent sea-level rise with the simple averaging method agree quite well with the more advanced techniques, but only for a large ensemble with full factorial parameter sampling. Best-fit parameter ranges confirm earlier values expected from prior model tuning, including large basal sliding coefficients on modern ocean beds. Each run is extended 5000 years into the "future" with idealized ramped climate warming. In the majority of runs with reasonable scores, this produces grounding-line retreat deep into the West Antarctic interior, and the analysis provides sea-level-rise envelopes with well defined parametric uncertainty bounds.

  10. Biochemical composition of Antarctic zooplankton from the Indian Ocean sector

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Parulekar, A.H.

    variations and ranged between 8.02 and 29.9% (x = 19.57 + or - 6.25). Values for carbohydrate content varied from 11.01 to 27.65% (x = 19.62 + or - 4.80). Higher accumulation of lipids in Antarctic zooplankton during phytoplankton blooms (austral summer...

  11. Climate Variability and Phytoplankton in the Pacific Ocean

    Science.gov (United States)

    Rousseaux, Cecile

    2012-01-01

    The effect of climate variability on phytoplankton communities was assessed for the tropical and sub-tropical Pacific Ocean between 1998 and 2005 using an established biogeochemical assimilation model. The phytoplankton communities exhibited wide range of responses to climate variability, from radical shifts in the Equatorial Pacific, to changes of only a couple of phytoplankton groups in the North Central Pacific, to no significant changes in the South Pacific. In the Equatorial Pacific, climate variability dominated the variability of phytoplankton. Here, nitrate, chlorophyll and all but one of the 4 phytoplankton types (diatoms, cyanobacteria and coccolithophores) were strongly correlated (pclimate variability can play in ocean biology.

  12. A new 100-m Digital Elevation Model of the Antarctic Peninsula derived from ASTER Global DEM: methods and accuracy assessment

    Directory of Open Access Journals (Sweden)

    A. J. Cook

    2012-10-01

    Full Text Available A high resolution surface topography Digital Elevation Model (DEM is required to underpin studies of the complex glacier system on the Antarctic Peninsula. A complete DEM with better than 200 m pixel size and high positional and vertical accuracy would enable mapping of all significant glacial basins and provide a dataset for glacier morphology analyses. No currently available DEM meets these specifications. We present a new 100-m DEM of the Antarctic Peninsula (63–70° S, based on ASTER Global Digital Elevation Model (GDEM data. The raw GDEM products are of high-quality on the rugged terrain and coastal-regions of the Antarctic Peninsula and have good geospatial accuracy, but they also contain large errors on ice-covered terrain and we seek to minimise these artefacts. Conventional data correction techniques do not work so we have developed a method that significantly improves the dataset, smoothing the erroneous regions and hence creating a DEM with a pixel size of 100 m that will be suitable for many glaciological applications. We evaluate the new DEM using ICESat-derived elevations, and perform horizontal and vertical accuracy assessments based on GPS positions, SPOT-5 DEMs and the Landsat Image Mosaic of Antarctica (LIMA imagery. The new DEM has a mean elevation difference of −4 m (± 25 m RMSE from ICESat (compared to −13 m mean and ±97 m RMSE for the original ASTER GDEM, and a horizontal error of less than 2 pixels, although elevation accuracies are lower on mountain peaks and steep-sided slopes. The correction method significantly reduces errors on low relief slopes and therefore the DEM can be regarded as suitable for topographical studies such as measuring the geometry and ice flow properties of glaciers on the Antarctic Peninsula. The DEM is available for download from the NSIDC website: http://nsidc.org/data/nsidc-0516.html (The Thermodynamic Flow-Force Interpretation of Root Nutrient Uptake Kinetics: A Powerful Formalism for Agronomic and Phytoplanktonic Models

    Science.gov (United States)

    Le Deunff, Erwan; Tournier, Pierre-Henri; Malagoli, Philippe

    2016-01-01

    The ion influx isotherms obtained by measuring unidirectional influx across root membranes with radioactive or stable tracers are mostly interpreted by enzyme-substrate-like modeling. However, recent analyses from ion transporter mutants clearly demonstrate the inadequacy of the conventional interpretation of ion isotherms. Many genetically distinct carriers are involved in the root catalytic function. Parameters Vmax and Km deduced from this interpretation cannot therefore be regarded as microscopic parameters of a single transporter, but are instead macroscopic parameters (Vmapp and Kmapp, apparent maximum velocity and affinity constant) that depend on weighted activities of multiple transporters along the root. The flow-force interpretation based on the thermodynamic principle of irreversible processes is an alternative macroscopic modeling approach for ion influx isotherms in which macroscopic parameters Lj (overall conductance of the root system for the substrate j) and πj (thermodynamic parameter when Jj = 0) have a straightforward meaning with respect to the biological sample studied. They characterize the efficiency of the entire root catalytic structure without deducing molecular characteristics. Here we present the basic principles of this theory and how its use can be tested and improved by changing root pre- and post-wash procedures before influx measurements in order to come as close as possible to equilibrium conditions. In addition, the constant values of Vm and Km in the Michaelis-Menten (MM) formalism of enzyme-substrate interpretation do not reflect variations in response to temperature, nutrient status or nutrient regimes. The linear formalism of the flow-force approach, which integrates temperature effect on nutrient uptake, could usefully replace MM formalism in the 1-3-dimension models of plants and phytoplankton. This formalism offers a simplification of parametrization to help find more realistic analytical expressions and numerical

  13. Poor correlation between phytoplankton community growth rates and nutrient concentration in the sea

    OpenAIRE

    Regaudie-de-gioux, A.; Sal, S; Á. López-Urrutia

    2015-01-01

    Nutrient availability is one of the major factors regulating marine productivity and phytoplankton community structure. While the response of phytoplankton species to nutrient variation is relatively well known, that of phytoplankton community remains unclear. We question whether phytoplankton community growth rates respond to nutrient concentration in a similar manner to phytoplankton species composing the community, that is, following Monod's model. Data on in situ marine community growth r...

  14. Future surface mass balance of the Antarctic ice sheet and its influence on sea level change, simulated by a regional atmospheric climate model

    NARCIS (Netherlands)

    Ligtenberg, S.R.M.; van de Berg, W.J.; van den Broeke, M.R.; Rae, J.G.L.; van Meijgaard, E.

    2013-01-01

    A regional atmospheric climate model with multi-layer snow module (RACMO2) is forced at the lateral boundaries by global climate model (GCM) data to assess the future climate and surface mass balance (SMB) of the Antarctic ice sheet (AIS). Two different GCMs (ECHAM5 until 2100 and HadCM3 until 2200)

  15. 21st Century Trends in Antarctic Temperature and Polar Stratospheric Cloud (PSC) Area in the GEOS Chemistry-Climate Model

    Science.gov (United States)

    Hurwitz, M. M.; Newman, P. A.

    2010-01-01

    This study examines trends in Antarctic temperature and APSC, a temperature proxy for the area of polar stratospheric clouds, in an ensemble of Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) simulations of the 21st century. A selection of greenhouse gas, ozone-depleting substance, and sea surface temperature scenarios is used to test the trend sensitivity to these parameters. One scenario is used to compare temperature trends in two versions of the GEOS CCM. An extended austral winter season is examined in detail. In May, June, and July, the expected future increase in CO2-related radiative cooling drives temperature trends in the Antarctic lower stratosphere. At 50 hPa, a 1.3 K cooling is expected between 2000 and 2100. Ozone levels increase, despite this robust cooling signal and the consequent increase in APSC, suggesting the enhancement of stratospheric transport in future. In the lower stratosphere, the choice of climate change scenarios does not affect the magnitude of the early winter cooling. Midwinter temperature trends are generally small. In October, APSC trends have the same sign as the prescribed halogen trends. That is, there are negative APSC trends in "grealistic future" simulations, where halogen loading decreases in accordance with the Montreal Protocol and CO2 continues to increase. In these simulations, the speed of ozone recovery is not influenced by either the choice of sea surface temperature and greenhouse gas scenarios or by the model version.

  16. An inversion model based on salinity and remote sensing reflectance for estimating the phytoplankton absorption coefficient in the Saint Lawrence Estuary

    Science.gov (United States)

    Montes-Hugo, Martin; Xie, Huxiang

    2015-10-01

    The inversion of individual inherent optical properties (IOPs) is very challenging in optically complex waters and within the violet spectral range (i.e., 380-450 nm) due to the strong light attenuation caused by chromophoric dissolved organic matter, nonalgal particulates, and phytoplankton. Here we present a technique to better discriminate light absorption contributions due to phytoplankton based on a hybrid model (QAA-hybrid) that combines regional Saint Lawrence System estimates of IOPs derived from a quasi-analytical algorithm (hereafter QAA-SLE) and empirical relationships between salinity and IOPs. Preliminary results in the Saint Lawrence System during May 2000 and April 2001 showed that QAA-hybrid estimates of phytoplankton absorption coefficient at 443 nm have a smaller bias with respect to in situ measurements (root-mean-square deviation, RMSD = 0.156) than those derived from QAA-SLE (RMSD = 0.341). These results were valid for surface waters (i.e., 0-5 m depth) of the lower estuary with a salinity and chlorophyll-a concentration range of 22-28 psu and 2.1-13.8 mg m-3, respectively.

  17. Why marine phytoplankton calcify.

    Science.gov (United States)

    Monteiro, Fanny M; Bach, Lennart T; Brownlee, Colin; Bown, Paul; Rickaby, Rosalind E M; Poulton, Alex J; Tyrrell, Toby; Beaufort, Luc; Dutkiewicz, Stephanie; Gibbs, Samantha; Gutowska, Magdalena A; Lee, Renee; Riebesell, Ulf; Young, Jeremy; Ridgwell, Andy

    2016-07-01

    Calcifying marine phytoplankton-coccolithophores- are some of the most successful yet enigmatic organisms in the ocean and are at risk from global change. To better understand how they will be affected, we need to know "why" coccolithophores calcify. We review coccolithophorid evolutionary history and cell biology as well as insights from recent experiments to provide a critical assessment of the costs and benefits of calcification. We conclude that calcification has high energy demands and that coccolithophores might have calcified initially to reduce grazing pressure but that additional benefits such as protection from photodamage and viral/bacterial attack further explain their high diversity and broad spectrum ecology. The cost-benefit aspect of these traits is illustrated by novel ecosystem modeling, although conclusive observations remain limited. In the future ocean, the trade-off between changing ecological and physiological costs of calcification and their benefits will ultimately decide how this important group is affected by ocean acidification and global warming. PMID:27453937

  18. Sea Soup: Phytoplankton.

    Science.gov (United States)

    Cerullo, Mary M.

    This guide, designed for students in grades 3-7, answers intriguing questions about phytoplankton, tiny drifters that have shaped our world. Invisible to the naked eye, phytoplankton are the source of our atmosphere, our climate, our ocean food chain, much of our oil supply, and more. They're also food for zooplankton. Photomicroscopy serves up…

  19. Modeling Distribution and Abundance of Antarctic Baleen Whales Using Ships of Opportunity

    Directory of Open Access Journals (Sweden)

    Philip S. Hammond

    2006-06-01

    Full Text Available Information on animal abundance and distribution is at the cornerstone of many wildlife and conservation strategies. However, these data can be difficult and costly to obtain for cetacean species. The expense of sufficient ship time to conduct design-unbiased line transect surveys may be simply out of reach for researchers in many countries, which nonetheless grapple with problems of conservation of endangered species, by-catch of small cetaceans in commercial fisheries, and progression toward ecosystem-based fisheries management. Recently developed spatial modeling techniques show promise for estimating wildlife abundance using non-randomized surveys, but have yet to receive much field-testing in areas where designed surveys have also been conducted. Effort and sightings data were collected along 9 650 km of transects aboard ships of opportunity in the Southern Ocean during the austral summers of 2000–2001 and 2001–2002. Generalized additive models with generalized cross-validation were used to express heterogeneity of cetacean sightings as functions of spatial covariates. Models were used to map predicted densities and to estimate abundance of humpback, minke, and fin whales in the Drake Passage and along the Antarctic Peninsula. All species’ distribution maps showed strong density gradients, which were robust to jackknife resampling when each of 14 trips was removed sequentially with replacement. Looped animations of model predictions of whale density illustrate uncertainty in distribution estimates in a way that is informative to non-scientists. The best abundance estimate for humpback whales was 1 829 (95% CI: 978-3 422. Abundance of fin whales was 4 487 (95% CI: 1 326–15 179 and minke whales was 1,544 (95% CI: 1,221–1,953. These estimates agreed roughly with those reported from a designed survey conducted in the region during the previous austral summer. These estimates assumed that all animals on the trackline were

  1. Integrating three lake models into a Phytoplankton Prediction System for Lake Taihu (Taihu PPS) with Python

    NARCIS (Netherlands)

    Huang, J.; Gao, J.; Hörmann, G.; Mooij, W.M.

    2012-01-01

    In the past decade, much work has been done on integrating different lake models using general frameworks to overcome model incompatibilities. However, a framework may not be flexible enough to support applications in different fields. To overcome this problem, we used Python to integrate three lake

  2. Influence of cross-shelf water transport on nutrients and phytoplankton in the East China Sea: a model study

    Directory of Open Access Journals (Sweden)

    L. Zhao

    2011-01-01

    Full Text Available A three dimensional coupled biophysical model was used to examine the supply of oceanic nutrients to the shelf of the East China Sea (ECS and its role in primary production over the shelf. The model consisted of two parts: the hydrodynamic module was based on a nested model with a horizontal resolution of 1/18 degree, whereas the biological module was a lower trophic level ecosystem model including two types of phytoplankton, three elements of nutrients, and biogenic organic material. The model results suggested that seasonal variations occurred in the distribution of nutrients and chlorophyll a over the shelf of the ECS. After comparison with available observed nutrients and chlorophyll a data, the model results were used to calculate volume and nutrients fluxes across the shelf break. The annual mean total fluxes were 1.53 Sv for volume, 9.4 kmol s−1 for DIN, 0.7 kmol s−1 for DIP, and 18.2 kmol s−1 for silicate. Two areas, northeast of Taiwan and southwest of Kyushu, were found to be major source regions of oceanic nutrients to the shelf. Although the onshore fluxes of nutrients and volume both had apparent seasonal variations, the seasonal variation of the onshore nutrient flux did not exactly follow that of the onshore volume flux. Additional calculations in which the concentration of nutrients in Kuroshio water was artificially increased suggested that the oceanic nutrients were distributed in the bottom layer from the shelf break to the region offshore of the Changjiang estuary from spring to summer and appeared in the surface layer from autumn to winter. The calculations also implied that the supply of oceanic nutrients to the shelf can change the consumption of pre-existing nutrients from rivers. The response of primary production over the shelf to the oceanic nutrients was confirmed not only in the surface layer (mainly at the outer shelf and shelf break in winter and in the region

  3. Influence of cross-shelf water transport on nutrients and phytoplankton in the East China Sea: a model study

    Directory of Open Access Journals (Sweden)

    L. Zhao

    2010-07-01

    Full Text Available A three dimensional coupled biophysical model was used to examine the supply of oceanic nutrients to the shelf of the East China Sea (ECS and its role in primary production over the shelf. The model consisted of two modules: the hydrodynamic module was based on a nested model with a horizontal resolution of 1/18 degree, whereas the biological module was a low trophic level ecosystem model including two types of phytoplankton, three elements of nutrients, and biogenic organic material. Model results suggested that seasonal variation in chlorophyll-a had a strong regional dependence over the shelf of the ECS. The area with high chlorophyll-a appears firstly at the outer shelf in winter, and gradually migrates toward the inner shelf (offshore region of Changjiang estuary from spring to summer. Vertically, chlorophyll-a was generally homogenous from the coastal zone to the inner shelf. In the middle and outer shelves, high chlorophyll-a appeared in the surface in spring but moved to the subsurface from summer to early autumn. The annual averaged onshore flux across the shelf break was estimated to be 1.53 Sv for volume, 9.4 kmol s−1 for DIN, 0.7 kmol s−1 for DIP, and 18.2 kmol s−1 for silicate, which are supplied mainly from the northeast of Taiwan and southwest of Kyushu. From calculations that artificially increased the concentration of nutrients in the Kuroshio water, the additional oceanic nutrients were distributed in the bottom layer from the shelf break to the region offshore of Changjiang estuary from spring to summer, and appeared in the surface layer from autumn to winter. The contribution of oceanic nutrients to primary production over the shelf was found not only in the surface layer (mainly at the outer shelf and shelf break in winter and in the region offshore of Changjiang estuary in summer but also in the subsurface layer over the shelf from spring to autumn.

  4. Model study on Bohai ecosystem 2. Annual cycle of nutrient-phytoplankton dynamics

    Institute of Scientific and Technical Information of China (English)

    LIU Hao; YIN Baoshu

    2006-01-01

    Using the coupled bio-physical model described in the first paper of this series of studies, the annual variations of algae biomass and nutrient concentration in the Bohai Sea are simulated. Modeled results show that the onset of spring bloom is induced by high nutrient stocks stored in winter, though the initial time is earlier in shallow waters than in deep waters, for which the evolution of the vertical stratification in deep waters plays an important role; on the other hand, newly added river-borne nutrients and resuspending sediment-borne nutrients are responsible for the outburst of autumn blooms. On the basis of modeled results, it is also found that the BS ecosystem, as a whole, is limited by nitrogen all the year round, though the phosphorus limitation is apparent in the Laizhou Bay where the ratio of nitrogen concentration to phosphorus concentration is higher than 16 due to the contribution of newly added nutrient species from Huanghe River discharges.

  5. Biomixing generated by benthic filterfeeders: A diffusion model for near-bottom phytoplankton depletion

    DEFF Research Database (Denmark)

    Scheel Larsen, Poul; Riisgård, H.U.

    1997-01-01

    polychaete Nereis diversicolor and the ascidian Ciona intestinalis, respectively. The model is based on sinks located at inhalant openings and Fick's law with an effective diffusivity that decreases with distance above the bottom due to the biomixing generated by exhalant and inhalant feeding currents. For N...

  6. Nutrient regimes control phytoplankton ecophysiology in the South Atlantic

    Directory of Open Access Journals (Sweden)

    T. J. Browning

    2013-07-01

    Full Text Available Fast Repetition Rate fluorometry (FRRf measurements of phytoplankton photophysiology from an across-basin South Atlantic cruise (as part of the GEOTRACES programme characterized two dominant ecophysiological regimes which were interpreted on the basis of nutrient limitation. South of the South Subtropical Convergence (SSTC in the northern sub-Antarctic sector of the Antarctic Circumpolar Current (ACC in the Eastern Atlantic Basin, waters are characterized by elevated chlorophyll concentrations, a dominance by larger phytoplankton cells, and low apparent photochemical efficiency (Fv / Fm. Shipboard 24 h iron (Fe addition incubation experiments confirmed that Fe stress was primarily responsible for the low Fv / Fm, with Fe addition to these waters, either within the artificial bottle additions or naturally occurring downstream enrichment from Gough Island, significantly increasing Fv / Fm values. Satellite images suggest a broader region of enhanced chlorophyll concentrations around the SSTC in the Western Atlantic relative to the Eastern Atlantic: hypothesized to be a result of higher iron supply from the South American continent. To the north of the SSTC at the southern boundary of the South Atlantic Gyre, phytoplankton are characterized by high values of Fv / Fm which, coupled with the low macronutrient concentrations and increased presence of picocyanobacteria, are interpreted as conditions of Fe replete, balanced macronutrient-limited growth. Spatial correlation was found between Fv / Fm and Fe:nitrate ratios, supporting the suggestion that the relative supply ratios of these two nutrients can control patterns of limitation and consequently the ecophysiology of phytoplankton in subtropical gyre and ACC regimes.

  7. Phytoplankton niche generation by interspecific stoichiometric variation

    Science.gov (United States)

    GöThlich, L.; Oschlies, A.

    2012-06-01

    For marine biogeochemical models used in simulations of climate change scenarios, the ability to account for adaptability of marine ecosystems to environmental change becomes a concern. The potential for adaptation is expected to be larger for a diverse ecosystem compared to a monoculture of a single type of (model) algae, such as typically included in biogeochemical models. Recent attempts to simulate phytoplankton diversity in global marine ecosystem models display remarkable qualitative agreement with observed patterns of species distributions. However, modeled species diversity tends to be systematically lower than observed and, in many regions, is smaller than the number of potentially limiting nutrients. According to resource competition theory, the maximum number of coexisting species at equilibrium equals the number of limiting resources. By simulating phytoplankton communities in a chemostat model and in a global circulation model, we show here that a systematic underestimate of phytoplankton diversity may result from the standard modeling assumption of identical stoichiometry for the different phytoplankton types. Implementing stoichiometric variation among the different marine algae types in the models allows species to generate different resource supply niches via their own ecological impact. This is shown to increase the level of phytoplankton coexistence both in a chemostat model and in a global self-assembling ecosystem model.

  8. Satellite-detected fluorescence reveals global physiology of ocean phytoplankton

    Directory of Open Access Journals (Sweden)

    M. J. Behrenfeld

    2008-11-01

    Full Text Available Phytoplankton photosynthesis links global ocean biology and climate-driven fluctuations in the physical environment. These interactions are largely expressed through changes in phytoplankton physiology, but physiological status has proven extremely challenging to characterize globally. Phytoplankton fluorescence does provide a rich source of physiological information long exploited in laboratory and field studies, and is now observed from space. Here we use satellite-based fluorescence measurements to evaluate light-absorption and energy-dissipation processes influencing phytoplankton light use efficiency and demonstrate its utility as a global physiological indicator of iron-limited growth conditions. This new tool provides a path for monitoring climate-phytoplankton physiology interactions, improving descriptions of light use efficiency in ocean productivity models, evaluating nutrient-stress predictions in ocean ecosystem models, and appraising phytoplankton responses to natural iron enrichments or purposeful iron fertilizations activities.

  9. Phytoplankton Monitoring Network (PMN)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Phytoplankton Monitoring Network (PMN) is a part of the National Centers for Coastal Ocean Science (NCCOS). The PMN was created as an outreach program to...

  10. Towards a tipping point? Exploring the capacity to self-regulate Antarctic tourism using agent-based modelling

    NARCIS (Netherlands)

    Student, J.R.; Amelung, B.; Lamers, M.A.J.

    2016-01-01

    Antarctica attracts tourists who want to explore its unique nature and landscapes. Antarctic tourism has rapidly grown since 1991 and is currently picking up again after the recent global economic downturn. Tourism activities are subject to the rules of the Antarctic Treaty System (ATS) and the deci

  11. Generalised additive models to investigate environmental drivers of Antarctic minke whale (Balaenoptera bonaerensis) spatial density in austral summer

    NARCIS (Netherlands)

    Beekmans, B.W.P.M.; Forcada, J.; Murphy, E.J.; Baar, H.J.W.; Bathmann, U.V.; Fleming, A.H.

    2010-01-01

    There is a need to characterise the physical environment associated with Antarctic minke whale density in order to understand long-term changes in minke whale distribution and density in open waters of the Southern Ocean during austral summer months. To investigate environmental drivers of Antarctic

  12. Phytoplankton of Lake Kivu

    OpenAIRE

    Sarmento, Hugo; Darchambeau, François; Descy, Jean-Pierre

    2012-01-01

    This chapter reviews taxonomic composition, biomass, production and nutrient limitation of the phytoplankton of Lake Kivu. Present Lake Kivu phytoplankton is dominated by cyanobacteria – mainly Synechococcus spp. and thin filaments of Planktolyngbya limnetica – and by pennate diatoms, among which Nitzschia bacata and Fragilaria danica are dominant. Seasonal shifts occur, with cyanobacteria developing more in the rainy season, and the diatoms in the dry season. Other groups present are cryptop...

  13. Phytoplankton Identification Manual

    Digital Repository Service at National Institute of Oceanography (India)

    Verlecar, X.N.; Desai, S.R.

    counts 9.3 Cell count by drop count method 10. Measurement of productivity 11. Bibliography 1 1. Introduction Phytoplankton (?phyto? = plant; ?planktos? = made to wander) are single celled marine algae, some of which are capable of movement through... of Environment & Forests, New Delhi 3 FOREWORD Since its inception in 1966 the National Institute of Oceanography is involved in taxonomic classification of marine phytoplankton, zooplankton, benthos and other flora and fauna under the Project ? Measurement...

  14. The Role of Phytoplankton Dynamics in the Seasonal and Interannual Variability of Carbon in the Subpolar North Atlantic - a Modeling Study

    Science.gov (United States)

    Signorini, Sergio; Hakkinen, Sirpa; Gudmundsson, K.; Olsen, A.; Omar, A. M.; Olafsson, J.; Reverdin, G.; Henson, S. A.; McClain, C. R.; Worthen, D. L.

    2014-01-01

    We developed an ecosystem/biogeochemical model system, which includes multiple phytoplankton functional groups and carbon cycle dynamics, and applied it to investigate physical-biological interactions in Icelandic waters. Satellite and in situ data were used to evaluate the model. Surface seasonal cycle amplitudes and biases of key parameters (DIC, TA, pCO2, air-sea CO2 flux, and nutrients) are significantly improved when compared to surface observations by prescribing deep water values and trends, based on available data. The seasonality of the coccolithophore and "other phytoplankton" (diatoms and dinoflagellates) blooms is in general agreement with satellite ocean color products. Nutrient supply, biomass and calcite concentrations are modulated by light and mixed layer depth seasonal cycles. Diatoms are the most abundant phytoplankton, with a large bloom in early spring and a secondary bloom in fall. The diatom bloom is followed by blooms of dinoflagellates and coccolithophores. The effect of biological changes on the seasonal variability of the surface ocean pCO2 is nearly twice the temperature effect, in agreement with previous studies. The inclusion of multiple phytoplankton functional groups in the model played a major role in the accurate representation of CO2 uptake by biology. For instance, at the peak of the bloom, the exclusion of coccolithophores causes an increase in alkalinity of up to 4 µmol kg(sup -1) with a corresponding increase in DIC of up to 16 µmol kg(sup -1). During the peak of the bloom in summer, the net effect of the absence of the coccolithophores bloom is an increase in pCO2 of more than 20 µatm and a reduction of atmospheric CO2 uptake of more than 6 mmolm(sup -2) d(sup -1). On average, the impact of coccolithophores is an increase of air-sea CO2 flux of about 27 %. Considering the areal extent of the bloom from satellite images within the Irminger and Icelandic Basins, this reduction translates into an annual mean of nearly 1500

  15. Phytoplankton and Climate

    Science.gov (United States)

    Moisan, John R.

    2009-01-01

    Ocean phytoplankton supply about half of the oxygen that humans utilize to sustain life. In this lecture, we will explore how phytoplankton plays a critical role in modulating the Earth's climate. These tiny organisms are the base of the Ocean's food web. They can modulate the rate at which solar heat is absorbed by the ocean, either through direct absorption or through production of highly scattering cellular coverings. They take up and help sequester carbon dioxide, a key greenhouse gas that modulated the Earth's climate. They are the source of cloud nucleation gases that are key to cloud formation/processes. They are also able to modify the nutrient budgets of the ocean through active uptake of inert atmospheric nitrogen. Climate variations have a pronounced impact on phytoplankton dynamics. Long term variations in the climate have been studied through geological interpretations on its influence on phytoplankton populations. The presentation will focus on presenting the numerous linkages that have been observed between climate and phytoplankton and further discuss how present climate change scenarios are likely to impact phytoplankton populations as well as present findings from several studies that have tried to understand how the climate might react to the feedbacks from these numerous climate-phytop|ankton linkages.

  16. Bacteria, plankton, and trace metal, and other data from bottle and CTD casts in the Antarctic from the NATHANIEL B. PALMER and ROGER REVELL in support of the US Joint Global Ocean Flux Study / Antarctic Environments Southern Ocean Process Study (JGOFS /AESOPS) from 1996-10-17 to 1998-03-15 (NODC Accession 0000504)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Phytoplankton and other data were collected in the Antarctic from the NATHANIEL B. PALMER and ROGER REVELL from 17 October 1996 to 15 March 1998. Bottle data...

  17. Influence of Antarctic Ice Sheet Lowering on the Southern Hemisphere Climate: Model Experiments Mimicking the Mid-Miocene

    Science.gov (United States)

    Justino, Flavio; Stordal, Frode

    2013-04-01

    Conditions in Antarctica have varied substantially in the Earth's climate history. During the early Miocene (23-17 Ma), as suggested by records from the Ocean Drilling Program (ODP) Sites 1090 and 1218, the ice volume was approximately 50%-125% of its present-day values. It has been argued that the rapid Cenozoic glaciation of Antarctica was induced by a decline in atmospheric CO2 from 4 times to 2 times preindustrial atmospheric level over a 10-Myr period. Minor contributions to this glaciation have also been associated with the opening of Southern Ocean gateways between Antarctica and the Australia-Tasmanian Passage, and Antarctica and the South America-Drake Passage, although it has been argued that the total amount of water owing in the Drake passage during the Eocene/Oligocene boundary may have been insufficient for reducing the poleward heat transport. The AIS is responsible for the greater amount of reflected solar radiation in the SH, and has significantly influenced meridional circulation due to its role in the characterization of the latitudinal thermal gradient. Moreover significant interaction between the polar and tropical regions through the link between the ENSO and West Antarctica has been demonstrated. It has been suggested that warming episodes during the Miocene were closely related to small changes in the Southern Ocean's freshwater balance. Paleorecords (ODP Sites 1090 and 1218) have also been utilized to disentangle the nature of deep-sea water mass. The analyses have demonstrated that warmer bottom water coexisted with increased production of Antarctic Bottom Water during the Plio-Pleistocene (1.6Ma) compared to today. We have investigated impacts of changes to the AIS topography on the climate system by using a coupled climate model, an Earth Model of Intermediate Complexity (EMIC), namely Speedy-Ocean (SPEEDO). We have designed experiments to inter-compare the nature of the atmospheric and oceanic circulation under modern conditions and

  18. Population dynamics of light-limited phytoplankton : Microcosm experiments

    NARCIS (Netherlands)

    Huisman, Jef

    1999-01-01

    This paper investigates the extent to which the predictions of an elementary model for light-limited growth are matched by laboratory experiments with light-limited phytoplankton. The model and experiments link the population dynamics of phytoplankton species with changes in the light gradient cause

  19. Modeling the Impact of Snow Drift on the Decameter-Scale Variability of Snow Properties on the Antarctic Plateau

    Science.gov (United States)

    Libois, Q.; Picard, G.; Arnaud, L.; Morin, S.; Brun, E.

    2015-12-01

    On the Antarctic Plateau, the annual snow accumulation and the physical properties of snow close to the surface are characterized by a large spatial variability at the scale of a few metres. As a consequence, two snowpits measured a few metres apart from each other can show significant differences. This variability mainly results from the combination of low annual amounts of precipitation and drift events that redistribute snow. The latter physical process is not simulated by one-dimensional snow evolution models. Here we describe how the detailed snowpack model Crocus is adapted to Antarctic conditions and modified to account for this drift-induced variability using a stochastic snow redistribution scheme. For this, 50 simulations are run in parallel and the corresponding numerical snowpacks are allowed to exchange snow mass according to rules driven by wind speed and snow characteristics. These simple rules were developed and calibrated based on in situ pictures of the snow surface recorded at Dome C for two years, which show the occurrence of snow drift and its impact on snow height variations. At Dome C, the results of these parallel simulations show three substantial improvements with respect to standard Crocus simulations. First, significant and rapid variations of snow height observed in hourly measurements are well reproduced, highlighting the crucial role of snow drift in snow accumulation. Second, the statistics of annual accumulation is successfully simulated, including the years with negative net ablation which are as frequent as 15% in the observations and 11% in the simulation. Eventually, the simulated vertical profiles of snow density and specific surface area down to 50 cm depth are compared to 98 profiles measured at Dome C during the summer 2012-2013. The observed spatial variability is partly reproduced by the new model, especially close to the surface. The erosion/deposition processes also explain why layers with density lower than 250 kg m-3

  20. Observation of different phytoplankton groups and biomass using Differential Optical Absorption Spectroscopy on SCIAMACHY data and comparisons to in-situ, NASA biogeochemical Model and MERIS

    OpenAIRE

    Bracher, Astrid; Taylor, Bettina; M. Vountas; Dinter, Tilman; J. P. Burrows; R. Röttgers; Peeken, Ilka

    2008-01-01

    In order to understand the marine phytoplanktons role in the global marine ecosystem and biogeochemical cycles it is necessary to derive global information on the distribution of major functional phytoplankton types (PFT) in the world oceans. In our study we use instead of the common ocean color sensors such as CZCS, SeaWiFS, MODIS, MERIS, with rather low spectral resolution, the Differential Optical Absorption Spectroscopy (DOAS) to study the retrieval of phytoplankton distribution and absor...

  1. Bivalve grazing can shape phytoplankton communities

    Science.gov (United States)

    Lucas, Lisa; Cloern, James E.; Thompson, Janet K.; Stacey, Mark T.; Koseff, Jeffrey K.

    2016-01-01

    The ability of bivalve filter feeders to limit phytoplankton biomass in shallow waters is well-documented, but the role of bivalves in shaping phytoplankton communities is not. The coupled effect of bivalve grazing at the sediment-water interface and sinking of phytoplankton cells to that bottom filtration zone could influence the relative biomass of sinking (diatoms) and non-sinking phytoplankton. Simulations with a pseudo-2D numerical model showed that benthic filter feeding can interact with sinking to alter diatom:non-diatom ratios. Cases with the smallest proportion of diatom biomass were those with the fastest sinking speeds and strongest bivalve grazing rates. Hydrodynamics modulated the coupled sinking-grazing influence on phytoplankton communities. For example, in simulations with persistent stratification, the non-sinking forms accumulated in the surface layer away from bottom grazers while the sinking forms dropped out of the surface layer toward bottom grazers. Tidal-scale stratification also influenced vertical gradients of the two groups in opposite ways. The model was applied to Suisun Bay, a low-salinity habitat of the San Francisco Bay system that was transformed by the introduction of the exotic clam Potamocorbula amurensis. Simulation results for this Bay were similar to (but more muted than) those for generic habitats, indicating that P. amurensis grazing could have caused a disproportionate loss of diatoms after its introduction. Our model simulations suggest bivalve grazing affects both phytoplankton biomass and community composition in shallow waters. We view these results as hypotheses to be tested with experiments and more complex modeling approaches.

  2. Global Ocean Phytoplankton

    Science.gov (United States)

    Franz, B. A.; Behrenfeld, M. J.; Siegel, D. A.; Werdell, P. J.

    2014-01-01

    Marine phytoplankton are responsible for roughly half the net primary production (NPP) on Earth, fixing atmospheric CO2 into food that fuels global ocean ecosystems and drives the ocean's biogeochemical cycles. Phytoplankton growth is highly sensitive to variations in ocean physical properties, such as upper ocean stratification and light availability within this mixed layer. Satellite ocean color sensors, such as the Sea-viewing Wide Field-of-view Sensor (SeaWiFS; McClain 2009) and Moderate Resolution Imaging Spectroradiometer (MODIS; Esaias 1998), provide observations of sufficient frequency and geographic coverage to globally monitor physically-driven changes in phytoplankton distributions. In practice, ocean color sensors retrieve the spectral distribution of visible solar radiation reflected upward from beneath the ocean surface, which can then be related to changes in the photosynthetic phytoplankton pigment, chlorophyll- a (Chla; measured in mg m-3). Here, global Chla data for 2013 are evaluated within the context of the 16-year continuous record provided through the combined observations of SeaWiFS (1997-2010) and MODIS on Aqua (MODISA; 2002-present). Ocean color measurements from the recently launched Visible and Infrared Imaging Radiometer Suite (VIIRS; 2011-present) are also considered, but results suggest that the temporal calibration of the VIIRS sensor is not yet sufficiently stable for quantitative global change studies. All MODISA (version 2013.1), SeaWiFS (version 2010.0), and VIIRS (version 2013.1) data presented here were produced by NASA using consistent Chla algorithms.

  3. Satellite-detected fluorescence reveals global physiology of ocean phytoplankton

    Directory of Open Access Journals (Sweden)

    M. J. Behrenfeld

    2009-05-01

    Full Text Available Phytoplankton photosynthesis links global ocean biology and climate-driven fluctuations in the physical environment. These interactions are largely expressed through changes in phytoplankton physiology, but physiological status has proven extremely challenging to characterize globally. Phytoplankton fluorescence does provide a rich source of physiological information long exploited in laboratory and field studies, and is now observed from space. Here we evaluate the physiological underpinnings of global variations in satellite-based phytoplankton chlorophyll fluorescence. The three dominant factors influencing fluorescence distributions are chlorophyll concentration, pigment packaging effects on light absorption, and light-dependent energy-quenching processes. After accounting for these three factors, resultant global distributions of quenching-corrected fluorescence quantum yields reveal a striking consistency with anticipated patterns of iron availability. High fluorescence quantum yields are typically found in low iron waters, while low quantum yields dominate regions where other environmental factors are most limiting to phytoplankton growth. Specific properties of photosynthetic membranes are discussed that provide a mechanistic view linking iron stress to satellite-detected fluorescence. Our results present satellite-based fluorescence as a valuable tool for evaluating nutrient stress predictions in ocean ecosystem models and give the first synoptic observational evidence that iron plays an important role in seasonal phytoplankton dynamics of the Indian Ocean. Satellite fluorescence may also provide a path for monitoring climate-phytoplankton physiology interactions and improving descriptions of phytoplankton light use efficiencies in ocean productivity models.

  4. Predictive habitat modelling of humpback (Megaptera novaeangliae) and Antarctic minke (Balaenoptera bonaerensis) whales in the Southern Ocean as a planning tool for seismic surveys

    Science.gov (United States)

    Bombosch, Annette; Zitterbart, Daniel P.; Van Opzeeland, Ilse; Frickenhaus, Stephan; Burkhardt, Elke; Wisz, Mary S.; Boebel, Olaf

    2014-09-01

    Seismic surveys are frequently a matter of concern regarding their potentially negative impacts on marine mammals. In the Southern Ocean, which provides a critical habitat for several endangered cetacean species, seismic research activities are undertaken at a circumpolar scale. In order to minimize impacts of these surveys, pre-cruise planning requires detailed, spatio-temporally resolved knowledge on the likelihood of encountering these species in the survey area. In this publication we present predictive habitat modelling as a potential tool to support decisions for survey planning. We associated opportunistic sightings (2005-2011) of humpback (Megaptera novaeangliae, N=93) and Antarctic minke whales (Balaenoptera bonaerensis, N=139) with a range of static and dynamic environmental variables. A maximum entropy algorithm (Maxent) was used to develop habitat models and to calculate daily basinwide/circumpolar prediction maps to evaluate how species-specific habitat conditions evolved throughout the spring and summer months. For both species, prediction maps revealed considerable changes in habitat suitability throughout the season. Suitable humpback whale habitat occurred predominantly in ice-free areas, expanding southwards with the retreating sea ice edge, whereas suitable Antarctic minke whale habitat was consistently predicted within sea ice covered areas. Daily, large-scale prediction maps provide a valuable tool to design layout and timing of seismic surveys as they allow the identification and consideration of potential spatio-temporal hotspots to minimize potential impacts of seismic surveys on Antarctic cetacean species.

  5. High protein production of phytoplankton in the Amundsen Sea

    Science.gov (United States)

    Jung Song, Ho; Jung Kang, Jae; Kyung Kim, Bo; Joo, HuiTae; Jin Yang, Eun; Park, Jisoo; Hoon Lee, Sang; Heon Lee, Sang

    2016-01-01

    The Amundsen Sea polynya is one of the largest and most productive polynyas in the Southern Ocean and has recently experienced a rapid change in sea ice coverage. However, very little is known about current physiological status of phytoplankton and its quality as food for pelagic herbivores and consequently higher trophic levels in the Amundsen Sea. Using a 13C isotope tracer technique, macromolecular production measurements of phytoplankton at eleven stations were conducted at three light depths (100, 30, and 1%) onboard R/V ARAON in the Amundsen Sea, 2012. The concentrations of major inorganic nutrients were replete at all the productivity stations and no substantial difference in macromolecular production was found between polynya and non-polynya regions. Distinct vertical trends were not observed in low-molecular-weight metabolites (LMWM) and polysaccharide productions, but weak vertical patterns in lipid and protein productions were found during our cruise period. The vertical patterns of lipids slightly increased with depth whereas decreased for protein synthesis in this study, and these vertical trends were not consistent with the results reported previously in the Arctic Ocean. Overall, phytoplankton allocated more photosynthetic carbon into proteins (60.0%) than other macromolecules in the Amundsen Sea, which is markedly higher than those reported previously in the Antarctic Ocean, ranging from 7 to 23%. The high protein synthesis appears to be sustained by high concentrations of major nutrients, which might be a strong factor for general patterns of macromolecular productions of phytoplankton in polar oceans, even under potential iron limitation.

  6. Andreas Acrivos Dissertation Prize Lecture: Phytoplankton in Flow

    Science.gov (United States)

    Durham, William M.

    2012-11-01

    Phytoplankton are small, unicellular organisms that form the base of the marine food web and are cumulatively responsible for half the global oxygen production. While phytoplankton live in an environment characterized by ubiquitous fluid flow, the impact of hydrodynamic conditions on their ecology remain poorly understood. In this talk, I report on two novel biophysical mechanisms based on the interaction between phytoplankton motility and fluid shear. First, I will consider ``thin phytoplankton layers,'' important hotspots of ecological activity that are found meters beneath the ocean surface and contain cell concentrations up to two orders of magnitude above ambient. Using a combination of experiments, individual-based simulations, and continuum modeling, we have shown that layers can form when the vertical migration of phytoplankton is disrupted by hydrodynamic shear. This mechanism which we call ``gyrotactic trapping'' is capable of triggering thin phytoplankton layers under hydrodynamic conditions typical of the environments that often harbor thin layers. Second, I will discuss the potential for turbulent shear to produce patchiness in the spatial distribution of motile phytoplankton. Field measurements have revealed that motile phytoplankton form aggregations at the Kolmogorov scale, whereas non-motile cells do not. We propose a new mechanism for the formation of this small-scale patchiness based on the interplay of gyrotactic motility and turbulent shear. Using laboratory experiments, an analytical model of vortical flow, and isotropic turbulence generated via Direct Numerical Simulations, we found that motile phytoplankton rapidly aggregate, whereas non-motile cells remain randomly distributed. Taken together, these two mechanisms demonstrate that the interaction of cell motility with flow plays a fundamental role in phytoplankton ecology and, as a consequence, can contribute to shape macroscale characteristics of the ocean.

  7. Variability of the Antarctic Circumpolar Current derived from GRACE retrievals, model simulations and in-situ measurements

    Science.gov (United States)

    Boening, C.; Timmermann, R.; Macrander, A.; Schroeter, J.; Boebel, O.

    2008-12-01

    The Gravity Recovery and Climate Experiment (GRACE) provides estimates of the Earth's static and time-variant gravity field. Solutions from various processing centres (GFZ, CSR, GRGS, JPL etc.) enable us to determine mass redistributions on the globe. Given that land signals are generally large compared to anomalies over the ocean, an assessment of the latter requires a particularly careful filtering of the data. We utilized the Finite Element Sea-Ice Ocean Model (FESOM) to develop a filtering algorithm which relies on the spatial coherency of ocean bottom pressure (OBP) anomalies. Taking large-scale circulation patterns into account, the new filter yields an improved representation of OBP (i.e. ocean mass) variability in the filtered GRACE data. In order to investigate the representation of Antarctic Circumpolar Current (ACC) variability in the pattern-filtered GRACE retrievals, an analysis of OBP anomalies in FESOM results and in-situ measurements has been performed. Data from a PIES (Pressure sensor equipped Inverted Echo Sounder) array (36°S-55°S, 2°W-13°E) south of Africa provides bottom pressure recorder data from 2002-2008 for the ACC region. Based on anomalies of OBP gradients between individual instruments, these in-situ measurements give an estimate of the overall transport variability as well as of the movement of ACC fronts and transport redistribution between different sectors of the ACC. The validation of simulated and satellite-derived OBP anomaly gradients against these data yields a measure for the representation of this variability in FESOM and GRACE. Furthermore, model simulations are used to assess the relation between transport variations in individual filaments of the Southern Ocean and total transport variability in this and other sectors of the ACC.

  8. The LARsen Ice Shelf System, Antarctica, LARISSA a Model for Antarctic Integrated System Science (AISS) Investigations using Marine Platforms

    Science.gov (United States)

    Domack, E. W.; Huber, B. A.; Vernet, M.; Leventer, A.; Scambos, T. A.; Mosley-Thompson, E. S.; Smith, C. R.; de Batist, M. A.; Yoon, H.; Larissa

    2010-12-01

    The LARISSA program is the first interdisciplinary project funded in the AISS program of the NSF Office of Polar Programs and was officially launched in the closing days of the IPY. This program brings together investigators, students, and media to address the rapid and fundamental changes taking place in the region of the Larsen Ice Shelf and surrounding areas. Scientific foci include: glaciologic and oceanographic interactions, the response of pelagic and benthic ecosystems to ice shelf decay, sedimentary record of ice shelf break disintegration, the geologic evolution of ice shelf systems over the last 100,000 years, paleoclimate/environmental records from marine sediment and ice cores, and the crustal response to ice mass loss at decade to millennial time scales. The first major field season took place this past austral summer aboard the NB Palmer (cruise NBP10-01) which deployed with a multi-layered logistical infrastructure that included: two Bell 220 aircraft, a multifunctional deep water ROV, video guided sediment corer, jumbo piston core, and an array of oceanographic and biological sensors and instruments. In tandem with this ship based operation Twin Otter aircraft supported an ice core team upon the crest of the Bruce Plateau with logistic support provided by the BAS at Rothera Station. Although unusually heavy sea ice prevented much of the original work from being completed in the Larsen Embayment the interdisciplinary approach proved useful. Further the logistical model of ship based aircraft to support interdisciplinary work proved viable, again despite an unusually severe summer meterologic pattern across the northern Antarctic Peninsula. As the program moves forward other vessels will come into play and the model can be applied to interdisciplinary objectives in other regions of Antarctica which are remote and lack land based infrastructure to support coastal field programs in glaciology, geology, or meteorology. This work could then be completed

  9. On measurements and modeling of ultraviolet radiation with focus on the Antarctic

    OpenAIRE

    Meinander, Outi

    2007-01-01

    The aim of the work was to study, on the basis of literature and experiments, the aspects of measuring and modeling ultraviolet radiation. For measurements, both the spectral and the non-spectral approaches were included. For modeling, physical and statistical models were applied. Thereafter the satellite UV estimates, i.e. spaceborn spectrometer measurements on solar radiation combined with physical UV modeling, were shortly introduced. Case studies were carried out for each of the five case...

  10. Antarctic research today

    International Nuclear Information System (INIS)

    With the appetite for living and dead natural resources, the political and economical interest concerning the Antarctic increases throughout the world. There are three interrelated main subjects accounting for the international interest: The shelf tectonic puzzle of the original continent of Gondwana, where the Antarctic is situated in the centre, between Australia, South Africa and South America, and the hopes concerning the existence of mineral resources under the ice of the Antarctic are based thereon. The Antarctic forms the biggest unified living space of the world. (orig.)

  11. Decadal-Scale Response of the Antarctic Ice sheet to a Warming Ocean using the POPSICLES Coupled Ice Sheet-Ocean model

    Science.gov (United States)

    Martin, D. F.; Asay-Davis, X.; Cornford, S. L.; Price, S. F.; Ng, E. G.; Collins, W.

    2015-12-01

    We present POPSICLES simulation results covering the full Antarctic Ice Sheet and the Southern Ocean spanning the period from 1990 to 2010. We use the CORE v. 2 interannual forcing data to force the ocean model. Simulations are performed at 0.1o(~5 km) ocean resolution with adaptive ice sheet resolution as fine as 500 m to adequately resolve the grounding line dynamics. We discuss the effect of improved ocean mixing and subshelf bathymetry (vs. the standard Bedmap2 bathymetry) on the behavior of the coupled system, comparing time-averaged melt rates below a number of major ice shelves with those reported in the literature. We also present seasonal variability and decadal melting trends from several Antarctic regions, along with the response of the ice shelves and the consequent dynamic response of the grounded ice sheet.POPSICLES couples the POP2x ocean model, a modified version of the Parallel Ocean Program, and the BISICLES ice-sheet model. POP2x includes sub-ice-shelf circulation using partial top cells and the commonly used three-equation boundary layer physics. Standalone POP2x output compares well with standard ice-ocean test cases (e.g., ISOMIP) and other continental-scale simulations and melt-rate observations. BISICLES makes use of adaptive mesh refinement and a 1st-order accurate momentum balance similar to the L1L2 model of Schoof and Hindmarsh to accurately model regions of dynamic complexity, such as ice streams, outlet glaciers, and grounding lines. Results of BISICLES simulations have compared favorably to comparable simulations with a Stokes momentum balance in both idealized tests (MISMIP-3d) and realistic configurations.The figure shows the BISICLES-computed vertically-integrated grounded ice velocity field 5 years into a 20-year coupled full-continent Antarctic-Southern-Ocean simulation. Submarine melt rates are painted onto the surface of the floating ice shelves. Grounding lines are shown in green.

  12. The dynamical landscape of marine phytoplankton diversity.

    Science.gov (United States)

    Lévy, Marina; Jahn, Oliver; Dutkiewicz, Stephanie; Follows, Michael J; d'Ovidio, Francesco

    2015-10-01

    Observations suggest that the landscape of marine phytoplankton assemblage might be strongly heterogeneous at the dynamical mesoscale and submesoscale (10-100 km, days to months), with potential consequences in terms of global diversity and carbon export. But these variations are not well documented as synoptic taxonomic data are difficult to acquire. Here, we examine how phytoplankton assemblage and diversity vary between mesoscale eddies and submesoscale fronts. We use a multi-phytoplankton numerical model embedded in a mesoscale flow representative of the North Atlantic. Our model results suggest that the mesoscale flow dynamically distorts the niches predefined by environmental contrasts at the basin scale and that the phytoplankton diversity landscape varies over temporal and spatial scales that are one order of magnitude smaller than those of the basin-scale environmental conditions. We find that any assemblage and any level of diversity can occur in eddies and fronts. However, on a statistical level, the results suggest a tendency for larger diversity and more fast-growing types at fronts, where nutrient supplies are larger and where populations of adjacent water masses are constantly brought into contact; and lower diversity in the core of eddies, where water masses are kept isolated long enough to enable competitive exclusion.

  13. Assessment and Consequences of the Delayed Breakup of the Antarctic Polar Vortex in Two Versions of the GEOS Chemistry-Climate Model

    Science.gov (United States)

    Hurwitz, M.M.; Newman, P.A.; Li, F.

    2008-01-01

    In mid-winter, winds circle the globe at speeds greater than 200 km/hr (approximately 130mph) in the middle atmosphere. This strong jet bounds the region known as the polar vortex. The presence of the Antarctic polar vortex is a key ingredient in the formation of the 'ozone hole', because the air inside the vortex is cold and isolated from lower latitudes, creating ideal conditions for large-scale chemical ozone depletion. Many atmospheric models are not able to reproduce observed winds in the middle atmosphere. Specifically, the polar vortices tend to break down too late and peak wind speeds are higher than observed. Hurwitz et al. find that the delayed break-up of the Antarctic polar vortex is due to weaker-than-observed wave driving from the lower atmosphere during the October-November period. The delayed break-up of the Antarctic polar vortex changes the temperature structure of the middle atmosphere, which biases the amount of chemical ozone depletion that can occur in late winter and spring. Also, the extended lifetime of the polar vortex strengthens the 'overturning' circulation cell in the middle atmosphere, changing the amount of ozone, methane and other chemical species that is transported from low to high latitudes. As greenhouse gas concentrations continue to rise, the atmospheric temperature structure and resulting wind structure are expected to change. Clearly, if models cannot duplicate the observed late 20th century high-latitude winds, their ability to simulate the polar vortices in future must be poor. Understanding model weaknesses and improving the modeled polar vortices will be necessary for accurate predictions of ozone recovery in the coming century.

  14. The importance of sea-ice area biases in 21st century multi-model projections of Antarctic net precipitation and temperature and their relative change

    Science.gov (United States)

    Bracegirdle, T.

    2015-12-01

    Climate models exhibit large biases in sea ice area (SIA) in their historical simulations. This study has explored the impacts of these biases on multi-model uncertainty in CMIP5 ensemble projections of 21st century change in Antarctic surface temperature, net precipitation and SIA. The analysis is based on time slice climatologies in the RCP8.5 future scenario (2070-2099) and historical (1970-1999) simulations across 37 different CMIP5 models. Projected changes in net precipitation, temperature and SIA are found to be strongly associated with simulated historical mean SIA (e.g. cross-model correlations of r = 0.77, 0.70 and -0.86, respectively). Furthermore, historical SIA bias is found to have a large impact on the simulated ratio between net precipitation response and temperature response. This ratio is smaller in models with smaller-than-observed historical SIA. These findings are particularly relevant to quantifying and reducing model uncertainty in projections of Antarctic surface mass balance and associated contributions to sea level change.

  15. Microphysical Modeling and POAM III Observations of Aerosol Extinction in the 1998-2003 Antarctic Stratosphere

    Science.gov (United States)

    Benson, C. M.; Drdla, K.; Nedoluha, G. E.; Shettle, E. P.; Alfred, J.; Hoppel, K. W.

    2005-12-01

    The Integrated Microphysics and Chemistry on Trajectories (IMPACT) model is used to study Polar stratospheric cloud formation and evolution in the Southern Polar vortex during the 1998-2003 winters. The model is applied to individual air parcels which are advected through the vortex on UKMO wind and temperature fields. The parcel temperature and pressure histories are used by IMPACT to calculate the formation and sedimentation of ice, NAT, SAT, and STS aerosols. Model results are validated by the Polar Ozone and Aerosol Measurement (POAM) III solar occultation instrument. Comparisons of POAM data to the model results help to constrain the microphysical parameters influencing aerosol formation and growth. Measurements of the water vapor mixing ratio are of limited use in clarifying the model microphysics; however, POAM measurements of aerosol extinction prove to be valuable in differentiating model runs. Specifically, the relationship of aerosol extinction to temperature arises from the different temperatures at which the various particle types form and grow. Comparisons of IMPACT calculations of this relationship to POAM measurements constrain the initial fraction of nuclei available for heterogeneous NAT freezing to 0.02% of all aerosols. Constraints are also placed on the ice accommodation coefficient and the NAT-ice lattice compatibility factor. However, these two parameters have similar effects on the extinction-temperature relationship, and thus a range of values are permissible for each.

  16. Antarctic news clips, 1991

    Science.gov (United States)

    1991-08-01

    Published stories are presented that sample a year's news coverage of Antarctica. The intent is to provide the U.S. Antarctic Program participants with a digest of current issues as presented by a variety of writers and popular publications. The subject areas covered include the following: earth science; ice studies; stratospheric ozone; astrophysics; life science; operations; education; antarctic treaty issues; and tourism

  17. Programmed Cell Death in Unicellular Phytoplankton.

    Science.gov (United States)

    Bidle, Kay D

    2016-07-11

    Unicellular, planktonic, prokaryotic and eukaryotic photoautotrophs (phytoplankton) have an ancient evolutionary history on Earth during which time they have played key roles in the regulation of marine food webs, biogeochemical cycles, and Earth's climate. Since they represent the basis of aquatic ecosystems, the manner in which phytoplankton die critically determines the flow and fate of photosynthetically fixed organic matter (and associated elements), ultimately constraining nutrient flow. Programmed cell death (PCD) and associated pathway genes, which are triggered by a variety of abiotic (nutrient, light, osmotic) and biotic (virus infection, allelopathy) environmental stresses, have an integral grip on cell fate, and have shaped the ecological success and evolutionary trajectory of diverse phytoplankton lineages. A combination of physiological, biochemical, and genetic techniques in model algal systems has demonstrated a conserved molecular and mechanistic framework of stress surveillance, signaling, and death activation pathways, involving collective and coordinated participation of organelles, redox enzymes, metabolites, and caspase-like proteases. This mechanistic understanding has provided insight into the integration of sensing and transduction of stress signals into cellular responses, and the mechanistic interfaces between PCD, cell stress and virus infection pathways. It has also provided insight into the evolution of PCD in unicellular photoautotrophs, the impact of PCD on the fate of natural phytoplankton assemblages and its role in aquatic biogeochemical cycles. PMID:27404255

  18. GLIMMER Antarctic Ice Sheet Model,an experimental research of moving boundary condition

    Institute of Scientific and Technical Information of China (English)

    Tang Xueyuan; Sun Bo; Zhang Zhanhai; Li Yuansheng; Yang Qinghua

    2008-01-01

    A 3 D coupled ice sheet model,GLIMMER model is introduced,and an idealized ice sheet experiment under the EISMINT 1 criterion of moving boundary condition is presented.The results of the experiment reveal that for a steady state ice sheet profile the characteristic curves describe the process of evolution which are accordant with theoretical estimates.By solving the coupled thermodynamics equations of ice sheet,one may find the characteristic curves which derived from the conservation of the mass,energy and momentum to the ice flow profile.At the same time,an agreement,approximate to the GLIMMER case and the confirmed theoretical results,is found.Present study is explorihg work to introduceand discuss the handicaps of EISMINT criterion and GLIMMER,and prospect a few directions of the GLIMMER model.

  19. On the influence of model physics on simulations of Arctic and Antarctic sea ice

    Directory of Open Access Journals (Sweden)

    F. Massonnet

    2011-09-01

    Full Text Available Two hindcast (1983–2007 simulations are performed with the global, ocean-sea ice models NEMO-LIM2 and NEMO-LIM3 driven by atmospheric reanalyses and climatologies. The two simulations differ only in their sea ice component, while all other elements of experimental design (resolution, initial conditions, atmospheric forcing are kept identical. The main differences in the sea ice models lie in the formulation of the subgrid-scale ice thickness distribution, of the thermodynamic processes, of the sea ice salinity and of the sea ice rheology. To assess the differences in model skill over the period of investigation, we develop a set of metrics for both hemispheres, comparing the main sea ice variables (concentration, thickness and drift to available observations and focusing on both mean state and seasonal to interannual variability. Based upon these metrics, we discuss the physical processes potentially responsible for the differences in model skill. In particular, we suggest that (i a detailed representation of the ice thickness distribution increases the seasonal to interannual variability of ice extent, with spectacular improvement for the simulation of the recent observed summer Arctic sea ice retreats, (ii the elastic-viscous-plastic rheology enhances the response of ice to wind stress, compared to the classical viscous-plastic approach, (iii the grid formulation and the air-sea ice drag coefficient affect the simulated ice export through Fram Strait and the ice accumulation along the Canadian Archipelago, and (iv both models show less skill in the Southern Ocean, probably due to the low quality of the reanalyses in this region and to the absence of important small-scale oceanic processes at the models' resolution (~1°.

  20. Toxin-allelopathy among phytoplankton species prevents competitive exclusion

    OpenAIRE

    Roy, Shovonlal; Chattopadhyay, Joydev

    2006-01-01

    Toxic or allelopathic compounds liberated by toxin-producing phytoplankton (TPP) acts as a strong mediator in plankton dynamics. On an analysis of a set of phytoplankton biomass-data that have been collected by our group in the North-West part of the Bay of Bengal, and by analysis of a three-component mathematical model under a constant as well as a stochastic environment, we explore the role of toxin-allelopathy in determining the dynamic behaviour of the competing-phytoplankton species. The...

  1. Large-Ensemble Modeling of Past Variations in West Antarctic Embayments

    Science.gov (United States)

    Pollard, D.; Deconto, R. M.

    2014-12-01

    Recent observations of thinning and retreat of the Pine Island and Thwaites Glaciers identify this sector of West Antarctica as particularly vulnerable to future climate change. To date, most future modeling of these glaciers has beenvalidated using recent and modern observations. As an alternate approach,we apply a hybrid 3-D ice sheet-shelf model to the last deglacial retreat in this sector, making use of geologic data of ice extents from ~20,000 years BP to present, both for the Amundsen Sea sector and also for the Ross and Weddellembayments.Following recent ice-sheet studies, we use Large-Ensemble statistical techniques, performing sets of ~500 to 1000 runs with varying model parameters. The model is run for the last 20 kyrs on 5 to 20-km grids spanning West Antarctica, with lateral boundary conditions from a prior continental-scale simulation. An objective score for each run is calculated using reconstructed past grounding lines, shelf extents, relative sea levels, and modern conditions. Runs are extended into the future (few millennia) with simple atmospheric and oceanic forcing. The goal is to produce calibrated probabilistic envelopes of model parameter ranges and simulated ice retreat.Preliminary results are presented for Large Ensembles with (i) Latin HyperCube sampling in high-dimensional parameter space, and (ii) dense sampling with a lower number of parameters. We focus on optimal parameter differencesbetween the 3 embayments, validation with other paleo data, contribution to meltwater pulses ~14 to 12 ka, and future projections. Most reasonable parameter combinations produce drastic future retreat into the interior Pine Island and Thwaites basins within ~2000 years, adding ~2 m to global sea-level rise.

  2. Model estimating the effect of marginal ice zone processes on the phytoplankton primary production and air-sea flux of CO2 in the Barents Sea

    Science.gov (United States)

    Dvornikov, Anton; Sein, Dmitry; Ryabchenko, Vladimir; Gorchakov, Victor; Martjyanov, Stanislav

    2016-04-01

    This study is aimed to assess the impact of sea ice on the primary production of phytoplankton (PPP) and air-sea CO2 flux in the Barents Sea. To get the estimations, we apply a three-dimensional eco-hydrodynamic model based on the Princeton Ocean Model which includes: 1) a module of sea ice with 7 categories, and 2) the 11-component module of marine pelagic ecosystem developed in the St. Petersburg Branch, Institute of Oceanology. The model is driven by atmospheric forcing, prescribed from the reanalysis NCEP / NCAR, and conditions on the open sea boundary, prescribed from the regional model of the atmosphere-ocean-sea ice-ocean biogeochemistry, developed at Max Planck Institute for Meteorology, Hamburg. Comparison of the model results for the period 1998-2007 with satellite data showed that the model reproduces the main features of the evolution of the sea surface temperature, seasonal changes in the ice extent, surface chlorophyll "a" concentration and PPP in the Barents Sea. Model estimates of the annual PPP for whole sea, APPmod, appeared in 1.5-2.3 times more than similar estimates, APPdata, from satellite data. The main reasons for this discrepancy are: 1) APPdata refers to the open water, while APPmod, to the whole sea area (under the pack ice and marginal ice zone (MIZ) was produced 16 - 38% of PPP); and 2) values of APPdata are underestimated because of the subsurface chlorophyll maximum. During the period 1998-2007, the modelled maximal (in the seasonal cycle) sea ice area has decreased by 15%. This reduction was accompanied by an increase in annual PPP of the sea at 54 and 63%, based, respectively, on satellite data and the model for the open water. According to model calculations for the whole sea area, the increase is only 19%. Using a simple 7-component model of oceanic carbon cycle incorporated into the above hydrodynamic model, the CO2 exchange between the atmosphere and sea has been estimated in different conditions. In the absence of biological

  3. Modelling the mass balance and salinity of Arctic and Antarctic sea ice

    OpenAIRE

    Vancoppenolle, Martin

    2008-01-01

    Ice formed from seawater, called sea ice, is both an important actor in and a sensitive indicator of climate change. Covering 7% of the World Ocean, sea ice damps the atmosphere-ocean exchanges of heat, radiation and momentum in polar regions. It also affects the oceanic circulation at a global scale. Recent satellite and submarine observations systems indicate a sharp decrease in the extent and volume of Arctic sea ice over the last 30 years. In addition, climate models project drastic sea i...

  4. Inclusion of mountain wave-induced cooling for the formation of PSCs over the Antarctic Peninsula in a chemistry–climate model

    Directory of Open Access Journals (Sweden)

    A. Orr

    2014-07-01

    Full Text Available An important source of polar stratospheric clouds (PSCs, which play a crucial role in controlling polar stratospheric ozone depletion, is from the temperature fluctuations induced by mountain waves. However, this formation mechanism is usually missing in chemistry–climate models because these temperature fluctuations are neither resolved nor parameterised. Here, we investigate the representation of stratospheric mountain wave-induced temperature fluctuations by the UK Met Office Unified Model (UM at high and low spatial resolution against Atmospheric Infrared Sounder satellite observations for three case studies over the Antarctic Peninsula. At a high horizontal resolution (4 km the mesoscale configuration of the UM correctly simulates the magnitude, timing, and location of the measured temperature fluctuations. By comparison, at a low horizontal resolution (2.5° × 3.75° the climate configuration fails to resolve such disturbances. However, it is demonstrated that the temperature fluctuations computed by a mountain wave parameterisation scheme inserted into the climate configuration (which computes the temperature fluctuations due to unresolved mountain waves are in excellent agreement with the mesoscale configuration responses. The parameterisation was subsequently used to compute the local mountain wave-induced cooling phases in the chemistry–climate configuration of the UM. This increased stratospheric cooling was passed to the PSC scheme of the chemistry–climate model, and caused a 30–50% increase in PSC surface area density over the Antarctic Peninsula compared to a 30 year control simulation.

  5. Controls and variability of solute and sedimentary fluxes in Antarctic and sub-Antarctic Environments

    Science.gov (United States)

    Zwolinski, Zbigniew

    2015-04-01

    The currently prepared SEDIBUD Book on "Source-to-Sink Fluxes in Undisturbed Cold Environments" (edited by Achim A. Beylich, John C. Dixon and Zbigniew Zwolinski and published by Cambridge University Press) is summarizing and synthesizing the achievements of the International Association of Geomorphologists` (I.A.G./A.I.G.) Working Group SEDIBUD (Sediment Budgets in Cold Environments), which has been active since 2005 (http://www.geomorph.org/wg/wgsb.html). The book comprises five parts. One of them is part about sub-Antarctic and Antarctic Environments. This part "Sub-Antarctic and Antarctic Environments" describes two different environments, namely oceanic and continental ones. Each part contains results of research on environmental drivers and rates of contemporary solute and sedimentary fluxes in selected sites. Apart from describing the environmental conditions of the whole continent of Antarctica and sub-Antarctic islands (Zb.Zwolinski, M.Kejna, A.N.Lastochkin, A.Zhirov, S.Boltramovich) this part of the book characterizes terrestrial polar oases free from multi-year ice and snow covers (Zb.Zwolinski). The detailed results of geoecological and sedimentological research come from different parts of Antarctica. Antarctic continental shelf (E.Isla) is an example of sub-Antarctic oceanic environment. South Shetlands, especially King George Island (Zb.Zwolinski, M.Kejna, G.Rachlewicz, I.Sobota, J.Szpikowski), is an example of sub-Antarctic terrestrial environment. Antarctic Peninsula (G.Vieira, M.Francelino, J.C.Fernandes) and surroundings of McMurdo Dry Valleys (W.B.Lyons, K.A.Welch, J.Levy, A.Fountain, D.McKnight) are examples of Antarctic continental environments. The key goals of the Antarctic and sub-Antarctic book chapters are following: (i) identify the main environmental drivers and rates of contemporary solute and sedimentary fluxes, and (ii) model possible effects of projected climate change on solute and sedimentary fluxes in cold climate environments

  6. Amplified Arctic warming by phytoplankton under greenhouse warming

    OpenAIRE

    Park, Jong-Yeon; Kug, Jong-Seong; Bader, Jürgen; Rolph, Rebecca; Kwon, Minho

    2015-01-01

    One of the important impacts of marine phytoplankton on climate systems is the geophysical feedback by which chlorophyll and the related pigments in phytoplankton absorb solar radiation and then change sea surface temperature. Yet such biogeophysical impact is still not considered in many climate projections by state-of-the-art climate models, nor is its impact on the future climate quantified. This study shows that, by conducting global warming simulations with and without an active marine e...

  7. Simulation of annual biogeochemical cycles of nutrient balance, phytoplankton bloom(s), and DO in Puget Sound using an unstructured grid model

    Energy Technology Data Exchange (ETDEWEB)

    Khangaonkar, Tarang; Sackmann, Brandon; Long, Wen; Mohamedali, Teizeen; Roberts, Mindy

    2012-08-14

    Nutrient pollution from rivers, nonpoint source runoff, and nearly 100 wastewater discharges is a potential threat to the ecological health of Puget Sound with evidence of hypoxia in some basins. However, the relative contributions of loads entering Puget Sound from natural and anthropogenic sources, and the effects of exchange flow from the Pacific Ocean are not well understood. Development of a quantitative model of Puget Sound is thus presented to help improve our understanding of the annual biogeochemical cycles in this system using the unstructured grid Finite-Volume Coastal Ocean Model framework and the Integrated Compartment Model (CE-QUAL-ICM) water quality kinetics. Results based on 2006 data show that phytoplankton growth and die-off, succession between two species of algae, nutrient dynamics, and dissolved oxygen in Puget Sound are strongly tied to seasonal variation of temperature, solar radiation, and the annual exchange and flushing induced by upwelled Pacific Ocean waters. Concentrations in the mixed outflow surface layer occupying approximately 5–20 m of the upper water column show strong effects of eutrophication from natural and anthropogenic sources, spring and summer algae blooms, accompanied by depleted nutrients but high dissolved oxygen levels. The bottom layer reflects dissolved oxygen and nutrient concentrations of upwelled Pacific Ocean water modulated by mixing with biologically active surface outflow in the Strait of Juan de Fuca prior to entering Puget Sound over the Admiralty Inlet. The effect of reflux mixing at the Admiralty Inlet sill resulting in lower nutrient and higher dissolved oxygen levels in bottom waters of Puget Sound than the incoming upwelled Pacific Ocean water is reproduced. Finally, by late winter, with the reduction in algal activity, water column constituents of interest, were renewed and the system appeared to reset with cooler temperature, higher nutrient, and higher dissolved oxygen waters from the Pacific

  8. Phytoplankton succession in recurrently fluctuating environments.

    Directory of Open Access Journals (Sweden)

    Daniel L Roelke

    Full Text Available Coastal marine systems are affected by seasonal variations in biogeochemical and physical processes, sometimes leading to alternating periods of reproductive growth limitation within an annual cycle. Transitions between these periods can be sudden or gradual. Human activities, such as reservoir construction and interbasin water transfers, influence these processes and can affect the type of transition between resource loading conditions. How such human activities might influence phytoplankton succession is largely unknown. Here, we employ a multispecies, multi-nutrient model to explore how nutrient loading switching mode might affect phytoplankton succession. The model is based on the Monod-relationship, predicting an instantaneous reproductive growth rate from ambient inorganic nutrient concentrations whereas the limiting nutrient at any given time was determined by Liebig's Law of the Minimum. When these relationships are combined with population loss factors, such as hydraulic displacement of cells associated with inflows, a characterization of a species' niche can be achieved through application of the R* conceptual model, thus enabling an ecological interpretation of modeling results. We found that the mode of reversal in resource supply concentrations had a profound effect. When resource supply reversals were sudden, as expected in systems influenced by pulsed inflows or wind-driven mixing events, phytoplankton were characterized by alternating succession dynamics, a phenomenon documented in inland water bodies of temperate latitudes. When resource supply reversals were gradual, as expected in systems influenced by seasonally developing wet and dry seasons, or annually occurring periods of upwelling, phytoplankton dynamics were characterized by mirror-image succession patterns. This phenomenon has not been reported previously in plankton systems but has been observed in some terrestrial plant systems. These findings suggest that a

  9. Phytoplankton succession in recurrently fluctuating environments.

    Science.gov (United States)

    Roelke, Daniel L; Spatharis, Sofie

    2015-01-01

    Coastal marine systems are affected by seasonal variations in biogeochemical and physical processes, sometimes leading to alternating periods of reproductive growth limitation within an annual cycle. Transitions between these periods can be sudden or gradual. Human activities, such as reservoir construction and interbasin water transfers, influence these processes and can affect the type of transition between resource loading conditions. How such human activities might influence phytoplankton succession is largely unknown. Here, we employ a multispecies, multi-nutrient model to explore how nutrient loading switching mode might affect phytoplankton succession. The model is based on the Monod-relationship, predicting an instantaneous reproductive growth rate from ambient inorganic nutrient concentrations whereas the limiting nutrient at any given time was determined by Liebig's Law of the Minimum. When these relationships are combined with population loss factors, such as hydraulic displacement of cells associated with inflows, a characterization of a species' niche can be achieved through application of the R* conceptual model, thus enabling an ecological interpretation of modeling results. We found that the mode of reversal in resource supply concentrations had a profound effect. When resource supply reversals were sudden, as expected in systems influenced by pulsed inflows or wind-driven mixing events, phytoplankton were characterized by alternating succession dynamics, a phenomenon documented in inland water bodies of temperate latitudes. When resource supply reversals were gradual, as expected in systems influenced by seasonally developing wet and dry seasons, or annually occurring periods of upwelling, phytoplankton dynamics were characterized by mirror-image succession patterns. This phenomenon has not been reported previously in plankton systems but has been observed in some terrestrial plant systems. These findings suggest that a transition from alternating

  10. The Biogeochemical Role of Antarctic Krill and Baleen Whales in Southern Ocean Nutrient Cycling.

    Science.gov (United States)

    Ratnarajah, L.

    2015-12-01

    Iron limits primary productivity in large areas of the Southern Ocean. It has been suggested that baleen whales form a crucial part of biogeochemical cycling processes through the consumption of nutrient-rich krill and subsequent defecation, but evidence on their contribution is scarce. We analysed the concentration of iron in Antarctic krill and baleen whale faeces and muscle. Iron concentrations in Antarctic krill were over 1 million times higher, and whale faecal matter were almost 10 million times higher than typical Southern Ocean High Nutrient Low Chlorophyll seawater concentrations. This suggests that Antarctic krill act as a reservoir of in in Southern Ocean surface waters, and that baleen whales play an important role in converting this fixed iron into a liquid form in their faeces. We developed an exploratory model to examine potential contribution of blue, fin and humpback whales to the Southern Ocean iron cycle to explore the effect of the recovery of great whales to historical levels. Our results suggest that pre-exploitation populations of blue whales and, to a lesser extent fin and humpback whales, could have contributed to the more effective recycling of iron in surface waters, resulting in enhanced phytoplankton production. This enhanced primary productivity is estimated to be: 8.3 x 10-5 to 15 g C m-2 yr-1 (blue whales), 7 x 10-5 to 9 g C m-2 yr-1 (fin whales), and 10-5 to 1.7 g C m-2 yr-1 (humpback whales). To put these into perspective, current estimates of primary production in the Southern Ocean from remotely sensed ocean colour are in the order of 57 g C m-2 yr-1 (south of 50°). The high degree of uncertainty around the magnitude of these increases in primary productivity is mainly due to our limited quantitative understanding of key biogeochemical processes including iron content in krill, krill consumption rates by whales, persistence of iron in the photic zone, bioavailability of retained iron, and carbon-to-iron ratio of phytoplankton

  11. Distribution of phytoplankton functional types in high-nitrate low-chlorophyll waters in a new diagnostic ecological indicator model

    DEFF Research Database (Denmark)

    Palacz, Artur; St. John, Michael; Brevin, R.J.W.;

    2013-01-01

    Modeling and monitoring plankton functional types (PFTs) is challenged by insufficient amount of field measurements to ground-truth both plankton models and bio-optical algorithms. In this study, we combine remote sensing data and a dynamic plankton model to simulate an ecologically-sound spatial...

  12. Phytoplankton Monitoring Network - Phytoplankton Analysis with Associated Collection Information

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A qualitative collection of data that includes salinity, temperature, phytoplankton counts and abundance ratios obtained from surface tows in the estuarine and...

  13. Challenges to the Future - Conservation of the Antarctic

    NARCIS (Netherlands)

    Chown, S.L.; Lee, J.E.; Hughes, K.A.; Barnes, J.; Bergstrom, D.M.; Convey, P.; Cowan, D.A.; Crosbie, K.; Dyer, G.; Frenot, Y.; Grant, S.M.; Herr, D.; Kennicutt, M.C.; Lamers, M.A.J.; Murray, A.; Possingham, H.P.; Reid, K.; Riddle, M.J.; Ryan, P.G.; Sanson, L.; Shaw, J.D.; Sparrow, M.D.; Summerhayes, C.; Terauds, A.; Wall, D.H.

    2012-01-01

    The Antarctic Treaty System, acknowledged as a successful model of cooperative regulation of one of the globe's largest commons (1), is under substantial pressure. Concerns have been raised about increased stress on Antarctic systems from global environmental change and growing interest in the regio

  14. In situ phytoplankton distributions in the Amundsen Sea Polynya measured by autonomous gliders

    Directory of Open Access Journals (Sweden)

    Oscar Schofield

    2015-10-01

    Full Text Available Abstract The Amundsen Sea Polynya is characterized by large phytoplankton blooms, which makes this region disproportionately important relative to its size for the biogeochemistry of the Southern Ocean. In situ data on phytoplankton are limited, which is problematic given recent reports of sustained change in the Amundsen Sea. During two field expeditions to the Amundsen Sea during austral summer 2010–2011 and 2014, we collected physical and bio-optical data from ships and autonomous underwater gliders. Gliders documented large phytoplankton blooms associated with Antarctic Surface Waters with low salinity surface water and shallow upper mixed layers (< 50 m. High biomass was not always associated with a specific water mass, suggesting the importance of upper mixed depth and light in influencing phytoplankton biomass. Spectral optical backscatter and ship pigment data suggested that the composition of phytoplankton was spatially heterogeneous, with the large blooms dominated by Phaeocystis and non-bloom waters dominated by diatoms. Phytoplankton growth rates estimated from field data (≤ 0.10 day−1 were at the lower end of the range measured during ship-based incubations, reflecting both in situ nutrient and light limitations. In the bloom waters, phytoplankton biomass was high throughout the 50-m thick upper mixed layer. Those biomass levels, along with the presence of colored dissolved organic matter and detritus, resulted in a euphotic zone that was often < 10 m deep. The net result was that the majority of phytoplankton were light-limited, suggesting that mixing rates within the upper mixed layer were critical to determining the overall productivity; however, regional productivity will ultimately be controlled by water column stability and the depth of the upper mixed layer, which may be enhanced with continued ice melt in the Amundsen Sea Polynya.

  15. SYKE Proficiency Test 10/2014 Phytoplankton

    OpenAIRE

    Vuorio, Kristiina; Björklöf, Katarina; Kuosa, Harri; Jokipii, Reija; JÀrvinen, Marko; Lehtinen, Sirpa; Leivuori, Mirja; NiemelÀ, Maija; VÀisÀnen, Ritva

    2015-01-01

    The Finnish Environment Institute (SYKE) organized in 2014 the fourth virtual phytoplankton proficiency test based on filmed material. A total of 39 analysts from 27 organizations and eight countries took part the test. The test material represented phytoplankton that typically occurs in boreal lakes and in the northern Baltic Sea. The test included three components: 1) phytoplankton species identification test, 2) phytoplankton counting test and 3) phytoplankton measurement of cell dimens...

  16. Diversity and distribution of winter phytoplankton in the Arabian Gulf and the Sea of Oman

    Science.gov (United States)

    Polikarpov, Igor; Saburova, Maria; Al-Yamani, Faiza

    2016-05-01

    The spatial distribution of the phytoplankton (diversity, composition, and cell abundance) was described in relation to local environmental conditions across the Arabian Gulf, the Strait of Hormuz, and the Sea of Oman based on data of ROPME cruise of winter 2006. The 376 phytoplankton taxa identified in these waters represented a diverse composition of species with a prevalence of dinoflagellates and diatoms. Three peaks in the phytoplankton abundance were recorded throughout the studied area associated with diatom-dominated phytoplankton blooms in the central and northwestern part of the Arabian Gulf and in the Sea of Oman and the adjacent waters. The studied area was divided into three main regions by cluster analysis based on differences in the phytoplankton composition and concentration. The Sea of Oman and the Strait of Hormuz were occupied by highly abundant, strongly diatom-dominated phytoplankton assemblage. The Arabian Gulf was divided into two main regions along a diagonal northwest-southeast axis, with rather diatom-dominated phytoplankton assemblage off the south and along the Iranian coast but with flagellate-dominated phytoplankton of the north and along the Arabian coast. The distance-based linear modeling revealed a significant relationship between the phytoplankton composition and water masses as indexed by salinity. Our results demonstrated that abundance and composition of winter phytoplankton were related to water circulation pattern in the Arabian Gulf and the Sea of Oman.

  17. Reactivity of metals for marine phytoplankton

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, N.S.

    1986-03-01

    The concentration of metals by marine phytoplankton, assessed for diverse species in laboratory culture experiments with radiotracer methodology and taken together with literature values for other metals, was analyzed in light of geochemical models describing particle surface chemistry. Concentration factors vary among the metals from approx. ordered 0 to approx. ordered 10/sup 6/. Regression analyses show that, at equilibrium, the logs of the concentration factors are exponentially related to solubility products of metal hydroxides and to cytotoxicity and are linearly related to the log of the mean oceanic residence times (years) of the metals. It would appear that concentration factors and toxicity of metals in marine phytoplankton and oceanic residence times of metals can be predicted to within an order of magnitude from the chemical literature.

  18. Size related processes in phytoplankton

    OpenAIRE

    Sandow, Marcel

    2004-01-01

    Growth, death, respiration, excretion and sedimentation describe the major rate processes of phytoplankton. These rates often scale allometrically (rate=a*mass^b). The allometric coefficient (b) describes the deviation from a linear reltionship. Literature values derived from experiments showed allometric coefficients of -0.48 to -0.1. Experiments with natural phytoplankton communities from the baltic and the subtropical gyre of the North Atlantic ocean showed an allometric coeffcient range o...

  19. Factors controlling phytoplankton ice-edge blooms in the marginal ice-zone of the northwestern Weddell Sea during sea ice retreat 1988 : field observations and mathematical modelling

    NARCIS (Netherlands)

    Lancelot, Christiane; Mathot, Sylvie; Veth, Cornelis; Baar, Hein de

    1993-01-01

    The factors controlling phytoplankton bloom development in the marginal ice zone of the northwestern Weddell Sea were investigated during the EPOS (Leg 2) expedition (1988). Measurements were made of physical and chemical processes and biological activities associated with the process of ice-melting

  20. First geomagnetic measurements in the Antarctic region

    Science.gov (United States)

    Raspopov, O. M.; Demina, I. M.; Meshcheryakov, V. V.

    2014-05-01

    Based on data from literature and archival sources, we have further processed and analyzed the results of geomagnetic measurements made during the 1772-1775 Second World Expedition by James Cook and the 1819-1821 overseas Antarctic Expedition by Russian mariners Bellingshausen and Lazarev. Comparison with the GUFM historical model showed that there are systematic differences in the spatial structure of both the declination and its secular variation. The results obtained can serve as a basis for the construction of regional models of the geomagnetic field for the Antarctic region.

  1. Phytoplankton depth profiles and their transitions near the critical sinking velocity.

    Science.gov (United States)

    Kolokolnikov, Theodore; Ou, Chunhua; Yuan, Yuan

    2009-07-01

    We consider a simple phytoplankton model introduced by Shigesada and Okubo which incorporates the sinking and self-shading effect of the phytoplankton. The amount of light the phytoplankton receives is assumed to be controlled by the density of the phytoplankton population above the given depth. We show the existence of non-homogeneous solutions for any water depth and study their profiles and stability. Depending on the sinking rate of the phytoplankton, light intensity and water depth, the plankton can concentrate either near the surface, at the bottom of the water column, or both, resulting in a "double-peak" profile. As the buoyancy passes a certain critical threshold, a sudden change in the phytoplankton profile occurs. We quantify this transition using asymptotic techniques. In all cases we show that the profile is locally stable. This generalizes the results of Shigesada and Okubo where infinite depth was considered.

  2. Species dynamics in phytoplankton blooms: Incomplete mixing and competition for light

    NARCIS (Netherlands)

    Huisman, J.; Van Oostveen, P.; Weissing, F.J.

    1999-01-01

    With the eutrophication of many freshwaters and coastal environments, phytoplankton blooms have become a common phenomenon. This article uses a reaction-diffusion model to investigate the implications of mixing processes for the dynamics and species composition of phytoplankton blooms. The model ide

  3. Species dynamics in phytoplankton blooms : Incomplete mixing and competition for light

    NARCIS (Netherlands)

    Huisman, J.; van Oostveen, P.; Weissing, F.J.

    1999-01-01

    With the eutrophication of many freshwaters and coastal environments, phytoplankton blooms have become a common phenomenon. This article uses a reaction-diffusion model to investigate the implications of mixing processes for the dynamics and species composition of phytoplankton blooms. The model ide

  4. Potential risk of organic micropollutants on marine phytoplankton in the greater North Sea: integration of modelling and experimental approaches

    OpenAIRE

    Everaert, G.

    2015-01-01

    A complex chemical cocktail, with unknown composition and concentrations, is present in marine waters. Although the awareness of the vulnerability of marine ecosystems to pollution induced changes increased, the ecotoxicological effects of chemical pollutants on marine ecosystems are poorly understood. Even in intensively monitored regions such as the North Sea, current knowledge of the ecotoxicological effects of chemicals is limited to few (priority) substances and few (model) species (disc...

  5. Ecological niches of open ocean phytoplankton taxa

    DEFF Research Database (Denmark)

    Brun, Philipp Georg; Vogt, Meike; Payne, Mark;

    2015-01-01

    We characterize the realized ecological niches of 133 phytoplankton taxa in the open ocean based on observations from the MAREDAT initiative and a statistical species distribution model (MaxEnt). The models find that the physical conditions (mixed layer depth, temperature, light) govern large...... conditions in the open ocean. Our estimates of the realized niches roughly match the predictions of Reynolds' C-S-R model for the global ocean, namely that taxa classified as nutrient stress tolerant have niches at lower nutrient and higher irradiance conditions than light stress tolerant taxa. Yet...

  6. Lidar and CTIPe model studies of the fast amplitude growth with altitude of the diurnal temperature "tides" in the Antarctic winter lower thermosphere and dependence on geomagnetic activity

    Science.gov (United States)

    Fong, Weichun; Chu, Xinzhao; Lu, Xian; Chen, Cao; Fuller-Rowell, Timothy J.; Codrescu, Mihail; Richmond, Arthur D.

    2015-02-01

    Four years of lidar observations at McMurdo reveal that the fast amplitude growth with altitude of diurnal temperature tides from 100 to 110 km during Antarctic winters, exceeding that of the freely propagating tides from the lower atmosphere, increases in strength with the Kp magnetic activity index. Simulations with the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model reproduce the lidar observations and exhibit concentric ring structures of diurnal amplitudes encircling the south geomagnetic pole and overlapping the auroral zone. These findings point to a magnetospheric source origin. Mechanistic studies using CTIPe show that the adiabatic cooling/heating associated with Hall ion drag is the dominant source of this feature, while Joule heating is a minor contributor due to the counteraction by Joule-heating-induced adiabatic cooling. The sum of total dynamical effects and Joule heating explains ~80% of the diurnal amplitudes. Auroral particle heating, lower atmosphere tides, and direct solar heating have minor contributions.

  7. Sugars in Antarctic aerosol

    Science.gov (United States)

    Barbaro, Elena; Kirchgeorg, Torben; Zangrando, Roberta; Vecchiato, Marco; Piazza, Rossano; Barbante, Carlo; Gambaro, Andrea

    2015-10-01

    The processes and transformations occurring in the Antarctic aerosol during atmospheric transport were described using selected sugars as source tracers. Monosaccharides (arabinose, fructose, galactose, glucose, mannose, ribose, xylose), disaccharides (sucrose, lactose, maltose, lactulose), alcohol-sugars (erythritol, mannitol, ribitol, sorbitol, xylitol, maltitol, galactitol) and anhydrosugars (levoglucosan, mannosan and galactosan) were measured in the Antarctic aerosol collected during four different sampling campaigns. For quantification, a sensitive high-pressure anion exchange chromatography was coupled with a single quadrupole mass spectrometer. The method was validated, showing good accuracy and low method quantification limits. This study describes the first determination of sugars in the Antarctic aerosol. The total mean concentration of sugars in the aerosol collected at the "Mario Zucchelli" coastal station was 140 pg m-3; as for the aerosol collected over the Antarctic plateau during two consecutive sampling campaigns, the concentration amounted to 440 and 438 pg m-3. The study of particle-size distribution allowed us to identify the natural emission from spores or from sea-spray as the main sources of sugars in the coastal area. The enrichment of sugars in the fine fraction of the aerosol collected on the Antarctic plateau is due to the degradation of particles during long-range atmospheric transport. The composition of sugars in the coarse fraction was also investigated in the aerosol collected during the oceanographic cruise.

  8. Estimating the Budgets of Nutrients for Phytoplankton Bloom in the Central Yellow Sea Using a Modified Lower Tropic Ecosystem Model

    Institute of Scientific and Technical Information of China (English)

    YUAN Chengyi; WANG Yuheng; WEI Hao

    2014-01-01

    A modified lower trophic ecosystem model (NEMURO) is coupled with a three-dimensional hydrodynamic model for an application in the central Yellow Sea. The model is used to simulate the horizontal distributions and annual cycles of chlorophyll-a and nutrients with results consistent with historical observations. Generally, during the winter background and spring bloom periods, the exchange with neighboring waters constitutes the primary sources of nutrients. Howerver, during the winter background period, the input of silicate from the layer deeper than 50 m is the most important source that contributes up to 60%to the total sources. Dur-ing the spring bloom period, the transport across the thermocline makes significant contribution to the input of phosphate and silicate. During the post spring bloom period, the relative contribution of relevant processes varies for different nutrients. For ammonium, atmospheric deposition, excretion of zooplankton and decomposition of particulate and dissolved nitrogen make similar contributions. For phosphate and silicate, the dominant input is the transport across the thermocline, accounting for 62% and 68% of the total sources, respectively. The N/P ratio averaged annually and over the whole southern Yellow Sea is up to 51.8, indicating the potential of P limitation in this region. The important influence of large scale sea water circulation is revealed by both the estimated fluxes and the corresponding N/P ratio of nutrients across a section linking the northeastern bank of the Changjiang River and Cheju Island. During the winter background period, the input of nitrate, ammonium, phosphate and silicate by the Yellow Sea Warm Current is estimated to be 4.6×1010, 2.3×1010, 2.0×109 and 1.2×1010 mol, respectively.

  9. A radiative transfer model for remote sensing of laser induced fluorescence of phytoplankton in non-homogeneous turbid water

    Science.gov (United States)

    Venable, D. D.

    1983-01-01

    A semi-analytic Monte Carlo simulation methodology (SALMON) was discussed. This simulation technique is particularly well suited for addressing fundamental radiative transfer problems in oceanographic LIDAR (optical radar), and also provides a framework for investigating the effects of environmental factors on LIDAR system performance. The simulation model was extended for airborne laser fluorosensors to allow for inhomogeneities in the vertical distribution of constituents in clear sea water. Results of the simulations for linearly varying step concentrations of chlorophyll are presented. The SALMON technique was also employed to determine how the LIDAR signals from an inhomogeneous media differ from those from homogeneous media.

  10. Optimization and Modeling of Enzymatic Hydrolysis Process for Antarctic Krill%南极磷虾酶解工艺优化及模型建立

    Institute of Scientific and Technical Information of China (English)

    吕传萍; 李学英; 杨宪时; 郭全友

    2011-01-01

    In the present work,alcalase was identified as the most suitable enzyme for enzymatic hydrolysis of Antarctic krill among 7 commonly used enzymes based on simultaneous consideration of chloroacetic acid-nitrogen soluble index(TCA-NSI) and degree of hydrolysis(DH).In order to optimize the hydrolysis of Antarctic krill by alcalase,the effects of the hydrolysis conditions enzyme dosage,substrate concentration,pH,temperature and hydrolysis time on TCA-NSI and DH were studied by one-factor-at-a-time and orthogonal rotary composite design methods.Two regression models with TCA-NSI or DH as a function of each hydrolysis condition were established.The optimal process conditions for hydrolyzing Antarctic krill with alcalase were 50.7 ℃ hydrolysis temperature,pH 8.01,3010 U/g alcalase dosage and 239 min hydrolysis time.Under the optimal conditions,the TCA-NSI and DH were 73.02% and 42.33%,respectively.Meanwhile,peptides with an average length of 2.36 and a molecular mass of 277.9 were obtained.%以短肽得率(trichloroacetic acid-nitrogen soluble index,TCA-NSI)和水解度(degree of hydrolysis,DH)为指标,从7种常用酶中选出Alcalase酶作为酶解南极磷虾的最适酶。对Alcalase酶水解南极磷虾的酶用量、底物浓度、pH值、温度和时间5个因素进行单因素试验和正交旋转组合试验,建立TCA-NSI和DH与各因素的回归模型;在此基础上,结合实际生产确定Alcalase酶水解南极磷虾的最适工艺为温度50.7℃、pH8.01、加酶量3010U/g、时间239min,此时TCA-NSI值为73.02%,DH值为42.33%,短肽平均肽链长(peptide chain long,PCL)为2.36,平均相对分子质量为277.9。

  11. Disassembling iron availability to phytoplankton

    Directory of Open Access Journals (Sweden)

    Yeala eShaked

    2012-04-01

    Full Text Available The bioavailability of iron to microorganisms and its underlying mechanisms have far reaching repercussions to many natural systems and diverse fields of research, including ocean biogeochemistry, carbon cycling and climate, harmful algal blooms, soil and plant research, bioremediation, pathogenesis and medicine. Within the framework of ocean sciences, short supply and restricted bioavailability of Fe to phytoplankton is thought to limit primary production and curtail atmospheric CO2 drawdown in vast ocean regions. Yet a clear-cut definition of bioavailability remains elusive, with elements of iron speciation and kinetics, phytoplankton physiology, light, temperature and microbial interactions, to name a few, all intricately intertwined into this concept. Here, in a synthesis of published and new data, we attempt to disassemble the complex concept of iron bioavailability to phytoplankton by individually exploring some of its facets. We distinguish between the fundamentals of bioavailability - the acquisition of Fe-substrate by phytoplankton - and added levels of complexity involving interactions among organisms, iron and ecosystem processes. We first examine how phytoplankton acquire free and organically-bound iron, drawing attention to the pervasiveness of the reductive uptake pathway in both prokaryotes and eukaryotes. Turning to acquisition rates, we propose to view the availability of various Fe-substrates to phytoplankton as spectrum rather than an absolute all or nothing. We then demonstrate the use of uptake rate constants to make comparisons across different studies, organisms, Fe compounds and environments, and for gauging the contribution of various Fe substrates to phytoplankton growth in situ. Last, we describe the influence of aquatic microorganisms on iron chemistry and fate by way of organic complexation and bio-mediated redox transformations and examine the bioavailability of these bio-modified Fe species.

  12. Comparative roles of upwelling and glacial iron sources in Ryder Bay, coastal western Antarctic Peninsula

    OpenAIRE

    Annett, Amber; Skiba, Marta; Henley, Sian; Venables, Hugh J.; Meredith, Michael P.; Statham, Peter; Ganeshram, Raja

    2015-01-01

    Iron (Fe) is an essential micronutrient for phytoplankton, and is scarce in many regions including the open Southern Ocean. The western Antarctic Peninsula (WAP), an important source region of Fe to the wider Southern Ocean, is also the fastest warming region of the Southern Hemisphere. The relative importance of glacial versus marine Fe sources is currently poorly constrained, hindering projections of how changing oceanic circulation, productivity, and glacial dynamics may affect the balance...

  13. Polar stratospheric clouds in the 1998-2003 Antarctic vortex: Microphysical modeling and Polar Ozone and Aerosol Measurement (POAM) III observations

    Science.gov (United States)

    Benson, C. M.; Drdla, K.; Nedoluha, G. E.; Shettle, E. P.; Alfred, J.; Hoppel, K. W.

    2006-09-01

    The Integrated Microphysics and Aerosol Chemistry on Trajectories (IMPACT) model is used to study polar stratospheric cloud (PSC) formation and evolution in the Antarctic vortex. The model is applied to individual air parcel trajectories driven by UK Met Office (UKMO) wind and temperature fields. The IMPACT model calculates the parcel microphysics, including the formation and sedimentation of ice, nitric acid trihydrate (NAT), sulfuric acid tetrahydrate (SAT), and supercooled ternary solution (STS) aerosols. Model results are validated by comparison with data obtained by the Polar Ozone and Aerosol Measurement (POAM) III solar occultation instrument and are examined for 6 years of POAM data (1998-2003). Comparisons of POAM water vapor and aerosol extinction measurements to the model results help to constrain three microphysical parameters influencing the formation and growth of both type I and type II PSCs. Principally, measurements of aerosol extinction prove to be valuable in differentiating model runs; the relationship of aerosol extinction to temperature is determined by the various particle types as they form and grow. Comparison of IMPACT calculations of this relationship to POAM measurements suggests that the initial fraction of nuclei available for heterogeneous NAT freezing is approximately 0.02% of all aerosols. Constraints are also placed on the accommodation coefficient of ice and the NAT-ice lattice compatibility. However, these two parameters have similar effects on the extinction-temperature relationship, and thus a range of values are permissible for each.

  14. Global dynamics of the Antarctic ice sheet

    NARCIS (Netherlands)

    Oerlemans, J.

    2002-01-01

    The total mass budget of the Antarctic ice sheet is studied with a simple axi-symmetrical model. The ice-sheet has a parabolic profile resting on a bed that slopes linearly downwards from the centre of the ice sheet into the ocean. The mean ice velocity at the grounding line is assumed to be proport

  15. Techniques for Quantifying Phytoplankton Biodiversity

    Science.gov (United States)

    Johnson, Zackary I.; Martiny, Adam C.

    2015-01-01

    The biodiversity of phytoplankton is a core measurement of the state and activity of marine ecosystems. In the context of historical approaches, we review recent major advances in the technologies that have enabled deeper characterization of the biodiversity of phytoplankton. In particular, high-throughput sequencing of single loci/genes, genomes, and communities (metagenomics) has revealed exceptional phylogenetic and genomic diversity whose breadth is not fully constrained. Other molecular tools—such as fingerprinting, quantitative polymerase chain reaction, and fluorescence in situ hybridization—have provided additional insight into the dynamics of this diversity in the context of environmental variability. Techniques for characterizing the functional diversity of community structure through targeted or untargeted approaches based on RNA or protein have also greatly advanced. A wide range of techniques is now available for characterizing phytoplankton communities, and these tools will continue to advance through ongoing improvements in both technology and data interpretation.

  16. Phytoplankton size class derived from phytoplankton absorption and chlorophyll-a concentrations in the northern South China Sea

    Institute of Scientific and Technical Information of China (English)

    WANG Guoqing; CAO Wenxi; WANG Guifen; ZHOU Wen

    2013-01-01

    A previously developed model was modified to derive three phytoplankton size classes (micro-,nano-,and pico-phytoplankton) from the overall chlorophyll-a concentration,assuming that each class has a specific absorption coefficient.The modified model performed well using in-situ data from the northern South China Sea,and the results were reliable and accurate.The relative errors of the size-fractioned chlorophyll-a concentration for each size class were:micro-:21%,nano-:41%,pico-:26%,and nano+pico:23%.The model was then applied on ocean color remote sensing data to examine the distribution and variation of phytoplankton size classes in northern South China Sea on a large scale.

  17. Large ensemble modeling of the last deglacial retreat of the West Antarctic Ice Sheet: comparison of simple and advanced statistical techniques

    Science.gov (United States)

    Pollard, David; Chang, Won; Haran, Murali; Applegate, Patrick; DeConto, Robert

    2016-05-01

    A 3-D hybrid ice-sheet model is applied to the last deglacial retreat of the West Antarctic Ice Sheet over the last ˜ 20 000 yr. A large ensemble of 625 model runs is used to calibrate the model to modern and geologic data, including reconstructed grounding lines, relative sea-level records, elevation-age data and uplift rates, with an aggregate score computed for each run that measures overall model-data misfit. Two types of statistical methods are used to analyze the large-ensemble results: simple averaging weighted by the aggregate score, and more advanced Bayesian techniques involving Gaussian process-based emulation and calibration, and Markov chain Monte Carlo. The analyses provide sea-level-rise envelopes with well-defined parametric uncertainty bounds, but the simple averaging method only provides robust results with full-factorial parameter sampling in the large ensemble. Results for best-fit parameter ranges and envelopes of equivalent sea-level rise with the simple averaging method agree well with the more advanced techniques. Best-fit parameter ranges confirm earlier values expected from prior model tuning, including large basal sliding coefficients on modern ocean beds.

  18. Comparing past accumulation rate reconstructions in East Antarctic ice cores using 10Be, water isotopes and CMIP5-PMIP3 models

    Directory of Open Access Journals (Sweden)

    A. Cauquoin

    2015-03-01

    Full Text Available Ice cores are exceptional archives which allow us to reconstruct a wealth of climatic parameters as well as past atmospheric composition over the last 800 kyr in Antarctica. Inferring the variations in past accumulation rate in polar regions is essential both for documenting past climate and for ice core chronology. On the East Antarctic Plateau, the accumulation rate is so small that annual layers cannot be identified and accumulation rate is mainly deduced from the water isotopic composition assuming constant temporal relationships between temperature, water isotopic composition and accumulation rate. Such an assumption leads to large uncertainties on the reconstructed past accumulation rate. Here, we use high-resolution beryllium-10 (10Be as an alternative tool for inferring past accumulation rate for the EPICA Dome C ice core, in East Antarctica. We present a high-resolution 10Be record covering a full climatic cycle over the period 269 to 355 ka from Marine Isotope Stage (MIS 9 to 10, including a period warmer than pre-industrial (MIS 9.3 optimum. After correcting 10Be for the estimated effect of the palaeomagnetic field, we deduce that the 10Be reconstruction is in reasonably good agreement with EDC3 values for the full cycle except for the period warmer than present. For the latter, the accumulation is up to 13% larger (4.46 cm ie yr−1 instead of 3.95. This result is in agreement with the studies suggesting an underestimation of the deuterium-based accumulation for the optimum of the Holocene (Parrenin et al. 2007a. Using the relationship between accumulation rate and surface temperature from the saturation vapour relationship, the 10Be-based accumulation rate reconstruction suggests that the temperature increase between the MIS 9.3 optimum and present day may be 2.4 K warmer than estimated by the water isotopes reconstruction. We compare these reconstructions to the available model results from CMIP5-PMIP3 for a glacial and an

  19. Species-Specific Variations in the Nutritional Quality of Southern Ocean Phytoplankton in Response to Elevated pCO2

    Directory of Open Access Journals (Sweden)

    Cathryn Wynn-Edwards

    2014-06-01

    Full Text Available Increased seawater pCO2 has the potential to alter phytoplankton biochemistry, which in turn may negatively affect the nutritional quality of phytoplankton as food for grazers. Our aim was to identify how Antarctic phytoplankton, Pyramimonas gelidicola, Phaeocystis antarctica, and Gymnodinium sp., respond to increased pCO2. Cultures were maintained in a continuous culture setup to ensure stable CO2 concentrations. Cells were subjected to a range of pCO2 from ambient to 993 µatm. We measured phytoplankton response in terms of cell size, cellular carbohydrate content, and elemental, pigment and fatty acid composition and content. We observed few changes in phytoplankton biochemistry with increasing CO2 concentration which were species-specific and predominantly included differences in the fatty acid composition. The C:N ratio was unaffected by CO2 concentration in the three species, while carbohydrate content decreased in Pyramimonas gelidicola, but increased in Phaeocystis antarctica. We found a significant reduction in the content of nutritionally important polyunsaturated fatty acids in Pyramimonas gelidicola cultures under high CO2 treatment, while cellular levels of the polyunsaturated fatty acid 20:5ω3, EPA, in Gymnodinium sp. increased. These changes in fatty acid profile could affect the nutritional quality of phytoplankton as food for grazers, however, further research is needed to identify the mechanisms for the observed species-specific changes and to improve our ability to extrapolate laboratory-based experiments on individual species to natural communities.

  20. Methanol Production by a Broad Phylogenetic Array of Marine Phytoplankton.

    Science.gov (United States)

    Mincer, Tracy J; Aicher, Athena C

    2016-01-01

    Methanol is a major volatile organic compound on Earth and serves as an important carbon and energy substrate for abundant methylotrophic microbes. Previous geochemical surveys coupled with predictive models suggest that the marine contributions are exceedingly large, rivaling terrestrial sources. Although well studied in terrestrial ecosystems, methanol sources are poorly understood in the marine environment and warrant further investigation. To this end, we adapted a Purge and Trap Gas Chromatography/Mass Spectrometry (P&T-GC/MS) method which allowed reliable measurements of methanol in seawater and marine phytoplankton cultures with a method detection limit of 120 nanomolar. All phytoplankton tested (cyanobacteria: Synechococcus spp. 8102 and 8103, Trichodesmium erythraeum, and Prochlorococcus marinus), and Eukarya (heterokont diatom: Phaeodactylum tricornutum, coccolithophore: Emiliania huxleyi, cryptophyte: Rhodomonas salina, and non-diatom heterokont: Nannochloropsis oculata) produced methanol, ranging from 0.8-13.7 micromolar in culture and methanol per total cellular carbon were measured in the ranges of 0.09-0.3%. Phytoplankton culture time-course measurements displayed a punctuated production pattern with maxima near early stationary phase. Stabile isotope labeled bicarbonate incorporation experiments confirmed that methanol was produced from phytoplankton biomass. Overall, our findings suggest that phytoplankton are a major source of methanol in the upper water column of the world's oceans. PMID:26963515

  1. Application of a laser fluorometer for discriminating phytoplankton species

    Science.gov (United States)

    Chen, Peng; Pan, Delu; Mao, Zhihua

    2015-04-01

    A portable laser-induced fluorescence system for discriminating phytoplankton species has been developed. It consists of a high pulsed repetition frequency (10-kHz) microchip laser at 405 nm, a reflective fluorescent probe and a broadband micro spectrometer. The measured fluorescent spectra were overlapped by various fluorescent components, and were then decomposed by a bi-Gaussian mixture model. A spectral shape description index was designed to characterize fluorescent spectral shapes for descriminating the phytoplankton species cultured in our laboratory. Using clustering analysis, the samples of eight phytoplankton species belonging to two divisions of Bacillariophyta and Dinophyta were divided into six categories: 1) Chaetoceros debilis, Thalassiosira rotula; 2) Prorocentrum donghaiense, Prorocentrum dentatum; 3) Gymnodinium simplex; 4) Alexandrium tamarense; 5) Karenia mikimotoi; and 6) Akashiwo sanguinea. The phytoplankton species belonging to Bacillariophyta were well separated from those belonging to Dinophyta. In addition, the phytoplankton species belonging to Dinophyta were successfully distinguished from each other at genus level. The portable system is expected to be used both in vivo and in the field.

  2. A glimpse into the future composition of marine phytoplankton communities

    Directory of Open Access Journals (Sweden)

    Esteban eAcevedo-Trejos

    2014-07-01

    Full Text Available It is expected that climate change will have significant impacts on ecosystems. Most model projections agree that the ocean will experience stronger stratification and less nutrient supply from deep waters. These changes will likely affect marine phytoplankton communities and will thus impact on the higher trophic levels of the oceanic food web. The potential consequences of future climate change on marine microbial communities can be investigated and predicted only with the help of mathematical models. Here we present the application of a model that describes aggregate properties of marine phytoplankton communities and captures the effects of a changing environment on their composition and adaptive capacity. Specifically, the model describes the phytoplankton community in terms of total biomass, mean cell size, and functional diversity. The model is applied to two contrasting regions of the Atlantic Ocean (tropical and temperate and is tested under two emission scenarios: SRES A2 or ``business as usual'' and SRES B1 or ``local utopia''. We find that all three macroecological properties will decline during the next century in both regions, although this effect will be more pronounced in the temperate region. Being consistent with previous model predictions, our results show that a simple trait-based modelling framework represents a valuable tool for investigating how phytoplankton communities may reorganize under a changing climate.

  3. Phytoplankton of the Tisa River

    OpenAIRE

    Ržaničanin Ana M.; Cvijan Mirko V.; Krizmanić Jelena

    2005-01-01

    Investigation of the Tisa River phytoplankton community was carried out directly after the cyanide spill in 2000. The investigation took place near Bečej from February of 2000 to January of 2001. We observed 374 taxa from eight algal divisions. The highest biodiversity was recorded among the divisions Chlorophyta and Bacillariophyta.

  4. Phytoplankton of the Tisa River

    Directory of Open Access Journals (Sweden)

    Ržaničanin Ana M.

    2005-01-01

    Full Text Available Investigation of the Tisa River phytoplankton community was carried out directly after the cyanide spill in 2000. The investigation took place near Bečej from February of 2000 to January of 2001. We observed 374 taxa from eight algal divisions. The highest biodiversity was recorded among the divisions Chlorophyta and Bacillariophyta.

  5. Regional genetic diversity patterns in Antarctic hairgrass (Deschampsia antartica Desv.)

    NARCIS (Netherlands)

    van de Wouw, M.J.; Van Dijk, P.J.; Huiskes, A.H.L.

    2008-01-01

    Aim To determine patterns in diversity of a major Antarctic plant species, including relationships of Antarctic populations with those outside the Antarctic zone. Location Antarctic Peninsula, Maritime Antarctica, sub-Antarctic islands, Falkland Islands and South America. Methods Amplified fragment

  6. A seasonal diary of phytoplankton in the North Atlantic

    DEFF Research Database (Denmark)

    Lindemann, Christian; St. John, Michael

    2014-01-01

    In recent years new biological and physical controls have been suggested to drive phytoplankton bloom dynamics in the North Atlantic. A better understanding of the mechanisms driving primary production has potentially important implications for the understanding of the biological carbon pump, as it...... are not mutually exclusive, but rather complementary. Thus, moving beyond the “single mechanism” point of view, here we present an integrated conceptual model of the physical and biological controls on phytoplankton dynamics in the North Atlantic. Further we believe that the acclimation of...... physiological rates can play an important role in mediating phytoplankton dynamics. Thus, this view emphasizes the occurrence of multiple controls and relates their variations in impact to climate change...

  7. Relative importance of nutrient inputs from streams and the sea entrance for phytoplankton dynamics in a shallow estuary - insights from 3D model simulations

    DEFF Research Database (Denmark)

    Timmermann, Karen; Gustafsson, Karin; Markager, Svend Stiig

    Danish estuaries are highly eutrophic due to high N and P inputs from local streams and a general increase in nutrient concentrations in the Baltic Sea region. Recovery plans have been implemented to reduce local loadings. A key issue for these plans is the relative importance of local sources...... the relative contribution to phytoplankton growth from nutrients originating from local sources and from the Baltic Sea outflow, respectively, which constituted the open boundary. Nutrient reduction scenarios were performed to asses the potential effects of reducing nutrient loadings from different sources...

  8. Latitudinal phytoplankton distribution and the neutral theory of biodiversity

    KAUST Repository

    Chust, Guillem

    2012-11-16

    Recent studies have suggested that global diatom distributions are not limited by dispersal, in the case of both extant species and fossil species, but rather that environmental filtering explains their spatial patterns. Hubbell\\'s neutral theory of biodiversity provides a framework in which to test these alternatives. Our aim is to test whether the structure of marine phytoplankton (diatoms, dinoflagellates and coccolithophores) assemblages across the Atlantic agrees with neutral theory predictions. We asked: (1) whether intersite variance in phytoplankton diversity is explained predominantly by dispersal limitation or by environmental conditions; and (2) whether species abundance distributions are consistent with those expected by the neutral model. Location: Meridional transect of the Atlantic (50° N-50° S). Methods: We estimated the relative contributions of environmental factors and geographic distance to phytoplankton composition using similarity matrices, Mantel tests and variation partitioning of the species composition based upon canonical ordination methods. We compared the species abundance distribution of phytoplankton with the neutral model using Etienne\\'s maximum-likelihood inference method. Results: Phytoplankton communities are slightly more determined by niche segregation (24%), than by dispersal limitation and ecological drift (17%). In 60% of communities, the assumption of neutrality in species\\' abundance distributions could not be rejected. In tropical zones, where oceanic gyres enclose large stable water masses, most communities showed low species immigration rates; in contrast, we infer that communities in temperate areas, out of oligotrophic gyres, have higher rates of species immigration. Conclusions: Phytoplankton community structure is consistent with partial niche assembly and partial dispersal and drift assembly (neutral processes). The role of dispersal limitation is almost as important as habitat filtering, a fact that has been

  9. Antarctic Tourism and Maritime Heritage

    OpenAIRE

    Basberg, Bjørn L.

    2010-01-01

    Maritime activities in the Antarctic region date back to the eighteenth century. They evolved from exploration and discoveries to commercial enterprises, especially sealing, whaling and fishing. Antarctic tourism is a much more recent phenomenon, developing mainly from the 1950s and 1960s. Today over 40,000 tourists visit the Antarctic annually, most of them on cruise ships. This essay reviews the historical development of this tourism. The focus is on how maritime heritage has been treated a...

  10. River Flow Control on the Phytoplankton Dynamics of Chesapeake Bay

    Institute of Scientific and Technical Information of China (English)

    YU Qingyun; WANG You; TANG Xuexi; LI Ming

    2013-01-01

    Recent observations support an emerging paradigm that climate variability dominates nutrient enrichment in costal ecosystems,which can explain seasonal and inter-annual variability of phytoplankton community composition,biomass (Chl-a),and primary production (PP).In this paper,we combined observation and modeling to investigate the regulation of phytoplankton dynamics in Chesapeake Bay.The year we chose is 1996 that has high river runoff and is usually called a ‘wet year’.A 3-D physical-biogeochemical model based on ROMS was developed to simulate the seasonal cycle and the regional distributions of phytoplankton biomass and primary production in Chesapeake Bay.Based on the model results,NO3 presents a strong contrast to the river nitrate load during spring and the highest concentration in the bay reaches around 80mmol N m3.Compared with the normal year,phytoplankton bloom in spring of 1996 appears in lower latitudes with a higher concentration.Quantitative comparison between the modeled and observed seasonal averaged dissolved inorganic nitrogen concentrations shows that the model produces reliable results.The correlation coefficient r2 for all quantities exceeds 0.95,and the skill parameter for the four seasons is all above 0.95.

  11. Antarctic science preserve polluted

    Science.gov (United States)

    Simarski, Lynn Teo

    Geophysicists are alarmed at the electromagnetic pollution of a research site in the Antarctic specifically set aside to study the ionosphere and magnetosphere. A private New Zealand communications company called Telecom recently constructed a satellite ground station within the boundaries of this Site of Special Scientific Interest (SSSI), protected since the mid-1970s. The placement of a commercial facility within this site sets an ominous precedent not only for the sanctity of other SSSIs, but also for Specially Protected Areas—preserves not even open to scientific research, such as certain penguin rookeries.The roughly rectangular, one-by-one-half mile site, located at Arrival Heights not far from McMurdo Station, is one of a number of areas protected under the Antarctic treaty for designated scientific activities. Many sites are set aside for geological or biological research, but this is the only one specifically for physical science.

  12. Measurements of 36Cl in Antarctic meteorites and Antarctic ice using a Van de Graaff accelerator

    International Nuclear Information System (INIS)

    Cosmic-ray produced 36Cl(tsub(1/2) = 3.0 X 105 years) has been measured in four Antarctic meteorites and one sample of Antarctic ice using a tandem Van de Graaff accelerator as an ultrasensitive mass spectrometer with the extremely low background level of 36Cl/Cl -16. Results from this ion counting technique (applied here to extraterrestrial materials for the first time) are used to support a two-stage irradiation model for the Yamato-7301and Allan Hills-76008 meteorites and to show a long terrestrial age (0.7 +- 0.1 m.y.) for Allan Hills-77002. Yamato-7304 has a terrestrial age of less than 0.1 m.y. The 36Cl content of the Antarctic ice sample from the Yamato Mountain area implies that the age of the ice cap at this site is less than one 36Cl half-life. (Auth.)

  13. Influence of Seawater Temperature on Phytoplankton Growth in Jiaozhou Bay, China

    Institute of Scientific and Technical Information of China (English)

    杨东方; 高振会; 陈豫; 王培刚; 孙培艳

    2004-01-01

    The phytoplankton reproduction capacity (PRC), as a new concept regarding chlorophyll-a and primary production (PP) is described. PRC is different from PP, carbon assimilation number (CAN) or photosynthetic rate (PB). PRC quantifies phytoplankton growth with a special consideration of the effect of seawater temperature. Observation data in Jiaozhou Bay, Qingdao, China, collected from May 1991 to February 1994 were used to analyze the horizontal distribution and seasonal variation of the PRC in Jiaozhou Bay in order to determine the characteristics, dynamic cycles and trends of phytoplankton growth in Jiaozhou Bay; and to develop a corresponding dynamic model of seawater temperature vs. PRC. Simulation curves showed that seawater temperature has a dual function of limiting and enhancing PRC. PRC's periodicity and fluctuation are similar to those of the seawater temperature. Nutrient silicon in Jiaozhou Bay satisfies phytoplankton growth from June 7 to November 3. When nutrients N, P and Si satisfy the phytoplankton growth and solar irradiation is sufficient, the PRC would reflect the influence of seawater temperature on phytoplankton growth. Moreover, the result quantitatively explains the scenario of one-peak or two-peak phytoplankton reproduction in Jiaozhou Bay, and also quantitatively elucidates the internal mechanism of the one- or two-peak phytoplankton reproduction in the global marine areas.

  14. Pronounced daily succession of phytoplankton, archaea and bacteria following a spring bloom.

    Science.gov (United States)

    Needham, David M; Fuhrman, Jed A

    2016-01-01

    Marine phytoplankton perform approximately half of global carbon fixation, with their blooms contributing disproportionately to carbon sequestration(1), and most phytoplankton production is ultimately consumed by heterotrophic prokaryotes(2). Therefore, phytoplankton and heterotrophic community dynamics are important in modelling carbon cycling and the impacts of global change(3). In a typical bloom, diatoms dominate initially, transitioning over several weeks to smaller and motile phytoplankton(4). Here, we show unexpected, rapid community variation from daily rRNA analysis of phytoplankton and prokaryotic community members following a bloom off southern California. Analysis of phytoplankton chloroplast 16S rRNA demonstrated ten different dominant phytoplankton over 18 days alone, including four taxa with animal toxin-producing strains. The dominant diatoms, flagellates and picophytoplankton varied dramatically in carbon export potential. Dominant prokaryotes also varied rapidly. Euryarchaea briefly became the most abundant organism, peaking over a few days to account for about 40% of prokaryotes. Phytoplankton and prokaryotic communities correlated better with each other than with environmental parameters. Extending beyond the traditional view of blooms being controlled primarily by physics and inorganic nutrients, these dynamics imply highly heterogeneous, continually changing conditions over time and/or space and suggest that interactions among microorganisms are critical in controlling plankton diversity, dynamics and fates. PMID:27572439

  15. Comment on "Patterns of diversity in marine phytoplankton"

    NARCIS (Netherlands)

    J. Huisman

    2010-01-01

    Barton et al. (Reports, 19 March 2010, p. 1509) argued that stable conditions enable neutral coexistence of many phytoplankton species in the tropical oceans, whereas seasonal variation causes low biodiversity in subpolar oceans. However, their model prediction is not robust. A minor deviation from

  16. Phytoplankton community characteristics in the coastal waters of the southeastern Arabian Sea Phytoplankton community characteristics in the coastal waters of the southeastern Arabian Sea

    Institute of Scientific and Technical Information of China (English)

    MINU P; SHAJU S S; MUHAMED ASHRAF P; MEENAKUMARI B

    2014-01-01

    Remote sensing applications are important in the fisheries sector and efforts were on to improve the predic-tions of potential fishing zones using ocean color. The present study was aimed to investigate the phyto-plankton dynamics and their absorption properties in the coastal waters of the southeastern Arabian Sea in different seasons during the year 2010 to 2011. The region exhibited 73 genera of phytoplankton from 19 orders and 41 families. The numerical abundance of phytoplankton varied from 14.235×103 to 55.075×106 cells/L. Centric diatoms dominated in the region and the largest family identified was Thalassiosiraceae with main genera asSkeletonemaspp.,Planktionellaspp.andThalassiosiraspp. Annual variations in abun-dance of phytoplankton showed a typical one-peak cycle, with the highest recorded during premonsoon season and the lowest during monsoon season. The species diversity index of phytoplankton exhibited low diversity during monsoon season. Phytoplankton with pigments Chlorophylla, Chlorophyllb, Chlorophyll c, peridinin, diadinoxanthin, fucoxanthin,β-carotene and phycoerythrobilin dominated in these waters. The knowledge on phytoplankton dynamics in coastal waters of the southeastern Arabian Sea forms a key parameter in bio-optical models of pigments and productivity and for the interpretation of remotely sensed ocean color data.

  17. Antarctic, Sub-Antarctic and cold temperate echinoid database

    Directory of Open Access Journals (Sweden)

    Benjamin Pierrat

    2012-06-01

    Full Text Available This database includes spatial data of Antarctic, Sub-Antarctic and cold temperate echinoid distribution (Echinodermata: Echinoidea collected during many oceanographic campaigns led in the Southern Hemisphere from 1872 to 2010. The dataset lists occurrence data of echinoid distribution south of 35°S latitude, together with information on taxonomy (from species to genus level, sampling sources (cruise ID, sampling dates, ship names and sampling sites (geographic coordinates and depth. Echinoid occurrence data were compiled from the Antarctic Echinoid Database (David et al., 2005a, which integrates records from oceanographic cruises led in the Southern Ocean until 2003. This database has been upgraded to take into account data from oceanographic cruises led after 2003. The dataset now reaches a total of 6160 occurrence data that have been checked for systematics reliability and consistency. It constitutes today the most complete database on Antarctic and Sub-Antarctic echinoids.

  18. Margalef's mandala and phytoplankton bloom strategies

    Science.gov (United States)

    Wyatt, Timothy

    2014-03-01

    Margalef's mandala maps phytoplankton species into a phase space defined by turbulence (A) and nutrient concentrations (Ni); these are the hard axes. The permutations of high and low A and high and low Ni divide the space into four domains. Soft axes indicate some ecological dynamics. A main sequence shows the normal course of phytoplankton succession; the r-K axis of MacArthur and Wilson runs parallel to it. An alternative successional sequence leads to the low A-high Ni domain into which many red tide species are mapped. Astronomical and biological time are implicit. A mathematical transformation of the mandala (rotation) links it to the classical bloom models of Sverdrup (time) and Kierstead and Slobodkin (space).Both rarity and the propensity to form red tides are considered to be species characters, meaning that maximum population abundance can be a target of natural selection. Equally, both the unpredictable appearance of bloom species and their short-lived appearances may be species characters. There may be a correlation too between these features and long-lived dormant stages in the life-cycle; then the vegetative planktonic phase is the 'weak link' in the life-cycle. Red tides are thus due to species which have evolved suites of traits which result in specific demographic strategies.

  19. Partitioning the Relative Importance of Phylogeny and Environmental Conditions on Phytoplankton Fatty Acids.

    Directory of Open Access Journals (Sweden)

    Aaron W E Galloway

    Full Text Available Essential fatty acids (EFA, which are primarily generated by phytoplankton, limit growth and reproduction in diverse heterotrophs. The biochemical composition of phytoplankton is well-known to be governed both by phylogeny and environmental conditions. Nutrients, light, salinity, and temperature all affect both phytoplankton growth and fatty acid composition. However, the relative importance of taxonomy and environment on algal fatty acid content has yet to be comparatively quantified, thus inhibiting predictions of changes to phytoplankton food quality in response to global environmental change. We compiled 1145 published marine and freshwater phytoplankton fatty acid profiles, consisting of 208 species from six major taxonomic groups, cultured in a wide range of environmental conditions, and used a multivariate distance-based linear model to quantify the total variation explained by each variable. Our results show that taxonomic group accounts for 3-4 times more variation in phytoplankton fatty acids than the most important growth condition variables. The results underscore that environmental conditions clearly affect phytoplankton fatty acid profiles, but also show that conditions account for relatively low variation compared to phylogeny. This suggests that the underlying mechanism determining basal food quality in aquatic habitats is primarily phytoplankton community composition, and allows for prediction of environmental-scale EFA dynamics based on phytoplankton community data. We used the compiled dataset to calculate seasonal dynamics of long-chain EFA (LCEFA; ≥C20 ɷ-3 and ɷ-6 polyunsaturated fatty acid concentrations and ɷ-3:ɷ-6 EFA ratios in Lake Washington using a multi-decadal phytoplankton community time series. These analyses quantify temporal dynamics of algal-derived LCEFA and food quality in a freshwater ecosystem that has undergone large community changes as a result of shifting resource management practices, highlighting

  20. A turbulence-induced switch in phytoplankton swimming behavior

    Science.gov (United States)

    Carrara, Francesco; Sengupta, Anupam; Stocker, Roman

    2015-11-01

    Phytoplankton, unicellular photosynthetic organisms that form the basis of life in aquatic environments, are frequently exposed to turbulence, which has long been known to affect phytoplankton fitness and species succession. Yet, mechanisms by which phytoplankton may adapt to turbulence have remained unknown. Here we present a striking behavioral response of a motile species - the red-tide-producing raphidophyte Heterosigma akashiwo - to hydrodynamic cues mimicking those experienced in ocean turbulence. In the absence of turbulence, H. akashiwo exhibits preferential upwards swimming (`negative gravitaxis'), observable as a strong accumulation of cells at the top of an experimental container. When cells were exposed to overturning in an automated chamber - representing a minimum experimental model of rotation by Kolmogorov-scale turbulent eddies - the population robustly split in two nearly equi-abundant subpopulations, one swimming upward and one swimming downward. Microscopic observations at the single-cell level showed that the behavioral switch was accompanied by a rapid morphological change. A mechanistic model that takes into account cell shape confirms that modulation of morphology can alter the hydrodynamic stress distribution over the cell body, which, in turn, triggers the observed switch in phytoplankton migration direction. This active response to fluid flow, whereby microscale morphological changes influence ocean-scale migration dynamics, could be part of a bet-hedging strategy to maximize the chances of at least a fraction of the population evading high-turbulence microzones.

  1. State of Climate 2011 - Global Ocean Phytoplankton

    Science.gov (United States)

    Siegel, D. A.; Antoine, D.; Behrenfeld, M. J.; d'Andon, O. H. Fanton; Fields, E.; Franz, B. A.; Goryl, P.; Maritorena, S.; McClain, C. R.; Wang, M.; Yoder, J. A.

    2012-01-01

    Phytoplankton photosynthesis in the sun lit upper layer of the global ocean is the overwhelmingly dominant source of organic matter that fuels marine ecosystems. Phytoplankton contribute roughly half of the global (land and ocean) net primary production (NPP; gross photosynthesis minus plant respiration) and phytoplankton carbon fixation is the primary conduit through which atmospheric CO2 concentrations interact with the ocean s carbon cycle. Phytoplankton productivity depends on the availability of sunlight, macronutrients (e.g., nitrogen, phosphorous), and micronutrients (e.g., iron), and thus is sensitive to climate-driven changes in the delivery of these resources to the euphotic zone

  2. Transcriptomics and comparative analysis of three antarctic notothenioid fishes.

    Directory of Open Access Journals (Sweden)

    Seung Chul Shin

    Full Text Available For the past 10 to 13 million years, Antarctic notothenioid fish have undergone extraordinary periods of evolution and have adapted to a cold and highly oxygenated Antarctic marine environment. While these species are considered an attractive model with which to study physiology and evolutionary adaptation, they are poorly characterized at the molecular level, and sequence information is lacking. The transcriptomes of the Antarctic fishes Notothenia coriiceps, Chaenocephalus aceratus, and Pleuragramma antarcticum were obtained by 454 FLX Titanium sequencing of a normalized cDNA library. More than 1,900,000 reads were assembled in a total of 71,539 contigs. Overall, 40% of the contigs were annotated based on similarity to known protein or nucleotide sequences, and more than 50% of the predicted transcripts were validated as full-length or putative full-length cDNAs. These three Antarctic fishes shared 663 genes expressed in the brain and 1,557 genes expressed in the liver. In addition, these cold-adapted fish expressed more Ub-conjugated proteins compared to temperate fish; Ub-conjugated proteins are involved in maintaining proteins in their native state in the cold and thermally stable Antarctic environments. Our transcriptome analysis of Antarctic notothenioid fish provides an archive for future studies in molecular mechanisms of fundamental genetic questions, and can be used in evolution studies comparing other fish.

  3. The Molecular Ecophysiology of Programmed Cell Death in Marine Phytoplankton

    Science.gov (United States)

    Bidle, Kay D.

    2015-01-01

    Planktonic, prokaryotic, and eukaryotic photoautotrophs (phytoplankton) share a diverse and ancient evolutionary history, during which time they have played key roles in regulating marine food webs, biogeochemical cycles, and Earth's climate. Because phytoplankton represent the basis of marine ecosystems, the manner in which they die critically determines the flow and fate of photosynthetically fixed organic matter (and associated elements), ultimately constraining upper-ocean biogeochemistry. Programmed cell death (PCD) and associated pathway genes, which are triggered by a variety of nutrient stressors and are employed by parasitic viruses, play an integral role in determining the cell fate of diverse photoautotrophs in the modern ocean. Indeed, these multifaceted death pathways continue to shape the success and evolutionary trajectory of diverse phytoplankton lineages at sea. Research over the past two decades has employed physiological, biochemical, and genetic techniques to provide a novel, comprehensive, mechanistic understanding of the factors controlling this key process. Here, I discuss the current understanding of the genetics, activation, and regulation of PCD pathways in marine model systems; how PCD evolved in unicellular photoautotrophs; how it mechanistically interfaces with viral infection pathways; how stress signals are sensed and transduced into cellular responses; and how novel molecular and biochemical tools are revealing the impact of PCD genes on the fate of natural phytoplankton assemblages.

  4. Stardust in Antarctic Micrometeorites

    Energy Technology Data Exchange (ETDEWEB)

    Yada, Toru; Floss, Christine; Stadermann, Frank J.; Zinner, E.; Nakamura, T.; Noguchi, T.; Lea, Alan S.

    2008-03-07

    We report the discovery of presolar silicate, oxide (hibonite) and (possibly) SiC grains from four Antarctic micrometeorites. The oxygen isotopic compositions of the eighteen presolar silicate (and one oxide) grains found are consistent with those observed previously in primitive meteorites and interplanetary dust particles, and indicate origins in oxygen-rich red giant or asymptotic giant branch stars. Four grains with anomalous C isotopic compositions were also detected. 12C/13C as well as Si ratios are similar to those of mainstream SiC grains; the N isotopic composition of one grain is also consistent with a mainstream SiC classification. Presolar silicate grains were found in three of the seven AMMs studied, and are heterogeneously distributed within these micrometeorites. Fourteen of the 18 presolar silicate grains and 3 of the 4 C-anomalous grains were found within one AMM, T98G8. The presence of magnesiowüstite, which forms mainly through the decomposition of carbonates, in AMMs without presolar silicates, and its absence in the presolar silicate-bearing micrometeorites, suggests that parent body processes (specifically aqueous alteration) may determine the presence or absence of presolar silicates in Antarctic micrometeorites.

  5. Direct Effect of Carbon Dioxide Concentration on Phytoplankton Community Structure in the Ross Sea, Antarctica

    Science.gov (United States)

    Riesselman, C. R.; Tortell, P. D.; Payne, C. D.; Dunbar, R. B.; Ditullio, G. R.

    2006-12-01

    As the largest high-nutrient low-chlorophyll (HNLC) region on the planet, the Southern Ocean plays a critical role in global biogeochemical cycling and climate modulation. Primary productivity and phytoplankton community structure in the waters surrounding Antarctica have demonstrated unique sensitivity to small changes in major and trace element availability and vertical mixing. However, the capacity of changing atmospheric CO2 to restructure Antarctic phytoplankton communities has only recently been proposed. During the austral summer of 2005-2006, the "Controls on Ross Sea Algal Community Structure" (CORSACS) project performed an integrated series of shipboard incubations coupled with polynya water column sampling designed to investigate the interplay of iron, light, and CO2 levels as determinants of primary production and phytoplankton community structure. Results from the CORSACS CO2 manipulation incubation experiment demonstrate substantial shifts in the taxonomic distribution of phytoplankton exposed to an experimental CO2 gradient. Triplicate semi-continuous culture bottles were bubbled with air mixtures containing 100, 370, and 800 ppm CO2, designed to approximate bloom conditions under glacial, modern, and projected future levels of carbon dioxide. At the conclusion of the 18-day incubation, the 100 ppm community was dominated by the small, finely silicified pennate diatom Pseudonitzschia subcurvata, while the abundance of larger, colonial Chaetoceros species increased significantly in the 800 ppm community. These results represent the first evidence that perturbations in atmospheric CO2 have the potential to reorganize phytoplankton community structure in the Southern Ocean, and have implications for both the glacial productivity paradox and the future of polar trophic structure.

  6. Satellite magnetic anomalies of the Antarctic crust

    Directory of Open Access Journals (Sweden)

    D. E. Alsdorf

    2000-06-01

    Full Text Available Spatially and temporally static crustal magnetic anomalies are contaminated by static core field effects above spherical harmonic degree 12 and dynamic, large-amplitude external fields. To extract crustal magnetic anomalies from the measurements of NASA's Magsat mission, we separate crustal signals from both core and external field effects. In particular, we define Magsat anomalies relative to the degree 11 field and use spectral correlation theory to reduce them for external field effects. We obtain a model of Antarctic crustal thickness by comparing the region's terrain gravity effects to free-air gravity anomalies derived from the Earth Gravity Model 1996 (EGM96. To separate core and crustal magnetic effects, we obtain the pseudo-magnetic effect of the crustal thickness variations from their gravity effect via Poisson's theorem for correlative potentials. We compare the pseudo-magnetic effect of the crustal thickness variations to field differences between degrees 11 and 13 by spectral correlation analysis. We thus identify and remove possible residual core field effects in the Magsat anomalies relative to the degree 11 core field. The resultant anomalies reflect possible Antarctic contrasts due both to crustal thickness and intracrustal variations of magnetization. In addition, they provide important constraints on the geologic interpretation of aeromagnetic survey data, such as are available for the Weddell Province. These crustal anomalies also may be used to correct for long wavelength errors in regional compilations of near-surface magnetic survey data. However, the validity of these applications is limited by the poor quality of the Antarctic Magsat data that were obtained during austral Summer and Fall when south polar external field activity was maximum. Hence an important test and supplement for the Antarctic crustal Magsat anomaly map will be provided by the data from the recently launched Ørsted mission, which will yield coverage

  7. Metazoan Parasites of Antarctic Fishes.

    Science.gov (United States)

    Oğuz, Mehmet Cemal; Tepe, Yahya; Belk, Mark C; Heckmann, Richard A; Aslan, Burçak; Gürgen, Meryem; Bray, Rodney A; Akgül, Ülker

    2015-06-01

    To date, there have been nearly 100 papers published on metazoan parasites of Antarctic fishes, but there has not yet been any compilation of a species list of fish parasites for this large geographic area. Herein, we provide a list of all documented occurrences of monogenean, cestode, digenean, acanthocephalan, nematode, and hirudinean parasites of Antarctic fishes. The list includes nearly 250 parasite species found in 142 species of host fishes. It is likely that there are more species of fish parasites, which are yet to be documented from Antarctic waters.

  8. Why marine phytoplankton calcify

    Science.gov (United States)

    Monteiro, Fanny M.; Bach, Lennart T.; Brownlee, Colin; Bown, Paul; Rickaby, Rosalind E. M.; Poulton, Alex J.; Tyrrell, Toby; Beaufort, Luc; Dutkiewicz, Stephanie; Gibbs, Samantha; Gutowska, Magdalena A.; Lee, Renee; Riebesell, Ulf; Young, Jeremy; Ridgwell, Andy

    2016-01-01

    Calcifying marine phytoplankton—coccolithophores— are some of the most successful yet enigmatic organisms in the ocean and are at risk from global change. To better understand how they will be affected, we need to know “why” coccolithophores calcify. We review coccolithophorid evolutionary history and cell biology as well as insights from recent experiments to provide a critical assessment of the costs and benefits of calcification. We conclude that calcification has high energy demands and that coccolithophores might have calcified initially to reduce grazing pressure but that additional benefits such as protection from photodamage and viral/bacterial attack further explain their high diversity and broad spectrum ecology. The cost-benefit aspect of these traits is illustrated by novel ecosystem modeling, although conclusive observations remain limited. In the future ocean, the trade-off between changing ecological and physiological costs of calcification and their benefits will ultimately decide how this important group is affected by ocean acidification and global warming. PMID:27453937

  9. Optical assessment of phytoplankton nutrient depletion

    DEFF Research Database (Denmark)

    Heath, M.R.; Richardson, Katherine; Kiørboe, Thomas

    1990-01-01

    The ratio of light absorption at 480 and 665 nm by 90% acetone extracts of marine phytoplankton pigments has been examined as a potential indicator of phytoplankton nutritional status in both laboratory and field studies. The laboratory studies demonstrated a clear relationship between nutritional...

  10. Phytoplankton productivity quantified from chlorophyll fluorescence

    DEFF Research Database (Denmark)

    Hancke, Kasper; Dalsgaard, Tage; Sejr, Mikael Kristian;

    Phytoplankton are the main food source for marine life, and accurate uantification of its productivity is essential for understanding how marine food webs function. As a novel non-invasive technology, chlorophyll fluorescence can be used to assess in situ primary production in phytoplankton...

  11. Modelos conceptuales de abundancia de fitoplancton asociados a la heterogeneidad espacial en el Embalse Rapel (Chile central Conceptual models of phytoplankton abundance associated to spatial heterogeneity at the Rapel reservoir (central Chile

    Directory of Open Access Journals (Sweden)

    GINGER MARTÍNEZ

    2003-06-01

    El Muro, la mayor variabilidad fue explicada por la concentración de compuestos nitrogenados, siendo el nitrato particularmente importante en el sector Alhué y el amonio en el sector El Muro. Estos resultados sugieren un control diferencial de la abundancia fitoplanctónica asociada a los diferentes sectores del embalse. Mientras que en el sector Las Balsas predominaría un control externo generado por la descarga de los tributarios, en la estación El Muro se postula un control interno y producido por la generación in situ de amonio. La significativa asociación a nitrato y nitrógeno orgánico detectada en la estación Alhué indicaría un control doble en la generación del patrón fitoplanctónicoHeterogeneous morphology generates abundance patterns and a differential response of the planktonic assemblages in regulated aquatic systems. This is the case at the Rapel reservoir (34º10' S, 71º29' W. A longitudinal morphoedaphic gradient and localized hydrodynamic conditions produce spatial complexity in this type-dendritic basin, that has been proposed as probable causal mechanism of the main diferences in phytoplankton abundance among areas inside of the reservoir. In this study, mechanisms and conceptual models of phytoplankton abundance are proposed, describing algae distribution patterns in three reservoir areas: Las Balsas, Alhué and El Muro. Also, the main predictive variables were identified which lead to propose a specific functioning model in each reservoir area. A data base published was used in order to obtain phytoplankton total abundance and physical and chemical variables from each station sampling that represent the reservoir areas, including the Confluencia area localized between Las Balsas and El Muro areas. Cluster and principal components analysis were applied in order to describe the spatial pattern and a multiple linear regression analysis was utilized to identify predictive variables in each sampling station. Results showed two significant

  12. OSIRIS observations of a tongue of NOx in the lower stratosphere at the Antarctic vortex edge: comparison with a high-resolution simulation from the Global Environmental Multiscale (GEM) model

    Energy Technology Data Exchange (ETDEWEB)

    Sioris, C.E.; McLinden, C.A.; Rochon, Y.J.; McElroy, C.T. [Environment Canada, Toronto, ON (Canada). Atmospheric Science and Technology Directorate; Chabrillat, S. [Belgian Inst. for Space Aeronomy, Brussels (Belgium); Haley, C.S. [York Univ., Toronto, ON (Canada); Menard, R.; Charron, M. [Environment Canada, Dorval, ON (Canada). Atmospheric Science and Technology Directorate

    2007-11-15

    An optical spectrograph and infrared imager system (OSIRIS) aboard the Odin satellite measures limb-scattered sunlight in the 280 to 810 nm range. This paper addressed the challenge of interpreting nitrogen dioxide (NO{sub 2}) profile observations in the polar lower stratosphere. Interpretations of these profile observations can be facilitated by first converting the measurements to NO{sub x} using a photochemical model in order to compare directly with simulated NO{sub x} from a 3-dimensional chemical transport model such as the Global Environmental Multiscale (GEM) model. In this study, GEM was used to simulate a tongue of NO{sub x} observed by OSIRIS as it circulated inside the Antarctic vortex edge. The objective was to clarify one of several OSIRIS observations of enhanced lower stratospheric NO{sub 2} in the Antarctic in early austral spring. Another objective was to demonstrate the variability in lower stratospheric NO{sub x} at polar latitudes due to dynamical processes. Selected NOx profiles of the Antarctic lower stratosphere inferred from OSIRIS NO{sub 2} observations were presented from the austral spring of 2003. A tongue of NOx at 100 hPa was observed, with a concentration typical of the middle stratosphere. GEM simulations revealed that this small-scale tongue of NOx-rich air descended into the lower stratosphere. The tongue was formed as a result of a Rossby wave breaking, transporting NOx from the pole, where larger concentrations had recently appeared, to the edge of the vortex. A detailed illustration of the 3-dimensional structure of the breaking wave was also presented. 17 refs., 1 tab., 10 figs.

  13. OSIRIS observations of a tongue of NOx in the lower stratosphere at the Antarctic vortex edge: comparison with a high-resolution simulation from the Global Environmental Multiscale (GEM) model

    International Nuclear Information System (INIS)

    An optical spectrograph and infrared imager system (OSIRIS) aboard the Odin satellite measures limb-scattered sunlight in the 280 to 810 nm range. This paper addressed the challenge of interpreting nitrogen dioxide (NO2) profile observations in the polar lower stratosphere. Interpretations of these profile observations can be facilitated by first converting the measurements to NOx using a photochemical model in order to compare directly with simulated NOx from a 3-dimensional chemical transport model such as the Global Environmental Multiscale (GEM) model. In this study, GEM was used to simulate a tongue of NOx observed by OSIRIS as it circulated inside the Antarctic vortex edge. The objective was to clarify one of several OSIRIS observations of enhanced lower stratospheric NO2 in the Antarctic in early austral spring. Another objective was to demonstrate the variability in lower stratospheric NOx at polar latitudes due to dynamical processes. Selected NOx profiles of the Antarctic lower stratosphere inferred from OSIRIS NO2 observations were presented from the austral spring of 2003. A tongue of NOx at 100 hPa was observed, with a concentration typical of the middle stratosphere. GEM simulations revealed that this small-scale tongue of NOx-rich air descended into the lower stratosphere. The tongue was formed as a result of a Rossby wave breaking, transporting NOx from the pole, where larger concentrations had recently appeared, to the edge of the vortex. A detailed illustration of the 3-dimensional structure of the breaking wave was also presented. 17 refs., 1 tab., 10 figs

  14. Phytoplankton variability in Lake Fraijanes, Costa Rica, in response to local weather variation.

    Science.gov (United States)

    Umaña-Villalobos, Gerardo

    2014-06-01

    Phytoplankton species show a variety in morphology which is the result of adaptations to pelagic life including responses to fluctuations in water column dynamics driven by weather conditions. This has been reported in the oceans and in Northern temperate lakes. In order to observe whether tropical freshwater phytoplankton responds to seasonal variation in weather, the weekly variation in temperature of the water column and phytoplankton composition was studied in Lake Fraijanes, Costa Rica, a shallow (6.2m) lake at 1 640m above sea level. A chain of data loggers for temperature was placed in the deepest point in the lake to register temperature every hour at four different depths, and phytoplankton samples were retrieved every week for a year. Additional monthly samples for nutrients were taken at two depths. Notwithstanding its shallowness, the lake developed a thermal gradient which kept the water column stratified for several months during dry season. Whole lake overturns occurred during cold spells with intense precipitation. Phytoplankton changed throughout the year mainly through a shift in dominant taxa. From September to February the lake was frequently mixed by rain storms and windy weather. At this time, phytoplankton was dominated by Chlorococcal green algae. From March to June, the lake was stratified and warmer. Phytoplankton became dominated by Cyanobateria, mainly colonial Chroococcales. The rainy season started again in May 2009. During June and July the lake started to mix intermittently during rain events and phytoplankton showed a brief increase in the contribution of Chlorococcales. These changes fitted well to a general model of phytoplankton succession based on functional groups identified according to their morphology and adaptations. PMID:25102633

  15. Isotopic shift for defining habitat exploitation by the Antarctic limpet Nacella concinna from rocky coastal habitats (Marian Cove, King George Island)

    Science.gov (United States)

    Choy, Eun Jung; Park, Hyun; Kim, Jeong-Hoon; Ahn, In-Young; Kang, Chang-Keun

    2011-05-01

    δ 13C and δ 15N of the Antarctic limpet Nacella concinna tissues and their potential food sources were used to determine their dietary origins and their movements between diverse habitats of intertidal and subtidal rocky shores and tide pools of Marian Cove, King George Island, Antarctica in the austral summer. δ 13C and δ 15N of the organic matter sources of epilithic microalgae, macroalgae and suspended particulate organic matter (SPOM) were readily distinguishable to discern their relative contribution to the limpet diets, with the most depleted values being found in SPOM and the most enriched in macroalgae. The limpets exhibited a spatial trend in distribution due to their seasonal migration, with smaller individuals in the subtidal zone compared with larger ones on the intertidal sites. The limpet isotopes had relatively broad ranges of δ 13C and δ 15N (-26.6 to -12.8‰ and 2.6-7.1‰, respectively), suggesting a dietary shift between habitats as well as size classes. The stable isotope ratios for each habitat seem likely to reflect the differing availabilities of the three potential food sources. Isotope mixing model results indicate a spatial shift in dietary mixture between habitats as well as limpet size classes. Epilithic microalgae and phytoplankton made great contributions to the diet of the subtidal limpets. Together with epilithic microalgae, macroalgae were significant contributors to the intertidal limpets where macroalgae were abundant. A higher contribution of macroalgae to the limpet diets was found in the tide pools. In contrast, while phytoplankton was an important food source for the limpet spat, a great dietary dependence on epilithic microalgae was found in the small-size limpets from the lower intertidal zone. Our results suggest that limpet grazing can determine microalgal and/or macroalgal abundance and coverage on the Antarctic rocky-shore ecosystem, and trophic structure of benthic food web can change along environmental

  16. A paleomagnetic study of the Antarctic Peninsula

    Science.gov (United States)

    Poblete, F.; Arriagada, C.; Roperch, P.

    2009-05-01

    In the Paleozoic, South America, South Africa and Antarctica were part of Gondwana. The Weddell Sea began to form at about 146 Ma, after rifting between the Antarctic Peninsula and southernmost South America. Much uncertainty still exists about the geometrical fit and subsequent drift history between Patagonia and Antarctica. Geophysical and geological data which describe the tectonic history are sparsely distributed and often of poor quality. During the last two years we have collected more than 1000 paleomagnetic samples from 70 sites at several localities (King George Island, Robert Island, Yankee Bay, Half Moon Island, Byers Peninsula and Snow Island) from the South Shetland Islands and Anderson Island in the northern tip of Antarctic Peninsula. Our main objective was to provide first-order constraints on latitudinal displacements and the amount of tectonic rotations as an essential test of published tectonic models. Paleomagnetic results were obtained from 50 sites. All samples from sites in volcanic and intrusive rocks have well-defined univectorial magnetizations. Unfortunately, all sites in late Paleozoic sediments have been remagnetized and the magnetizations are often unstable upon thermal demagnetization. Cretaceous and Cenozoic units display very little apparent polar wander. Results from intrusive rocks of expected Jurassic age do not confirm the expected relative rotation betwen the Antarctic Peninsula and East Antarctica. Further radiometric dating are needed to confirm the age of these units.

  17. Simulating the mass balance and salinity of Arctic and Antarctic sea ice. 1. Model description and validation

    OpenAIRE

    Vancoppenolle, M.; Fichefet, T.; Goosse, H.; S. Bouillon; Madec, G.; Maqueda, M. A. M.

    2009-01-01

    This paper is the first part of a twofold contribution dedicated to the new version of the Louvain-la-Neuve sea ice model LIM3. In this part, LIM3 is described and its results arc, compared with observations. LIM3 is a C-grid dynamic-thermodynamic model, including the representation of the subgrid-scale distributions of ice thickness, enthalpy, salinity and age. Brine entrapment and drainage as well as brine impact on ice thermodynamics are explicitly included. LIM3 is embedded into the ocean...

  18. Development of a model to assess masking potential for marine mammals by the use of air guns in Antarctic waters

    NARCIS (Netherlands)

    Wittekind, D.; Tougaard, J.; Stilz, P.; Dähne, M.; Clark, C.W.; Lucke, K.; Benda-Beckmann, A.M. von; Ainslie, M.A.; Siebert, U.

    2016-01-01

    We estimated the long-range effects of air gun array noise on marine mammal communication ranges in the Southern Ocean. Air gun impulses are subject to significant distortion during propagation, potentially resulting in a quasi- continuous sound. Propagation modeling to estimate the received wavefor

  19. Antarctic crabs: invasion or endurance?

    Science.gov (United States)

    Griffiths, Huw J; Whittle, Rowan J; Roberts, Stephen J; Belchier, Mark; Linse, Katrin

    2013-01-01

    Recent scientific interest following the "discovery" of lithodid crabs around Antarctica has centred on a hypothesis that these crabs might be poised to invade the Antarctic shelf if the recent warming trend continues, potentially decimating its native fauna. This "invasion hypothesis" suggests that decapod crabs were driven out of Antarctica 40-15 million years ago and are only now returning as "warm" enough habitats become available. The hypothesis is based on a geographically and spatially poor fossil record of a different group of crabs (Brachyura), and examination of relatively few Recent lithodid samples from the Antarctic slope. In this paper, we examine the existing lithodid fossil record and present the distribution and biogeographic patterns derived from over 16,000 records of Recent Southern Hemisphere crabs and lobsters. Globally, the lithodid fossil record consists of only two known specimens, neither of which comes from the Antarctic. Recent records show that 22 species of crabs and lobsters have been reported from the Southern Ocean, with 12 species found south of 60 °S. All are restricted to waters warmer than 0 °C, with their Antarctic distribution limited to the areas of seafloor dominated by Circumpolar Deep Water (CDW). Currently, CDW extends further and shallower onto the West Antarctic shelf than the known distribution ranges of most lithodid species examined. Geological evidence suggests that West Antarctic shelf could have been available for colonisation during the last 9,000 years. Distribution patterns, species richness, and levels of endemism all suggest that, rather than becoming extinct and recently re-invading from outside Antarctica, the lithodid crabs have likely persisted, and even radiated, on or near to Antarctic slope. We conclude there is no evidence for a modern-day "crab invasion". We recommend a repeated targeted lithodid sampling program along the West Antarctic shelf to fully test the validity of the "invasion hypothesis".

  20. Effect of high iron concentration enrichment on the phytoplankton in the Prydz Bay

    Institute of Scientific and Technical Information of China (English)

    张武昌; 孙松; 张永山; 扈传昱; 刘诚刚

    2004-01-01

    Shipboard iron enrichment phytoplankton incubations were carried out in the Prydz Bay, Antarctic, in January through to March 2002. Waters for the three incubations ( Exp 1,2 and 3 ) were collected from 20 m depth in three stations ( St. Ⅰ -1, Ⅶ-1 and Ⅶ-5 ), respectively. Although the nutrient concentrations in the surface waters of the three stations were consistently high, the Chl a concentrations varied considerably. Chl a concentrations in the 20 m depth of St. Ⅰ-1 and Ⅶ-1 werewas 2.35-2.65 for St. Ⅶ-5. There were six levels of enriched iron concentrations(control 5, 10, 20, 40 and 80 nM) in Exp 1 (6-29th, January) while three enriched iron levels (control 10 and 40 nM) were arranged in Exp 2 and 3 (both were from 20th February to 4 th March). The iron enrichments stimulated the phytoplankton growth and nutrient drawdown in Exp 1 and Exp 2. In Exp 3, phytoplankton growth and nutrient drawdown were at nearly the same rate in the control and iron enriched bottles. In Exp 1, Chl a concentrations in the bottles with 20, 40 and 80 nM iday, respectively, with a growth rate of 0.36-0.38 d-1. Chl a concentration in the day ( growth rate 0.27 d - 1 ). Phytoplankton growth rates in the control bottle and the bottle enriched with 5 nM iron were 0.13 and 0.16 d -1, respectively. In Exp 2, the Chl a growth rates were 0.13, 0.32 and 0.40 d-1 in the control bottle and bottles with 10 and 40 nM iron enrichments, respectively. It seems that 10 nM iron enrichment was not enough to stimulate the phytoplankton to reach their maximum growth rate. The result that the phytoplankton < 10 μm bloomed in Exp 1 and 2 was controversial to the "Ecumenical Iron Hypothesis" of Morel et al. ( 1991 ) that upon enrichment of iron, phytoplankton >10 μm would grow faster than phytoplankton<10 μm.

  1. Development of a Model to Assess Masking Potential for Marine Mammals by the Use of Air Guns in Antarctic Waters.

    Science.gov (United States)

    Wittekind, Dietrich; Tougaard, Jakob; Stilz, Peter; Dähne, Michael; Clark, Christopher W; Lucke, Klaus; von Benda-Beckmann, Sander; Ainslie, Michael A; Siebert, Ursula

    2016-01-01

    We estimated the long-range effects of air gun array noise on marine mammal communication ranges in the Southern Ocean. Air gun impulses are subject to significant distortion during propagation, potentially resulting in a quasi-continuous sound. Propagation modeling to estimate the received waveform was conducted. A leaky integrator was used as a hearing model to assess communication masking in three species due to intermittent/continuous air gun sounds. Air gun noise is most probably changing from impulse to continuous noise between 1,000 and 2,000 km from the source, leading to a reduced communication range for, e.g., blue and fin whales up to 2,000 km from the source. PMID:26611093

  2. A contribution toward understanding the biospherical significance of Antarctic ozone depletion

    Science.gov (United States)

    Lubin, Dan; Mitchell, Greg; Frederick, John E.; Alberts, Amy D.; Booth, C. R.; Lucas, Timothy; Neuschuler, David

    1992-01-01

    The paper presents and compares measurements of biologically active UV radiation made by the NSF scanning spectroradiometer (UV-monitor) at Palmer Station, Antarctica, during the Austral springs of 1988, 1989, and 1990. Column ozone abundance above Palmer Station is computed from these measurements using a multiple wavelength algorithm. Two contrasting action spectra are employed to estimate the biologically relevant dose from the spectral measurements: a standard weighting function for damage to DNA, and a new action spectrum representing the potential for photosynthesis inhibition in Antarctic phytoplankton. The former weights only UV-B wavelengths (280-320 nm) and gives the most weight to wavelengths shorter than 300 nm, while the latter includes large contributions out to 355 nm. Ozone abundances and dose-weighted irradiances provided by the NSF UV-monitor are used to derive the radiation amplification factors for both DNA- and phytoplankton-effective irradiance.

  3. Modelling the light absorption properties of particulate matter forming organic particles suspended in seawater.Part 1. Model description, classification of organic particles, and example spectra of the light absorption coefficient and the imaginary part of the refractive index of particulate matter for phytoplankton cells and phytoplankton-like particles

    Directory of Open Access Journals (Sweden)

    Bogdan Woźniak

    2005-06-01

    Full Text Available Data on organic substances in the sea are applied to distinguish hypothetical chemical classes and physical types of suspended particulate organic matter (POM in seawater. Spectra of the light absorption coefficients of particulate matter apm(λ and the imaginary refractive index n'p(λ, are assessed for some of these classes and types of POM in seawater, that is, for live phytoplankton cells and phytoplankton-like particles. The spectral characteristics of these coefficients are established and the probable ranges of variability of their absolute magnitudes defined on the basis of the mass-specific coefficients of light absorption by the various organic substances forming the particles. Also presented are mathematical relationships linking the coefficients apm(λ and n'p(λ for the various chemical classes of POM with their physical parameters, such as the relative contents of organic matter, water, air or some other gas. This article is part of a bio-optical study undertaken by the authors, the objective of which is to implement remote sensing techniques in the investigation of Baltic ecosystems (Woźniak et al. 2004.

  4. Investigating the Effect of Recruitment Variability on Length-Based Recruitment Indices for Antarctic Krill Using an Individual-Based Population Dynamics Model

    OpenAIRE

    Stéphane Thanassekos; Cox, Martin J.; Keith Reid

    2014-01-01

    Antarctic krill (Euphausia superba; herein krill) is monitored as part of an on-going fisheries observer program that collects length-frequency data. A krill feedback management programme is currently being developed, and as part of this development, the utility of data-derived indices describing population level processes is being assessed. To date, however, little work has been carried out on the selection of optimum recruitment indices and it has not been possible to assess the performance...

  5. An evaluation of the application of CHEMTAX to Antarctic coastal pigment data

    Science.gov (United States)

    Kozlowski, Wendy A.; Deutschman, Douglas; Garibotti, Irene; Trees, Charles; Vernet, Maria

    2011-04-01

    Presented is an evaluation of the application of CHEMTAX (CHEMical TAXonomy) to Antarctic coastal pigments collected along the western Antarctic Peninsula (wAP). Overall analytical error is Blooms during mid-summer (chlorophyll a concentrations >5 μg L -1) were dominated primarily by either diatoms or cryptomonads. Mixed flagellates can also be abundant and Pheaocystis spp. and prasinophytes are frequently present in low concentrations. Comparison with microscopy shows CHEMTAX to give superior results in identifying Pheaocystis spp. with favorable results for other groups. This analysis shows CHEMTAX to be a reliable and stable tool for providing estimations of the main phytoplankton taxa in wAP waters based on long-term data collected during a 12-year time series.

  6. Climate-induced changes in carbon and nitrogen cycling in the rapidly warming Antarctic coastal ocean

    OpenAIRE

    Henley, Sian Frances

    2013-01-01

    The western Antarctic Peninsula (WAP) is a hotspot of climatic and oceanographic change, with a 6°C rise in winter atmospheric temperatures and >1°C warming of the surface ocean since the 1950s. These trends are having a profound impact on the physical environment at the WAP, with widespread glacial retreat, a 40% decline in sea ice coverage and intensification of deep water upwelling. The main objective of this study is to assess the response of phytoplankton productivity to t...

  7. Ocean processes at the Antarctic continental slope.

    Science.gov (United States)

    Heywood, Karen J; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D; Queste, Bastien Y; Stevens, David P; Wadley, Martin; Thompson, Andrew F; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K; Smith, Walker

    2014-07-13

    The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean-atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system.

  8. Examination of silicate limitation of primary production in Jiaozhou Bay, China. I. Silicate being a limiting factor of phytoplankton primary production

    Science.gov (United States)

    Yang, Dong-Fang; Zhang, Jing; Lu, Ji-Bin; Gao, Zhen-Hui; Chen, Yu

    2002-09-01

    Jiaozhou Bay data collected from May 1991 to February 1994, in 12 seasonal investigations, and provided the authors by the Ecological Station of Jiaozhou Bay, were analyzed to determine the spatiotemporal variations in temperature, light, nutrients (NO{3/-}-N, NO{2/-}-N, NH{4/+}-N, SiO{3/2-}-Si, PO{4/3-}-P), phytoplankton, and primary production in Jiaozhou Bay. The results indicated that only silicate correlated well in time and space with, and had important effects on, the characteristics, dynamic cycles and trends of, primary production in Jiaozhou Bay. The authors developed a corresponding dynamic model of primary production and silicate and water temperature. Eq. (1) of the model shows that the primary production variation is controlled by the nutrient Si and affected by water temperature; that the main factor controlling the primary production is Si; that water temperature affects the composition of the structure of phytoplankton assemblage; that the different populations of the phytoplankton assemblage occupy different ecological niches for C, the apparent ratio of conversion of silicate in seawater into phytoplankton biomas and D, the coefficient of water temperature's effect on phytoplankton biomass. The authors researched the silicon source of Jiaozhou Bay, the biogeochemical sediment process of the silicon, the phytoplankton predominant species and the phytoplankton structure. The authors considered silicate a limiting factor of primary production in Jiaozhou Bay, whose decreasing concentration of silicate from terrestrial source is supposedly due to dilution by current and uptake by phytoplankton; quantified the silicate assimilated by phytoplankton, the intrinsic ratio of conversion of silicon into phytoplankton biomass, the proportion of silicate uptaken by phytoplankton and diluted by current; and found that the primary production of the phytoplankton is determined by the quantity of the silicate assimilated by them. The phenomenon of apparently high

  9. EXAMINATION OF SILICATE LIMITATION OF PRIMARY PRODUCTION IN JIAOZHOU BAY, CHINA Ⅰ. SILICATE BEING A LIMITING FACTOR OF PHYTOPLANKTON PRIMARY PRODUCTION

    Institute of Scientific and Technical Information of China (English)

    杨东方; 张经; 吕吉斌; 高振会; 陈豫

    2002-01-01

    Jiaozhou Bay data collected from May 1991 to February 1994, in 12 seasonal investigations, and provided the authors by the Ecological Station of Jiaozhou B ay, were analyzed to determine the spatiotemporal variations in temperature, light, nutrients (NO-3-N, NO-2-N, NH+4-N, SiO2-3-Si, PO3-4-P), phytoplankton, and primary production in Jiaozhou Bay. The results indicated that only silicate correlated well in time and space with, and had important effects on, the characteristics, dynamic cycles and trends of, primary production in Jiaozhou Bay. The authors developed a corresponding dynamic model of primary production and silicate and water temperature. Eq.(1) of the model shows that the primary production variation is controlled by the nutrient Si and affected by water temp erature; that the main factor controlling the primary production is Si; that water temper ature affects the composition of the structure of phytoplankton assemblage; that the different populations of the phytoplankton assemblage occupy different ecologica l niches for C, the apparent ratio of conversion of silicate in seawater into phytoplankton biomas and D, the coefficient of water temperature's effect on phytoplankton biomass. The authors researched the silicon source of Jiaozhou Bay , the biogeochemical sediment process of the silicon, the phytoplankton predominan t species and the phytoplankton structure. The authors considered silicate a limit ing factor of primary production in Jiaozhou Bay, whose decreasing concentration of silicate from terrestrial source is supposedly due to dilution by current and up take by phytoplankton; quantified the silicate assimilated by phytoplankton, the intrins ic ratio of conversion of silicon into phytoplankton biomass, the proportion of silicate uptaken by phytoplankton and diluted by current; and found that the primary production of the phytoplankton is determined by the quantity of the silicate assimilated by them. The phenomenon of apparently high plant

  10. EXAMINATION OF SILICATE LIMITATION OF PRIMARY PRODUCTION IN JIAOZHOU BAY, CHINA——I. SILICATE BEING A LIMITING FACTOR OF PHYTOPLANKTON PRIMARY PRODUCTION

    Institute of Scientific and Technical Information of China (English)

    杨东方; 张经; 吕吉斌; 高振会; 陈豫

    2002-01-01

    Jiaozhou Bay data collected from May 1991 to February 1994, in 12 seasonal investigations, and provided the authors by the Ecological Station of Jiaozhou Bay, were analyzed to determine the spatiotemporal variations in temperature, light, nutrients (NO3--N, NO2--N, NH4+-N, SIO32--Si, PO43--P), phytoplankton, and primary production in Jiaozhou Bay. The results indicated that only silicate correlated well in time and space with, and had important effects on, the characteristics, dynamic cycles and trends of, primary production in Jiaozhou Bay. The authors developed a corresponding dynamic model of primary production and silicate and water temperature. Eq. ( 1 ) of the model shows that the primary production variation is controlled by the nutrient Si and affected by water temperature; that the main factor controlling the primary production is Si; that water temperature affects the composition of the structure of phytoplankton assemblage; that the different populations of the phytoplankton assemblage occupy different ecological niches for C, the apparent ratio of conversion of silicate in seawater into phytoplankton biomas and D, the coefficient of water temperature's effect on phytoplankton biomass. The authors researched the silicon source of Jiaozhou Bay, the biogeochemical sediment process of the silicon, the phytoplankton predominant species and the phytoplankton structure. The authors considered silicate a limiting factor of primary production in Jiaozhou Bay, whose decreasing concentration of silicate from terrestrial source is supposedly due to dilution by current and uptake by phytoplankton; quantified the silicate assimilated by phytoplankton, the intrinsic ratio of conversion of silicon into phytoplankton biomass, the proportion of silicate uptaken by phytoplankton and diluted by current; and found that the primary production of the phytoplankton is determined by the quantity of the silicate assimilated by them. The phenomenon of apparently high plant

  11. Mapping and Assessing Variability in the Antarctic Marginal Ice Zone, the Pack Ice and Coastal Polynyas

    Science.gov (United States)

    Stroeve, Julienne; Jenouvrier, Stephanie

    2016-04-01

    Sea ice variability within the marginal ice zone (MIZ) and polynyas plays an important role for phytoplankton productivity and krill abundance. Therefore mapping their spatial extent, seasonal and interannual variability is essential for understanding how current and future changes in these biological active regions may impact the Antarctic marine ecosystem. Knowledge of the distribution of different ice types to the total Antarctic sea ice cover may also help to shed light on the factors contributing towards recent expansion of the Antarctic ice cover in some regions and contraction in others. The long-term passive microwave satellite data record provides the longest and most consistent data record for assessing different ice types. However, estimates of the amount of MIZ, consolidated pack ice and polynyas depends strongly on what sea ice algorithm is used. This study uses two popular passive microwave sea ice algorithms, the NASA Team and Bootstrap to evaluate the distribution and variability in the MIZ, the consolidated pack ice and coastal polynyas. Results reveal the NASA Team algorithm has on average twice the MIZ and half the consolidated pack ice area as the Bootstrap algorithm. Polynya area is also larger in the NASA Team algorithm, and the timing of maximum polynya area may differ by as much as 5 months between algorithms. These differences lead to different relationships between sea ice characteristics and biological processes, as illustrated here with the breeding success of an Antarctic seabird.

  12. Impact of ocean acidification on the structure of future phytoplankton communities

    Science.gov (United States)

    Dutkiewicz, Stephanie; Morris, J. Jeffrey; Follows, Michael J.; Scott, Jeffery; Levitan, Orly; Dyhrman, Sonya T.; Berman-Frank, Ilana

    2015-11-01

    Phytoplankton form the foundation of the marine food web and regulate key biogeochemical processes. These organisms face multiple environmental changes, including the decline in ocean pH (ocean acidification) caused by rising atmospheric pCO2 (ref. ). A meta-analysis of published experimental data assessing growth rates of different phytoplankton taxa under both ambient and elevated pCO2 conditions revealed a significant range of responses. This effect of ocean acidification was incorporated into a global marine ecosystem model to explore how marine phytoplankton communities might be impacted over the course of a hypothetical twenty-first century. Results emphasized that the differing responses to elevated pCO2 caused sufficient changes in competitive fitness between phytoplankton types to significantly alter community structure. At the level of ecological function of the phytoplankton community, acidification had a greater impact than warming or reduced nutrient supply. The model suggested that longer timescales of competition- and transport-mediated adjustments are essential for predicting changes to phytoplankton community structure.

  13. Lagrangian studies of phytoplankton growth and grazing relationships in a coastal upwelling ecosystem off Southern California

    Science.gov (United States)

    Landry, Michael R.; Ohman, Mark D.; Goericke, Ralf; Stukel, Michael R.; Tsyrklevich, Kate

    2009-12-01

    Experimental studies of phytoplankton growth and grazing processes were conducted in the coastal upwelling system off Point Conception, California to test the hypothesis that phytoplankton growth and grazing losses determine, to first order, the local dynamics of phytoplankton in the upwelling circulation. Eight experiments of 3-5 days each were conducted over the course of two cruises in May-June 2006 and April 2007 following the trajectories of satellite-tracked drifters. Rates of phytoplankton growth and microzooplankton grazing were determined by daily in situ dilution incubations at 8 depths spanning the euphotic zone. Mesozooplankton grazing was assessed by gut fluorescence analysis of animals collected from net tows through the euphotic zone. We compared directly the net rates of change observed for the ambient phytoplankton community to the net growth rates predicted from experimental determinations of each process rate. The resulting relationship accounted for 91% of the variability observed, providing strong support for the growth-grazing hypothesis. In addition, grazing by mesozooplankton was unexpectedly high and variable, driving a substantial positive to negative shift in phytoplankton net rate of change between years despite comparable environmental conditions and similar high growth rates and suggesting strong top-down control potential. The demonstrated agreement between net ambient and experimental community changes is an important point of validation for using field data to parameterize models. Data sets of this type may provide an important source of new information and rate constraints for developing better coupled biological-physical models of upwelling system dynamics.

  14. Diatom-specific highly branched isoprenoids as biomarkers in Antarctic consumers.

    Directory of Open Access Journals (Sweden)

    Aurélie Goutte

    Full Text Available The structure, functioning and dynamics of polar marine ecosystems are strongly influenced by the extent of sea ice. Ice algae and pelagic phytoplankton represent the primary sources of nutrition for higher trophic-level organisms in seasonally ice-covered areas, but their relative contributions to polar marine consumers remain largely unexplored. Here, we investigated the potential of diatom-specific lipid markers and highly branched isoprenoids (HBIs for estimating the importance of these two carbon pools in an Antarctic pelagic ecosystem. Using GC-MS analysis, we studied HBI biomarkers in key marine species over three years in Adélie Land, Antarctica: euphausiids (ice krill Euphausia crystallorophias and Antarctic krill E. superba, fish (bald notothens Pagothenia borchgrevinki and Antarctic silverfish Pleuragramma antarcticum and seabirds (Adélie penguins Pygoscelis adeliae, snow petrels Pagodroma nivea and cape petrels Daption capense. This study provides the first evidence of the incorporation of HBI lipids in Antarctic pelagic consumers. Specifically, a di-unsaturated HBI (diene of sea ice origin was more abundant in ice-associated species than in pelagic species, whereas a tri-unsaturated HBI (triene of phytoplanktonic origin was more abundant in pelagic species than in ice-associated species. Moreover, the relative abundances of diene and triene in seabird tissues and eggs were higher during a year of good sea ice conditions than in a year of poor ice conditions. In turn, the higher contribution of ice algal derived organic matter to the diet of seabirds was related to earlier breeding and higher breeding success. HBI biomarkers are a promising tool for estimating the contribution of organic matter derived from ice algae in pelagic consumers from Antarctica.

  15. Diatom-specific highly branched isoprenoids as biomarkers in Antarctic consumers.

    Science.gov (United States)

    Goutte, Aurélie; Cherel, Yves; Houssais, Marie-Noëlle; Klein, Vincent; Ozouf-Costaz, Catherine; Raccurt, Mireille; Robineau, Camille; Massé, Guillaume

    2013-01-01

    The structure, functioning and dynamics of polar marine ecosystems are strongly influenced by the extent of sea ice. Ice algae and pelagic phytoplankton represent the primary sources of nutrition for higher trophic-level organisms in seasonally ice-covered areas, but their relative contributions to polar marine consumers remain largely unexplored. Here, we investigated the potential of diatom-specific lipid markers and highly branched isoprenoids (HBIs) for estimating the importance of these two carbon pools in an Antarctic pelagic ecosystem. Using GC-MS analysis, we studied HBI biomarkers in key marine species over three years in Adélie Land, Antarctica: euphausiids (ice krill Euphausia crystallorophias and Antarctic krill E. superba), fish (bald notothens Pagothenia borchgrevinki and Antarctic silverfish Pleuragramma antarcticum) and seabirds (Adélie penguins Pygoscelis adeliae, snow petrels Pagodroma nivea and cape petrels Daption capense). This study provides the first evidence of the incorporation of HBI lipids in Antarctic pelagic consumers. Specifically, a di-unsaturated HBI (diene) of sea ice origin was more abundant in ice-associated species than in pelagic species, whereas a tri-unsaturated HBI (triene) of phytoplanktonic origin was more abundant in pelagic species than in ice-associated species. Moreover, the relative abundances of diene and triene in seabird tissues and eggs were higher during a year of good sea ice conditions than in a year of poor ice conditions. In turn, the higher contribution of ice algal derived organic matter to the diet of seabirds was related to earlier breeding and higher breeding success. HBI biomarkers are a promising tool for estimating the contribution of organic matter derived from ice algae in pelagic consumers from Antarctica. PMID:23418580

  16. Environmental contamination in Antarctic ecosystems.

    Science.gov (United States)

    Bargagli, R

    2008-08-01

    Although the remote continent of Antarctica is perceived as the symbol of the last great wilderness, the human presence in the Southern Ocean and the continent began in the early 1900s for hunting, fishing and exploration, and many invasive plant and animal species have been deliberately introduced in several sub-Antarctic islands. Over the last 50 years, the development of research and tourism have locally affected terrestrial and marine coastal ecosystems through fuel combustion (for transportation and energy production), accidental oil spills, waste incineration and sewage. Although natural "barriers" such as oceanic and atmospheric circulation protect Antarctica from lower latitude water and air masses, available data on concentrations of metals, pesticides and other persistent pollutants in air, snow, mosses, lichens and marine organisms show that most persistent contaminants in the Antarctic environment are transported from other continents in the Southern Hemisphere. At present, levels of most contaminants in Antarctic organisms are lower than those in related species from other remote regions, except for the natural accumulation of Cd and Hg in several marine organisms and especially in albatrosses and petrels. The concentrations of organic pollutants in the eggs of an opportunistic top predator such as the south polar skua are close to those that may cause adverse health effects. Population growth and industrial development in several countries of the Southern Hemisphere are changing the global pattern of persistent anthropogenic contaminants and new classes of chemicals have already been detected in the Antarctic environment. Although the Protocol on Environmental Protection to the Antarctic Treaty provides strict guidelines for the protection of the Antarctic environment and establishes obligations for all human activity in the continent and the Southern Ocean, global warming, population growth and industrial development in countries of the Southern

  17. Environmental contamination in Antarctic ecosystems.

    Science.gov (United States)

    Bargagli, R

    2008-08-01

    Although the remote continent of Antarctica is perceived as the symbol of the last great wilderness, the human presence in the Southern Ocean and the continent began in the early 1900s for hunting, fishing and exploration, and many invasive plant and animal species have been deliberately introduced in several sub-Antarctic islands. Over the last 50 years, the development of research and tourism have locally affected terrestrial and marine coastal ecosystems through fuel combustion (for transportation and energy production), accidental oil spills, waste incineration and sewage. Although natural "barriers" such as oceanic and atmospheric circulation protect Antarctica from lower latitude water and air masses, available data on concentrations of metals, pesticides and other persistent pollutants in air, snow, mosses, lichens and marine organisms show that most persistent contaminants in the Antarctic environment are transported from other continents in the Southern Hemisphere. At present, levels of most contaminants in Antarctic organisms are lower than those in related species from other remote regions, except for the natural accumulation of Cd and Hg in several marine organisms and especially in albatrosses and petrels. The concentrations of organic pollutants in the eggs of an opportunistic top predator such as the south polar skua are close to those that may cause adverse health effects. Population growth and industrial development in several countries of the Southern Hemisphere are changing the global pattern of persistent anthropogenic contaminants and new classes of chemicals have already been detected in the Antarctic environment. Although the Protocol on Environmental Protection to the Antarctic Treaty provides strict guidelines for the protection of the Antarctic environment and establishes obligations for all human activity in the continent and the Southern Ocean, global warming, population growth and industrial development in countries of the Southern

  18. Phytoplankton species composition, abundance and distribution in Fishing area 58 of Indian Ocean sector of Southern Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rathod, V.

    of different parameter at the Polar Front and Sun Antarctic regions. Polar Front Stations ( 1 – 13) Parameters Min. Max. Mean SD Nitrate (µ M) 7.80 24.1 15.21 4.06 Nitrite (µM) 0.01 0.4 0.17 0.12 Phosphate ( µM) 0.63 3.2 1.50 0.54 Silicate (µ M) 27...-96. 37 Kopczynska, E.E., Periodicity and composition of summer phytoplankton in Ezcurra Inlet, Admiral Bay, South Shetland Islands. Pol Polar Res, 1981,2, 55-70. 38 Kopczynska, E.E., Weber, L.H., El-Sayed, S.Z., Phytoplankton Species composition...

  19. How do sinking phytoplankton species manage to persist?

    OpenAIRE

    Huisman, J.; Arrayás, M.; Ebert, Ute; Sommeijer, Ben

    2001-01-01

    Phytoplankton requires light for photosynthesis, but most phytoplankton species are heavier than water and sink. How can these sinking species persist? Here we show, by means of an advection-diffusion-reaction equation of light-limited phytoplankton, that the answer lies in the turbulent motion of water that re-disperses phytoplankton over the vertical water column. More specifically, we show that there is a turbulence window sustaining sinking phytoplankton species. If turbulent diffusion is...

  20. Uncertainty Analysis of Phytoplankton Dynamics in Coastal Waters

    OpenAIRE

    Niu, L.

    2015-01-01

    There is an increasing concern about the interactions between phytoplankton and coastal ecosystems, especially on the negative effects from coastal eutrophication and phytoplankton blooms. As the key indicator of the coastal ecosystem, phytoplankton plays an important role in the whole impact-effect chain. Primary production by phytoplankton forms the basic link in the food-chain. A lot of effort has been paid to the investigation of phytoplankton dynamics on the basis of literature surveys, ...

  1. Quantifying the impact of submesoscale processes on the spring phytoplankton bloom in a turbulent upper ocean using a Lagrangian approach

    Science.gov (United States)

    Brody, Sarah R.; Lozier, M. Susan; Mahadevan, Amala

    2016-05-01

    The spring phytoplankton bloom in the subpolar North Atlantic and the mechanisms controlling its evolution and onset have important consequences for marine ecosystems and carbon cycling. Submesoscale mixed layer eddies (MLEs) play a role in the onset of the bloom by creating localized stratification and alleviating phytoplankton light limitation; however, the importance of MLEs for phytoplankton in a turbulent surface mixed layer has not yet been examined. We explore the effect of MLEs on phytoplankton by simulating their trajectories with Lagrangian particles subject to turbulent vertical displacements in an MLE-resolving model. By tracking the light exposure of the simulated phytoplankton, we find that MLEs can advance the timing of the spring bloom by 1 to 2 weeks, depending on surface forcing conditions. The onset of the bloom is linked with the onset of positive heat fluxes, whether or not MLEs are present.

  2. Spatial dynamics of a nutrient-phytoplankton system with toxic effect on phytoplankton

    DEFF Research Database (Denmark)

    Chakraborty, Subhendu; Tiwari, P. K.; Misra, A. K.;

    2015-01-01

    The production of toxins by some species of phytoplankton is known to have several economic, ecological, and human health impacts. However, the role of toxins on the spatial distribution of phytoplankton is not well understood. In the present study, the spatial dynamics of a nutrient-phytoplankto......The production of toxins by some species of phytoplankton is known to have several economic, ecological, and human health impacts. However, the role of toxins on the spatial distribution of phytoplankton is not well understood. In the present study, the spatial dynamics of a nutrient...

  3. Macroecological patterns in the distribution of marine phytoplankton

    DEFF Research Database (Denmark)

    Mousing, Erik Askov

    Marine phytoplankton are responsible for approximately half of the global total primary production. The photosynthesis they carry out sustains higher trophic levels in the marine ecosystem. Changes in phytoplankton community composition can have cascading effects on food web dynamics, total...... stratification limiting the flux of nutrients from the deep ocean). This affect has important implications for the global carbon cycle and should be included in future climate models. In manuscript II, changes in the mean cyst size of dinoflagellates are investigated in relation to temperature changes during...... in the 1970s. However, increasing silicate in the deep ocean over the same period has indicated that there is an overlooked source of silicate and has brought the paradigm of silica limitation into question. Here, it is shown that silicate-using protists became more diluted in the sediment after 1970...

  4. The spatial extent and dynamics of the Antarctic Cold Reversal

    Science.gov (United States)

    Pedro, Joel B.; Bostock, Helen C.; Bitz, Cecilia M.; He, Feng; Vandergoes, Marcus J.; Steig, Eric J.; Chase, Brian M.; Krause, Claire E.; Rasmussen, Sune O.; Markle, Bradley R.; Cortese, Giuseppe

    2016-01-01

    Antarctic ice cores show that a millennial-scale cooling event, the Antarctic Cold Reversal (14,700 to 13,000 years ago), interrupted the last deglaciation. The Antarctic Cold Reversal coincides with the Bølling-Allerød warm stage in the North Atlantic, providing an example of the inter-hemispheric coupling of abrupt climate change generally referred to as the bipolar seesaw. However, the ocean-atmosphere dynamics governing this coupling are debated. Here we examine the extent and expression of the Antarctic Cold Reversal in the Southern Hemisphere using a synthesis of 84 palaeoclimate records. We find that the cooling is strongest in the South Atlantic and all regions south of 40° S. At the same time, the terrestrial tropics and subtropics show abrupt hydrologic variations that are significantly correlated with North Atlantic climate changes. Our transient global climate model simulations indicate that the observed extent of Antarctic Cold Reversal cooling can be explained by enhanced northward ocean heat transport from the South to North Atlantic, amplified by the expansion and thickening of sea ice in the Southern Ocean. The hydrologic variations at lower latitudes result from an opposing enhancement of southward heat transport in the atmosphere mediated by the Hadley circulation. Our findings reconcile previous arguments about the relative dominance of ocean and atmospheric heat transports in inter-hemispheric coupling, demonstrating that the spatial pattern of past millennial-scale climate change reflects the superposition of both.

  5. The Antarctic ozone depletion caused by Erebus volcano gas emissions

    Science.gov (United States)

    Zuev, V. V.; Zueva, N. E.; Savelieva, E. S.; Gerasimov, V. V.

    2015-12-01

    Heterogeneous chemical reactions releasing photochemically active molecular chlorine play a key role in Antarctic stratospheric ozone destruction, resulting in the Antarctic ozone hole. Hydrogen chloride (HCl) is one of the principal components in these reactions on the surfaces of polar stratospheric clouds (PSCs). PSCs form during polar nights at extremely low temperatures (lower than -78 °C) mainly on sulfuric acid (H2SO4) aerosols, acting as condensation nuclei and formed from sulfur dioxide (SO2). However, the cause of HCl and H2SO4 high concentrations in the Antarctic stratosphere, leading to considerable springtime ozone depletion, is still not clear. Based on the NCEP/NCAR reanalysis data over the last 35 years and by using the NOAA HYSPLIT trajectory model, we show that Erebus volcano gas emissions (including HCl and SO2) can reach the Antarctic stratosphere via high-latitude cyclones with the annual average probability Pbarann. of at least ∼0.235 (23.5%). Depending on Erebus activity, this corresponds to additional annual stratospheric HCl mass of 1.0-14.3 kilotons (kt) and SO2 mass of 1.4-19.7 kt. Thus, Erebus volcano is the natural and powerful source of additional stratospheric HCl and SO2, and hence, the cause of the Antarctic ozone depletion, together with man-made chlorofluorocarbons.

  6. Evolution and ecology of antarctic sponges

    OpenAIRE

    Vargas Ramirez, Sergio

    2012-01-01

    Sponges are abundant and species-rich in Antarctic waters, and play important roles in the benthic ecosystems of the continent. The taxonomy of Antarctic sponges is, to some extent, well established, yet the phylogenetic relationships of this fauna remain unknown. Here, the first contributions to the knowledge of the evolution of Antarctic sponges are presented. A molecular phylogeny for the common Antarctic shelf glass sponge genus Rossella is provided. Based on nuclear and mitochondrial mar...

  7. Phytoplankton Monitoring Network (PMN) - Sampling Sites

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A qualitative collection of data that includes salinity, temperature, phytoplankton counts and abundance ratios obtained from surface tows in the estuarine and...

  8. Latitudinal variation in virus-induced mortality of phytoplankton across the North Atlantic Ocean.

    Science.gov (United States)

    Mojica, Kristina D A; Huisman, Jef; Wilhelm, Steven W; Brussaard, Corina P D

    2016-02-01

    Viral lysis of phytoplankton constrains marine primary production, food web dynamics and biogeochemical cycles in the ocean. Yet, little is known about the biogeographical distribution of viral lysis rates across the global ocean. To address this, we investigated phytoplankton group-specific viral lysis rates along a latitudinal gradient within the North Atlantic Ocean. The data show large-scale distribution patterns of different virus groups across the North Atlantic that are associated with the biogeographical distributions of their potential microbial hosts. Average virus-mediated lysis rates of the picocyanobacteria Prochlorococcus and Synechococcus were lower than those of the picoeukaryotic and nanoeukaryotic phytoplankton (that is, 0.14 per day compared with 0.19 and 0.23 per day, respectively). Total phytoplankton mortality (virus plus grazer-mediated) was comparable to the gross growth rate, demonstrating high turnover rates of phytoplankton populations. Virus-induced mortality was an important loss process at low and mid latitudes, whereas phytoplankton mortality was dominated by microzooplankton grazing at higher latitudes (>56°N). This shift from a viral-lysis-dominated to a grazing-dominated phytoplankton community was associated with a decrease in temperature and salinity, and the decrease in viral lysis rates was also associated with increased vertical mixing at higher latitudes. Ocean-climate models predict that surface warming will lead to an expansion of the stratified and oligotrophic regions of the world's oceans. Our findings suggest that these future shifts in the regional climate of the ocean surface layer are likely to increase the contribution of viral lysis to phytoplankton mortality in the higher-latitude waters of the North Atlantic, which may potentially reduce transfer of matter and energy up the food chain and thus affect the capacity of the northern North Atlantic to act as a long-term sink for CO2. PMID:26262815

  9. Latitudinal variation in virus-induced mortality of phytoplankton across the North Atlantic Ocean.

    Science.gov (United States)

    Mojica, Kristina D A; Huisman, Jef; Wilhelm, Steven W; Brussaard, Corina P D

    2016-02-01

    Viral lysis of phytoplankton constrains marine primary production, food web dynamics and biogeochemical cycles in the ocean. Yet, little is known about the biogeographical distribution of viral lysis rates across the global ocean. To address this, we investigated phytoplankton group-specific viral lysis rates along a latitudinal gradient within the North Atlantic Ocean. The data show large-scale distribution patterns of different virus groups across the North Atlantic that are associated with the biogeographical distributions of their potential microbial hosts. Average virus-mediated lysis rates of the picocyanobacteria Prochlorococcus and Synechococcus were lower than those of the picoeukaryotic and nanoeukaryotic phytoplankton (that is, 0.14 per day compared with 0.19 and 0.23 per day, respectively). Total phytoplankton mortality (virus plus grazer-mediated) was comparable to the gross growth rate, demonstrating high turnover rates of phytoplankton populations. Virus-induced mortality was an important loss process at low and mid latitudes, whereas phytoplankton mortality was dominated by microzooplankton grazing at higher latitudes (>56°N). This shift from a viral-lysis-dominated to a grazing-dominated phytoplankton community was associated with a decrease in temperature and salinity, and the decrease in viral lysis rates was also associated with increased vertical mixing at higher latitudes. Ocean-climate models predict that surface warming will lead to an expansion of the stratified and oligotrophic regions of the world's oceans. Our findings suggest that these future shifts in the regional climate of the ocean surface layer are likely to increase the contribution of viral lysis to phytoplankton mortality in the higher-latitude waters of the North Atlantic, which may potentially reduce transfer of matter and energy up the food chain and thus affect the capacity of the northern North Atlantic to act as a long-term sink for CO2.

  10. Prospects for surviving climate change in Antarctic aquatic species

    Directory of Open Access Journals (Sweden)

    Peck Lloyd S

    2005-06-01

    Full Text Available Abstract Maritime Antarctic freshwater habitats are amongst the fastest changing environments on Earth. Temperatures have risen around 1°C and ice cover has dramatically decreased in 15 years. Few animal species inhabit these sites, but the fairy shrimp Branchinecta gaini typifies those that do. This species survives up to 25°C daily temperature fluctuations in summer and passes winter as eggs at temperatures down to -25°C. Its annual temperature envelope is, therefore around 50°C. This is typical of Antarctic terrestrial species, which exhibit great physiological flexibility in coping with temperature fluctuations. The rapidly changing conditions in the Maritime Antarctic are enhancing fitness in these species by increasing the time available for feeding, growth and reproduction, as well as increasing productivity in lakes. The future problem these animals face is via displacement by alien species from lower latitudes. Such invasions are now well documented from sub-Antarctic sites. In contrast the marine Antarctic environment has very stable temperatures. However, seasonality is intense with very short summers and long winter periods of low to no algal productivity. Marine animals grow slowly, have long generation times, low metabolic rates and low levels of activity. They also die at temperatures between +5°C and +10°C. Failure of oxygen supply mechanisms and loss of aerobic scope defines upper temperature limits. As temperature rises, their ability to perform work declines rapidly before lethal limits are reached, such that 50% of populations of clams and limpets cannot perform essential activities at 2–3°C, and all scallops are incapable of swimming at 2°C. Currently there is little evidence of temperature change in Antarctic marine sites. Models predict average global sea temperatures will rise by around 2°C by 2100. Such a rise would take many Antarctic marine animals beyond their survival limits. Animals have 3 mechanisms for

  11. Regulating Antarctic Tourism and the Precautionary Principle

    NARCIS (Netherlands)

    Bastmeijer, C.J.; Roura, R.

    2004-01-01

    On the basis of an overview of the developments in Antarctic tourism since 1956, this current development note examines the issue of international regulation of Antarctic tourism. After discussing one of the main management issues in respect of Antarctic tourism ¿ the assessment and prevention of cu

  12. Variability in the Antarctic Marginal Ice Zone and Pack Ice in Observations and NCAR CESM

    Science.gov (United States)

    Stroeve, J. C.; Campbell, G. G.; Holland, M. M.; Landrum, L.

    2015-12-01

    Sea ice around Antarctica reached another record high extent in September 2014, recording a maximum extent of more than 20 million km2 for the first time since the modern satellite data record began in October 1978. This follows previous record maxima in 2012 and 2013, resulting in an overall increase in Antarctic September sea ice extent of 1.3% per decade since 1979. Several explanations have been put forward to explain the increasing trends, such as anomalous short-term wind patterns that both grow and spread out the ice, and freshening of the surface ocean layer from increased melting of floating ice from the continent. These positive trends in Antarctic sea ice are at odds with climate model forecasts that suggest the sea ice should be declining in response to increasing greenhouse gases and stratospheric ozone depletion. While the reasons for the increases in total extent remain poorly understood, it is likely that these changes are not just impacting the total ice extent, but also the distribution of pack ice, the marginal ice zone (MIZ) and polynyas, with important ramifications for phytoplankton productivity that in turn impact zooplankton, fish, sea birds and marine mammals. This study evaluates changes in the distribution of the pack ice, polynyas and the marginal ice zone around Antarctica from two sea ice algorithms, the NASA Team and the Bootstrap. These results are further compared with climate model simulations from the CESM large ensemble output. Seasonal analysis of the different ice types using NASA Team and Bootstrap shows that during ice advance, the ice advances as pack ice, with a seasonal peak in September (broader peak for Bootstrap), and as the pack ice begins to retreat, it first converts to a wide area of MIZ, that reaches its peak around November (NASA Team) or December (Bootstrap). CESM also shows a similar seasonal cycle, with a peak in the pack ice in August, and a December/January peak in the MIZ. Seasonal variability and trends are

  13. Phytoplankton Composition of Poyrazlar Lake (Sakarya)

    OpenAIRE

    Sevindik, Tuğba Ongun; Altundal, Ersin; KÜÇÜK, Fatma

    2015-01-01

    The aim of this study is to determine the phytoplankton composition of Poyrazlar Lake. The phytoplankton of the Poyrazlar Lake was investigated between April 2011 and March 20012. Samples were taken monthly from 3 sampling stations. A total of 120 taxa belonging to 7 divisions have been identified, including Chlorophyta (46 taxa), Ochrophyta (33 taxa), Euglenozoa (14 taxa), Charophyta (10 taxa), Cyanobacteria (9 taxa), Cryptophyta (4 taxa) and Dinophyta (4 taxa). Chlorophyta and Ochrophyta we...

  14. Emergent neutrality drives phytoplankton species coexistence

    Science.gov (United States)

    Segura, Angel M.; Calliari, Danilo; Kruk, Carla; Conde, Daniel; Bonilla, Sylvia; Fort, Hugo

    2011-01-01

    The mechanisms that drive species coexistence and community dynamics have long puzzled ecologists. Here, we explain species coexistence, size structure and diversity patterns in a phytoplankton community using a combination of four fundamental factors: organism traits, size-based constraints, hydrology and species competition. Using a ‘microscopic’ Lotka–Volterra competition (MLVC) model (i.e. with explicit recipes to compute its parameters), we provide a mechanistic explanation of species coexistence along a niche axis (i.e. organismic volume). We based our model on empirically measured quantities, minimal ecological assumptions and stochastic processes. In nature, we found aggregated patterns of species biovolume (i.e. clumps) along the volume axis and a peak in species richness. Both patterns were reproduced by the MLVC model. Observed clumps corresponded to niche zones (volumes) where species fitness was highest, or where fitness was equal among competing species. The latter implies the action of equalizing processes, which would suggest emergent neutrality as a plausible mechanism to explain community patterns. PMID:21177680

  15. Water masses, ocean fronts, and the structure of Antarctic seabird communities: Putting the eastern Bellingshausen Sea in perspective

    Science.gov (United States)

    Ribic, Christine A.; Ainley, David G.; Glenn Ford, R.; Fraser, William R.; Tynan, Cynthia T.; Woehler, Eric J.

    2011-07-01

    Waters off the western Antarctic Peninsula (i.e., the eastern Bellingshausen Sea) are unusually complex owing to the convergence of several major fronts. Determining the relative influence of fronts on occurrence patterns of top-trophic species in that area, therefore, has been challenging. In one of the few ocean-wide seabird data syntheses, in this case for the Southern Ocean, we analyzed ample, previously collected cruise data, Antarctic-wide, to determine seabird species assemblages and quantitative relationships to fronts as a way to provide context to the long-term Palmer LTER and the winter Southern Ocean GLOBEC studies in the eastern Bellingshausen Sea. Fronts investigated during both winter (April-September) and summer (October-March) were the southern boundary of the Antarctic Circumpolar Current (ACC), which separates the High Antarctic from the Low Antarctic water mass, and within which are embedded the marginal ice zone and Antarctic Shelf Break Front; and the Antarctic Polar Front, which separates the Low Antarctic and the Subantarctic water masses. We used clustering to determine species' groupings with water masses, and generalized additive models to relate species' densities, biomass and diversity to distance to respective fronts. Antarctic-wide, in both periods, highest seabird densities and lowest species diversity were found in the High Antarctic water mass. In the eastern Bellingshausen, seabird density in the High Antarctic water mass was lower (as low as half that of winter) than found in other Antarctic regions. During winter, Antarctic-wide, two significant species groups were evident: one dominated by Adélie penguins ( Pygoscelis adeliae) (High Antarctic water mass) and the other by petrels and prions (no differentiation among water masses); in eastern Bellingshausen waters during winter, the one significant species group was composed of species from both Antarctic-wide groups. In summer, Antarctic-wide, a High Antarctic group dominated

  16. Antarctic Ozone Hole, 2000

    Science.gov (United States)

    2002-01-01

    Each spring the ozone layer over Antarctica nearly disappears, forming a 'hole' over the entire continent. The hole is created by the interaction of some man-made chemicals-freon, for example-with Antarctica's unique weather patterns and extremely cold temperatures. Ozone in the stratosphere absorbs ultraviolet radiation from the sun, thereby protecting living things. Since the ozone hole was discovered many of the chemicals that destroy ozone have been banned, but they will remain in the atmosphere for decades. In 2000, the ozone hole grew quicker than usual and exceptionally large. By the first week in September the hole was the largest ever-11.4 million square miles. The top image shows the average total column ozone values over Antarctica for September 2000. (Total column ozone is the amount of ozone from the ground to the top of the atmosphere. A relatively typical measurement of 300 Dobson Units is equivalent to a layer of ozone 0.12 inches thick on the Earth's surface. Levels below 220 Dobson Units are considered to be significant ozone depletion.) The record-breaking hole is likely the result of lower than average ozone levels during the Antarctic fall and winter, and exceptionally cold temperatures. In October, however (bottom image), the hole shrank dramatically, much more quickly than usual. By the end of October, the hole was only one-third of it's previous size. In a typical year, the ozone hole does not collapse until the end of November. NASA scientists were surprised by this early shrinking and speculate it is related to the region's weather. Global ozone levels are measured by the Total Ozone Mapping Spectrometer (TOMS). For more information about ozone, read the Earth Observatory's ozone fact sheet, view global ozone data and see these ozone images. Images by Greg Shirah, NASA GSFC Scientific Visualization Studio.

  17. Variable climatic conditions dominate recent phytoplankton dynamics in Chesapeake Bay

    Science.gov (United States)

    Harding, Lawrence W., Jr.; Mallonee, Michael E.; Perry, Elgin S.; Miller, W. David; Adolf, Jason E.; Gallegos, Charles L.; Paerl, Hans W.

    2016-03-01

    Variable climatic conditions strongly influence phytoplankton dynamics in estuaries globally. Our study area is Chesapeake Bay, a highly productive ecosystem providing natural resources, transportation, and recreation for nearly 16 million people inhabiting a 165,000-km2 watershed. Since World War II, nutrient over-enrichment has led to multiple ecosystem impairments caused by increased phytoplankton biomass as chlorophyll-a (chl-a). Doubled nitrogen (N) loadings from 1945–1980 led to increased chl-a, reduced water clarity, and low dissolved oxygen (DO), while decreased N loadings from 1981–2012 suggest modest improvement. The recent 30+ years are characterized by high inter-annual variability of chl-a, coinciding with irregular dry and wet periods, complicating the detection of long-term trends. Here, we synthesize time-series data for historical and recent N loadings (TN, NO2 + NO3), chl-a, floral composition, and net primary productivity (NPP) to distinguish secular changes caused by nutrient over-enrichment from spatio-temporal variability imposed by climatic conditions. Wet years showed higher chl-a, higher diatom abundance, and increased NPP, while dry years showed lower chl-a, lower diatom abundance, and decreased NPP. Our findings support a conceptual model wherein variable climatic conditions dominate recent phytoplankton dynamics against a backdrop of nutrient over-enrichment, emphasizing the need to separate these effects to gauge progress toward improving water quality in estuaries.

  18. Short- and Long-Term Response of Phytoplankton to ENSO in Prydz Bay, Antarctica:Evidences from Field Measurements, Remote Sensing Data and Stratigraphic Biomarker Records

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jun; Hans-Ulrich Peter; ZHANG Haisheng; HAN Zhengbing; HU Chuanyu; YU Peisong; LU Bing; Thomas S.Bianchi

    2014-01-01

    The study provides one of the first lines of evidence showing linkages between Antarctic phytoplankton abundance and composition in response to ENSO, based on historical reconstruction of sediment biomarkers. In addition to sediment biomarkers, field measured and remote sensing data of phytoplankton abundance were also recorded from Prydz Bay, Eastern Antarctica. Com-munity structure of field measured phytoplankton showed significant El Niño/La Niña-related succession during 1990 to 2002. In general, the number of algae species decreased during El Niño and La Niña years compared to normal years. Austral summer monthly variation of remotely sensed chlorophyll-a (Chl-a), particulate organic carbon (POC), and sea surface temperature (SST) indicated that ENSO impacted the timing of phytoplankton blooms during 2007 to 2011. Phytoplankton blooms (indicated by Chl-a and POC) preceded the increases in SST during El Niño years, and lagged behind the SST increases during La Niña years. Stratigraphic record of marine sedimentary lipid (brassicasterol, dinosterol and alkenones) biomarkers inferred that the proportions of different algae (diatoms, dinoflagellates and haptophytes) changed significantly between El Niño and La Niña events. The relative proportion of diatoms increased, with that of dinoflagellates being decreased during El Niño years, while it was reversed during La Niña years.

  19. Interactions of anthropogenic stress factors on phytoplankton

    Directory of Open Access Journals (Sweden)

    Donat P. Häder

    2015-03-01

    Full Text Available Phytoplankton are the main primary producers in aquatic ecosystems. Their biomass production and CO2 sequestration equals that of all terrestrial plants taken together. Phytoplankton productivity is controlled by a number of environmental factors, many of which currently undergo substantial changes due to anthropogenic global climate change. Light availability is an absolute requirement for photosynthesis, but excessive visible and UV radiation impair productivity. Increasing temperatures enhance stratification, decrease the depth of the upper mixing layer exposing the cells to higher solar radiation, and reduce nutrient upward transport from deeper layers. At the same time, stratospheric ozone depletion exposes phytoplankton to higher solar UV-B radiation especially in polar and mid latitudes. Terrestrial runoff carrying sediments and dissolved organic matter into coastal waters leads to eutrophication while reducing UV penetration. All these environmental forcings are known to affect physiological and ecological processes of primary producers. Ocean acidification due to increased atmospheric CO2 concentrations changes the seawater chemistry; it reduces calcification in phytoplankton, macroalgae and many zoological taxa and enhances UV-induced damage. Ocean warming results in changing species composition and favors blooms of toxic prokaryotic and eukaryotic phytoplankton; it moderates UV-induced damage of the photosynthetic apparatus because of higher repair rates. Increasing pollution from crude oil spills, persistent organic pollutants, heavy metal as well as industrial and household wastewaters affect phytoplankton, which is augmented by solar UV radiation. In view of the fact that extensive analyses of the impacts of multiple stressors are scarce, here we review reported findings on the impacts of anthropogenic stressors on phytoplankton with an emphasis on their interactive effects and a prospect for future studies.

  20. Antarctic Porifera database from the Spanish benthic expeditions.

    Science.gov (United States)

    Rios, Pilar; Cristobo, Javier

    2014-01-01

    THE INFORMATION ABOUT THE SPONGES IN THIS DATASET IS DERIVED FROM THE SAMPLES COLLECTED DURING FIVE SPANISH ANTARCTIC EXPEDITIONS: Bentart 94, Bentart 95, Gebrap 96, Ciemar 99/00 and Bentart 2003. Samples were collected in the Antarctic Peninsula and Bellingshausen Sea at depths ranging from 4 to 2044 m using various sampling gears. The Antarctic Porifera database from the Spanish benthic expeditions is unique as it provides information for an under-explored region of the Southern Ocean (Bellingshausen Sea). It fills an information gap on Antarctic deep-sea sponges, for which there were previously very few data. This phylum is an important part of the Antarctic biota and plays a key role in the structure of the Antarctic marine benthic community due to its considerable diversity and predominance in different areas. It is often a dominant component of Southern Ocean benthic communities. The quality of the data was controlled very thoroughly with GPS systems onboard the R/V Hesperides and by checking the data against the World Porifera Database (which is part of the World Register of Marine Species, WoRMS). The data are therefore fit for completing checklists, inclusion in biodiversity pattern analysis and niche modelling. The authors can be contacted if any additional information is needed before carrying out detailed biodiversity or biogeographic studies. The dataset currently contains 767 occurrence data items that have been checked for systematic reliability. This database is not yet complete and the collection is growing. Specimens are stored in the author's collection at the Spanish Institute of Oceanography (IEO) in the city of Gijón (Spain). The data are available in GBIF. PMID:24843257

  1. Antarctic Porifera database from the Spanish benthic expeditions

    Directory of Open Access Journals (Sweden)

    Pilar Rios

    2014-04-01

    Full Text Available The information about the sponges in this dataset is derived from the samples collected during five Spanish Antarctic expeditions: Bentart 94, Bentart 95, Gebrap 96, Ciemar 99/00 and Bentart 2003. Samples were collected in the Antarctic Peninsula and Bellingshausen Sea at depths ranging from 4 to 2044 m using va­rious sampling gears.The Antarctic Porifera database from the Spanish benthic expeditions is unique as it provides in­formation for an under-explored region of the Southern Ocean (Bellingshausen Sea. It fills an information gap on Antarctic deep-sea sponges, for which there were previously very few data.This phylum is an important part of the Antarctic biota and plays a key role in the structure of the Antarctic marine benthic community due to its considerable diversity and predominance in different areas. It is often a dominant component of Southern Ocean benthic communities.The quality of the data was controlled very thoroughly with GPS systems onboard the R/V Hesperides and by checking the data against the World Porifera Database (which is part of the World Register of Marine Species, WoRMS. The data are therefore fit for completing checklists, inclusion in biodivers­ity pattern analysis and niche modelling. The authors can be contacted if any additional information is needed before carrying out detailed biodiversity or biogeographic studies.The dataset currently contains 767 occurrence data items that have been checked for systematic reliability. This database is not yet complete and the collection is growing. Specimens are stored in the author’s collection at the Spanish Institute of Oceanography (IEO in the city of Gijón (Spain. The data are available in GBIF.

  2. Principles of the Antarctic Treaty

    Science.gov (United States)

    Candidi, M.

    The operation of any base or expedition to Antarctica is regulated by the mutual agreement among nations in the “Antarctic Treaty”. This treaty deals with the major aspects of life in Antarctica and its main principles and provisions are described in what follows.

  3. Special Stamps:Antarctic Scenery

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In July 2002, the State Postal Bureau issued a set of three stamps, whose theme is Antarctic scenery.The first stamp depicts an iceberg. Antarctica is where 90 percent of the world’s ice exists. Each year countless icebergs float majestically through the sea, and are a magnificent scenic feature of Antarctica.

  4. Interhemispheric coupling and warm Antarctic interglacials

    Directory of Open Access Journals (Sweden)

    P. B. Holden

    2009-12-01

    Full Text Available Ice core evidence indicates that even though atmospheric CO2 concentrations did not exceed ~300 ppm at any point during the last 800 000 years, East Antarctica was at least ~3–4 °C warmer than pre-industrial (CO2 ~280 ppm in each of the last four interglacials. During the previous three interglacials, this anomalous warming was short lived (~3 000 years and apparently occurred before the completion of Northern Hemisphere deglaciation. Hereafter, we refer to these periods as "Warmer than Present Transients" (WPTs. We here present transient 800 kyr simulations using the intermediate complexity model GENIE-1 which suggest that WPTs could be explained as a consequence of the meltwater-forced slowdown of the Atlantic Meridional Overturning Circulation (AMOC during glacial terminations. It is well known that a slowed AMOC would increase southern Sea Surface Temperature (SST through the bipolar seesaw. Observational data supports this hypothesis, suggesting that the AMOC remained weak throughout the terminations preceding WPTs, strengthening rapidly at a time which coincides closely with peak Antarctic temperature. In order to investigate model and boundary condition uncertainty, we additionally present three ensembles of transient GENIE-1 simulations across Termination II (135 000 to 124 000 BP and three snapshot HadCM3 simulations at 130 000 Before Present (BP. These simulations together reproduce both the timing and magnitude of WPTs, and point to the potential importance of an albedo feedback associated with West Antarctic Ice Sheet (WAIS retreat.

  5. The role of deep convection on the dynamics of the North Atlantic phytoplankton community

    DEFF Research Database (Denmark)

    Lindemann, Christian

    convective regimes. To investigate this discrepancy between observations and model studies, a modeling approach commonly used in population models was applied to a spatial grid, where the advective flow was explicit represented. The result shows that indeed phytoplankton can persists in highly turbulent deep...

  6. Global phytoplankton decline over the past century.

    Science.gov (United States)

    Boyce, Daniel G; Lewis, Marlon R; Worm, Boris

    2010-07-29

    In the oceans, ubiquitous microscopic phototrophs (phytoplankton) account for approximately half the production of organic matter on Earth. Analyses of satellite-derived phytoplankton concentration (available since 1979) have suggested decadal-scale fluctuations linked to climate forcing, but the length of this record is insufficient to resolve longer-term trends. Here we combine available ocean transparency measurements and in situ chlorophyll observations to estimate the time dependence of phytoplankton biomass at local, regional and global scales since 1899. We observe declines in eight out of ten ocean regions, and estimate a global rate of decline of approximately 1% of the global median per year. Our analyses further reveal interannual to decadal phytoplankton fluctuations superimposed on long-term trends. These fluctuations are strongly correlated with basin-scale climate indices, whereas long-term declining trends are related to increasing sea surface temperatures. We conclude that global phytoplankton concentration has declined over the past century; this decline will need to be considered in future studies of marine ecosystems, geochemical cycling, ocean circulation and fisheries. PMID:20671703

  7. Phytoplankton Bloom in North Sea off Scotland

    Science.gov (United States)

    2008-01-01

    The northern and western highlands of Scotland were still winter-brown and even dusted with snow in places, but the waters of the North Sea were blooming with phytoplankton on May 8, 2008, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite passed over the region and captured this image. The tiny, plant-like organisms swirled in the waters off the country's east coast, coloring the shallow coastal waters shades of bright blue and green. Phytoplankton are tiny organisms--many are just a single cell--that use chlorophyll and other pigments to capture light for photosynthesis. Because these pigments absorb sunlight, they change the color of the light reflected from the sea surface back to the satellite. Scientists have used observations of 'ocean color' from satellites for more than 20 years to track worldwide patterns in phytoplankton blooms. Phytoplankton are important to the Earth system for a host of reasons, including their status as the base of the ocean food web. In the North Sea, they are the base of the food web that supports Scotland's commercial fisheries, including monkfish and herring. As photosynthesizers, they also play a crucial role in the carbon cycle, removing carbon dioxide from the atmosphere. Some oceanographers are concerned that rising ocean temperatures will slow phytoplankton growth rates, harming marine ecosystems and causing carbon dioxide to accumulate more rapidly in the atmosphere.

  8. SOME ENVIRONMENTAL FEATURES OF PHYTOPLANKTON

    Directory of Open Access Journals (Sweden)

    Taha A. Al-Tayyar

    2013-05-01

    Full Text Available Todefine the biological features of phytoplankton in Mosul  Dam  Lake, monthly samples were collectedalong a year from September 2003 to August 2004. Consisting thermalstratification and turn over periods from four locations in the main lake andanother location in the regulating lake. Total numbers of algae  reached 2300 cell/ml in the main lake and 1100cell/ml in the regulating lake.Bacillariophyta were dominant with a maximum number of 1400 cell/ml in autumn. Chlorophytawere dominant in autumn also with 550 cell/ml. Ten genus of Chlorophyta wereappeared in this water body: Cosmarium, Chlorella, Spirogyra, Scendesmus, Pediastrum, Tetraedron, Quadrigula, Ankiseradosm, Pandorina, and Straurastrum.Seven genus of Bacillariophyta were noticeable. Some genus of Cyanophyta was recorded as Aphanocapsa. In addition someEuglenophyta spp. were occurred in the main lake and the regulating lake also. On thebasis of these algae abundance, the lake is undergoing cultural Eutrophication.It has passed in mesotrophic state (the middle trophic state ofEutrophication. Some genera which were appeared are the indication ofeutrophic state.Totalplate count bacteria ranged from 400-1700 cell/ ml in the main lake and 200-950 cell/ml in the regulating lakewere also recorded. Coliform bacteria were founded with most probablenumber  reached 460 cell/100ml in themain lake and 150 cell/100ml in the regulating lake. Therefore, the lake wateris classified as moderate pure and considering a good source of raw water supplywith all treatment units and safe for swimming and recreational uses.

  9. Modeling phytoplankton blooms and carbon export production in the Southern Ocean : dominant controls by light and iron in the Atlantic sector in Austral spring 1992

    NARCIS (Netherlands)

    Lancelot, C.; Hannon, E.; Becquevort, S.; Veth, C.; Baar, H.J.W. de

    2000-01-01

    The high nutrient low chlorophyll (HNLC) conditions of the Southern Ocean were explored with an ecological model (SWAMCO) describing the cycling of C, N, P, Si and Fe through different, aggregated, chemical and biological compartments of the plankton ecosystem. The structure of the model was chosen

  10. Phytoplankton composition and biomass across the southern Indian Ocean

    DEFF Research Database (Denmark)

    Schlüter, Louise; Henriksen, Peter; Nielsen, Torkel Gissel;

    2011-01-01

    Phytoplankton composition and biomass was investigated across the southern Indian Ocean. Phytoplankton composition was determined from pigment analysis with subsequent calculations of group contributions to total chlorophyll a (Chl a) using CHEMTAX and, in addition, by examination in the microscope...

  11. Patterns and multi-scale drivers of phytoplankton species richness in temperate peri-urban lakes.

    Science.gov (United States)

    Catherine, Arnaud; Selma, Maloufi; Mouillot, David; Troussellier, Marc; Bernard, Cécile

    2016-07-15

    Local species richness (SR) is a key characteristic affecting ecosystem functioning. Yet, the mechanisms regulating phytoplankton diversity in freshwater ecosystems are not fully understood, especially in peri-urban environments where anthropogenic pressures strongly impact the quality of aquatic ecosystems. To address this issue, we sampled the phytoplankton communities of 50 lakes in the Paris area (France) characterized by a large gradient of physico-chemical and catchment-scale characteristics. We used large phytoplankton datasets to describe phytoplankton diversity patterns and applied a machine-learning algorithm to test the degree to which species richness patterns are potentially controlled by environmental factors. Selected environmental factors were studied at two scales: the lake-scale (e.g. nutrients concentrations, water temperature, lake depth) and the catchment-scale (e.g. catchment, landscape and climate variables). Then, we used a variance partitioning approach to evaluate the interaction between lake-scale and catchment-scale variables in explaining local species richness. Finally, we analysed the residuals of predictive models to identify potential vectors of improvement of phytoplankton species richness predictive models. Lake-scale and catchment-scale drivers provided similar predictive accuracy of local species richness (R(2)=0.458 and 0.424, respectively). Both models suggested that seasonal temperature variations and nutrient supply strongly modulate local species richness. Integrating lake- and catchment-scale predictors in a single predictive model did not provide increased predictive accuracy; therefore suggesting that the catchment-scale model probably explains observed species richness variations through the impact of catchment-scale variables on in-lake water quality characteristics. Models based on catchment characteristics, which include simple and easy to obtain variables, provide a meaningful way of predicting phytoplankton species

  12. Phytoplankton communities of polar regions--Diversity depending on environmental conditions and chemical anthropopressure.

    Science.gov (United States)

    Kosek, Klaudia; Polkowska, Żaneta; Żyszka, Beata; Lipok, Jacek

    2016-04-15

    The polar regions (Arctic and Antarctic) constitute up to 14% of the biosphere and offer some of the coldest and most arid Earth's environments. Nevertheless several oxygenic phototrophs including some higher plants, mosses, lichens, various algal groups and cyanobacteria, survive that harsh climate and create the base of the trophic relationships in fragile ecosystems of polar environments. Ecosystems in polar regions are characterized by low primary productivity and slow growth rates, therefore they are more vulnerable to disturbance, than those in temperate regions. From this reason, chemical contaminants influencing the growth of photoautotrophic producers might induce serious disorders in the integrity of polar ecosystems. However, for a long time these areas were believed to be free of chemical contamination, and relatively protected from widespread anthropogenic pressure, due their remoteness and extreme climate conditions. Nowadays, there is a growing amount of data that prove that xenobiotics are transported thousands of kilometers by the air and ocean currents and then they are deposed in colder regions and accumulate in many environments, including the habitats of marine and freshwater cyanobacteria. Cyanobacteria (blue green algae), as a natural part of phytoplankton assemblages, are globally distributed, but in high polar ecosystems they represent the dominant primary producers. These microorganisms are continuously exposed to various concentration levels of the compounds that are present in their habitats and act as nourishment or the factors influencing the growth and development of cyanobacteria in other way. The most common group of contaminants in Arctic and Antarctic are persistent organic pollutants (POPs), characterized by durability and resistance to degradation. It is important to determine their concentrations in all phytoplankton species cells and in their environment to get to know the possibility of contaminants to transfer to higher

  13. Primary production in a tropical large lake: The role of phytoplankton composition

    International Nuclear Information System (INIS)

    Phytoplankton biomass and primary production in tropical large lakes vary at different time scales, from seasons to centuries. We provide a dataset made of 7 consecutive years of phytoplankton biomass and production in Lake Kivu (Eastern Africa). From 2002 to 2008, bi-weekly samplings were performed in a pelagic site in order to quantify phytoplankton composition and biomass, using marker pigments determined by HPLC. Primary production rates were estimated by 96 in situ 14C incubations. A principal component analysis showed that the main environmental gradient was linked to a seasonal variation of the phytoplankton assemblage, with a clear separation between diatoms during the dry season and cyanobacteria during the rainy season. A rather wide range of the maximum specific photosynthetic rate (PBm) was found, ranging between 1.15 and 7.21 g carbon g−1 chlorophyll a h−1, and was best predicted by a regression model using phytoplankton composition as an explanatory variable. The irradiance at the onset of light saturation (Ik) ranged between 91 and 752 μE m−2 s−1 and was linearly correlated with the mean irradiance in the mixed layer. The inter-annual variability of phytoplankton biomass and production was high, ranging from 53 to 100 mg chlorophyll a m−2 (annual mean) and from 143 to 278 g carbon m−2 y−1, respectively. The degree of seasonal mixing determined annual production, demonstrating the sensitivity of tropical lakes to climate variability. A review of primary production of other African great lakes allows situating Lake Kivu productivity in the same range as that of lakes Tanganyika and Malawi, even if mean phytoplankton biomass was higher in Lake Kivu. - Highlights: • We provide a 7-year dataset of primary production in a tropical great lake. • Specific photosynthetic rate was determined by community composition. • Annual primary production varied between 143 and 278 mg C m−2 y−1. • Pelagic production was highly sensitive to

  14. Iron–Nutrient Interactions within Phytoplankton

    Science.gov (United States)

    Schoffman, Hanan; Lis, Hagar; Shaked, Yeala; Keren, Nir

    2016-01-01

    Iron limits photosynthetic activity in up to one third of the world’s oceans and in many fresh water environments. When studying the effects of Fe limitation on phytoplankton or their adaptation to low Fe environments, we must take into account the numerous cellular processes within which this micronutrient plays a central role. Due to its flexible redox chemistry, Fe is indispensable in enzymatic catalysis and electron transfer reactions and is therefore closely linked to the acquisition, assimilation and utilization of essential resources. Iron limitation will therefore influence a wide range of metabolic pathways within phytoplankton, most prominently photosynthesis. In this review, we map out four well-studied interactions between Fe and essential resources: nitrogen, manganese, copper and light. Data was compiled from both field and laboratory studies to shed light on larger scale questions such as the connection between metabolic pathways and ambient iron levels and the biogeographical distribution of phytoplankton species. PMID:27588022

  15. Iron-Nutrient Interactions within Phytoplankton.

    Science.gov (United States)

    Schoffman, Hanan; Lis, Hagar; Shaked, Yeala; Keren, Nir

    2016-01-01

    Iron limits photosynthetic activity in up to one third of the world's oceans and in many fresh water environments. When studying the effects of Fe limitation on phytoplankton or their adaptation to low Fe environments, we must take into account the numerous cellular processes within which this micronutrient plays a central role. Due to its flexible redox chemistry, Fe is indispensable in enzymatic catalysis and electron transfer reactions and is therefore closely linked to the acquisition, assimilation and utilization of essential resources. Iron limitation will therefore influence a wide range of metabolic pathways within phytoplankton, most prominently photosynthesis. In this review, we map out four well-studied interactions between Fe and essential resources: nitrogen, manganese, copper and light. Data was compiled from both field and laboratory studies to shed light on larger scale questions such as the connection between metabolic pathways and ambient iron levels and the biogeographical distribution of phytoplankton species. PMID:27588022

  16. The role of noise on the steady state distributions of phytoplankton populations

    Science.gov (United States)

    Valenti, D.; Denaro, G.; Conversano, F.; Brunet, C.; Bonanno, A.; Basilone, G.; Mazzola, S.; Spagnolo, B.

    2016-05-01

    The spatio-temporal behaviour of total chlorophyll concentration is investigated in the middle of the Tyrrhenian Sea by using a stochastic approach. The study is based on a reaction–diffusion–taxis model, which is used to analyse the dynamics of five phytoplankton groups, responsible for about 80% of the total chlorophyll a inside the euphotic zone of the water column. The analysis is performed by considering: (i) the intraspecific competition of the phytoplanktonic groups for limiting factors, i.e. light intensity and nutrient concentration, (ii) the seasonal changes of environmental variables, and (iii) the random fluctuations of the components of the velocity field and temperature. Specifically, we investigate the effects of external perturbations, both deterministic and random, on the dynamics of phytoplankton populations, by inserting a term of multiplicative noise into the differential equation of the nutrient dynamics. The theoretical results of the phytoplankton abundances obtained by the stochastic model are converted in chlorophyll a concentrations, and compared with the experimental findings. The statistical checks, based on the chi-square test, show that the vertical distributions of total chlorophyll concentration are in a good agreement with the experimental data. Finally, we observe that the high intensity of environmental noise strongly modifies the steady spatial distributions of two phytoplankton groups usually localized in deeper layers, causing algal blooms in surface water.

  17. Nitrogen and phosphorus intake by phytoplankton in the Xiamen Bay

    Institute of Scientific and Technical Information of China (English)

    林彩; 林辉; 贺青; 许焜灿; 吴省三; 张元标; 陈金民; 陈宝红; 林力斌; 卢美鸾; 陈维芬; 汤荣坤; 暨卫东

    2010-01-01

    This paper describes a time series experiment examining the nitrogen and phosphorus intake of natural phytoplankton communities by a microcosms approach.Seawater samples containing natural phytoplankton communities were collected from waters around Baozhu Islet in inner Xiamen Bay and around Qingyu Islet in the outer bay.The goal was to elucidate the relationship between phytoplankton population enhancement,the biological removal of nitrogen and phosphorus from the seawater,and the phytoplankton nitrogen an...

  18. Warming Oceans, Phytoplankton, and River Discharge: Implications for Cholera Outbreaks

    OpenAIRE

    Jutla, Antarpreet S; Akanda, Ali S.; Griffiths, Jeffrey K; Colwell, Rita; Islam, Shafiqul

    2011-01-01

    Phytoplankton abundance is inversely related to sea surface temperature (SST). However, a positive relationship is observed between SST and phytoplankton abundance in coastal waters of Bay of Bengal. This has led to an assertion that in a warming climate, rise in SST may increase phytoplankton blooms and, therefore, cholera outbreaks. Here, we explain why a positive SST-phytoplankton relationship exists in the Bay of Bengal and the implications of such a relationship on cholera dynamics. We f...

  19. The annual cycles of phytoplankton biomass

    Science.gov (United States)

    Winder, M.; Cloern, J.E.

    2010-01-01

    Terrestrial plants are powerful climate sentinels because their annual cycles of growth, reproduction and senescence are finely tuned to the annual climate cycle having a period of one year. Consistency in the seasonal phasing of terrestrial plant activity provides a relatively low-noise background from which phenological shifts can be detected and attributed to climate change. Here, we ask whether phytoplankton biomass also fluctuates over a consistent annual cycle in lake, estuarine-coastal and ocean ecosystems and whether there is a characteristic phenology of phytoplankton as a consistent phase and amplitude of variability. We compiled 125 time series of phytoplankton biomass (chloro-phyll a concentration) from temperate and subtropical zones and used wavelet analysis to extract their dominant periods of variability and the recurrence strength at those periods. Fewer than half (48%) of the series had a dominant 12-month period of variability, commonly expressed as the canonical spring-bloom pattern. About 20 per cent had a dominant six-month period of variability, commonly expressed as the spring and autumn or winter and summer blooms of temperate lakes and oceans. These annual patterns varied in recurrence strength across sites, and did not persist over the full series duration at some sites. About a third of the series had no component of variability at either the six-or 12-month period, reflecting a series of irregular pulses of biomass. These findings show that there is high variability of annual phytoplankton cycles across ecosystems, and that climate-driven annual cycles can be obscured by other drivers of population variability, including human disturbance, aperiodic weather events and strong trophic coupling between phytoplankton and their consumers. Regulation of phytoplankton biomass by multiple processes operating at multiple time scales adds complexity to the challenge of detecting climate-driven trends in aquatic ecosystems where the noise to

  20. CHAMP Magnetic Anomalies of the Antarctic Crust

    Science.gov (United States)

    Kim, Hyung Rae; Gaya-Pique, Luis R.; vonFrese, Ralph R. B.; Taylor, Patrick T.; Kim, Jeong Woo

    2003-01-01

    Regional magnetic signals of the crust are strongly masked by the core field and its secular variations components and hence difficult to isolate in the satellite measurements. In particular, the un-modeled effects of the strong auroral external fields and the complicated- behavior of the core field near the geomagnetic poles conspire to greatly reduce the crustal magnetic signal-to-noise ratio in the polar regions relative to the rest of the Earth. We can, however, use spectral correlation theory to filter the static lithospheric and core field components from the dynamic external field effects. To help isolate regional lithospheric from core field components, the correlations between CHAMP magnetic anomalies and the pseudo magnetic effects inferred from gravity-derived crustal thickness variations can also be exploited.. Employing these procedures, we processed the CHAMP magnetic observations for an improved magnetic anomaly map of the Antarctic crust. Relative to the much higher altitude Orsted and noisier Magsat observations, the CHAMP magnetic anomalies at 400 km altitude reveal new details on the effects of intracrustal magnetic features and crustal thickness variations of the Antarctic.

  1. Longitudinal surface structures (flowstripes on Antarctic glaciers

    Directory of Open Access Journals (Sweden)

    N. F. Glasser

    2011-11-01

    Full Text Available Longitudinal surface structures (''flowstripes'' are common on many glaciers but their origin and significance are poorly understood. In this paper we present observations of the development of these longitudinal structures from four different Antarctic glacier systems (the Lambert Glacier/Amery Ice Shelf area, outlet glaciers in the Ross Sea sector, ice-shelf tributary glaciers on the Antarctic Peninsula, and the onset zone of a tributary to the Recovery Glacier Ice Stream in the Filchner Ice Shelf area. Mapping from optical satellite images demonstrates that longitudinal surface structures develop in two main situations: (1 as relatively wide flow stripes within glacier flow units and (2 as relatively narrow flow stripes where there is convergent flow around nunataks or at glacier confluence zones. Our observations indicate that the confluence features are narrower, sharper, and more clearly defined features. They are characterised by linear troughs or depressions on the ice surface and are much more common than the former type. Longitudinal surface structures within glacier flow units have previously been explained as the surface expression of localised bed perturbations but a universal explanation for those forming at glacier confluences is lacking. Here we propose that these features are formed at zones of ice acceleration and extensional flow at glacier confluences. We provide a schematic model for the development of longitudinal surface structures based on extensional flow that can explain their ridge and trough morphology as well as their down-ice persistence.

  2. Antarctic glaciation caused ocean circulation changes at the Eocene-Oligocene transition.

    Science.gov (United States)

    Goldner, A; Herold, N; Huber, M

    2014-07-31

    Two main hypotheses compete to explain global cooling and the abrupt growth of the Antarctic ice sheet across the Eocene-Oligocene transition about 34 million years ago: thermal isolation of Antarctica due to southern ocean gateway opening, and declining atmospheric CO2 (refs 5, 6). Increases in ocean thermal stratification and circulation in proxies across the Eocene-Oligocene transition have been interpreted as a unique signature of gateway opening, but at present both mechanisms remain possible. Here, using a coupled ocean-atmosphere model, we show that the rise of Antarctic glaciation, rather than altered palaeogeography, is best able to explain the observed oceanographic changes. We find that growth of the Antarctic ice sheet caused enhanced northward transport of Antarctic intermediate water and invigorated the formation of Antarctic bottom water, fundamentally reorganizing ocean circulation. Conversely, gateway openings had much less impact on ocean thermal stratification and circulation. Our results support available evidence that CO2 drawdown--not gateway opening--caused Antarctic ice sheet growth, and further show that these feedbacks in turn altered ocean circulation. The precise timing and rate of glaciation, and thus its impacts on ocean circulation, reflect the balance between potentially positive feedbacks (increases in sea ice extent and enhanced primary productivity) and negative feedbacks (stronger southward heat transport and localized high-latitude warming). The Antarctic ice sheet had a complex, dynamic role in ocean circulation and heat fluxes during its initiation, and these processes are likely to operate in the future.

  3. Bifurcation and spatial pattern formation in spreading of disease with incubation period in a phytoplankton dynamics

    Directory of Open Access Journals (Sweden)

    Randhir Singh Baghel

    2012-02-01

    Full Text Available In this article, we propose a three dimensional mathematical model of phytoplankton dynamics with the help of reaction-diffusion equations that studies the bifurcation and pattern formation mechanism. We provide an analytical explanation for understanding phytoplankton dynamics with three population classes: susceptible, incubated, and infected. This model has a Holling type II response function for the population transformation from susceptible to incubated class in an aquatic ecosystem. Our main goal is to provide a qualitative analysis of Hopf bifurcation mechanisms, taking death rate of infected phytoplankton as bifurcation parameter, and to study further spatial patterns formation due to spatial diffusion. Here analytical findings are supported by the results of numerical experiments. It is observed that the coexistence of all classes of population depends on the rate of diffusion. Also we obtained the time evaluation pattern formation of the spatial system.

  4. Tropical pacing of Antarctic sea ice increase

    Science.gov (United States)

    Schneider, D. P.

    2015-12-01

    One reason why coupled climate model simulations generally do not reproduce the observed increase in Antarctic sea ice extent may be that their internally generated climate variability does not sync with the observed phases of phenomena like the Pacific Decadal Oscillation (PDO) and ENSO. For example, it is unlikely for a free-running coupled model simulation to capture the shift of the PDO from its positive to negative phase during 1998, and the subsequent ~15 year duration of the negative PDO phase. In previously presented work based on atmospheric models forced by observed tropical SSTs and stratospheric ozone, we demonstrated that tropical variability is key to explaining the wind trends over the Southern Ocean during the past ~35 years, particularly in the Ross, Amundsen and Bellingshausen Seas, the regions of the largest trends in sea ice extent and ice season duration. Here, we extend this idea to coupled model simulations with the Community Earth System Model (CESM) in which the evolution of SST anomalies in the central and eastern tropical Pacific is constrained to match the observations. This ensemble of 10 "tropical pacemaker" simulations shows a more realistic evolution of Antarctic sea ice anomalies than does its unconstrained counterpart, the CESM Large Ensemble (both sets of runs include stratospheric ozone depletion and other time-dependent radiative forcings). In particular, the pacemaker runs show that increased sea ice in the eastern Ross Sea is associated with a deeper Amundsen Sea Low (ASL) and stronger westerlies over the south Pacific. These circulation patterns in turn are linked with the negative phase of the PDO, characterized by negative SST anomalies in the central and eastern Pacific. The timing of tropical decadal variability with respect to ozone depletion further suggests a strong role for tropical variability in the recent acceleration of the Antarctic sea ice trend, as ozone depletion stabilized by late 1990s, prior to the most

  5. Multibranch Antarctic Seismic Data Library facilitates research

    Science.gov (United States)

    Cooper, Alan K.

    In 1991, investigators from 11 nations involved in Antarctic multichannel seismic (MCS) reflection research sought a way to keep the Antarctic Treaty's promise of open access to data, and in the process to encourage Earth-science research using seismic data. The Antarctic Seismic Data Library System for Cooperative Research (SDLS) was the solution, and is now a recommendation of the Antarctic Treaty Consultative Parties (ATCP). Today—at 12 branches spanning the world—researchers can access over 68,000 km of marine MCS data to use for cooperative research.More than 150,000 km of MCS data have been accumulated since 1976 by 13 countries on nearly 70 cruises. The majority of data now in the library cover the Ross Sea, Wilkes Land, and Prydz Bay sectors of the Antarctic margin, with smaller amounts from the Weddell Sea and the Antarctic Peninsula.

  6. The phytoplankton chip - development and assessment of a DNA microarray as a reliable tool for monitoring of phytoplankton

    OpenAIRE

    Gescher, Christine

    2007-01-01

    One microarray, the Phytoplankton Chip was developed . Phytoplankton field samples were taken at the island of Helgoland in the North Sea from 2004 to 2006 at regular intervals. For the phytoplankton community, only the > 20 mikrometer size fraction is identified on a daily basis. For picoplanktonic groups, light microscopy can not differentiate taxa or species. The phyto- and especially picoplanktonic dynamics were successfully analyzed with the Phytoplankton Chip in these three annual cycle...

  7. Antarctic Cenozoic climate history from sedimentary records: ANDRILL and beyond.

    Science.gov (United States)

    McKay, R M; Barrett, P J; Levy, R S; Naish, T R; Golledge, N R; Pyne, A

    2016-01-28

    Mounting evidence from models and geological data implies that the Antarctic Ice Sheet may behave in an unstable manner and retreat rapidly in response to a warming climate, which is a key factor motivating efforts to improve estimates of Antarctic ice volume contributions to future sea-level rise. Here, we review Antarctic cooling history since peak temperatures of the Middle Eocene Climatic Optimum (approx. 50 Ma) to provide a framework for future initiatives to recover sediment cores from subglacial lakes and sedimentary basins in Antarctica's continental interior. While the existing inventory of cores has yielded important insights into the biotic and climatic evolution of Antarctica, strata have numerous and often lengthy time breaks, providing a framework of 'snapshots' through time. Further cores, and more work on existing cores, are needed to reconcile Antarctic records with the more continuous 'far-field' records documenting the evolution of global ice volume and deep-sea temperature. To achieve this, we argue for an integrated portfolio of drilling and coring missions that encompasses existing methodologies using ship- and sea-ice-/ice-shelf-based drilling platforms as well as recently developed seafloor-based drilling and subglacial access systems. We conclude by reviewing key technological issues that will need to be overcome.

  8. Recent Rapid Regional Climate Warming on the Antarctic Peninsula

    Science.gov (United States)

    Vaughan, D. G.; Marshall, G. J.; Connolley, W. M.; Parkinson, C.; Mulvaney, R.; Hodgson, D. A.; King, J. C.; Pudsey, C. J.; Turner, J.

    2002-12-01

    The Intergovernmental Panel on Climate Change (IPCC) confirmed that global warming was 0.6 ñ 0.2 degrees C during the 20th Century and cited increases in greenhouse gases as a likely contributor. But this average conceals the complexity of observed climate change, which is seasonally biased, decadally variable and geographically patchy. In particular, over the last 50 years three high-latitude areas have undergone recent rapid regional (RRR) warming ? substantially more rapid than the global mean. We discuss the spatial and temporal significance of RRR warming in one area, the Antarctic Peninsula. New analyses of station records show no ubiquitous polar amplification of global warming but significant RRR warming on the Antarctic Peninsula. We investigate the likelihood that this could be amplification of a global warming, and use climate-proxy data to indicate that this RRR warming on the Antarctic Peninsula is unprecedented over the last two millennia and unlikely to be a natural mode of variability. We can show a strong connection between RRR warming and reduced sea-ice duration in an area on the west of the Antarctic Peninsula, but here we cannot yet distinguish cause and effect. Thus for the present we cannot determine which process causes the RRR warming, and until the mechanism initiating and sustaining it is understood, and is convincingly reproduced in climate models, we lack a sound basis for predicting climate change in this region over the coming century.

  9. Evaluating Wind Power Potential in the Spanish Antarctic Base (BAE)

    International Nuclear Information System (INIS)

    The objective of the work is to model wind field in the surroundings of the Spanish Antarctic Base (BAE in the following). The need of such a work comes from the necessity of an energy source able to supply the energy demand in the BAE during the Antarctic winter. When the BAE is in operation (in the Antarctic summer) the energy supply comes from a diesel engine. In the Antarctic winter the base is closed, but the demand of energy supply is growing up every year because of the increase in the number of technical and scientific machines that remain in the BAE taking different measurements. For this purpose the top of a closed hill called Pico Radio, not perturbed by close obstacles, has been chosen as the better site for the measurements. The measurement station is made up with a sonic anemometer and a small wind generator to supply the energy needed by the sensors head heating of the anemometer. This way, it will be also used as a proof for the suitability of a wind generator in the new chosen site, under those special climatic conditions.(Author) 3 refs

  10. Antarctic tourism and the maritime heritage

    OpenAIRE

    Basberg, Bjørn L.

    2008-01-01

    Maritime activity in the Antarctic region goes back to the 18th Century. It evolved from exploration and discoveries to commercial activities, especially sealing and whaling. Antarctic tourism is a more recent phenomenon, developing gradually from the 1960s. Today, more than 20.000 tourists visit the Antarctic annually – mostly on cruise ships. The paper reviews the historical development of these activities. The main focus is on how the maritime heritage has been dealt with an...

  11. Phosphate and iron limitation of phytoplankton biomass in Lake Tahoe

    Science.gov (United States)

    Chang, Cecily C.Y.; Kuwabara, J.S.; Pasilis, S.P.

    1992-01-01

    Bioassays were carried out to assess the response of inoculated, single-species diatom populations (Cyclotella meneghiniana and Aulocosiera italica) to additions of synthetic chelators and phosphate. A chemical speciation model along with the field data was also used to predict how trace metal speciation, and hence bioavailability, was affected by the chelator additions. Results suggest that phosphate was limiting to phytoplankton biomass. Other solutes, Fe in particular, may also exert controls on biomass. Nitrate limitation seems less likely, although Fe-limiting conditions may have led to an effective N limitation because algae require Fe to carry out nitrate reduction. -from Authors

  12. A global seasonal surface ocean climatology of phytoplankton types based on CHEMTAX analysis of HPLC pigments

    Science.gov (United States)

    Swan, Chantal M.; Vogt, Meike; Gruber, Nicolas; Laufkoetter, Charlotte

    2016-03-01

    Much advancement has been made in recent years in field data assimilation, remote sensing and ecosystem modeling, yet our global view of phytoplankton biogeography beyond chlorophyll biomass is still a cursory taxonomic picture with vast areas of the open ocean requiring field validations. High performance liquid chromatography (HPLC) pigment data combined with inverse methods offer an advantage over many other phytoplankton quantification measures by way of providing an immediate perspective of the whole phytoplankton community in a sample as a function of chlorophyll biomass. Historically, such chemotaxonomic analysis has been conducted mainly at local spatial and temporal scales in the ocean. Here, we apply a widely tested inverse approach, CHEMTAX, to a global climatology of pigment observations from HPLC. This study marks the first systematic and objective global application of CHEMTAX, yielding a seasonal climatology comprised of ~1500 1°×1° global grid points of the major phytoplankton pigment types in the ocean characterizing cyanobacteria, haptophytes, chlorophytes, cryptophytes, dinoflagellates, and diatoms, with results validated against prior regional studies where possible. Key findings from this new global view of specific phytoplankton abundances from pigments are a) the large global proportion of marine haptophytes (comprising 32±5% of total chlorophyll), whose biogeochemical functional roles are relatively unknown, and b) the contrasting spatial scales of complexity in global community structure that can be explained in part by regional oceanographic conditions. The results are publically accessible via

  13. Does chlorophyll a provide the best index of phytoplankton biomass for primary productivity studies?

    Science.gov (United States)

    Huot, Y.; Babin, M.; Bruyant, F.; Grob, C.; Twardowski, M. S.; Claustre, H.

    2007-03-01

    Probably because it is a readily available ocean color product, almost all models of primary productivity use chlorophyll as their index of phytoplankton biomass. As other variables become more readily available, both from remote sensing and in situ autonomous platforms, we should ask if other indices of biomass might be preferable. Herein, we compare the accuracy of different proxies of phytoplankton biomass for estimating the maximum photosynthetic rate (Pmax) and the initial slope of the production versus irradiance (P vs. E) curve (α). The proxies compared are: the total chlorophyll a concentration (Tchla, the sum of chlorophyll a and divinyl chlorophyll), the phytoplankton absorption coefficient, the phytoplankton photosynthetic absorption coefficient, the active fluorescence in situ, the particulate scattering coefficient at 650 nm (bp (650)), and the particulate backscattering coefficient at 650 nm (bbp (650)). All of the data (about 170 P vs. E curves) were collected in the South Pacific Ocean. We find that when only the phytoplanktonic biomass proxies are available, bp (650) and Tchla are respectively the best estimators of Pmax and alpha. When additional variables are available, such as the depth of sampling, the irradiance at depth, or the temperature, Tchla becomes the best estimator of both Pmax and α. From a remote sensing perspective, error propagation analysis shows that, given the current algorithms errors for estimating bbp(650), Tchla remains the best estimator of Pmax.

  14. Effects of lowered pH on marine phytoplankton growth rates

    DEFF Research Database (Denmark)

    Berge, Terje; Daugbjerg, Niels; Andersen, Betinna Balling;

    2010-01-01

    concentration of seawater. Ocean acidification may potentially both stimulate and reduce primary production by marine phytoplankton. Data are scarce on the response of marine phytoplankton growth rates to lowered pH/increased CO2. Using the acid addition method to lower the seawater pH and manipulate...... the carbonate system, we determined in detail the lower pH limit for growth rates of 2 model species of common marine phytoplankton. We also tested whether growth and production rates of 6 other common species of phytoplankton were affected by ocean acidification (lowered to pH 7.0). The lower pH limits...... statistically similar in the pH range of ~7.0 to 8.5. Our results and literature reports on growth at lowered pH indicate that marine phytoplankton in general are resistant to climate change in terms of ocean acidification, and do not increase or decrease their growth rates according to ecological relevant...

  15. Phytoplankton biovolume is independent from the slope of the size spectrum in the oligotrophic atlantic ocean

    KAUST Repository

    Moreno-Ostos, Enrique

    2015-08-06

    Modelling the size-abundance spectrum of phytoplankton has proven to be a very useful tool for the analysis of physical-biological coupling and the vertical flux of carbon in oceanic ecosystems at different scales. A frequent observation relates high phytoplankton biovolume in productive regions with flatter spectrum slope and the opposite in oligotrophic ecosystems. Rather than this, the relationship between high biovolume phytoplankton assemblages and flatter size-abundance spectra does not correspond with measurements of the phytoplankton community in the Atlantic Ocean open waters. As part of the Malaspina Circunnavegation Expedition, sixty seven sampling stations within the Atlantic Ocean covering six oceanographic provinces, at different seasons, produced a complete set of phytoplankton size-spectra whose slope and biovolume did not show any obvious interrelation. In these oligotrophic sites, small (procaryotes) and medium-size (nanoplankton) cells are responsible for the most part of biovolume, and their response to environmental conditions does not apply to changes in the size-abundance spectrum slope as expected in richer, large-cell dominated ecosystems.

  16. Diagnosis of Physical and Biological Controls on Phytoplankton Distribution in the Sargasso Sea

    Institute of Scientific and Technical Information of China (English)

    WANG Caixia; Paola Malanotte-Rizzoli

    2014-01-01

    The linkage between physical and biological processes is studied by applying a one-dimensional physical-biological coupled model to the Sargasso Sea. The physical model is the Princeton Ocean Model and the biological model is a five-component system including phytoplankton, zooplankton, nitrate, ammonium, and detritus. The coupling between the physical and biological model is accomplished through vertical mixing which is parameterized by the level 2.5 Mellor and Yamada turbulence closure scheme. The coupled model investigates the annual cycle of ecosystem production and the response to external forcing, such as heat flux, wind stress, and surface salinity, and the relative importance of physical processes in affecting the ecosystem. Sensitivity ex-periments are also carried out, which provide information on how the model bio-chemical parameters affect the biological system. The computed seasonal cycles compare reasonably well with the observations of the Bermuda Atlantic Time-series Study (BATS). The spring bloom of phytoplankton occurs in March and April, right after the weakening of the winter mixing and before the estab-lishment of the summer stratification. The bloom of zooplankton occurs about two weeks after the bloom of phytoplankton. The sen-sitivity experiments show that zooplankton is more sensitive to the variations of biochemical parameters than phytoplankton.

  17. Antarctic skuas recognize individual humans.

    Science.gov (United States)

    Lee, Won Young; Han, Yeong-Deok; Lee, Sang-Im; Jablonski, Piotr G; Jung, Jin-Woo; Kim, Jeong-Hoon

    2016-07-01

    Recent findings report that wild animals can recognize individual humans. To explain how the animals distinguish humans, two hypotheses are proposed. The high cognitive abilities hypothesis implies that pre-existing high intelligence enabled animals to acquire such abilities. The pre-exposure to stimuli hypothesis suggests that frequent encounters with humans promote the acquisition of discriminatory abilities in these species. Here, we examine individual human recognition abilities in a wild Antarctic species, the brown skua (Stercorarius antarcticus), which lives away from typical human settlements and was only recently exposed to humans due to activities at Antarctic stations. We found that, as nest visits were repeated, the skua parents responded at further distances and were more likely to attack the nest intruder. Also, we demonstrated that seven out of seven breeding pairs of skuas selectively responded to a human nest intruder with aggression and ignored a neutral human who had not previously approached the nest. The results indicate that Antarctic skuas, a species that typically inhabited in human-free areas, are able to recognize individual humans who disturbed their nests. Our findings generally support the high cognitive abilities hypothesis, but this ability can be acquired during a relatively short period in the life of an individual as a result of interactions between individual birds and humans.

  18. Remote sensing of phytoplankton using laser-induced fluorescence

    International Nuclear Information System (INIS)

    The results of remote laser sensing of brackish-water phytoplankton on board a research vessel are presented. Field data of laser-induced fluorescence of phytoplankton obtained during the several cruises in the mouth of tile Gulf of Finland are compared with the results of standard chlorophyll a analysis of water samples and phytoplankton species determination by microscopy. The approach of fluorescence excitation by tunable laser radiation is applied to study the spatial distribution of a natural phytoplankton community. The remote analysis of the pigment composition of a phytoplankton community using the method of selective pigment excitation is described. The possibility of elaborating methods of quantitative laser remote biomonitoring is discussed

  19. Novel Technique for Assessing Ammonium Utilization by Phytoplankton in the San Francisco Bay-Delta Estuary

    Science.gov (United States)

    Schmidt, C. M.; Kendall, C.; Young, M. B.; Kraus, T. E. C.; Silva, S. R.; Richter, M. T.

    2015-12-01

    High concentrations of NH4+ in the San Francisco Bay-Delta Estuary (SFE) have been shown to inhibit the growth of phytoplankton, which are an important food source to zooplankton at the base of the pelagic food web. Here we present results from a study which used a stable isotope mixing model to quantify the proportion of nitrogen assimilated as NH4+ by phytoplankton in situ in a portion of the Sacramento River where NH4+ concentration is elevated downstream of the Sacramento Regional Wastewater Treatment Plant (SRWTP). To determine the δ15N value of phytoplankton, a novel method was developed to isolate phytoplankton from bulk particulate organic matter using flow cytometry prior to isotopic analysis. Modifications were made to an elemental analyzer to allow measurement of the δ15N values of samples containing as little as 0.5 µg N with an analytical precision of 0.2‰ (determined from replicate analysis of standards). During fall and spring field campaigns, two parcels of Sacramento River water (one with wastewater effluent and one without) were tracked and sampled in a Lagrangian sampling scheme over ~80 hours of travel downstream of the SRWTP. Water samples were analyzed for nutrient and chlorophyll concentrations as well δ15N-NO3 and δ15N-NH4+. In addition, approximately ten million phytoplankton cells were sorted from each sample for analysis of δ15N-phytoplankton. In parcels of Sacramento River water without wastewater effluent, NH4+ concentrations remained low and trends in δ15N-phytoplankton followed trends in δ15N-NO3-. In contrast, in the parcels containing SRWTP effluent phytoplankton uptake of N as NH4+ gradually increased from 15% immediately downstream of the SRWTP to as high as 90% after 80 hours of downstream transit. Previous mesocosm incubation experiments have demonstrated depressed growth rates and a rapid switch from NO3- to NH4+ uptake downstream of the SRWTP, suggesting that the apparent gradual increase in the proportion of N

  20. Seasonal variations in phytoplankton growth and microzooplankton grazing in a temperate coastal embayment, Korea

    Science.gov (United States)

    Kim, Sunju; Park, Myung Gil; Moon, Changho; Shin, Kyoungsoon; Chang, Man

    2007-01-01

    Microzooplankton grazing on coastal phytoplankton was determined by the dilution method from May 2002 to April 2003 at a fixed site located in the Jinhae Bay, Korea. During the dilution experiments, our study site exhibited a wide range of chlorophyll a concentrations (0.29-127.42 μg l -1), and the species composition of the phytoplankton community changed dramatically over a year, shifting from the predominance of chain-forming diatoms, particularly Chaetoceros spp., Leptocylindrus danicus, Pseudonitzschia pungens, and Skeletonema costatum, between May and September 2002, to a massive bloom of the dinoflagellates, Alexandrium spp. in October 2002, to a dominance of cryptophytes ( Chroomonas sp.) between November 2002 and March 2003, and then again to a prevalence of diatoms toward the end of the experiment. Both nutrients enriched ( μ n) and in situ phytoplankton growth rates ( μ0) showed pronounced seasonal variations, ranging from 0.11 to 2.87 d -1 and from -0.63 to 2.08 d -1, respectively. With regard to both variables, the lowest values were obtained during the fall and winter seasons. The average ratio of μ0/ μ n was 0.96 (SE = 0.08), thereby indicating that phytoplankton growth in the study site was not nutrient-limited. Microzooplankton grazing rates showed the large fluctuations (0-3.86 d -1) over an annual cycle, with non-significant and/or negative grazing frequently (62% of 29 measurements) detected. Relatively high grazing rates did occur frequently at the times during which a large phytoplankton biomass and/or large-sized phytoplankton dominance were observed. Our results contribute to the growing body of evidence suggesting that microzooplankton are important phytoplankton consumers in communities dominated by large phytoplankton, and also bolster the notion that size-based models of food web relationships may be of limited predictive value. The observed large fluctuations in grazing rates over a year, coupled with frequent non-significant and

  1. Satellite SAR and 'in situ' observations of phytoplankton in eutrophic waters

    Science.gov (United States)

    Shomina, Olga; Ermakov, Stanislav; Sergievskaya, Irina; Kapustin, Ivan; da Silva, Jose

    2014-05-01

    from TerraSAR-X images along the ship tracks and were found to be consistent with X-band scatterometer data. The experiments proved that SAR backscatter as well as scatterometer signal decreases with phytoplankton concentration, and the areas of enhanced phytoplankton concentration appear in satellite images as "dark" areas. Theoretical modeling of radar backscatter as a function of phytoplankton concentration was performed using retrieved values of the effective water viscosity, the film elasticity and the surface tension coefficient. The theory was shown to be in good agreement with observations. The work has been supported by the Russian Foundation of Basic Research (Projects RFBR 12-05-31237, 11-05-00295, 13-05-97058, 13-05-97043), the Program RAS Radiophysics, and by the Russian Government (Grant No. 11.G34.31.0078).

  2. Phytoplankton and sediments in Gulf of Mexico

    Science.gov (United States)

    2002-01-01

    Affected both by terrestrial factors like agriculture, deforestation, and erosion, and by marine factors like salinity levels, ocean temperature and water pollution, coastal environments are the dynamic interface between land and sea. In this MODIS image from January 15, 2002, the Gulf of Mexico is awash in a mixture of phytoplankton and sediment. Tan-colored sediment is flowing out into the Gulf from the Mississippi River, whose floodplain cuts a pale, wide swath to the right of center in the image, and also from numerous smaller rivers along the Louisiana coast (center). Mixing with the sediment are the multi-colored blue and green swirls that reveal the presence of large populations of marine plants called phytoplankton. Phytoplankton populations bloom and then fade, and these cycles affect fish and mammals-including humans-higher up the food chain. Certain phytoplankton are toxic to both fish and humans, and coastal health departments must monitor ecosystems carefully, often restricting fishing or harvesting of shellfish until the blooms have subsided.

  3. Ecotoxicology of bromoacetic acid on estuarine phytoplankton.

    Science.gov (United States)

    Gordon, Ana R; Richardson, Tammi L; Pinckney, James L

    2015-11-01

    Bromoacetic acid is formed when effluent containing chlorine residuals react with humics in natural waters containing bromide. The objective of this research was to quantify the effects of bromoacetic acid on estuarine phytoplankton as a proxy for ecosystem productivity. Bioassays were used to measure the EC50 for growth in cultured species and natural marine communities. Growth inhibition was estimated by changes in chlorophyll a concentrations measured by fluorometry and HPLC. The EC50s for cultured Thalassiosira pseudonana were 194 mg L(-1), 240 mg L(-1) for Dunaliella tertiolecta and 209 mg L(-1) for Rhodomonas salina. Natural phytoplankton communities were more sensitive to contamination with an EC50 of 80 mg L(-1). Discriminant analysis suggested that bromoacetic acid additions cause an alteration of phytoplankton community structure with implications for higher trophic levels. A two-fold EC50 decrease in mixed natural phytoplankton populations affirms the importance of field confirmation for establishing water quality criteria.

  4. Immuno flow cytometry in marine phytoplankton research

    NARCIS (Netherlands)

    Peperzak, L; Vrieling, EG; Sandee, B; Rutten, T

    2000-01-01

    The developments in the combination of flow cytometry and immunology as a tool to identify, count and examine marine phytoplankton cells are reviewed. The concepts of immunology and now cytometry are described. A distinction is made between quantitative and qualitative immunofluorescence. Quantitati

  5. Earth's Most Important Producers: Meet the Phytoplankton!

    Science.gov (United States)

    Marrero, Meghan E.; Stevens, Nicole

    2011-01-01

    The ocean is home to some of Earth's most important producers. Single-celled organisms in the ocean are responsible for more than half of Earth's productivity, as well as most of its oxygen. Phytoplankton are single-celled, plantlike organisms. That is, they have chloroplasts and perform photosynthesis, but are not true plants, which are typically…

  6. Interhemispheric coupling, the West Antarctic Ice Sheet and warm Antarctic interglacials

    Directory of Open Access Journals (Sweden)

    P. B. Holden

    2010-07-01

    Full Text Available Ice core evidence indicates that even though atmospheric CO2 concentrations did not exceed ~300 ppm at any point during the last 800 000 years, East Antarctica was at least ~3–4 °C warmer than preindustrial (CO2~280 ppm in each of the last four interglacials. During the previous three interglacials, this anomalous warming was short lived (~3000 years and apparently occurred before the completion of Northern Hemisphere deglaciation. Hereafter, we refer to these periods as "Warmer than Present Transients" (WPTs. We present a series of experiments to investigate the impact of deglacial meltwater on the Atlantic Meridional Overturning Circulation (AMOC and Antarctic temperature. It is well known that a slowed AMOC would increase southern sea surface temperature (SST through the bipolar seesaw and observational data suggests that the AMOC remained weak throughout the terminations preceding WPTs, strengthening rapidly at a time which coincides closely with peak Antarctic temperature. We present two 800 kyr transient simulations using the Intermediate Complexity model GENIE-1 which demonstrate that meltwater forcing generates transient southern warming that is consistent with the timing of WPTs, but is not sufficient (in this single parameterisation to reproduce the magnitude of observed warmth. In order to investigate model and boundary condition uncertainty, we present three ensembles of transient GENIE-1 simulations across Termination II (135 000 to 124 000 BP and three snapshot HadCM3 simulations at 130 000 BP. Only with consideration of the possible feedback of West Antarctic Ice Sheet (WAIS retreat does it become possible to simulate the magnitude of observed warming.

  7. Numerical Simulation of Nutrient and Phytoplankton Dynamics in Guangxi Coastal Bays, China

    Institute of Scientific and Technical Information of China (English)

    QIAO Xudong; WANG Baodong; SUN Xia; LIANG Shengkang

    2014-01-01

    The increasing riverine pollutants have resulted in nutrient enrichment and deterioration of water quality in the coastal water of Guangxi Province, China. However, the quantitative relationship between nutrient loads and water quality responses, which is crucial for developing eutrophication control strategies, is not well studied. In this study, the riverine fluxes of nutrients were quan-tified and integrated with nutrient cycling and phytoplankton dynamics by using box models for Guangxi coastal bays. The model concepts and biogeochemical equations were the same; while most model parameters were specific for each bay. The parameters were calibrated with seasonal observations during 2006-2007, and validated with yearly averaged measurements in 2009. The gen-eral features of nutrient and phytoplankton dynamics were reproduced, and the models were proved feasible under a wide range of bay conditions. Dissolved inorganic nitrogen was depleted during the spring algal bloom in Zhenzhu Bay and Fangcheng Bay with relatively less nutrient inputs. Phosphorus concentration was high in spring, which decreased then due to continuous phytoplankton consumption. Chlorophyll-a concentration reached its annual maximum in summer, but was the minimum in winter. Eutrophication was characterized by both an increase in nutrient concentrations and phytoplankton biomass in Lianzhou Bay. Either about 80%re-duction of nitrogen or 70%reduction of phosphorus was required to control the algal bloom in Lianzhou Bay. Defects of the models were discussed and suggestions to the environmental protection of Guangxi coastal bays were proposed.

  8. Projected changes of Antarctic krill habitat by the end of the 21st century

    Science.gov (United States)

    Piñones, Andrea; Fedorov, Alexey V.

    2016-08-01

    Climate change is rapidly shaping the living environment of the most abundant keystone species of the Antarctic marine food web, Antarctic krill. Projected future changes for the krill habitat include a sustained increase in ocean temperature and changes in sea ice and chlorophyll a. Here we investigate how these factors affect the early life history of krill and identify the regions around Antarctica where the impact will be greatest. Our tool is a temperature-dependent krill growth model forced by data from comprehensive greenhouse warming simulations. We find that by the year 2100 localized regions along the western Weddell Sea, isolated areas of the Indian Antarctic , and the Amundsen/Bellingshausen Sea will support successful spawning habitats for krill. The failure of potentially successful spawning will have a strong impact on the already declining adult populations with consequences for the Antarctic marine food web, having both ecological and commercial ramifications.

  9. Spectral absorption coefficient of phytoplankton and its relation to chlorophyll a and remote sensing reflectance in coastal waters of southern China

    Institute of Scientific and Technical Information of China (English)

    CAO Wenxi; YANG Yuezhong; LIU Sheng; XU Xiaoqiang; YANG Dingtian; ZHANG Jianlin

    2005-01-01

    The spectral absorption coefficient of phytoplankton in coastal waters of southern China is investigated. Large variations in the absorption coefficient of phytoplankton are found. The absorption coefficient of phytoplankton at 443 nm ranged from 0. 006 m- 1 to 0. 484 m - 1, with an average value of 0. 067 m - 1. The chlorophyll-specific absorption coefficient of phytoplankton is also a bio-optical varito pigment composition of phytoplankton and package effect. The chlorophyll-specific absorption coefficient of phytoplankton decreases with the increasing of chlorophyll a concentration. This relationship can be described by a power law function, with the parameters and the coefficient of determination r2 as functions of wavelength, but the parameters describing the relationships in present study differed from that in Case 1 waters, thus the regional adjustment of model parameters was of particular significance for improving the accuracy of bio-optical algorithms for estimation of Chl-a concentration and primary production from remotely sensed data. Regression analysis of reflectance (R rs) ratio and absorption coefficient of phytoplankton (a ph) indicates a close correlation between them, which means that it is possible to retrieve absorption coefficient of phytoplankton using ocean color remote sensing data in optically complex coastal waters.

  10. JCADM, new directions in Antarctic data management

    Science.gov (United States)

    Campbell, H.; de Bruin, T. F.

    2008-12-01

    The Joint Committee on Antarctic Data Management (JCADM) was established by the Scientific Committee on Antarctic Research (SCAR) and the Council of Managers of National Antarctic Programs (COMNAP), to assist in the fulfilment of the data management obligations imposed by the Antarctic Treaty (section III.1.c): "Scientific observations and results from Antarctica shall be exchanged and made freely available." JCADM comprises representatives of the National Antarctic Data Centres or national points of contact. Currently 31 nations around the world are represented in JCADM. So far, JCADM has been focussing on the coordination of the Antarctic Master Directory (AMD), the internationally accessible, web-based, searchable record of Antarctic and Southern Ocean data set descriptions. The AMD is directly integrated into the international Global Change Master Directory (GCMD) to help further merge Antarctic science into global science. The AMD is a resource for scientists to advertise the data they have collected and to search for data they may need. Currently, JCADM is in a transition phase, moving forward to provide data access. Existing systems and web services technology will be used as much as possible, to increase efficiency and prevent 're-inventing the wheel' This poster will give an overview of this process, the current status and the expected results.

  11. Impact of climate change on Antarctic krill

    NARCIS (Netherlands)

    Florentino De Souza Silva, A.P.; Atkinson, A.; Kawaguchi, S.; Bravo Rebolledo, E.; Franeker, van J.A.

    2012-01-01

    Antarctic krill Euphausia superba (hereafter ‘krill’) occur in regions undergoing rapid environmental change, particularly loss of winter sea ice. During recent years, harvesting of krill has increased, possibly enhancing stress on krill and Antarctic ecosystems. Here we review the overall impact of

  12. Ambiguous climate impacts on the competition between submerged macrophytes and phytoplankton in shallow lakes

    NARCIS (Netherlands)

    Kosten, S.; Jeppesen, E.; Huszar, V.M.; Mazzeo, N.; Nes, van E.H.; Peeters, E.T.H.M.; Scheffer, M.

    2011-01-01

    1. Shallow lakes may switch from a state dominated by submerged macrophytes to a phytoplankton-dominated state when a critical nutrient concentration is exceeded. We explore how climate change may affect this critical nutrient concentration by linking a graphical model to data from 83 lakes along a

  13. Critical depth and critical turbulence : Two different mechanisms for the development of phytoplankton blooms

    NARCIS (Netherlands)

    Huisman, J.; van Oostveen, P.; Weissing, F.J.

    1999-01-01

    A turbulent diffusion model shows that there are two different mechanisms for the development of phytoplankton blooms. One of these mechanisms works in well-mixed environments and corresponds to the classical critical depth theory. The other mechanism is based on the rate of turbulent mixing. If tur

  14. Critical depth and critical turbulence: two different mechanisms for the development of phytoplankton blooms

    NARCIS (Netherlands)

    Huisman, J.; Van Oostveen, P.; Weissing, F.J.

    1999-01-01

    A turbulent diffusion model shows that there are two different mechanisms for the development of phytoplankton blooms. One of these mechanisms works in well-mixed environments and corresponds to the classical critical depth theory. The other mechanism is based on the rate of turbulent mixing. If tur

  15. Late Cenozoic Climate History of the Ross Embayment from the AND-1B Drill Hole: Culmination of Three Decades of Antarctic Margin Drilling

    Science.gov (United States)

    Naish, T.R.; Powell, R.D.; Barrett, P.J.; Levy, R.H.; Henrys, S.; Wilson, G.S.; Krissek, L.A.; Niessen, F.; Pompilio, M.; Ross, J.; Scherer, R.; Talarico, F.; Pyne, A.; ,

    2007-01-01

    Because of the paucity of exposed rock, the direct physical record of Antarctic Cenozoic glacial history has become known only recently and then largely from offshore shelf basins through seismic surveys and drilling. The number of holes on the continental shelf has been small and largely confined to three areas (McMurdo Sound, Prydz Bay, and Antarctic Peninsula), but even in McMurdo Sound, where Oligocene and early Miocene strata are well cored, the late Cenozoic is poorly known and dated. The latest Antarctic geological drilling program, ANDRILL, successfully cored a 1285-m-long record of climate history spanning the last 13 m.y. from subsea-floor sediment beneath the McMurdo Ice Shelf (MIS), using drilling systems specially developed for operating through ice shelves. The cores provide the most complete Antarctic record to date of ice-sheet and climate fluctuations for this period of Earth’s history. The >60 cycles of advance and retreat of the grounded ice margin preserved in the AND-1B record the evolution of the Antarctic ice sheet since a profound global cooling step in deep-sea oxygen isotope records ~14 m.y.a. A feature of particular interest is a ~90-m-thick interval of diatomite deposited during the warm Pliocene and representing an extended period (~200,000 years) of locally open water, high phytoplankton productivity, and retreat of the glaciers on land.

  16. Windblown Pliocene diatoms and East Antarctic Ice Sheet retreat

    Science.gov (United States)

    Scherer, Reed P.; DeConto, Robert M.; Pollard, David; Alley, Richard B.

    2016-01-01

    Marine diatoms in tillites along the Transantarctic Mountains (TAMs) have been used to suggest a diminished East Antarctic Ice Sheet (EAIS) during Pliocene warm periods. Updated ice-sheet modelling shows significant Pliocene EAIS retreat, creating marine embayments into the Wilkes and Aurora basins that were conducive to high diatom productivity and rapid accumulation of diatomaceous sediments. Here we show that subsequent isostatic uplift exposed accumulated unconsolidated marine deposits to wind erosion. We report new atmospheric modelling utilizing Pliocene climate and derived Antarctic landscapes indicating that prevailing mid-altitude winds transported diatoms towards the TAMs, dominantly from extensive emerged coastal deposits of the Aurora Basin. This result unifies leading ideas from competing sides of a contentious debate about the origin of the diatoms in the TAMs and their link to EAIS history, supporting the view that parts of the EAIS are vulnerable to relatively modest warming, with possible implications for future sea-level rise. PMID:27649516

  17. Antarctic springtime ozone depletion computed from temperature observations

    Science.gov (United States)

    Rosenfield, Joan E.; Schoeberl, Mark R.; Newman, Paul A.

    1988-01-01

    An observationally based, mechanistic dynamical model is used to simulate the decline of total ozone during September and October for the years 1979 through 1986. Vertical velocities derived from observed stratospheric temperature changes and computed radiative heating rates are used to advect an ozone mixing ratio profile during the Antarctic spring period. An early August 1982 Syowa balloonsonde ozone profile is used to initialize the computations. The model reasonably simulates the September and October changes in total ozone, considering the uncertainties in the observed data and the radiative heating. The simulated decline is found to be very sensitive to the choice of initial ozone profile and to small changes in the radiative heating. The results of this study suggest that the dynamical hypothesis of the Antarctic ozone depletion is both quantitatively credible and consistent with the observed temperature changes.

  18. Testing oils in antarctic soils

    International Nuclear Information System (INIS)

    The resident seals, whales and penguins in Antarctica's Ross Sea region have only environmentally friendly ways of getting around. In contrast, wherever humans go in the Antarctic and whatever they do, be it research, tourism or fishing, they need fuel for their planes, icebreaker ships, land vehicles and generators. Because of this, petroleum hydrocarbons are the most likely source of pollution in the Antarctic. Accidental oil spills often occur near scientific stations, where storage and refuelling of aircraft and vehicles can result in spills. Spills also occur as a consequence of drilling activities. Dr Jackie Aislabie, a microbiologist from the New Zealand government's research company Landcare Research, is leading a program aimed at understanding how oil spills impact on Antarctic soils. The properties of pristine soils were compared with oil-contaminated soil at three locations: Scott Base, Marble Point and in the Wright Valley at Bull Pass. Soils in the Scott Base area are impacted by the establishment and continuous habitation of the base over 40 years, and a hydrocarbon-contaminated site was sampled near a former storage area for drums of mixed oils. Soil sampled from Marble Point was taken from near the old Marble Point camp, which was inhabited from 1957 to about 1963. Oil stains were visible on the soil surface, and are assumed to have been there for more than 30 years. The samples selected for analysis from the Wright Valley came from a spill site near Bull Pass that occurred during seismic bore-hole drilling activities in 1985. The contamination levels ranged from below detection to just over 29,000 μg/g of soil. Descriptions and analyse results are included into a Geographic Information System and associated soils database

  19. Subtle effects of the water soluble fraction of oil spills on natural phytoplankton assemblages enclosed in mesocosms

    Science.gov (United States)

    González, J.; Fernández, E.; Figueiras, F. G.; Varela, M.

    2013-06-01

    Four mesocosm experiments were conducted to evaluate the effect of episodic oil spills on coastal marine phytoplankton assemblages. The experimental design was selected to simulate the Prestige oil spill, which occurred in Galician coastal waters (NW Iberia) in November 2002. The empirical results indicate that no significant direct effects of the water soluble fraction of oil (20-60 μg l-1 of chrysene equivalents) on phytoplankton biomass and production were observed immediately after oil additions. Despite this, subtle negative effects on primary production were detected using a modelling approach, being the impact lower on phytoplankton communities dominated by diatoms. Consistent with the reduced direct effect of oil additions on phytoplankton biomass and photosynthesis-related variables, no indirect trophic cascading effects, previously reported in microcosm experiments, were detected. This shows that the effect of punctual inputs of the water accommodated fraction of oil on natural phytoplankton communities was very subtle, undetectable on some occasions, and of much lower magnitude than the effects recorded in microcosm experiments. This suggests that the initial composition of the phytoplankton community determines the degree of response and that the experimental approach adopted could explain the different, and sometimes contradictory, reported responses of the planktonic community to the input of oil into the marine environment.

  20. Optical determination of phytoplankton floristic composition

    Science.gov (United States)

    Smith, P. S. D.; Bowers, D. G.; Mitchelson-Jacob, E. G.

    1997-02-01

    Radiance and irradiance measurements are collected using a seven channel profiling radiometer and a four channel moored irradiance sensor which both use Sea-viewing Wide Field-of- View Sensor (SeaWiFS) wavebands. The instruments were deployed as part of the Land-Ocean Interaction Study, shelf edge study on the Malin Shelf, off the west coast of Scotland, during spring and simmer 1995 and 1996. Changes in in-situ reflectance ratios, calculated from the blue, cyan and green wavebands of the moored color sensors, suggest a diatom-dominated spring bloom, followed by an early summer coccolithophore bloom, with a flagellate-dominated phytoplankton population during the summer. Similar changes are also seen in attenuance ratios and specific attenuation coefficients calculated from the profiling radiometer data. The use of these optical properties to determine phytoplankton floristic composition is discussed.

  1. Studies on phytoplankton-bacterial interactions

    Digital Repository Service at National Institute of Oceanography (India)

    DeCosta, P.M.

    , Smith AG (2005) Algae acquire vitamin B 12 through a symbiotic relationship with bacteria. Nature 438: 90-93. Cullen JJ, Lesser MP (1991) Inhibition of photosynthesis by ultraviolet radiation as a function of dose and dosage rate: results for a.... TT Maps and Publications Limited, Madras. Desikachary TV, Prema P (1987) Diatoms from the Bay of Bengal. In: Desikachary TV (ed.) Atlas of Diatoms. Fascicle III. TT Maps and Publications Limited, Madras. Droop MR (2007) Vitamins, phytoplankton...

  2. Near-Surface Phytoplankton Pigment from the Coastal Zone Color Scanner in the Subantarctic Region Southeast of New Zealand

    Science.gov (United States)

    Banse, Karl; English, David C.

    1997-01-01

    Primarily based on satellite images, the phytoplankton concentration southeast (down- stream) of New Zealand in the High Nitrate - Low Chlorophyll (HNLC) Subantarctic water between the Subtropical Convergence (STC) and the Polar Front (PF) is believed to be higher than in the remainder of the Pacific Sector. Iron enrichment is assumed to be the reason, To study the question, near-surface phytoplankton pigment estimates from the Coastal Zone Color Scanner for up to 7 yr were reprocessed with particular attention to interference by clouds. Monthly mean images were created for the U,S. JGOFS Box along 170 deg W and means for individual dates calculated for 7 large areas between 170 deg E and 160 deg W, 45 deg and 58 deg S, well offshore of New Zealand and principally between and away from the STC and PF. The areal means are about as low as in other HNLC regions (most values between 0.1 and 0.4 or 0.5 mg/ sq m, with very few winter images; median of seasonal means, 0.26 mg/sq m) except at times near the STC, The higher means tend to occur in late summer and autumn, However, contrary to expectations, neither the PF nor the environs of the Subantarctic Front are distinguished by a zone of increased pigment. Also, of 24 spring-summer images of oceanic islands in mostly pigment-poor water, 17 yielded no recognizable elevated pigment; islands were 5 times surrounded by approximately doubled concentrations (ca 100 km in diameter), and 2 cases may have been associated with an extensive bloom. Inspection of offshore images showed concentrations of 1 greater than or equal to(up to 5) mg/sq m in rare patches of 65 to 200 km size on approximately one-tenth of the dates; such patches were not seen in Sub-antarctic waters of the eastern Pacific Sector. A case is made for Australian airborne iron supply being the cause that, presumably, would enhance large-celled phytoplankton. Since, however, the putative iron supply from the seabed around the oceanic islands or the near

  3. Spatio-temporal variability of phytoplankton dimensional classes in the Mediterranean Sea from satellite data

    Science.gov (United States)

    Sammartino, Michela; Di Cicco, Annalisa; Marullo, Salvatore; Santoleri, Rosalia

    2016-04-01

    Phytoplankton contributes to fix half of the carbon dioxide released on Earth, becoming a key component not only in the carbon cycle, but also in several biogeochemical cycles. It is involved in the control of greenhouse gases and, consequently, in the effect of climate change on marine system. Therefore, phytoplankton is often considered one of the most common bio-indicator for any environmental changes, which, in turn, can affect the algal community composition and structure. The alteration of the biological, physical and chemical conditions in the ocean can be reflected in the algal assemblage structure, in terms of variation of dominant size class and taxonomic composition. In this work, the seasonal and year-to-year variability of the phytoplankton size class (PSC) spatial distribution has been examined in the Mediterranean Sea using ten year of satellite observations. The estimation of PSCs from space is based on relationship between chlorophyll a (Chl a) and diagnostic pigments that should be verified at regional scales. Our analysis shows that the Mediterranean pigments ratios differs from the global ones; therefore, we regionalized the mathematical relation existing between the Chl a and the diagnostic pigments, used in the in situ PSC identification. This regionally tuned relation allowed to improve the estimation of PSCs from space by reducing the observed bias between modelled and measured PSCs. The analysis of PSC satellite time series allowed, for the first time, to have a quantitative description of the seasonal and inter-annual variability of the spatial distribution of the algal community in the Mediterranean Sea. The results demonstrated that the pico-phytoplankton contributes with high values to the total Chl a, especially in summer and in ultra-oligotrophic environments, such as the Levantine basin. Micro-phytoplankton contribution results high during spring bloom period in offshore areas, characterized by a strong water mixing; while, in

  4. Synoptic relationships quantified between surface Chlorophyll-a and diagnostic pigments specific to phytoplankton functional types

    Science.gov (United States)

    Hirata, T.; Hardman-Mountford, N. J.; Brewin, R. J. W.; Aiken, J.; Barlow, R.; Suzuki, K.; Isada, T.; Howell, E.; Hashioka, T.; Noguchi-Aita, M.; Yamanaka, Y.

    2010-09-01

    Error-quantified, synoptic-scale relationships between chlorophyll-a (Chla) and phytoplankton pigment groups at the sea surface are presented. A total of nine pigment groups were considered to represent nine phytoplankton functional types (PFTs) including microplankton, nanoplankton, picoplankton, diatoms, dinoflagellates, green algae, picoeukaryotes, prokaryotes and Prochlorococcus sp. The observed relationships between Chla and pigment groups were well-defined at the global scale to show that Chla can be used as an index of not only phytoplankton abundance but also community structure; large (micro) phytoplankton monotonically increase as Chla increases, whereas the small (pico) phytoplankton community generally decreases. Within these relationships, we also found non-monotonic variations with Chla for certain pico-plankton (pico-eukaryotes, Prokaryotes and Prochlorococcus sp.) and for Green Algae and nano-sized phytoplankton. The relationships were quantified with a least-square fitting approach in order to estimate the PFTs from Chla alone. The estimated uncertainty of the relationships quantified depends on both phytoplankton types and Chla concentration. Maximum uncertainty over all groups (34.7% Chla) was found from diatom at approximately Chla = 1.07 mg m-3. However, the mean uncertainty of the relationships over all groups was 5.8 [% Chla] over the entire Chla range observed (0.02 < Chla < 6.84 mg m-3). The relationships were applied to SeaWiFS satellite Chla data from 1998 to 2009 to show the global climatological fields of the surface distribution of PFTs. Results show that microplankton are present in the mid and high latitudes, constituting ~9.0 [% Chla] of the phytoplankton community at the global surface, in which diatoms explain ~6.0 [% Chla]. Nanoplankton are ubiquious throught much of the global surface oceans except subtropical gyres, acting as a background population, constituting ~44.2 [% Chla]. Picoplankton are mostly limited in subtropical

  5. Synoptic relationships between surface Chlorophyll-a and diagnostic pigments specific to phytoplankton functional types

    Directory of Open Access Journals (Sweden)

    M. Noguchi-Aita

    2011-02-01

    Full Text Available Error-quantified, synoptic-scale relationships between chlorophyll-a (Chl-a and phytoplankton pigment groups at the sea surface are presented. A total of ten pigment groups were considered to represent three Phytoplankton Size Classes (PSCs, micro-, nano- and picoplankton and seven Phytoplankton Functional Types (PFTs, i.e. diatoms, dinoflagellates, green algae, prymnesiophytes (haptophytes, pico-eukaryotes, prokaryotes and Prochlorococcus sp.. The observed relationships between Chl-a and PSCs/PFTs were well-defined at the global scale to show that a community shift of phytoplankton at the basin and global scales is reflected by a change in Chl-a of the total community. Thus, Chl-a of the total community can be used as an index of not only phytoplankton biomass but also of their community structure. Within these relationships, we also found non-monotonic variations with Chl-a for certain pico-sized phytoplankton (pico-eukaryotes, Prokaryotes and Prochlorococcus sp. and nano-sized phytoplankton (Green algae, prymnesiophytes. The relationships were quantified with a least-square fitting approach in order to enable an estimation of the PFTs from Chl-a where PFTs are expressed as a percentage of the total Chl-a. The estimated uncertainty of the relationships depends on both PFT and Chl-a concentration. Maximum uncertainty of 31.8% was found for diatoms at Chl-a = 0.49 mg m−3. However, the mean uncertainty of the relationships over all PFTs was 5.9% over the entire Chl-a range observed in situ (0.02 < Chl-a < 4.26 mg m−3. The relationships were applied to SeaWiFS satellite Chl-a data from 1998 to 2009 to show the global climatological fields of the surface distribution of PFTs. Results show that microplankton are present in the mid and high latitudes, constituting only ~10.9% of the entire phytoplankton community in the mean field for 1998–2009, in which diatoms explain ~7.5%. Nanoplankton are ubiquitous throughout the global surface oceans

  6. Spontaneous Assembly of Exopolymers from Phytoplankton

    Directory of Open Access Journals (Sweden)

    Yong-Xue Ding

    2009-01-01

    Full Text Available Phytoplankton exopolymeric substances (EPS contribute significantly to the dissolved organic car bon (DOC pool in the ocean, playing crucial roles in the surface ocean car bon cycle. Recent studies have demonstrated that ~10% of marine DOC can self-assemble as microgels through electro static Ca bonds providing hotspots of enriched microbial substrate. How ever, the question whether EPS can self-assemble and the formation mechanisms for EPS microgels have not been examined. Here were port that EPS from three representative phytoplankton species, Synechococcus, Emiliania huxleyi, and Skeletonema costatum can spontaneously self assemble in artificial sea water (ASW, forming microscopic gels of ~ 3 - 4 _ in diameter. Different from the marine DOC polymers assembly, these EPS samples can self-assemble in Ca2+-free ASW. Further experiments from fluorescence enhancement and chemical composition analysis confirmed the existence of fair amounts of hydrophobic domains in these EPS samples. These results suggest that hydrophobic interactions play a key role in the assembly of EPS from these three species of marine phytoplankton.

  7. Annual cycle of Antarctic baseline aerosol: controlled by photooxidation-limited aerosol formation

    Directory of Open Access Journals (Sweden)

    M. Fiebig

    2013-09-01

    Full Text Available This article investigates the annual cycle observed in the Antarctic baseline aerosol scattering coefficient, total particle number concentration, and particle number size distribution (PNSD as measured at Troll Atmospheric Observatory. Mie-theory shows that the annual cycles in microphysical and optical aerosol properties have a common cause. By comparison with observations at other Antarctic stations, it is shown that the annual cycle is not a local phenomenon, but common to Central Antarctic baseline air masses. Observations of ground-level ozone at Troll as well as backward plume calculations for the air masses arriving at Troll demonstrate that the baseline air masses originate from the free troposphere and lower stratosphere region, and descend over the Central Antarctic continent. The Antarctic summer PNSD is dominated by particles with diameters 3/(MJ m. Further research is proposed to investigate the applicability of this number to other atmospheric reservoirs, and to use the observed annual cycle in Antarctic baseline aerosol properties as a benchmark for the representation of natural atmospheric aerosol processes in climate models.

  8. 浮游植物动力学模型及其在海域富营养化研究中的应用%REVIEW ON THE NUMERICAL MODELS OF PHYTOPLANKTON DYNAMICS AND THEIR APPLICATION IN ENVIRONMENT MANAGEMENT OF EUTROPHICATION

    Institute of Scientific and Technical Information of China (English)

    魏皓; 赵亮; 武建平

    2001-01-01

    The numerical models of phytoplankton dynamics can reproduce t hespatial and temporal variation of alge and quantify the contributions of all physical and biological processes involved in phytoplankton production. It takes a great role when studying the eutrophication of coastal sea. A brief review on the model's development is given. Time-dependent water column model is the ini tial state of physical-biological couplling. Vertical resolved model, horizont al box model and three-dimensional model can simulate the annual cycle of bioma ss. Short-term model studies show a great importance of the short-time physica l processes to the evolution of marine ecosystem. More nutrients and function gr oups are included in the eutrophyication models. They must reproduce the variati on of phytoplankton biomass at first. Then the response of the sea to the strate gy of nutrient deduction can be investigated. More attention should be pay on th e driven and boundary processes in our modelling studies.%浮游植物动力学模型用来研究特定海域浮游植物生物量的时空分布规律,定量确定各种物理、生物过程的贡献,对解决浮游植物生物量异常增加导致的富营养化问题具有至关重要的作用。综述了国内外海洋浮游植物动力学模型研究的发展过程和现状,介绍了几种不同时空尺度浮游植物动力学模型的特点和性能。此类模型在发达国家的海域富营养化研究和环境管理中已取得了相当的进展,而我国目前虽已开展了海洋生态模型的初步研究,但面临一些困难,其中不仅需要获取特定海域的过程参数,而且急需对海域的强迫过程和边界过程加强认识。

  9. Sedimentation of phytoplankton during a diatom bloom : Rates and mechanisms

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Hansen, J.L.S.; Alldredge, A.L.;

    1996-01-01

    Phytoplankton blooms are uncoupled from grazing and are normally terminated by sedimentation. There are several potential mechanisms by which phytoplankton cells may settle out of the photic zone: sinking of individual cells or chains, coagulation of cells into aggregates with high settling...... fjord, and evaluated their potential to control phytoplankton population dynamics. Overall specific sedimentation rates of intact phytoplankton cells were low during the Ii-day study period, averaging ca. 0.1 d(-1), and mass sedimentation and bloom termination did not occur. Most cells settled attached...... to marine snow aggregates formed from discarded larvacean houses, whereas settling of unaggregated cells was insignificant. Formation rates of phytoplankton aggregates by physical coagulation was very low, and losses by this mechanism were much less than 0.07 d(-1); phytoplankton aggregates were...

  10. Paleogeographic controls on the onset of the Antarctic circumpolar current

    Science.gov (United States)

    Hill, Daniel J.; Haywood, Alan M.; Valdes, Paul J.; Francis, Jane E.; Lunt, Daniel J.; Wade, Bridget S.; Bowman, Vanessa C.

    2013-10-01

    of the Antarctic Circumpolar Current (ACC) during the Cenozoic is controversial in terms of timing and its role in major climate transitions. Some propose that the development of the ACC was instrumental in the continental scale glaciation of Antarctica and climate cooling at the Eocene/Oligocene boundary. Here we present climate model results that show that a coherent ACC was not possible during the Oligocene due to Australasian paleogeography, despite deep water connections through the Drake Passage and Tasman Gateway and the initiation of Antarctic glaciation. The simulations of ocean currents compare well to paleoenvironmental records relating to the physical oceanography of the Oligocene and provide a framework for understanding apparently contradictory dating of the initiation of the ACC. We conclude that the northward motion of the Australasian land masses and the reconfiguration of the Tasman Seaway and Drake Passage are necessary preconditions for the formation of a strong, coherent ACC.

  11. A database of marine phytoplankton abundance, biomass and species composition in Australian waters.

    Science.gov (United States)

    Davies, Claire H; Coughlan, Alex; Hallegraeff, Gustaaf; Ajani, Penelope; Armbrecht, Linda; Atkins, Natalia; Bonham, Prudence; Brett, Steve; Brinkman, Richard; Burford, Michele; Clementson, Lesley; Coad, Peter; Coman, Frank; Davies, Diana; Dela-Cruz, Jocelyn; Devlin, Michelle; Edgar, Steven; Eriksen, Ruth; Furnas, Miles; Hassler, Christel; Hill, David; Holmes, Michael; Ingleton, Tim; Jameson, Ian; Leterme, Sophie C; Lønborg, Christian; McLaughlin, James; McEnnulty, Felicity; McKinnon, A David; Miller, Margaret; Murray, Shauna; Nayar, Sasi; Patten, Renee; Pritchard, Tim; Proctor, Roger; Purcell-Meyerink, Diane; Raes, Eric; Rissik, David; Ruszczyk, Jason; Slotwinski, Anita; Swadling, Kerrie M; Tattersall, Katherine; Thompson, Peter; Thomson, Paul; Tonks, Mark; Trull, Thomas W; Uribe-Palomino, Julian; Waite, Anya M; Yauwenas, Rouna; Zammit, Anthony; Richardson, Anthony J

    2016-01-01

    There have been many individual phytoplankton datasets collected across Australia since the mid 1900s, but most are unavailable to the research community. We have searched archives, contacted researchers, and scanned the primary and grey literature to collate 3,621,847 records of marine phytoplankton species from Australian waters from 1844 to the present. Many of these are small datasets collected for local questions, but combined they provide over 170 years of data on phytoplankton communities in Australian waters. Units and taxonomy have been standardised, obviously erroneous data removed, and all metadata included. We have lodged this dataset with the Australian Ocean Data Network (http://portal.aodn.org.au/) allowing public access. The Australian Phytoplankton Database will be invaluable for global change studies, as it allows analysis of ecological indicators of climate change and eutrophication (e.g., changes in distribution; diatom:dinoflagellate ratios). In addition, the standardised conversion of abundance records to biomass provides modellers with quantifiable data to initialise and validate ecosystem models of lower marine trophic levels. PMID:27328409

  12. A database of marine phytoplankton abundance, biomass and species composition in Australian waters

    Science.gov (United States)

    Davies, Claire H.; Coughlan, Alex; Hallegraeff, Gustaaf; Ajani, Penelope; Armbrecht, Linda; Atkins, Natalia; Bonham, Prudence; Brett, Steve; Brinkman, Richard; Burford, Michele; Clementson, Lesley; Coad, Peter; Coman, Frank; Davies, Diana; Dela-Cruz, Jocelyn; Devlin, Michelle; Edgar, Steven; Eriksen, Ruth; Furnas, Miles; Hassler, Christel; Hill, David; Holmes, Michael; Ingleton, Tim; Jameson, Ian; Leterme, Sophie C.; Lønborg, Christian; McLaughlin, James; McEnnulty, Felicity; McKinnon, A. David; Miller, Margaret; Murray, Shauna; Nayar, Sasi; Patten, Renee; Pritchard, Tim; Proctor, Roger; Purcell-Meyerink, Diane; Raes, Eric; Rissik, David; Ruszczyk, Jason; Slotwinski, Anita; Swadling, Kerrie M.; Tattersall, Katherine; Thompson, Peter; Thomson, Paul; Tonks, Mark; Trull, Thomas W.; Uribe-Palomino, Julian; Waite, Anya M.; Yauwenas, Rouna; Zammit, Anthony; Richardson, Anthony J.

    2016-01-01

    There have been many individual phytoplankton datasets collected across Australia since the mid 1900s, but most are unavailable to the research community. We have searched archives, contacted researchers, and scanned the primary and grey literature to collate 3,621,847 records of marine phytoplankton species from Australian waters from 1844 to the present. Many of these are small datasets collected for local questions, but combined they provide over 170 years of data on phytoplankton communities in Australian waters. Units and taxonomy have been standardised, obviously erroneous data removed, and all metadata included. We have lodged this dataset with the Australian Ocean Data Network (http://portal.aodn.org.au/) allowing public access. The Australian Phytoplankton Database will be invaluable for global change studies, as it allows analysis of ecological indicators of climate change and eutrophication (e.g., changes in distribution; diatom:dinoflagellate ratios). In addition, the standardised conversion of abundance records to biomass provides modellers with quantifiable data to initialise and validate ecosystem models of lower marine trophic levels. PMID:27328409

  13. Underwater Optics in Sub-Antarctic and Antarctic Coastal Ecosystems.

    Science.gov (United States)

    Huovinen, Pirjo; Ramírez, Jaime; Gómez, Iván

    2016-01-01

    Understanding underwater optics in natural waters is essential in evaluating aquatic primary production and risk of UV exposure in aquatic habitats. Changing environmental conditions related with global climate change, which imply potential contrasting changes in underwater light climate further emphasize the need to gain insights into patterns related with underwater optics for more accurate future predictions. The present study evaluated penetration of solar radiation in six sub-Antarctic estuaries and fjords in Chilean North Patagonian region (39-44°S) and in an Antarctic bay (62°S). Based on vertical diffuse attenuation coefficients (Kd), derived from measurements with a submersible multichannel radiometer, average summer UV penetration depth (z1%) in these water bodies ranged 2-11 m for UV-B (313 nm), 4-27 m for UV-A (395 nm), and 7-30 m for PAR (euphotic zone). UV attenuation was strongest in the shallow Quempillén estuary, while Fildes Bay (Antarctica) exhibited the highest transparency. Optically non-homogeneous water layers and seasonal variation in transparency (lower in winter) characterized Comau Fjord and Puyuhuapi Channel. In general, multivariate analysis based on Kd values of UV and PAR wavelengths discriminated strongly Quempillén estuary and Puyuhuapi Channel from other study sites. Spatial (horizontal) variation within the estuary of Valdivia river reflected stronger attenuation in zones receiving river impact, while within Fildes Bay a lower spatial variation in water transparency could in general be related to closeness of glaciers, likely due to increased turbidity through ice-driven processes. Higher transparency and deeper UV-B penetration in proportion to UV-A/visible wavelengths observed in Fildes Bay suggests a higher risk for Antarctic ecosystems reflected by e.g. altered UV-B damage vs. photorepair under UV-A/PAR. Considering that damage repair processes often slow down under cool temperatures, adverse UV impact could be further

  14. Underwater Optics in Sub-Antarctic and Antarctic Coastal Ecosystems.

    Science.gov (United States)

    Huovinen, Pirjo; Ramírez, Jaime; Gómez, Iván

    2016-01-01

    Understanding underwater optics in natural waters is essential in evaluating aquatic primary production and risk of UV exposure in aquatic habitats. Changing environmental conditions related with global climate change, which imply potential contrasting changes in underwater light climate further emphasize the need to gain insights into patterns related with underwater optics for more accurate future predictions. The present study evaluated penetration of solar radiation in six sub-Antarctic estuaries and fjords in Chilean North Patagonian region (39-44°S) and in an Antarctic bay (62°S). Based on vertical diffuse attenuation coefficients (Kd), derived from measurements with a submersible multichannel radiometer, average summer UV penetration depth (z1%) in these water bodies ranged 2-11 m for UV-B (313 nm), 4-27 m for UV-A (395 nm), and 7-30 m for PAR (euphotic zone). UV attenuation was strongest in the shallow Quempillén estuary, while Fildes Bay (Antarctica) exhibited the highest transparency. Optically non-homogeneous water layers and seasonal variation in transparency (lower in winter) characterized Comau Fjord and Puyuhuapi Channel. In general, multivariate analysis based on Kd values of UV and PAR wavelengths discriminated strongly Quempillén estuary and Puyuhuapi Channel from other study sites. Spatial (horizontal) variation within the estuary of Valdivia river reflected stronger attenuation in zones receiving river impact, while within Fildes Bay a lower spatial variation in water transparency could in general be related to closeness of glaciers, likely due to increased turbidity through ice-driven processes. Higher transparency and deeper UV-B penetration in proportion to UV-A/visible wavelengths observed in Fildes Bay suggests a higher risk for Antarctic ecosystems reflected by e.g. altered UV-B damage vs. photorepair under UV-A/PAR. Considering that damage repair processes often slow down under cool temperatures, adverse UV impact could be further

  15. Understanding the extent of universality in phytoplankton spatial properties

    OpenAIRE

    van Gennip, Simon Jan

    2014-01-01

    Phytoplankton are one of the most visible signs of life in our oceans. They also are a key component of the global carbon cycle and of the marine food web. Their complex patterns at the sea surface are routinely seen in satellite images, though the first observations go back centuries. The motivation of this thesis is to explore the spatial properties of phytoplankton. Inspired by ‘universal’ theories for the dynamics of turbulence, several ones have been proposed to explain phytoplankton...

  16. Tilapia rendalli increases phytoplankton biomass of a shallow tropical lake

    OpenAIRE

    Lúcia Helena Sampaio da Silva; Marlene Sofia Arcifa; Gian Salazar-Torres; Vera Lúcia de Moraes Huszar

    2014-01-01

    AIM: This study aimed to experimentally test the influence of a planktivorous filter-feeding fish (Tilapia rendalli) on the phytoplankton dynamics of a small and shallow tropical reservoir (Lake Monte Alegre, Brazil). Adults of T. rendalli of this lake feed preferentially on phytoplankton, and we hypothesize that: I) adults of T. rendalli will decrease the phytoplankton biomass and composition through direct herbivory, and II) as it is a eutrophic system, fish would not have strong influence ...

  17. A REVIEW OF PHYTOPLANKTON ECOLOGY IN FRESHWATER LAKES OF INDIA

    OpenAIRE

    Giripunje, Manisha D; Fulke, Abhay B; Khairnar, Krishna; P. U. MESHRAM; Waman N. PAUNIKAR

    2013-01-01

    This is a comprehensive review of phytoplankton ecology in freshwater lakes of India. A review study was undertaken for the better understanding of the phytoplankton distribution. In broad terms, authors discussed the relations of phytoplankton with factors like lake temperature, sunlight exposure period, sunlight penetration, water pH, wind, transparency, seasonal variations, water characteristics, nutrient enrichment and prey-predator relation in the lakes of India. From the results, author...

  18. Phytoplankton composition of Sazlidere Dam lake, Istanbul, Turkey

    OpenAIRE

    Nese Yilmaz

    2013-01-01

    The phytoplankton composition of Sazlidere Dam lake was studied at 5 sampling sites between December 2003 - November 2005. A total of 67 taxa were recorded, representing Bacillariophyta (31), Chlorophyta (18), Cyanophyta (9), Chrysophyta (1), Cryptophyta (1), Dinophyta (3) and Euglenophyta (4). Bacillariophyta members constituted the dominant phytoplankton group in terms of species number. Nygaard’s compound index value and composition of phytoplankton indicate that the trophic state of Sazli...

  19. A Taxonomic Study on the Phytoplankton of Lake Uluabat (Bursa)

    OpenAIRE

    KARACAOĞLU, Didem; DERE, Şükran; DALKIRAN, Nurhayat

    2004-01-01

    The phytoplanktonic algal flora of Lake Uluabat was studied during July 1998- June 1999 by analysing samples taken each month from 5 sampling stations. Identified taxa (331) of the phytoplanktonic community are as follows: 152 Bacillariophyta, 89 Chlorophyta, 42 Cyanophyta, 31 Euglenophyta, 11 Dinophyta, 4 Cryptophyta and 2 Chrysophyta. Algal species which live in eutrophic water are dominant in the phytoplankton. Most of the species are characterised by their widespread presence, although it...

  20. A comparison of phytoplankton and total particle counts

    OpenAIRE

    Beattie, I.H.

    1981-01-01

    Phytoplankton counts made under the light microscope were compared to counts using an electronic dimensional particle counter. Counts were made on a monthly basis, on water samples taken from one station in the Sanyati Basin. Neither total particle numbers nor total particle volume compare closely with phytoplankton numbers. Total particle numbers were of the order of one and a half to two times greater than the phytoplankton numbers.

  1. Phytoplankton assemblage of a solar saltern in Port Fouad, Egypt

    OpenAIRE

    Fedekar Fadel Madkour; Mona Mohamed Gaballah

    2012-01-01

    The present study is the first investigation of the phytoplankton community inone of Egypt's saltworks. The phytoplankton composition and distribution infive ponds of increasing salinity were investigated in the solar saltern of Port Fouad.The phytoplankton community consisted of 42 species belonging to cyanobacteria(16), diatoms (12), dinoflagellates (11), Euglenophyceae (2) and Chlorophyceae (1).The number of species decreased significantly and rapidly with increasing salinity,varying betw...

  2. Seasonal Distribution of Phytoplankton in Orduzu Dam Lake (Malatya, Turkey)

    OpenAIRE

    ÇETİN, A. Kadri

    2004-01-01

    The species composition and seasonal distribution of phytoplankton in Orduzu Dam Lake was studied for a year. Diatoms (Bacillariophyta) were most diverse, followed by green algae (Chlorophyta), blue-green algae (Cyanophyta), euglenoids (Euglenophyta) and dinoflagellates (Dinophyta). A total of 117 taxa were recorded and the phytoplankton of the lake contained a large number of detached benthic algae. Phytoplankton assemblages were dominated by diatoms in all the periods investigated and centr...

  3. Phytoplankton composition of Sazlidere Dam lake, Istanbul, Turkey

    Directory of Open Access Journals (Sweden)

    Nese Yilmaz

    2013-05-01

    Full Text Available The phytoplankton composition of Sazlidere Dam lake was studied at 5 sampling sites between December 2003 - November 2005. A total of 67 taxa were recorded, representing Bacillariophyta (31, Chlorophyta (18, Cyanophyta (9, Chrysophyta (1, Cryptophyta (1, Dinophyta (3 and Euglenophyta (4. Bacillariophyta members constituted the dominant phytoplankton group in terms of species number. Nygaard’s compound index value and composition of phytoplankton indicate that the trophic state of Sazlidere Dam lake was changing from oligotrophic to mesotrophic.

  4. Effects of warming on the phytoplankton succession and trophic interactions

    OpenAIRE

    Lewandowska, Aleksandra M.

    2011-01-01

    There is now a good evidence of ecological impacts of recent climate change on ecosystems worldwide. A major challenge in climate change research on phytoplankton succession is to understand the multiple factors, which drive ecological changes in phytoplankton communities. Increasing sea surface temperature is likely to alter phytoplankton bloom dynamic, phenology and community structure. Recent studies on the global primary production showed decline in size and productivity of marine phytopl...

  5. Complementary impact of copepods and cladocerans on phytoplankton

    OpenAIRE

    Sommer, Ulrich; Sommer, Frank; Santer, Barbara; Jamieson, Colleen; Boersma, Maarten; Becker, Claes; Hansen, Thomas

    2001-01-01

    The differences in the impact of two major groups of herbivorous zooplankton (Cladocera and Copepoda) on summer phytoplankton in a mesotrophic lake were studied. Field experiments were performed in which phytoplankton were exposed to different densities of two major types of herbivorous zooplankton, cladocerans and copepods. Contrary to expectation, neither of the two zooplankton groups significantly reduced phytoplankton biomass. However, there were strong and contrasting impacts on phytopla...

  6. Climate-mediated changes to mixed-layer properties in the Southern Ocean: assessing the phytoplankton response

    Directory of Open Access Journals (Sweden)

    P. W. Boyd

    2007-11-01

    Full Text Available Concurrent changes in ocean chemical and physical properties influence phytoplankton dynamics via alterations in carbonate chemistry, nutrient and trace metal inventories and upper ocean light environment. Using a fully coupled, global carbon-climate model (Climate System Model 1.4-carbon, we quantify anthropogenic climate change relative to the background natural interannual variability for the Southern Ocean over the period 2000 and 2100. Model results are interpreted using our understanding of the environmental control of phytoplankton growth rates – leading to two major findings. Firstly, comparison with results from phytoplankton perturbation experiments, in which environmental properties have been altered for key species (e.g., bloom formers, indicates that the predicted rates of change in oceanic properties over the next few decades are too subtle to be represented experimentally at present. Secondly, the rate of secular climate change will not exceed background natural variability, on seasonal to interannual time-scales, for at least several decades – which may not provide the prevailing conditions of change, i.e. constancy, needed for phytoplankton adaptation. Taken together, the relatively subtle environmental changes, due to climate change, may result in adaptation by resident phytoplankton, but not for several decades due to the confounding effects of climate variability. This presents major challenges for the detection and attribution of climate change effects on Southern Ocean phytoplankton. We advocate the development of multi-faceted tests/metrics that will reflect the relative plasticity of different phytoplankton functional groups and/or species to respond to changing ocean conditions.

  7. Evaluation of Antarctic polar stratospheric clouds data obtained by ground based lidars (at Dome C, McMurdo and Dumont D'Urville) and the satellite based CALIOP lidar system versus a subset of CCMVAL-2 chemistry-climate models.

    Science.gov (United States)

    Snels, Marcel; Fierli, Federico; de Muro, Mauro; Cagnazzo, Chiara; Cairo, Francesco; Di Liberto, Luca

    2016-04-01

    Polar stratospheric clouds play an important role in the ozone depletion process in polar regions and are thus strongly linked to climate changes. Long term observations are needed to monitor the presence of PSCs and to compare to climate models. The last decades PSCs in Antarctica have been observed by using the CALIOP lidar system on the CALIPSO satellite and by ground based lidars at Dumont D'Urville, McMurdo, Casey, and since 2014 at Dome C. We evaluate the Antarctic PSC observational databases of CALIPSO and the ground-based lidars of NDACC (Network for Detection of Atmospheric Composition Changes) located in McMurdo and Dumont D'Urville and Dome C stations and provide a process-oriented evaluation of PSC in a subset of CCMVAL-2 chemistry-climate models. Lidar observatories have a decadal coverage, albeit with discontinuities, spanning from 1992 to today hence offering a unique database. A clear issue is the representativeness of ground-based long-term data series of the Antarctic stratosphere conditions that may limit their value in climatological studies and model evaluation. The comparison with the CALIPSO observations with a global coverage is, hence, a key issue. In turn, models can have a biased representation of the stratospheric conditions and of the PSC microphysics leading to large discrepancies in PSC occurrence and composition. Point-to-point comparison is difficult due to sparseness of the database and to intrinsic differences in spatial distribution between models and observations. However, a statistical analysis of PSC observations shows a satisfactory agreement between ground-based and satellite borne-lidar. The differences may be attributed to averaging processes for data with a bad signal to noise ratio, which tends to smear out the values of the optical parameters. Data from some Chemistry Climate models (CCMs) having provided PSC surface areas on daily basis have been evaluated using the same diagnostic type that may be derived CALIPSO (i

  8. On the Atmospheric Correction of Antarctic Airborne Hyperspectral Data

    Directory of Open Access Journals (Sweden)

    Martin Black

    2014-05-01

    Full Text Available The first airborne hyperspectral campaign in the Antarctic Peninsula region was carried out by the British Antarctic Survey and partners in February 2011. This paper presents an insight into the applicability of currently available radiative transfer modelling and atmospheric correction techniques for processing airborne hyperspectral data in this unique coastal Antarctic environment. Results from the Atmospheric and Topographic Correction version 4 (ATCOR-4 package reveal absolute reflectance values somewhat in line with laboratory measured spectra, with Root Mean Square Error (RMSE values of 5% in the visible near infrared (0.4–1 µm and 8% in the shortwave infrared (1–2.5 µm. Residual noise remains present due to the absorption by atmospheric gases and aerosols, but certain parts of the spectrum match laboratory measured features very well. This study demonstrates that commercially available packages for carrying out atmospheric correction are capable of correcting airborne hyperspectral data in the challenging environment present in Antarctica. However, it is anticipated that future results from atmospheric correction could be improved by measuring in situ atmospheric data to generate atmospheric profiles and aerosol models, or with the use of multiple ground targets for calibration and validation.

  9. Microbial ecology of Antarctic aquatic systems.

    Science.gov (United States)

    Cavicchioli, Ricardo

    2015-11-01

    The Earth's biosphere is dominated by cold environments, and the cold biosphere is dominated by microorganisms. Microorganisms in cold Southern Ocean waters are recognized for having crucial roles in global biogeochemical cycles, including carbon sequestration, whereas microorganisms in other Antarctic aquatic biomes are not as well understood. In this Review, I consider what has been learned about Antarctic aquatic microbial ecology from 'omic' studies. I assess the factors that shape the biogeography of Antarctic microorganisms, reflect on some of the unusual biogeochemical cycles that they are associated with and discuss the important roles that viruses have in controlling ecosystem function.

  10. Bacterial productivity in the Prydz Bay and its adjacent waters,Antarctic

    Institute of Scientific and Technical Information of China (English)

    邱雨生; 黄奕普; 陈敏; 刘广山

    2004-01-01

    Bacterial productivity was measured using 3H-thymidine methods in the Prydz Bay and its adjacent waters in the Southern Ocean during the 16th National Antarctic Research Expedition of China (CHINARE). The results showed that bacteted for the Ross Sea. The mean ratio of bacterial productivity to primary productivity in our study areas was 41%. The general characteristics in the vertical profiles showed a subsurface maximum at most of the stations, which was also consistent with those observed in the other sea areas in the Southern Ocean. The spatial distribution of bacterial productivity and dissolved organic carbon in the surface waters showed that their variations were inversely correlative. The relationship among bacterial productivity, primary productivity and dissolved organic carbon suggested that bacterial productivity in the Prydz Bay and its adjacent water was influenced mostly by phytoplankton activities and the hydrologic conditions.

  11. Responses of Antarctic Oscillation to global warming

    Science.gov (United States)

    Feng, S.

    2015-12-01

    The Antarctic Oscillation (AAO) is the major annular mode dominates the spatiotemporal variability of the atmospheric circulation in the Southern Hemisphere. This study examined the sensitivity of AAO to future warming by analyzing the outputs of 34 state-of-the-art climate models participating in phase 5 of the Coupled Model Intercomparion Project (CMIP5). The model simulations include the stabilized (RCP4.5) and business as usual (RCP8.5) scenarios as well as the idealized 1% per year increase in atmospheric CO2 to quadrupling (1pctCO2) and an instantaneous quadrupling of CO2 (abrupt4xCO2). We show that the CMIP5 models on average simulate increases in the AAO in every season by 2100 under the RCP4.5 and RCP8.5 scenarios. However, due to the impacts of ozone, aerosol and land use changes, the amplitudes of the projected changes in AAO to future climate scenarios are quit different on different seasons. After the impact of ozone, aerosol and land use changes were removed; it was found that the impact of greenhouse gases (GHGs) on AAO is similar on all seasons. The increases of AAO are accelerating following the increase of GHGs. Our results are also consistent with the simulations of 1pctCO2 and abrupt4xCO2.

  12. The Effects of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in an AOGCM

    Science.gov (United States)

    Li, Feng; Newman, Paul; Pawson, Steven; Waugh, Darryn

    2014-01-01

    Stratospheric ozone depletion has played a dominant role in driving Antarctic climate change in the last decades. In order to capture the stratospheric ozone forcing, many coupled atmosphere-ocean general circulation models (AOGCMs) prescribe the Antarctic ozone hole using monthly and zonally averaged ozone field. However, the prescribed ozone hole has a high ozone bias and lacks zonal asymmetry. The impacts of these biases on model simulations, particularly on Southern Ocean and the Antarctic sea ice, are not well understood. The purpose of this study is to determine the effects of using interactive stratospheric chemistry instead of prescribed ozone on Antarctic and Southern Ocean climate change in an AOGCM. We compare two sets of ensemble simulations for the 1960-2010 period using different versions of the Goddard Earth Observing System 5 - AOGCM: one with interactive stratospheric chemistry, and the other with prescribed monthly and zonally averaged ozone and 6 other stratospheric radiative species calculated from the interactive chemistry simulations. Consistent with previous studies using prescribed sea surface temperatures and sea ice concentrations, the interactive chemistry runs simulate a deeper Antarctic ozone hole and consistently larger changes in surface pressure and winds than the prescribed ozone runs. The use of a coupled atmosphere-ocean model in this study enables us to determine the impact of these surface changes on Southern Ocean circulation and Antarctic sea ice. The larger surface wind trends in the interactive chemistry case lead to larger Southern Ocean circulation trends with stronger changes in northerly and westerly surface flow near the Antarctica continent and stronger upwelling near 60S. Using interactive chemistry also simulates a larger decrease of sea ice concentrations. Our results highlight the importance of using interactive chemistry in order to correctly capture the influences of stratospheric ozone depletion on climate

  13. Progressive decoupling between phytoplankton growth and microzooplankton grazing during an iron-induced phytoplankton bloom in the Southern Ocean (EIFEX)

    OpenAIRE

    M. Latasa; Henjes, J.; R. Scharek; Assmy, P.; R. Röttgers; Smetacek, V.

    2014-01-01

    Dilution experiments were performed to quantify growth and mortality rates of phytoplankton groups (as defined by pigment markers) for 5 wk in an iron-induced phytoplankton bloom during the European Iron Fertilization Experiment (EIFEX) conducted in the Southern Ocean. Rates could be reliably measured for the 2 main groups, diatoms and prymnesiophytes. Mean phytoplankton intrinsic growth rates were around 0.23 d−1, without a significant temporal trend. Mortality rates, however,...

  14. Validation and Assessment on the Bio-optical Models for Retrieving Phytoplankton Size Structure in the Northern South China Sea%南海北部海区浮游植物粒级结构生物光学反演模型的验证与评价

    Institute of Scientific and Technical Information of China (English)

    王桂芬; 周雯; 林俊芳; 王国青; 赵文静; 曹文熙

    2014-01-01

    Phytoplankton size distribution is an important biological factor in marine ecosystem.Estimating phytoplank-ton size classes (PSC)based on bio-optical models has been a hot topic in recent studies about ocean color remote sens-ing.Based on a large dataset collected in the Northern South China Sea,several of these models were validated against in situ observation after locally parameterized,and the ability to detect dominant phytoplankton size classes (micro-, nano-,and Pico plankton)was evaluated.Results show that the dominant roles of micro-and pico-plankton can be gen-erally discriminated according to the chlorophyll a concentration (Chl a)and phytoplankton absorption coefficients (aph (443)with high accuracy compared with the low accuracy for nano-plankton.The size parameter deduced from the nor-malized phytoplankton spectragenerally shows the trend of PSC.Variations of size-specific chlorophyll a concentration with the total Chl a can be described with the simple three component model,especially for the picoplankton.The PSC retrieval algorithm was further optimized by coupling aph (λ) and total [Chl a]which improved the accuvacy for micro-and nano-plankton.%浮游植物粒级结构是海洋生态系统中的一个重要生物学因子。基于生物光学参数反演浮游植物粒级结构变化是当前水色遥感研究的热点问题。本文综合南海北部海区多年航次调查数据,对现有几类反演算法进行了区域性优化和验证评价。根据叶绿素 a 浓度(Chl a)或浮游植物吸收系数(aph (443))的阈值可实现南海北部海区小型(Micro)和微微型(Pico)浮游植物主导的划分,微型(Nano)的判别精度较差。基于归一化吸收光谱提取的粒级指数可定性地表征浮游植物粒级结构的综合变化趋势。基于叶绿素 a 浓度的三组分模型,较好地模拟浮游植物粒级结构的变化规律,可实现分粒级叶绿素 a 浓度的定量反演,Pico 粒

  15. Centripetal focusing of gyrotactic phytoplankton.

    Science.gov (United States)

    Cencini, M; Franchino, M; Santamaria, F; Boffetta, G

    2016-06-21

    A suspension of gyrotactic microalgae Chlamydomonas augustae swimming in a cylindrical water vessel in solid-body rotation is studied. Our experiments show that swimming algae form an aggregate around the axis of rotation, whose intensity increases with the rotation speed. We explain this phenomenon by the centripetal orientation of the swimming direction towards the axis of rotation. This centripetal focusing is contrasted by diffusive fluxes due to stochastic reorientation of the cells. The competition of the two effects lead to a stationary distribution, which we analytically derive from a refined mathematical model of gyrotactic swimmers. The temporal evolution of the cell distribution, obtained via numerical simulations of the stochastic model, is in quantitative agreement with the experimental measurements in the range of parameters explored. PMID:27060672

  16. Effects of African dust deposition on phytoplankton in the western tropical Atlantic Ocean off Barbados

    Science.gov (United States)

    Chien, Chia-Te; Mackey, Katherine R. M.; Dutkiewicz, Stephanie; Mahowald, Natalie M.; Prospero, Joseph M.; Paytan, Adina

    2016-05-01

    Bioassay incubation experiments conducted with nutrients and local atmospheric aerosol amendments indicate that phosphorus (P) availability limited phytoplankton growth in the low-nutrient low-chlorophyll (LNLC) ocean off Barbados. Atmospheric deposition provides a relatively large influx of new nutrients and trace metals to the surface ocean in this region in comparison to other nutrient sources. However, the impact on native phytoplankton is muted due to the high ratio of nitrogen (N) to P (NO3:SRP > 40) and the low P solubility of these aerosols. Atmospheric deposition induces P limitation in this LNLC region by adding more N and iron (Fe) relative to P. This favors the growth of Prochlorococcus, a genus characterized by low P requirements and highly efficient P acquisition mechanisms. A global three-dimensional marine ecosystem model that includes species-specific phytoplankton elemental quotas/stoichiometry and the atmospheric deposition of N, P, and Fe supports this conclusion. Future increases in aerosol N loading may therefore influence phytoplankton community structure in other LNLC areas, thereby affecting the biological pump and associated carbon sequestration.

  17. River flow and ammonium discharge determine spring phytoplankton blooms in an urbanized estuary

    Science.gov (United States)

    Dugdale, Richard; Wilkerson, Frances; Parker, Alexander E.; Marchi, Al; Taberski, Karen

    2012-12-01

    Nutrient loadings to urbanized estuaries have increased over the past decades in response to population growth and upgrading to secondary sewage treatment. Evidence from the San Francisco Estuary (SFE) indicates that increased ammonium (NH4) loads have resulted in reduced primary production, a counter-intuitive finding; the NH4 paradox. Phytoplankton uptake of nitrate (NO3), the largest pool of dissolved inorganic nitrogen, is necessary for blooms to occur in SFE. The relatively small pool of ambient NH4, by itself insufficient to support a bloom, prevents access to NO3 and bloom development. This has contributed to the current rarity of spring phytoplankton blooms in the northern SFE (Suisun Bay), in spite of high inorganic nutrient concentrations, improved water transparency and seasonally low biomass of bivalve grazers. The lack of blooms has likely contributed to deleterious bottom-up impacts on estuarine fish. This bloom suppression may also occur in other estuaries that receive large amounts of anthropogenic NH4. In 2010 two rare diatom blooms were observed in spring in Suisun Bay (followed by increased abundances of copepods and pelagic fish), and like the prior bloom observed in 2000, chlorophyll accumulated after NH4 concentrations were decreased. In 2010, low NH4 concentrations were apparently due to a combination of reduced NH4 discharge from a wastewater treatment plant and increased river flow. To understand the interactions of river flow, NH4 discharge and bloom initiation, a conceptual model was constructed with three criteria; 1) NH4 loading must not exceed the capacity of the phytoplankton to assimilate the inflow of NH4, 2) the NH4 concentration must be ≤4 μmol L-1 to enable phytoplankton NO3 uptake, 3) the dilution rate of phytoplankton biomass set by river flow must not exceed the phytoplankton growth rate to avoid "washout". These criteria were determined for Suisun Bay; with sufficient irradiance and present day discharge of 15 tons NH4-N d

  18. Monte Carlo Ray Tracing Simulation of Polarization Characteristics of Sea Water Which Contains Spherical and Non-Spherical Particles of Suspended Solid and Phytoplankton

    Directory of Open Access Journals (Sweden)

    Kohei Arai

    2012-06-01

    Full Text Available Simulation method of sea water which contains spherical and non-spherical particles of suspended solid and phytoplankton based on Monte Carlo Ray Tracing: MCRT is proposed for identifying non-spherical species of phytoplankton. From the simulation results, it is found that the proposed MCRT model is validated. Also some possibility of identification of spherical and non-spherical shapes of particles which are contained in sea water is shown. Meanwhile, simulations with the different shape of particles, Prolate and Oblate show that Degree of Polarization: DP depends on shapes. Therefore, non-spherical shape of phytoplankton can be identified with polarization characteristics measurements of the ocean.

  19. Program of the Antarctic Syowa MST/IS radar (PANSY)

    Science.gov (United States)

    Sato, K.; Tsutsumi, M.; Sato, T.; Saito, A.; Tomikawa, Y.; Aso, T.; Yamanouchi, T.; Ejiri, M.

    We have been promoting a project to introduce the first MST Mesosphere-Stratosphere-Troposphere IS Incoherent Scatter radar which is a VHF pulse Doppler radar in the Antarctic to Syowa Station 39E 69S Program of the Antarctic Syowa MST IS Radar PANSY as an important station observing the earth s environment with the aim to catch the climate change signals that the Antarctic atmosphere shows This radar consists of about 1000 crossed Yagi antennas having a peak power of 500kW which allows us to observe the Antarctic atmosphere with fine resolution and good accuracy in a wide height range of 1-500 km The interaction of the neutral atmosphere with the ionosphere and magnetosphere as well as the global-scale atmospheric circulation including the low and middle latitude regions are also targets of PANSY The observation data with high resolution and good accuracy obtained by the PANSY radar are also valuable from the viewpoint of certification of the reality of phenomena simulated by high-resolution numerical models The scientific importance of PANSY is discussed and resolved by international research organizations of IUGG URSI SCAR SCOSTEP and SPARC and documented in a report by Council of Science and Technology Policy in Japan One major issue for the operation of the MST IS radar at an isolated place such as Syowa Station is the reduction of power consumption We have developed a new power-efficient transmitter class-E amplifier and successfully reduced the needed power consumption to an acceptable

  20. Obliquity-paced Pliocene West Antarctic ice sheet oscillations

    Science.gov (United States)

    Naish, T.; Powell, R.; Levy, R.; Wilson, G.; Scherer, R.; Talarico, F.; Krissek, L.; Niessen, F.; Pompilio, M.; Wilson, T.; Carter, L.; DeConto, R.; Huybers, P.; McKay, R.; Pollard, D.; Ross, J.; Winter, D.; Barrett, P.; Browne, G.; Cody, R.; Cowan, E.; Crampton, J.; Dunbar, G.; Dunbar, N.; Florindo, F.; Gebhardt, C.; Graham, I.; Hannah, M.; Hansaraj, D.; Harwood, D.; Helling, D.; Henrys, S.; Hinnov, L.; Kuhn, G.; Kyle, P.; Laufer, A.; Maffioli, P.; Magens, D.; Mandernack, K.; McIntosh, W.; Millan, C.; Morin, R.; Ohneiser, C.; Paulsen, T.; Persico, D.; Raine, I.; Reed, J.; Riesselman, C.; Sagnotti, L.; Schmitt, D.; Sjunneskog, C.; Strong, P.; Taviani, M.; Vogel, S.; Wilch, T.; Williams, T.

    2009-01-01

    Thirty years after oxygen isotope records from microfossils deposited in ocean sediments confirmed the hypothesis that variations in the Earth's orbital geometry control the ice ages, fundamental questions remain over the response of the Antarctic ice sheets to orbital cycles. Furthermore, an understanding of the behaviour of the marine-based West Antarctic ice sheet (WAIS) during the 'warmer-than-present' early-Pliocene epoch (???5-3 Myr ago) is needed to better constrain the possible range of ice-sheet behaviour in the context of future global warming. Here we present a marine glacial record from the upper 600 m of the AND-1B sediment core recovered from beneath the northwest part of the Ross ice shelf by the ANDRILL programme and demonstrate well-dated, ???40-kyr cyclic variations in ice-sheet extent linked to cycles in insolation influenced by changes in the Earth's axial tilt (obliquity) during the Pliocene. Our data provide direct evidence for orbitally induced oscillations in the WAIS, which periodically collapsed, resulting in a switch from grounded ice, or ice shelves, to open waters in the Ross embayment when planetary temperatures were up to ???3??C warmer than today and atmospheric CO 2 concentration was as high as ???400 p.p.m.v. (refs 5, 6). The evidence is consistent with a new ice-sheet/ice-shelf model that simulates fluctuations in Antarctic ice volume of up to +7 m in equivalent sea level associated with the loss of the WAIS and up to +3 m in equivalent sea level from the East Antarctic ice sheet, in response to ocean-induced melting paced by obliquity. During interglacial times, diatomaceous sediments indicate high surface-water productivity, minimal summer sea ice and air temperatures above freezing, suggesting an additional influence of surface melt under conditions of elevated CO2. ??2009 Macmillan Publishers Limited. All rights reserved.

  1. Nitrogen and phosphorus intake by phytoplankton in the Xiamen Bay

    Science.gov (United States)

    Lin, Cai; Li, Hui; He, Qing; Xu, Kuncan; Wu, Shengsan; Zhang, Yuanbiao; Chen, Jinmin; Chen, Baohong; Lin, Libin; Lu, Meiluan; Chen, Weifen; Tang, Rongkun; Ji, Weidong

    2010-01-01

    This paper describes a time series experiment examining the nitrogen and phosphorus intake of natural phytoplankton communities by a microcosms approach. Seawater samples containing natural phytoplankton communities were collected from waters around Baozhu Islet in inner Xiamen Bay and around Qingyu Islet in the outer bay. The goal was to elucidate the relationship between phytoplankton population enhancement, the biological removal of nitrogen and phosphorus from the seawater, and the phytoplankton nitrogen and phosphorus intake ratio based on nitrogen and phosphorus removal from seawater by phytoplankton, to provide a basis for detecting prewarning conditions for red tide and the assessment of red tide events. Two key results were obtained: 1. During the experiment, the nitrogen and phosphorus seawater concentrations in samples from these two sites were negatively and closely correlated to the logarithm of the phytoplankton cell concentration and to the value of the apparent oxygen increment. The ratio of the intake coefficients was 3.5:1 for phosphorus and 1.1:1 for nitrogen for the phytoplankton between these samples from around Baozhu Islet and Qingyu Islet, respectively. This indicates that the intake capabilities of phytoplankton for nitrogen in the two waters are essentially identical. However, for phosphorus, the capability was much higher in the Baozhu Islet waters than the Qingyu Islet waters. In other words, the phytoplankton in Qingyu Islet waters produced more biomass while consuming the same amount of phosphorus as the other waters; 2. The phytoplankton nitrogen and phosphorus intake ratio from the Baozhu Islet and Qingyu Islet waters was 20:1 and 36:1, respectively. The latter waters had a significantly higher ratio than the former and both were higher than the Redfield Ratio. These results indicate that nitrogen and phosphorus intake ratios by phytoplankton can vary significantly from region to region.

  2. Abundance, viability and culturability of Antarctic bacteria

    Digital Repository Service at National Institute of Oceanography (India)

    LokaBharathi, P.A.; DeSouza, M.J.B.D.; Nair, S.; Chandramohan, D.

    The viability of total number of bacteria decide the mineralisation rate in any ecosystem and ultimately the fertility of the region. This study aims at establishing the extent of viability in the standing stock of the Antarctic bacterial population...

  3. Diagnosis of Physical and Biological Control over Phytoplankton in the Gulf of Maine-Georges Bank Region Using an Adjoint Data Assimilation Approach

    Institute of Scientific and Technical Information of China (English)

    WANG Caixia; Paola Malanotte-Rizzoli

    2014-01-01

    The linkage between physical and biological processes, particularly the effect of the circulation field on the distribution of phytoplankton, is studied by applying a two-dimensional model and an adjoint data assimilation approach to the Gulf of Maine-Georges Bank region. The model results, comparing well with observation data, reveal seasonal and geographic variations of phytoplankton concentration and verify that the seasonal cycles of phytoplankton are controlled by both biological sources and ad-vection processes which are functions of space and time and counterbalance each other. Although advective flux divergences have greater magnitudes on Georges Bank than in the coastal region of the western Gulf of Maine, advection control over phytoplankton concentration is more significant in the coastal region of the western Gulf of Maine. The model results also suggest that the two separated populations in the coastal regions of the western Gulf of Maine and on Georges Bank are self-sustaining.

  4. Designing an effective mark-recapture study of Antarctic blue whales.

    Science.gov (United States)

    Peel, David; Bravington, Mark; Kelly, Natalie; Double, Michael C

    2015-06-01

    To properly conserve and manage wild populations, it is important to have information on abundance and population dynamics. In the case of rare and cryptic species, especially in remote locations, surveys can be difficult and expensive, and run the risk of not producing sample sizes large enough to produce precise estimates. Therefore, it is crucial to conduct preliminary analysis to determine if the study will produce useable estimates. The focus of this paper is a proposed mark-recapture study of Antarctic blue whales (Balaenoptera musculus intermedia). Antarctic blue whales were hunted to near extinction up until the mid- 1960s, when commercial exploitation of this species ended. Current abundance estimates are a decade old. Furthermore, at present, there are no formal circumpolar-level cetacean surveys operating in Antarctic waters and, specifically, there is no strategy to monitor the potential recovery of Antarctic blue whales. Hence the work in this paper was motivated by the need to inform decisions on strategies for future monitoring of Antarctic blue whale population. The paper describes a model to predict the precision and bias of estimates from a proposed survey program. The analysis showed that mark-recapture is indeed a suitable method to provide a circumpolar abundance estimate of Antarctic blue whales, with precision of the abundance, at the midpoint of the program, predicted to be between 0.2 and 0.3. However, this was only if passive acoustic tracking was utilized to increase the encounter rate. The analysis also provided guidance on general design for an Antarctic blue whale program, showing that it requires a 12-year duration; although surveys do not necessarily need to be run every year if multiple vessels are available to clump effort. Mark-recapture is based on a number of assumptions; it was evident from the analysis that ongoing analysis and monitoring of the data would be required to check such assumptions hold (e.g., test for

  5. Breakup of Pack Ice, Antarctic Ice Shelf

    Science.gov (United States)

    1991-01-01

    Breakup of Pack Ice along the periphery of the Antarctic Ice Shelf (53.5S, 3.0E) produced this mosaic of ice floes off the Antarctic Ice Shelf. Strong offshore winds, probably associated with strong katabatic downdrafts from the interior of the continent, are seen peeling off the edges of the ice shelf into long filamets of sea ice, icebergs, bergy bits and growlers to flow northward into the South Atlantic Ocean. 53.5S, 3.0E

  6. COMMENT ON AEROSOL EFFECT ON ANTARCTIC OZONE

    OpenAIRE

    イワサカ, ヤスノブ; Yasunobu, IWASAKA; Guang-Yu, SHI

    1987-01-01

    The structure of the aerosol layer disturbed by a cold air was suggested from the lidar measurements at Syowa Station (69°00′S, 39°35′E). The particle layer containing sublayers of spherical or nonspherical aerosols was frequently observed in Antarctic spring. It is a point one sholud not ignore when he discusses aerosol effects on "Antarctic ozone depletion" through radiative processes and heterogeneous chemical reactions.

  7. Role of the meiobenthos in Antarctic ecosystems

    OpenAIRE

    Vanhove, S.; Wittoeck, J; Beghyn, M.; Van Gansbeke, D.; Van Kenhove, A.; Coomans, A.; Vincx, M.

    1997-01-01

    To date meiobenthic research remained a big white spot in the systematic-ecological work on Antarctic zoobenthos. Therefore the relative importance of the meiofauna (organisms within the size range of 38-1000µm) in the Antarctic benthic community has been assessed by a combined field ecology and experimental approach. This was done in two contrasting conditions, e.g. the deep sea and low subtidal, where as to the depth of the water column the benthic characteristics were, respectively, indire...

  8. The Scientific Committee on Antarctic Research (SCAR) in the IPY 2007-2009

    Science.gov (United States)

    Kennicutt, M. C.; Wilson, T. J.; Summerhayes, C.

    2005-05-01

    The Scientific Committee on Antarctic Research (SCAR) initiates, develops, and coordinates international scientific research in the Antarctic region. SCAR is assuming a leadership position in the IPY primarily through its five major Scientific Research Programs; ACE, SALE, EBA, AGCS, and ICESTAR; which will be briefly described.Antarctic Climate Evolution (ACE) promotes the exchange of data and ideas between research groups focusing on the evolution of Antarctica's climate system and ice sheet. The program will: (1) quantitatively assess the climate and glacial history of Antarctica; (2) identify the processes which govern Antarctic change and feed back around the globe; (3) improve our ability to model past changes in Antarctica; and (4)document past change to predict future change in Antarctica. Subglacial Antarctic Lake Environments (SALE) promotes, facilitates, and champions cooperation and collaboration in the exploration and study of subglacial environments in Antarctica. SALE intends to understand the complex interplay of biological, geological, chemical, glaciological, and physical processes within subglacial lake environments through coordinated international research teams. Evolution and Biodiversity in the Antarctic (EBA) will use a suite of modern techniques and interdisciplinary approaches, to explore the evolutionary history of selected modern Antarctic biota, examine how modern biological diversity in the Antarctic influences the way present-day ecosystems function, and thereby predict how the biota may respond to future environmental change. Antarctica and the Global Climate System (AGCS) will investigate the nature of the atmospheric and oceanic linkages between the climate of the Antarctic and the rest of the Earth system, and the mechanisms involved therein. A combination of modern instrumented records of atmospheric and oceanic conditions, and the climate signals held within ice cores will be used to understand past and future climate

  9. Advances through collaboration: sharing seismic reflection data via the Antarctic Seismic Data Library System for Cooperative Research (SDLS)

    Science.gov (United States)

    Wardell, N.; Childs, J. R.; Cooper, A. K.

    2007-01-01

    The Antarctic Seismic Data Library System for Cooperative Research (SDLS) has served for the past 16 years under the auspices of the Antarctic Treaty (ATCM Recommendation XVI-12) as a role model for collaboration and equitable sharing of Antarctic multichannel seismic reflection (MCS) data for geoscience studies. During this period, collaboration in MCS studies has advanced deciphering the seismic stratigraphy and structure of Antarctica’s continental margin more rapidly than previously. MCS data compilations provided the geologic framework for scientific drilling at several Antarctic locations and for high-resolution seismic and sampling studies to decipher Cenozoic depositional paleoenvironments. The SDLS successes come from cooperation of National Antarctic Programs and individual investigators in “on-time” submissions of their MCS data. Most do, but some do not. The SDLS community has an International Polar Year (IPY) goal of all overdue MCS data being sent to the SDLS by end of IPY. The community science objective is to compile all Antarctic MCS data to derive a unified seismic stratigraphy for the continental margin – a stratigraphy to be used with drilling data to derive Cenozoic circum-Antarctic paleobathymetry maps and local-to-regional scale paleoenvironmental histories.

  10. Quantifying interspecific coagulation efficiency of phytoplankton

    DEFF Research Database (Denmark)

    Hansen, J.L.S.; Kiørboe, Thomas

    1997-01-01

    the interspecific coagulation efficiency could be calculated. Stickiness between beads and T. nordenskjoeldii was 50% of that of T. nordenskjoeldii in monospecific suspensions, and this ratio remained constant throughout 12 experiments covering 1 order of magnitude variation in the stickiness level of T....... nordenskjoeldii. Mutual coagulation between Skeletonema costatum and the non-sticky cel:ls of Ditylum brightwellii also proceeded with hall the efficiency of S. costatum alone. The latex beads were suitable to be used as 'standard particles' to quantify the ability of phytoplankton to prime aggregation...

  11. Mid Pleistocene foraminiferal mass extinction coupled with phytoplankton evolution

    Science.gov (United States)

    Kender, Sev; McClymont, Erin L.; Elmore, Aurora C.; Emanuele, Dario; Leng, Melanie J.; Elderfield, Henry

    2016-06-01

    Understanding the interaction between climate and biotic evolution is crucial for deciphering the sensitivity of life. An enigmatic mass extinction occurred in the deep oceans during the Mid Pleistocene, with a loss of over 100 species (20%) of sea floor calcareous foraminifera. An evolutionarily conservative group, benthic foraminifera often comprise >50% of eukaryote biomass on the deep-ocean floor. Here we test extinction hypotheses (temperature, corrosiveness and productivity) in the Tasman Sea, using geochemistry and micropalaeontology, and find evidence from several globally distributed sites that the extinction was caused by a change in phytoplankton food source. Coccolithophore evolution may have enhanced the seasonal `bloom' nature of primary productivity and fundamentally shifted it towards a more intra-annually variable state at ~0.8 Ma. Our results highlight intra-annual variability as a potential new consideration for Mid Pleistocene global biogeochemical climate models, and imply that deep-sea biota may be sensitive to future changes in productivity.

  12. Assessment of phytoplankton class abundance using fluorescence excitation-emission matrix by parallel factor analysis and nonnegative least squares

    Science.gov (United States)

    Su, Rongguo; Chen, Xiaona; Wu, Zhenzhen; Yao, Peng; Shi, Xiaoyong

    2015-07-01

    The feasibility of using fluorescence excitation-emission matrix (EEM) along with parallel factor analysis (PARAFAC) and nonnegative least squares (NNLS) method for the differentiation of phytoplankton taxonomic groups was investigated. Forty-one phytoplankton species belonging to 28 genera of five divisions were studied. First, the PARAFAC model was applied to EEMs, and 15 fluorescence components were generated. Second, 15 fluorescence components were found to have a strong discriminating capability based on Bayesian discriminant analysis (BDA). Third, all spectra of the fluorescence component compositions for the 41 phytoplankton species were spectrographically sorted into 61 reference spectra using hierarchical cluster analysis (HCA), and then, the reference spectra were used to establish a database. Finally, the phytoplankton taxonomic groups was differentiated by the reference spectra database using the NNLS method. The five phytoplankton groups were differentiated with the correct discrimination ratios (CDRs) of 100% for single-species samples at the division level. The CDRs for the mixtures were above 91% for the dominant phytoplankton species and above 73% for the subdominant phytoplankton species. Sixteen of the 85 field samples collected from the Changjiang River estuary were analyzed by both HPLC-CHEMTAX and the fluorometric technique developed. The results of both methods reveal that Bacillariophyta was the dominant algal group in these 16 samples and that the subdominant algal groups comprised Dinophyta, Chlorophyta and Cryptophyta. The differentiation results by the fluorometric technique were in good agreement with those from HPLC-CHEMTAX. The results indicate that the fluorometric technique could differentiate algal taxonomic groups accurately at the division level.

  13. Phytoplankton sinking rates in the Rhine region of freshwater influence

    NARCIS (Netherlands)

    Peperzak, L; Colijn, F; Koeman, R; Gieskes, WWC; Joordens, JCA

    2003-01-01

    According to Stokes' law, colony formation in phytoplankton would lead to enhanced sinking rates and higher sedimentation losses if colonies had the same densities as the phytoplankton cells they contain. In the Dutch coastal zone of the North Sea, algae settling out of the water column are subject

  14. Monitoring and prediction of phytoplankton dynamics in the North Sea

    NARCIS (Netherlands)

    A.N. Blauw

    2015-01-01

    Phytoplankton forms the base of the marine food web, but when concentrations get too high, algal blooms can have adverse effects on ecosystems and aquaculture. Phytoplankton concentrations vary strongly in space and time. However, the nature and drivers of this variability are not yet well understoo

  15. Does biodiversity of estuarine phytoplankton depend on hydrology?

    NARCIS (Netherlands)

    Ferreira, JG; Wolff, WJ; Simas, TC; Bricker, SB

    2005-01-01

    Phytoplankton growth in estuaries is controlled by factors such as flushing, salinity tolerance, light, nutrients and grazing. Here, we show that biodiversity of estuarine phytoplankton is related to flushing, and illustrate this for some European estuaries. The implications for the definition of re

  16. Phytoplankton diversity and primary production in Poonthura estuary, south Kerala

    OpenAIRE

    Ritakumari, S.D.; Shibu, S.

    2007-01-01

    Seasonal variations in the phytoplankton density, diversity, gross production and related physicochemical parameters of Poonthura estuary have been followed for a period of one year. The polluted nature of the water body favored a higher density of phytoplankters, which exhibited a positive correlation with gross production. The influence of various physicochemical parameters, phytoplankton density and species diversity on gross production is discussed.

  17. Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles

    DEFF Research Database (Denmark)

    Le Quéré, Corinne; Buitenhuis, Erik T.; Moriarty, Róisín;

    2016-01-01

    Global ocean biogeochemistry models currently employed in climate change projections use highly simplified representations of pelagic food webs. These food webs do not necessarily include critical pathways by which ecosystems interact with ocean biogeochemistry and climate. Here we present a global...... zooplankton community, despite iron limitation of phytoplankton community growth rates. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean....

  18. Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles

    Science.gov (United States)

    Le Quéré, Corinne; Buitenhuis, Erik T.; Moriarty, Róisín; Alvain, Séverine; Aumont, Olivier; Bopp, Laurent; Chollet, Sophie; Enright, Clare; Franklin, Daniel J.; Geider, Richard J.; Harrison, Sandy P.; Hirst, Andrew G.; Larsen, Stuart; Legendre, Louis; Platt, Trevor; Prentice, I. Colin; Rivkin, Richard B.; Sailley, Sévrine; Sathyendranath, Shubha; Stephens, Nick; Vogt, Meike; Vallina, Sergio M.

    2016-07-01

    Global ocean biogeochemistry models currently employed in climate change projections use highly simplified representations of pelagic food webs. These food webs do not necessarily include critical pathways by which ecosystems interact with ocean biogeochemistry and climate. Here we present a global biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types (PFTs): six types of phytoplankton, three types of zooplankton, and heterotrophic procaryotes. We improved the representation of zooplankton dynamics in our model through (a) the explicit inclusion of large, slow-growing macrozooplankton (e.g. krill), and (b) the introduction of trophic cascades among the three zooplankton types. We use the model to quantitatively assess the relative roles of iron vs. grazing in determining phytoplankton biomass in the Southern Ocean high-nutrient low-chlorophyll (HNLC) region during summer. When model simulations do not include macrozooplankton grazing explicitly, they systematically overestimate Southern Ocean chlorophyll biomass during the summer, even when there is no iron deposition from dust. When model simulations include a slow-growing macrozooplankton and trophic cascades among three zooplankton types, the high-chlorophyll summer bias in the Southern Ocean HNLC region largely disappears. Our model results suggest that the observed low phytoplankton biomass in the Southern Ocean during summer is primarily explained by the dynamics of the Southern Ocean zooplankton community, despite iron limitation of phytoplankton community growth rates. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean.

  19. Primary production in a tropical large lake: The role of phytoplankton composition

    Energy Technology Data Exchange (ETDEWEB)

    Darchambeau, F., E-mail: francois.darchambeau@ulg.ac.be [Chemical Oceanography Unit, University of Liège, Liège (Belgium); Sarmento, H., E-mail: hugo.sarmento@gmail.com [Department of Hydrobiology, Federal University of São Carlos, 13565-905 São Carlos, São Paulo (Brazil); Descy, J.-P., E-mail: jean-pierre.descy@unamur.be [Research Unit in Environmental and Evolutionary Biology, University of Namur, Namur (Belgium)

    2014-03-01

    Phytoplankton biomass and primary production in tropical large lakes vary at different time scales, from seasons to centuries. We provide a dataset made of 7 consecutive years of phytoplankton biomass and production in Lake Kivu (Eastern Africa). From 2002 to 2008, bi-weekly samplings were performed in a pelagic site in order to quantify phytoplankton composition and biomass, using marker pigments determined by HPLC. Primary production rates were estimated by 96 in situ {sup 14}C incubations. A principal component analysis showed that the main environmental gradient was linked to a seasonal variation of the phytoplankton assemblage, with a clear separation between diatoms during the dry season and cyanobacteria during the rainy season. A rather wide range of the maximum specific photosynthetic rate (P{sub Bm}) was found, ranging between 1.15 and 7.21 g carbon g{sup −1} chlorophyll a h{sup −1}, and was best predicted by a regression model using phytoplankton composition as an explanatory variable. The irradiance at the onset of light saturation (I{sub k}) ranged between 91 and 752 μE m{sup −2} s{sup −1} and was linearly correlated with the mean irradiance in the mixed layer. The inter-annual variability of phytoplankton biomass and production was high, ranging from 53 to 100 mg chlorophyll a m{sup −2} (annual mean) and from 143 to 278 g carbon m{sup −2} y{sup −1}, respectively. The degree of seasonal mixing determined annual production, demonstrating the sensitivity of tropical lakes to climate variability. A review of primary production of other African great lakes allows situating Lake Kivu productivity in the same range as that of lakes Tanganyika and Malawi, even if mean phytoplankton biomass was higher in Lake Kivu. - Highlights: • We provide a 7-year dataset of primary production in a tropical great lake. • Specific photosynthetic rate was determined by community composition. • Annual primary production varied between 143 and 278 mg C m

  20. Response of phytoplankton dynamics to 19-year (1991-2009) climate trends in Potter Cove (Antarctica)

    Science.gov (United States)

    Schloss, Irene R.; Abele, Doris; Moreau, Sébastien; Demers, Serge; Bers, A. Valeria; González, Oscar; Ferreyra, Gustavo A.

    2012-04-01

    King George Island (KGI, Isla 25 de Mayo) is located within one of the most rapidly warming regions on Earth at the north-western tip of the Antarctic Peninsula. Since 1991 hydrographical characteristics and phytoplankton dynamics were monitored at two stations in Potter Cove, a fjord-like environment on the south-eastern KGI coastline. Seawater temperature and salinity, total suspended particulate matter (TSPM) and chlorophyll- a (Chl- a, a proxy for phytoplankton biomass) concentrations were measured in summer and winter over a 19-year period, together with local air temperature. Mean air temperatures rose by 0.39 and 0.48 °C per decade in summer and winter, respectively. Positive anomalies characterized wind speeds during the decade between the mid '90 and the mid 2000 years, whereas negative anomalies were observed from 2004 onwards. Day of sea ice formation and retreat, based on satellite data, did not change, although total sea ice cover diminished during the studied period. Surface water temperature increased during summer (0.36 °C per decade), whereas no trend was observed in salinity. Summer Chl- a concentrations were around 1 mg m - 3 Chl- a with no clear trend throughout the study period. TSPM increased in surface waters of the inner cove during the spring-summer months. The Southern Annular Mode (SAM) climate signal was apparent in the fluctuating interannual pattern of the hydrographic variables in the outer Potter Cove and bottom waters whereas surface hydrography was strongly governed by the local forcing of glacier melt. The results show that global trends have significant effects on local hydrographical and biological conditions in the coastal marine environments of Western Antarctica.

  1. The SCAR Standing Committee on Antarctic Data Management - new directions in access to Antarctic research data

    Science.gov (United States)

    de Bruin, T.

    2009-04-01

    The SCAR Standing Committee on Antarctic Data Management (SC-ADM) was established by the Scientific Committee on Antarctic Research (SCAR) and the Council of Managers of National Antarctic Programs (COMNAP), to assist in the fulfillment of the data management obligations imposed by the Antarctic Treaty (section III.1.c): "Scientific observations and results from Antarctica shall be exchanged and made freely available." SC-ADM comprises representatives of the National Antarctic Data Centres or national points of contact. Currently 31 nations around the world are represented in SC-ADM. So far, SC-ADM has been focussing on the coordination of the Antarctic Master Directory (AMD), the internationally accessible, web-based, searchable record of Antarctic and Southern Ocean data set descriptions. The AMD is directly integrated into the international Global Change Master Directory (GCMD) to help further merge Antarctic science into global science. The AMD is a resource for scientists to advertise the data they have collected and to search for data they may need. Currently, SC-ADM is in a transition phase, moving forward to provide data access. Existing systems and web services technology will be used as much as possible, to increase efficiency and prevent 're-inventing the wheel' This poster will give an overview of this process, the current status and the expected results.

  2. Recruitment, growth and mortality of an Antarctic hexactinellid sponge, Anoxycalyx joubini.

    Directory of Open Access Journals (Sweden)

    Paul K Dayton

    Full Text Available Polar ecosystems are sensitive to climate forcing, and we often lack baselines to evaluate changes. Here we report a nearly 50-year study in which a sudden shift in the population dynamics of an ecologically important, structure-forming hexactinellid sponge, Anoxycalyx joubini was observed. This is the largest Antarctic sponge, with individuals growing over two meters tall. In order to investigate life history characteristics of Antarctic marine invertebrates, artificial substrata were deployed at a number of sites in the southern portion of the Ross Sea between 1967 and 1975. Over a 22-year period, no growth or settlement was recorded for A. joubini on these substrata; however, in 2004 and 2010, A. joubini was observed to have settled and grown to large sizes on some but not all artificial substrata. This single settlement and growth event correlates with a region-wide shift in phytoplankton productivity driven by the calving of a massive iceberg. We also report almost complete mortality of large sponges followed over 40 years. Given our warming global climate, similar system-wide changes are expected in the future.

  3. Recruitment, Growth and Mortality of an Antarctic Hexactinellid Sponge, Anoxycalyx joubini

    Science.gov (United States)

    Dayton, Paul K.; Kim, Stacy; Jarrell, Shannon C.; Oliver, John S.; Hammerstrom, Kamille; Fisher, Jennifer L.; O’Connor, Kevin; Barber, Julie S.; Robilliard, Gordon; Barry, James; Thurber, Andrew R.; Conlan, Kathy

    2013-01-01

    Polar ecosystems are sensitive to climate forcing, and we often lack baselines to evaluate changes. Here we report a nearly 50-year study in which a sudden shift in the population dynamics of an ecologically important, structure-forming hexactinellid sponge, Anoxycalyx joubini was observed. This is the largest Antarctic sponge, with individuals growing over two meters tall. In order to investigate life history characteristics of Antarctic marine invertebrates, artificial substrata were deployed at a number of sites in the southern portion of the Ross Sea between 1967 and 1975. Over a 22-year period, no growth or settlement was recorded for A. joubini on these substrata; however, in 2004 and 2010, A. joubini was observed to have settled and grown to large sizes on some but not all artificial substrata. This single settlement and growth event correlates with a region-wide shift in phytoplankton productivity driven by the calving of a massive iceberg. We also report almost complete mortality of large sponges followed over 40 years. Given our warming global climate, similar system-wide changes are expected in the future. PMID:23460822

  4. Cell cycle and cell signal transduction in marine phytoplankton

    Institute of Scientific and Technical Information of China (English)

    LIU Jingwen; JIAO Nianzhi; CAI Huinong

    2006-01-01

    As unicellular phytoplankton, the growth of a marine phytoplankton population results directly from the completion of a cell cycle, therefore, cell-environment communication is an important way which involves signal transduction pathways to regulate cell cycle progression and contribute to growth, metabolism and primary production and respond to their surrounding environment in marine phytoplankton. Cyclin-CDK and CaM/Ca2+ are essentially key regulators in control of cell cycle and signal transduction pathway, which has important values on both basic research and applied biotechnology. This paper reviews progress made in this research field, which involves the identification and characterization of cyclins and cell signal transduction system, cell cycle control mechanisms in marine phytoplankton cells, cell cycle proteins as a marker of a terminal event to estimate the growth rate of phytoplankton at the species level, cell cycle-dependent toxin production of toxic algae and cell cycle progression regulated by environmental factors.

  5. A REVIEW OF PHYTOPLANKTON ECOLOGY IN FRESHWATER LAKES OF INDIA

    Directory of Open Access Journals (Sweden)

    Manisha D. GIRIPUNJE

    2013-12-01

    Full Text Available This is a comprehensive review of phytoplankton ecology in freshwater lakes of India. A review study was undertaken for the better understanding of the phytoplankton distribution. In broad terms, authors discussed the relations of phytoplankton with factors like lake temperature, sunlight exposure period, sunlight penetration, water pH, wind, transparency, seasonal variations, water characteristics, nutrient enrichment and prey-predator relation in the lakes of India. From the results, authors noticed that each lake habitat is different from other lake habitat. Finally, authors concluded that phytoplankton ecology is an indicator for the evaluation of impacts of influencing factors. These factors provide a suitable management plan for lakes. Phytoplankton ecology provides a ground for monitoring and assessing the strategies of the fresh water lake management.

  6. Assessing strength and dynamics of the Oligocene Antarctic Circumpolar Current using organic-walled dinoflagellate cysts

    Science.gov (United States)

    Bijl, P.; Houben, A. J.; Sangiorgi, F.; Brinkhuis, H.

    2013-12-01

    The Oligocene Epoch (33.9-23 Ma) is the time interval in the Cenozoic that saw the establishment of a continental-scale Antarctic ice-sheet. Numerical modelling studies suggest that alongside continental ice, first sea-ice conditions may have started along the East Antarctic Margin, but this conclusion lacks support from field evidence. Other numerical models predict that hysteresis effects within the ice sheet will make a continental-size Antarctic ice sheet rather insensitive to warming. In contrast, deep-water benthic foraminiferal oxygen isotope records across the Oligocene suggest dramatic waxing and waning of Antarctic ice sheets. The role of opening of Southern Ocean Gateways on the process of building and sustaining Antarctic continental ice has been questioned in the past. Particularly uncertain is the timing of the installation of a strong Antarctic Circumpolar Current (ACC), and the dynamics of its strength in the earlier phases of Gateway throughflow. Integrated Ocean Drilling Expedition 318 drilled the Antarctic Margin in 2010, and recovered sediments from the early phase of Antarctic glaciation. With this record, we can now evaluate the robustness of the results of the numerical models and the oceanographic changes with field data. Sediments recovered from Site U1356 yields a thick and relatively complete (albeit compromised by core gaps) Oligocene succession both of which are chrono-stratigraphically well-calibrated with use of nannoplankton- dinocyst- and magnetostratigraphy. Notably, this record yields well-preserved dinoflagellate cysts (dinocysts). Dinocysts are the fossilizable remains of dinoflagellates, some of which are today specifically linked to the high (seasonal) productivity of the ecosystems associated with sea-ice and oceanic fronts. In the earliest Oligocene, just after the onset of Antarctic glaciation, we document the installation of dinoflagellate cyst assemblages that bear remarkable similarity with those of the present

  7. Toxicity of atmospheric aerosols on marine phytoplankton

    Science.gov (United States)

    Paytan, A.; Mackey, K.R.M.; Chen, Y.; Lima, I.D.; Doney, S.C.; Mahowald, N.; Labiosa, R.; Post, A.F.

    2009-01-01

    Atmospheric aerosol deposition is an important source of nutrients and trace metals to the open ocean that can enhance ocean productivity and carbon sequestration and thus influence atmospheric carbon dioxide concentrations and climate. Using aerosol samples from different back trajectories in incubation experiments with natural communities, we demonstrate that the response of phytoplankton growth to aerosol additions depends on specific components in aerosols and differs across phytoplankton species. Aerosol additions enhanced growth by releasing nitrogen and phosphorus, but not all aerosols stimulated growth. Toxic effects were observed with some aerosols, where the toxicity affected picoeukaryotes and Synechococcus but not Prochlorococcus.We suggest that the toxicity could be due to high copper concentrations in these aerosols and support this by laboratory copper toxicity tests preformed with Synechococcus cultures. However, it is possible that other elements present in the aerosols or unknown synergistic effects between these elements could have also contributed to the toxic effect. Anthropogenic emissions are increasing atmospheric copper deposition sharply, and based on coupled atmosphere-ocean calculations, we show that this deposition can potentially alter patterns of marine primary production and community structure in high aerosol, low chlorophyll areas, particularly in the Bay of Bengal and downwind of South and East Asia.

  8. Super-aggregations of krill and humpback whales in Wilhelmina Bay, Antarctic Peninsula.

    Directory of Open Access Journals (Sweden)

    Douglas P Nowacek

    Full Text Available Ecological relationships of krill and whales have not been explored in the Western Antarctic Peninsula (WAP, and have only rarely been studied elsewhere in the Southern Ocean. In the austral autumn we observed an extremely high density (5.1 whales per km(2 of humpback whales (Megaptera novaeangliae feeding on a super-aggregation of Antarctic krill (Euphausia superba in Wilhelmina Bay. The krill biomass was approximately 2 million tons, distributed over an area of 100 km(2 at densities of up to 2000 individuals m(-3; reports of such 'super-aggregations' of krill have been absent in the scientific literature for >20 years. Retentive circulation patterns in the Bay entrained phytoplankton and meso-zooplankton that were grazed by the krill. Tagged whales rested during daylight hours and fed intensively throughout the night as krill migrated toward the surface. We infer that the previously unstudied WAP embayments are important foraging areas for whales during autumn and, furthermore, that meso-scale variation in the distribution of whales and their prey are important features of this system. Recent decreases in the abundance of Antarctic krill around the WAP have been linked to reductions in sea ice, mediated by rapid climate change in this area. At the same time, baleen whale populations in the Southern Ocean, which feed primarily on krill, are recovering from past exploitation. Consideration of these features and the effects of climate change on krill dynamics are critical to managing both krill harvests and the recovery of baleen whales in the Southern Ocean.

  9. Free amino acids in Antarctic aerosol: potential markers for the evolution and fate of marine aerosol

    Directory of Open Access Journals (Sweden)

    E. Barbaro

    2015-01-01

    Full Text Available To investigate the impact of marine aerosols on global climate change it is important to study their chemical composition and size distribution. Amino acids are a component of the organic nitrogen in aerosols, particles containing amino acids have been found to be efficient ice nuclei. The main aim of this study was to investigate the L- and D-free amino acid composition as possible tracers of primary biological production in Antarctic aerosols from three different areas: two continental bases, Mario Zucchelli Station (MZS on the coast of the Ross Sea, Concordia Station at Dome C on the Antarctic Plateau, and the Southern Ocean near the Antarctic continent. Studying the size distribution of amino acids in aerosols allowed us to characterize this component of the water-soluble organic carbon (WSOC in marine aerosols near their source and after long-range transport. The presence of only free L-amino acids in our samples is indicative of the prevalence of phytoplanktonic material. Sampling at these three points allowed us to study the reactivity of these compounds during long-range transport. The mean total amino acid concentration detected at MZS was 11 pmol m−3, a higher percentage of amino acids were found in the fine fraction. The aerosol samples collected at Dome C had the lowest amino acid values (0.7 and 0.8 pmol m−3 and the coarse particles were found to be enriched with amino acids compared to the coastal site. The amino acid composition had also changed suggesting that physical and chemical transformations had occurred during long range transport. During the sampling cruise on the R/V talica on the Southern Ocean, high concentrations of amino acids were found in the total suspended particles, this we attribute to the presence of intact biological material in the sample.

  10. Marine Ecosystem Response to Rapid Climate Warming on the West Antarctic Peninsula (Invited)

    Science.gov (United States)

    Ducklow, H.; Baker, K. S.; Doney, S. C.; Fraser, B.; Martinson, D. G.; Meredith, M. P.; Montes-Hugo, M. A.; Sailley, S.; Schofield, O.; Sherrell, R. M.; Stammerjohn, S. E.; Steinberg, D. K.

    2010-12-01

    The Palmer, Antarctica LTER builds on meteorological, ocean color and seabird observations since the late 1970s. It occupies annually in summer a regional-scale grid extending 700 km northward from Charcot Island to Anvers Island, and 200 km cross-shelf from the coast to the shelfbreak. In addition to routine CTD profiles and zooplankton tows throughout the grid, the observing system also includes Slocum Glider surveys and thermistor moorings. Geophysical changes include +6C atmospheric warming in winter since 1950, a 20% increase in heat content over the continental shelf since 1990, a surface ocean warming of +1C since 1950, an 83-day reduction in sea ice duration (advance 48 days later, retreat 35 days earlier) over the greater southern Bellingshausen Sea region from 1979-2007, intensification of westerly winds and differential changes in cloudiness. In response to these large changes in the regional climate, the marine ecosystem of the western Peninsula is changing at all trophic levels from diatoms to penguins. Ocean color indicates differential changes in phytoplankton stocks in response to regional decreases in sea ice cover. Surface chlorophyll has declined 89% in the north and increased 67% in the south. Antarctic krill and salps have declined and increased in our study area, respectively. Penguin diet sampling suggests changes in populations or distributions of the Antarctic Silverfish in the Anvers Island vicinity, possibly in response to ocean warming. Adélie penguins have declined 75% from 15000 to food availability and increased late spring snow accumulation. Changes in pygoscelid penguin breeding populations in the Anvers Island vicinity of the West Antarctic Peninsula

  11. Characterising Antarctic and Southern Ocean Lithosphere with Magnetic and Gravity Imaging of East Antarctic Rift Systems

    Science.gov (United States)

    Vaughan, A. P.; Kusznir, N. J.; Ferraccioli, F.; Jordan, T. A.; Purucker, M. E.; Golynsky, A. V.; Rogozhina, I.

    2012-12-01

    East Antarctica will identify the plate-scale geometry of zones of crustal and lithospheric thinning; 4) understanding when and how East Antarctica acquired its thick crust and high elevation, and why it is so thick and elevated, will place new constraints on models of Cenozoic ice sheet formation and stability. The crustal thickness map for East Antarctica will make it possible to produce a multi-dataset-based geothermal heatflux map for the continent. Estimating the heat flux in the Gamburtsev Subglacial Mountains (GSM) region is particularly critical because: 1) The GSM likely acted as key nucleation point for the East Antarctic Ice Sheet (EAIS); 2) the region may contain the oldest ice of the EAIS - a prime target for future ice core drilling; 3) geothermal heat flux is important to understand proposed ice accretion at the base of the EAIS in the GSM and its links to sub-ice hydrology; 4) an integrated multi-dataset-based geothermal heatflux model for East Antarctica will resolve the wide range of estimates previously published using single datasets.

  12. Phytoplankton and the Macondo oil spill: A comparison of the 2010 phytoplankton assemblage to baseline conditions on the Louisiana shelf.

    Science.gov (United States)

    Parsons, M L; Morrison, W; Rabalais, N N; Turner, R E; Tyre, K N

    2015-12-01

    The Macondo oil spill was likely the largest oil spill to ever occur in United States territorial waters. We report herein our findings comparing the available baseline phytoplankton data from coastal waters west of the Mississippi River, and samples collected monthly from the same sampling stations, during and after the oil spill (May-October, 2010). Our results indicate that overall, the phytoplankton abundance was 85% lower in 2010 versus the baseline, and that the species composition of the phytoplankton community moved towards diatoms and cyanobacteria and away from ciliates and phytoflagellates. The results of this study reaffirm the view that phytoplankton responses will vary by the seasonal timing of the oil spill and the specific composition of the spilled oil. The trophic impacts of the purported lower abundance of phytoplankton in 2010 coupled with the observed assemblage shift remain unknown. PMID:26378966

  13. Latest tendency in the Antarctic ozone longitudinal distribution

    Science.gov (United States)

    Milinevsky, Gennadi; Grytsai, Asen; Klekociuk, Andrew; Evtushevsky, Olexander

    2014-05-01

    Significant ozone depletion was observed within the southern polar vortex during spring in the 1980s - early 1990s. Later, a stabilization in total ozone levels and ozone hole area has been observed. Atmosphere models predict a consequent recovery of the Antarctic ozone. Nevertheless, identification of the long-term processes is complicated by high interannual variability hiding their general regularities. In particular, a large stratosphere warming in 2002 resulted in significant increase in total ozone levels. The Antarctic ozone hole is formed inside polar stratospheric vortex, which is under influence of large-scale planetary waves. The components of the quasi-stationary wave (QSW) in the spring Southern Hemisphere (SH) stratosphere is mainly contributed by zonal wave number 1 which in turn determines the location of the total ozone extremes in spring: QSW minimum (maximum) is located in the South Atlantic (Australian) sector. In our work the satellite data of TOMS/Nimbus-7, TOMS/Earth Probe and OMI/Aura (http://ozoneaq.gsfc.nasa.gov/) have been used to investigate longitudinal distribution of the total ozone in Antarctic region. The gap in these satellite observations (1993-1995) was filled by the Multi-Sensor Reanalysis data (http://www.temis.nl/). Ozone distribution in the SH high and mid latitudes 80-50S were analyzed for southern spring season including months from September to November. The zonal distribution is considered along seven latitude circles from 80S to 50S with step of five degrees. To distinguish long-term processes and to obtain a quasi-stationary pattern, daily September - November ozone was averaged. Our previous study demonstrated a systematic eastward shift of the QSW minimum region. In this study, we extended the analysis to 2013 and obtained new results that exhibited a probable cessation in that eastward shift. Polynomial fit for all chosen latitudes is even evidence of a change in the tendency to opposite. It more time needs to

  14. Further analysis of target strength measurements of Antarctic krill at 38 and 120 kHz: Comparison with deformed cylinder model and inference of orientation distribution

    OpenAIRE

    Chu, Dezhang; Foote, Kenneth G.; Stanton, Timothy K.

    1993-01-01

    Data collected during the krill target strength experiment [J. Acoust. Soc. Am. 87, 16–24 (1990)] are examined in the light of a recent zooplankton scattering model where the elongated animals are modeled as deformed finite cylinders [J. Acoust. Soc. Am. 86, 691–705 (1989)]. Exercise of the model under assumption of an orientation distribution allows absolute predictions of target strength to be made at each frequency. By requiring that the difference between predicted and measured target str...

  15. Health aspects of Antarctic tourism.

    Science.gov (United States)

    Prociv, P

    1998-12-01

    Increasing numbers of seaborne tourists are visiting Antarctica, with most coming from the United States (3503 in 1996-97), Germany (777), and Australia (680; cf. 356 in 1994-95 and 410 in 1995-96). The impression among travel medicine clinicians is that, each year, more prospective travelers seek advice about the health demands of this type of adventure, mostly relating to fitness for travel, exposure to extreme cold, hazards in ice and snow, and other potential health risks. This is a recent phenomenon. While a regular shipping service had been established between the Falklands and the subantarctic islands of South Georgia and the South Shetlands by 1924, the first documented tourists accompanied an Argentine expedition to the South Orkneys in 1933.1 Commercial airline flights over these islands and the Antarctic Peninsula began in 1956, from Chile, and recreational cruises to the Peninsula began in 1958. Tourist numbers subsequently grew slowly, for what was clearly an exclusive and very expensive undertaking, with few ships available for these hazardous voyages. From 1957 to 1993, 37,000 tourists visited by sea, most seeing only the Peninsula.2 The dramatic recent growth in numbers is a consequence of the collapse of the Soviet Union. The small fleet of ice-strengthened research vessels and working icebreakers, which was made redundant by withdrawal of central government support from isolated communities and military activities along the northern coast of Siberia (and from Antarctic research bases), now accounts for the bulk of charter-cruise tourism to Antarctica, at competitive prices. According to the International Association of Antarctica Tour Operators,3 7322 people traveled to Antarctica on commercially organized voyages in the 1996-97 season, and a record 10,000 shipborne visitors were expected for the 1997-98 season (November-March), traveling mainly from South America to the Peninsula on 15 ice-reinforced vessels, each carrying between 36 and 180

  16. Iodine monoxide in the Antarctic snowpack

    Directory of Open Access Journals (Sweden)

    U. Platt

    2009-11-01

    Full Text Available Recent ground-based and space borne observations suggest the presence of significant amounts of iodine monoxide in the boundary layer of Antarctica, which are expected to have an impact on the ozone budget and might contribute to the formation of new airborne particles. So far, the source of these iodine radicals has been unknown. This paper presents long-term measurements of iodine monoxide at the German Antarctic research station Neumayer, which indicate that the snowpack is the main source for iodine radicals. The measurements have been performed using multi-axis differential optical absorption spectroscopy (MAX-DOAS. Using a coupled atmosphere-snowpack radiative transfer model, the comparison of the signals observed from scattered skylight and from light reflected by the snowpack yields several ppb of iodine monoxide in the upper layers of the sunlit snowpack throughout the year. Snow pit samples from Neumayer Station contain up to 700 ng/l of total iodine, representing a sufficient reservoir for these extraordinarily high IO concentrations.

  17. Iodine monoxide in the Antarctic snowpack

    Directory of Open Access Journals (Sweden)

    U. Frieß

    2010-03-01

    Full Text Available Recent ground-based and space borne observations suggest the presence of significant amounts of iodine monoxide in the boundary layer of Antarctica, which are expected to have an impact on the ozone budget and might contribute to the formation of new airborne particles. So far, the source of these iodine radicals has been unknown. This paper presents long-term measurements of iodine monoxide at the German Antarctic research station Neumayer, which indicate that high IO concentrations in the order of 50 ppb are present in the snow interstitial air. The measurements have been performed using multi-axis differential optical absorption spectroscopy (MAX-DOAS. Using a coupled atmosphere – snowpack radiative transfer model, the comparison of the signals observed from scattered skylight and from light reflected by the snowpack yields several ppb of iodine monoxide in the upper layers of the sunlit snowpack throughout the year. Snow pit samples from Neumayer Station contain up to 700 ng/l of total iodine, representing a sufficient reservoir for these extraordinarily high IO concentrations.

  18. Towards the fourth GEWEX atmospheric boundary layer model intercomparison study (GABLS4): exploration of very stable conditions over an Antarctic ice shelf

    NARCIS (Netherlands)

    Vihma, T.; Kilpeläinen, T.; Rontu, L.; Anderson, P.S.; Orr, A.; Phillips, T.; Finkele, K.; Rodrigo, I.; Holtslag, A.A.M.; Svensson, G.

    2012-01-01

    Numerical weather prediction and climate models continue to have large errors for stable boundary layers (SBL). To understand and to improve on this, so far three atmospheric boundary layer model inter-comparison studies have been organised within the Global Energy and Water Cycle Experiment (GEWEX)

  19. Carbon-based phytoplankton size classes retrieved via ocean color estimates of the particle size distribution

    Science.gov (United States)

    Kostadinov, Tihomir S.; Milutinović, Svetlana; Marinov, Irina; Cabré, Anna

    2016-04-01

    Owing to their important roles in biogeochemical cycles, phytoplankton functional types (PFTs) have been the aim of an increasing number of ocean color algorithms. Yet, none of the existing methods are based on phytoplankton carbon (C) biomass, which is a fundamental biogeochemical and ecological variable and the "unit of accounting" in Earth system models. We present a novel bio-optical algorithm to retrieve size-partitioned phytoplankton carbon from ocean color satellite data. The algorithm is based on existing methods to estimate particle volume from a power-law particle size distribution (PSD). Volume is converted to carbon concentrations using a compilation of allometric relationships. We quantify absolute and fractional biomass in three PFTs based on size - picophytoplankton (0.5-2 µm in diameter), nanophytoplankton (2-20 µm) and microphytoplankton (20-50 µm). The mean spatial distributions of total phytoplankton C biomass and individual PFTs, derived from global text">SeaWiFS monthly ocean color data, are consistent with current understanding of oceanic ecosystems, i.e., oligotrophic regions are characterized by low biomass and dominance of picoplankton, whereas eutrophic regions have high biomass to which nanoplankton and microplankton contribute relatively larger fractions. Global climatological, spatially integrated phytoplankton carbon biomass standing stock estimates using our PSD-based approach yield ˜ 0.25 Gt of C, consistent with analogous estimates from two other ocean color algorithms and several state-of-the-art Earth system models. Satisfactory in situ closure observed between PSD and POC measurements lends support to the theoretical basis of the PSD-based algorithm. Uncertainty budget analyses indicate that absolute carbon concentration uncertainties are driven by the PSD parameter No which determines particle number concentration to first order, while uncertainties in PFTs' fractional contributions to total C biomass are mostly due to the

  20. Carbon-based phytoplankton size classes retrieved via ocean color estimates of the particle size distribution

    Directory of Open Access Journals (Sweden)

    T. S. Kostadinov

    2015-05-01

    Full Text Available Owing to their important roles in biogeochemical cycles, phytoplankton functional types (PFTs have been the aim of an increasing number of ocean color algorithms. Yet, none of the existing methods are based on phytoplankton carbon (C biomass, which is a fundamental biogeochemical and ecological variable and the "unit of accounting" in Earth System models. We present a novel bio-optical algorithm to retrieve size-partitioned phytoplankton carbon from ocean color satellite data. The algorithm is based on existing algorithms to estimate particle volume from a power-law particle size distribution (PSD. Volume is converted to carbon concentrations using a compilation of allometric relationships. We quantify absolute and fractional biomass in three PFTs based on size – picophytoplankton (0.5–2 μm in diameter, nanophytoplankton (2–20 μm and microphytoplankton (20–50 μm. The mean spatial distributions of total phytoplankton C biomass and individual PFTs, derived from global SeaWiFS monthly ocean color data, are consistent with current understanding of oceanic ecosystems, i.e. oligotrophic regions are characterized by low biomass and dominance of picoplankton, whereas eutrophic regions have large biomass to which nanoplankton and microplankton contribute relatively larger fractions. Global spatially integrated phytoplankton carbon biomass standing stock estimates using our PSD-based approach yield on average ~0.2–0.3 Gt of C, consistent with analogous estimates from two other ocean color algorithms, and several state-of-the-art Earth System models. However, the range of phytoplankton C biomass spatial variability globally is larger than estimated by any other models considered here, because the PSD-based algorithm is not a priori empirically constrained and introduces improvement over the assumptions of the other approaches. Satisfactory in situ closure observed between PSD and POC measurements lends support to the theoretical basis of the

  1. Carbon-based phytoplankton size classes retrieved via ocean color estimates of the particle size distribution

    Science.gov (United States)

    Kostadinov, Tihomir S.; Milutinović, Svetlana; Marinov, Irina; Cabré, Anna

    2016-04-01

    Owing to their important roles in biogeochemical cycles, phytoplankton functional types (PFTs) have been the aim of an increasing number of ocean color algorithms. Yet, none of the existing methods are based on phytoplankton carbon (C) biomass, which is a fundamental biogeochemical and ecological variable and the "unit of accounting" in Earth system models. We present a novel bio-optical algorithm to retrieve size-partitioned phytoplankton carbon from ocean color satellite data. The algorithm is based on existing methods to estimate particle volume from a power-law particle size distribution (PSD). Volume is converted to carbon concentrations using a compilation of allometric relationships. We quantify absolute and fractional biomass in three PFTs based on size - picophytoplankton (0.5-2 µm in diameter), nanophytoplankton (2-20 µm) and microphytoplankton (20-50 µm). The mean spatial distributions of total phytoplankton C biomass and individual PFTs, derived from global SeaWiFS monthly ocean color data, are consistent with current understanding of oceanic ecosystems, i.e., oligotrophic regions are characterized by low biomass and dominance of picoplankton, whereas eutrophic regions have high biomass to which nanoplankton and microplankton contribute relatively larger fractions. Global climatological, spatially integrated phytoplankton carbon biomass standing stock estimates using our PSD-based approach yield ˜ 0.25 Gt of C, consistent with analogous estimates from two other ocean color algorithms and several state-of-the-art Earth system models. Satisfactory in situ closure observed between PSD and POC measurements lends support to the theoretical basis of the PSD-based algorithm. Uncertainty budget analyses indicate that absolute carbon concentration uncertainties are driven by the PSD parameter No which determines particle number concentration to first order, while uncertainties in PFTs' fractional contributions to total C biomass are mostly due to the

  2. The role of phytoplankton in the modulation of dissolved and oyster cadmium concentrations in Deep Bay, British Columbia, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Cassis, David, E-mail: dcassis@telus.net [Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 (Canada); Lekhi, Priyanka [Department of Chemistry, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 (Canada); Pearce, Christopher M. [Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, BC, Canada V9T 6N7 (Canada); Ebell, Nadene [Ministry of Agriculture, Nanaimo, BC, Canada V9T 6J9 (Canada); Orians, Kristin [Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 (Canada); Department of Chemistry, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 (Canada); Maldonado, Maria T. [Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 (Canada)

    2011-09-15

    We previously identified dissolved cadmium (Cd{sub diss}) as the main source of this metal in cultured Pacific oysters, Crassostrea gigas, in Deep Bay, British Columbia, Canada (Lekhi et al., 2008). Total suspended particulate Cd (Cd{sub part}) was not found to be a significant source of oyster Cd (Cd{sub oys}), with Cd{sub part} > 20 {mu}m negatively correlated with Cd{sub oys} concentration. High phytoplankton abundance in spring and summer was hypothesized to reduce Cd{sub oys} indirectly by drawing down Cd{sub diss} and increasing oyster growth. In the present study we expanded on these results by examining specifically how the phytoplankton community composition modulates both Cd{sub diss} and Cd{sub oys} concentrations in Deep Bay. Based on calculations of nutrients and Cd{sub diss} drawdown, phytoplankton accounted for approximately 90% of the overall summer reduction in Cd{sub diss} in the bay. Diatoms were the dominant phytoplankton group, being correlated negatively with Cd{sub oys} and positively with Cd{sub part}. This suggests that diatom growth mediates the transfer of Cd from the dissolved to the particulate phase, resulting in lower Cd{sub oys}. Spring blooms and sporadic harmful algal blooms may mediate a large flux of Cd{sub part} to the sediments. Thus, phytoplankton act as a sink, rather than a source, of Cd to oysters in Deep Bay and have a crucial role in the seasonality of Cd{sub oys} by reducing the concentration of Cd{sub diss} during the summer. Based on environmental variables, two descriptive models for annual Cd{sub oys} concentrations were developed using multiple linear regression. The first model (R{sup 2} = 0.870) was created to explain the maximum variability in Cd{sub oys} concentrations throughout the year, while the second (R{sup 2} = 0.806) was based on parameters that could be measured easily under farm conditions. Oyster age heavily affected both models, with the first model being secondarily affected by temperature and the

  3. Arctic and Antarctic Ice Pack Changes during the Past Decade from a High Resolution Global Coupled Sea Ice-Ocean Model

    Science.gov (United States)

    Ivanova, D. P.; McClean, J. L.; Thoppil, P.; Hunke, E.; Stark, D.; Maltrud, M. E.; Lipscomb, W.

    2004-12-01

    Changes over the past decade in the global ice pack are analyzed using a coupled ice-ocean model and observational data sets. The model consists of the latest versions of the Los Alamos Parallel Ocean Program (POP) and sea ice model (CICE) and is configured on a moderately high-resolution global grid (0.4° and 40 vertical levels). A model simulation forced with high frequency daily NCEP/NCAR atmospheric fields was integrated for 23 years (1979-2002). Following a decade-long ice spin-up, the model's ability to reproduce observed ice extent, ice thickness and ice drift distributions is evaluated by statistical comparisons using satellite, upward looking sonar and ice drift buoy data. In particular, the realism of the ice mean state and variability on time scales from daily to interannual are examined. To better understand ocean-ice interaction processes, coupled model results are compared to stand alone integrations of the ice and ocean models. Mean ice states are examined during the positive/negative phases of the North Atlantic Oscillation and Arctic Oscillation in the last decade of the coupled simulation. Particularly ice export from the Fram and Bering Straits during these phases will be considered.

  4. Flexible C : N ratio enhances metabolism of large phytoplankton when resource supply is intermittent

    Science.gov (United States)

    Talmy, D.; Blackford, J.; Hardman-Mountford, N. J.; Polimene, L.; Follows, M. J.; Geider, R. J.

    2014-09-01

    Phytoplankton cell size influences particle sinking rate, food web interactions and biogeographical distributions. We present a model in which the uptake, storage and assimilation of nitrogen and carbon are explicitly resolved in different-sized phytoplankton cells. In the model, metabolism and cellular C : N ratio are influenced by the accumulation of carbon polymers such as carbohydrate and lipid, which is greatest when cells are nutrient starved, or exposed to high light. Allometric relations and empirical data sets are used to constrain the range of possible C : N, and indicate that larger cells can accumulate significantly more carbon storage compounds than smaller cells. When forced with extended periods of darkness combined with brief exposure to saturating irradiance, the model predicts organisms large enough to accumulate significant carbon reserves may on average synthesize protein and other functional apparatus up to five times faster than smaller organisms. The advantage of storage in terms of average daily protein synthesis rate is greatest when modeled organisms were previously nutrient starved, and carbon storage reservoirs saturated. Small organisms may therefore be at a disadvantage in terms of average daily growth rate in environments that involve prolonged periods of darkness and intermittent nutrient limitation. We suggest this mechanism is a significant constraint on phytoplankton C : N variability and cell size distribution in different oceanic regimes.

  5. DIVERSITY OF PLANKTON IN BIRNAL RESERVIOR WITH SPECIAL REFERENCE TO PHYTOPLANKTON

    OpenAIRE

    Deshmukh. S. B; Gonjare. G. R

    2014-01-01

    Phytoplankton's are microscopic autotrophs forming communities and Remain suspended in water up to the effective light penetration. Planktons are found in fresh; Marine and brackish water.Planktons are divided in phytoplankton and zooplankton. Phytoplankton constitute the basic food sourceof any aquatic ecosystem; which supports Aquatic animals such as fish's .The zooplanktons are the major mode of energy between Phytoplankton and fish.

  6. Phytoplankton chytridiomycosis: fungal parasites of phytoplankton and their imprints on the food web dynamics

    Directory of Open Access Journals (Sweden)

    Télesphore eSIME - NGANDO

    2012-10-01

    Full Text Available Parasitism is one of the earlier and common ecological interactions in the nature, occurring in almost all environments. Microbial parasites typically are characterized by their small size, short generation time, and high rates of reproduction, with simple life cycle occurring generally within a single host. They are diverse and ubiquitous in aquatic ecosystems, comprising viruses, prokaryotes and eukaryotes. Recently, environmental 18S-rDNA surveys of microbial eukaryotes have unveiled major infecting agents in pelagic systems, consisting primarily of the fungal order of Chytridiales (chytrids. Chytrids are considered the earlier branch of the Eumycetes and produce motile, flagellated zoospores, characterized by a small size (2-6 µm and a single, posterior flagellum. The existence of these dispersal propagules includes chytrids within the so-called group of zoosporic fungi, which are particularly adapted to the plankton lifestyle where they infect a wide variety of hosts, including fishes, eggs, zooplankton, algae, and other aquatic fungi but primarily freshwater phytoplankton. Related ecological implications are huge because chytrids can killed their hosts, release substrates for microbial processes, and provide nutrient-rich particles as zoospores and short fragments of filamentous inedible hosts for the grazer food chain. Furthermore, based on the observation that phytoplankton chytridiomycosis preferentially impacts the larger size species, blooms of such species (e.g. filamentous cyanobacteria may not totally represent trophic bottlenecks. Besides, chytrid epidemics represent an important driving factor in phytoplankton seasonal successions. In this review, I summarize the knowledge on the diversity, community structure, quantitative importance, and functional roles of fungal chytrids, primarily those who are parasites of phytoplankton, and infer the ecological implications and potentials for the food web dynamics and properties.

  7. 76 FR 9849 - Comprehensive Environmental Evaluations for Antarctic Activities

    Science.gov (United States)

    2011-02-22

    .... SUPPLEMENTARY INFORMATION: Article 3 of Annex I to the Protocol on Environmental Protection to the Antarctic Treaty requires the preparation of a CEE for any proposed Antarctic activity likely to have more than a... Comprehensive Environmental Evaluations for Antarctic Activities SUMMARY: The Department of State gives...

  8. Phytoplankton niches, traits and eco-evolutionary responses to global environmental change

    DEFF Research Database (Denmark)

    Litchman, Elena; Edwards, Kyle F.; Klausmeier, Christopher A.;

    2012-01-01

    Phytoplankton are major primary producers in aquatic ecosystems and are sensitive to various aspects of global environmental change. They can respond through phenotypic plasticity, species sorting, genetic adaptation, or a combination of these processes. Here we present conceptual, experimental a...... be investigated simultaneously. Novel models of trait evolution in a community context should provide additional insights into potential adaptation trajectories under diverse global change scenarios...

  9. Numerical analysis of cumulative impact of phytoplankton photoresponses to light variation on carbon assimilation

    OpenAIRE

    Esposito, S.; Botte, V.; Iudicone, D.; Ribera d'Alcala, M.

    2009-01-01

    Abstract Light variation in temporal and spatial domains is a key constraint on the photosynthetic performance of phytoplankton. The most obvious responses are the modification of cell pigment content either to improve photocapture or to mitigate photo-damage. Very few studies have analyzed whether light variation significantly alters carbon assimilation, especially in a fluctuating light environment as in the mixed layer of the ocean. We addressed the question using a modeling app...

  10. PHYTOPLANKTON OF VRANSKO LAKE ON THE ISLAND CRES

    Directory of Open Access Journals (Sweden)

    Marija Tomec

    1996-06-01

    Full Text Available As a special nature phenomenon, Vransko Lake with its ackreage of 5.7 km2 and cubic capacity of 220 million m3 fresh-water of extraordinary quality has been unsufficiently biologically examined. Ichthyological, physical, chemical and bacteriological examination were conducted in 1989 (June, September and December and 1990 (April, Special attention was given to the examination of phytoplankton structure as an indicator of water quality. In addition to collecting phytoplankton specimen, the temperature and transparency of water were measured at 5 different places (Picture 1. The phytoplankton specimen Were taken at the depths of 0.5 m, 10 m, 20 m and 40 m. The results of medium values of measured water temperature and lake transparency are showed on the Picture 2. The water temperature s was mostly under the influence of surrounding air temperature. The thermic stratification in summer and the manifestation of isotherm in the colder period of year were observed. In the qualitative composition of phytoplankton there were stated sixty plankton algae which belonged to the following system groups: Cyanophyceae, Euglenophyceae, Dinophyceae, Chryslophyceae and Chlorophyceae (Table 1. While representatives of Bacillariophyceae outnumbered other groups, the species Cera- tium hirundinella which belongs to the Dinophyceae group and the indicator of olighosaprobnog degree dominated in all phytoplankton specimen of Vransko Lake. Besides that group, the significant role in the phytoplankton structure had the species Cyclotella comta, the indicator of olighosaprobnog degree and Dinobryon divergens, the indicator of bethamesosaprobnog degree. On the basis of qualitative analysis of phytoplankton, the representatives of olighosaprobnog degree dominated in Vransko Lake what implies good water quality and the quantitative analysis show the olighothrophic lake character. According to representation of particular phytoplankton species at the time of examination, the

  11. Growth-irradiance relationships in phytoplankton

    Energy Technology Data Exchange (ETDEWEB)

    Falkowski, P.G.; Dubinsky, Z.; Wyman, K.

    1985-03-01

    The steady state growth rates of three species of marine phytoplankton, Thalassiosira weisflogii, Isochrysis galbana, and Prorocentrum micans, were followed in turbidostat culture. At each growth irradiance, photosynthesis and respiration were measured by following changes in oxygen. Together with measurements of optical absorption cross sections, cellular chlorophyll, carbon and nitrogen, and excretion rates as well as knowledge of the quantum flux, the quantum requirement for growth and photosynthesis were calculated. Our results suggest that variations in growth rate caused by changes in irradiance may be related to changes in respiration rates relative to growth as well as changes in optical absorption cross sections for a given species. Interspecific differences in growth rate at a given irradiance are not related to changes in respiration however, but are primarily attributable to differences in optical absorption cross sections normalized to chlorophyll and differences in chlorophyll:carbon ratios.

  12. Antarctic last interglacial isotope peak in response to sea ice retreat not ice-sheet collapse.

    Science.gov (United States)

    Holloway, Max D; Sime, Louise C; Singarayer, Joy S; Tindall, Julia C; Bunch, Pete; Valdes, Paul J

    2016-01-01

    Several studies have suggested that sea-level rise during the last interglacial implies retreat of the West Antarctic Ice Sheet (WAIS). The prevalent hypothesis is that the retreat coincided with the peak Antarctic temperature and stable water isotope values from 128,000 years ago (128 ka); very early in the last interglacial. Here, by analysing climate model simulations of last interglacial WAIS loss featuring water isotopes, we show instead that the isotopic response to WAIS loss is in opposition to the isotopic evidence at 128 ka. Instead, a reduction in winter sea ice area of 65±7% fully explains the 128 ka ice core evidence. Our finding of a marked retreat of the sea ice at 128 ka demonstrates the sensitivity of Antarctic sea ice extent to climate warming. PMID:27526639

  13. The effect of representing bromine from VSLS on the simulation and evolution of Antarctic ozone

    Science.gov (United States)

    Oman, Luke D.; Douglass, Anne R.; Salawitch, Ross J.; Canty, Timothy P.; Ziemke, Jerald R.; Manyin, Michael

    2016-09-01

    We use the Goddard Earth Observing System Chemistry-Climate Model, a contributor to both the 2010 and 2014 World Meteorological Organization Ozone Assessment Reports, to show that inclusion of 5 parts per trillion (ppt) of stratospheric bromine (Bry) from very short lived substances (VSLS) is responsible for about a decade delay in ozone hole recovery. These results partially explain the significantly later recovery of Antarctic ozone noted in the 2014 report, as bromine from VSLS was not included in the 2010 Assessment. We show multiple lines of evidence that simulations that account for VSLS Bry are in better agreement with both total column BrO and the seasonal evolution of Antarctic ozone reported by the Ozone Monitoring Instrument on NASA's Aura satellite. In addition, the near-zero ozone levels observed in the deep Antarctic lower stratospheric polar vortex are only reproduced in a simulation that includes this Bry source from VSLS.

  14. Antarctic last interglacial isotope peak in response to sea ice retreat not ice-sheet collapse.

    Science.gov (United States)

    Holloway, Max D; Sime, Louise C; Singarayer, Joy S; Tindall, Julia C; Bunch, Pete; Valdes, Paul J

    2016-01-01

    Several studies have suggested that sea-level rise during the last interglacial implies retreat of the West Antarctic Ice Sheet (WAIS). The prevalent hypothesis is that the retreat coincided with the peak Antarctic temperature and stable water isotope values from 128,000 years ago (128 ka); very early in the last interglacial. Here, by analysing climate model simulations of last interglacial WAIS loss featuring water isotopes, we show instead that the isotopic response to WAIS loss is in opposition to the isotopic evidence at 128 ka. Instead, a reduction in winter sea ice area of 65±7% fully explains the 128 ka ice core evidence. Our finding of a marked retreat of the sea ice at 128 ka demonstrates the sensitivity of Antarctic sea ice extent to climate warming.

  15. Combustion of available fossil-fuel resources sufficient to eliminate the Antarctic Ice Sheet

    Science.gov (United States)

    Winkelmann, R.; Levermann, A.; Ridgwell, A.; Caldeira, K.

    2015-12-01

    The Antarctic Ice Sheet stores water equivalent to 58 meters in global sea-level rise. Here we show in simulations with the Parallel Ice Sheet Model that burning the currently attainable fossil-fuel resources is sufficient to eliminate the ice sheet. With cumulative fossil-fuel emissions of 10 000 GtC, Antarctica is projected to become almost ice-free with an average contribution to sea-level rise exceeding 3 meters per century during the first millennium. Consistent with recent observations and simulations, the West Antarctic Ice Sheet becomes unstable with 600 to 800 GtC of additional carbon emissions. Beyond this additional carbon release, the destabilization of ice basins in both West- and East Antarctica results in a threshold-increase in global sea level. Unabated carbon emissions thus threaten the Antarctic Ice Sheet in its entirety with associated sea-level rise that far exceeds that of all other possible sources.

  16. Antarctic last interglacial isotope peak in response to sea ice retreat not ice-sheet collapse

    Science.gov (United States)

    Holloway, Max D.; Sime, Louise C.; Singarayer, Joy S.; Tindall, Julia C.; Bunch, Pete; Valdes, Paul J.

    2016-01-01

    Several studies have suggested that sea-level rise during the last interglacial implies retreat of the West Antarctic Ice Sheet (WAIS). The prevalent hypothesis is that the retreat coincided with the peak Antarctic temperature and stable water isotope values from 128,000 years ago (128 ka); very early in the last interglacial. Here, by analysing climate model simulations of last interglacial WAIS loss featuring water isotopes, we show instead that the isotopic response to WAIS loss is in opposition to the isotopic evidence at 128 ka. Instead, a reduction in winter sea ice area of 65±7% fully explains the 128 ka ice core evidence. Our finding of a marked retreat of the sea ice at 128 ka demonstrates the sensitivity of Antarctic sea ice extent to climate warming. PMID:27526639

  17. Contrasting phytoplankton community structure and associated light absorption characteristics of the western Bay of Bengal

    Science.gov (United States)

    Pandi, Sudarsana Rao; Kiran, Rayaprolu; Sarma, Nittala S.; Srikanth, A. S.; Sarma, V. V. S. S.; Krishna, M. S.; Bandyopadhyay, D.; Prasad, V. R.; Acharyya, T.; Reddy, K. G.

    2014-01-01

    Absorption spectra, particulate pigments, and hydrochemical constituents were measured in the western Bay of Bengal (BoB) during July-August 2010 when influence of river discharge is at peak. Chromophoric dissolved organic matter (CDOM) absorption coefficient (aCDOM(440)) displayed a significant inverse linear relationship with salinity in the surface waters implying conservative mixing of marine and terrestrial end members. The northern part of the study area is influenced by discharge from the river Ganga and a dominant terrestrial CDOM signal is seen. The southern part receives discharge from peninsular rivers with corresponding signals of higher CDOM than the linear model would indicate and higher UV-specific absorption coefficient (SUVA) indicating more aged and humified DOM. Lower contribution of CDOM to total non-water absorption and higher phytoplankton biomass (chlorophyll a absorption coefficient, aph(440)) but lower chlorophyll a specific phytoplankton absorption coefficient (a{ph/*}(440)) characterize the northern part, compared to the southern part. Chlorophyll b had a distinct linear relationship with chlorophyll a in the latter. The size index (SI) indicated dominance of microphytoplankton in the northern and nano and picophytoplankton in the southern parts. Chlorophyll a is significantly related to a{ph/*}(440) by an inverse power model in the northern part but by an inverse linear model in the southern part. Our study suggests that knowledge of the phytoplankton community structure is essential to improve chlorophyll a algorithm in the coastal Bay of Bengal.

  18. Development of a new generation gravity map of Antarctica: ADGRAV Antarctic Digital Gravity Synthesis

    Directory of Open Access Journals (Sweden)

    R. A. Arko

    1999-06-01

    Full Text Available The U.S. National Science Foundation (NSF has agreed to support the development of a new generation gravity map of Antarctica (ADGRAV - Antarctic Digital Gravity Synthesis, funding the development of a web based access tool. The goal of this project is the creation of an on-line Antarctic gravity database which will facilitate access to improved high resolution satellite gravity models, in conjunction with shipboard, airborne, and land based gravity measurements for the continental regions. This database will complement parallel projects underway to develop new continental bedrock (BEDMAP and magnetic (ADMAP maps of Antarctica.

  19. NSF's role in Antarctic environment scrutinized

    Science.gov (United States)

    Bush, Susan

    In the last few years, the National Science Foundation has come under criticism by environmental groups for inadequate stewardship in the U.S. Antarctic Program's environmental issues. Since 1978, NSF was given full responsibility, by Executive Order, for budgeting and managing the entire U.S. national program in Antarctica, including logistics support. NSF has also been responsible for the compliance of the U.S. Antarctic Program with environmental protection measures agreed to by the Antarctic Treaty nations. Specifically under fire by environmentalists have been NSF's maintenance of a land-fill, open-air burning of solid waste, and the removal of toxic substances. According to Peter E. Wilkniss, director of the Division of Polar Programs at NSF, open burning is no longer taking place and will not be allowed in the future.

  20. Antarctic “quiet” site stirs debate

    Science.gov (United States)

    Simarski, Lynn Teo

    Geophysicists from the United States and New Zealand plan to meet in the coming months to assess the electromagnetic pollution of an Antarctic site especially designated for research. U.S. scientists charge that a satellite Earth station erected apparently inside the preserve by New Zealand's Telecom company could interfere with experiments on the ionosphere and magnetosphere (Eos, April 28, 1992). The Site of Special Scientific Interest at Arrival Heights, the only Antarctic preserve specifically for physical science, is located near the U.S. McMurdo and New Zealand Scott bases.Debate over the Telecom facility inter-twines diplomatic and scientific issues. One question is whether the station violates the Antarctic treaty. Secondly, does it actually impair research at the site—or could it harm future experiments? To deepen the imbroglio, those involved from both nations say that transmissions from sources off-site also interfere with research—raising doubts about how pristine the site really is.

  1. The Antarctic cryptoendolithic ecosystem - Relevance to exobiology

    Science.gov (United States)

    Friedmann, E. I.; Ocampo-Friedmann, R.

    1984-01-01

    Cryptoendolithic microorganisms in the Antarctic desert live inside porous sandstone rocks, protected by a thin rock crust. While the rock surface is abiotic, the microclimate inside the rock is comparatively mild. These organisms may have descended from early, pre-glaciation Antarctic life forms and thus may represent the last outpost of life in a gradually deteriorating environment. Assuming that life once arose on Mars, it is conceivable that, following the loss of water, the last of surviving organisms withdrew to similar insulated microenvironments. Because such microscopic pockets have little connection with the outside environment, their detection may be difficult. The chances that the Viking lander could sample cryptoendolithic microorganisms in the Antarctic desert would be infinitesimal.

  2. Solar flare irradiation records in Antarctic meteorites

    Science.gov (United States)

    Goswami, J. N.

    1981-01-01

    The observation of tracks from solar flare heavy nuclei in Antarctic meteorite samples is reported. In an analysis of nuclear track densities in eight L and H chondrites of low metamorphic grade, it was found that two interior specimens of sample 77216, an L-3 chondrite, contain olivine grains with track densities much higher than the average track densities, indicating precompaction irradiation by solar flares in different shielding conditions. Preliminary data from mass spectroscopic analyses show a large excess of noble gases, with a Ne-20/Ne-22 ratio of greater than or equal to 10, indicating the presence of solar-type noble gas. Results of track density measurements in the other Antarctic meteorites range from 10,000 to 4,000,000/sq cm, which is within the range observed in non-Antarctic L-group meteorites

  3. Meteorological observatory for Antarctic data collection

    International Nuclear Information System (INIS)

    In the last years, a great number of automatic weather stations was installed in Antarctica, with the aim to examine closely the weather and climate of this region and to improve the coverage of measuring points on the Antarctic surface. In 1987 the Italian Antarctic Project started to set up a meteorological network, in an area not completely covered by other countries. Some of the activities performed by the meteorological observatory, concerning technical functions such as maintenance of the AWS's and the execution of radio soundings, or relating to scientific purposes such as validation and elaboration of collected data, are exposed. Finally, some climatological considerations on the thermal behaviour of the Antarctic troposphere such as 'coreless winter', and on the wind field, including katabatic flows in North Victoria Land are described

  4. Antarctic icebergs melt over the Southern Ocean : Climatology and impact on sea ice

    Science.gov (United States)

    Merino, Nacho; Le Sommer, Julien; Durand, Gael; Jourdain, Nicolas C.; Madec, Gurvan; Mathiot, Pierre; Tournadre, Jean

    2016-08-01

    Recent increase in Antarctic freshwater release to the Southern Ocean is suggested to contribute to change in water masses and sea ice. However, climate models differ in their representation of the freshwater sources. Recent improvements in altimetry-based detection of small icebergs and in estimates of the mass loss of Antarctica may help better constrain the values of Antarctic freshwater releases. We propose a model-based seasonal climatology of iceberg melt over the Southern Ocean using state-of-the-art observed glaciological estimates of the Antarctic mass loss. An improved version of a Lagrangian iceberg model is coupled with a global, eddy-permitting ocean/sea ice model and compared to small icebergs observations. Iceberg melt increases sea ice cover, about 10% in annual mean sea ice volume, and decreases sea surface temperature over most of the Southern Ocean, but with distinctive regional patterns. Our results underline the importance of improving the representation of Antarctic freshwater sources. This can be achieved by forcing ocean/sea ice models with a climatological iceberg fresh-water flux.

  5. A new 1 km digital elevation model of the Antarctic derived from combined satellite radar and laser data - Part 1: Data and methods

    OpenAIRE

    J. L. Bamber; J. L. Gomez-Dans; Griggs, J. A.

    2009-01-01

    Digital elevation models (DEMs) of the whole of Antarctica have been derived, previously, from satellite radar altimetry (SRA) and limited terrestrial data. Near the ice sheet margins and in other areas of steep relief the SRA data tend to have relatively poor coverage and accuracy. To remedy this and to extend the coverage beyond the latitudinal limit of the SRA missions (81.5° S) we have combined laser altimeter measurements from the Geosciences Laser Altimeter System onboard ICESat...

  6. Climate Change Influences on Antarctic Bird Populations

    Science.gov (United States)

    Korczak-Abshire, Małgorzata

    2010-01-01

    Rapid changes in the major environmental variables like: temperature, wind and precipitation have occurred in the Antarctic region during the last 50 years. In this very sensitive region, even small changes can potentially lead to major environmental perturbations. Then the climate change poses a new challenge to the survival of Antarctic wildlife. As important bioindicators of changes in the ecosystem seabirds and their response to the climate perturbations have been recorded. Atmospheric warming and consequent changes in sea ice conditions have been hypothesized to differentially affect predator populations due to different predator life-history strategies and substantially altered krill recruitment dynamics.

  7. A synthesis of bentho-pelagic coupling on the Antarctic shelf: Food banks, ecosystem inertia and global climate change

    Science.gov (United States)

    Smith, Craig R.; Mincks, Sarah; DeMaster, David J.

    2006-04-01

    The Antarctic continental shelf is large, deep (500-1000 m), and characterized by extreme seasonality in sea-ice cover and primary production. Intense seasonality and short pelagic foodwebs on the Antarctic shelf may favor strong bentho-pelagic coupling, whereas unusual water depth combined with complex topography and circulation could cause such coupling to be weak. Here, we address six questions regarding the nature and strength of coupling between benthic and water-column processes on the continental shelf surrounding Antarctica. We find that water-column production is transmitted to the shelf floor in intense pulses of particulate organic matter, although these pulses are often difficult to correlate with local phytoplankton blooms or sea-ice conditions. On regional scales, benthic habitat variability resulting from substrate type, current regime, and iceberg scour often may obscure the imprint of water-column productivity on the seafloor. However, within a single habitat type, i.e. the muddy sediments that characterize much of the deep Antarctic shelf, macrobenthic biomass appears to be correlated with regional primary production and sea-ice duration. Over annual time-scales, many benthic ecological processes were initially expected to vary in phase with the extraordinary boom/bust cycle of production in the water column. However, numerous processes, including sediment respiration, deposit feeding, larval development, and recruitment, often are poorly coupled to the summer bloom season. Several integrative, time-series studies on the Antarctic shelf suggest that this lack of phasing may result in part from the accumulation of a persistent sediment food bank that buffers the benthic ecosystem from the seasonal variability of the water column. As a consequence, a variety of benthic parameters (e.g., sediment respiration, inventories of labile organic matter, macrobenthic biomass) may act as "low-pass" filters, responding to longer-term (e.g., inter

  8. A review of phytoplankton dynamics in tropical African lakes

    Directory of Open Access Journals (Sweden)

    Charles F. Musil

    2010-03-01

    Full Text Available This paper provides a synthesis of current knowledge on phytoplankton production, seasonality, and stratification in tropical African lakes and considers the effects of nutrient enrichment and the potential impacts of climate warming on phytoplankton production and composition. Tropical African lakes are especially sensitive to climate warming as they experience wide fluctuations in the thermocline over a narrow range of high water temperatures. Recent climate warming has reduced phytoplankton biomass and production in the lakes. A decline in the production of palatable chlorophytes and an increase in cyanobacteria has led to reduced zooplankton production and a consequent decline in fish stocks, all of which can be associated with the elevated water temperatures. This indicates that even moderate climate warming may destabilise phytoplankton dynamics in tropical African lakes, thereby reducing water quality and food resources for planktivorous fish, with consequent negative impacts on human livelihoods.

  9. What drives the increased phytoplankton biomass in the Arabian Sea?

    Digital Repository Service at National Institute of Oceanography (India)

    PrasannaKumar, S.; Roshin, R.P.; Narvekar, J.; DineshKumar, P.K.; Vivekanandan, E.

    Sea during 1997-2007 showed a weak increasing trend. Contrary to the earlier hypothesis, our analysis showed that this increased phytoplankton biomass was not driven by the strengthening winds during summer monsoon. In fact, the basin...

  10. Turbulent mixing, restratification, and phytoplankton growth at a submesoscale eddy

    Science.gov (United States)

    Taylor, J. R.

    2016-06-01

    High-resolution large-eddy simulations are used to study the influence of submesoscale mixed layer instability and small-scale turbulence on phytoplankton growth in light-limited conditions. Four simulations are considered with small-scale turbulence driven by varying levels of surface cooling. Significant small-scale turbulence is seen even without surface forcing, and the downward mixing of phytoplankton is sufficient to briefly delay the developing bloom. Moderate and strong values of the constant surface heat flux (Q =- 10,-100 W/m2) are sufficient to prevent a bloom. In contrast to the critical depth hypothesis, the growth rate for phytoplankton does not appear to be controlled by the mixed layer depth. Instead, a comparison between the turbulent diffusivity above the compensation depth and a critical value predicted by the critical turbulence hypothesis closely matches the timing and magnitude of phytoplankton growth.

  11. Examination of Daytime Length's Influence on Phytoplankton Growth in Jiaozhou Bay, China

    Institute of Scientific and Technical Information of China (English)

    杨东方; 高振会; 张经; 崔文林; 石强

    2004-01-01

    This study showed how the daytime length in Jiaozhou Bay affected the water temperature, which in turn affected the phytoplankton growth when solar radiation was sufficient for phytoplankton photosynthesis. Jiaozhou Bay observation data collected from May 1991 to February 1994 were used to analyze the daytime length vs water temperature relationship. Our study showed that daytime length and the variation controlled the cycle of water temperature flunctuation. Should the cyclic variation curve of the daytime length be moved back for two months it would be superimposed with temperature change. The values of daytime length and temperature that calculated in the dynamical model of daytime length lag vs water temperature were consistent with observed values. The light radiation and daytime length in this model determined the photochemistry process and the enzymic catalysis process of phytoplankton photosynthesis. In addition, by considering the effect of the daytime length on water temperature and photosynthesis, we could comprehend the joint effect of daytime length, water temperature, and nutrients, on the spatiotemporal variation of primary production in Jiaozhou Bay.

  12. Regime shift from phytoplankton to macrophyte dominance in a large river: Top-down versus bottom-up effects

    Energy Technology Data Exchange (ETDEWEB)

    Ibanez, Carles, E-mail: carles.ibanez@irta.cat [IRTA Aquatic Ecosystems, Carretera Poble Nou, Km 5.5, 43540 St. Carles de la Rapita, Catalonia (Spain); Alcaraz, Carles; Caiola, Nuno; Rovira, Albert; Trobajo, Rosa [IRTA Aquatic Ecosystems, Carretera Poble Nou, Km 5.5, 43540 St. Carles de la Rapita, Catalonia (Spain); Alonso, Miguel [United Research Services S.L., Urgell 143, 08036 Barcelona, Catalonia (Spain); Duran, Concha [Confederacion Hidrografica del Ebro, Sagasta 24-26, 50071 Zaragoza, Aragon (Spain); Jimenez, Pere J. [Grup Natura Freixe, Major 56, 43750 Flix, Catalonia (Spain); Munne, Antoni [Agencia Catalana de l' Aigua, Provenca 204-208, 08036 Barcelona, Catalonia (Spain); Prat, Narcis [Departament d' Ecologia, Universitat de Barcelona, Diagonal 645, 08028 Barcelona Catalonia (Spain)

    2012-02-01

    The lower Ebro River (Catalonia, Spain) has recently undergone a regime shift from a phytoplankton-dominated to a macrophyte-dominated system. This shift is well known in shallow lakes but apparently it has never been documented in rivers. Two initial hypotheses to explain the collapse of the phytoplankton were considered: a) the diminution of nutrients (bottom-up); b) the filtering effect due to the colonization of the zebra mussel (top-down). Data on water quality, hydrology and biological communities (phytoplankton, macrophytes and zebra mussel) was obtained both from existing data sets and new surveys. Results clearly indicate that the decrease in phosphorus is the main cause of a dramatic decrease in chlorophyll and large increase in water transparency, triggering the subsequent colonization of macrophytes in the river bed. A Generalized Linear Model analysis showed that the decrease in dissolved phosphorus had a relative importance 14 times higher than the increase in zebra mussel density to explain the variation of total chlorophyll. We suggest that the described changes in the lower Ebro River can be considered a novel ecosystem shift. This shift is triggering remarkable changes in the biological communities beyond the decrease of phytoplankton and the proliferation of macrophytes, such as massive colonization of Simulidae (black fly) and other changes in the benthic invertebrate communities that are currently investigated. - Highlights: Black-Right-Pointing-Pointer We show a regime shift in a large river from phytoplankton to macrophyte dominance. Black-Right-Pointing-Pointer Two main hypotheses are considered: nutrient decrease and zebra mussel grazing. Black-Right-Pointing-Pointer Phosphorus depletion is found to be the main cause of the phytoplankton decline. Black-Right-Pointing-Pointer We conclude that oligotrophication triggered the colonization of macrophytes. Black-Right-Pointing-Pointer This new regime shift in a river is similar to that described

  13. Vertical distribution and composition of phytoplankton under the influence of an upper mixed layer.

    Science.gov (United States)

    Ryabov, Alexei B; Rudolf, Lars; Blasius, Bernd

    2010-03-01

    The vertical distribution of phytoplankton is of fundamental importance for the dynamics and structure of aquatic communities. Here, using an advection-reaction-diffusion model, we investigate the distribution and competition of phytoplankton species in a water column, in which inverse resource gradients of light and a nutrient can limit growth of the biomass. This problem poses a challenge for ecologists, as the location of a production layer is not fixed, but rather depends on many internal parameters and environmental factors. In particular, we study the influence of an upper mixed layer (UML) in this system and show that it leads to a variety of dynamic effects: (i) Our model predicts alternative density profiles with a maximum of biomass either within or below the UML, thereby the system may be bistable or the relaxation from an unstable state may require a long-lasting transition. (ii) Reduced mixing in the deep layer can induce oscillations of the biomass; we show that a UML can sustain these oscillations even if the diffusivity is less than the critical mixing for a sinking phytoplankton population. (iii) A UML can strongly modify the outcome of competition between different phytoplankton species, yielding bistability both in the spatial distribution and in the species composition. (iv) A light limited species can obtain a competitive advantage if the diffusivity in the deep layers is reduced below a critical value. This yields a subtle competitive exclusion effect, where the oscillatory states in the deep layers are displaced by steady solutions in the UML. Finally, we present a novel graphical approach for deducing the competition outcome and for the analysis of the role of a UML in aquatic systems.

  14. Tilapia rendalli increases phytoplankton biomass of a shallow tropical lake

    Directory of Open Access Journals (Sweden)

    Lúcia Helena Sampaio da Silva

    2014-12-01

    Full Text Available AIM: This study aimed to experimentally test the influence of a planktivorous filter-feeding fish (Tilapia rendalli on the phytoplankton dynamics of a small and shallow tropical reservoir (Lake Monte Alegre, Brazil. Adults of T. rendalli of this lake feed preferentially on phytoplankton, and we hypothesize that: I adults of T. rendalli will decrease the phytoplankton biomass and composition through direct herbivory, and II as it is a eutrophic system, fish would not have strong influence on phytoplankton through nutrient cycling. METHODS: To evaluate these different effects on algae, a field experiment was performed in the summer period for 15 days, in mesocosms isolated from the sediment, using a control group (no fish and a treatment group (with one fish in each mesocosm. Physical and chemical variables and phyto- and zooplankton were evaluated at the start, middle, and end of the experiment. RESULTS: At the end of the experiment, it was observed a significant increase in ammonium concentrations and total phytoplankton biomass, Cyanobacteria and Zygnemaphyceae and all size classes except class II (20-30 µm in the treatment group (with fish. The biomass increase of the potentially toxic cyanobacterium Cylindrospermospsis raciborskii was also observed in the fish treatment at the end of the experimental period. CONCLUSION: This study did not support both initial hypotheses. It supports the assertion that in tropical water bodies, with similar characteristics to the environment studied, planktivorous filter-feeding fish, such as T. rendalli, are not effective in reducing phytoplankton biomass through direct grazing, even when phytoplankton is one of their main food items. T. rendalli can contribute to the increase of phytoplankton biomass and can promote or increase the eutrophication of aquatic systems.

  15. Differential Growth Responses of Marine Phytoplankton to Herbicide Glyphosate

    OpenAIRE

    Wang, Cong; Lin, Xin; Li, Ling; Lin, Senjie

    2016-01-01

    Glyphosate is a globally popular herbicide to kill weeds and its wide applications may lead to accumulation in coastal oceans as a source of phosphorus (P) nutrient or growth inhibitor of phytoplankton. We studied the physiological effects of glyphosate on fourteen species representing five major coastal phytoplankton phyla (haptophyta, bacillariophyta, dinoflagellata, raphidophyta, and chlorophyta). Based on growth responses to different concentrations of glyphosate under contrasting dissolv...

  16. Ultrafast quantitative time-stretch imaging flow cytometry of phytoplankton

    Science.gov (United States)

    Lai, Queenie T. K.; Lau, Andy K. S.; Tang, Anson H. L.; Wong, Kenneth K. Y.; Tsia, Kevin K.

    2016-03-01

    Comprehensive quantification of phytoplankton abundance, sizes and other parameters, e.g. biomasses, has been an important, yet daunting task in aquatic sciences and biofuel research. It is primarily because of the lack of effective tool to image and thus accurately profile individual microalgae in a large population. The phytoplankton species are highly diversified and heterogeneous in terms of their sizes and the richness in morphological complexity. This fact makes time-stretch imaging, a new ultrafast real-time optical imaging technology, particularly suitable for ultralarge-scale taxonomic classification of phytoplankton together with quantitative image recognition and analysis. We here demonstrate quantitative imaging flow cytometry of single phytoplankton based on quantitative asymmetric-detection time-stretch optical microscopy (Q-ATOM) - a new time-stretch imaging modality for label-free quantitative phase imaging without interferometric implementations. Sharing the similar concept of Schlieren imaging, Q-ATOM accesses multiple phase-gradient contrasts of each single phytoplankton, from which the quantitative phase profile is computed. We employ such system to capture, at an imaging line-scan rate of 11.6 MHz, high-resolution images of two phytoplankton populations (scenedesmus and chlamydomonas) in ultrafast microfluidic flow (3 m/s). We further perform quantitative taxonomic screening analysis enabled by this technique. More importantly, the system can also generate quantitative phase images of single phytoplankton. This is especially useful for label-free quantification of biomasses (e.g. lipid droplets) of the particular species of interest - an important task adopted in biofuel applications. Combining machine learning for automated classification, Q-ATOM could be an attractive platform for continuous and real-time ultralarge-scale single-phytoplankton analysis.

  17. Interactions of anthropogenic stress factors on marine phytoplankton

    OpenAIRE

    Häder, Donat-P.; Gao, Kunshan

    2015-01-01

    Phytoplankton are the main primary producers in aquatic ecosystems. Their biomass production and CO2 sequestration equals that of all terrestrial plants taken together. Phytoplankton productivity is controlled by a number of environmental factors, many of which currently undergo substantial changes due to anthropogenic global climate change. Most of these factors interact either additively or synergistically. Light availability is an absolute requirement for photosynthesis, but excessive visi...

  18. Strong responses of Southern Ocean phytoplankton communities to volcanic ash

    OpenAIRE

    Browning, T.J.; Bouman, H. A.; Henderson, G. M.; Mather, T.A.; D. M. Pyle; Schlosser, Christian; Woodward, E.M.S.; Moore, C. M.

    2014-01-01

    Volcanic eruptions have been hypothesized as an iron supply mechanism for phytoplankton blooms; however, little direct evidence of stimulatory responses has been obtained in the field. Here we present the results of twenty-one 1-2day bottle enrichment experiments from cruises in the South Atlantic and Southern Ocean which conclusively demonstrated a photophysiological and biomass stimulation of phytoplankton communities following supply of basaltic or rhyolitic volcanic ash. Furthermore, expe...

  19. Monitoring and prediction of phytoplankton dynamics in the North Sea

    OpenAIRE

    Huisman, J.; Laane, R.W.P.M.; Blauw, A.N.

    2015-01-01

    Phytoplankton forms the base of the marine food web, but when concentrations get too high, algal blooms can have adverse effects on ecosystems and aquaculture. Phytoplankton concentrations vary strongly in space and time. However, the nature and drivers of this variability are not yet well understood. For ecological assessments and for early warnings of harmful algal blooms, monitoring strategies are required with sufficiently high temporal and spatial resolution to capture the natural variab...

  20. Chemotaxis toward phytoplankton drives organic matter partitioning among marine bacteria.

    Science.gov (United States)

    Smriga, Steven; Fernandez, Vicente I; Mitchell, James G; Stocker, Roman

    2016-02-01

    The microenvironment surrounding individual phytoplankton cells is often rich in dissolved organic matter (DOM), which can attract bacteria by chemotaxis. These "phycospheres" may be prominent sources of resource heterogeneity in the ocean, affecting the growth of bacterial populations and the fate of DOM. However, these effects remain poorly quantified due to a lack of quantitative ecological frameworks. Here, we used video microscopy to dissect with unprecedented resolution the chemotactic accumulation of marine bacteria around individual Chaetoceros affinis diatoms undergoing lysis. The observed spatiotemporal distribution of bacteria was used in a resource utilization model to map the conditions under which competition between different bacterial groups favors chemotaxis. The model predicts that chemotactic, copiotrophic populations outcompete nonmotile, oligotrophic populations during diatom blooms and bloom collapse conditions, resulting in an increase in the ratio of motile to nonmotile cells and in the succession of populations. Partitioning of DOM between the two populations is strongly dependent on the overall concentration of bacteria and the diffusivity of different DOM substances, and within each population, the growth benefit from phycospheres is experienced by only a small fraction of cells. By informing a DOM utilization model with highly resolved behavioral data, the hybrid approach used here represents a new path toward the elusive goal of predicting the consequences of microscale interactions in the ocean.

  1. Constraining the Antarctic contribution to interglacial sea-level rise

    Science.gov (United States)

    Naish, T.; Mckay, R. M.; Barrett, P. J.; Levy, R. H.; Golledge, N. R.; Deconto, R. M.; Horgan, H. J.; Dunbar, G. B.

    2015-12-01

    Observations, models and paleoclimate reconstructions suggest that Antarctica's marine-based ice sheets behave in an unstable manner with episodes of rapid retreat in response to warming climate. Understanding the processes involved in this "marine ice sheet instability" is key for improving estimates of Antarctic ice sheet contribution to future sea-level rise. Another motivating factor is that far-field sea-level reconstructions and ice sheet models imply global mean sea level (GMSL) was up to 20m and 10m higher, respectively, compared with present day, during the interglacials of the warm Pliocene (~4-3Ma) and Late Pleistocene (at ~400ka and 125ka). This was when atmospheric CO2 was between 280 and 400ppm and global average surface temperatures were 1- 3°C warmer, suggesting polar ice sheets are highly sensitive to relatively modest increases in climate forcing. Such magnitudes of GMSL rise not only require near complete melt of the Greenland Ice Sheet and the West Antarctic Ice Sheet, but a substantial retreat of marine-based sectors of East Antarctic Ice Sheet. Recent geological drilling initiatives on the continental margin of Antarctica from both ship- (e.g. IODP; International Ocean Discovery Program) and ice-based (e.g. ANDRILL/Antarctic Geological Drilling) platforms have provided evidence supporting retreat of marine-based ice. However, without direct access through the ice sheet to archives preserved within sub-glacial sedimentary basins, the volume and extent of ice sheet retreat during past interglacials cannot be directly constrained. Sediment cores have been successfully recovered from beneath ice shelves by the ANDRILL Program and ice streams by the WISSARD (Whillans Ice Stream Sub-glacial Access Research Drilling) Project. Together with the potential of the new RAID (Rapid Access Ice Drill) initiative, these demonstrate the technological feasibility of accessing the subglacial bed and deeper sedimentary archives. In this talk I will outline the

  2. Adaptive evolution of hepcidin genes in antarctic notothenioid fishes.

    Science.gov (United States)

    Xu, Qianghua; Cheng, Chi-Hing Christina; Hu, Peng; Ye, Hua; Chen, Zuozhou; Cao, Lixue; Chen, Lei; Shen, Yu; Chen, Liangbiao

    2008-06-01

    Hepcidin is a small bioactive peptide with dual roles as an antimicrobial peptide and as the principal hormonal regulator of iron homeostasis in human and mouse. Hepcidin homologs of very similar structures are found in lower vertebrates, all comprise approximately 20-25 amino acids with 8 highly conserved cysteines forming 4 intramolecular disulfide bonds, giving hepcidin a hairpin structure. Hepcidins are particularly diverse in teleost fishes, which may be related to the diversity of aquatic environments with varying degree of pathogen challenge, oxygenation, and iron concentration, factors known to alter hepcidin expression in mammals. We characterized the diversity of hepcidin genes of the Antarctic notothenioid fishes that are endemic to the world's coldest and most oxygen-rich marine water. Notothenioid fishes have at least 4 hepcidin variants, in 2 distinctive structural types. Type I hepcidins comprise 3 distinct variants that are homologs of the widespread 8-cysteine hepcidins. Type II is a novel 4-cysteine variant and therefore only 2 possible disulfide bonds, highly expressed in hematopoietic tissues. Analyses of d(N)/d(S) substitution rate ratios and likelihood ratio test under site-specific models detected significant signal of positive Darwinian selection on the mature hepcidin-coding sequence, suggesting adaptive evolution of notothenioid hepcidins. Genomic polymerase chain reaction and Southern hybridization showed that the novel type II hepcidin occurs exclusively in lineages of the Antarctic notothenioid radiation but not in the basal non-Antarctic taxa, and lineage-specific positive selection was detected on the branch leading to the type II hepcidin clade under branch-site models, suggesting adaptive evolution of the reduced cysteine variant in response to the polar environment. We also isolated a structurally distinct 4-cysteine (4cys) hepcidin from an Antarctic eelpout that is unrelated to the notothenioids but inhabits the same freezing

  3. Phytoplankton primary production in the world's estuarine-coastal ecosystems

    Science.gov (United States)

    Cloern, J. E.; Foster, S. Q.; Kleckner, A. E.

    2014-05-01

    Estuaries are biogeochemical hot spots because they receive large inputs of nutrients and organic carbon from land and oceans to support high rates of metabolism and primary production. We synthesize published rates of annual phytoplankton primary production (APPP) in marine ecosystems influenced by connectivity to land - estuaries, bays, lagoons, fjords and inland seas. Review of the scientific literature produced a compilation of 1148 values of APPP derived from monthly incubation assays to measure carbon assimilation or oxygen production. The median value of median APPP measurements in 131 ecosystems is 185 and the mean is 252 g C m-2 yr-1, but the range is large: from -105 (net pelagic production in the Scheldt Estuary) to 1890 g C m-2 yr-1 (net phytoplankton production in Tamagawa Estuary). APPP varies up to 10-fold within ecosystems and 5-fold from year to year (but we only found eight APPP series longer than a decade so our knowledge of decadal-scale variability is limited). We use studies of individual places to build a conceptual model that integrates the mechanisms generating this large variability: nutrient supply, light limitation by turbidity, grazing by consumers, and physical processes (river inflow, ocean exchange, and inputs of heat, light and wind energy). We consider method as another source of variability because the compilation includes values derived from widely differing protocols. A simulation model shows that different methods reported in the literature can yield up to 3-fold variability depending on incubation protocols and methods for integrating measured rates over time and depth. Although attempts have been made to upscale measures of estuarine-coastal APPP, the empirical record is inadequate for yielding reliable global estimates. The record is deficient in three ways. First, it is highly biased by the large number of measurements made in northern Europe (particularly the Baltic region) and North America. Of the 1148 reported values of

  4. Phytoplankton primary production in the world's estuarine-coastal ecosystems

    Science.gov (United States)

    Cloern, James E.; Foster, S.Q.; Kleckner, A.E.

    2014-01-01

    Estuaries are biogeochemical hot spots because they receive large inputs of nutrients and organic carbon from land and oceans to support high rates of metabolism and primary production. We synthesize published rates of annual phytoplankton primary production (APPP) in marine ecosystems influenced by connectivity to land – estuaries, bays, lagoons, fjords and inland seas. Review of the scientific literature produced a compilation of 1148 values of APPP derived from monthly incubation assays to measure carbon assimilation or oxygen production. The median value of median APPP measurements in 131 ecosystems is 185 and the mean is 252 g C m−2 yr−1, but the range is large: from −105 (net pelagic production in the Scheldt Estuary) to 1890 g C m−2 yr−1 (net phytoplankton production in Tamagawa Estuary). APPP varies up to 10-fold within ecosystems and 5-fold from year to year (but we only found eight APPP series longer than a decade so our knowledge of decadal-scale variability is limited). We use studies of individual places to build a conceptual model that integrates the mechanisms generating this large variability: nutrient supply, light limitation by turbidity, grazing by consumers, and physical processes (river inflow, ocean exchange, and inputs of heat, light and wind energy). We consider method as another source of variability because the compilation includes values derived from widely differing protocols. A simulation model shows that different methods reported in the literature can yield up to 3-fold variability depending on incubation protocols and methods for integrating measured rates over time and depth. Although attempts have been made to upscale measures of estuarine-coastal APPP, the empirical record is inadequate for yielding reliable global estimates. The record is deficient in three ways. First, it is highly biased by the large number of measurements made in northern Europe (particularly the Baltic region) and North America. Of the 1148

  5. The near-surface wind field over the Antarctic continent

    Science.gov (United States)

    van Lipzig, N. P. M.; Turner, J.; Colwell, S. R.; van den Broeke, M. R.

    2004-12-01

    A 14 year integration with a regional atmospheric model has been used to determine the near-surface climatological wind field over the Antarctic ice sheet at a horizontal grid spacing of 55 km. Previous maps of the near-surface wind field were generally based on models ignoring the large-scale pressure-gradient forcing term in the momentum equation. Presently, state-of-the-art atmospheric models include all pressure-gradient forcing terms. Evaluation of our model output against in situ data shows that the model is able to represent realistically the observed increase in wind speed going from the interior to the coast, as well as the observed wind direction at South Pole and Dumont d'Urville and the bimodal wind distribution at Halley.

  6. Regional Changes in the Sea Ice Cover and Ice Production in the Antarctic

    Science.gov (United States)

    Comiso, Josefino C.

    2011-01-01

    Coastal polynyas around the Antarctic continent have been regarded as sea ice factories because of high ice production rates in these regions. The observation of a positive trend in the extent of Antarctic sea ice during the satellite era has been intriguing in light of the observed rapid decline of the ice extent in the Arctic. The results of analysis of the time series of passive microwave data indicate large regional variability with the trends being strongly positive in the Ross Sea, strongly negative in the Bellingshausen/Amundsen Seas and close to zero in the other regions. The atmospheric circulation in the Antarctic is controlled mainly by the Southern Annular Mode (SAM) and the marginal ice zone around the continent shows an alternating pattern of advance and retreat suggesting the presence of a propagating wave (called Antarctic Circumpolar Wave) around the circumpolar region. The results of analysis of the passive microwave data suggest that the positive trend in the Antarctic sea ice cover could be caused primarily by enhanced ice production in the Ross Sea that may be associated with more persistent and larger coastal polynyas in the region. Over the Ross Sea shelf, analysis of sea ice drift data from 1992 to 2008 yields a positive rate-of-increase in the net ice export of about 30,000 km2 per year. For a characteristic ice thickness of 0.6 m, this yields a volume transport of about 20 km3/year, which is almost identical, within error bars, to our estimate of the trend in ice production. In addition to the possibility of changes in SAM, modeling studies have also indicated that the ozone hole may have a role in that it causes the deepening of the lows in the western Antarctic region thereby causing strong winds to occur offthe Ross-ice shelf.

  7. The multi-millennial Antarctic commitment to future sea-level rise.

    Science.gov (United States)

    Golledge, N R; Kowalewski, D E; Naish, T R; Levy, R H; Fogwill, C J; Gasson, E G W

    2015-10-15

    Atmospheric warming is projected to increase global mean surface temperatures by 0.3 to 4.8 degrees Celsius above pre-industrial values by the end of this century. If anthropogenic emissions continue unchecked, the warming increase may reach 8-10 degrees Celsius by 2300 (ref. 2). The contribution that large ice sheets will make to sea-level rise under such warming scenarios is difficult to quantify because the equilibrium-response timescale of ice sheets is longer than those of the atmosphere or ocean. Here we use a coupled ice-sheet/ice-shelf model to show that if atmospheric warming exceeds 1.5 to 2 degrees Celsius above present, collapse of the major Antarctic ice shelves triggers a centennial- to millennial-scale response of the Antarctic ice sheet in which enhanced viscous flow produces a long-term commitment (an unstoppable contribution) to sea-level rise. Our simulations represent the response of the present-day Antarctic ice-sheet system to the oceanic and climatic changes of four representative concentration pathways (RCPs) from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. We find that substantial Antarctic ice loss can be prevented only by limiting greenhouse gas emissions to RCP 2.6 levels. Higher-emissions scenarios lead to ice loss from Antarctic that will raise sea level by 0.6-3 metres by the year 2300. Our results imply that greenhouse gas emissions in the next few decades will strongly influence the long-term contribution of the Antarctic ice sheet to global sea level.

  8. The multi-millennial Antarctic commitment to future sea-level rise.

    Science.gov (United States)

    Golledge, N R; Kowalewski, D E; Naish, T R; Levy, R H; Fogwill, C J; Gasson, E G W

    2015-10-15

    Atmospheric warming is projected to increase global mean surface temperatures by 0.3 to 4.8 degrees Celsius above pre-industrial values by the end of this century. If anthropogenic emissions continue unchecked, the warming increase may reach 8-10 degrees Celsius by 2300 (ref. 2). The contribution that large ice sheets will make to sea-level rise under such warming scenarios is difficult to quantify because the equilibrium-response timescale of ice sheets is longer than those of the atmosphere or ocean. Here we use a coupled ice-sheet/ice-shelf model to show that if atmospheric warming exceeds 1.5 to 2 degrees Celsius above present, collapse of the major Antarctic ice shelves triggers a centennial- to millennial-scale response of the Antarctic ice sheet in which enhanced viscous flow produces a long-term commitment (an unstoppable contribution) to sea-level rise. Our simulations represent the response of the present-day Antarctic ice-sheet system to the oceanic and climatic changes of four representative concentration pathways (RCPs) from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. We find that substantial Antarctic ice loss can be prevented only by limiting greenhouse gas emissions to RCP 2.6 levels. Higher-emissions scenarios lead to ice loss from Antarctic that will raise sea level by 0.6-3 metres by the year 2300. Our results imply that greenhouse gas emissions in the next few decades will strongly influence the long-term contribution of the Antarctic ice sheet to global sea level. PMID:26469052

  9. Antarctic Data Management as Part of the IPY Legacy

    Science.gov (United States)

    de Bruin, T.

    2006-12-01

    The Antarctic Treaty states that "scientific observations and results from Antarctica shall be exchanged and made freely available". Antarctica includes the Southern Ocean. In support of this, National Antarctic Data Centres (NADC) are being established to catalogue data sets and to provide information on data sets to scientists and others with interest in Antarctic science. The Joint Committee on Antarctic Data Management (JCADM) was established by the Scientific Committee on Antarctic Research (SCAR) and the Council of Managers of National Antarctic Programs (COMNAP). JCADM comprises representatives of the National Antarctic Data Centres. Currently 30 nations around the world are represented in JCADM. JCADM is responsible for the Antarctic Master Directory (AMD), the internationally accessible, web-based, searchable record of Antarctic and Southern Ocean data set descriptions. The AMD is directly integrated into the international Global Change Master Directory (GCMD) to help further merge Antarctic science into global science. The AMD is a resource for scientists to advertise the data they have collected and to search for data they may need. JCADM is the Antarctic component of the IPY Data Infrastructure, which is presently being developed. This presentation will give an overview of the organization of Antarctic and Southern Ocean data management with sections on the organizational structure of JCADM, contents of the Antarctic Master Directory, relationships to the SCAR Scientific Research Programmes (SRP) and IPY, international embedding and connections with discipline-based peer organizations like the International Oceanographic Data and Information Exchange Committee (IODE). It will focus primarily on the role that an existing infrastructure as JCADM, may play in the development of the IPY Data Infrastructure and will provide considerations for IPY data management, based on the experiences in Antarctic and oceanographic data management.

  10. Contrasting Arctic and Antarctic sea ice temperatures

    Science.gov (United States)

    Vancoppenolle, Martin; Raphael, Marilyn; Rousset, Clément; Vivier, Frédéric; Moreau, Sébastien; Delille, Bruno; Tison, Jean-Louis

    2016-04-01

    Sea ice temperature affects the sea ice growth rate, heat content, permeability and habitability for ice algae. Large-scale simulations with NEMO-LIM suggest large ice temperature contrasts between the Arctic and the Antarctic sea ice. First, Antarctic sea ice proves generally warmer than in the Arctic, in particular during winter, where differences reach up to ~10°C. Second, the seasonality of temperature is different among the two hemispheres: Antarctic ice temperatures are 2-3°C higher in spring than they are in fall, whereas the opposite is true in the Arctic. These two key differences are supported by the available ice core and mass balance buoys temperature observations, and can be attributed to differences in air temperature and snow depth. As a result, the ice is found to be habitable and permeable over much larger areas and much earlier in late spring in the Antarctic as compared with the Arctic, which consequences on biogeochemical exchanges in the sea ice zone remain to be evaluated.

  11. Relevance of antarctic microbial ecosystems to exobiology

    Science.gov (United States)

    Mckay, Christopher P.

    1993-01-01

    Antarctic microbial ecosystems which provide biological and physical analogs that can be used in exobiology are studied. Since the access to extraterrestrial habitats is extremely difficult, terrestrial analogs represent the best opportunity for both formulation and preliminary testing of hypothesis about life. Antarctica, as one of few suitable environments on earth is considered to be a major locus of progress in exobiology.

  12. A new 1 km digital elevation model of the Antarctic derived from combined satellite radar and laser data – Part 1: Data and methods

    Directory of Open Access Journals (Sweden)

    J. L. Bamber

    2009-05-01

    Full Text Available Digital elevation models (DEMs of the whole of Antarctica have been derived, previously, from satellite radar altimetry (SRA and limited terrestrial data. Near the ice sheet margins and in other areas of steep relief the SRA data tend to have relatively poor coverage and accuracy. To remedy this and to extend the coverage beyond the latitudinal limit of the SRA missions (81.5° S we have combined laser altimeter measurements from the Geosciences Laser Altimeter System onboard ICESat with SRA data from the geodetic phase of the ERS-1 satellite mission. The former provide decimetre vertical accuracy but with poor spatial coverage. The latter have excellent spatial coverage but a poorer vertical accuracy. By combining the radar and laser data using an optimal approach we have maximised the vertical accuracy and spatial resolution of the DEM and minimised the number of grid cells with an interpolated elevation estimate. We assessed the optimum resolution for producing a DEM based on a trade-off between resolution and interpolated cells, which was found to be 1 km. This resulted in just under 32% of grid cells having an interpolated value. The accuracy of the final DEM was assessed using a suite of independent airborne altimeter data and used to produce an error map. The RMS error in the new DEM was found to be roughly half that of the best previous 5 km resolution, SRA-derived DEM, with marked improvements in the steeper marginal and mountainous areas and between 81.5 and 86° S. The DEM contains a wealth of information related to ice flow. This is particularly apparent for the two largest ice shelves – the Filchner-Ronne and Ross – where the surface expression of flow of ice streams and outlet glaciers can be traced from the grounding line to the calving front. The surface expression of subglacial lakes and other basal features are also illustrated. We also use the DEM to derive new estimates of balance velocities and ice divide locations.

  13. A new 1 km digital elevation model of the Antarctic derived from combined satellite radar and laser data – Part 1: Data and methods

    Directory of Open Access Journals (Sweden)

    J. L. Bamber

    2008-11-01

    Full Text Available Digital elevation models (DEMs of Antarctica have been derived, previously, from satellite radar altimetry (SRA and limited terrestrial data. Near the ice sheet margins and in other areas of steep relief the SRA data tend to have relatively poor coverage and accuracy. To remedy this and to extend the coverage beyond the latitudinal limit of the SRA missions (81.5° S we have combined laser altimeter measurements from the Geosciences Laser Altimeter System onboard ICESat with SRA data from the geodetic phase of the ERS-1 satellite mission. The former provide decimetre vertical accuracy but with poor spatial coverage. The latter have excellent spatial coverage but a poorer vertical accuracy. By combining the radar and laser data using an optimal approach we have maximised the vertical accuracy and spatial resolution of the DEM and minimised the number of grid cells with an interpolated elevation estimate. We assessed the optimum resolution for producing a DEM based on a trade-off between resolution and interpolated cells, which was found to be 1 km. This resulted in just under 35% of grid cells having an interpolated value. The accuracy of the final DEM was assessed using a suite of independent airborne altimeter data and used to produce an error map. The RMS error in the new DEM was found to be roughly half that of the best previous 5 km resolution, SRA-derived DEM, with marked improvements in the steeper marginal and mountainous areas and between 81.5 and 86° S. The DEM contains a wealth of information related to ice flow. This is particularly apparent for the two largest ice shelves – the Filchner-Ronne and Ross – where the surface expression of flow of ice streams and outlet glaciers can be traced from the grounding line to the calving front. The surface expression of subglacial lakes and other basal features are also illustrated. We also use the DEM to derive new estimates of balance velocities and ice divide locations.

  14. A Palaeohydrological Shift during Neogene East Antarctic Ice Sheet Retreat

    Science.gov (United States)

    Rees-Owen, R. L.; Newton, R.; Ivanovic, R. F.; Francis, J.; Tindall, J. C.; Riding, J. B.

    2015-12-01

    The East Antarctic Ice Sheet is an important driver of global climate, playing a particular role in governing albedo and atmospheric circulation (eg. Singh et al., 2013). Recent evidence from marine sediment and terrestrial glaciovolcanic sequences suggests that the EAIS underwent periodic retreat and collapse in response to warmer climates during the late Neogene (14 to 3 million years ago). Mummified prostrate trees recovered from palaeosols at Oliver Bluffs in the Beardmore Glacier region, Transantarctic Mountains (85° S), represent a rare insight into the terrestrial palaeoclimate during one of these periods of retreat. Prostrate trees are an understudied but useful tool for interrogating endmember (e.g. periglacial) environments at high altitudes and latitudes. We present exciting new palaeoclimate data from the sequence at Oliver Bluffs. δ18O analysis of tree ring cellulose suggests that Antarctic summer palaeoprecipitation was enriched relative to today (-25 to -5‰ for ancient, -35 to -20‰ for modern); consistent with our isotope-enabled general circulation model simulations. The MBT/CBT palaeothermometer gives a summer temperature of 3-6ºC, consistent with other palaeobotanical climate indices. These geological and model data have wide-ranging implications for our understanding of the hydrological cycle during this time period. We present data suggesting that changes in moisture recycling and source region indicate a markedly different hydrological cycle.

  15. Methyl mercury uptake by diverse marine phytoplankton and trophic transfer to zooplankton

    Science.gov (United States)

    Lee, C. S.; Fisher, N. S.

    2014-12-01

    While it is well known that methylmercury (MeHg) biomagnifies in aquatic food chains, few studies have quantified its bioaccumulation in marine phytoplankton from seawater, even though that is overwhelmingly the largest bioaccumulation step. Aquatic animals acquire MeHg mainly from dietary exposure and it is important to evaluate the bioaccumulation of this compound in planktonic organisms that form the base of marine food webs. We used a gamma-emitting radioisotope, 203Hg, to assess the rate and extent of MeHg uptake in marine diatoms, dinoflagellates, coccolithophores, cryptophytes chlorophytes, and cyanobacteria held in unialgal cultures under varying temperature and light conditions. For experimental conditions in which the dissolved MeHg was at 300 pM, the uptake rates in all species ranged from 0.004 to 0.75 amol Hg μm-3 cell volume d-1 and reached steady state within 2 d. Volume concentration factors (VCFs) ranged from 0.4 to 60 x 105 for the different species. Temperature and light conditions had no direct effect on cellular MeHg uptake but ultimately affected growth of the cells, resulting in greater suspended particulate matter and associated MeHg. VCFs strongly correlated with cell surface area to volume ratios in all species. Assimilation efficiencies of MeHg from phytoplankton food (Thalassiosira pseudonana, Dunaliella tertiolecta and Rhodomonas salina) in a marine copepod grazer (Acartia tonsa) ranged from 74 to 92%, directly proportional to the cytoplasmic partitioning of MeHg in the phytoplankton cells. MeHg uptake in copepods from the aqueous phase was low and modeling shows that nearly all the MeHg acquired by this zooplankter is from diet. Herbivorous zooplankton can be an important link from phytoplankton at the base of the food web to fish higher in the food chain.

  16. Chromium uptake and adsorption in marine phytoplankton - Implications for the marine chromium cycle

    Science.gov (United States)

    Semeniuk, David M.; Maldonado, Maria T.; Jaccard, Samuel L.

    2016-07-01

    Using the radioisotope 51Cr, we investigated the controls of cellular Cr accumulation in an array of marine phytoplankton grown in environmentally relevant Cr concentrations (1-10 nM). Given the affinity of Cr(III) for amorphous Fe-hydroxide mineral surfaces, and the formation of these mineral phases on the outside of phytoplankton cells, extracellular Cr was monitored in a model diatom species (Thalassiosira weissflogii) as extracellular Fe concentrations varied. Extracellular Cr in T. weissflogii increased with increasing extracellular Fe, demonstrating that Cr may be removed from seawater via extracellular adsorption to phytoplankton. Short-term Cr(VI) and Cr(III) uptake experiments performed with T. weissflogii demonstrated that Cr(III) was the primary oxidation state adsorbing to cells and being internalized by them. Cellular Cr:C ratios (phytoplankton species surveyed were significantly lower than previously reported Cr:C ratios in marine particles with a high biogenic component (10-300 μmol Cr mol C-1). This indicates that Cr(III) likely accumulates in marine particles due to uptake and/or adsorption. Mass balance calculations demonstrate that surface water Cr deficits can be explained via loss of Cr(III) to exported particles, thereby providing a mechanism to account for the nutrient depth profile for Cr in modern seawater. Given the large fractionation of stable Cr isotopes during Cr(VI) reduction, Cr(III) associated with exported organic carbon is likely enriched in lighter isotopes. Most sedimentary Cr isotope studies have thus far neglected internal fractionating processes in the marine Cr cycle, but our data indicate that loss of Cr to exported particles may be traced in the sedimentary δ53Cr record.

  17. ARM West Antarctic Radiation Experiment (AWARE) Science Plan

    Energy Technology Data Exchange (ETDEWEB)

    Lubin, D [National Science Foundation; Bromwich, DH [Ohio State University; Russell, LM [Scripps Institution of Oceanography; Verlinde, J [The Pennsylvania State University; Vogelmann, AM [Brookhaven National Laboratory

    2015-10-01

    West Antarctica is one of the most rapidly warming regions on Earth, and this warming is closely connected with global sea level rise. The discovery of rapid climate change on the West Antarctic Ice Sheet (WAIS) has challenged previous explanations of Antarctic climate change that focused on strengthening of circumpolar westerlies in response to the positive polarity trend in the Southern Annular Mode. West Antarctic warming does not yet have a comprehensive explanation: dynamical mechanisms may vary from one season to the next, and these mechanisms very likely involve complex teleconnections with subtropical and tropical latitudes. The prime motivation for this proposal is that there has been no substantial atmospheric science or climatological field work on West Antarctica since the 1957 International Geophysical Year and that research continued for only a few years. Direct meteorological information on the WAIS has been limited to a few automatic weather stations for several decades, yet satellite imagery and meteorological reanalyses indicate that West Antarctica is highly susceptible to advection of warm and moist maritime air with related cloud cover, depending on the location and strength of low pressure cells in the Amundsen, Ross, and Bellingshausen Seas. There is a need to quantify the role of these changing air masses on the surface energy balance, including all surface energy components and cloud-radiative forcing. More generally, global climate model simulations are known to perform poorly over the Antarctic and Southern Oceans, and the marked scarcity of cloud information at southern high latitudes has so far inhibited significant progress. Fortunately, McMurdo Station, where the Atmospheric Radiation Measurement Facility’s (ARM’s) most advanced cloud and aerosol instrumentation is situated, has a meteorological relationship with the WAIS via circulation patterns in the Ross and Amundsen Seas. We can therefore gather sophisticated data with cloud

  18. Neogene kinematic history of Nazca-Antarctic-Phoenix slab windows beneath Patagonia and the Antarctic Peninsula

    Science.gov (United States)

    Breitsprecher, Katrin; Thorkelson, Derek J.

    2009-01-01

    The Patagonian slab window is a subsurface tectonic feature resulting from subduction of the Nazca-Antarctic spreading-ridge system (Chile Rise) beneath southern South America. The geometry of the slab window had not been rigorously defined, in part because of the complex nature of the history of ridge subduction in the southeast Pacific region, which includes four interrelated spreading-ridge systems since 20 Ma: first, the Nazca-Phoenix ridge beneath South America, then simultaneous subduction of the Nazca-Antarctic and the northern Phoenix-Antarctic spreading-ridge systems beneath South America, and the southern Phoenix-Antarctic spreading-ridge system beneath Antarctica. Spreading-ridge paleo-geographies and rotation poles for all relevant plate pairs (Nazca, Phoenix, Antarctic, South America) are available from 20 Ma onward, and form the mathematical basis of our kinematic reconstruction of the geometry of the Patagonia and Antarctic slab windows through Neogene time. At approximately 18 Ma, the Nazca-Phoenix-Antarctic oceanic (ridge-ridge-ridge) triple junction enters the South American trench; we recognize this condition as an unstable quadruple junction. Heat flow at this junction and for some distance beneath the forearc would be considerably higher than is generally recognized in cases of ridge subduction. From 16 Ma onward, the geometry of the Patagonia slab window developed from the subduction of the trailing arms of the former oceanic triple junction. The majority of the slab window's areal extent and geometry is controlled by the highly oblique (near-parallel) subduction angle of the Nazca-Antarctic ridge system, and by the high contrast in relative convergence rates between these two plates relative to South America. The very slow convergence rate of the Antarctic slab is manifested by the shallow levels achieved by the slab edge (< 45 km); thus no point on the Antarctic slab is sufficiently deep to generate "normal" mantle-derived arc-type magmas

  19. Nutrients and toxin producing phytoplankton control algal blooms – a spatio-temporal study in a noisy environment

    Indian Academy of Sciences (India)

    Ram Rup Sarkar; Horst Malchow

    2005-12-01

    A phytoplankton-zooplankton prey-predator model has been investigated for temporal, spatial and spatio-temporal dissipative pattern formation in a deterministic and noisy environment, respectively. The overall carrying capacity for the phytoplankton population depends on the nutrient level. The role of nutrient concentrations and toxin producing phytoplankton for controlling the algal blooms has been discussed