WorldWideScience

Sample records for visible earth phytoplankton

  1. 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…

  2. Visible light-dependent degradation of lipidic phytoplanktonic components during senescence: a review.

    Science.gov (United States)

    Rontani, J F

    2001-09-01

    Though most of the organic components of phytoplankton are susceptible to being photodegraded during senescence, until recent years there has been very little research in this area. Recently, however, there have been a renewal of interest, and the heterogeneous visible light-induced degradative reactions of lipidic compounds associated with phytodetritus have been studied. The present paper reviews the results obtained in the course of these studies. In the first part, the production and quenching of excited states of chlorophyll and toxic oxygen species (singlet oxygen, superoxide ion, hydroxyl radical and hydrogen peroxide) in healthy and senescent phytoplanktonic cells are discussed. Then, the photo-oxidation of the main lipidic cell components (chlorophyll, chlorophyll phytyl chain, carotenoids, sterols, unsaturated fatty acids, alkenones and unsaturated alkenes) in senescent phytoplanktonic cells is examined. Emphasis is given to the degradation rates and the mechanisms of visible light-induced degradation of the main lipidic components of phytoplankton and to the structure of the photoproducts formed. In each case, the selectivity of these compounds is discussed in order to select a "pool" of photoproducts able to act as tracers of photo-oxidative alterations in the marine medium. This "pool" of photoproducts could provide very useful information concerning the physiological state of phytoplanktonic communities and current environmental problems related to ozone depletion.

  3. 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.

  4. Robust Visible and Infrared Light Emitting Devices Using Rare-Earth-Doped GaN

    National Research Council Canada - National Science Library

    Steckl, Andrew

    2006-01-01

    Rare earth (RE) dopants (such as Er, Eu, Tm) in the wide bandgap semiconductor (WBGS) GaN are investigated for the fabrication of robust visible and infrared light emitting devices at a variety of wavelengths...

  5. Solar Irradiance Changes and Phytoplankton Productivity in Earth's Ocean Following Astrophysical Ionizing Radiation Events

    Science.gov (United States)

    Neale, Patrick J.; Thomas, Brian C.

    2016-04-01

    Two atmospheric responses to simulated astrophysical ionizing radiation events significant to life on Earth are production of odd-nitrogen species, especially NO2, and subsequent depletion of stratospheric ozone. Ozone depletion increases incident short-wavelength ultraviolet radiation (UVB, 280-315 nm) and longer (>600 nm) wavelengths of photosynthetically available radiation (PAR, 400-700 nm). On the other hand, the NO2 haze decreases atmospheric transmission in the long-wavelength UVA (315-400 nm) and short-wavelength PAR. Here, we use the results of previous simulations of incident spectral irradiance following an ionizing radiation event to predict changes in terran productivity focusing on photosynthesis of marine phytoplankton. The prediction is based on a spectral model of photosynthetic response, which was developed for the dominant genera in central regions of the ocean (Synechococcus and Prochlorococcus), and on remote-sensing-based observations of spectral water transparency, temperature, wind speed, and mixed layer depth. Predicted productivity declined after a simulated ionizing event, but the effect integrated over the water column was small. For integrations taking into account the full depth range of PAR transmission (down to 0.1% of utilizable PAR), the decrease was at most 2-3% (depending on strain), with larger effects (5-7%) for integrations just to the depth of the surface mixed layer. The deeper integrations were most affected by the decreased utilizable PAR at depth due to the NO2 haze, whereas shallower integrations were most affected by the increased surface UV. Several factors tended to dampen the magnitude of productivity responses relative to increases in surface-damaging radiation, for example, most inhibition in the modeled strains is caused by UVA and PAR, and the greatest relative increase in damaging exposure is predicted to occur in the winter when UV and productivity are low.

  6. TWINKLE - A Low Earth Orbit Visible and Infrared Exoplanet Spectroscopy Observatory

    Science.gov (United States)

    Tessenyi, M.; Savini, G.; Tinetti, G.; Tennyson, J.; Dhesi, M.; Joshua, M.

    2017-07-01

    Twinkle is a space mission designed for visible and near-IR spectroscopic observations of extrasolar planets. Twinkle's highly stable instrument will allow the photometric and spectroscopic observation of a wide range of planetary classes around different types of stars, with a focus on bright sources close to the ecliptic. The planets will be observed through transit and eclipse photometry and spectroscopy, as well as phase curves, eclipse mapping and multiple narrow-band time-series. The targets observed by Twinkle will be composed of known exoplanets mainly discovered by existing and upcoming ground surveys in our galaxy and will also feature new discoveries by space observatories (K2, GAIA, Cheops, TESS). Twinkle is a small satellite with a payload designed to perform high-quality astrophysical observations while adapting to the design of an existing Low Earth Orbit commercial satellite platform. The SSTL-300 bus, to be launched into a low-Earth sun-synchronous polar orbit by 2019, will carry a half-meter class telescope with two instruments (visible and near-IR spectrographs - between 0.4 and 4.5μm - with resolving power R˜300 at the lower end of the wavelength scale) using mostly flight proven spacecraft systems designed by Surrey Satellite Technology Ltd and a combination of high TRL instrumentation and a few lower TRL elements built by a consortium of UK institutes. The Twinkle design will enable the observation of the chemical composition and weather of at least 100 exoplanets in the Milky Way, including super-Earths (rocky planets 1-10 times the mass of Earth), Neptunes, sub-Neptunes and gas giants like Jupiter. It will also allow the follow-up photometric observations of 1000+ exoplanets in the visible and infrared, as well as observations of Solar system objects, bright stars and disks.

  7. Microemulsion synthesis, characterization of highly visible light responsive rare earth-doped Bi2O3.

    Science.gov (United States)

    Wu, Shuxing; Fang, Jianzhang; Xu, Xiaoxin; Liu, Zhang; Zhu, Ximiao; Xu, Weicheng

    2012-01-01

    In this paper, Bi(2)O(3) and rare earth (La, Ce)-doped Bi(2)O(3) visible-light-driven photocatalysts were prepared in a Triton X-100/n-hexanol/cyclohexane/water reverse microemulsion. The resulting materials were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area, photoluminescence spectra (PLS) and UV-Vis diffuse reflectance spectroscopy. The XRD patterns of the as-prepared catalysts calcined at 500 °C exhibited only the characteristic peaks of monoclinic α-Bi(2)O(3). PLS analysis implied that the separation efficiency for electron-hole has been enhanced when Bi(2)O(3) was doped with rare earth. UV-Vis diffuse reflectance spectroscopy measurements presented an extension of light absorption into the visible region. The photocatalytic activity of the samples was evaluated by degradation of methyl orange (MO) and 2,4-dichlorophenol (2,4-DCP). The results displayed that the photocatalytic activity of rare earth-doped Bi(2)O(3) was higher than that of dopant-free Bi(2)O(3). The optimal dopant amount of La or Ce was 1.0 mol%. And the mechanisms of influence on the photocatalytic activity of the catalysts were discussed. © 2012 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2012 The American Society of Photobiology.

  8. Increase the Visibility of Microbial Growth in a Winogradsky Column by Substituting Diatomaceous Earth for Sediment

    Directory of Open Access Journals (Sweden)

    Thomas G. Benoit

    2015-02-01

    Full Text Available The difficulty students have seeing the color associated with microbial growth in a traditional Winogradsky column can be overcome by substituting diatomaceous earth (DE for sediment. Microbial growth in a DE column is visible from the early stages of ecological succession and the colors produced appear more vibrant. A flat-sided tissue culture flask can be used as a column container to provide a large surface area for observation. The enhanced visual experience provided by a DE column increases student engagement and learning. Editor's Note:The ASM advocates that students must successfully demonstrate the ability to explain and practice safe laboratory techniques. For more information, read the laboratory safety section of the ASM Curriculum Recommendations: Introductory Course in Microbiology and the Guidelines for Biosafety in Teaching Laboratories, available at www.asm.org. The Editors of JMBE recommend that adopters of the protocols included in this article follow a minimum of Biosafety Level 1 practices.

  9. 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.

  10. Earth-Mars Telecommunications and Information Management System (TIMS): Antenna Visibility Determination, Network Simulation, and Management Models

    Science.gov (United States)

    Odubiyi, Jide; Kocur, David; Pino, Nino; Chu, Don

    1996-01-01

    This report presents the results of our research on Earth-Mars Telecommunications and Information Management System (TIMS) network modeling and unattended network operations. The primary focus of our research is to investigate the feasibility of the TIMS architecture, which links the Earth-based Mars Operations Control Center, Science Data Processing Facility, Mars Network Management Center, and the Deep Space Network of antennae to the relay satellites and other communication network elements based in the Mars region. The investigation was enhanced by developing Build 3 of the TIMS network modeling and simulation model. The results of several 'what-if' scenarios are reported along with reports on upgraded antenna visibility determination software and unattended network management prototype.

  11. Indicators: Phytoplankton

    Science.gov (United States)

    Phytoplankton are free-floating, microscopic algae that inhabit the sunlit, upper layer of most freshwater and marine environments. They are usually responsible for the color and clarity of lakes, wetlands, rivers, streams and estuaries.

  12. Injection Laser Using Rare Earth Doped GaN Thin Films for Visible and Infrared Applications

    Science.gov (United States)

    2010-05-01

    MBE control software: Crystal V7. Fig 3.3 Spectrum of residual gas analyzer (RGA). Fig 3.4 RHEED pattern on (a) 2d wurtzite and (b) 3d cubic GaN...mixture subflow will help reactant gas of main flow to reach the surface and promote 2D growth but suppress 3D growth. The effect of AlN and GaN buffer...reported by Chu-Kung. 1.3. Rare Earth Elements: Mysterious Lighting Sources Rare earth (RE) elements, also called Lanthanides , include fifteen

  13. Unraveling the Mechanisms of Visible Light Photocatalytic NO Purification on Earth-Abundant Insulator-Based Core-Shell Heterojunctions.

    Science.gov (United States)

    Wang, Hong; Sun, Yanjuan; Jiang, Guangming; Zhang, Yuxin; Huang, Hongwei; Wu, Zhongbiao; Lee, S C; Dong, Fan

    2018-01-08

    Earth-abundant insulators are seldom exploited as photocatalysts. In this work, we constructed a novel family of insulator-based heterojunctions and demonstrated their promising applications in photocatalytic NO purification, even under visible light irradiation. The heterojunction formed between the insulator SrCO3 and the photosensitizer BiOI, via a special SrCO3-BiOI core-shell structure, exhibits an enhanced visible light absorbance between 400-600 nm, and an unprecedentedly high photocatalytic NO removal performance. Further density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) analysis revealed that the covalent interaction between the O 2p orbital of the insulator (SrCO3, n-type) and the Bi 6p orbital of photosensitizer (BiOI, p-type) can provide an electron transfer channel between SrCO3 and BiOI, allowing the transfer of the photoexcited electrons from the photosensitizer to the conduction band of insulator (confirmed by charge difference distribution analysis and time-resolved fluorescence spectroscopy). The •O2- and •OH radicals are the main reactive species in photocatalytic NO oxidation. A reaction pathway study based on both in situ FT-IR and molecular-level simulation of NO adsorption and transformation indicates that this heterojunction can efficiently transform NO to harmless nitrate products via the NO → NO+ and NO2+ → nitrate or nitrite routes. This work provides numerous opportunities to explore earth-abundant insulators as visible-light-driven photocatalysts, and also offers a new mechanistic understanding of the role of gas-phase photocatalysis in controlling air pollution.

  14. Evaluation of nighttime imaging limits of visible near-infrared Earth observation platforms

    Science.gov (United States)

    Gartley, M.; Gerace, A.

    2012-06-01

    A subset of the existing NASA and NOAA families of Earth observation imaging platforms currently on orbit (Landsat 7, Advanced Land Imager (ALI), and the Defense Meteorological Satellite Program Operational Line Scanner) have a primary mission of imaging the Earth's landforms during the daylight hours. All three systems are capable of nighttime imaging operations, however this capability of Landsat and ALI is not frequently utilized due to lack of utility in the resulting data products. Many researchers have published science results on focused problems such as volcanic eruptions, wildfires, and urban settlement mapping. In this work we present a first-principles based radiometric framework for quantifying the capability of such imaging platforms for detecting the presence of boats in open waters taking into consideration the interaction between the boat and water surfaces. The low-level radiometric modeling is performed using both the DIRSIG software tool and MODTRAN, in conjunction with freely available boat geometric models, incandescent lamp spectra, and a randomly rough sea surface geometry. The resulting performance metric represents the minimum wattage of one or more incandescent illuminants that might be detected above the system noise floor for a variety of imaging geometries.

  15. Phytoplankton chlorophyll

    NARCIS (Netherlands)

    van de Poll, W.H.; Kulk, G.; Timmermans, K.R.; Brussaard, C.P.D.; van der Woerd, H.J.; Kehoe, M.J.; Mojica, K.D.A.; Visser, R.J.W.; Rozema, P.D.; Buma, A.G.J.

    2013-01-01

    Relationships between sea surface temperature (SST, > 10 m) and vertical density stratification, nutrient concentrations, and phytoplankton biomass, composition, and chlorophyll a (Chl a) specific absorption were assessed in spring and summer from latitudes 29 to 63 degrees N in the northeast

  16. An Earth-Moon Transfer Trajectory Design and Analysis Considering Spacecraft’s Visibility from Daejeon Ground Station at TLI and LOI Maneuvers

    Directory of Open Access Journals (Sweden)

    Jin Woo

    2010-09-01

    Full Text Available The optimal Earth-Moon transfer trajectory considering spacecraft’s visibility from the Daejeon ground station visibility at both the trans lunar injection (TLI and lunar orbit insertion (LOI maneuvers is designed. Both the TLI and LOI maneuvers are assumed to be impulsive thrust. As the successful execution of the TLI and LOI maneuvers are crucial factors among the various lunar mission parameters, it is necessary to design an optimal lunar transfer trajectory which guarantees the visibility from a specified ground station while executing these maneuvers. The optimal Earth-Moon transfer trajectory is simulated by modifying the Korean Lunar Mission Design Software using Impulsive high Thrust Engine (KLMDS-ITE which is developed in previous studies. Four different mission scenarios are established and simulated to analyze the effects of the spacecraft’s visibility considerations at the TLI and LOI maneuvers. As a result, it is found that the optimal Earth-Moon transfer trajectory, guaranteeing the spacecraft’s visibility from Daejeon ground station at both the TLI and LOI maneuvers, can be designed with slight changes in total amount of delta-Vs. About 1% difference is observed with the optimal trajectory when none of the visibility condition is guaranteed, and about 0.04% with the visibility condition is only guaranteed at the time of TLI maneuver. The spacecraft’s mass which can delivered to the Moon, when both visibility conditions are secured is shown to be about 534 kg with assumptions of KSLV-2’s on-orbit mass about 2.6 tons. To minimize total mission delta-Vs, it is strongly recommended that visibility conditions at both the TLI and LOI maneuvers should be simultaneously implemented to the trajectory optimization algorithm.

  17. Overview of NASA's MODIS and Visible Infrared Imaging Radiometer Suite (VIIRS) snow-cover Earth System Data Records

    Science.gov (United States)

    Riggs, George A.; Hall, Dorothy K.; Román, Miguel O.

    2017-10-01

    Knowledge of the distribution, extent, duration and timing of snowmelt is critical for characterizing the Earth's climate system and its changes. As a result, snow cover is one of the Global Climate Observing System (GCOS) essential climate variables (ECVs). Consistent, long-term datasets of snow cover are needed to study interannual variability and snow climatology. The NASA snow-cover datasets generated from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra and Aqua spacecraft and the Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) are NASA Earth System Data Records (ESDR). The objective of the snow-cover detection algorithms is to optimize the accuracy of mapping snow-cover extent (SCE) and to minimize snow-cover detection errors of omission and commission using automated, globally applied algorithms to produce SCE data products. Advancements in snow-cover mapping have been made with each of the four major reprocessings of the MODIS data record, which extends from 2000 to the present. MODIS Collection 6 (C6; https://nsidc.org/data/modis/data_summaries) and VIIRS Collection 1 (C1; https://doi.org/10.5067/VIIRS/VNP10.001) represent the state-of-the-art global snow-cover mapping algorithms and products for NASA Earth science. There were many revisions made in the C6 algorithms which improved snow-cover detection accuracy and information content of the data products. These improvements have also been incorporated into the NASA VIIRS snow-cover algorithms for C1. Both information content and usability were improved by including the Normalized Snow Difference Index (NDSI) and a quality assurance (QA) data array of algorithm processing flags in the data product, along with the SCE map. The increased data content allows flexibility in using the datasets for specific regions and end-user applications. Though there are important differences between the MODIS and VIIRS instruments (e.g., the VIIRS 375

  18. Overview of NASA's MODIS and Visible Infrared Imaging Radiometer Suite (VIIRS snow-cover Earth System Data Records

    Directory of Open Access Journals (Sweden)

    G. A. Riggs

    2017-10-01

    Full Text Available Knowledge of the distribution, extent, duration and timing of snowmelt is critical for characterizing the Earth's climate system and its changes. As a result, snow cover is one of the Global Climate Observing System (GCOS essential climate variables (ECVs. Consistent, long-term datasets of snow cover are needed to study interannual variability and snow climatology. The NASA snow-cover datasets generated from the Moderate Resolution Imaging Spectroradiometer (MODIS on the Terra and Aqua spacecraft and the Suomi National Polar-orbiting Partnership (S-NPP Visible Infrared Imaging Radiometer Suite (VIIRS are NASA Earth System Data Records (ESDR. The objective of the snow-cover detection algorithms is to optimize the accuracy of mapping snow-cover extent (SCE and to minimize snow-cover detection errors of omission and commission using automated, globally applied algorithms to produce SCE data products. Advancements in snow-cover mapping have been made with each of the four major reprocessings of the MODIS data record, which extends from 2000 to the present. MODIS Collection 6 (C6; https://nsidc.org/data/modis/data_summaries and VIIRS Collection 1 (C1; https://doi.org/10.5067/VIIRS/VNP10.001 represent the state-of-the-art global snow-cover mapping algorithms and products for NASA Earth science. There were many revisions made in the C6 algorithms which improved snow-cover detection accuracy and information content of the data products. These improvements have also been incorporated into the NASA VIIRS snow-cover algorithms for C1. Both information content and usability were improved by including the Normalized Snow Difference Index (NDSI and a quality assurance (QA data array of algorithm processing flags in the data product, along with the SCE map. The increased data content allows flexibility in using the datasets for specific regions and end-user applications. Though there are important differences between the MODIS and VIIRS instruments (e

  19. Fast and simultaneously determination of light and heavy rare earth elements in monazite using combination of ultraviolet-visible spectrophotometry and multivariate analysis

    Science.gov (United States)

    Anggraeni, Anni; Arianto, Fernando; Mutalib, Abdul; Pratomo, Uji; Bahti, Husein H.

    2017-05-01

    Rare Earth Elements (REE) are elements that a lot of function for life, such as metallurgy, optical devices, and manufacture of electronic devices. Sources of REE is present in the mineral, in which each element has similar properties. Currently, to determining the content of REE is used instruments such as ICP-OES, ICP-MS, XRF, and HPLC. But in each instruments, there are still have some weaknesses. Therefore we need an alternative analytical method for the determination of rare earth metal content, one of them is by a combination of UV-Visible spectrophotometry and multivariate analysis, including Principal Component Analysis (PCA), Principal Component Regression (PCR), and Partial Least Square Regression (PLS). The purpose of this experiment is to determine the content of light and medium rare earth elements in the mineral monazite without chemical separation by using a combination of multivariate analysis and UV-Visible spectrophotometric methods. Training set created 22 variations of concentration and absorbance was measured using a UV-Vis spectrophotometer, then the data is processed by PCA, PCR, and PLSR. The results were compared and validated to obtain the mathematical equation with the smallest percent error. From this experiment, mathematical equation used PLS methods was better than PCR after validated, which has RMSE value for La, Ce, Pr, Nd, Gd, Sm, Eu, and Tb respectively 0.095; 0.573; 0.538; 0.440; 3.387; 1.240; 1.870; and 0.639.

  20. Thematic mapper research in the earth sciences: Small scale patches of suspended matter and phytoplankton in the Elbe River Estuary, German Bight and Tidal Flats

    Science.gov (United States)

    Grassl, H.; Doerffer, R.; Fischer, J.; Brockmann, C.; Stoessel, M.

    1987-01-01

    A Thematic Mapper (TM) field experiment was followed by a data analysis to determine TM capabilities for analysis of suspended matter and phytoplankton. Factor analysis showed that suspended matter concentration, atmospheric scattering, and sea surface temperature can be retrieved as independent factors which determine the variation in the TM data over water areas. Spectral channels in the near infrared open the possibility of determining the Angstrom exponent better than for the coastal zone color scanner. The suspended matter distribution may then be calculated by the absolute radiance of channel 2 or 3 or the ratio of both. There is no indication of whether separation of chlorophyll is possible. The distribution of suspended matter and sea surface temperature can be observed with the expected fine structure. A good correlation between water depth and suspended matter distribution as found from ship data can now be analyzed for an entire area by the synoptic view of the TM scenes.

  1. Earth

    CERN Document Server

    Carter, Jason

    2017-01-01

    This curriculum-based, easy-to-follow book teaches young readers about Earth as one of the eight planets in our solar system in astronomical terms. With accessible text, it provides the fundamental information any student needs to begin their studies in astronomy, such as how Earth spins and revolves around the Sun, why it's uniquely suitable for life, its physical features, atmosphere, biosphere, moon, its past, future, and more. To enhance the learning experience, many of the images come directly from NASA. This straightforward title offers the fundamental information any student needs to sp

  2. 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.

  3. 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.

  4. 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…

  5. 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.

  6. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. 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 connect...

  8. Continuous cultures of phytoplankton

    National Research Council Canada - National Science Library

    Baron, Ron; Davie, Alexander; Gaines, Alec; Grant, Darren; Okay, Oya; Ozsoy, Emin

    2014-01-01

    The development of cultures of phytoplankton adapting throughout several days in an axenic, continuous-flow chemostat to yield a steady kinetic state of competing species is described mathematically...

  9. Phytoplankton diversity, biomass, and production

    Digital Repository Service at National Institute of Oceanography (India)

    Madondkar, S.G.P.; Gomes, H.; Parab, S.G.; Pednekar, S.; Goes, J.I.

    -Z system is also subjected to human influence through alterations in catchment area and ore mining activities, and the consequent land runoff. These aspects had prompted us to examine changes in phytoplankton diversity during last two decades. Phytoplankton...

  10. Enhanced visible-light photocatalytic H2 production by Znx Cd1-x S modified with earth-abundant nickel-based cocatalysts.

    Science.gov (United States)

    Ran, Jingrun; Zhang, Jun; Yu, Jiaguo; Qiao, Shi Zhang

    2014-12-01

    The application of various earth-abundant Ni species, such as NiS, Ni, Ni(OH)2 , and NiO, as a co-catalyst in a Znx Cd1-x S system for visible-light photocatalytic H2 production was investigated for the first time. The loading of Ni or NiS enhanced the photocatalytic activity of Znx Cd1-x S because they could promote the electron transfer at the interface with Znx Cd1-x S and catalyze the H2 evolution. Surprisingly, Ni(OH)2 -loaded Znx Cd1-x S exhibits a very high photocatalytic H2 -production rate of 7160 μmol h(-1)  g(-1) with a quantum efficiency of 29.5 % at 420 nm, which represents one of the most efficient metal sulfide photocatalysts without a Pt co-catalyst to date. This outstanding activity arises from the pronounced synergetic effect between Ni(OH)2 and metallic Ni formed in situ during the photocatalytic reaction. However, the loading of NiO deactivated the activity of Znx Cd1-x S because of their unmatched conduction band positions. This paper reports the optimization of the Znx Cd1-x S system by selecting an appropriate Ni-based co-catalyst, Ni(OH)2 , from a series of Ni species to achieve the highest photocatalytic H2 -production activity for the first time and also reveals the roles of these Ni species in the photocatalytic activity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Visible light responsive sulfated rare earth doped TiO(2)@fumed SiO(2) composites with mesoporosity: enhanced photocatalytic activity for methyl orange degradation.

    Science.gov (United States)

    Zhan, Changchao; Chen, Feng; Yang, Jintao; Dai, Daoxing; Cao, Xiaohua; Zhong, Mingqiang

    2014-02-28

    Visible light (VL) responsive mesoporous sulfated rare earth ions (Nd(3+), La(3+), Y(3+)) incorporated TiO2@fumed SiO2 photocatalysts were prepared by sol-gel method with P123 (EO20PO70EO20) as a template. The resultant samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption measurements (BET), UV-vis diffuse reflectance spectroscopy, photoluminescence (PL) spectra, Fourier transform infrared spectroscopy (FTIR) and thermal analyses (TG-DTA). In comparison with nondoped sample, RE-doped samples showed not only an increase in the surface areas and pore volumes, but also an inhibition of titania phase transition from anatase to rutile. Photo-degradation results revealed that RE-doped samples could greatly improve the photocatalytic activity, and the experimental degradation rates of methyl orange (MO) were higher than that catalyzed by undoped samples and Degussa P-25, obeyed the order of Nd(3+)>La(3+)>Y(3+). Nd-doped sample expressed the highest photoactivity and the optimal dosage was 0.25mol%, which resulted in MO degradation rates of 99.8% and 90.05% irradiation under UV for 60min and VL (λ>400nm) for 40h, respectively. The enhanced photocatalytic activity could be attributed to the higher specific area, good crystallinity, strong VL absorption and effective separation of photogenerated electron-hole pairs in the catalyst. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Studies on Antarctic phytoplankton

    Digital Repository Service at National Institute of Oceanography (India)

    Pant, A.

    Ice-edge data from a single polynya station at 70 degrees S 11 degrees E over a 2-month period is assessed in relation to previously published work in similar environments. The phytoplankton community seems to be composed of 2 quite different...

  13. Small Submersible Robust Microflow Cytometer for Quantitative Detection of Phytoplankton Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Marine phytoplankton are critical in sustaining life on Earth. They are key drivers of the global biogeochemical cycles of carbon and other nutrients, and account...

  14. Global biodiversity patterns of marine phytoplankton and zooplankton

    NARCIS (Netherlands)

    Huisman, J.; Irigoien, X.; Harris, R.P.

    2004-01-01

    Although the oceans cover 70% of the Earth's surface, our knowledge of biodiversity patterns in marine phytoplankton and zooplankton is very limited compared to that of the biodiversity of plants and herbivores in the terrestrial world. Here, we present biodiversity data for marine plankton

  15. Phytoplankton Identification Manual

    Digital Repository Service at National Institute of Oceanography (India)

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

    filtered through any plankton net is essential for the estimation of the standing crop. The volume of water traversed by the net is determined as an approximate value by the formula v = r2d? . Where, V, volume of the water filtered by the net; r, radius.... Number of calibrated ocular micrometer divisions multiplied by the corresponding calibrated value would 20 9. Measurement of Biomass Assessment of standing crop of phytoplankton in different periods is essential for any environment as the level...

  16. Monitoring natural phytoplankton communities

    DEFF Research Database (Denmark)

    Haraguchi, L.; Jakobsen, H. H.; Lundholm, Nina

    2017-01-01

    The phytoplankton community can vary within hours (physiology) to years (climatic and anthropogenic responses), and monitoring at different timescales is relevant for understanding community functioning and assessing changes. However, standard techniques used in monitoring programmes are time...... carbon biomass with PFCM, applying the same conversion factors as for microscopy. Biomasses obtained with PFCM, estimated from live cells, were higher than microscopy for natural samples. We conclude that PFCM results are comparable to classical techniques, yet the data from PFCM had poor taxonomic...

  17. PHYTOPLANKTON OF CASPIAN

    Directory of Open Access Journals (Sweden)

    Aysha Sharapatinovna Gasanova

    2015-01-01

    Full Text Available Aim. The composition of the species of the phytoplankton in the Russian sector of the Caspian Sea in conditions of transgression, anthropogenic and chemical contamination has been studied.Location.The Russian sector of the Caspian SeaMethods. The phytoplankton samples were collected at the depths of 8 – 50m by the use of the Nansen bathometer and subsequently were fixed in 4% formalin. The office processing was carried out in a box of Nozhotta type, which has the volume of 0.1 ml and the triplicate surface, under the light microscope of Biolam P15. The system of domestic diamotologists was used during the classification of Bacillariaphyta, as for the classification of Dinophyta, the Dodge scheme was applied. Cyanophyta algae were classified according to the system of A.A. Elenkina with the amendments adopted by A.I. Proshkin-Lavrenko and V.V. Makarova. The classification of the Chlorophyta division has been done according to the Smith system.Results, main conclusions. Presented the taxonomic structure and the lists of species of the phytoplankton community in the sea coastal shallow waters Russian sector of the Caspian Sea have been presented. A high floristic diversity and domination of small cell forms are characteristics of the modern structure of the coastal shoal waters of the Dagestan part of the Caspian Sea. The auttaclimatizant of 1934, Pseudosolenia calcaravis, has not been discovered in the plankton of the researched water area. The phytoplankton community has been represented by 58 species of six groups: Cyanophyta, Bacillariaphyta, Dinophyta, Euglenophyta, Chlorophyta and the small flagellate. Bacillariaphyta were the basis of both the taxonomic diversity and the biomass. Cyanophita prevailed in number.

  18. Effects of a coastal power plant thermal discharge on phytoplankton community structure in Zhanjiang Bay, China.

    Science.gov (United States)

    Li, Xue-Ying; Li, Bin; Sun, Xing-Li

    2014-04-15

    The effects of a thermal discharge from a coastal power plant on phytoplankton were determined in Zhanjiang Bay. Monthly cruises were undertaken at four tide times during April-October 2011. There were significant differences for dominant species among seven sampling months and four sampling tides. Species diversity (H') and Evenness showed a distinct increasing gradient from the heated water source to the control zone and fluctuated during four tides with no visible patterns. Species richness, cell count and Chl a at mixed and control zones were significantly higher than heated zones, and showed tidal changes with no obvious patterns. The threshold temperature of phytoplankton species can be regarded as that of phytoplankton community at ebb slack. The average threshold temperature over phytoplankton species, cell count and Chl a, and the threshold temperature of cell count can be regarded as that of phytoplankton community at flood slack during spring and neap respectively. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Phytoplankton Bloom Off Portugal

    Science.gov (United States)

    2002-01-01

    Turquoise and greenish swirls marked the presence of a large phytoplankton bloom off the coast of Portugal on April 23, 2002. This true-color image was acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra satellite. There are also several fires burning in northwest Spain, near the port city of A Coruna. Please note that the high-resolution scene provided here is 500 meters per pixel. For a copy of this scene at the sensor's fullest resolution, visit the MODIS Rapidfire site.

  20. Modelling Phytoplankton Dynamics in Estuaries

    NARCIS (Netherlands)

    Liu, B.

    2017-01-01

    In estuaries, which are the transition areas between rivers and coastal waters, the spatial and temporal distribution of phytoplankton cell number density (P) is determined by local specific growth and loss, advection by currents, mixing by turbulence, and sinking if the density of phytoplankton is

  1. Climate Change Effects on Iron Availability to Arctic Phytoplankton

    Science.gov (United States)

    Maldonado, Maria Teresa; Li, Jingxuan; Semeniuk, David; Schuback, Nina; Hoppe, Clara; AWI/UBC Collaboration

    2016-09-01

    Phytoplankton, unicellular algae, are responsible for 50% of earth's photosynthesis, and for a significant consumption of atmospheric CO2. Iron (Fe) is essential for phytoplankton, but is extremely depleted in seawater, limiting photosynthesis in 30% of the global ocean. Oceanic Fe bioavailability is determined by physical and chemical processes. The Arctic Ocean is experiencing the greatest decrease in seawater pH (termed ocean acidification). Simultaneously, ice retreat is promoting higher light intensity in Arctic Ocean. We investigated the effects of ocean acidification and high light on Fe availability to Arctic phytoplankton. Iron uptake rates by plankton, using the radionuclide 55Fe, were used as a proxy for Fe bioavailability. In an Arctic summer research cruise, we measured Fe uptake by two phytoplankton populations subjected to two light levels, as well as present CO2 levels (400ppm) or those expected by 2100 (1100 ppm). Our results demonstrated that high CO2 decreases Fe availability, while high light increases it, suggesting that future Fe bioavailability might be similar to present day. However, the detrimental effects of high CO2 were more pronounced in the plankton population exposed to higher seawater temperature. Future studies should investigate the interaction among light, CO2 and temperature on the Fe physiology of Arctic phytoplankton.

  2. 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.

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

    Directory of Open Access Journals (Sweden)

    Tracy J Mincer

    Full Text Available 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.

  4. 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

  5. Novel applications of diagnostic x-rays in activating photo-agents through x-ray induced visible luminescence from rare-earth particles: an in vitro study

    Science.gov (United States)

    Abliz, Erkinay; Collins, Joshua E.; Friedberg, Joseph S.; Kumar, Ajith; Bell, Howard; Waynant, Ronald W.; Tata, Darrell B.

    2010-02-01

    Photodynamic agents such as Photofrin II (Photo II) utilized in photodynamic therapy (PDT) possess a remarkable property to become preferentially retained within the tumor's micro-environment. Upon the photo-agent's activation through visible light photon absorption, the agents exert their cellular cytotoxicity through type II and type I mechanistic pathways through extensive generation of reactive oxygen species (ROS): singlet oxygen 1O2, superoxide anion O2 -, and hydrogen peroxide H2O2, within the intratumoral environment. Unfortunately, due to shallow visible light penetration depth (~2mm to 5mm) in tissues, the PDT strategy currently has largely been restricted to the treatments of surface tumors, such as the melanomas. Additional invasive strategies through optical fibers are currently utilized in getting the visible light into the intended deep seated targets within the body for PDT. In this communication, we report on a novel strategy in utilizing "soft" energy diagnostic X-rays to indirectly activate Photo II through X-ray induced luminescence from Gadolinium oxysulfide (20 micron dimension) particles doped with Terbium: Gd2O2S:Tb. X-ray induced visible luminescence from Gd2O2S:Tb particles was spectroscopically characterized and the ROS production levels from clinically relevant concentration (10 μg/ml) of Photo II was quantified through changes in the Vitamin C absorbance. ROS kinetics through X-ray induced luminescence was found to be similar to the ROS kinetics from red He-Ne laser exposures used in the clinics. Taken together, in-vitro findings herein provide the basis for future studies in determining the safety and efficacy of this non-invasive X-ray induced luminescence strategy in activating photo-agent in deep seated tumors.

  6. SYKE Proficiency Test 10/2014 Phytoplankton

    OpenAIRE

    Vuorio, Kristiina; Björklöf, Katarina; Kuosa, Harri; Jokipii, Reija; Järvinen, Marko; Lehtinen, Sirpa; Leivuori, Mirja; Niemelä, Maija; Väisänen, 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...

  7. Physiological responses of coastal phytoplankton (Visakhapatnam, SW Bay of Bengal, India) to experimental copper addition.

    Science.gov (United States)

    Biswas, Haimanti; Bandyopadhyay, Debasmita

    2017-10-01

    Trace amount of copper (Cu) is essential for many physiological processes; however, it can be potentially toxic at elevated levels. The impact of variable Cu concentrations on a coastal phytoplankton community was investigated along a coastal transect in SW Bay of Bengal. A small increase in Cu supply enhanced the concentrations of particulate organic carbon, particulate organic nitrogen, biogenic silica, total pigment, phytoplankton cell and total bacterial count. At elevated Cu levels all these parameters were adversely affected. δ 13 C POM and δ 15 N POC reflected a visible signature of both beneficial and toxic impacts of Cu supply. Skeletonema costatum, the dominant diatom species, showed higher tolerance to increasing Cu levels relative to Chaetoceros sp. Cyanobacteria showed greater sensitivity to copper than diatoms. The magnitude of Cu toxicity on the phytoplankton communities was inversely related to the distance from the coast. Co-enrichment of iron alleviated Cu toxicity to phytoplankton. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Longtime variation of phytoplankton in the South China Sea from the perspective of carbon fixation

    Science.gov (United States)

    Li, Teng; Bai, Yan; Chen, Xiaoyan; Zhu, Qiankun; Gong, Fang; Wang, Difeng

    2017-10-01

    The ocean is a huge carbon pool in the earth, and about half of the anthropogenic emissions of carbon dioxide are absorbed by the ocean each year. By converting inorganic carbon into organic carbon, the photosynthesis process of phytoplankton affords an important way for carbon sequestration in the ocean. According to previous researches, primary production (NPP) and the structure of phytoplankton community are important in regulate the efficiency of biological carbon pump. This study examined the spatiotemporal variability of satellite remote sensing derived chlorophyll a concentration (Chla), phytoplankton carbon biomass (Carbon), composition ratio of micro-, nano- and pico- phytoplankton, NPP and integrated particulate organic carbon (IPOC) during 1998-2007 in the South China Sea (SCS). Micro-, nano-phytoplankton and NPP showed similar seasonal variation with highest values in winter (January) (especially in the western ocean of Luzon Strait) and lowest values in summer (July) in SCS. Chla, phytoplankton carbon biomass, and IPOC showed different seasonal trends with one peak values occurred in winter and lowest in spring. Two sampling areas (A, N:17-21°, E:117.5-120° and B, N:12.5-15°, E:112-119°) in SCS were selected based on spatial distribution of the standard deviation of research parameters mentioned above. Compared to Chla, phytoplankton carbon biomass, NPP and IPOC, the interannual changes of phytoplankton community structure were remarkable in the two areas. The fraction of micro- and nano- phytoplankton in SCS tend to rise when La Nina events occur. Our results contribute to an understanding of the response of phytoplankton to climate change in the marginal sea. To quantify the efficiency of biological carbon pump in this area, more attention should be paid to the development of remote sensing algorithms of export NPP (or POC export flux) as well as the regulate mechanism of export NPP.

  9. 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.

  10. 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.

  11. DNA Analyses of Phytoplankton in the Southern Ocean

    Science.gov (United States)

    Xu, Y.; Gonzalez, M. F.; Bench, S.

    2014-12-01

    The Western Antarctic Peninsula (WAP) is experiencing the fastest climate warming of any marine environment on Earth, with a 6°C rise in mean winter temperature over the past 60 years (Vaughan et al., 2003). Though poorly understood, these changes may have profound effects on local Antarctic ecosystems. This research project aims to identify these changes through the compositional analysis of Antarctic phytoplankton using DNA sequencing supported by fluorescent microscopy. During the 2013 and 2014 blooming seasons, December to March, water samples were obtained from Palmer Station (located on the WAP) and filtered through 3 μm/0.8 μm filters. DNA was extracted from the water samples using the Qiagen Plant Kit, quantified through use of both Nanodrop and Picogreen technology, quality-checked by gel electrophoresis, and sent to be sequenced. Additionally, major phytoplankton species were identified through microscope imaging and preliminary counts were made for four important dates, two located at the peaks of phytoplankton blooms. From these four samples alone, it appeared that cryptomonads dominated the primary bloom whereas diatoms, both centric and pennate, were more abundant during the second bloom. In the future, these results will be tested against sequencing data. Through continued year-by-year analysis of Antarctic phytoplankton abundance levels, it will be possible to identify trends that may be crucial to understanding the dynamic Antarctic ecosystem.

  12. 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.

  13. Visibility Matters

    DEFF Research Database (Denmark)

    Wildgaard, Lorna Elizabeth

    2015-01-01

    Research production, which earns universities money, is accredited publications in peer-reviewed journals and books. Increasing research productivity is one policy amongst many used by management to boost growth and income. It is time for a pat on the back, the growth of knowledge and visibility...

  14. Control of the visible emission in the SrZrO3 nano-crystals with the rare earth ion doping.

    Science.gov (United States)

    Kim, Dong Hwan; Kim, Ji Hyun; Chung, Jin Seok; Lee, Yunsang

    2013-11-01

    We investigated the emission property of SrZrO3 nano-crystals (NCs) with the doping of rare earth (RE) ions, Eu3+ and Tm3+, by using 325 nm photo-excitation. SrZrO3 NCs show a sizable violet-blue emission, while the Eu3+ and Tm3+ ions are well known to be good red and blue phosphors, respectively. Combined emissions of the host and the RE ion dopant might suggest a new white luminescent source. The RE ion doped SrZrO3 NCs were initially synthesized by using the combustion method, and then the as-synthesized crystals were annealed at different temperatures from 650 degrees C to 1450 degrees C. The Eu3+-doped SrZrO3 NCs showed the sharp red emission near 600 nm, in addition to a violet-blue emission of the host material in itself. While the red emission is enhanced in the high temperature post-annealing, the blue emission is suppressed in an opposite way. This close relation between the emissions of the host and dopant was observed similarly in the Tm3+-doped NCs. We could control the emission property in the SrZrO3:Eu3+/Tm3+ NCs from blue to red by thermal annealing and RE ion doping.

  15. Physical forcing and phytoplankton distributions

    Directory of Open Access Journals (Sweden)

    Trevor Platt

    2005-06-01

    Full Text Available At the global and regional scales, the distribution and abundance of marine phytoplankton are under the control of physical forcing. Moreover, the community structure and the size structure of phytoplankton assemblages also appear to be under physical control. Areas of the ocean with common physical forcing (ecological provinces may be expected to have phytoplankton communities that respond in a similar fashion to changes in local forcing, and with ecophysiological rate parameters that are predictable from local environmental conditions. In modelling the marine ecosystem, relevant parameters may be assigned according to a partition into ecological provinces. To the extent that physical forcing of the ocean is not constant within or between years, the boundaries of the provinces should be considered as dynamic. The dynamics and the associated changes in taxa can be revealed by remote sensing.

  16. Calcifying phytoplankton biomass and CO2: A striking balance

    Science.gov (United States)

    Henderiks, Jorijntje; Hannisdal, Bjarte; Liow, Lee Hsiang

    2010-05-01

    Calcifying phytoplankton play a fundamental role in marine ecosystems and global biogeochemical cycles. Their cell size and abundance modulate the strength of the biological carbon and carbonate 'pumps', which represent important feedbacks in the Earth System. Phytoplankton biomass is thus coupled to climate variability, but the behavior of this coupling on geological time scales remains unknown. We compared fossil time series of coccolithophore relative abundance and cell size to geochemical proxy records of global climate change over much of the Cenozoic (~45-5 million years ago). We show that the Cenozoic decline in atmospheric carbon dioxide levels (pCO2) caused a reduction in calcifying phytoplankton biomass. Our results demonstrate that long-term variation in CO2 availability and concomitant shifts in ocean carbonate chemistry have been important drivers of planktonic ecosystems beyond their association with ocean temperature and stratification. This supports the hypothesis that large-celled coccolithophores lacking a carbon concentrating mechanism were disadvantaged in a low-pCO2 world (Henderiks & Pagani 2008). In addition, decreasing biomass of calcifying phytoplankton may have represented a negative feedback during global cooling by reducing carbon drawdown and burial fluxes, potentially contributing to the stabilization of atmospheric CO2 concentrations over the past 24 million years (Pagani et al. 2009). References Henderiks, J. and M. Pagani (2008), Coccolithophore cell size and the Paleogene decline in atmospheric CO2, Earth and Planetary Science Letters, 269, 575-583. Pagani, M., K. Caldeira, R. Berner and D. J. Beerling (2009), The role of terrestrial plants in limiting atmospheric CO2 decline over the past 24 million years, Nature, 460, 85-88.

  17. 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......-replete and nutrient-depleted cells. The field data suggest that the absorption ratio may be a useful indicator of nutritional status of natural phytoplankton populations, and can be used to augment the interpretation of other data....

  18. 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.; hide

    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

  19. Preliminary census of zooplanktons and phytoplanktons community ...

    African Journals Online (AJOL)

    The zooplankton and phytoplankton community of Ajeko Stream, North Central Nigeria were assessed between October and December 2010. Prior to sampling, Temperature, Transparency, Dissolve Oxygen and pH were evaluated. Zooplankton and phytoplanktons were sampled using plankton net of 20μm diameter with a ...

  20. Phytoplankton assemblage and environmental variables in Ogun ...

    African Journals Online (AJOL)

    The distribution and composition of estuarine phytoplankton species provide prerequisite to the understanding of the dynamics of aquatic ecosystem and its diagnostic assessment. The present study was on the relationship between phytoplankton assemblage and environmental variables. It was carried out between ...

  1. Using of phytoplankton and physicochemical parameters as ...

    African Journals Online (AJOL)

    Samples were collected from six sites covering the lake Timsah during the period summer 2005-spring 2006, representing the four seasons, including water and phytoplankton samples, in order to evaluating phytoplankton algal community and physicochemical parameters. A total of One-hundard and two taxa have been ...

  2. Thermal Thresholds of Phytoplankton Growth in Polar Waters and Their Consequences for a Warming Polar Ocean

    KAUST Repository

    Coello-Camba, Alexandra

    2017-06-02

    Polar areas are experiencing the steepest warming rates on Earth, a trend expected to continue in the future. In these habitats, phytoplankton communities constitute the basis of the food web and their thermal tolerance may dictate how warming affects these delicate environments. Here, we compiled available data on thermal responses of phytoplankton growth in polar waters. We assembled 53 growth-vs.-temperature curves (25 from the Arctic, 28 from the Southern oceans), indicating the limited information available for these ecosystems. Half of the data from Arctic phytoplankton came from natural communities where low ambient concentrations could limit growth rates. Phytoplankton from polar waters grew faster under small temperature increases until reaching an optimum (TOPT), and slowed when temperatures increased beyond this value. This left-skewed curves were characterized by higher activation energies (Ea) for phytoplankton growth above than below the TOPT. Combining these thermal responses we obtained a community TOPT of 6.5°C (±0.2) and 5.2°C (±0.1) for Arctic and Southern Ocean phytoplankton communities, respectively. These threshold temperatures were already exceeded at 70°N during the first half of August 2013, evidenced by sea surface temperatures (SSTs, satellite data, http://www.ncdc.noaa.gov). We forecasted SSTs for the end of the twenty-first century by assuming an overall 3°C increase, equivalent to a low emission scenario. Our forecasts show that SSTs at 70°N are expected to exceed TOPT during summer by 2100, and during the first half of August at 75°N. While recent Arctic spring temperatures average 0.5°C and −0.7°C at 70°N and 75°N, respectively, they could increase to 2.8°C at 70°N and 2.2°C at 75°N as we approach 2100. Such temperature increases could lead to intense phytoplankton blooms, shortened by fast nutrient consumption. As SSTs increase, thermal thresholds for phytoplankton growth would be eventually exceeded during bloom

  3. Interannual Variation in Phytoplankton Class-specific Primary Production at a Global Scale

    Science.gov (United States)

    Rousseaux, Cecile; Gregg, Watson

    2014-01-01

    Phytoplankton is responsible for over half of the net primary production on earth. The knowledge on the contribution of various phytoplankton groups to the total primary production is still poorly understood. Data from satellite observations suggest that for upwelling regions, photosynthetic rates by microplankton is higher than that of nanoplankton but that when the spatial extent is considered, the production by nanoplankton is comparable or even larger than microplankton. Here, we used the NASA Ocean Biogeochemical Model (NOBM) combined with remote sensing data via assimilation to evaluate the contribution of 4 phytoplankton groups to the total primary production. Globally, diatoms were the group that contributed the most to the total phytoplankton production (approx. 50%) followed by coccolithophores and chlorophytes. Primary production by diatoms was highest in high latitude (>45 deg) and in major upwelling systems (Equatorial Pacific and Benguela system). We assessed the effects of climate variability on the class-specific primary production using global (i.e. Multivariate El Nino Index, MEI) and 'regional' climate indices (e.g. Southern Annular Mode (SAM), Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO)). Most interannual variability occurred in the Equatorial Pacific and was associated with climate variability. These results provide a modeling and data assimilation perspective to phytoplankton partitioning of primary production and contribute to our understanding of the dynamics of the carbon cycle in the oceans at a global scale.

  4. Carbon Concentrating Mechanisms & C4 Enzymes In Marine Phytoplankton

    Science.gov (United States)

    Moolna, A.; Hermoso, M.; Rickaby, R.

    2009-12-01

    Photosynthetic CO2 assimilation by marine phytoplankton is a major sink in the Earth’s carbon cycle. Understanding the molecular biogeochemistry of this carbon capture is crucial to predicting how the Earth will respond to the carbon emissions driving human-induced climate change. We are investigating the connection of phytoplankton photosynthesis to different CO2 levels using the diatom Thalassiosira weissflogii and the coccolithophores Emiliania huxleyi and Gephyrocapsa oceanica. Phytoplankton in equilibrium with present-day atmospheric CO2 levels have carbon concentrating mechanisms (CCMs) that increase their internal concentration of dissolved inorganic carbon (DIC) relative to their surrounding seawater. By acclimating cultures to seawater with quadrupled DIC availability, the CCM physiology is relaxed. This is demonstrated by resuspending the phytoplankton in CO2-free seawater and then plotting the response curve of photosynthetic O2 evolution rate against the addition of specific concentrations of DIC (Figure 1). Relaxation implies less energy used for CCMs and so more energy may be available for carbon fixation. Scanning electron micrographs of high DIC G. oceanica cultures, for example, show that the size of both the coccosphere and of individual coccoliths is unchanged; but the external shield of the coccolith extends further into the central area. This suggests an increase in calcification, with implications for carbon partition between organic and inorganic fluxes to the seafloor. Of particular interest is the possibility that C4 photosynthesis could provide a CCM for marine phytoplankton. The carbon-fixing Rubisco enzyme can only use CO2 as a substrate but, due to reaction between CO2 and H2O, most of the CO2 dissolved in seawater is actually present as HCO3-. In C4 land plants, CO2 for Rubisco is provided via a four-carbon intermediate compound generated from HCO3-; and the basic C4 machinery is found in all photosynthetic life because of

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

    Science.gov (United States)

    Chakraborty, Subhendu; Tiwari, P K; Misra, A K; Chattopadhyay, J

    2015-06-01

    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-phytoplankton system with toxic effect on phytoplankton is investigated. We analyze the linear stability of the system and obtain the condition for Turing instability. In the presence of toxic effect, we find that the distribution of nutrient and phytoplankton becomes inhomogeneous in space and results in different patterns, like stripes, spots, and the mixture of them depending on the toxicity level. We also observe that the distribution of nutrient and phytoplankton shows spatiotemporal oscillation for certain toxicity level. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Massive phytoplankton blooms under Arctic sea ice.

    Science.gov (United States)

    Arrigo, Kevin R; Perovich, Donald K; Pickart, Robert S; Brown, Zachary W; van Dijken, Gert L; Lowry, Kate E; Mills, Matthew M; Palmer, Molly A; Balch, William M; Bahr, Frank; Bates, Nicholas R; Benitez-Nelson, Claudia; Bowler, Bruce; Brownlee, Emily; Ehn, Jens K; Frey, Karen E; Garley, Rebecca; Laney, Samuel R; Lubelczyk, Laura; Mathis, Jeremy; Matsuoka, Atsushi; Mitchell, B Greg; Moore, G W K; Ortega-Retuerta, Eva; Pal, Sharmila; Polashenski, Chris M; Reynolds, Rick A; Schieber, Brian; Sosik, Heidi M; Stephens, Michael; Swift, James H

    2012-06-15

    Phytoplankton blooms over Arctic Ocean continental shelves are thought to be restricted to waters free of sea ice. Here, we document a massive phytoplankton bloom beneath fully consolidated pack ice far from the ice edge in the Chukchi Sea, where light transmission has increased in recent decades because of thinning ice cover and proliferation of melt ponds. The bloom was characterized by high diatom biomass and rates of growth and primary production. Evidence suggests that under-ice phytoplankton blooms may be more widespread over nutrient-rich Arctic continental shelves and that satellite-based estimates of annual primary production in these waters may be underestimated by up to 10-fold.

  7. Horizon Detection In The Visible Spectrum

    Science.gov (United States)

    2016-09-01

    techniques can also recognize star patterns in star trackers for satellite attitude determination. Horizon detection in the visible spectrum was largely...analysis of visual imagery from low-earth orbit was conducted to develop a horizon brightness transition model, which allows for consistent and...vision techniques can also recognize star patterns in star trackers for satellite attitude determination. Horizon detection in the visible spectrum was

  8. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science. Vijaya. Articles written in Journal of Earth System Science. Volume 120 Issue 3 June 2011 pp 545-556. Fine-scale responses of phytoplankton to freshwater influx in a tropical monsoonal estuary following the onset of southwest monsoon · Suraksha M Pednekar S G Prabhu ...

  9. 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...

  10. Phytoplankton: quality indexes, functional groups and toxicity

    OpenAIRE

    Mariani, Maria Antonietta

    2008-01-01

    The primary scientific centre of my doctorate is phytoplankton, especially some specific aspects of its ecology. Phytoplankton, the plant component, constitutes together with phytobenthos and periphyton the photosynthetic entity of inland waters (Tonolli, 1964). In man-made lakes, because of the great variations in the water level, which can reach 10-15 meters in Sardinia (Sechi, 1986), the presence and importance of phytobenthos and periphyton is almost negligible, so that all th...

  11. Nearshore phytoplankton of Hammond Bay, Lake Huron

    Science.gov (United States)

    Brown, Charles L.; Manny, Bruce A.

    1983-01-01

    To predict the effects of increased nutrient loading on nearshore phytoplankton populations in northern Lake Huron, we collected phytoplankton from a small, nearshore water intake at Hammond Bay four times per week from August 1973 to July 1975. Phytoplankton density, taxonomic composition, and biomass in the nearshore waters followed predictable, seasonal fluctuations during each of two 12-month periods. The density of total phytoplankton was high (450600 cells/mL) in June and low (60 to 210 cells/mL) from January to April each year. The mean annual composition of the phytoplankton assemblage by number for the study period was 33% cryptomonads, 24% diatoms, 16% chrysophytes, 16% blue-green algae, and 10% green algae. Phytoplankton biomass was low through each year (range, 0.09 to 0.66 g/m3), resembling values previously reported from Lake Superior. Pennate diatoms contributed 60 to 80% of the total biomass from December to April and in July. Phytoflagellates consisting of chrysophytes and cryptomonads accounted for 35% of the biomass throughout the 2-year study.

  12. Phytoplankton Assessment in Danube Delta Biosphere Reserve

    Directory of Open Access Journals (Sweden)

    SPIRIDON Cosmin

    2016-12-01

    Full Text Available The term ”plankton” refers to those microscopic aquatic forms having little or no resistance to currents and living free-floating and suspended, in open or pelagic waters. Phytoplankton development has different consequences depending on biomass quality and quantity, the overgrowth result being eutrophication process. The eutrophication intensity can cause both a lower water transparency, by excessive algal growth, to fish death in the area. In this study, it was presented the ecological status and phytoplankton biomass dynamic, in the Danube branches from upstream to downstream. The measurements have been made in 2013, in March, June, September and November, using spectrofluorometer for algal biomass determination and a microscope for qualitative analyses of phytoplankton species. Shannon-Wiener index was calculated to compare phytoplankton species diversity. Also, the biodegradable organic matter loading the ecosystem was determined by computing the Saprobic index. The values obtained do not exceed the eutrophication limits according to the Water Framework Directive, transposed into Romanian legislation by Order 161/2006, with normal concentrations for rheophile ecosystems, as Danube's branches. In this area, water currents and high water turbidity inhibit phytoplankton growth, in contrast to lacustrine ecosystems, where light penetration to depths favors the development of different phytoplankton groups.

  13. Triclosan alterations of estuarine phytoplankton community structure.

    Science.gov (United States)

    Pinckney, James L; Thompson, Laura; Hylton, Sarah

    2017-06-15

    Antimicrobial additives in pharmaceutical and personal care products are a major environmental concern due to their potential ecological impacts on aquatic ecosystems. Triclosan (TCS) has been used as an antiseptic, disinfectant, and preservative in various media. The sublethal and lethal effects of TCS on estuarine phytoplankton community composition were investigated using bioassays of natural phytoplankton communities to measure phytoplankton responses to different concentrations of TCS ranging from 1 to 200μgl -1 . The EC 50 (the concentration of an inhibitor where the growth is reduced by half) for phytoplankton groups (diatoms, chlorophytes, cryptophytes) examined in this ranged from 10.7 to 113.8μg TCS l -1 . Exposures resulted in major shifts in phytoplankton community composition at concentrations as low as 1.0μg TCS l -1 . This study demonstrates estuarine ecosystem sensitivity to TCS exposure and highlights potential alterations in phytoplankton community composition at what are typically environmental concentrations of TCS in urbanized estuaries. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Visible Jovian Aurora

    Science.gov (United States)

    1997-01-01

    Jupiter's aurora on the night side of the planet is seen here at five different wavelengths. Jupiter's bright crescent, which is about half illuminated, is out of view to the right. North is at the top. The images are centered at 57 degrees north and 184 degrees West and were taken on April 2, 1997 at a range of 1.7 million kilometers (1.05 million miles) by the Solid State Imaging (SSI) camera system aboard NASA's Galileo spacecraft.Although Jupiter's aurora had been imaged from Earth in the ultraviolet and infrared, these are the first images at visible wavelengths, where most of the emission takes place. CLR stands for clear (no filter) and shows the integrated brightness at all wavelengths. The other panels show the violet, green, red, and 889 nanometer-wavelength filtered images. The brightness of the aurora is roughly independent of wavelength, at least at the spectral resolution obtainable with these filters.As on Earth, the aurora is caused by electrically charged particles striking the upper atmosphere, causing the molecules of the atmosphere to glow. The brightness in the different filters contains information about the energy of the impinging particles and the composition of the upper atmosphere. If atomic hydrogen were the only emitter, the light would be much stronger in the red filter, which is not consistent with the observed distribution.The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at: http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at: http:/ /www.jpl.nasa.gov/galileo/sepo.

  15. Brazilian scientific production on phytoplankton studies: national determinants and international comparisons

    Directory of Open Access Journals (Sweden)

    JC. Nabout

    Full Text Available In this study, we determined the temporal trends of publications by Brazilian authors on phytoplankton and compared these trends to those of other Latin American countries as well as to the 14 countries ranking ahead of Brazil in terms of scientific publication. To do this, we investigated phytoplankton studies published in an international database (Thomson-ISI. The data showed that Brazil plays an important role among other Latin American countries in the publication of these studies. Moreover, the trend of studies published on phytoplankton in Brazil was similar to trends recorded in the developed countries of the world. We conclude that studies can be more deliberately targeted to reduce national and international asymmetries by focusing on projects with large spatial scales and projects that concentrate on less-studied geographic regions, thus encouraging increased productivity in remote areas of the country. Associated with this is a necessary increase in high-impact journal publications, increasing the quantity and quality of Brazilian scientific studies on phytoplankton and, consequently, their global visibility.

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

    Science.gov (United States)

    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 found clear evidence of two independent physical drivers for phytoplankton abundance. The first one is the widely accepted phytoplankton blooming produced by the upwelling of cold, nutrient-rich deep ocean waters. The second, which explains the Bay of Bengal findings, is coastal phytoplankton blooming during high river discharges with terrestrial nutrients. Causal mechanisms should be understood when associating SST with phytoplankton and subsequent cholera outbreaks in regions where freshwater discharge are a predominant mechanism for phytoplankton production. PMID:21813852

  17. Challenges in modeling spatiotemporally varying phytoplankton blooms in the Northwestern Arabian Sea and Gulf of Oman

    OpenAIRE

    Sedigh Marvasti, S.; A. Gnanadesikan; A. A. Bidokhti; Dunne, J. P.; Ghader, S.

    2016-01-01

    Recent years have shown an increase in harmful algal blooms in the Northwest Arabian Sea and Gulf of Oman, raising the question of whether climate change will accelerate this trend. This has led us to examine whether the Earth System Models used to simulate phytoplankton productivity accurately capture bloom dynamics in this region – both in terms of the annual cycle and interannual variability. Satellite data (SeaWIFS ocean color) show two climatological blooms in this regi...

  18. Drivers of phytoplankton dynamics in old Tampa Bay, FL (USA), a subestuary lagging in ecosystem recovery

    Science.gov (United States)

    Corcoran, Alina A.; Wolny, Jennifer; Leone, Erin; Ivey, James; Murasko, Susan

    2017-02-01

    In the past four decades, consistent and coordinated management actions led to the recovery of Tampa Bay, FL (USA) - an estuary that was declared dead in the 1970s. An exception to this success story is Old Tampa Bay, the northernmost subestuary of the system. Compared to the other bay segments, Old Tampa Bay is characterized by poorer water quality and spring and summer blooms of cyanobacteria, picoplankton, diatoms, and the saxitoxin-producing dinoflagellate Pyrodinium bahamense. Together, these blooms contribute to light attenuation and lagging recovery of seagrass beds. Yet, studies of phytoplankton dynamics within Old Tampa Bay have been limited - both in number and in their spatiotemporal resolution. In this study, we used field sampling and continuous monitoring to (1) characterize temporal and spatial variability in phytoplankton biomass and community composition and (2) identify key drivers of the different phytoplankton blooms in Old Tampa Bay. Overall, temporal variability in phytoplankton biomass (using chlorophyll a as a proxy) and community composition surpassed spatial variability of these parameters. We found a base community of small diatoms and flagellates, as well as certain dinoflagellates, that persisted year round in the system. Seasonally, freshwater runoff stimulated phytoplankton growth, specifically that of chlorophytes, cyanobacteria and other dinoflagellates - consistent with predictions based on ecological theory. On shorter time scales, salinity, visibility, and freshwater inflows were important predictors of phytoplankton biomass. With respect to P. bahamense, environmental drivers including salinity, temperature and dissolved nutrient concentrations explained ∼24% of the variability in cell abundance, indicating missing explanatory parameters in our study for this taxon, such as cyst density and location of cyst beds. Spatially, we found differences in community trajectories across north-south and west-east gradients, with the

  19. Retrieval of phytoplankton cell size from chlorophyll a specific absorption and scattering spectra of phytoplankton.

    Science.gov (United States)

    Zhou, Wen; Wang, Guifen; Li, Cai; Xu, Zhantang; Cao, Wenxi; Shen, Fang

    2017-10-20

    Phytoplankton cell size is an important property that affects diverse ecological and biogeochemical processes, and analysis of the absorption and scattering spectra of phytoplankton can provide important information about phytoplankton size. In this study, an inversion method for extracting quantitative phytoplankton cell size data from these spectra was developed. This inversion method requires two inputs: chlorophyll a specific absorption and scattering spectra of phytoplankton. The average equivalent-volume spherical diameter (ESD v ) was calculated as the single size approximation for the log-normal particle size distribution (PSD) of the algal suspension. The performance of this method for retrieving cell size was assessed using the datasets from cultures of 12 phytoplankton species. The estimations of a(λ) and b(λ) for the phytoplankton population using ESD v had mean error values of 5.8%-6.9% and 7.0%-10.6%, respectively, compared to the a(λ) and b(λ) for the phytoplankton populations using the log-normal PSD. The estimated values of C i ESD v were in good agreement with the measurements, with r 2 =0.88 and relative root mean square error (NRMSE)=25.3%, and relatively good performances were also found for the retrieval of ESD v with r 2 =0.78 and NRMSE=23.9%.

  20. 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.)

  1. Visibly Pushdown Automata

    DEFF Research Database (Denmark)

    Srba, Jiri

    2006-01-01

    We investigate the possibility of (bi)simulation-like preorder/equivalence checking on the class of visibly pushdown automata and its natural subclasses visibly BPA (Basic Process Algebra) and visibly one-counter automata. We describe generic methods for proving complexity upper and lower bounds...... for a number of studied preorders and equivalences like simulation, completed simulation, ready simulation, 2-nested simulation preorders/equivalences and bisimulation equivalence. Our main results are that all the mentioned equivalences and preorders are EXPTIME-complete on visibly pushdown automata, PSPACE......-complete on visibly one-counter automata and P-complete on visibly BPA. Our PSPACE lower bound for visibly one-counter automata improves also the previously known DP-hardness results for ordinary one-counter automata and one-counter nets. Finally, we study regularity checking problems for visibly pushdown automata...

  2. Earth - Moon Conjunction

    Science.gov (United States)

    1992-01-01

    On December 16, 1992, 8 days after its encounter with Earth, the Galileo spacecraft looked back from a distance of about 6.2 million kilometers (3.9 million miles) to capture this remarkable view of the Moon in orbit about Earth. The composite photograph was constructed from images taken through visible (violet, red) and near-infrared (1.0-micron) filters. The Moon is in the foreground; its orbital path is from left to right. Brightly colored Earth contrasts strongly with the Moon, which reacts only about one-third as much sunlight as our world. To improve the visibility of both bodies, contrast and color have been computer enhanced. At the bottom of Earth's disk, Antarctica is visible through clouds. The Moon's far side can also be seen. The shadowy indentation in the Moon's dawn terminator--the boundary between its dark and lit sides--is the South Pole-Aitken Basin, one of the largest and oldest lunar impact features. This feature was studied extensively by Galileo during the first Earth flyby in December 1990.

  3. The Visibility Complex

    NARCIS (Netherlands)

    Pocchiola, Michel; Vegter, Gert

    1993-01-01

    We introduce the visibility complex of a collection O of n pairwise disjoint convex objects in the plane. This 2–dimensional cell complex may be considered as a generalization of the tangent visibility graph of O. Its space complexity k is proportional to the size of the tangent visibility graph. We

  4. 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

  5. Grazers and phytoplankton growth in the oceans: an experimental and evolutionary perspective.

    Science.gov (United States)

    Ratti, Simona; Knoll, Andrew H; Giordano, Mario

    2013-01-01

    The taxonomic composition of phytoplankton responsible for primary production on continental shelves has changed episodically through Earth history. Geological correlations suggest that major changes in phytoplankton composition correspond in time to changes in grazing and seawater chemistry. Testing hypotheses that arise from these correlations requires experimentation, and so we carried out a series of experiments in which selected phytoplankton species were grown in treatments that differed with respect to the presence or absence of grazers as well as seawater chemistry. Both protistan (Euplotes sp.) and microarthropod (Acartia tonsa) grazers changed the growth dynamics and biochemical composition of the green alga Tetraselmis suecica, the diatom Thalassiosira weissflogii, and the cyanobacterium Synechococcus sp., increasing the specific growth rate and palatability of the eukaryotic algae, while decreasing or leaving unchanged both parameters in the cyanobacteria. Synechococcus (especially) and Thalassiosira produced toxins effective against the copepod, but ciliate growth was unaffected. Acartia induced a 4-6 fold increase of Si cell quota in the diatom, but Euplotes had no similar effect. The differential growth responses of the eukaryotic algae and cyanobacteria to ciliate grazing may help to explain the apparently coeval radiation of eukaryophagic protists and rise of eukaryotes to ecological prominence as primary producers in Neoproterozoic oceans. The experimental results suggest that phytoplankton responses to the later radiation of microarthropod grazers were clade-specific, and included changes in growth dynamics, toxin synthesis, encystment, and (in diatoms) enhanced Si uptake.

  6. Grazers and phytoplankton growth in the oceans: an experimental and evolutionary perspective.

    Directory of Open Access Journals (Sweden)

    Simona Ratti

    Full Text Available The taxonomic composition of phytoplankton responsible for primary production on continental shelves has changed episodically through Earth history. Geological correlations suggest that major changes in phytoplankton composition correspond in time to changes in grazing and seawater chemistry. Testing hypotheses that arise from these correlations requires experimentation, and so we carried out a series of experiments in which selected phytoplankton species were grown in treatments that differed with respect to the presence or absence of grazers as well as seawater chemistry. Both protistan (Euplotes sp. and microarthropod (Acartia tonsa grazers changed the growth dynamics and biochemical composition of the green alga Tetraselmis suecica, the diatom Thalassiosira weissflogii, and the cyanobacterium Synechococcus sp., increasing the specific growth rate and palatability of the eukaryotic algae, while decreasing or leaving unchanged both parameters in the cyanobacteria. Synechococcus (especially and Thalassiosira produced toxins effective against the copepod, but ciliate growth was unaffected. Acartia induced a 4-6 fold increase of Si cell quota in the diatom, but Euplotes had no similar effect. The differential growth responses of the eukaryotic algae and cyanobacteria to ciliate grazing may help to explain the apparently coeval radiation of eukaryophagic protists and rise of eukaryotes to ecological prominence as primary producers in Neoproterozoic oceans. The experimental results suggest that phytoplankton responses to the later radiation of microarthropod grazers were clade-specific, and included changes in growth dynamics, toxin synthesis, encystment, and (in diatoms enhanced Si uptake.

  7. 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.

  8. Biomass relations between phytoplankton and zooplankton in Goa waters

    Digital Repository Service at National Institute of Oceanography (India)

    Pant, A.; Matondkar, S.G.P.; Goswami, S.C.

    Biomass of phytoplankton and zooplankton, measured as particulate oxidizable carbon, shows that at shallowest stations (5 m) there is large excess of phytoplankton organic carbon over zooplankton carbon in all the samples There is no significant...

  9. 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...

  10. Physico-Chemical Parameters and Phytoplankton Community of ...

    African Journals Online (AJOL)

    These were Bacilliariophyceae, Cyanophyceae and Chlorophyceae. The phytoplankton community was predominated by Cyanophyceae which constituted more than 40% of the total phytoplankton population. The predominant taxa were Spirulina sp., Lepocindis sp., Merimospedia sp., Anabena sp. and Coclastrum sp.

  11. Phytoplankton community and their impact on water quality: An ...

    African Journals Online (AJOL)

    Michael Horsfall

    eutrophic status. At the time of this study, the lake was not susceptible to generating algal blooms. @JASEM. Keywords: phytoplankton, water quality, biomass. Phytoplankton communities are sensitive to changes in their environment and therefore ...

  12. Observing and modelling phytoplankton community structure in the North Sea

    NARCIS (Netherlands)

    Ford, D.A.; van der Molen, J.; Hyder, K.; Bacon, J.; Barciela, R.; Creach, V.; McEwan, R.; Ruardij, P.; Forster, R.

    2017-01-01

    Phytoplankton form the base of the marine foodchain, and knowledge of phytoplankton community structureis fundamental when assessing marine biodiversity. Policymakers and other users require information on marinebiodiversity and other aspects of the marine environmentfor the North Sea, a highly

  13. Phytoplankton as Particles - A New Approach to Modeling Algal Blooms

    Science.gov (United States)

    2013-07-01

    ER D C/ EL T R -1 3 -1 3 Civil Works Basic Research Program Phytoplankton as Particles – A New Approach to Modeling Algal Blooms E nv... Phytoplankton as Particles – A New Approach to Modeling Algal Blooms Carl F. Cerco and Mark R. Noel Environmental Laboratory U.S. Army Engineer Research... phytoplankton blooms can be modeled by treating phytoplankton as discrete particles capable of self- induced transport via buoyancy regulation or other

  14. A flexible multivariable model for phytoplankton growth.

    Science.gov (United States)

    Tabatabai, Mohammad A; Eby, Wayne M; Bae, Sejong; Singh, Karan P

    2013-06-01

    We introduce a new multivariable model to be used to study the growth dynamics of phytoplankton as a function of both time and the concentration of nutrients. This model is applied to a set of experimental data which describes the rate of growth as a function of these two variables. The form of the model allows easy extension to additional variables. Thus, the model can be used to analyze experimental data regarding the effects of various factors on phytoplankton growth rate. Such a model will also be useful in analysis of the role of concentration of various nutrients or trace elements, temperature, and light intensity, or other important explanatory variables, or combinations of such variables, in analyzing phytoplankton growth dynamics.

  15. Photophysiological expressions of iron stress in phytoplankton.

    Science.gov (United States)

    Behrenfeld, Michael J; Milligan, Allen J

    2013-01-01

    Iron is essential for all life, but it is particularly important to photoautotrophs because of the many iron-dependent electron transport components in photosynthetic membranes. Since the proliferation of oxygenic photosynthesis in the Archean ocean, iron has been a scarce commodity, and it is now recognized as a limiting resource for phytoplankton over broad expanses of the open ocean and even in some coastal/continental shelf waters. Iron stress does not impair photochemical or carbon fixation efficiencies, and in this respect it resembles the highly tuned photosynthetic systems of steady-state macronutrient-limited phytoplankton. However, iron stress does present unique photophysiological challenges, and phytoplankton have responded to these challenges through major architectural changes in photosynthetic membranes. These evolved responses include overexpression of photosynthetic pigments and iron-economic pathways for ATP synthesis, and they result in diagnostic fluorescence properties that allow a broad appraisal of iron stress in the field and even the detection of iron stress from space.

  16. Iron-nutrient interactions within phytoplankton

    Directory of Open Access Journals (Sweden)

    Hanan Schoffman

    2016-08-01

    Full Text Available 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.

  17. 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.

  18. 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

  19. 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...... patterns, like stripes, spots, and the mixture of them depending on the toxicity level. We also observe that the distribution of nutrient and phytoplankton shows spatiotemporal oscillation for certain toxicity level. (C) 2015 Elsevier Inc. All rights reserved....

  20. Phytoplankton diversity and abundance in Ndop wetland plain ...

    African Journals Online (AJOL)

    Phytoplankton is very sensitive to nutrient changes. Very little work has been carried out on the effect of these changes on the phytoplankton community in the Ndop wetland. Four paddy-field sites were studied to evaluate the effect of some abiotic factors on their occurrence and abundance of phytoplankton. Water samples ...

  1. Uncertainty Analysis of Phytoplankton Dynamics in Coastal Waters

    NARCIS (Netherlands)

    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

  2. Regional to Global Assessments of Phytoplankton Dynamics From The SeaWiFS Mission

    Science.gov (United States)

    Siegel, David; Behrenfeld, Michael; Maritorena, Stephanie; McClain, Charles R.; Antoine, David; Bailey, Sean W.; Bontempi, Paula S.; Boss, Emmanuel S.; Dierssen, Heidi M.; Doney, Scott C.; hide

    2013-01-01

    Photosynthetic production of organic matter by microscopic oceanic phytoplankton fuels ocean ecosystems and contributes roughly half of the Earth's net primary production. For 13 years, the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) mission provided the first consistent, synoptic observations of global ocean ecosystems. Changes in the surface chlorophyll concentration, the primary biological property retrieved from SeaWiFS, have traditionally been used as a metric for phytoplankton abundance and its distribution largely reflects patterns in vertical nutrient transport. On regional to global scales, chlorophyll concentrations covary with sea surface temperature (SST) because SST changes reflect light and nutrient conditions. However, the oceanmay be too complex to be well characterized using a single index such as the chlorophyll concentration. A semi-analytical bio-optical algorithm is used to help interpret regional to global SeaWiFS chlorophyll observations from using three independent, well-validated ocean color data products; the chlorophyll a concentration, absorption by CDM and particulate backscattering. First, we show that observed long-term, global-scale trends in standard chlorophyll retrievals are likely compromised by coincident changes in CDM. Second, we partition the chlorophyll signal into a component due to phytoplankton biomass changes and a component caused by physiological adjustments in intracellular chlorophyll concentrations to changes in mixed layer light levels. We show that biomass changes dominate chlorophyll signals for the high latitude seas and where persistent vertical upwelling is known to occur, while physiological processes dominate chlorophyll variability over much of the tropical and subtropical oceans. The SeaWiFS data set demonstrates complexity in the interpretation of changes in regional to global phytoplankton distributions and illustrates limitations for the assessment of phytoplankton dynamics using chlorophyll

  3. Volcanism, Iron, and Phytoplankton in the Heard and McDonald Islands Region, Southern Indian Ocean

    Science.gov (United States)

    Coffin, M. F.; Arculus, R. J.; Bowie, A. R.; Chase, Z.; Robertson, R.; Trull, T. W.; Heobi in2016 v01 Shipboard Party, T.

    2016-12-01

    Phytoplankton supply approximately half of the oxygen in Earth's atmosphere, and iron supply limits the growth of phytoplankton in the anemic Southern Ocean. Situated entirely within the Indian Ocean sector of the Southern Ocean are Australia's only active subaerial volcanoes, Heard and McDonald islands (HIMI) on the central Kerguelen Plateau, a large igneous province. Widespread fields of submarine volcanoes, some of which may be active, extend for distances of up to several hundred kilometers from the islands. The predominantly eastward-flowing Antarctic Circumpolar Current sweeps across the central Kerguelen Plateau, and extensive blooms of phytoplankton are observed on the Plateau down-current of HIMI. The goal of RV Investigator voyage IN2016_V01, conducted in January/February 2016, is to test the hypothesis that hydrothermal fluids, which cool active submarine volcanoes in the HIMI region, ascend from the seafloor and fertilise surface waters with iron, thereby enhancing biological productivity beginning with phytoplankton. Significant initial shipboard results include: Documentation, for the first time, of the role of active HIMI and nearby submarine volcanoes in supplying iron to the Southern Ocean. Nearshore waters had elevated dissolved iron levels. Although biomass was not correspondingly elevated, fluorescence induction data indicated highly productive resident phytoplankton. Discovery of >200 acoustic plumes emanating from the seafloor and ascending up to tens of meters into the water column near HIMI. Deep tow camera footage shows bubbles rising from the seafloor in an acoustic plume field north of Heard Island. Mapping 1,000 km2 of uncharted seafloor around HIMI. Submarine volcanic edifices punctuate the adjacent seafloor, and yielded iron-rich rocks similar to those found on HIMI, respectively. Acoustic plumes emanating from some of these features suggest active seafloor hydrothermal systems.

  4. Phytoplankton adapt to changing ocean environments.

    Science.gov (United States)

    Irwin, Andrew J; Finkel, Zoe V; Müller-Karger, Frank E; Troccoli Ghinaglia, Luis

    2015-05-05

    Model projections indicate that climate change may dramatically restructure phytoplankton communities, with cascading consequences for marine food webs. It is currently not known whether evolutionary change is likely to be able to keep pace with the rate of climate change. For simplicity, and in the absence of evidence to the contrary, most model projections assume species have fixed environmental preferences and will not adapt to changing environmental conditions on the century scale. Using 15 y of observations from Station CARIACO (Carbon Retention in a Colored Ocean), we show that most of the dominant species from a marine phytoplankton community were able to adapt their realized niches to track average increases in water temperature and irradiance, but the majority of species exhibited a fixed niche for nitrate. We do not know the extent of this adaptive capacity, so we cannot conclude that phytoplankton will be able to adapt to the changes anticipated over the next century, but community ecosystem models can no longer assume that phytoplankton cannot adapt.

  5. Environmental influence on phytoplankton production during ...

    African Journals Online (AJOL)

    Phytoplankton adaptation to variable environmental conditions was characterised by a decreased light-limited slope (αB) and increased rate of photosynthesis (PmB) and light saturation (Ek) with elevated temperatures. The converse (increased αB and decreased PmB and Ek) was observed as irradiance levels declined.

  6. A vertically resolved model for phytoplankton aggregation

    Indian Academy of Sciences (India)

    components undergo vertical mixing, and phytoplank- ton sink. Phytoplankton growth is limited by the product of nutrient and light terms. The equations for nitrate (NO3) and ... resolved model there is an extra complication: the largest particles that sink out of ...... and biogeochemistry with satellite ocean colour data. Vertically ...

  7. 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. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. 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.

  9. The dynamical landscape of marine phytoplankton diversity

    Science.gov (United States)

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

    2015-01-01

    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. PMID:26400196

  10. Algae, phytoplankton and eutrophication research and management ...

    African Journals Online (AJOL)

    A brief history of South African research on and management of algae-, phytoplankton- and eutrophication-related problems is presented, including their ecological, social and economic impacts, which provides a basis for formulation of future research needs. The contributions of southern African research on different ...

  11. Quantifying interspecific coagulation efficiency of phytoplankton

    DEFF Research Database (Denmark)

    Hansen, J.L.S.; Kiørboe, Thomas

    1997-01-01

    . 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...

  12. Spatial distribution and community structure of phytoplankton ...

    African Journals Online (AJOL)

    The composition and distribution of the main planktonic halophilic microorganisms were studied in 12 ponds of different salinity levels, ranging from 38 to 328, in the saltern of Sousse, Tunisia, in relation to environmental factors. Nutrient concentrations increased with decreasing salinity in the ponds. Phytoplankton, ciliate ...

  13. Scaling laws in phytoplankton nutrient uptake affinity

    DEFF Research Database (Denmark)

    Lindemann, Christian; Fiksen, Øyvind; Andersen, Ken Haste

    2016-01-01

    instantaneously. Here we provide empirical evidence that the perfect sink strategy is not common in phytoplankton. Although small cells are indeed favored by a large surface to volume ratio, we show that they are punished by higher relative investment cost in order to fully benefit from the larger surface...

  14. Distribution of nutrients, chlorophyll and phytoplankton primary ...

    African Journals Online (AJOL)

    The aim of this study was to determine the characteristic rates of phytoplankton production in water bodies bordering the Benguela-Angolan frontal region and differing in their hydrographic, hydrochemical and biological properties. Two cruises were undertaken in the vicinity of the Cape Frio upwelling cell and the ...

  15. Immuno flow cytometry in marine phytoplankton research

    NARCIS (Netherlands)

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

    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.

  16. Physicochemical Flux and Phytoplankton diversity in Shagari ...

    African Journals Online (AJOL)

    USER

    2007-03-20

    Mar 20, 2007 ... (Carpenter and Kitchell, 1993). Phytoplankton studies of shallow, tropical Nigerian reservoirs such as Shagari reservoir could provide management guide to the reservoir water quality and its fisheries, since most of these reservoirs are constructed solely for drinking water supply, but with fish production.

  17. Effect of Phytoplankton Richness on Phytoplankton Biomass Is Weak Where the Distribution of Herbivores is Patchy.

    Science.gov (United States)

    Weis, Jerome J

    2016-01-01

    Positive effects of competitor species richness on competitor productivity can be more pronounced at a scale that includes heterogeneity in 'bottom-up' environmental factors, such as the supply of limiting nutrients. The effect of species richness is not well understood in landscapes where variation in 'top-down' factors, such as the abundance of predators or herbivores, has a strong influence competitor communities. I asked how phytoplankton species richness directly influenced standing phytoplankton biomass in replicate microcosm regions where one patch had a population of herbivores (Daphnia pulicaria) and one patch did not have herbivores. The effect of phytoplankton richness on standing phytoplankton biomass was positive but weak and not statistically significant at this regional scale. Among no-Daphnia patches, there was a significant positive effect of phytoplankton richness that resulted from positive selection effects for two dominant and productive species in polycultures. Among with-Daphnia patches there was not a significant effect of phytoplankton richness. The same two species dominated species-rich polycultures in no- and with-Daphnia patches but both species were relatively vulnerable to consumption by Daphnia. Consistent with previous studies, this experiment shows a measurable positive influence of primary producer richness on biomass when herbivores were absent. It also shows that given the patchy distribution of herbivores at a regional scale, a regional positive effect was not detected.

  18. Solar irradiance changes and photobiological effects at earth's surface following astrophysical ionizing radiation events.

    Science.gov (United States)

    Thomas, Brian C; Neale, Patrick J; Snyder, Brock R

    2015-03-01

    Astrophysical ionizing radiation events have been recognized as a potential threat to life on Earth, primarily through depletion of stratospheric ozone and subsequent increase in surface-level solar ultraviolet radiation. Simulations of the atmospheric effects of a variety of events (such as supernovae, gamma-ray bursts, and solar proton events) have been previously published, along with estimates of biological damage at Earth's surface. In this work, we employed the Tropospheric Ultraviolet and Visible (TUV) radiative transfer model to expand and improve calculations of surface-level irradiance and biological impacts following an ionizing radiation event. We considered changes in surface-level UVB, UVA, and photosynthetically active radiation (visible light) for clear-sky conditions and fixed aerosol parameter values. We also considered a wide range of biological effects on organisms ranging from humans to phytoplankton. We found that past work overestimated UVB irradiance but that relative estimates for increase in exposure to DNA-damaging radiation are still similar to our improved calculations. We also found that the intensity of biologically damaging radiation varies widely with organism and specific impact considered; these results have implications for biosphere-level damage following astrophysical ionizing radiation events. When considering changes in surface-level visible light irradiance, we found that, contrary to previous assumptions, a decrease in irradiance is only present for a short time in very limited geographical areas; instead we found a net increase for most of the modeled time-space region. This result has implications for proposed climate changes associated with ionizing radiation events.

  19. Viewer Makes Radioactivity "Visible"

    Science.gov (United States)

    Yin, L. I.

    1983-01-01

    Battery operated viewer demonstrates feasibility of generating threedimensional visible light simulations of objects that emit X-ray or gamma rays. Ray paths are traced for two pinhold positions to show location of reconstructed image. Images formed by pinholes are converted to intensified visible-light images. Applications range from radioactivity contamination surveys to monitoring radioisotope absorption in tumors.

  20. Visibility and Citation Impact

    Science.gov (United States)

    Ebrahim, Nader Ale; Salehi, Hadi; Embi, Mohamed Amin; Tanha, Farid Habibi; Gholizadeh, Hossein; Motahar, Seyed Mohammad

    2014-01-01

    The number of publications is the first criteria for assessing a researcher output. However, the main measurement for author productivity is the number of citations, and citations are typically related to the paper's visibility. In this paper, the relationship between article visibility and the number of citations is investigated. A case study of…

  1. Visible Human Project

    Science.gov (United States)

    ... NLM Mobile Gallery Site Navigation Home The Visible Human Project ® Overview The Visible Human Project ® is an outgrowth of the NLM's 1986 ... dimensional representations of the normal male and female human bodies. Acquisition of transverse CT, MR and cryosection ...

  2. Bacterial and Phytoplankton Responses to Nutrient Amendments in a Boreal Lake Differ According to Season and to Taxonomic Resolution

    Science.gov (United States)

    Peura, Sari; Eiler, Alexander; Hiltunen, Minna; Nykänen, Hannu; Tiirola, Marja; Jones, Roger I.

    2012-01-01

    Nutrient limitation and resource competition in bacterial and phytoplankton communities may appear different when considering different levels of taxonomic resolution. Nutrient amendment experiments conducted in a boreal lake on three occasions during one open water season revealed complex responses in overall bacterioplankton and phytoplankton abundance and biovolume. In general, bacteria were dominant in spring, while phytoplankton was clearly the predominant group in autumn. Seasonal differences in the community composition of bacteria and phytoplankton were mainly related to changes in observed taxa, while the differences across nutrient treatments within an experiment were due to changes in relative contributions of certain higher- and lower-level phylogenetic groups. Of the main bacterioplankton phyla, only Actinobacteria had a treatment response that was visible even at the phylum level throughout the season. With increasing resolution (from 75 to 99% sequence similarity) major responses to nutrient amendments appeared using 454 pyrosequencing data of 16S rRNA amplicons. This further revealed that OTUs (defined by 97% sequence similarity) annotated to the same highly resolved freshwater groups appeared to occur during different seasons and were showing treatment-dependent differentiation, indicating that OTUs within these groups were not ecologically coherent. Similarly, phytoplankton species from the same genera responded differently to nutrient amendments even though biovolumes of the majority of taxa increased when both nitrogen and phosphorus were added simultaneously. The bacterioplankton and phytoplankton community compositions showed concurrent trajectories that could be seen in synchronous succession patterns over the season. Overall, our data revealed that the response of both communities to nutrient changes was highly dependent on season and that contradictory results may be obtained when using different taxonomic resolutions. PMID:22715392

  3. Effects of UV radiation on phytoplankton

    Science.gov (United States)

    Smith, Raymond C.; Cullen, John J.

    1995-07-01

    It is now widely documented that reduced ozone will result in increased levels of ultraviolet (UV) radiation, especially UV-B (280-320nm), incident at the surface of the earth [Watson, 1988; Anderson et al., 1991; Schoeberl and Hartmann, 1991; Frederick and Alberts, 1991; WMO, 1991; Madronich, 1993; Kerr and McElroy, 1993], and there is considerable and increasing evidence that these higher levels of UV-B radiation may be detrimental to various forms of marine life in the upper layers of the ocean. With respect to aquatic ecosystems, we also know that this biologically- damaging mid-ultraviolet radiation can penetrate to ecologically- significant depths in marine and freshwater systems [Jerlov, 1950; Lenoble, 1956; Smith and Baker, 1979; Smith and Baker, 1980; Smith and Baker, 1981; Kirk et al., 1994]. This knowledge, plus the dramatic decline in stratospheric ozone over the Antarctic continent each spring, now known to be caused by anthropogenically released chemicals [Solomon, 1990; Booth et al., 1994], has resulted in increased UV-environmental research and a number of summary reports. The United Nations Environmental Program (UNEP) has provided recent updates with respect to the effects of ozone depletion on aquatic ecosystems (Hader, Worrest, Kumar in UNEP 1989, 1991, Hader, Worrest, Kumar and Smith UNEP 1994) and the Scientific Committee on Problems of the Environment (SCOPE) has provided [SCOPE, 1992] a summary of the effects of increased UV radiation on biological systems. SCOPE has also reported [SCOPE, 1993] on the effects of increased UV on the biosphere. In addition, several books have recently been published reviewing various aspects of environmental UV photobiology [Young et al., 1993], UV effects on humans, animals and plants [Tevini, 1993], the biological effects of UV radiation in Antarctica [Weiler and Penhale, 1994], and UV research in freshwater ecosystems [Williamson and Zagarese, 1994]. Several other reviews are relevant [NAS, 1984; Caldwell

  4. B Vitamins as Regulators of Phytoplankton Dynamics

    Science.gov (United States)

    Panzeca, Caterina; Tovar-Sanchez, Antonio; Agustí, Susana; Reche, Isabel; Duarte, Carlos M.; Taylor, Gordon T.; Sañudo-Wilhelmy, Sergio A.

    2006-12-01

    Without an adequate supply of dissolved vitamins, many species of phytoplankton do not grow. Additions of inorganic nutrients like phosphorus and nitrogen, and trace metals like iron, are not alone adequate to sustain life-a practical lesson learned quickly by experimental biologists when they try to keep eukaryotic phytoplankton cultures alive in their labs. The reason is that coenzymes such as B vitamins are also required for many metabolic pathways. For example, vitamin B1 serves as a cofactor for a large number of enzymatic systems, including the pyruvate dehydrogenase complex required for the metabolism of carbohydrates (glycolysis) and amino acid synthesis [Vandamme, 1989]. Vitamin B12 is used primarily to assist two enzymes: methionine synthase, which is involved in DNA synthesis, and methylmalonyl CoA mutase, which is required for inorganic carbon assimilation [Lindemans and Abels, 1985].

  5. 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

  6. 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

  7. 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 __m 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.

  8. Effect of seasonal changing temperature on the growth of phytoplankton.

    Science.gov (United States)

    Chen, Ming; Fan, Meng; Yuan, Xing; Zhu, Huaiping

    An non-autonomous nutrient-phytoplankton interacting model incorporating the effect of time-varying temperature is established. The impacts of temperature on metabolism of phytoplankton such as nutrient uptake, death rate, and nutrient releasing from particulate nutrient are investigated. The ecological reproductive index is formulated to present a threshold criteria and to characterize the dynamics of phytoplankton. The positive invariance, dissipativity, and the existence and stability of boundary and positive periodic solution are established. The analyses rely on the comparison principle, the coincidence degree theory and Lyapunov direct method. The effect of seasonal temperature and daily temperature on phytoplankton biomass are simulated numerically. Numerical simulation shows that the phytoplankton biomass is very robust to the variation of water temperature. The dynamics of the model and model predictions agree with the experimental data. Our model and analysis provide a possible explanation of triggering mechanism of phytoplankton blooms.

  9. [Phytoplankton community structure in Mingzhu Lake of Chongming Island, Shanghai].

    Science.gov (United States)

    Chen, Li-Jing; Wu, Zhu-Chen; Hu, Zhong-Jun; Peng, Zi-Ran; Liu, Qi-Gen

    2011-06-01

    A preliminary study was conducted on the phytoplankton community structure and the annual variation of species diversity in Mingzhu Lake of Chongming Island from January to December 2007. A total of 120 phytoplankton species belonging to 8 phyla and 63 genera were collected, among which, Phormidium tenue, Meismopedia tenuissima, M. convoluta, Microcystis incerta and Synedra ulna were the dominant species. The mean annual density and biomass of the phytoplankton were 5361.57 x 10(4) cell x L(-1) and 7.68 mg x L(-1) respectively. There was a significant difference in the monthly phytoplankton standing crop (P phytoplankton community were higher in spring and winter than in the summer and autumn. Biological evaluation indicated that the water quality of Mingzhu Lake was better in spring and winter than in the other two seasons, and canonical correlation analysis (CCA) suggested that the main factors affecting the phytoplankton community were water temperature, followed by total phosphorus, and total nitrogen.

  10. Macroecological patterns in the distribution of marine phytoplankton

    DEFF Research Database (Denmark)

    Mousing, Erik Askov

    and community size structure at the global scale. The statistical approach applied indicated that different nutrients were, apparently, co-limiting the examined phytoplankton processes in different regions of the world’s oceans. It is also shown that there is a strong increase in both phytoplankton total...... for predicting future ocean function. This PhD thesis investigates and describes macroecological patterns in the distribution and diversity of marine phytoplankton. The primary focus has been to describe macroecological patterns in phytoplankton total biomass and community structure and relate these patterns...... are presented as five research chapters shaped as manuscripts. In Manuscript I, the macroecological patterns in phytoplankton community size structure were investigated in relation to temperature and inorganic nutrient concentrations. Although temperature has been shown to directly affect phytoplankton size...

  11. Marine Aerosol Precursor Emissions for Earth System Models

    Energy Technology Data Exchange (ETDEWEB)

    Maltrud, Mathew Einar [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-07-25

    Dimethyl sulfide (DMS) is generated by marine ecosystems and plays a major role in cloud formation over the ocean. Currently, Earth System Models use imposed flux of DMS from the ocean to the atmosphere that is independent of the climate state. We have added DMS as a prognostic variable to the Community Earth System Model (CESM) that depends on the distribution of phytoplankton species, and thus changes with climate.

  12. Phytoplankton biomass and productivity in the Great Astrolabe lagoon

    OpenAIRE

    Charpy, Loïc

    1996-01-01

    Phytoplankton biomass and productivity of the Great Astrolabe Reef lagoon were studied using measurements of chlorophyll concentration and carbon uptake. Average chlorophyll concentration was 0.8 mg/m3 with 45 % of phytoplankton passing through 3 microm. Primary production was 1.3 gC/m2/day (30 m depth) with 47 % due to phytoplankton < 3 microm. (Résumé d'auteur)

  13. Impact of Submesoscale Processes on Dynamics of Phytoplankton Filaments

    Science.gov (United States)

    2015-02-12

    RESPONSIBLE PERSON 19b. TELEPHONE NUMBER (Include area code) 29-04-2015 Journal Article Impact of submesoscale processes on dynamics of phytoplankton ...in contrast to the earlier summer time, when the ASC mixes phytoplankton much deeper to the area below of the euphotic depth, and chlorophyll a...filaments are 3 -4 times weaker. coastal processes; upwelling, submesoscale processes, phytoplankton filaments Unclassified Unclassified Unclassified UU 13 Igor Shulman (228) 688-5646 Reset

  14. 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.

  15. Synthesis of visibility detection systems.

    Science.gov (United States)

    2012-10-01

    Visibility is a critical component to the task of driving on all types of roads. The visibility detection and warning systems provide real-time, automated detection as well as appropriate responses to counteract reduced visibility conditions due to f...

  16. Phytoplankton responses to aluminum enrichment in the South China Sea.

    Science.gov (United States)

    Zhou, Linbin; Liu, Jiaxing; Xing, Shuai; Tan, Yehui; Huang, Liangmin

    2017-09-22

    Compared to extensive studies reporting the aluminum (Al) toxicity to terrestrial plants and freshwater organisms, very little is known about how marine phytoplankton responds to Al in the field. Here we report the marine phytoplankton responses to Al enrichment in the South China Sea (SCS) using on-deck bottle incubation experiments during eight cruises from May 2010 to November 2013. Generally, Al addition alone enhanced the growth of diatom and Trichodesmium, and nitrogen fixation, but it inhibited the growth of dinoflagellates and Synechococcus. Nevertheless, Al addition alone did not influence the chlorophyll a concentration of the entire phytoplankton assemblages. By adding nitrate and phosphate simultaneously, Al enrichment led to substantial increases in chlorophyll a concentration (especially that of the picophytoplankton<3μm), and cell abundances of diatom and photosynthetic picoeukaryotes. These results indicate varied responses of phytoplankton in different size fractions and taxonomic groups to Al enrichment. Further, by simultaneously adding different macronutrients and/or sufficient trace metals including iron, we found that the phytoplankton responses to Al enrichment were relevant to nutrients coexisting in the environment. Al enrichment may give some phytoplankton a competitive edge over using nutrients, especially the limited ones. The possible influences of Al on the competitors and grazers (predators) of some phytoplankton might indirectly contribute to the positive responses of the phytoplankton to Al enrichment. Our results indicate that Al may influence marine carbon cycle by impacting phytoplankton growth and structure in natural seawater. Copyright © 2017. Published by Elsevier Inc.

  17. Phytoplankton ice-edge blooms in the marginal ice zone at Princess Astrid Coast in Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Verlecar, X.N.; Dhargalkar, V.K.; Goswami, S.C.; Mhamal, N.P.

    of the phytoplankton crop. Species distribution showed that herbivore zooplankters dominated the phytoplankton bloom periods while carnivores during non-bloom periods. The results suggest that while mixing processes are prominent the active growth of phytoplankton...

  18. Allelopathic interactions between phytoplankton species : the roles of heterotrophic bacteria and mixing intensity

    NARCIS (Netherlands)

    Hulot, F.; Huisman, J.

    2004-01-01

    Toxin-producing phytoplankton species may compensate for competitive disadvantages by secreting chemicals that affect toxin-sensitive phytoplankton species. Heterotrophic bacteria, however, may, in turn, degrade the toxins produced by allelopathic phytoplankton, thus confounding allelopathic

  19. Predicting Visibility of Aircraft

    Science.gov (United States)

    Watson, Andrew; Ramirez, Cesar V.; Salud, Ellen

    2009-01-01

    Visual detection of aircraft by human observers is an important element of aviation safety. To assess and ensure safety, it would be useful to be able to be able to predict the visibility, to a human observer, of an aircraft of specified size, shape, distance, and coloration. Examples include assuring safe separation among aircraft and between aircraft and unmanned vehicles, design of airport control towers, and efforts to enhance or suppress the visibility of military and rescue vehicles. We have recently developed a simple metric of pattern visibility, the Spatial Standard Observer (SSO). In this report we examine whether the SSO can predict visibility of simulated aircraft images. We constructed a set of aircraft images from three-dimensional computer graphic models, and measured the luminance contrast threshold for each image from three human observers. The data were well predicted by the SSO. Finally, we show how to use the SSO to predict visibility range for aircraft of arbitrary size, shape, distance, and coloration. PMID:19462007

  20. Measuring visibility using smartphones

    Science.gov (United States)

    Friesen, Jan; Bialon, Raphael; Claßen, Christoph; Graffi, Kalman

    2017-04-01

    Spatial information on fog density is an important parameter for ecohydrological studies in cloud forests. The Dhofar cloud forest in Southern Oman exhibits a close interaction between the fog, trees, and rainfall. During the three month monsoon season the trees capture substantial amounts of horizontal precipitation from fog which increases net precipitation below the tree canopy. As fog density measurements are scarce, a smartphone app was designed to measure visibility. Different smartphone units use a variety of different parts. It is therefore important to assess the developed visibility measurement across a suite of different smartphones. In this study we tested five smartphones/ tablets (Google/ LG Nexus 5X, Huawei P8 lite, Huawei Y3, HTC Nexus 9, and Samsung Galaxy S4 mini) against digital camera (Sony DLSR-A900) and visual visibility observations. Visibility was assessed from photos using image entropy, from the number of visible targets, and from WiFi signal strength using RSSI. Results show clear relationships between object distance and fog density, yet a considerable spread across the different smartphone/ tablet units is evident.

  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. UVISS preliminary visibility analysis

    DEFF Research Database (Denmark)

    Betto, Maurizio

    1998-01-01

    The goal of this work is to obtain a preliminary assessment of the sky visibility for anastronomical telescope located on the express pallet of the International SpaceStation (ISS)} taking into account the major constraints imposed on the instrument by the ISSattitude and structure. Part of the w......The goal of this work is to obtain a preliminary assessment of the sky visibility for anastronomical telescope located on the express pallet of the International SpaceStation (ISS)} taking into account the major constraints imposed on the instrument by the ISSattitude and structure. Part...... of the work is also to setup the kernel of a software tool for the visibility analysis thatshould be easily expandable to consider more complex strucures for future activities.This analysis is part of the UVISS assessment study and it is meant to provide elementsfor the definition and the selection...

  3. Between visibility and surveillance

    DEFF Research Database (Denmark)

    Uldam, Julie

    As activists move from alternative media platforms to commercial social media platforms they face increasing challenges in protecting their online security and privacy. While government surveillance of activists is well-documented in both scholarly research and the media, corporate surveillance...... of activists remains under-researched. This presentation explores visibility as a prerequisite and an obstacle to political participation. The dual capacity of visibility in social media enables both surveillance and counter-surveillance by making not only the surveilled actor, but also the surveilling actor......’ surveillance of anti-capitalist activists in social media....

  4. Making Invisible Forces Visible

    DEFF Research Database (Denmark)

    Ratner, Helene; Pors, Justine Grønbæk

    2013-01-01

    This paper investigates managerial tactics of visualisation when a need to know and manage employees' values and attitudes is expressed. Using the Danish public school as a case study, we explore how school managers use teachers' emotions to render visible presumably invisible information about...... their 'true' attitudes and values. The paper draws on theories of affect as well as actor-network theory to analyse three incidents where managers turn their interpretations of teachers' emotions into such information. These incidents suggest that the efforts to render employees' attitudes and values visible...

  5. Why large cells dominate estuarine phytoplankton

    Science.gov (United States)

    Cloern, James E.

    2018-01-01

    Surveys across the world oceans have shown that phytoplankton biomass and production are dominated by small cells (picoplankton) where nutrient concentrations are low, but large cells (microplankton) dominate when nutrient-rich deep water is mixed to the surface. I analyzed phytoplankton size structure in samples collected over 25 yr in San Francisco Bay, a nutrient-rich estuary. Biomass was dominated by large cells because their biomass selectively grew during blooms. Large-cell dominance appears to be a characteristic of ecosystems at the land–sea interface, and these places may therefore function as analogs to oceanic upwelling systems. Simulations with a size-structured NPZ model showed that runs of positive net growth rate persisted long enough for biomass of large, but not small, cells to accumulate. Model experiments showed that small cells would dominate in the absence of grazing, at lower nutrient concentrations, and at elevated (+5°C) temperatures. Underlying these results are two fundamental scaling laws: (1) large cells are grazed more slowly than small cells, and (2) grazing rate increases with temperature faster than growth rate. The model experiments suggest testable hypotheses about phytoplankton size structure at the land–sea interface: (1) anthropogenic nutrient enrichment increases cell size; (2) this response varies with temperature and only occurs at mid-high latitudes; (3) large-cell blooms can only develop when temperature is below a critical value, around 15°C; (4) cell size diminishes along temperature gradients from high to low latitudes; and (5) large-cell blooms will diminish or disappear where planetary warming increases temperature beyond their critical threshold.

  6. A Lagrangian View of Spring Phytoplankton Blooms

    Science.gov (United States)

    Kida, Shinichiro; Ito, Takamitsu

    2017-11-01

    The mechanisms of spring phytoplankton blooms are investigated from a Lagrangian framework by using a Lagrangian NPZD model that can track the movement and transfers of nutrient parcels in a turbulent environment. The model reveals that the onset of spring blooms depends on the cumulative euphotic age, which is the total time that inorganic nutrient is exposed to light before the photosynthetic conversion to phytoplankton biomass. A spring bloom, defined as a tenfold increase of near-surface phytoplankton, occurs when this cumulative euphotic age is approximately μeff-1·ln⁡10, where μeff is the effective growth rate in the euphotic layer, regardless of the underlying mechanism. If the turbulent layer depth is shallower than the critical depth and turbulence is strong, nutrient parcels accumulate enough light exposure through multiple entries to the sun-lit zone near the surface. If turbulence is weak, as that considered in the critical turbulence theory, the accumulation of the light exposure depends on the residence time of the nutrients parcels near the surface. The spectral shape of the cumulative euphotic age can clearly distinguish these two modes of spring blooms. The spectrum shows a peak at the theoretical growth timescale when multiple entries become important, while it shows a maximum near age zero that decays with age when the near-surface residence time becomes important. Mortality increases the cumulative euphotic age necessary for a bloom but does not affect the spectral shape, suggesting that it does not alter the primary mechanism behind the accumulation of cumulative euphotic age.

  7. Solar Irradiance Changes And Photobiological Effects At Earth's Surface Following Astrophysical Ionizing Radiation Events

    Science.gov (United States)

    Thomas, Brian; Neale, Patrick

    2016-01-01

    Astrophysical ionizing radiation events have been recognized as a potential threat to life on Earth for decades. Although there is some direct biological damage on the surface from redistributed radiation several studies have indicated that the greatest long term threat is from ozone depletion and subsequent heightened solar ultraviolet (UV) radiation. It is known that organisms exposed to this irradiation experience harmful effects such as sunburn and even direct damage to DNA, proteins, or other cellular structures. Simulations of the atmospheric effects of a variety of events (such as supernovae, gamma-ray bursts, and solar proton events) have been previously published, along with estimates of biological damage at Earth's surface. In the present work, we employed a radiative transfer model to expand and improve calculations of surface-level irradiance and biological impacts following an ionizing radiation event. We considered changes in surface-level UVB, UVA, and photosynthetically active radiation (visible light). Using biological weighting functions we have considered a wide range of effects, including: erythema and skin cancer in humans; inhibition of photosynthesis in the diatom Phaeodactylum sp. and dinoflagellate Prorocentrum micans inhibition of carbon fixation in Antarctic phytoplankton; inhibition of growth of oat (Avena sativa L. cv. Otana) seedlings; and cataracts. We found that past work overestimated UVB irradiance, but that relative estimates for increase in exposure to DNA damaging radiation are still similar to our improved calculations. We also found that the intensity of biologically damaging radiation varies widely with organism and specific impact considered; these results have implications for biosphere-level damage following astrophysical ionizing radiation events. When considering changes in surface-level visible light irradiance, we found that, contrary to previous assumptions, a decrease in irradiance is only present for a short time in

  8. 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...

  9. Phytoplankton chytridiomycosis: fungal parasites of phytoplankton and their imprints on the food web dynamics.

    Science.gov (United States)

    Sime-Ngando, Télesphore

    2012-01-01

    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. I reach the

  10. Distributions of phytoplankton in a coastal lagoon of Mahin, Ondo ...

    African Journals Online (AJOL)

    Distributions of phytoplankton were investigated in Mahin Lagoon within Transgressive mud coast of Ondo, Western Nigeria. Collections and analyses of samples of phytoplankton and surface waters (for some physico-chemical parameters) were done at fifteen stations along the stretch of the lagoon in October 2013 and ...

  11. Hydro-environmental factors and phytoplankton of the Atlantic ...

    African Journals Online (AJOL)

    Hydro-environmental factors and phytoplankton of the Atlantic Ocean, off the Light House Beach, Lagos, Nigeria. ... hydro-environmental factors and phytoplankton components reflected a tropical unpolluted neritic and oceanic environment. Keywords: Physico-chemistry, micro-algae, sea, Lighthouse Beach, Atlantic Ocean ...

  12. 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

  13. Nutrients and toxin producing phytoplankton control algal blooms–a ...

    Indian Academy of Sciences (India)

    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 ...

  14. The phytoplankton component of seston in San Francisco Bay

    Science.gov (United States)

    Wienke, S.M.; Cloern, J.E.

    1987-01-01

    Phytoplankton biomass (as carbon) was estimated from chlorophyll a concentrations (Chla) and a mean value for the ratio of phytoplankton carbon to chlorophyll a in San Francisco Bay. The ratio was determined as the slope of a Model II regression of POC' against (Chla), where POC' is total particulate organic carbon minus sediment-associated non-phytoplankton carbon. Samples from 30 fixed sites in the channel and lateral shoals of San Francisco Bay were collected once or twice a month from April to November 1980, and at irregular intervals in South Bay during 1984 and 1985. For all data the calculated mean value of phytoplankton C:Chla was 51 (95% confidence interval = 47-54). No significant differences were found in the C:Chla ratio between shallow and deep sites (where light availability differs) or between northern and southern San Francisco Bay (where phytoplankton community composition differs). Using the mean C:Chla ratio of 51, we calculated that phytoplankton biomass constitutes about one third of seston carbon under most circumstances, but this fraction ranges from about 95% during phytoplankton blooms to less than 20% during spring periods of low phytoplankton biomass and high suspended sediment concentration. ?? 1987.

  15. Response of phytoplankton assemblages isolated for short periods ...

    African Journals Online (AJOL)

    The response of phytoplankton assemblages isolated in enclosures for short periods of time was examined in hyper-eutrophic Lake Chivero (Harare, Zimbabwe), to determine the factors that influenced the structure of the phytoplankton community, after noticing a marked decline in the dominance of Microcystis aeruginosa ...

  16. A mesocosm tool to optically study phytoplankton dynamics

    NARCIS (Netherlands)

    Peperzak, L.; Timmermans, K.R.; Wernand, M.R.; Oosterhuis, S.; van der Woerd, H.J.

    2011-01-01

    The accuracy of remote sensing algorithms for phytoplankton biomass and physiology is difficult to test under natural conditions due to rapid changes in physical and biological forcings and the practical inability to manipulate nutrient conditions and phytoplankton composition in the sea. Therefore,

  17. Distribution of phytoplankton and chlorophyll a around little Andaman Island

    Digital Repository Service at National Institute of Oceanography (India)

    Devassy, V.P.; Bhattathiri, P.M.A.

    0.014 to 0.064(av.0.029). Depthwise distribution of phytoplankton chl a and phaeo-pigments showed an increasing trend up to 1% light in the 2 coral banks. Phytoplankton population ranged from 1400 to 4900 cells/litre. Dinoflagellates formed...

  18. Nutrients and toxin producing phytoplankton control algal blooms ...

    Indian Academy of Sciences (India)

    Unknown

    A phytoplankton-zooplankton prey-predator model has been investigated for temporal, spatial and spatio-tem- poral 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 ...

  19. The decline in phytoplankton biomass and prawn catches in the ...

    African Journals Online (AJOL)

    We combined in-situ measurement and ocean colour satellite data to determine and assess trends in phytoplankton biomass and sea surface temperature between 2002 and 2014. These trends were related to a declining prawn fishery in the Channel. While phytoplankton displayed a significant declining trend during the ...

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

    NARCIS (Netherlands)

    Huisman, Jef

    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

  1. Effect of pollution on phytoplankton occurrence and distribution in ...

    African Journals Online (AJOL)

    The phytoplankton distribution of some parts of River Kaduna receiving Industrial effluents was surveyed for a period of one year. A total number of 2166 specimens of phytoplankton represented by four major taxa namely: Chlorophyceae, Bacillariophyceae, Cyanophyceae and Dinophyceae, were encountered.

  2. Spatial and temporal patterns of phytoplankton abundance and ...

    African Journals Online (AJOL)

    Phytoplankton abundance and composition in relation to physico-chemical parameters were investigated from September 2005 to October 2007 at 51 stations of various depths in the nearshore, intermediate and deep offshore waters of Lake Victoria. Shallow nearshore waters had the highest abundance of phytoplankton ...

  3. Seasonal distribution of phytoplankton in the Aby lagoon system ...

    African Journals Online (AJOL)

    Seasonal variability of phytoplankton species composition, abundance and physical and chemical factors influencing phytoplankton dynamics were investigated in the Aby lagoon system, south-eastern Ivory Coast, covering the main climatic seasons in 2006–2007. Seasonal and spatial variability of nutrient concentrations ...

  4. Water quality status and phytoplankton composition in Soetendalvlei ...

    African Journals Online (AJOL)

    Three wetlands on the Agulhas Plain, for which no limnological information was available, were investigated in order to provide baseline data on their present water quality and phytoplankton community structure. Physicochemical variables were assessed and phytoplankton biomass and community analyses were ...

  5. Wet season spatial occurrence of phytoplankton and zooplankton in ...

    African Journals Online (AJOL)

    Investigation into the spatial occurrence of wet season phytoplankton and zooplankton in Lagos lagoon, Nigeria was carried out in October, 2008 in 12 stations. A total of 36 species of phytoplankton from 21 genera, 20 zooplankton species from 17 genera and 10 juvenile forms were recorded for the study. The results ...

  6. The phytoplankton of Great Bitter Lake, Egypt, including the impacts ...

    African Journals Online (AJOL)

    A year-long survey of the phytoplankton and nutrients in Great Bitter Lake indicates that this is a severely eutrophic lake. Chlorophyll levels were consistently high (> 30µg/l), especially in summer (>90µg/l). The phytoplankton community comprised mostly diatoms and blue-green algae, although dinoflagellates and green ...

  7. Awortwi et al.: Mixing and stratification relationship on phytoplankton ...

    African Journals Online (AJOL)

    Awortwi et al.: Mixing and stratification relationship on phytoplankton of Lake Bosomtwe (Ghana) 43 West African Journal of Applied Ecology, vol. 23(2), 2015: 43–62. The Relationship Between Mixing and Stratification Regime on the Phytoplankton of Lake Bo.

  8. A prospective study of marine phytoplankton and reported ...

    Science.gov (United States)

    BACKGROUND: Blooms of marine phytoplankton may adversely affect human health. The potential public health impact of low-level exposures is not well established, and few prospective cohort studies of recreational exposures to marine phytoplankton have been conducted.OBJECTIVE: We evaluated the association between phytoplankton cell counts and subsequent illness among recreational beachgoers.METHODS:We recruited beachgoers at Boquer6n Beach, Puerto Rico, during the summer of 2009. We conducted interviews at three time points to assess baseline health, water activities, and subsequent illness. Daily water samples were quantitatively assayed for phytoplankton cell count. Logistic regression models, adjusted for age and sex, were used to assess the association between exposure to three categories of phytoplankton concentration and subsequent illness.RESULTS: During 26 study days, 15,726 individuals successfully completed all three interviews. Daily total phytoplankton cell counts ranged from 346 to 2,012 cells/ml (median, 712 cells/ml). The category with the highest (≥75th percentile) total phytoplankton cell count was associated with eye irritation [adjusted odds ratio (OR) = 1.30; 95% confidence interval (Cl): 1.01, 1.66], rash (OR = 1.27; 95% Cl: 1.02, 1.57), and earache (OR = 1.25; 95% Cl: 0.88, 1.77). In phytoplankton group-specific analyses, the category with the highest Cyanobacteria counts was associated with respiratory illness (OR = 1.37; 95% Cl: 1.12, 1

  9. Toxicity of lead and cadmium to tropical marine phytoplankton

    DEFF Research Database (Denmark)

    Jensen, Susanne Dal; Panutrakul, Suwanna; Nyholm, Niels

    2000-01-01

    Toxicity of Pb and Cd to three tropical, marine phytoplankton species isolated from the Andaman Sea off Phuket Thailand were determined. The phytoplankton species included one diatom, Chaetoceros calcitrans, one green alga, Chlorella sp., and one chrysophyte, Dunaliella tertiolecta. The test method...

  10. Dry Season Phytoplankton Composition Of Ibiekuma Dam, Ekpoma ...

    African Journals Online (AJOL)

    In this study, the phytoplankton composition of Ibiekuma dam, Ekpoma was investigated between January and February, 2010. A total of 20 phytoplankton taxa belonging to three divisions; Bacillariophyta, Chlorophyta and Euglenophyta were observed. All the species of Bacillariophyta observed were pennate forms.

  11. Monitoring and prediction of phytoplankton dynamics in the North Sea

    NARCIS (Netherlands)

    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

  12. Phytoplankton production and adaptation in the vicinity of Pemba ...

    African Journals Online (AJOL)

    Phytoplankton production and physiology were investigated at six selected locations during a research cruise in early October 2007 in Tanzanian coastal waters. The dataset included photosynthesis–irradiance and active fluorescence parameters, phytoplankton absorption coefficients, and pigment concentrations. Primary ...

  13. Seasonal Variability of Phytoplankton Population in the Brahmani ...

    African Journals Online (AJOL)

    Based on the collected samples from six stations, phytoplankton population, DO, BOD, salinity and nutrient (o-PO4, NO3+NH3) were examined. The phytoplankton abundance varies with the seasonal variation. Due to wave action and circulation patterns DO distribution shows a marginal variation at different sampling ...

  14. Checklist of Phytoplankton of Shendam Reserviour in Plateau State ...

    African Journals Online (AJOL)

    A qualitative study of phytoplankton flora was carried out in Shendam reservoir, Plateau state of Nigeria. Seventy one species were recorded indicating a fairly low species number when compared to other Nigerian waters. The major groups of phytoplankton found were chlorophyceae, bacilliarophyceae, cyanophyceae and ...

  15. The visibility complex

    NARCIS (Netherlands)

    Pocchiola, M; Vegter, G

    We introduce the visibility complex (rr 2-dimensional regular cell complex) of a collection of n pairwise disjoint convex obstacles in the plane. It can be considered as a subdivision of the set of free rays (i.e., rays whose origins lie in free space, the complement of the obstacles). Its cells

  16. Visible Solid State Lasers

    NARCIS (Netherlands)

    Hikmet, R.A.M.

    2007-01-01

    Diode lasers can be found in various applications most notably in optical communication and optical storage. Visible lasers were until recently were all based on IR diode lasers. Using GaN, directly blue and violet emitting lasers have also been introduced to the market mainly in the area of optical

  17. Visible but Unseen?

    DEFF Research Database (Denmark)

    Torkilsheyggi, Arnvør Martinsdóttir á; Hertzum, Morten

    2015-01-01

    to support awareness in a setting where the users are (locally) mobile, specifically in regard to information that requires continuous monitoring. We do however also find that the whiteboard safeguarded the work with blood tests against some risks by making blood-test information socially visible....

  18. Evaluation of Visible Plumes.

    Science.gov (United States)

    Brennan, Thomas

    Developed for presentation at the 12th Conference on Methods in Air Pollution and Industrial Hygiene Studies, University of Southern California, April, 1971, this outline discusses plumes with contaminants that are visible to the naked eye. Information covers: (1) history of air pollution control regulations, (2) need for methods of evaluating…

  19. Spatial and temporal distribution of phytoplankton in Lake Skadar

    Directory of Open Access Journals (Sweden)

    Rakočević Jelena

    2012-01-01

    Full Text Available Phytoplankton seasonal succession and spatial heterogeneity were studied in Lake Skadar from February to December 2004. A total of 167 taxa from 6 algal divisions were observed, with Bacillariophyta being best represented (52.8%. The general pattern of phytoplankton seasonal succession in Lake Skadar was: Bacillariophyta in the spring, Chlorophyta in early summer, Cyanobacteria and Chlorophyta in late summer and Bacillariophyta and Chlorophyta in autumn and winter. Distinct spatial heterogeneity was observed. The central, open part of the lake (pelagic zone was characterized by dominant euplanktonic species, mostly diatoms, whereas the western and northwestern parts (more isolated and shallower had higher abundance of greens and blue-greens and a higher percentage of resuspended benthic-epiphytic forms in the phytoplankton community. Comparison with former phytoplankton data showed distinct differences in terms of the qualitative and quantitative composition of the phytoplankton community of Lake Skadar, which indicates lake deterioration.

  20. Dynamics of phytoplankton blooms in turbulent vortex cells

    DEFF Research Database (Denmark)

    Lindemann, Christian; Visser, Andre; Mariani, Patrizio

    2017-01-01

    Turbulence and coherent circulation structures, such as submesoscale and mesoscale eddies, convective plumes and Langmuir cells, play a critical role in shaping phytoplankton spatial distribution and population dynamics. We use a framework of advection-reaction-diffusion equations to investigate...... the effects of turbulent transport on the phytoplankton population growth and its spatial structure in a vertical two-dimensional vortex flow field. In particular, we focus on how turbulent flow velocities and sinking influence phytoplankton growth and biomass aggregation. Our results indicate that conditions...... in mixing and growth of phytoplankton can drive different vertical spatial structures in the mixed layer, with the depth of the mixed layer being a critical factor to allow coexistence of populations with different sinking speed. With increasing mixed layer depth, positive growth for sinking phytoplankton...

  1. 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.

  2. Development of phytoplankton communities: Implications of nutrient injections on phytoplankton composition, pH and ecosystem production

    DEFF Research Database (Denmark)

    Jakobsen, Hans; Blanda, Elisa; Stæhr, Peter Anton

    2015-01-01

    The development of a marine phytoplankton community was studied in a series of mesocosm tanks exposed to different levels of nutrient inputs. Key ecosystem variables such as phytoplankton species development, ecosystem net production (NEP), pH and bacteria production were measured. The overall aim...

  3. Toxicity of atmospheric aerosols on marine phytoplankton.

    Science.gov (United States)

    Paytan, Adina; Mackey, Katherine R M; Chen, Ying; Lima, Ivan D; Doney, Scott C; Mahowald, Natalie; Labiosa, Rochelle; Post, Anton F

    2009-03-24

    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.

  4. Title: Freshwater phytoplankton responses to global warming.

    Science.gov (United States)

    Wagner, Heiko; Fanesi, Andrea; Wilhelm, Christian

    2016-09-20

    Global warming alters species composition and function of freshwater ecosystems. However, the impact of temperature on primary productivity is not sufficiently understood and water quality models need to be improved in order to assess the quantitative and qualitative changes of aquatic communities. On the basis of experimental data, we demonstrate that the commonly used photosynthetic and water chemistry parameters alone are not sufficient for modeling phytoplankton growth under changing temperature regimes. We present some new aspects of the acclimation process with respect to temperature and how contrasting responses may be explained by a more complete physiological knowledge of the energy flow from photons to new biomass. We further suggest including additional bio-markers/traits for algal growth such as carbon allocation patterns to increase the explanatory power of such models. Although carbon allocation patterns are promising and functional cellular traits for growth prediction under different nutrient and light conditions, their predictive power still waits to be tested with respect to temperature. A great challenge for the near future will be the prediction of primary production efficiencies under the global change scenario using a uniform model for phytoplankton assemblages. Copyright © 2016 Elsevier GmbH. All rights reserved.

  5. 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.

  6. 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. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. 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

    APPP, 958 come from sites between 30 and 60° N; we found only 36 for sites south of 20° N. Second, of the 131 ecosystems where APPP has been reported, 37% are based on measurements at only one location during 1 year. The accuracy of these values is unknown but probably low, given the large interannual and spatial variability within ecosystems. Finally, global assessments are confounded by measurements that are not intercomparable because they were made with different methods. Phytoplankton primary production along the continental margins is tightly linked to variability of water quality, biogeochemical processes including ocean-atmosphere CO2 exchange, and production at higher trophic levels including species we harvest as food. The empirical record has deficiencies that preclude reliable global assessment of this key Earth system process. We face two grand challenges to resolve these deficiencies: (1) organize and fund an international effort to use a common method and measure APPP regularly across a network of coastal sites that are globally representative and sustained over time, and (2) integrate data into a unifying model to explain the wide range of variability across ecosystems and to project responses of APPP to regional manifestations of global change as it continues to unfold.

  8. 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

    reported values of APPP, 958 come from sites between 30 and 60° N; we found only 36 for sites south of 20° N. Second, of the 131 ecosystems where APPP has been reported, 37% are based on measurements at only one location during 1 year. The accuracy of these values is unknown but probably low, given the large interannual and spatial variability within ecosystems. Finally, global assessments are confounded by measurements that are not intercomparable because they were made with different methods. Phytoplankton primary production along the continental margins is tightly linked to variability of water quality, biogeochemical processes including ocean–atmosphere CO2 exchange, and production at higher trophic levels including species we harvest as food. The empirical record has deficiencies that preclude reliable global assessment of this key Earth system process. We face two grand challenges to resolve these deficiencies: (1) organize and fund an international effort to use a common method and measure APPP regularly across a network of coastal sites that are globally representative and sustained over time, and (2) integrate data into a unifying model to explain the wide range of variability across ecosystems and to project responses of APPP to regional manifestations of global change as it continues to unfold.

  9. Making Heat Visible

    Science.gov (United States)

    Goodhew, Julie; Pahl, Sabine; Auburn, Tim; Goodhew, Steve

    2015-01-01

    Householders play a role in energy conservation through the decisions they make about purchases and installations such as insulation, and through their habitual behavior. The present U.K. study investigated the effect of thermal imaging technology on energy conservation, by measuring the behavioral effect after householders viewed images of heat escaping from or cold air entering their homes. In Study 1 (n = 43), householders who received a thermal image reduced their energy use at a 1-year follow-up, whereas householders who received a carbon footprint audit and a non-intervention control demonstrated no change. In Study 2 (n = 87), householders were nearly 5 times more likely to install draught proofing measures after seeing a thermal image. The effect was especially pronounced for actions that addressed an issue visible in the images. Findings indicate that using thermal imaging to make heat loss visible can promote energy conservation. PMID:26635418

  10. Social media visibility

    DEFF Research Database (Denmark)

    Uldam, Julie

    2017-01-01

    As activists move from alternative media platforms to commercial social media platforms, they face increasing challenges in protecting their online security and privacy. While government surveillance of activists is well-documented in scholarly research and the media, corporate surveillance...... for responding to the activities of individual activists in social media. It shows that while social media afford an unprecedented level of visibility for activists, it comes with the risk of being monitored by corporations. Theoretically, it draws on conceptions of visibility in social sciences and media...... studies as well as literature on activism and political participation in media studies. Empirically, it draws on files from BP on specific civil society individuals obtained through Subject Access Requests under the UK Data Protection Act 1998 as well as press responses from BP....

  11. On court interpreters' visibility

    DEFF Research Database (Denmark)

    Dubslaff, Friedel; Martinsen, Bodil

    of the service they receive. Ultimately, the findings will be used for training purposes. Future - and, for that matter, already practising - interpreters as well as the professional users of interpreters ought to take the reality of the interpreters' work in practice into account when assessing the quality...... in by the participants almost immediately after the interrogations and supplemented by interviews. The main objective of the project is to explore the interpreters' own perception of the quality of the service they render as well as the professional users´ and the other language users' perception of the quality...... of the interpreter as an invisible language switcher. However, a closer look at the data shows that, even in a less complex constellation like the one analysed here, there is clear evidence of the interpreter's visibility. We shall identify various forms of visibility based on the discourse data...

  12. Visibility graph motifs

    CERN Document Server

    Iacovacci, Jacopo

    2015-01-01

    Visibility algorithms transform time series into graphs and encode dynamical information in their topology, paving the way for graph-theoretical time series analysis as well as building a bridge between nonlinear dynamics and network science. In this work we introduce and study the concept of visibility graph motifs, smaller substructures that appear with characteristic frequencies. We develop a theory to compute in an exact way the motif profiles associated to general classes of deterministic and stochastic dynamics. We find that this simple property is indeed a highly informative and computationally efficient feature capable to distinguish among different dynamics and robust against noise contamination. We finally confirm that it can be used in practice to perform unsupervised learning, by extracting motif profiles from experimental heart-rate series and being able, accordingly, to disentangle meditative from other relaxation states. Applications of this general theory include the automatic classification a...

  13. Method 446.0: In Vitro Determination of Chlorophylls a, b, c + c and Pheopigments in 1 2Marine And Freshwater Algae by Visible Spectrophotometry

    Science.gov (United States)

    This method provides a procedure for determination of chlorophylls a (chl a), b (chl b), c + c 1 2 (chl c + c ) and pheopigments of chlorophyll a (pheo a) 1 2 found in marine and freshwater phytoplankton. Chlorophyllide a is determined as chl a. Visible wavelength spectrophotomet...

  14. Interferometric visibility and coherence

    Science.gov (United States)

    Biswas, Tanmoy; García Díaz, María; Winter, Andreas

    2017-07-01

    Recently, the basic concept of quantum coherence (or superposition) has gained a lot of renewed attention, after Baumgratz et al. (Phys. Rev. Lett. 113, 140401. (doi:10.1103/PhysRevLett.113.140401)), following Åberg (http://arxiv.org/abs/quant-ph/0612146), have proposed a resource theoretic approach to quantify it. This has resulted in a large number of papers and preprints exploring various coherence monotones, and debating possible forms for the resource theory. Here, we take the view that the operational foundation of coherence in a state, be it quantum or otherwise wave mechanical, lies in the observation of interference effects. Our approach here is to consider an idealized multi-path interferometer, with a suitable detector, in such a way that the visibility of the interference pattern provides a quantitative expression of the amount of coherence in a given probe state. We present a general framework of deriving coherence measures from visibility, and demonstrate it by analysing several concrete visibility parameters, recovering some known coherence measures and obtaining some new ones.

  15. Evacuation under limited visibility

    Science.gov (United States)

    Frank, Guillermo A.; Dorso, Claudio O.

    2015-06-01

    A multiplicity of situations can trigger off an evacuation of a room under panic conditions. For "normal" (with "normal" meaning absence of obstacles, perfect visibility, etc.) environmental conditions, the "faster is slower" effect dominates the dynamics of this process. It states that as the pedestrians desire to reach the exit increases, the clogging phenomena delays the time to get out of the room. But, environmental conditions are usually far from "normal." In this work, we consider that pedestrians have to find their way out under low visibility conditions. Some of them might switch to a herding-like behavior if they do not remember where the exit was. Others will just trust on their memory. Our investigation handles the herding and memory effects on the evacuation of a single exit room with no obstacles. We also include a section on how signaling devices affect the evacuation process. Unexpectedly, some low visibility situations may enhance the evacuation performance. This can be resumed as a second paradoxical result, since we demonstrated in an earlier investigation that "clever is not always better" G. A. Frank and C. O. Dorso, Physica A 390, 2135 (2011).

  16. Paradoxes of Visibility

    Directory of Open Access Journals (Sweden)

    Tarnay László

    2017-12-01

    Full Text Available The paper investigates two possible critical arguments following the pictorial turn. The first is formulated within ocularcentrism, the dominance of sight, and starts with the right to visibility as a general principle that governs today’s digital culture but gets twisted in special cases like the Auschwitz photos of the Shoa, the Abu Ghraib prison videos, or recently the website called Yolocaust. The second is conceived outside the visual culture and is meant to vindicate the other senses vis-à-vis the eyes. However, the argument is truncated here only to highlight the boomerang effect of the other senses: haptic vision. It is the case of visual perception when (a there is a lack of things to see and (b indeterminate synaesthesia: when vision intensifies the other senses in the embodied viewer. The two arguments converge upon a dialectic of the visible and the imaginable, which is formulated here as two paradoxes that the discussed examples transcend. By enforcing visibility at all costs where there is hardly anything recognizable to see, they lead to two diverging results. On the one hand, the meaning of “image” is extended toward the unimaginable, the traumatic experience, on the other hand, it is extended toward the invisible, the encounter with the radical Other.

  17. [Phytoplankton community structure and eutrophication risk assessment of Beijiang River].

    Science.gov (United States)

    Gou, Ting; Ma, Qian-Li; Xu, Zhen-Cheng; Wang, Li; Li, Jie; Zhao, Xue-Min

    2015-03-01

    To study the distribution of phytoplankton and water quality of Beijiang River, the community structure of phytoplankton was investigated and analyzed in wet and dry seasons. The results showed that a total of 74 species belonging to six phyla, 29 family and 48 genera of phytoplankton were identified, including 58 species of five phyla, 23 family and 41 genera in wet season and 59 species of six phyla, 26 family and 40 genera in dry season. Phytoplankton community structure in Beijiang River was represented by Bacillariophyta, Chlorophyta and Cyanophyta. Bacillariophyta dominanted the phytoplankton, and the dominant species were Aulacoseira granulate, Fragilaria virescens, Surirella biseriata, Nitzschia amphibia, Navicula simplex, Cyclotella meneghiniana, Synedra ulna, Gomphonema angustatum and Cymbella tumida. There was little difference in phytoplankton density between both seasons with the mean values being 3.54 x 10(5) and 4.87 x 10(5) cells L(-1) in dry and wet seasons, respectively. Based on the RDA results, DO, permanganate index, nitrogen and phosphorus were the important environmental factors affecting the distribution of phytoplankton in Beijiang River. The water quality of Beijiang River was classified as oligo-mesotrophic level even if this river was subjected to nitrogen and phosphorus pollution mainly from agricultural non-point source.

  18. Advection by ocean currents modifies phytoplankton size structure.

    Science.gov (United States)

    Font-Muñoz, Joan S; Jordi, Antoni; Tuval, Idan; Arrieta, Jorge; Anglès, Sílvia; Basterretxea, Gotzon

    2017-05-01

    Advection by ocean currents modifies phytoplankton size structure at small scales (1-10 cm) by aggregating cells in different regions of the flow depending on their size. This effect is caused by the inertia of the cells relative to the displaced fluid. It is considered that, at larger scales (greater than or equal to 1 km), biological processes regulate the heterogeneity in size structure. Here, we provide observational evidence of heterogeneity in phytoplankton size structure driven by ocean currents at relatively large scales (1-10 km). Our results reveal changes in the phytoplankton size distribution associated with the coastal circulation patterns. A numerical model that incorporates the inertial properties of phytoplankton confirms the role of advection on the distribution of phytoplankton according to their size except in areas with enhanced nutrient inputs where phytoplankton dynamics is ruled by other processes. The observed preferential concentration mechanism has important ecological consequences that range from the phytoplankton level to the whole ecosystem. © 2017 The Author(s).

  19. Influences of sea ice on eastern Bering Sea phytoplankton

    Science.gov (United States)

    Zhou, Qianqian; Wang, Peng; Chen, Changping; Liang, Junrong; Li, Bingqian; Gao, Yahui

    2015-03-01

    The influence of sea ice on the species composition and cell density of phytoplankton was investigated in the eastern Bering Sea in spring 2008. Diatoms, particularly pennate diatoms, dominated the phytoplankton community. The dominant species were Grammonema islandica (Grunow in Van Heurck) Hasle, Fragilariopsis cylindrus (Grunow) Krieger, F. oceanica (Cleve) Hasle, Navicula vanhoeffenii Gran, Thalassiosira antarctica Comber, T. gravida Cleve, T. nordenskiöeldii Cleve, and T. rotula Meunier. Phytoplankton cell densities varied from 0.08×104 to 428.8×104 cells/L, with an average of 30.3×104 cells/L. Using cluster analysis, phytoplankton were grouped into three assemblages defined by ice-forming conditions: open water, ice edge, and sea ice assemblages. In spring, when the sea ice melts, the phytoplankton dispersed from the sea ice to the ice edge and even into open waters. Thus, these phytoplankton in the sea ice may serve as a "seed bank" for phytoplankton population succession in the subarctic ecosystem. Moreover, historical studies combined with these results suggest that the sizes of diatom species have become smaller, shifting from microplankton to nannoplankton-dominated communities.

  20. The Importance of Phytoplankton Biomolecule Availability for Secondary Production

    Directory of Open Access Journals (Sweden)

    Elina T. Peltomaa

    2017-10-01

    Full Text Available The growth and reproduction of animals is affected by their access to resources. In aquatic ecosystems, the availability of essential biomolecules for filter-feeding zooplankton depends greatly on phytoplankton. Here, we analyzed the biochemical composition, i.e., the fatty acid, sterol and amino acid profiles and concentrations as well as protein, carbon, nitrogen, and phosphorus content of 17 phytoplankton monocultures representing the seven most abundant phytoplankton classes in boreal and sub-arctic lakes. To examine how the differences in the biochemical composition between phytoplankton classes affect their nutritional quality for consumers, we assessed the performance of Daphnia, on these diets. Furthermore, we defined the most important biomolecules regulating the somatic growth and reproduction of Daphnia, expecting that higher concentrations of certain biomolecules are needed for reproduction than for growth. Finally, we combined these results with phytoplankton field data from over 900 boreal and sub-arctic lakes in order to estimate whether the somatic growth of Daphnia is sterol-limited when the natural phytoplankton communities are cyanobacteria-dominated. Our analysis shows that Daphnia grows best with phytoplankton rich in sterols, ω-3 fatty acids, protein, and amino acids. Their reproduction follows food sterol and ω-3 concentration as well as C:P-ratio being two times higher in Daphnia feeding on cryptophytes than any other diet. Interestingly, we found that a high dietary ω-6 fatty acid concentration decreases both somatic growth and reproduction of Daphnia. When combined with phytoplankton community composition field data, our results indicate that zooplankton is constantly limited by sterols in lakes dominated by cyanobacteria (≥40% of total phytoplankton biomass, and that the absence of cryptophytes can severely hinder zooplankton production in nature.

  1. Observing and modelling phytoplankton community structure in the North Sea

    Science.gov (United States)

    Ford, David A.; van der Molen, Johan; Hyder, Kieran; Bacon, John; Barciela, Rosa; Creach, Veronique; McEwan, Robert; Ruardij, Piet; Forster, Rodney

    2017-03-01

    Phytoplankton form the base of the marine food chain, and knowledge of phytoplankton community structure is fundamental when assessing marine biodiversity. Policy makers and other users require information on marine biodiversity and other aspects of the marine environment for the North Sea, a highly productive European shelf sea. This information must come from a combination of observations and models, but currently the coastal ocean is greatly under-sampled for phytoplankton data, and outputs of phytoplankton community structure from models are therefore not yet frequently validated. This study presents a novel set of in situ observations of phytoplankton community structure for the North Sea using accessory pigment analysis. The observations allow a good understanding of the patterns of surface phytoplankton biomass and community structure in the North Sea for the observed months of August 2010 and 2011. Two physical-biogeochemical ocean models, the biogeochemical components of which are different variants of the widely used European Regional Seas Ecosystem Model (ERSEM), were then validated against these and other observations. Both models were a good match for sea surface temperature observations, and a reasonable match for remotely sensed ocean colour observations. However, the two models displayed very different phytoplankton community structures, with one better matching the in situ observations than the other. Nonetheless, both models shared some similarities with the observations in terms of spatial features and inter-annual variability. An initial comparison of the formulations and parameterizations of the two models suggests that diversity between the parameter settings of model phytoplankton functional types, along with formulations which promote a greater sensitivity to changes in light and nutrients, is key to capturing the observed phytoplankton community structure. These findings will help inform future model development, which should be coupled

  2. 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

  3. 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.

  4. Earth\\'s Mass Variability

    CERN Document Server

    Mawad, Ramy

    2014-01-01

    The perturbation of the Earth caused by variability of mass of Earth as additional reason with gravity of celestial bodies and shape of the Earth. The Earth eating and collecting matters from space and loss or eject matters to space through its flying in the space around the Sun. The source of the rising in the global sea level is not closed in global warming and icebergs, but the outer space is the additional important source for this rising. The Earth eats waters from space in unknown mechanism. The mass of the Earth become greater in November i.e. before transit apoapsis two months, and become latter in February i.e. after transit apoapsis to two months.

  5. UV-Visible Spectroscopic Method and Models for Assessment and Monitoring of Harmful Algal Blooms

    Science.gov (United States)

    Mitchell, B. Greg

    2000-01-01

    The development of an enhanced predictive and early warning capability for the occurrence and impact of harmful algal blooms (HABs) would be of great benefit to coastal communities. A critical issue for early detection and monitoring of HABs is the need to detect harmful algal species within a mixed-species phytoplankton assemblage. Possession of UV-absorbing compounds called mycosporine-like amino acids (MAAs) may be one factor that allows HAB species to out-compete their phytoplankton neighbors. Possession of MAAs, which we believe can be inferred from strong UV-absorption signals in phytoplankton absorption coefficients, can be used as a flag for potential HAB outbreak. The goal of this project was to develop a solar simulating UV-visible incubator to grow HAB dinoflagellates, to begin MAA analysis of samples collected on global cruises, and to carry out initial experiments on HAB dinoflagellate species in pure culture. Our scientific objectives are to quantify MAA production and spectral induction mechanisms in HAB species, to characterize spectral absorption of MAAs, and to define the ecological benefit of MAAs (i.e. photoprotection). Data collected on cruises to the global oceans will be used to parameterize phytoplankton absorption in the UV region, and this parameterization could be incorporated into existing models of seawater optical properties in the UV spectral region. Data collected in this project were used for graduate fellowship applications by Elizabeth Frame. She has been awarded an EPA STAR fellowship to continue the work initiated by this project.

  6. Variability in the mechanisms controlling Southern Ocean phytoplankton bloom phenology in an ocean model and satellite observations

    Science.gov (United States)

    Rohr, Tyler; Long, Matthew C.; Kavanaugh, Maria T.; Lindsay, Keith; Doney, Scott C.

    2017-05-01

    A coupled global numerical simulation (conducted with the Community Earth System Model) is used in conjunction with satellite remote sensing observations to examine the role of top-down (grazing pressure) and bottom-up (light, nutrients) controls on marine phytoplankton bloom dynamics in the Southern Ocean. Phytoplankton seasonal phenology is evaluated in the context of the recently proposed "disturbance-recovery" hypothesis relative to more traditional, exclusively "bottom-up" frameworks. All blooms occur when phytoplankton division rates exceed loss rates to permit sustained net population growth; however, the nature of this decoupling period varies regionally in Community Earth System Model. Regional case studies illustrate how unique pathways allow blooms to emerge despite very poor division rates or very strong grazing rates. In the Subantarctic, southeast Pacific small spring blooms initiate early cooccurring with deep mixing and low division rates, consistent with the disturbance-recovery hypothesis. Similar systematics are present in the Subantarctic, southwest Atlantic during the spring but are eclipsed by a subsequent, larger summer bloom that is coincident with shallow mixing and the annual maximum in division rates, consistent with a bottom-up, light limited framework. In the model simulation, increased iron stress prevents a similar summer bloom in the southeast Pacific. In the simulated Antarctic zone (70°S-65°S) seasonal sea ice acts as a dominant phytoplankton-zooplankton decoupling agent, triggering a delayed but substantial bloom as ice recedes. Satellite ocean color remote sensing and ocean physical reanalysis products do not precisely match model-predicted phenology, but observed patterns do indicate regional variability in mechanism across the Atlantic and Pacific.

  7. Earth's City Lights

    Science.gov (United States)

    2002-01-01

    This image of Earth's city lights was created with data from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS). Originally designed to view clouds by moonlight, the OLS is also used to map the locations of permanent lights on the Earth's surface. The brightest areas of the Earth are the most urbanized, but not necessarily the most populated. (Compare western Europe with China and India.) Cities tend to grow along coastlines and transportation networks. Even without the underlying map, the outlines of many continents would still be visible. The United States interstate highway system appears as a lattice connecting the brighter dots of city centers. In Russia, the Trans-Siberian railroad is a thin line stretching from Moscow through the center of Asia to Vladivostok. The Nile River, from the Aswan Dam to the Mediterranean Sea, is another bright thread through an otherwise dark region. Even more than 100 years after the invention of the electric light, some regions remain thinly populated and unlit. Antarctica is entirely dark. The interior jungles of Africa and South America are mostly dark, but lights are beginning to appear there. Deserts in Africa, Arabia, Australia, Mongolia, and the United States are poorly lit as well (except along the coast), along with the boreal forests of Canada and Russia, and the great mountains of the Himalaya. The Earth Observatory article Bright Lights, Big City describes how NASA scientists use city light data to map urbanization. Image by Craig Mayhew and Robert Simmon, NASA GSFC, based on DMSP data

  8. [Ecological characteristics of phytoplankton in coastal area of Pearl River estuary].

    Science.gov (United States)

    Dai, Ming; Li, Chunhou; Jia, Xiaoping; Zhang, Hanhua; Chen, Ruiwen

    2004-08-01

    Five cruises of phytoplankton survey were made in costal area of Pearl River estuary in 1998-1999. The results showed that 239 species were identified, 72.4% of which belonging to Bacillariophyta, 23.8% to Pyrrophyta, and 3.8% to others. The dominant species were warm and eurythermic species Thalassiothrix frauenfeldii, Nitzschia delicatissima, Thalassiothrix frauenfeldii and Thalassiosira subtilis, and changed with an obvious seasonal succession. The cell density ranged from 0.2 x 10(4) to 2,767.1 x 10(4) cell x m(-3), with an average of 98.7 x 10(4) cell x m(-3), and the mean cell density was obviously higher in summer and winter than in spring and autumn. The regional variation revealed that the cell density in shore area was visibly higher than that in offshore area, and the largest density area was at the southeast of Shangchuan Island all the year around. The range of mean Shannon-Wiener index, Pielou evenness index and biodiversity threshold was 2.63-3.17, 0.53-0.71 and 1.74-2.23, respectively. According to the diversity index, it was concluded that the diversity level of phytoplankton community in coastal area of Pearl River estuary was relatively high and stable.

  9. Seasonal phytoplanktonic diversity of Kitham lake, Agra.

    Science.gov (United States)

    Tiwari, Ashesh; Chauhan, S V S

    2006-01-01

    Two years (Jan. 2000 - Dec. 2001) data on the seasonal studies of phytoplanktonic diversity of Kitham lake (Sur Sarovar) Agra revealed the presence of 73 algal species. A limited number of these were recorded throughout the year, while others were distributed in different seasons mainly in winter and summer seasons. During winters, Chlorophyceae was the most dominant group followed by Bacillariophyceae. On the other hand, Cyanophyceae and Euglenophyceae were the most dominant during summers. Certain species e.g. Pandorina morum, Pediastrum tetras, Gonium sp., Chlorella vulgaris, Scendesmus quadricauda, Oedogonium cardiocum, Synedra ulna, Oscillatoria agardhii and Euglena gracillis were recorded throughout the year. Chlorella, Stigeoclonium, Pandorina, Micratinium, Oscillatoria, Anacystis, Nitzschia and Cymbella were found to be good indicators of water pollution.

  10. 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.

    . Numerical models experiments suggest an active role of phytoplankton in the equatorial ocean dynamics by modifying density and thus providing conditions favorable to phytoplankton growth, i.e., the potential positive feedback mechanism between the ecosystem...

  11. The visible ear simulator

    DEFF Research Database (Denmark)

    Sorensen, Mads Solvsten; Mosegaard, Jesper; Mikkelsen, Peter Trier

    2009-01-01

    material.Virtual training often requires the purchase of a program, a customized computer, and expensive peripherals dedicated exclusively to this purpose. MATERIALS AND METHODS: The Visible Ear freeware library of digital images from a fresh-frozen human temporal bone was segmented, and real-time volume......, 2D, or optional anaglyph stereoscopic 3D was achieved on a standard Core 2 Duo personal computer with a GeForce 8,800 GTX graphics card, and surgical interaction was provided through a relatively inexpensive (approximately $2,500) Phantom Omni haptic 3D pointing device. CONCLUSION: This prototype...

  12. WWW visibility in marketing

    OpenAIRE

    Ollila, T.

    2013-01-01

    Social media is a vital channel for marketers nowadays. Customers are more empowered today than ever before and the Internet is accelerating the trend toward greater customer empowerment. In few years Web 2.0 has become a highly important media and it has changed the Web into platform where individuals can communicate, assemble and organize data. Web 2.0 also offers a variety of different “tools” for companies to be used in marketing. Because companies and products are visible and discussed i...

  13. Laboratory LiF characterization of different phytoplankton species originating harmful blooms

    Energy Technology Data Exchange (ETDEWEB)

    Barbini, R.; Colao, F.; Fantoni, R.; Palucci, A.; Ribezzo, S. [ENEA, Centro Ricerche Frascati, Rome (Italy). Dip. Innovazione; Micheli, C. [ENEA, Centro Ricerche Casaccia, Rome (Italy). Dipt. Innovazione

    1997-11-01

    A systematic laboratory characterization of different phytoplankton cultures has been performed in combination with LiF (Laser Induced Fluorescence) measurements aimed to investigate the possibility of their remote monitoring by means of lidar fluoro sensor systems. Cultures of microalgae characterized by different pigment contents have been analyzed in the visible region upon UV laser excitation. High resolution laboratory spectra have been measured in order to obtain the fingerprint of each species. Emission wavelength related to the main pigments contribution have been identified. Detection limits of the emitted red chlorophyll signal have been evaluated for the different species after dilution in the culture medium and in real sea water. Prior to the LiF excitation aimed to the remote characterization the algal cultures were morphologically analyzed by fluorescence and scanning electron microscopy. Furthermore the relevant cell number was counted for biomass estimation, and the chlorophylls content was determined by different chemical methods.

  14. Adaptive divergence in pigment composition promotes phytoplankton biodiversity

    NARCIS (Netherlands)

    Stomp, M.; Huisman, Jef; de Jongh, F.; Veraart, Annelies; Gerla, Daan J.; Rijkeboer, M.; Ibelings, B.W.; Wollenzien, U.I.A.; Stal, L.J.

    2004-01-01

    The dazzling diversity of the phytoplankton has puzzled biologists for decades. The puzzle has been enlarged rather than solved by the progressive discovery of new phototrophic microorganisms in the oceans, including picocyanobacteria, pico-eukaryotes, and bacteriochlorophyll-based and

  15. Ecology of phytoplankton from Dharmatar Creek, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Tiwari, L.R.; Nair, V.R.

    Phytoplankton pigment, cell count and species diversity wee studied at five locations in Dharamtar Creek during September 1984 to November 1985. Chemical parameters indicated a healthy system free of any environmental stress. The water...

  16. Optimization of phytoplankton monitoring in the Baltic Sea

    Science.gov (United States)

    Jaanus, Andres; Kuprijanov, Ivan; Kaljurand, Kaire; Lehtinen, Sirpa; Enke, Annely

    2017-07-01

    Since water quality monitoring can be rather costly, it is important to properly design the monitoring network so that maximum information can be received with moderate effort. One component of monitoring is measuring the phytoplankton community composition and detecting whether that has changed. From April to October 2012, by using ships-of-opportunity (SOOP), we collected simultaneous samples from 15 stations in the Gulf of Finland and the Baltic Proper to study the spatial variability in the phytoplankton species composition and biomass throughout the growing season. The analysis was performed with 10 dominant taxa constituting 83-97% of the total phytoplankton biomass. We set the criterion of the statistically significant (p phytoplankton analysis between countries is addressed in order to have comparable data sets by different countries.

  17. Empirical relationships between phytoplankton and zooplankton biomass in Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Jayalakshmy, K.V.

    Empirical models based on regression analysis are derived using published values of phytoplankton and crustacean zooplankton biomass from Indian Ocean. Three regression models are derived. There is significant correlation between zooplankton...

  18. Variations in the spectral values of specific absorption of phytoplankton

    Digital Repository Service at National Institute of Oceanography (India)

    Sathyendranath, S.; Lazzara, L.; Prieur, L.

    Absorption spectra of laboratory cultures of eight species of phytoplankton were studied. These spectra, normalized per unit of chlorophyll a concentration (specific absorption) show variability in magnitude and spectral form. Specific absorption...

  19. 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.

    phytoplankton biomass during September-October to dust-induced iron fertilization when there is sufficient buildup of nitrate in the upper ocean. During winter, the enhanced evaporative cooling under the strengthening winds led to the increased convective mixing...

  20. Adaptations in phytoplankton to changing conditions in tropical estuaries

    Digital Repository Service at National Institute of Oceanography (India)

    Qasim, S.Z.

    Experimental studies on phytoplankton organisms from Cochin backwaters (a tropical estuary) have shown that many algal forms are adapted to changing conditions of salinity, light and nutrients. Photosynthesis in 12 species of algae was found...

  1. Host parasite interactions between freshwater phytoplankton and chytrid fungi (Chytridiomycota)

    NARCIS (Netherlands)

    Ibelings, B.W.; De Bruin, A.; Kagami, M.; Rijkeboer, M.; Brehm, Michaela; Van Donk, E.

    2004-01-01

    Some chytrids are host-specific parasiticfungithat may have a considerable impact on phytoplankton dynamics. The phylum Chytridiomycota contains one class, the Chytridiomycetes, and is composed of five different orders. Molecular studies now firmly place the Chytridiomycota within the fungal

  2. Cyanobacteria-phytoplankton dynamics of a hypertrophic African lake

    CSIR Research Space (South Africa)

    Zohary, T

    1995-01-01

    Full Text Available Phytoplankton species composition and abundance were recorded weekly or biweekly for nearly 7 years in a hypertrophic lake ( Hartbeespoort Dam, South Africa), together with a range of physical and chemical parameters. A total of 73 species were...

  3. Can we restore global phytoplankton, the westerly winds and other aspects of climate using geoengineering?

    Science.gov (United States)

    Wingenter, O. W.; Elliott, S. M.; Blake, D. R.; Blake, N. J.

    2010-12-01

    : Recent analysis of ocean transparency measurements and in situ chlorophyll observations indicate a global decline of ocean phytoplankton of ~40% since 1950. Global warming has increased stratification of the ocean surface, which is believed to be the cause. Because phytoplankton are the basis of the ocean food web, the importance of protecting this essential initial link cannot be over stated. Climate change has increased the temperature difference between the southern mid-and high-latitudes resulting in the Southern Hemispheric westerly winds shifting 3-4 degrees southward and intensifying 20% over the last 50 years. Alignment of the westerlies with the wind-driven Antarctic Circumpolar Current is key to the amount of ocean overturning circulation and is the chief mechanism in which deep water is vented. The upwelled water is saturated in CO2 resulting in greater sea-to-air flux of CO2 and the warmer water supplies heat to Antarctic sea ice, ice shelves, and ice sheets, causing them to melt, potentially accelerating sea level rise. It appears this system may be feeding back positively leading to a greater temperature differential and stronger winds. Can we safely cool the planet or perhaps specific regions in order to restore phytoplankton, realign the westerlies and lessen other unwanted consequences of climate change? We propose model simulations of stratospheric solar radiation management (SSRM) to see if this method may be workable as a general means to cool the Earth and restore the ocean mixed layert. If used in conjunction with cloud brightening-solar radiation management (CBSRM) the impact of SSRM on the westerlies may be controlled.

  4. Impact of El Niño Variability on Oceanic Phytoplankton

    Directory of Open Access Journals (Sweden)

    Marie-Fanny Racault

    2017-05-01

    Full Text Available Oceanic phytoplankton respond rapidly to a complex spectrum of climate-driven perturbations, confounding attempts to isolate the principal causes of observed changes. A dominant mode of variability in the Earth-climate system is that generated by the El Niño phenomenon. Marked variations are observed in the centroid of anomalous warming in the Equatorial Pacific under El Niño, associated with quite different alterations in environmental and biological properties. Here, using observational and reanalysis datasets, we differentiate the regional physical forcing mechanisms, and compile a global atlas of associated impacts on oceanic phytoplankton caused by two extreme types of El Niño. We find robust evidence that during Eastern Pacific (EP and Central Pacific (CP types of El Niño, impacts on phytoplankton can be felt everywhere, but tend to be greatest in the tropics and subtropics, encompassing up to 67% of the total affected areas, with the remaining 33% being areas located in high-latitudes. Our analysis also highlights considerable and sometimes opposing regional effects. During EP El Niño, we estimate decreases of −56 TgC/y in the tropical eastern Pacific Ocean, and −82 TgC/y in the western Indian Ocean, and increase of +13 TgC/y in eastern Indian Ocean, whereas during CP El Niño, we estimate decreases −68 TgC/y in the tropical western Pacific Ocean and −10 TgC/y in the central Atlantic Ocean. We advocate that analysis of the dominant mechanisms forcing the biophysical under El Niño variability may provide a useful guide to improve our understanding of projected changes in the marine ecosystem in a warming climate and support development of adaptation and mitigation plans.

  5. Early Spring Phytoplankton Dynamics in the Western Antarctic Peninsula

    Science.gov (United States)

    Arrigo, Kevin R.; van Dijken, Gert L.; Alderkamp, Anne-Carlijn; Erickson, Zachary K.; Lewis, Kate M.; Lowry, Kate E.; Joy-Warren, Hannah L.; Middag, Rob; Nash-Arrigo, Janice E.; Selz, Virginia; van de Poll, Willem

    2017-12-01

    The Palmer Long-Term Ecological Research program has sampled waters of the western Antarctic Peninsula (wAP) annually each summer since 1990. However, information about the wAP prior to the peak of the phytoplankton bloom in January is sparse. Here we present results from a spring process cruise that sampled the wAP in the early stages of phytoplankton bloom development in 2014. Sea ice concentrations were high on the shelf relative to nonshelf waters, especially toward the south. Macronutrients were high and nonlimiting to phytoplankton growth in both shelf and nonshelf waters, while dissolved iron concentrations were high only on the shelf. Phytoplankton were in good physiological condition throughout the wAP, although biomass on the shelf was uniformly low, presumably because of heavy sea ice cover. In contrast, an early stage phytoplankton bloom was observed beneath variable sea ice cover just seaward of the shelf break. Chlorophyll a concentrations in the bloom reached 2 mg m-3 within a 100-150 km band between the SBACC and SACCF. The location of the bloom appeared to be controlled by a balance between enhanced vertical mixing at the position of the two fronts and increased stratification due to melting sea ice between them. Unlike summer, when diatoms overwhelmingly dominate the phytoplankton population of the wAP, the haptophyte Phaeocystis antarctica dominated in spring, although diatoms were common. These results suggest that factors controlling phytoplankton abundance and composition change seasonally and may differentially affect phytoplankton populations as environmental conditions within the wAP region continue to change.

  6. 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.

  7. Assessment of phytoplankton and environmental variables for water quality and trophic state classification in the Gemlik Gulf, Marmara Sea (Turkey).

    Science.gov (United States)

    Balci, Muharrem; Balkis, Neslihan

    2017-02-15

    Phytoplankton assemblages related to environmental factors and ecological status of the Gemlik Gulf were investigated between June 2010 and May 2011. A total 155 phytoplankton species were detected and 6 taxa (Amphisolenia laticincta, Archaeperidinium minutum, Cochlodinium sp., Gynogonadinium aequatoriale, Heterocapsa rotundata and Metaphalacroma sp.) were new records for the Turkish Seas. The lowest and highest total phytoplankton abundance among the sampling units (depths) was recorded in April 2011 (7.4×103cellsL-1) and July 2010 (251.8×103cellsL-1). Local small patches of visible red tide events were detected especially in the gulf, although a phytoplankton bloom was not observed. The water column was well stratified in the early autumn and well mixed in the early spring according to stratification index values. Surface nutrient concentrations increased especially at stations located inside of the gulf. The limiting effect of silicate was observed in early, mid-summer and early winter periods while the nitrogen was the limiting nutrient in the gulf during the whole sampling period. In the Gulf, low water quality-high mesotrophic and bad water quality-eutrophic status, high quality and low trophic level were generally detected according to Chl a, dissolved oxygen and trophic index. However, indices developed to determine the trophic level and water quality of the Mediterranean Sea can give unexpected results about the current environmental quality status when it is applied to the Marmara Sea which has limited photic zone by the halocline-pycnocline and thermocline. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Zooplankton excretion metabolites stimulate Southern Ocean phytoplankton growth

    KAUST Repository

    Coello-Camba, A.

    2017-04-24

    Warming over Antarctica is leading to changes in the zooplankton communities inhabiting the Southern Ocean. It has been observed that zooplankton not only regulates phytoplankton through grazing, but also through the recycling of nutrients that are essential for phytoplankton growth. In this way, the effects of warming on zooplankton populations will change the amount or proportion at which recycled nutrients are restored. To estimate how the recycled nutrients released by zooplankton populations, dominated by krill (Euphausia superba), amphipods or copepods, affect the phytoplankton uptake and communities, we performed four incubation experiments: two close to the Antarctic Peninsula and two at the Southern Atlantic Ocean. Our results showed a stimulating effect of the addition of metabolites on ammonia removal rates and on the net growth of phytoplankton communities, with different responses amongst the different phytoplankton groups. According to our results, phytoplankton net growth and community composition may be altered if this relevant source of nutrients is lost due to projected changes in the abundance or distribution of these zooplankton populations.

  9. An automated platform for phytoplankton ecology and aquatic ecosystem monitoring.

    Science.gov (United States)

    Pomati, Francesco; Jokela, Jukka; Simona, Marco; Veronesi, Mauro; Ibelings, Bas W

    2011-11-15

    High quality monitoring data are vital for tracking and understanding the causes of ecosystem change. We present a potentially powerful approach for phytoplankton and aquatic ecosystem monitoring, based on integration of scanning flow-cytometry for the characterization and counting of algal cells with multiparametric vertical water profiling. This approach affords high-frequency data on phytoplankton abundance, functional traits and diversity, coupled with the characterization of environmental conditions for growth over the vertical structure of a deep water body. Data from a pilot study revealed effects of an environmental disturbance event on the phytoplankton community in Lake Lugano (Switzerland), characterized by a reduction in cytometry-based functional diversity and by a period of cyanobacterial dominance. These changes were missed by traditional limnological methods, employed in parallel to high-frequency monitoring. Modeling of phytoplankton functional diversity revealed the importance of integrated spatiotemporal data, including circadian time-lags and variability over the water column, to understand the drivers of diversity and dynamic processes. The approach described represents progress toward an automated and trait-based analysis of phytoplankton natural communities. Streamlining of high-frequency measurements may represent a resource for understanding, modeling and managing aquatic ecosystems under impact of environmental change, yielding insight into processes governing phytoplankton community resistance and resilience.

  10. Temperature and species richness effects in phytoplankton communities.

    Science.gov (United States)

    Schabhüttl, Stefanie; Hingsamer, Peter; Weigelhofer, Gabriele; Hein, Thomas; Weigert, Achim; Striebel, Maren

    2013-02-01

    Phytoplankton play an important role as primary producers and thus can affect higher trophic levels. Phytoplankton growth and diversity may, besides other factors, be controlled by seasonal temperature changes and increasing water temperatures. In this study, we investigated the combined effects of temperature and diversity on phytoplankton growth. In a controlled laboratory experiment, monocultures of 15 freshwater phytoplankton taxa (green algae, cyanobacteria, and diatoms) as well as 25 mixed communities of different species richness (2-12 species) and taxa composition were exposed to constant temperatures of 12, 18, and 24 °C. Additionally, they were exposed to short-term daily temperature peaks of +4 °C. Increased species richness had a positive effect on phytoplankton growth rates and phosphorous content at all temperature levels, with maximum values occurring at 18 °C. Overyielding was observed at almost all temperature levels and could mostly be explained by complementary traits. Higher temperatures resulted in higher fractions of cyanobacteria in communities. This negative effect of temperature on phytoplankton diversity following a shift in community composition was most obvious in communities adapted to cooler temperatures, pointing to the assumption that relative temperature changes may be more important than absolute ones.

  11. Warming will affect phytoplankton differently: evidence through a mechanistic approach.

    Science.gov (United States)

    Huertas, I Emma; Rouco, Mónica; López-Rodas, Victoria; Costas, Eduardo

    2011-12-07

    Although the consequences of global warming in aquatic ecosystems are only beginning to be revealed, a key to forecasting the impact on aquatic communities is an understanding of individual species' vulnerability to increased temperature. Despite their microscopic size, phytoplankton support about half of the global primary production, drive essential biogeochemical cycles and represent the basis of the aquatic food web. At present, it is known that phytoplankton are important targets and, consequently, harbingers of climate change in aquatic systems. Therefore, investigating the capacity of phytoplankton to adapt to the predicted warming has become a relevant issue. However, considering the polyphyletic complexity of the phytoplankton community, different responses to increased temperature are expected. We experimentally tested the effects of warming on 12 species of phytoplankton isolated from a variety of environments by using a mechanistic approach able to assess evolutionary adaptation (the so-called ratchet technique). We found different degrees of tolerance to temperature rises and an interspecific capacity for genetic adaptation. The thermal resistance level reached by each species is discussed in relation to their respective original habitats. Our study additionally provides evidence on the most resistant phytoplankton groups in a future warming scenario.

  12. The Effect of Atrazine on Louisiana Gulf Coast Estuarine Phytoplankton.

    Science.gov (United States)

    Starr, Alexis V; Bargu, Sibel; Maiti, Kanchan; DeLaune, Ronald D

    2017-02-01

    Pesticides may enter water bodies in areas with a high proportion of agricultural land use through surface runoff, groundwater discharge, and erosion and thus negatively impact nontarget aquatic organisms. The herbicide atrazine is used extensively throughout the Midwest and enters the Mississippi River through surface runoff and groundwater discharge. The purpose of this study was to determine the extent of atrazine contamination in Louisiana's estuaries from Mississippi River water under different flow and nutrient regimes (spring and summer) and its effect on the biomass and oxygen production of the local phytoplankton community. The results showed that atrazine was consistently present in these systems at low levels. Microcosm experiments exposed to an atrazine-dilution series under low and high nutrient conditions to determine the phytoplankton stress response showed that high atrazine levels greatly decreased phytoplankton biomass and oxygen production. Phytoplankton exposed to low and moderate atrazine levels under high nutrient conditions were able to recover after an extended acclimation period. Communities grown under high nutrient conditions grew more rapidly and produced greater levels of oxygen than the low nutrient treatment groups, thus indicating that atrazine exposure may induce a greater stress response in phytoplankton communities under low-nutrient conditions. The native community also experienced a shift from more sensitive species, such as chlorophytes, to potentially more resilient species such as diatoms. The phytoplankton response to atrazine exposure at various concentrations can be especially important to greater trophic levels because their growth and abundance can determine the potential productivity of the entire ecosystem.

  13. Amplified Arctic warming by phytoplankton under greenhouse warming.

    Science.gov (United States)

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

    2015-05-12

    Phytoplankton have attracted increasing attention in climate science due to their impacts on climate systems. A new generation of climate models can now provide estimates of future climate change, considering the biological feedbacks through the development of the coupled physical-ecosystem model. Here we present the geophysical impact of phytoplankton, which is often overlooked in future climate projections. A suite of future warming experiments using a fully coupled ocean-atmosphere model that interacts with a marine ecosystem model reveals that the future phytoplankton change influenced by greenhouse warming can amplify Arctic surface warming considerably. The warming-induced sea ice melting and the corresponding increase in shortwave radiation penetrating into the ocean both result in a longer phytoplankton growing season in the Arctic. In turn, the increase in Arctic phytoplankton warms the ocean surface layer through direct biological heating, triggering additional positive feedbacks in the Arctic, and consequently intensifying the Arctic warming further. Our results establish the presence of marine phytoplankton as an important potential driver of the future Arctic climate changes.

  14. 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 (pphytoplankton groups (chlorophytes and coccolithophores). Ocean biology in the South Pacific was not significantly correlated with MEI. During La Nina events, diatoms increased and expanded westward along the cold tongue (correlation with MEI, r=-0.81), while cyanobacteria concentrations decreased significantly (r=0.78). El Nino produced the reverse pattern, with cyanobacteria populations increasing while diatoms plummeted. The diverse response of phytoplankton in the different major basins of the Pacific suggests the different roles climate variability can play in ocean biology.

  15. Earth materials and earth dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, K; Shankland, T. [and others

    2000-11-01

    In the project ''Earth Materials and Earth Dynamics'' we linked fundamental and exploratory, experimental, theoretical, and computational research programs to shed light on the current and past states of the dynamic Earth. Our objective was to combine different geological, geochemical, geophysical, and materials science analyses with numerical techniques to illuminate active processes in the Earth. These processes include fluid-rock interactions that form and modify the lithosphere, non-linear wave attenuations in rocks that drive plate tectonics and perturb the earth's surface, dynamic recrystallization of olivine that deforms the upper mantle, development of texture in high-pressure olivine polymorphs that create anisotropic velocity regions in the convecting upper mantle and transition zone, and the intense chemical reactions between the mantle and core. We measured physical properties such as texture and nonlinear elasticity, equation of states at simultaneous pressures and temperatures, magnetic spins and bonding, chemical permeability, and thermal-chemical feedback to better characterize earth materials. We artificially generated seismic waves, numerically modeled fluid flow and transport in rock systems and modified polycrystal plasticity theory to interpret measured physical properties and integrate them into our understanding of the Earth. This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

  16. Glasses for seeing beyond visible.

    Science.gov (United States)

    Zhang, XiangHua; Bureau, Bruno; Lucas, Pierre; Boussard-Pledel, Catherine; Lucas, Jacques

    2008-01-01

    Conventional glasses based on oxides have a transparency limited by phonon absorption in the near IR region and have a limited interest for analyzing information located far beyond the visible. The IR spectral domain is nevertheless of prime interest, since it covers fundamental wavelength ranges used for thermal imaging as well as molecular vibrational signatures. Besides spectacular advances in the field of IR detectors, the main significant progresses are related to the development of IR glass optics, such as lenses or IR optical fibres. The field of IR glasses is almost totally dominated by glasses formed from heavy atoms such as the chalcogens S, Se and Te. Their transparency extends up to 12, 16 and 28 microm for sulfide-, selenide- and the new generation of telluride-based glasses, respectively. They cover the atmospheric transparency domains, 3-5 and 8-13 microm, respectively, at which the IR radiation can propagate allowing thermal imaging and night-vision operations through thick layers of atmosphere. The development of new glass compositions will be discussed on the basis of structural consideration with the objective of moulding low-cost lenses for IR cameras used, for instance, in car-driving assistance. Additionally, multimode, single-index, optical fibres operating in the 3 to 12 microm window developed for in situ remote evanescent-wave IR spectroscopy will also be mentioned. The detection of molecular IR signatures is applied to environmental monitoring for investigating the pollution of underground water with toxic molecules. The extension of this technique to the investigation of biomolecules in three different studies devoted to liver tissues analysis, bio-film formation, and cell metabolism will also be discussed. Finally we will mention the developments in the field of single-mode fibres operating around 10 mum for the Darwin space mission, which is aiming at discovering, signs of biological life in telluric earth-like exoplanets throughout

  17. Evolution and extinction in the marine realm: some constraints imposed by phytoplankton

    Science.gov (United States)

    Knoll, A. H.

    1989-01-01

    The organic and mineralized remains of planktonic algae provide a rich record of microplankton evolution extending over nearly half of the preserved geological record. In general, Phanerozoic patterns of phytoplankton radiation and extinction parallel those documented for skeletonized marine invertebrates, both augmenting and constraining thought about evolution in the oceans. Rapidly increasing knowledge of Proterozoic plankton is making possible the recognition of additional episodes of diversification and extinction that antedate the Ediacaran radiation of macroscopic animals. In contrast to earlier phytoplankton history, the late Mesozoic and Cainozoic record is documented in sufficient detail to constrain theories of mass extinction in more than a general way. Broad patterns of diversity change in planktonic algae show similarities across the Cretaceous-Tertiary and Eocene-Oligocene boundaries, but detailed comparisons of origination and extinction rates in calcareous nannoplankton, as well as other algae and skeletonized protozoans, suggest that the two episodes were quite distinct. Common causation appears unlikely, casting doubt on monolithic theories of mass extinction, whether periodic or not. Studies of mass extinction highlight a broader class of insights that paleontologists can contribute to evolutionary biology: the evaluation of evolutionary change in the context of evolving Earth-surface environments.

  18. Seabird guano enhances phytoplankton production in the Southern Ocean.

    Science.gov (United States)

    Shatova, Olga; Wing, Stephen; Hoffmann, Linn; Jack, Lucy; Gault-Ringold, Melanie

    2015-04-01

    Great congregations of seabirds in sub-Antarctic and Antarctic coastal areas result in delivery of nutrient-rich guano to marine ecosystems that potentially enhances productivity and supports biodiversity in the region. Guano-derived bio-available micronutrients and macronutrients might be utilized by marine phytoplankton for photosynthetic production, however, mechanisms and significance of guano fertilization in the Southern Ocean are largely understudied. Over austral summers of 2012 and 2013 we performed a series of guano-enrichment phytoplankton incubation experiments with water samples collected from three different water masses in the Southern Ocean: Antarctic waters of the Ross sea and sub-Antarctic waters offshore the Otago Peninsula, both showing iron limitation of phytoplankton productivity in summer, and in the subtropical frontal zone offshore from the Snares Islands, which is generally micronutrient-repleted. Samples were enriched with known concentrations of guano-derived nutrients. Phytoplankton biomass increased significantly in guano-treated samples during all three incubation experiments (7-10 fold increase), while remained low in control samples. This response indicates that seabird guano provides nutrients that limit primary production in the Southern Ocean and that these nutrients are readily taken up by phytoplankton. Guano additions were compared to Fe and Macronutrient treatments (both added in quantities similar to those in the guano treatment). Phytoplankton biomass increased significantly in response to the Macronutrient treatment in the subtropical frontal zone, however, the response had a smaller magnitude compared to the guano treatment (2.8 µgL-1 vs 5.2 µgL-1) ; there was no significant effect of Fe on phytoplankton growth. This suggests the potential importance of synergistic effects of nutrients in guano. Incubation with sub-Antarctic waters showed that Fe and Macronutrients might be equally important for enhancement of

  19. Sun, Earth and Sky

    CERN Document Server

    Lang, Kenneth R

    2006-01-01

    This Second Edition of Sun, Earth and Sky updates the popular text by providing comprehensive accounts of the most recent discoveries made by five modern solar spacecraft during the past decade. Their instruments have used sound waves to peer deep into the Sun’s inner regions and measure the temperature of its central nuclear reactor, and extended our gaze far from the visible Sun to record energetic outbursts that threaten Earth. Breakthrough observations with the underground Sudbury Neutrino Observatory are also included, which explain the new physics of ghostly neutrinos and solve the problematic mismatch between the predicted and observed amounts of solar neutrinos. This new edition of Sun, Earth and Sky also describes our recent understanding of how the Sun’s outer atmosphere is heated to a million degrees, and just where the Sun’s continuous winds come from. As humans we are more intimately linked with our life-sustaining Sun than with any other astronomical object, and the new edition therefore p...

  20. Impact of sea ice on the marine iron cycle and phytoplankton productivity

    Science.gov (United States)

    Wang, S.; Bailey, D.; Lindsay, K.; Moore, J. K.; Holland, M.

    2014-09-01

    Iron is a key nutrient for phytoplankton growth in the surface ocean. At high latitudes, the iron cycle is closely related to the dynamics of sea ice. In recent decades, Arctic sea ice cover has been declining rapidly and Antarctic sea ice has exhibited large regional trends. A significant reduction of sea ice in both hemispheres is projected in future climate scenarios. In order to adequately study the effect of sea ice on the polar iron cycle, sea ice bearing iron was incorporated in the Community Earth System Model (CESM). Sea ice acts as a reservoir for iron during winter and releases the trace metal to the surface ocean in spring and summer. Simulated iron concentrations in sea ice generally agree with observations in regions where iron concentrations are relatively low. The maximum iron concentrations simulated in Arctic and Antarctic sea ice are much lower than observed, which is likely due to underestimation of iron inputs to sea ice or missing mechanisms. The largest iron source to sea ice is suspended sediments, contributing fluxes of iron of 2.2 × 108 mol Fe month-1 in the Arctic and 4.1 × 106 mol Fe month-1 in the Southern Ocean during summer. As a result of the iron flux from ice, iron concentrations increase significantly in the Arctic. Iron released from melting ice increases phytoplankton production in spring and summer and shifts phytoplankton community composition in the Southern Ocean. Results for the period of 1998 to 2007 indicate that a reduction of sea ice in the Southern Ocean will have a negative influence on phytoplankton production. Iron transport by sea ice appears to be an important process bringing iron to the central Arctic. The impact of ice to ocean iron fluxes on marine ecosystems is negligible in the current Arctic Ocean, as iron is not typically the growth-limiting nutrient. However, it may become a more important factor in the future, particularly in the central Arctic, as iron concentrations will decrease with declining sea

  1. Infection of phytoplankton by aerosolized marine viruses.

    Science.gov (United States)

    Sharoni, Shlomit; Trainic, Miri; Schatz, Daniella; Lehahn, Yoav; Flores, Michel J; Bidle, Kay D; Ben-Dor, Shifra; Rudich, Yinon; Koren, Ilan; Vardi, Assaf

    2015-05-26

    Marine viruses constitute a major ecological and evolutionary driving force in the marine ecosystems. However, their dispersal mechanisms remain underexplored. Here we follow the dynamics of Emiliania huxleyi viruses (EhV) that infect the ubiquitous, bloom-forming phytoplankton E. huxleyi and show that EhV are emitted to the atmosphere as primary marine aerosols. Using a laboratory-based setup, we showed that the dynamic of EhV aerial emission is strongly coupled to the host-virus dynamic in the culture media. In addition, we recovered EhV DNA from atmospheric samples collected over an E. huxleyi bloom in the North Atlantic, providing evidence for aerosolization of marine viruses in their natural environment. Decay rate analysis in the laboratory revealed that aerosolized viruses can remain infective under meteorological conditions prevailing during E. huxleyi blooms in the ocean, allowing potential dispersal and infectivity over hundreds of kilometers. Based on the combined laboratory and in situ findings, we propose that atmospheric transport of EhV is an effective transmission mechanism for spreading viral infection over large areas in the ocean. This transmission mechanism may also have an important ecological impact on the large-scale host-virus "arms race" during bloom succession and consequently the turnover of carbon in the ocean.

  2. Phytoplankton community ecology: Principles applied in San Francisco Bay

    Science.gov (United States)

    Cloern, J.E.; Dufford, R.

    2005-01-01

    In his seminal 1961 paper 'The paradox of the plankton' Am Nat 95:137-147, G. E. Hutchinson asked why many species of phytoplankton can coexist while competing for a small number of limiting resources in an unstructured habitat. Hutchinson anticipated the resolution of his paradox, recognizing that communities are organized by processes beyond resource competition including species interactions, habitat variability and dispersal. Since 1961 we have made fundamental discoveries that have revolutionized our conceptual understanding of pelagic ecology, including (1) habitat heterogeneity at all scales relevant to plankton population dynamics, (2) community shifts in response to global climate cycles, (3) fast and selective predation as a powerful top-down force to shape phytoplankton communities, (4) turbulent mixing as a physical process that selects species on the basis of their size and form, (5) mixotrophy that allows some algal species to tap organic nutrient pools and function at multiple trophic levels, (6) taxon-specific life cycles including alternating vegetative and resting stages, and (7) the pelagic as an open system where communities are continually reshaped by species immigration. Here we synthesize these discoveries to show how they validate and amplify Hutchinson's hypothesis that phytoplankton communities are assembled by many processes. Our synthesis is built around observations of phytoplankton species composition from a decade of study in San Francisco Bay, used as a case study to illustrate the contemporary principles of phytoplankton community ecology. We apply these principles to address 2 central questions: (1) What processes assemble phytoplankton communities? (2) How does phytoplankton community composition influence ecosystem functions such as production in pelagic and benthic food webs?

  3. Dynamics of living phytoplankton: Implications for paleoenvironmental reconstructions

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, A B [Centre for Marine and Environmental Research (CIMA), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal)], E-mail: abarbosa@ualg.pt

    2009-01-01

    Phytoplankton is the dominant primary producer in aquatic ecosystems and is considered a gauge of ecological condition and change. Some phytoplankton groups, namely diatoms, dinoflagellates, and coccolithophores, produce morphological or chemical fossils that can be used for paleoenvironmental reconstruction. This study aims to review the processes that regulate dynamics in living phytoplankton and to highlight how this knowledge is used in paleoecological studies. The distribution patterns of phytoplankton in present-day aquatic ecosystems are shaped by the interplay between processes that regulate cell growth and cell death. Cell growth and cell death are regulated by the internal environment of phytoplankton (e.g., specific environmental tolerances, resource uptake properties, cell size, density and morphology, alternative nutritional strategies such as mixotrophy or N{sub 2} uptake, motility, intracellular storage capacities, grazing resistance properties), and by its external environment. The external environment includes variables dependent on the availability of resources (e.g., light intensity, concentration of CO{sub 2} and dissolved inorganic macronutrients and micronutrients, availability of living prey in case of mixotrophs) and variables independent of resources (e.g., temperature, salinity, turbulence, ultraviolet radiation, bioactive compounds, activity of grazers, viruses, and eukaryotic parasites). The importance of recently described loss processes, such as grazing by phagotrophic protists, viral lyses, and programmed cell death, is discussed in the context of its potential impact upon phytoplankton vertical fluxes. Examples of the use of different phytoplankton metrics (e.g. abundance, species composition, species morphology, and elemental composition) to infer contemporaneous as well as past environmental and ecological conditions are critically evaluated.

  4. Dynamics of living phytoplankton: Implications for paleoenvironmental reconstructions

    Science.gov (United States)

    Barbosa, A. B.

    2009-01-01

    Phytoplankton is the dominant primary producer in aquatic ecosystems and is considered a gauge of ecological condition and change. Some phytoplankton groups, namely diatoms, dinoflagellates, and coccolithophores, produce morphological or chemical fossils that can be used for paleoenvironmental reconstruction. This study aims to review the processes that regulate dynamics in living phytoplankton and to highlight how this knowledge is used in paleoecological studies. The distribution patterns of phytoplankton in present-day aquatic ecosystems are shaped by the interplay between processes that regulate cell growth and cell death. Cell growth and cell death are regulated by the internal environment of phytoplankton (e.g., specific environmental tolerances, resource uptake properties, cell size, density and morphology, alternative nutritional strategies such as mixotrophy or N2 uptake, motility, intracellular storage capacities, grazing resistance properties), and by its external environment. The external environment includes variables dependent on the availability of resources (e.g., light intensity, concentration of CO2 and dissolved inorganic macronutrients and micronutrients, availability of living prey in case of mixotrophs) and variables independent of resources (e.g., temperature, salinity, turbulence, ultraviolet radiation, bioactive compounds, activity of grazers, viruses, and eukaryotic parasites). The importance of recently described loss processes, such as grazing by phagotrophic protists, viral lyses, and programmed cell death, is discussed in the context of its potential impact upon phytoplankton vertical fluxes. Examples of the use of different phytoplankton metrics (e.g. abundance, species composition, species morphology, and elemental composition) to infer contemporaneous as well as past environmental and ecological conditions are critically evaluated.

  5. Phosphorus physiological ecology and molecular mechanisms in marine phytoplankton.

    Science.gov (United States)

    Lin, Senjie; Litaker, Richard Wayne; Sunda, William G

    2016-02-01

    Phosphorus (P) is an essential nutrient for marine phytoplankton and indeed all life forms. Current data show that P availability is growth-limiting in certain marine systems and can impact algal species composition. Available P occurs in marine waters as dissolved inorganic phosphate (primarily orthophosphate [Pi]) or as a myriad of dissolved organic phosphorus (DOP) compounds. Despite numerous studies on P physiology and ecology and increasing research on genomics in marine phytoplankton, there have been few attempts to synthesize information from these different disciplines. This paper is aimed to integrate the physiological and molecular information on the acquisition, utilization, and storage of P in marine phytoplankton and the strategies used by these organisms to acclimate and adapt to variations in P availability. Where applicable, we attempt to identify gaps in our current knowledge that warrant further research and examine possible metabolic pathways that might occur in phytoplankton from well-studied bacterial models. Physical and chemical limitations governing cellular P uptake are explored along with physiological and molecular mechanisms to adapt and acclimate to temporally and spatially varying P nutrient regimes. Topics covered include cellular Pi uptake and feedback regulation of uptake systems, enzymatic utilization of DOP, P acquisition by phagotrophy, P-limitation of phytoplankton growth in oceanic and coastal waters, and the role of P-limitation in regulating cell size and toxin levels in phytoplankton. Finally, we examine the role of P and other nutrients in the transition of phytoplankton communities from early succession species (diatoms) to late succession ones (e.g., dinoflagellates and haptophytes). © 2015 Phycological Society of America.

  6. Phytoplankton Assemblage Patterns in the Southern Mid-Atlantic Bight

    Science.gov (United States)

    Makinen, Carla; Moisan, Tiffany A. (Editor)

    2012-01-01

    As part of the Wallops Coastal Oceans Observing Laboratory (Wa-COOL) Project, we sampled a time-series transect in the southern Mid-Atlantic Bight (MAB) biweekly. Our 2-year time-series data included physical parameters, nutrient concentrations, and chlorophyll a concentrations. A detailed phytoplankton assemblage structure was examined in the second year. During the 2-year study, chlorophyll a concentration (and ocean color satellite imagery) indicated that phytoplankton blooms occurred in January/February during mixing conditions and in early autumn under stratified conditions. The chlorophyll a concentrations ranged from 0.25 microgram 1(exp -1) to 15.49 microgram 1(exp -1) during the 2-year period. We were able to discriminate approximately 116 different species under phase contrast microscopy. Dominant phytoplankton included Skeletonema costatum, Rhizosolenia spp., and Pseudo-nitzschia pungens. In an attempt to determine phytoplankton species competition/succession within the assemblage, we calculated a Shannon Weaver diversity index for our diatom microscopy data. Diatom diversity was greatest during the winter and minimal during the spring. Diatom diversity was also greater at nearshore stations than at offshore stations. Individual genera appeared patchy, with surface and subsurface patches appearing abruptly and persisting for only 1-2 months at a time. The distribution of individual species differed significantly from bulk variables of the assemblage (chlorophyll a ) and total phytoplankton assemblage (cells), which indicates that phytoplankton species may be limited in growth in ways that differ from those of the total assemblage. Our study demonstrated a highly diverse phytoplankton assemblage throughout the year, with opportunistic species dominating during spring and fall in response to seasonal changes in temperature and nutrients in the southern MAB.

  7. EPOXI EARTH OBS - MRI CALIBRATED IMAGES V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set set contains version 1.0 of calibrated 750-nm filter images of Earth acquired by the Deep Impact Medium Resolution Visible CCD during the EPOCh phase...

  8. EPOXI EARTH OBS - MRI CALIBRATED IMAGES V2.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This dataset contains calibrated, 750-nm filter images of Earth acquired by the Deep Impact Medium Resolution Visible CCD (MRI) during the EPOCh and Cruise 2 phases...

  9. EPOXI EARTH OBS - MRI RAW IMAGES V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set set contains version 1.0 of raw 750-nm filter images of Earth acquired by the Deep Impact Medium Resolution Visible CCD during the EPOCh phase of the...

  10. EPOXI EARTH OBS - HRIV CALIBRATED IMAGES V2.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains calibrated, narrow band filter images (350-950 nm) of Earth acquired by the Deep Impact High Resolution Visible CCD (HRIV) during the EPOCh...

  11. EPOXI EARTH OBS - HRIV RAW IMAGES V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set set contains version 1.0 of raw narrow band filter images (350-950 nm) of Earth acquired by the Deep Impact High Resolution Visible CCD during the...

  12. EPOXI EARTH OBS - HRIV CALIBRATED IMAGES V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set set contains version 1.0 of calibrated narrow band filter images (350-950 nm) of Earth acquired by the Deep Impact High Resolution Visible CCD during...

  13. ATST visible broadband imager

    Science.gov (United States)

    McBride, William R.; Wöger, Friedrich; Hegwer, Steve L.; Ferayorni, Andrew; Gregory, B. Scott

    2012-09-01

    The Advanced Technology Solar Telescope (ATST) is a 4 meter class telescope for observation of the solar atmosphere currently in the construction phase. The Visible Broadband Imager (VBI) is a diffraction limited imaging instrument planned to be the first-light instrument in the ATST instrumentation suite. The VBI is composed of two branches, the "VBI blue" and the "VBI red", and uses state-of-the-art narrow bandwidth interference filters and two custom designed high speed filter wheels to take bursts of images that will be re-constructed using a Graphics Processing Unit (GPU) optimized near-real-time speckle image reconstruction engine. At first light, the VBI instrument will produce diffraction-limited movies of solar activity at eight discrete wavelengths with a field of view of 2 arc minutes square. In this contribution, the VBI design team will discuss the capabilities of the VBI and describe the design of the instrument, highlighting the unique challenges faced in the development of this unique instrument.

  14. Digital Earth - A sustainable Earth

    Science.gov (United States)

    Mahavir

    2014-02-01

    All life, particularly human, cannot be sustainable, unless complimented with shelter, poverty reduction, provision of basic infrastructure and services, equal opportunities and social justice. Yet, in the context of cities, it is believed that they can accommodate more and more people, endlessly, regardless to their carrying capacity and increasing ecological footprint. The 'inclusion', for bringing more and more people in the purview of development is often limited to social and economic inclusion rather than spatial and ecological inclusion. Economic investment decisions are also not always supported with spatial planning decisions. Most planning for a sustainable Earth, be at a level of rural settlement, city, region, national or Global, fail on the capacity and capability fronts. In India, for example, out of some 8,000 towns and cities, Master Plans exist for only about 1,800. A chapter on sustainability or environment is neither statutorily compulsory nor a norm for these Master Plans. Geospatial technologies including Remote Sensing, GIS, Indian National Spatial Data Infrastructure (NSDI), Indian National Urban Information Systems (NUIS), Indian Environmental Information System (ENVIS), and Indian National GIS (NGIS), etc. have potential to map, analyse, visualize and take sustainable developmental decisions based on participatory social, economic and social inclusion. Sustainable Earth, at all scales, is a logical and natural outcome of a digitally mapped, conceived and planned Earth. Digital Earth, in fact, itself offers a platform to dovetail the ecological, social and economic considerations in transforming it into a sustainable Earth.

  15. Spatio-temporal organization of phytoplankton in Peipsi Lake

    Directory of Open Access Journals (Sweden)

    Sharov Andrey

    2016-12-01

    Full Text Available In the article, the results of the study of phytoplankton received at 16 stations of the Lake Peipsi in the spring (May, summer (August and autumn (October within the period of 2012–2015 were analyzed. 186 phytoplankton species were found. The list of mass taxa is given. It was noted that phytoplankton biomass had wide amplitude of annual average values in different lakes: Lake Peipsi/Chudskoe 2.1 ± 0.2 (0.3–23.0 mg / L; Lake Pihkva/Pskovskoe 5.4 ± 1.4 (0.4–34.0 mg / L and Lake Lämmijärv/Teploe 6.1 ± 1.2 (3.4–25.1 mg / l. According to species composition, structure and biomass of phytoplankton the lake belongs to the mesotrophic reservoirs with eutrophic features, as it was in previous years of observation. The water quality in the different parts of Lake Peipsi corresponded to conditionally pure water (1st quality class and slightly polluted one(2nd quality class. Correlation between characteristics of phytoplankton and the environmental factors (temperature, water level, transparency, N and P concentration in water was detected.

  16. Phytoplankton and Eutrophication Degree Assessment of Baiyangdian Lake Wetland, China

    Science.gov (United States)

    Wang, Xing; Wang, Yu; Liu, Lusan; Shu, Jianmin; Zhu, Yanzhong; Zhou, Juan

    2013-01-01

    Eight typical sampling sites were chosen to investigate the phytoplankton community structure and to assess the eutrophication degree of Baiyangdian Lake in 2009. Our results showed that among the total 133 species identified, Cyanophyta, Chlorophyta, and Bacillariophyta dominated the phytoplankton community. In spring, Chlorophyta and Bacillariophyta were the dominant phyla, and the dominant species included Chlorella sp., Chroomonas acuta Uterm., and Microcystis incerta Lemm.; the density of the phytoplankton ranged from 496 × 104 to 6256 × 104 cells/L with an average of 2384 × 104 cells/L. However, Chlorophyta and Cyanophyta became the dominant phyla in summer, and the dominant species were Chlorella sp., Leptolyngbya valderiana Anagn., and Nephrocytium agardhianum Nageli.; the density of the phytoplankton varied from 318 × 104 to 4630 × 104 cells/L with an average of 1785 × 104 cells/L. The density of the phytoplankton has increased significantly compared to the previous investigations in 2005. The index of Carlson nutritional status (TSIM) and the dominant genus assessment indicated that the majority of Baiyangdian Lake was in eutrophic state. PMID:23983633

  17. Phytoplankton assemblage of a solar saltern in Port Fouad, Egypt

    Directory of Open Access Journals (Sweden)

    Fedekar Fadel Madkour

    2012-11-01

    Full Text Available 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 between 33 species in the first pond (P1 and one species in the crystallizerpond (P5. Conversely, the total phytoplankton density, except that recordedin P1, increased significantly with rising salinity, fluctuating between 8.7 and56 × 105 individuals l-1 in P2 and P5 respectively. In spiteof the local variations in climate and nutrient availability, the phytoplankton composition, density and spatialvariations along the salinity gradient were, in many respects, very similar towhat has been observed in other solar saltworks. The pond with the lowest salinity(P1 - -1 was characterized by a significant diversity andblooming of diatoms and dinoflagellates. Intermediate salinity ponds (P2 andP3 with salinity ∼ 112-180 g l-1 exhibited a decline in bothspecies richness and density, but the stenohaline blue green algae (Synechocystis salina did flourish. The highly saline concentrating ponds andcrystallizers (P4 and P5 with salinity ∼ 223-340 g l-1 werecharacterized by few species, the disappearance of blue green algae and thethriving of the halotolerant green alga Dunaliella salina.

  18. Unexpected winter phytoplankton blooms in the North Atlantic subpolar gyre

    Science.gov (United States)

    Lacour, L.; Ardyna, M.; Stec, K. F.; Claustre, H.; Prieur, L.; Poteau, A.; D'Alcala, M. Ribera; Iudicone, D.

    2017-11-01

    In mid- and high-latitude oceans, winter surface cooling and strong winds drive turbulent mixing that carries phytoplankton to depths of several hundred metres, well below the sunlit layer. This downward mixing, in combination with low solar radiation, drastically limits phytoplankton growth during the winter, especially that of the diatoms and other species that are involved in seeding the spring bloom. Here we present observational evidence for widespread winter phytoplankton blooms in a large part of the North Atlantic subpolar gyre from autonomous profiling floats equipped with biogeochemical sensors. These blooms were triggered by intermittent restratification of the mixed layer when mixed-layer eddies led to a horizontal transport of lighter water over denser layers. Combining a bio-optical index with complementary chemotaxonomic and modelling approaches, we show that these restratification events increase phytoplankton residence time in the sunlight zone, resulting in greater light interception and the emergence of winter blooms. Restratification also caused a phytoplankton community shift from pico- and nanophytoplankton to phototrophic diatoms. We conclude that transient winter blooms can maintain active diatom populations throughout the winter months, directly seeding the spring bloom and potentially making a significant contribution to over-winter carbon export.

  19. Spatial variation of phytoplankton community structure in Daya Bay, China.

    Science.gov (United States)

    Jiang, Zhao-Yu; Wang, You-Shao; Cheng, Hao; Zhang, Jian-Dong; Fei, Jiao

    2015-10-01

    Daya Bay is one of the largest and most important gulfs in the southern coast of China, in the northern part of the South China Sea. The phylogenetic diversity and spatial distribution of phytoplankton from the Daya Bay surface water and the relationship with the in situ water environment were investigated by the clone library of the large subunit of ribulose-1, 5-bisphosphate carboxylase (rbcL) gene. The dominant species of phytoplankton were diatoms and eustigmatophytes, which accounted for 81.9 % of all the clones of the rbcL genes. Prymnesiophytes were widely spread and wide varieties lived in Daya Bay, whereas the quantity was limited. The community structure of phytoplankton was shaped by pH and salinity and the concentration of silicate, phosphorus and nitrite. The phytoplankton biomass was significantly positively affected by phosphorus and nitrite but negatively by salinity and pH. Therefore, the phytoplankton distribution and biomass from Daya Bay were doubly affected by anthropic activities and natural factors.

  20. Phytoplankton Growth and Microzooplankton Grazing in the Subtropical Northeast Atlantic

    Science.gov (United States)

    Cáceres, Carlos; Taboada, Fernando González; Höfer, Juan; Anadón, Ricardo

    2013-01-01

    Dilution experiments were performed to estimate phytoplankton growth and microzooplankton grazing rates during two Lagrangian surveys in inner and eastern locations of the Eastern North Atlantic Subtropical Gyre province (NAST-E). Our design included two phytoplankton size fractions (0.2–5 µm and >5 µm) and five depths, allowing us to characterize differences in growth and grazing rates between size fractions and depths, as well as to estimate vertically integrated measurements. Phytoplankton growth rates were high (0.11–1.60 d−1), especially in the case of the large fraction. Grazing rates were also high (0.15–1.29 d−1), suggesting high turnover rates within the phytoplankton community. The integrated balances between phytoplankton growth and grazing losses were close to zero, although deviations were detected at several depths. Also, O2 supersaturation was observed up to 110 m depth during both Lagrangian surveys. These results add up to increased evidence indicating an autotrophic metabolic balance in oceanic subtropical gyres. PMID:23935946

  1. Phytoplankton growth and microzooplankton grazing in the subtropical Northeast Atlantic.

    Directory of Open Access Journals (Sweden)

    Carlos Cáceres

    Full Text Available Dilution experiments were performed to estimate phytoplankton growth and microzooplankton grazing rates during two Lagrangian surveys in inner and eastern locations of the Eastern North Atlantic Subtropical Gyre province (NAST-E. Our design included two phytoplankton size fractions (0.2-5 µm and >5 µm and five depths, allowing us to characterize differences in growth and grazing rates between size fractions and depths, as well as to estimate vertically integrated measurements. Phytoplankton growth rates were high (0.11-1.60 d(-1, especially in the case of the large fraction. Grazing rates were also high (0.15-1.29 d(-1, suggesting high turnover rates within the phytoplankton community. The integrated balances between phytoplankton growth and grazing losses were close to zero, although deviations were detected at several depths. Also, O2 supersaturation was observed up to 110 m depth during both Lagrangian surveys. These results add up to increased evidence indicating an autotrophic metabolic balance in oceanic subtropical gyres.

  2. Iron, phytoplankton growth, and the carbon cycle.

    Science.gov (United States)

    Street, Joseph H; Paytan, Adina

    2005-01-01

    Iron is an essential nutrient for all living organisms. Iron is required for the synthesis of chlorophyll and of several photosynthetic electron transport proteins and for the reduction of CO2, SO4(2-), and NO3(-) during the photosynthetic production of organic compounds. Iron concentrations in vast areas of the ocean are very low (iron in oxic seawater. Low iron concentrations have been shown to limit primary production rates, biomass accumulation, and ecosystem structure in a variety of open-ocean environments, including the equatorial Pacific, the subarctic Pacific and the Southern Ocean and even in some coastal areas. Oceanic primary production, the transfer of carbon dioxide into organic carbon by photosynthetic plankton (phytoplankton), is one process by which atmospheric CO2 can be transferred to the deep ocean and sequestered for long periods of time. Accordingly, iron limitation of primary producers likely plays a major role in the global carbon cycle. It has been suggested that variations in oceanic primary productivity, spurred by changes in the deposition of iron in atmospheric dust, control atmospheric CO2 concentrations, and hence global climate, over glacial-interglacial timescales. A contemporary application of this "iron hypothesis" promotes the large-scale iron fertilization of ocean regions as a means of enhancing the ability of the ocean to store anthropogenic CO2 and mitigate 21st century climate change. Recent in situ iron enrichment experiments in the HNLC regions, however, cast doubt on the efficacy and advisability of iron fertilization schemes. The experiments have confirmed the role of iron in regulating primary productivity, but resulted in only small carbon export fluxes to the depths necessary for long-term sequestration. Above all, these experiments and other studies of iron biogeochemistry over the last two decades have begun to illustrate the great complexity of the ocean system. Attempts to engineer this system are likely to

  3. Photosynthetic characteristics of the phytoplankton in the Scheldt estuary: community and single-cell fluorescence measurements

    NARCIS (Netherlands)

    Dijkman, N.A.; Kromkamp, J.C.

    2006-01-01

    Estuaries present a very dynamic environment for phytoplankton with large changes in salinity occurring over relatively short distances, usually with high turbidity. We investigated the photosynthetic characteristics of phytoplankton in the Scheldt estuary (Belgium and the Netherlands) along a

  4. Iron released from ilmenite mineral sustains a phytoplankton community in microcosms

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, C.E.G.; Velip, D.; Mourya, B.S.; Shaikh, S.; Das, A.; LokaBharathi, P.A.

    ilmenite had significantly higher phytoplankton growth compared with controls containing no ilmenite or those containing only ferrous sulfate. Phytoplankton cell numbers in the ilmenite-supplemented treatment were 20X higher than in controls. The later...

  5. Upper ocean circulation modulation by phytoplankton concentration in the Equatorial Pacific and the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Nakamoto, S.; PrasannaKumar, S.; Oberhuber, J.M.; Sammarco, P.; Muneyama, K.; Sato, T.; AjoyKumar, A.; Frouin, R.

    brings nutrient-rich subsurface waters to the euphotic zone, thus the ocean currents supports perinnial phytoplankton bloom. The phytoplankton inhibits downward solar radiation penetration in the equatorial Pacific, resulting in cross equatorial density...

  6. Dust-induced episodic phytoplankton blooms in the Arabian Sea during winter monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Banerjee, P.; PrasannaKumar, S.

    to potential iron limitation. Although, all the phytoplankton blooms within CAS were observed following episodic dust events, only four blooms can be attributed to dust depositions. Our work shows that phytoplankton blooms fueled by episodic dust storms...

  7. Both phosphorus- and nitrogen limitation constrain viral proliferation in marine phytoplankton

    NARCIS (Netherlands)

    Maat, D.S.; Brussaard, C.P.D.

    2016-01-01

    Through cell lysis, viruses shape phytoplankton community composition and stimulatebiogeochemical cycling in the oceans. Earlier studies indicate that reduced phosphorus (P)availability can affect phytoplankton virus proliferation. The effects of nitrogen (N) availability areclaimed to be weaker

  8. Impact of the antifouling agent Irgarol 1051 on marine phytoplankton species

    NARCIS (Netherlands)

    Buma, Anita G. J.; Sjollema, Sascha B.; van de Poll, Willem H.; Klamer, Hans J. C.; Bakker, Joop F.

    In the present study we tested the hypothesis that environmental concentrations of the antifouling agent Irgarol 1051, as measured in coastal Western European waters, affect marine phytoplankton performance. The impact of Irgarol was investigated in the phytoplankton species Thalassiosira

  9. Phytoplankton assemblages and pigments in the exclusive economic zone of Mauritius (Indian Ocean)

    Digital Repository Service at National Institute of Oceanography (India)

    Devassy; Goes, J.I.

    curtailed phytoplankton growth in the surface waters leading to formation of a distinct subsurface chlorophyll maximum (SCM). In the vicinity of Agalega Islands, the enhancement of phytoplankton biomass was associated with an upwelling process causEd...

  10. A model for which toxic and non-toxic phytoplankton are indistinguishable by the zooplantkon

    Science.gov (United States)

    Sen, Moitri; Venturino, Ezio

    2012-09-01

    Using Haldane-Monod functions, we study the response of zooplankton avoiding to feed on phytoplankton when the latter releases toxines, but assuming that the zooplankton does not distinguish between toxic and non-toxic phytoplankton.

  11. Oceanic and atmospheric influences on the variability of phytoplankton bloom in the southwestern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Raj, R.P.; Peter, B.N.; Pushpadas, D.

    The phytoplankton bloom developed in the southwestern Indian Ocean during austral summer is unique in its occurrence. Interannual and intraannual variability of this large phytoplankton bloom were studied using satellite derived, model...

  12. DYNAMICALLY MAINTAINING THE VISIBILITY GRAPH

    NARCIS (Netherlands)

    VEGTER, G

    1991-01-01

    An algorithm is presented to maintain the visibility graph of a set of N line segments in the plane in O(log2 N + K log N) time, where K is the total number of arcs of the visibility graph that are destroyed or created upon insertion or deletion of a line segment. The line segments should be

  13. Revisiting visibility in the plane

    DEFF Research Database (Denmark)

    Wilkinson, Bryan Thomas

    Abstract We consider two closely related problems: computing the region visible from a point amid simple polygonal obstacles and computing the lower envelope of a set of disjoint segments. Visibility problems such as these were proposed and promptly solved in the late'80s and early'90s before...

  14. Non-Euclidean visibility problems

    Indian Academy of Sciences (India)

    We prove a visibility criterion and study orchard problem and the cardinality of visible points in large circles. Author Affiliations. Fernando Chamizo1. Departamento de Matemáticas, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain. Dates. Manuscript received: 14 November 2005. Proceedings ...

  15. Visualizing Earth Materials

    Science.gov (United States)

    Cashman, K. V.; Rust, A.; Stibbon, E.; Harris, R.

    2016-12-01

    Earth materials are fundamental to art. They are pigments, they are clay, they provide form and color. Earth scientists, however, rarely attempt to make the physical properties of Earth materials visible through art, and similarly many artists use Earth materials without fully understanding their physical and chemical properties. Here we explore the intersection between art and science through study of the physical properties of Earth materials as characterized in the laboratory, and as transferred to paper using different techniques and suspending media. One focus of this collaboration is volcanic ash. Ash is interesting scientifically because its form provides information on the fundamental processes that drive volcanic eruptions, and determines its transport properties, and thus its potential to affect populations far downwind of the volcano. Ash properties also affect its behavior as an art material. From an aesthetic point of view, ash lends a granular surface to the image; it is also uncontrollable, and thus requires engagement between artist and medium. More fundamentally, using ash in art creates an exchange between the medium and the subject matter, and imparts something of the physical, visceral experience of volcanic landscapes to the viewer. Another component of this work uses powdered rock as a printing medium for geologic maps. Because different types of rock create powders with different properties (grain size distributions and shapes), the geology is communicated not only as color, but also by the physical characteristics of the material as it interacts with the paper. More importantly, the use of actual rocks samples as printing material for geologic maps not only makes a direct connection between the map and the material it represents, but also provides an emotional connection between the map, the viewer and the landscape, its colors, textures and geological juxtapositions. Both case studies provide examples not only of ways in which artists can

  16. Earth as an extrasolar planet: Earth model validation using EPOXI earth observations.

    Science.gov (United States)

    Robinson, Tyler D; Meadows, Victoria S; Crisp, David; Deming, Drake; A'hearn, Michael F; Charbonneau, David; Livengood, Timothy A; Seager, Sara; Barry, Richard K; Hearty, Thomas; Hewagama, Tilak; Lisse, Carey M; McFadden, Lucy A; Wellnitz, Dennis D

    2011-06-01

    The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric and moderate resolution near-infrared (NIR) spectroscopic observations of Earth. These remote observations provide a rigorous validation of whole-disk Earth model simulations used to better understand remotely detectable extrasolar planet characteristics. We have used these data to upgrade, correct, and validate the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional line-by-line, multiple-scattering spectral Earth model. This comprehensive model now includes specular reflectance from the ocean and explicitly includes atmospheric effects such as Rayleigh scattering, gas absorption, and temperature structure. We have used this model to generate spatially and temporally resolved synthetic spectra and images of Earth for the dates of EPOXI observation. Model parameters were varied to yield an optimum fit to the data. We found that a minimum spatial resolution of ∼100 pixels on the visible disk, and four categories of water clouds, which were defined by using observed cloud positions and optical thicknesses, were needed to yield acceptable fits. The validated model provides a simultaneous fit to Earth's lightcurve, absolute brightness, and spectral data, with a root-mean-square (RMS) error of typically less than 3% for the multiwavelength lightcurves and residuals of ∼10% for the absolute brightness throughout the visible and NIR spectral range. We have extended our validation into the mid-infrared by comparing the model to high spectral resolution observations of Earth from the Atmospheric Infrared Sounder, obtaining a fit with residuals of ∼7% and brightness temperature errors of less than 1 K in the atmospheric window. For the purpose of understanding the observable characteristics of the distant Earth at arbitrary viewing geometry and observing cadence, our validated forward model can be

  17. Using Bio-Optics to Reveal Phytoplankton Physiology from a Wirewalker Autonomous Platform

    Science.gov (United States)

    Omand, M. M.; Cetinic, I.; Lucas, A. J.

    2017-01-01

    Rapid, wave-powered profiling of bio-optical properties from an autonomous Wirewalker platform provides useful insights into phytoplankton physiology, including the patterns of diel growth, phytoplankton mortality, nonphotochemical quenching of chlorophyll a fluorescence, and natural (sun-induced) fluorescence of mixed communities. Methods are proposed to quantify each of these processes. Such autonomous measurements of phytoplankton physiological rates and responses open up new possibilities for studying phytoplankton in situ, over longer periods, and under a broader range of environmental conditions.

  18. 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...... and theoretical ways to predict different phytoplankton responses to global change. Using phytoplankton ecological niches to predict their responses to multiple environmental stressors is a promising new approach. Functional traits of phytoplankton, such as resource utilization traits and tolerance curves...

  19. Phytoplankton dynamics in relation to environmental changes in a phytoplankton-dominated Mediterranean lagoon (Cabras Lagoon, Italy

    Directory of Open Access Journals (Sweden)

    B.M. Padedda

    2012-09-01

    Full Text Available In Mediterranean lagoons, macrophytes often surpass phytoplankton as the most important primary producers. Less frequently, phytoplankton dominates throughout the year, thus knowledge of its dynamics is relatively limited and scattered. In this study, we assessed over two years the dynamics of phytoplankton assemblages, including potential harmful algal species (HAS, in relation to environmental changes in the phytoplankton-dominated Cabras Lagoon (Sardinia, Italy. The lagoon was characterised by uniform spatial conditions, wide temporal variations in salinity (40 PSU and high nutrient availability. Phosphorus was highest in summer, possibly recycled within the system, while dissolved inorganic nitrogen increased in winter and spring due to watershed discharge. Chlorophyll a, positively correlated with nutrients and rainfall, showed a typical bimodal pattern with summer-winter blooms. Modifications in phytoplankton composition strongly correlated with extreme weather events, such as intense rainfall. This generated an abrupt salinity decrease that, combined with high nutrient availability, favoured the dominance of Cyanophyceae of reduced cell size, such as Cyanobium and Rhabdoderma species. We suggest that the prolonged and intense dominance of Cyanophyceae, added to other HAS, has a negative impact on the primary economic activities of the lagoon, such as fishery, and generally on the whole lagoon functioning.

  20. Phytoplankton defence mechanisms: traits and trade-offs

    DEFF Research Database (Denmark)

    Pančić, Marina; Kiørboe, Thomas

    2018-01-01

    In aquatic ecosystems, unicellular algae form the basis of the food webs. Theoretical and experimental studies have demonstrated that one of the mechanisms that maintain high diversity of phytoplankton is through predation and the consequent evolution of defence mechanisms. Proposed defence...... mechanisms in phytoplankton are diverse and include physiological (e.g. toxicity, bioluminescence), morphological (e.g. silica shell, colony formation), and behavioural (e.g. escape response) traits. However, the function of many of the proposed defence mechanisms remains elusive, and the costs and benefits...... (trade-offs) are often unquantified or undocumented. Here, we provide an overview of suggested phytoplankton defensive traits and review their experimental support. Wherever possible we quantify the trade-offs from experimental evidence and theoretical considerations. In many instances, experimental...

  1. 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...... 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...

  2. Subsurface phytoplankton blooms fuel pelagic production in the North Sea

    DEFF Research Database (Denmark)

    Richardson, Kathrine; Visser, Andre; Pedersen, Flemming

    2000-01-01

    The seasonal phytoplankton biomass distribution pattern in stratified temperate marine waters is traditionally depicted as consisting of spring and autumn blooms. The energy source supporting pelagic summer production is believed to be the spring bloom. However, the spring bloom disappears...... relatively quickly from the water column and a large proportion of the material sedimenting to the bottom following the spring bloom is often comprised of intact phytoplankton cells. Thus, it is easy to argue that the spring bloom is fueling the energy demands of the benthos, but more difficult to argue...... convincingly that energy fixed during the spring bloom is fueling the pelagic production occurring during summer months. We argue here that periodic phytoplankton blooms are occurring during the summer in the North Sea at depths of >25 m and that the accumulated new production [sensu (Dugdale and Goering...

  3. 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

  4. Seasonal dynamics of phytoplankton community in a tropical wetland.

    Science.gov (United States)

    Bhat, Najeeb Ahmad; Wanganeo, Ashwani; Raina, Rajni

    2015-01-01

    Phytoplankton species composition and seasonal changes were investigated in the Bhoj wetland Bhopal. Taxonomic composition, diversity, and abundance of phytoplankton were studied at nine stations from March 2008 to February 2010, in relation to various physico-chemical factors. Total phytoplankton species composition in the Bhoj wetland was represented by 360 species. Among phytoplankton, diversity belonged to seven groups. Chlorophyceae was the dominant group (48%) followed by Bacillariophyceae (26%), Cyanophyceae (15%), and Euglenophyceae (9%), while Pyrophyceae, Chrysophyceae, and Xanthophyceae contributed 2% of the population. Phytoplankton on the basis of seasonal studies recorded 1651 units l(-1) during summer season which was contributed mainly by Chlorophyceae (39.3%), with Spirogyra sp. (14.2%) and Closteriopsis sp. (9.1%) contributing maximum to the total group in the first year, while during the second year of summer period, a total of 2095 units l(-1) was recorded which was contributed mainly by group Pyrophyceae (51%) with the main dominant species represented by Ceratium hirundinella (98.46%). The highest Shannon-Wiener diversity index (H') value (4.27) was recorded. Simpson values are approaching 1, signifying that sites have high relative diversity due to its supporting surrounding components. The trend of variation in evenness values was more or less the same as Shannon diversity index. Thus, the highest diversity indices recoded at all the stations in the present study justify the diverse nature of species inhabiting the different ecological niches in the ecosystem. The very high phosphate and nitrate concentrations in the wetland are indicators of pollution which may be due to the discharge of agricultural and sewage wastes enriched with nutrients as well as the human activities there. Our recommendation is to avoid as far as possible the discharge of sewage and agriculture wastes into the Bhoj wetland. The effects of various physicochemical

  5. Ammonium uptake by phytoplankton regulates nitrification in the sunlit ocean.

    Directory of Open Access Journals (Sweden)

    Jason M Smith

    Full Text Available Nitrification, the microbial oxidation of ammonium to nitrate, is a central part of the nitrogen cycle. In the ocean's surface layer, the process alters the distribution of inorganic nitrogen species available to phytoplankton and produces nitrous oxide. A widely held idea among oceanographers is that nitrification is inhibited by light in the ocean. However, recent evidence that the primary organisms involved in nitrification, the ammonia-oxidizing archaea (AOA, are present and active throughout the surface ocean has challenged this idea. Here we show, through field experiments coupling molecular genetic and biogeochemical approaches, that competition for ammonium with phytoplankton is the strongest regulator of nitrification in the photic zone. During multiday experiments at high irradiance a single ecotype of AOA remained active in the presence of rapidly growing phytoplankton. Over the course of this three day experiment, variability in the intensity of competition with phytoplankton caused nitrification rates to decline from those typical of the lower photic zone (60 nmol L-1 d-1 to those in well-lit layers (<1 nmol L-1 d-1. During another set of experiments, nitrification rates exhibited a diel periodicity throughout much of the photic zone, with the highest rates occurring at night when competition with phytoplankton is lowest. Together, the results of our experiments indicate that nitrification rates in the photic zone are more strongly regulated by competition with phytoplankton for ammonium than they are by light itself. This finding advances our ability to model the impact of nitrification on estimates of new primary production, and emphasizes the need to more strongly consider the effects of organismal interactions on nutrient standing stocks and biogeochemical cycling in the surface of the ocean.

  6. PHYTOPLANKTON COMPOSITION IN FISH FARMS ALONG THE EASTERN ADRIATIC COAST

    Directory of Open Access Journals (Sweden)

    Marija Tomec

    2006-10-01

    Full Text Available Investigations of net phytoplankton composition were performed at three fish farms situated at the northern, middle and southern part of the eastern Adriatic Sea coast, respectively. In the northern part investigations were conducted in the Limski kanal, in the middle part at the Ugljan island and in the southern part in the place Drače on the Pelješac peninsula (Figure 1. At all three localities fish culture included mostly two species: gilthead sea bream (Sparus aurata and sea bass (Dicentrarchus labrax. Beside some physico–chemical parameters (sea water temperature, salinity special attention was placed on the examination of qualitative net phytoplankton composition, which was conducted in the period of May and November 2004 and May and October 2005. Samples were collected at the depths of 0. 5 and 4 meters. According to the physico–chemical parameters, sea water temperature was influenced by the temperature of the environment. Qualitative net phytoplankton composition consisted of 153 microphytic species belonging to the systematic compartments of Cyanobacteria, Chrysophyta and Dinophyta (Table 1. The most numerous algal group were diatoms or Bacillarophyceae (84 species or 55% with relative frequencies of species from 1 to 7. Taxonomic composition of diatoms showed the community Chaetoceros–Rhizosolenia (Proboscia as the dominant one. The second numerically most dominant compartment were Dinophyta (62 species or 401% with dominant the species of the genera Ceratium and Protoperidinium. Relative frequencies of species was ranging from 1 to 7 (mass presence of specimens in the water column. From Cyanobacteria (4 species or 3%, only filamentous algae were determined, with individual presence in net phytoplankton composition. Qualitative net phytoplankton composition suggests the similarity of species composition in the water column at all investigated fish farms. From the obtained characteristics of net phytoplankton composition

  7. Remote sensing observations of phytoplankton increases triggered by successive typhoons

    Science.gov (United States)

    Huang, Lei; Zhao, Hui; Pan, Jiayi; Devlin, Adam

    2017-12-01

    Phytoplankton blooms in the Western North Pacific, triggered by two successive typhoons with different intensities and translation speeds under different pre-existing oceanic conditions, were observed and analyzed using remotely sensed chlorophyll-a (Chl-a), sea surface temperature (SST), and sea surface height anomaly (SSHA) data, as well as typhoon parameters and CTD (conductivity, temperature, and depth) profiles. Typhoon Sinlaku, with relatively weaker intensity and slower translation speed, induced a stronger phytoplankton bloom than Jangmi with stronger intensity and faster translation speed (Chl-a>0.18 mg·m‒3 versus Chl-aphytoplankton blooms in the study area. Pre-existing cyclonic circulations provided a relatively unstable thermodynamic structure for Sinlaku, and therefore cold water with rich nutrients could be brought up easily. The mixed-layer deepening caused by Typhoon Sinlaku, which occurred first, could have triggered an unfavorable condition for the phytoplankton bloom induced by Typhoon Jangmi which followed afterwards. The sea surface temperature cooling by Jangmi was suppressed due to the presence of the thick upper-ocean mixed-layer, which prevented the deeper cold water from being entrained into the upper-ocean mixed layer, leading to a weaker phytoplankton augment. The present study suggests that both wind (including typhoon translation speed and intensity) and pre-existing conditions (e.g., mixed-layer depths, eddies, and nutrients) play important roles in the strong phytoplankton bloom, and are responsible for the stronger phytoplankton bloom after Sinlaku's passage than that after Jangmi's passage. A new typhoon-influencing parameter is introduced that combines the effects of the typhoon forcing (including the typhoon intensity and translation speed) and the oceanic pre-condition. This parameter shows that the forcing effect of Sinlaku was stronger than that of Jangmi.

  8. Ammonium uptake by phytoplankton regulates nitrification in the sunlit ocean.

    Science.gov (United States)

    Smith, Jason M; Chavez, Francisco P; Francis, Christopher A

    2014-01-01

    Nitrification, the microbial oxidation of ammonium to nitrate, is a central part of the nitrogen cycle. In the ocean's surface layer, the process alters the distribution of inorganic nitrogen species available to phytoplankton and produces nitrous oxide. A widely held idea among oceanographers is that nitrification is inhibited by light in the ocean. However, recent evidence that the primary organisms involved in nitrification, the ammonia-oxidizing archaea (AOA), are present and active throughout the surface ocean has challenged this idea. Here we show, through field experiments coupling molecular genetic and biogeochemical approaches, that competition for ammonium with phytoplankton is the strongest regulator of nitrification in the photic zone. During multiday experiments at high irradiance a single ecotype of AOA remained active in the presence of rapidly growing phytoplankton. Over the course of this three day experiment, variability in the intensity of competition with phytoplankton caused nitrification rates to decline from those typical of the lower photic zone (60 nmol L-1 d-1) to those in well-lit layers (nitrification rates exhibited a diel periodicity throughout much of the photic zone, with the highest rates occurring at night when competition with phytoplankton is lowest. Together, the results of our experiments indicate that nitrification rates in the photic zone are more strongly regulated by competition with phytoplankton for ammonium than they are by light itself. This finding advances our ability to model the impact of nitrification on estimates of new primary production, and emphasizes the need to more strongly consider the effects of organismal interactions on nutrient standing stocks and biogeochemical cycling in the surface of the ocean.

  9. Mercury methylation and bacterial activity associated to tropical phytoplankton

    Energy Technology Data Exchange (ETDEWEB)

    Coelho-Souza, Sergio A. [Laboratorio de Tracadores Wolfgang Pfeiffer, SL 62, Instituto de Biofisica Carlos Chagas Filho, Bloco G, Ilha do Fundao, Universidade Federal do Rio de Janeiro (IBCCF/UFRJ), RJ, CEP 21949-900 (Brazil); Guimaraes, Jean R.D. [Laboratorio de Tracadores Wolfgang Pfeiffer, SL 62, Instituto de Biofisica Carlos Chagas Filho, Bloco G, Ilha do Fundao, Universidade Federal do Rio de Janeiro (IBCCF/UFRJ), RJ, CEP 21949-900 (Brazil)]. E-mail: jeanrdg@biof.ufrj.br; Mauro, Jane B.N. [Laboratorio de Tracadores Wolfgang Pfeiffer, SL 62, Instituto de Biofisica Carlos Chagas Filho, Bloco G, Ilha do Fundao, Universidade Federal do Rio de Janeiro (IBCCF/UFRJ), RJ, CEP 21949-900 (Brazil); Miranda, Marcio R. [Laboratorio de Tracadores Wolfgang Pfeiffer, SL 62, Instituto de Biofisica Carlos Chagas Filho, Bloco G, Ilha do Fundao, Universidade Federal do Rio de Janeiro (IBCCF/UFRJ), RJ, CEP 21949-900 (Brazil); Azevedo, Sandra M.F.O. [Laboratorio de Ecofisiologia e Toxicologia de Cianobacterias, IBCCF/UFRJ, RJ (Brazil)

    2006-07-01

    The methylated form of mercury (Hg), methylmercury (MeHg), is one of the most toxic pollutants. Biotic and/or abiotic methylation, often associated to sulfate-reducing bacteria metabolism, occurs in aquatic environments and in many tropical areas, mostly in the periphyton associated to floating macrophyte roots. Data about mercury methylation by phytoplankton are scarce and the aim of this study was to verify the biotic influence in the methylation process in Microcystis aeruginosa and Sineccocystis sp. laboratory strains and in natural populations of phytoplankton from two different aquatic systems, the mesotrophic Ribeirao das Lajes reservoir and hypereutrophic oligohaline Jacarepagua lagoon, Rio de Janeiro state, Brazil. Adapted radiochemical techniques were used to measure sulfate-reduction, mercury methylation and bacterial activity in phytoplankton samples. Methyl-{sup 203}Hg formation from added inorganic {sup 203}Hg and {sup 3}H-Leucine uptake were measured by liquid scintillation as well as sulfate-reduction, estimated as H{sub 2} {sup 35}S produced from added Na{sub 2} {sup 35}SO{sub 4}. There was no significant difference in low methylation potentials (0.37%) among the two cyanobacterium species studied in laboratory conditions. At Ribeirao das Lajes reservoir, there was no significant difference in methylation, bacterial activity and sulfate-reduction of surface sediment between the sampling points. Methylation in sediments (3-4%) was higher than in phytoplankton (1.5%), the opposite being true for bacterial activity (sediment mean 6.6 against 150.3 nmol gdw{sup -1} h{sup -1} for phytoplankton samples). At Jacarepagua lagoon, an expressive bacterial activity (477.1 x 10{sup 3} nmol gdw{sup -1} h{sup -1} at a concentration of 1000 nM leucine) and sulfate-reduction ({approx}21% H{sub 2} {sup 35}S trapped) associated to phytoplankton (mostly cyanobacteria M. aeruginosa) was observed, but mercury methylation was not detected.

  10. Fine-scale responses of phytoplankton to freshwater influx in a ...

    Indian Academy of Sciences (India)

    easy access as NIO's coastal research vessel CRV. Sagar Shukti which .... the percentages of Diatom and Dinoflagellate populations,. (b) of the total number of phytoplankton genera and the total number of phytoplankton species, and (c) of the diver- sity index of Diatom, Dinoflagellate and total phytoplankton population.

  11. Simulation of three-dimensional phytoplankton dynamics: competition in light-limited environments

    NARCIS (Netherlands)

    Pham Thi, N.N.; Huisman, J.; Sommeijer, B.P.

    2005-01-01

    In this paper, we develop computational methods for a three-dimensional model of competition for light between phytoplankton species. The competing phytoplankton populations are exposed to both horizontal and vertical mixing. The vertical light-dependence of phytoplankton photosynthesis implies that

  12. Seasonal variations of group-specific phytoplankton cell death in Xiamen Bay, China

    Science.gov (United States)

    Huang, Xiaozhou; Liu, Xin; Chen, Jixin; Xiao, Wupeng; Cao, Zhen; Huang, Bangqin

    2017-03-01

    The importance of phytoplankton cell death is being increasingly recognized, however, there are still no published reports on this in Xiamen Bay. In this study, the proportion of dead phytoplankton cells associated with environmental factors was assessed at a station in Xiamen Bay from December 2012 to December 2013, using a cell digestion assay, which is an effective method to analyze dead/ living cells in complex natural phytoplankton communities. The percentages of dead cells (% DC) in the total phytoplankton in summer (16%±6%) were lower than those in winter (27%±16%). Six groups of phytoplankton (G1-G6) were categorized by flow cytometry. These phytoplankton communities with diverse seasonal variations in % DC had different responses to environmental constraints. The main factors affecting mortality were temperature and salinity, while nutrient concentration showed little influence on phytoplankton death. Additionally, our results provide evidence that chlorophyll a concentrations had an inverse relationship with total phytoplankton % DC and viable cell abundance was more meaningful than total cells to explain variations in environmental parameters (such as Chl a). Moreover, the lowest mean % DC in total phytoplankton was 16%±6% at our sample site, which is in a subtropical area with high water temperatures, full solar radiation, and rich nutrients. This indicates that phytoplankton cell death is a process that cannot be ignored. In summary, phytoplankton cell death is important in understanding the dynamics of phytoplankton communities and the functioning of subtropical ecosystems.

  13. 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.

  14. Do marine phytoplankton follow Bergmann's rule sensu lato?

    Science.gov (United States)

    Sommer, Ulrich; Peter, Kalista H; Genitsaris, Savvas; Moustaka-Gouni, Maria

    2017-05-01

    Global warming has revitalized interest in the relationship between body size and temperature, proposed by Bergmann's rule 150 years ago, one of the oldest manifestations of a 'biogeography of traits'. We review biogeographic evidence, results from clonal cultures and recent micro- and mesocosm experiments with naturally mixed phytoplankton communities regarding the response of phytoplankton body size to temperature, either as a single factor or in combination with other factors such as grazing, nutrient limitation, and ocean acidification. Where possible, we also focus on the comparison between intraspecific size shifts and size shifts resulting from changes in species composition. Taken together, biogeographic evidence, community-level experiments and single-species experiments indicate that phytoplankton average cell sizes tend to become smaller in warmer waters, although temperature is not necessarily the proximate environmental factor driving size shifts. Indirect effects via nutrient supply and grazing are important and often dominate. In a substantial proportion of field studies, resource availability is seen as the only factor of relevance. Interspecific size effects are greater than intraspecific effects. Direct temperature effects tend to be exacerbated by indirect ones, if warming leads to intensified nutrient limitation or copepod grazing while ocean acidification tends to counteract the temperature effect on cell size in non-calcifying phytoplankton. We discuss the implications of the temperature-related size trends in a global-warming context, based on known functional traits associated with phytoplankton size. These are a higher affinity for nutrients of smaller cells, highest maximal growth rates of moderately small phytoplankton (ca. 10 2  µm 3 ), size-related sensitivities for different types of grazers, and impacts on sinking rates. For a phytoplankton community increasingly dominated by smaller algae we predict that: (i) a higher proportion

  15. On characterizing terrain visibility graphs

    Directory of Open Access Journals (Sweden)

    William Evans

    2015-06-01

    Full Text Available A terrain is an $x$-monotone polygonal line in the $xy$-plane. Two vertices of a terrain are mutually visible if and only if there is no terrain vertex on or above the open line segment connecting them. A graph whose vertices represent terrain vertices and whose edges represent mutually visible pairs of terrain vertices is called a terrain visibility graph. We would like to find properties that are both necessary and sufficient for a graph to be a terrain visibility graph; that is, we would like to characterize terrain visibility graphs.Abello et al. [Discrete and Computational Geometry, 14(3:331--358, 1995] showed that all terrain visibility graphs are “persistent”. They showed that the visibility information of a terrain point set implies some ordering requirements on the slopes of the lines connecting pairs of points in any realization, and as a step towards showing sufficiency, they proved that for any persistent graph $M$ there is a total order on the slopes of the (pseudo lines in a generalized configuration of points whose visibility graph is $M$.We give a much simpler proof of this result by establishing an orientation to every triple of vertices, reflecting some slope ordering requirements that are consistent with $M$ being the visibility graph, and prove that these requirements form a partial order. We give a faster algorithm to construct a total order on the slopes. Our approach attempts to clarify the implications of the graph theoretic properties on the ordering of the slopes, and may be interpreted as defining properties on an underlying oriented matroid that we show is a restricted type of $3$-signotope.

  16. Automated, in-water determination of colored dissolved organic material and phytoplankton community structure using the optical phytoplankton discriminator

    Science.gov (United States)

    Kirkpatrick, Gary J.; Millie, David F.; Moline, Mark A.; Lohrenz, Steven E.; Schofield, Oscar M.

    2011-06-01

    Optical Phytoplankton Discriminator (OPD, a.k.a. BreveBuster) determines colored dissolved organic material (CDOM) absorption spectra and particulate light absorbance spectra. The CDOM absorption spectra and correlation coefficients (referred to as 'similarity indexes') between the particulate absorbance spectra and known phytoplankton classes are available in real-time. Post-deployment processing calculates the best fit of multiple absorbance spectra from known phytoplankton taxonomic classes. Through this process the OPD provides an estimate of the phytoplankton community chlorophyll distribution among the classes included in the fit process. The major components of the OPD include: a liquid-waveguide capillary cell (LWCC), a fiber-optic spectrometer, a tungsten-deuterium fiber-optic light and a 0.2 micrometer pore cross-flow filter. In-water operation of the OPD began in May 2003. Since that date 25 of these instruments have been deployed on a variety of autonomous underwater vehicles, buoys, piers, channel markers and boats and ships. It has been utilized in CDOM studies off the New Jersey coast, in HAB monitoring efforts in the Gulf of Mexico and the Great Lakes, and in phytoplankton community structure studies in the Galapagos Islands and the Mediterranean Sea. Most recently, it has been deployed to Veracruz, Mexico for HAB monitoring. Presently, several OPD's operating on Slocum gliders and coastal buoys make up a local HAB observatory south of Tampa Bay, Florida, partially supported by the NOAA/IOOS through GCOOS. This presentation will detail the OPD's capabilities and report results from several of the deployments listed above. The ongoing effort to effectively visualize 4-D phytoplankton community structure will be discussed.

  17. SCOR Working Group 137: "Global Patterns of Phytoplankton Dynamics in Coastal Ecosystems": An introduction to the special issue of Estuarine, Coastal and Shelf Science

    Science.gov (United States)

    Paerl, Hans W.; Yin, Kedong; O'Brien, Todd D.

    2015-09-01

    Phytoplankton form the base of most aquatic food webs and play a central role in assimilation and processing of carbon and nutrients, including nitrogen, phosphorus, silicon, iron and a wide range of trace elements (Reynolds, 2006). In the marine environment, estuarine and coastal ecosystems (jointly termed coastal here) are among the most productive, resourceful and dynamic habitats on Earth (Malone et al., 1999; Day et al., 2012). These ecosystems constitute only ∼10% of the global oceans' surface, but account for over 30% of its primary production (Day et al., 2012). They process vast amounts of nutrients, sediments, carbonaceous, and xenobiotic compounds generated in coastal watersheds, in which approximately 70% of the world's human population resides (Nixon, 1995; Vitousek et al., 1997; NOAA, 2013). Estuarine and coastal ecosystems are also strongly influenced by localized nutrient enrichment from coastal upwelling, with major impacts on the structure and function of phytoplankton communities and the food webs they support (Legendre and Rassoulzadegan, 2012; Paerl and Justić, 2012). In addition, introductions and invasions of exotic plant and animal species have led to significant "top down" mediated changes in phytoplankton community structure and function (Carlton, 1999; Thompson, 2005). Lastly, the coastal zone is the "front line" of climatically-induced environmental change, including warming, altered rainfall patterns, intensities and magnitudes (Trenberth, 2005; IPCC, 2012), which jointly impact phytoplankton community structure and function (Cloern and Jassby, 2012; Hall et al., 2013). The combined effects of these pressures translate into a myriad of changes in phytoplankton production and community structure along geomorphological and geographic gradients (Fig. 1), with cascading quantitative and qualitative impacts on biogeochemical cycling, food web structure and function, water quality and overall resourcefulness and sustainability of these

  18. A multiomics approach to study the microbiome response to phytoplankton blooms.

    Science.gov (United States)

    Song, Liyan

    2017-06-01

    Phytoplankton blooms are predictable features of marine and freshwater habitats. Despite a good knowledge base of the environmental factors controlling blooms, complex interactions between the bacterial and archaeal communities and phytoplankton bloom taxa are only now emerging. Here, the current research on bacterial community's structural and functional response to phytoplankton blooms is reviewed and discussed and further research is proposed. More attention should be paid on structure and function of autotrophic bacteria and archaea during phytoplankton blooms. A multiomics integration approach is needed to investigate bacterial and archaeal communities' diversity, metabolic diversity, and biogeochemical functions of microbial interactions during phytoplankton blooms.

  19. Incremental Visualizer for Visible Objects

    DEFF Research Database (Denmark)

    Bukauskas, Linas; Bøhlen, Michael Hanspeter

    path. IVVO is the novel solution which allows data to be visualized and loaded on the fly from the database and which regards visibilities of objects. We run a set of experiments to convince that IVVO is feasible in terms of I/O operations and CPU load. We consider the example of data which uses......This paper discusses the integration of database back-end and visualizer front-end into a one tightly coupled system. The main aim which we achieve is to reduce the data pipeline from database to visualization by using incremental data extraction of visible objects in a fly-through scenarios. We...... also argue that passing only relevant data from the database will substantially reduce the overall load of the visualization system. We propose the system Incremental Visualizer for Visible Objects (IVVO) which considers visible objects and enables incremental visualization along the observer movement...

  20. vysmaw: Fast visibility stream muncher

    Science.gov (United States)

    Pokorny, Martin; Law, Casey J.

    2017-10-01

    The vysmaw client library facilitates the development of code for processes to tap into the fast visibility stream on the National Radio Astronomy Observatory's Very Large Array correlator back-end InfiniBand network.

  1. Visible neutrino decay at DUNE

    Energy Technology Data Exchange (ETDEWEB)

    Coloma, Pilar [Fermilab; Peres, Orlando G. [ICTP, Trieste

    2017-05-09

    If the heaviest neutrino mass eigenstate is unstable, its decay modes could include lighter neutrino eigenstates. In this case part of the decay products could be visible, as they would interact at neutrino detectors via mixing. At neutrino oscillation experiments, a characteristic signature of such \\emph{visible neutrino decay} would be an apparent excess of events at low energies. We focus on a simple phenomenological model in which the heaviest neutrino decays as $\

  2. Computing Visible-Surface Representations,

    Science.gov (United States)

    1985-03-01

    of applications. @ Massachusetts Institute of Technology 1985 "’ki report dcs;crihrs rccarch done at the Arificial lInelligence lhaboratory of the...411FO111 OIMMI bm tpal) IS. SUPPLEMENTARY MOTES None A IS~~~1. KEY WORS (Co~me 01 reerseea ............ MIngUfy ySek It Vision Variational principles...perception of visible surfaces. The explicit representation of visible surfaces, an intermediate goal of computational vision , has since attracted

  3. Phytoplankton and Nutrient Dynamics of a Tropical Estuarine ...

    African Journals Online (AJOL)

    Nekky Umera

    and significant difference in the stations (p< 0.05). A wide array of phytoplankton species ... the different potential roles water has as a resource, optimization is best achieved through a combination of uses. .... Apart from the major cations, anions and dissolved solids in water, gases were important chemical components of ...

  4. Phytoplankton Diversity in the Cross River Estuary of Nigeria ...

    African Journals Online (AJOL)

    DR. MIKE HORSFALL

    (Diatom) was the most abundant phytoplankton family, constituting 71.58% of total Algal density, followed by .... sampling zone B. The lower diatom dominance in ..... Fisheries Research. 47:81-92. Newell, GB; Newell RC (1977). Marine Plankton: A. Practical Gide. Hutchinson and Company. Publishers Ltd. London 229pp.

  5. Environmental variables, algal pigments and phytoplankton in the ...

    African Journals Online (AJOL)

    The phytoplankton diversity, environmental variables and algal pigments of the Atlantic Ocean off the coast of Badagry, Lagos were investigated for twelve months between May 2015 and April 2016. The water chemistry characteristics reflected sea water conditions. At the two stations, the range of values recorded for some ...

  6. Physicochemical conditions in affecting the distribution of spring phytoplankton community

    Science.gov (United States)

    Wei, Yuqiu; Liu, Haijiao; Zhang, Xiaodong; Xue, Bing; Munir, Sonia; Sun, Jun

    2017-11-01

    To better understand the physicochemical conditions in affecting regional distribution of phytoplankton community, one research cruise was carried out in the Bohai Sea and Yellow Sea during 3rd and 23th May, 2010. The phytoplankton community, including Bacillariophyta (105 taxa), Pyrrophyta (54 taxa), Chrysophyta (1 taxon) and Chlorophyta (2 taxa), had been identified and clearly described from six ecological provinces. And, the six ecological provinces were partitioned based on the top twenty dominant species related with notable physicochemical parameters. In general, the regional distributions of phytoplankton ecological provinces were predominantly influenced by the physicochemical properties induced by the variable water masses and circulations. The predominant diatoms in most of water samples showed well adaptability in turbulent and eutrophic conditions. However, several species of dinoflagellates e.g., Protoperidinium conicum, Protoperidinium triestinum, Protoperidinium sp. and Gymnodinium lohmanni preferred warmer, saltier and nutrient-poor environment. Moreover, the dinoflagellates with high frequency in the Yellow Sea might be transported from the Yellow Sea Warm Current. The horizontal distribution of phytoplankton was depicted by diatoms and controlled by phosphate concentration, while the vertical distribution was mainly supported by light and nutrients availability in the subsurface and bottom layers, respectively.

  7. Spatio-temporal variations in phytoplankton community structure in ...

    African Journals Online (AJOL)

    OMARI

    2013-09-06

    Sep 6, 2013 ... Spatio-temporal variations of phytoplankton, expressed in terms of species composition and diversity collected at various sampling sites in small water bodies (SWBs) within Lake Victoria basin, Kenya, were investigated monthly from November 2010 to June 2011, in relation to selected physical and.

  8. Phytoplankton productivity in newly dug fish ponds within Lake ...

    African Journals Online (AJOL)

    EJIRO

    Full Length Research Paper. Phytoplankton productivity in newly dug fish ponds ... The research was carried out in two wetlands situated within the. Lake Victoria basin, located at an altitude of 1134 m above .... planktonlyngbya limnetica, and among the diatoms the. Nitzschia spp and Navicula spp were in high numbers.

  9. Spatio-temporal variations in phytoplankton community structure in ...

    African Journals Online (AJOL)

    OMARI

    2013-09-06

    Sep 6, 2013 ... Spatio-temporal variations of phytoplankton, expressed in terms of species composition and diversity collected at various sampling ... chemical and biological properties of water most often lead to the production of .... Persulfate digestion methods, respectively in the laboratory (APHA,. 2000). Data analysis.

  10. Photoinhibition as affected by photoacclimation in phytoplankton: a model approach.

    NARCIS (Netherlands)

    Zonneveld, C.

    1998-01-01

    The photosynthesis-irradiance curve (or PI-curve, for short) in phytoplankton is highly plastic, in response to changes in the environment. The response to changes in the long term average irradiance is usually designated by the term 'photoacclimation'. On a much shorter time scale, high irradiances

  11. Distribution of phytoplankton in some parts of Lagos Lagoon ...

    African Journals Online (AJOL)

    Phytoplankton samples were collected from twelve stations during the wet (July, 2008) and dry (March, 2009) seasons. A typical freshwater condition prevailed in the study area during wet season with salinity of 0 parts per thousand (o/oo) at every station, whereas during the dry season, relatively high salinity levels were ...

  12. Some physico-chemical parameters and phytoplankton biodiversity ...

    African Journals Online (AJOL)

    The Ithikkara River, Kerala, India is used for drinking, bathing and fisheries purposes. It is important to have information on the water quality of this river considering its importance to the inhabitants of Kerala. The study therefore determined some physico-chemical parameters and phytoplankton population of Ithikara River.

  13. Phytoplankton Productivity numerical model: calibration via laboratory cultures

    Science.gov (United States)

    Zavatarelli, Marco; fiori, Emanuela; Carolina, Amadio

    2017-04-01

    The primary production module of the "Biogeochemical Flux Model" (BFM) has been used to replicate results from laboratory phytoplankton cultures of diatoms, dinoflagellates and picophytoplankton. The model explicitly solve for the phytoplankton, chlorophyll, carbon, phosphorus, nitrogen and (diatoms only) silicon content. Simulations of the temporal evolution of the cultured phytoplankton biomass, have been carried out in order to provide a correct parameterization of the temperature role in modulating the growth dynamics, and to gain insight in the process of chlorophyll turnover, with particular reference to the phytoplankton biomass decay in condition of nutrient stress. Results highligthed some limitation of the Q10 approach in defining the temperature constraints on the primary production (particularly at relatively high temperature) This required a modification of such approach. Moreover, the decay of the chlorophyll concentration under nutrient stress, appeared (as expected) significantly decoupled from the evolution of the carbon content. The implementation of a specific procedure (based on the laboratory culture results) adressing such decoupling, allowed for the achievement of better agreement between model and observations.

  14. Spatio-temporal variations of phytoplankton community composition ...

    African Journals Online (AJOL)

    STORAGESEVER

    2009-10-05

    Oct 5, 2009 ... (2003), who concluded that short-term phyto- plankton variations were controlled by temperature, wind and turbidity, while long-term abundance dynamics were influenced by nutrients. However, these findings are insufficient to understand phytoplankton dynamics since only pelagic data were considered.

  15. Environmental flow assessments in estuaries related to preference of phytoplankton

    Science.gov (United States)

    Yang, Z. F.; Sun, T.; Zhao, R.

    2014-05-01

    An approach to assess estuarine environmental flow based on phytoplankton preference, including the complex relationships between hydrological modifications and ecosystem biomass, was developed in this study. We initially established a relationship between biomass requirements for primary and higher nutritional level organisms based on the ecosystem nutritional energy flow principles. Subsequently, diagnostic pigments were employed to represent phytoplankton community biomass, which indicated competition between two groups of phytoplankton in the biochemistry process. Considering empirical relationships between diagnostic pigments and critical environmental factors, biomass responses to river discharge were established by simulating distributions of critical environmental factors under action of river discharges and tide currents. Consequently, environmental flows were recommended for different fish biomass requirements. We used the Yellow River estuary as a case study; and May and June were identified as critical months for maintaining environmental flow. Temporal variation in natural river flow dynamics, which was used as a proxy for environmental flow, should be carefully examined in artificial hydrological regulation strategies, particularly during high-amplitude flood pulses, which might result in negative effects on phytoplankton groups, and subsequently higher aquatic species biomass.

  16. Photoinhibition and the assembly of light-limited phytoplankton communities

    NARCIS (Netherlands)

    Gerla, D.J.; Mooij, W.M.; Huisman, J.

    2011-01-01

    Photoinhibition is characterised by a decreasing rate of photosynthesis with increasing light. It occurs in many photosynthetic organisms and is especially apparent in phytoplankton species sensitive to high light. Yet, the population and community level consequences of photoinhibition are not well

  17. Influence of Water quality on the biodiversity of phytoplankton in ...

    African Journals Online (AJOL)

    Michael Horsfall

    Influence of Water quality on the biodiversity of phytoplankton in Dhamra River. Estuary of Odisha Coast, Bay of Bengal. PALLEYI, S ... ecosystem and play a major role in the global cycling of carbon, nitrogen, phosphorus and other ... Water samples for the measurement of salinity, turbidity and nutrient parameters were ...

  18. River flow control on the phytoplankton dynamics of Chesapeake Bay

    Science.gov (United States)

    Yu, Qingyun; Wang, You; Tang, Xuexi; Li, Ming

    2013-03-01

    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 80 mmol N m-3. 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 r 2 for all quantities exceeds 0.95, and the skill parameter for the four seasons is all above 0.95.

  19. Phytoplankton diversity indices of Osse river, Edo state, Nigeria ...

    African Journals Online (AJOL)

    The phytoplankton diversity indices of Osse River, Edo State, Nigeria, were investigated monthly from January 2003 to April 2004. The plankton samples were collected from five sampling stations in the open water of the river using a plankton net of 55μm mesh net tied to a motorized boat and towed at low speed for five ...

  20. Seasonal and interannual variability in phytoplankton biomass on ...

    African Journals Online (AJOL)

    Surface ocean phytoplankton biomass variability on the southern African continental shelf area is investigated using coastal zone colour scanner data for the period 1979–1986. Coherent interannual trends in surface ocean chlorophyll for both the west coast Benguela and the south coast Agulhas Bank areas correspond ...

  1. Phytoplankton dynamics and periodicity in two cascading warm ...

    African Journals Online (AJOL)

    Consideration of phytoplankton dynamics in terms of functional groups offers certain advantages over conventional phyletic taxonomic analyses, although algal response forecasting by either approach appears potentially constrained by hydrological variability. Site-specific bio-monitoring, possibly using new rapid ...

  2. Growth response of natural phytoplankton to enrichment of urea and ...

    African Journals Online (AJOL)

    user

    mail: nita.r@unhas.ac.id. Tel: +62-0411-588828. Fax: +62-0411-586025. subsequent eutrophication-enhanced phytoplankton growth (D'Elia et al., 1986; Janse, 1997; Ornolfsdottir et al., 2004). Excessive biomass associated with algal blooms ...

  3. Saccharides enhance iron bioavailability to Southern Ocean phytoplankton

    NARCIS (Netherlands)

    Hassler, C.S.; Schoemann, V.; Nichols, C.M.; Butler, E.C.V.; Boyd, P.W.; Nichols, C.M.

    2011-01-01

    Iron limits primary productivity in vast regions of the ocean. Given that marine phytoplankton contribute up to 40% of global biological carbon fixation, it is important to understand what parameters control the availability of iron (iron bioavailability) to these organisms. Most studies on iron

  4. The evolutionary inheritance of elemental stoichiometry in marine phytoplankton

    Science.gov (United States)

    Quigg, Antonietta; Finkel, Zoe V.; Irwin, Andrew J.; Rosenthal, Yair; Ho, Tung-Yuan; Reinfelder, John R.; Schofield, Oscar; Morel, Francois M. M.; Falkowski, Paul G.

    2003-09-01

    Phytoplankton is a nineteenth century ecological construct for a biologically diverse group of pelagic photoautotrophs that share common metabolic functions but not evolutionary histories. In contrast to terrestrial plants, a major schism occurred in the evolution of the eukaryotic phytoplankton that gave rise to two major plastid superfamilies. The green superfamily appropriated chlorophyll b, whereas the red superfamily uses chlorophyll c as an accessory photosynthetic pigment. Fossil evidence suggests that the green superfamily dominated Palaeozoic oceans. However, after the end-Permian extinction, members of the red superfamily rose to ecological prominence. The processes responsible for this shift are obscure. Here we present an analysis of major nutrients and trace elements in 15 species of marine phytoplankton from the two superfamilies. Our results indicate that there are systematic phylogenetic differences in the two plastid types where macronutrient (carbon:nitrogen:phosphorus) stoichiometries primarily reflect ancestral pre-symbiotic host cell phenotypes, but trace element composition reflects differences in the acquired plastids. The compositional differences between the two plastid superfamilies suggest that changes in ocean redox state strongly influenced the evolution and selection of eukaryotic phytoplankton since the Proterozoic era.

  5. Phytoplankton productivity in the surface ocean forms the basis of ...

    African Journals Online (AJOL)

    spamer

    to assessing the future viability of the fisheries resource, and the potential impacts of climate change ... fore not true means and are biased against conditions associated with cloud cover. Each pixel represents ..... global warming on phytoplankton and its implications for pelagic fish. S. Afr. J. Sci. 87: 233–242. BROWN, P. C. ...

  6. 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.

  7. Competing phytoplankton undermines allelopathy of a bloom-forming dinoflagellate.

    Science.gov (United States)

    Prince, Emily K; Myers, Tracey L; Naar, Jerome; Kubanek, Julia

    2008-12-07

    Biotic interactions in the plankton can be both complex and dynamic. Competition among phytoplankton is often chemically mediated, but no studies have considered whether allelopathic compounds are modified by biotic interactions. Here, we show that compounds exuded during Karenia brevis blooms were allelopathic to the cosmopolitan diatom Skeletonema costatum, but that bloom allelopathy varied dramatically among collections and years. We investigated several possible causes of this variability and found that neither bloom density nor concentrations of water-borne brevetoxins correlated with allelopathic potency. However, when we directly tested whether the presence of competing phytoplankton influenced bloom allelopathy, we found that S. costatum reduced the growth-inhibiting effects of bloom exudates, suggesting that S. costatum has a mechanism for undermining K. brevis allelopathy. Additional laboratory experiments indicated that inducible changes to K. brevis allelopathy were restricted to two diatoms among five sensitive phytoplankton species, whereas five other species were constitutively resistant to K. brevis allelopathy. Our results suggest that competitors differ in their responses to phytoplankton allelopathy, with S. costatum exhibiting a previously undescribed method of resistance that may influence community structure and alter bloom dynamics.

  8. Observations and models of highly intermittent phytoplankton distributions.

    Directory of Open Access Journals (Sweden)

    Sandip Mandal

    Full Text Available The measurement of phytoplankton distributions in ocean ecosystems provides the basis for elucidating the influences of physical processes on plankton dynamics. Technological advances allow for measurement of phytoplankton data to greater resolution, displaying high spatial variability. In conventional mathematical models, the mean value of the measured variable is approximated to compare with the model output, which may misinterpret the reality of planktonic ecosystems, especially at the microscale level. To consider intermittency of variables, in this work, a new modelling approach to the planktonic ecosystem is applied, called the closure approach. Using this approach for a simple nutrient-phytoplankton model, we have shown how consideration of the fluctuating parts of model variables can affect system dynamics. Also, we have found a critical value of variance of overall fluctuating terms below which the conventional non-closure model and the mean value from the closure model exhibit the same result. This analysis gives an idea about the importance of the fluctuating parts of model variables and about when to use the closure approach. Comparisons of plot of mean versus standard deviation of phytoplankton at different depths, obtained using this new approach with real observations, give this approach good conformity.

  9. Phytoplankton community in relation to physico-chemical ...

    African Journals Online (AJOL)

    Phytoplankton community in relation to physico-chemical characteristics of the Talar River, Iran. ... The dominant zooplanktonic organisms determined were Paramecium, Daphnia, Cypris, Keratalla and Arachinous. The present study on ecology and the surface water of this fresh water river covered a number of aspects, ...

  10. Phytoplankton/protozoan dynamics in the Nyara Estuary, a small ...

    African Journals Online (AJOL)

    When not receiving pulses of nutrients through freshwater inflow, the Nyara is best described as a predominantly low nutrient, low phytoplankton biomass, stratified system, dominated by the microbial food-web and possibly fed by detritus. This state can however, be altered rapidly by flood events that cause mouth opening.

  11. Phytoplankton Virus Production Negatively Affected by Iron Limitation

    NARCIS (Netherlands)

    Slagter, H.A.; Gerringa, L.J.A.; Brussaard, C.P.D.

    2016-01-01

    Fe-limited monocultures of the ubiquitous algae Micromonas pusilla and Phaeocystis globosa were infected with their respective viruses (MpV and PgV) to ascertain the effect of Fe-limitation on phytoplankton host-virus dynamics. The effect of the viral shunt on Fe concentrations and bioavailability

  12. Seasonal variation in phytoplankton in the southern Benguela ...

    African Journals Online (AJOL)

    Pigment indices and satellite imagery were used to investigate the seasonal variation in phytoplankton in the southern Benguela, with the aid of monthly monitoring on two transect lines. Sea surface temperature images revealed the similarity in thermal conditions during autumn, winter and spring, with a broad zone of ...

  13. Spatial-temporal changes in phytoplankton biomass and primary ...

    African Journals Online (AJOL)

    Spatial-temporal variations in phytoplankton primary production (PP) and biomass (B) were studied for a period of about one year, from July 1999 to July 2000. In addition, changes in corresponding environmental variables were examined. Sampling took place at two stations in Chwaka Bay, one located in mangrove areas, ...

  14. Composition of phytoplankton algae in Gubi Reservoir, Bauchi ...

    African Journals Online (AJOL)

    Studies on the distribution, abundance and taxonomic composition of phytoplankton algae in Gubi reservoir were carried out for 12 months (from January to December 1995). Of the 26 algal taxa identified, 14 taxa belonged to the diatoms, 8 taxa were green algae while 4 taxa belonged to the blue-green algae. Higher cell ...

  15. Growth response of natural phytoplankton to enrichment of urea and ...

    African Journals Online (AJOL)

    The Broadwater of Myall Lakes, NWS Australia is brackish water which has a high variation in water quality in particular salinity and nutrient concentration. In these experiments, we determined the growth and species assemblages of natural phytoplankton community exposed to nutrient enrichment. Laboratory incubation ...

  16. Phytoplankton diversity and abundance as a function of water ...

    African Journals Online (AJOL)

    Water quality and phytoplankton composition of two Reservoirs (Bomo and Kubanni) in Zaria, Nigeria, were investigated for their fish production potentials from April to June 2011. April represented the dry period, while May and June were months with rains. Physicochemical parameters of the two Reservoirs showed ...

  17. Phytoplankton community and their impact on water quality: An ...

    African Journals Online (AJOL)

    Algal bloom had been a problem on the Hollingworth Lake in years' past to the locales and the lake's biodiversity. In order to assess the status of the lake, the lake's phytoplankton and water quality were examined during the study period of June to August 2004) at three lake depths. 49 species belonging to 7 different ...

  18. Induced growth of phytoplankton using two fertilizers (NPK and ...

    African Journals Online (AJOL)

    An investigation was carried out on the ability of two types of fertilizer; agrolyser micronutrient and NPK (nitrogen, phosphorus, potassium)-macronutrient in inducing phytoplankton growth for sixteen days under laboratory conditions. The parameters studied were abundance, species diversity and occurrence of the ...

  19. Observations and Models of Highly Intermittent Phytoplankton Distributions

    Science.gov (United States)

    Mandal, Sandip; Locke, Christopher; Tanaka, Mamoru; Yamazaki, Hidekatsu

    2014-01-01

    The measurement of phytoplankton distributions in ocean ecosystems provides the basis for elucidating the influences of physical processes on plankton dynamics. Technological advances allow for measurement of phytoplankton data to greater resolution, displaying high spatial variability. In conventional mathematical models, the mean value of the measured variable is approximated to compare with the model output, which may misinterpret the reality of planktonic ecosystems, especially at the microscale level. To consider intermittency of variables, in this work, a new modelling approach to the planktonic ecosystem is applied, called the closure approach. Using this approach for a simple nutrient-phytoplankton model, we have shown how consideration of the fluctuating parts of model variables can affect system dynamics. Also, we have found a critical value of variance of overall fluctuating terms below which the conventional non-closure model and the mean value from the closure model exhibit the same result. This analysis gives an idea about the importance of the fluctuating parts of model variables and about when to use the closure approach. Comparisons of plot of mean versus standard deviation of phytoplankton at different depths, obtained using this new approach with real observations, give this approach good conformity. PMID:24787740

  20. Mesoscale features and phytoplankton biomass at the GoodHope ...

    African Journals Online (AJOL)

    Two sets of high-resolution subsurface hydrographic and underway surface chlorophylla (Chl a) measurements are used, in conjunction with satellite remotely sensed data, to investigate the upper layer oceanography (mesoscale features and mixed layer depth variability) and phytoplankton biomass at the GoodHope line ...

  1. Growth of Phytoplankton in Different Fertilizer Media | KADIRI ...

    African Journals Online (AJOL)

    The growth response of phytoplankton was examined in organic manure and inorganic fertilizers. The organic fertilizers used were cow dung, poultry droppings as well as their combination with inorganic fertilizer while the inorganic fertilizer was NPK triple super phosphate (ratio 15:17:17). The study involved both natural ...

  2. Seasonal changes in phytoplankton biomass on the Western ...

    African Journals Online (AJOL)

    Data on temporal and spatial changes in phytoplankton biomass and distribution on the western Agulhas Bank during the main spawning season of pelagic fish were obtained from monthly cruises conducted between. August and March in 1993/94 and September and March in 1994/95. The period was divided into three ...

  3. Phytoplankton responses to changes in macrophyte density in a ...

    African Journals Online (AJOL)

    The response of phytoplankton population dynamics to changes in densities of Nymphaea lotus L. and Polygonum limbatum Meisn. was studied in an artificial pond in Zaria, Nigeria, from June to November 2007. Antagonistic effects of these macrophytes on Netrium sp., Staurastrum sp., Ulothrix sp., Marssionella sp. and ...

  4. Nutrient limitation of phytoplankton in five impoundments on the ...

    African Journals Online (AJOL)

    Nutrient limitation was investigated in the Manyame lakes, namely, Harava Dam, Seke Dam, Lake Chivero, Lake Manyame and Bhiri Dam, during 2004-05. Selenestrum capricornutum was used as the test organism in one group of bioassays and the lakes' natural phytoplankton population in the other. Nitrogen was ...

  5. Pigment signatures of phytoplankton composition in the northern ...

    African Journals Online (AJOL)

    Pigment indices were used to investigate the distribution and composition of phytoplankton in the northern Benguela during the austral spring of 2000, with sampling being conducted on five transect lines between 19°S and 25°S and at other inshore stations on the shelf. Total chlorophyll a concentrations (TChla) at the ...

  6. Spatio-temporal variations in phytoplankton community structure in ...

    African Journals Online (AJOL)

    Spatio-temporal variations of phytoplankton, expressed in terms of species composition and diversity collected at various sampling sites in small water bodies (SWBs) within Lake Victoria basin, Kenya, were investigated monthly from November 2010 to June 2011, in relation to selected physical and chemical water quality ...

  7. Phytoplankton Species Associations in Two Tropical Rivers in ...

    African Journals Online (AJOL)

    This study evaluated the influence of water quality conditions on phytoplankton communities in Ona and Ogunpa rivers using a series of multivariate statistical methods. The principal component factor analysis of environmental variables revealed that buffering capacity and trace metal levels were major determinants of ...

  8. Phytoplankton community and physico-chemical seasonality and ...

    African Journals Online (AJOL)

    Phytoplankton community structure and physico-chemical variables, sampled monthly at an offshore station in Lake Hora-Kilole from August 2007 to May 2008, were compared with previously reported data. In 1989 the Mojo River was temporarily diverted to flow into the lake. The lake subsequently changed markedly, first ...

  9. Phytoplankton species diversity and abundance in the near shore ...

    African Journals Online (AJOL)

    The survey was carried out in January/February and July/August 2002 to investigate phytoplankton species diversity, spatial distribution, numerical abundance and total biomass (chlorophyll a concentration) in 10 selected stations on the Tanzanian side of Lake Victoria. At each station, samples for diversity data were ...

  10. Isolation by Time During an Arctic Phytoplankton Spring Bloom.

    Science.gov (United States)

    Tammilehto, Anna; Watts, Phillip C; Lundholm, Nina

    2017-03-01

    The arctic phytoplankton spring bloom, which is often diatom-dominated, is a key event that provides the high latitude communities with a fundamental flux of organic carbon. During a bloom, phytoplankton may increase its biomass by orders of magnitude within days. Yet, very little is known about phytoplankton bloom dynamics, including for example how blooming affects genetic composition and diversity of a population. Here, we quantified the genetic composition and temporal changes of the diatom Fragilariopsis cylindrus, which is one of the most important primary producers in the Arctic, during the spring bloom in western Greenland, using 13 novel microsatellite markers developed for this study. We found that genetic differentiation (quantified using sample-specific F ST ) decreased between time points as the bloom progressed, with the most drastic changes in F ST occurring at the start of the bloom; thus the genetic structure of the bloom is characterized by isolation by time. There was little temporal variation in genetic diversity throughout the bloom (mean H E  = 0.57), despite marked fluctuations in F. cylindrus cell concentrations and the temporal change in sample-specific F ST . On the basis of this novel pattern of genetic differentiation, we suggest that blooming behavior may promote genetic diversity of a phytoplankton population. © 2016 The Author(s) Journal of Eukaryotic Microbiology © 2016 International Society of Protistologists.

  11. Chemical warfare in freshwater. Allelpathic effects of macrophytes on phytoplankton

    NARCIS (Netherlands)

    Mulderij, G.

    2006-01-01

    Aquatic macrophytes can excrete chemical substances into their enviroment and these compounds may inhibit the growth of phytoplankton. This process is defined as allelopathy: one organism has effects on another via the excretion of a (mixture of) chemical substance(s). With laboratory and field

  12. Coagulation efficiency and aggregate formation in marine phytoplankton

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Andersen, K.P.; Dam, H.G.

    1990-01-01

    , which is mainly physically controlled, and on the probability of adhesion upon collison (= coagulation efficiency, stickiness), which depends on physico-chemical and biological properties of the cells. We describe here an experimental method to quantify the stickiness of phytoplankton cells...

  13. 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.

  14. wet season spatial occurrence of phytoplankton and zooplankton in ...

    African Journals Online (AJOL)

    Administrator

    Onyema (2007) on a tidal creek (Abule-elude creek) and Onyema. &Ojo (2008) on the lower Ogun river (Agboyi creek). The aim of this work is to investigate the spatial occurrence of phytoplankton and zooplankton in the wet season in relation to environmental characteristics. MATERIALS AND METHODS. The Study Area: ...

  15. An automated platform for phytoplankton ecology and aquatic ecosystem monitoring

    NARCIS (Netherlands)

    Pomati, F.; Jokela, J.; Simona, M.; Veronesi, M.; Ibelings, B.W.

    2011-01-01

    High quality monitoring data are vital for tracking and understanding the causes of ecosystem change. We present a potentially powerful approach for phytoplankton and aquatic ecosystem monitoring, based on integration of scanning flow-cytometry for the characterization and counting of algal cells

  16. Phytoplankton dynamics studying using observation and biophysical modeling

    Science.gov (United States)

    Xu, Yi

    Continental shelf phytoplankton bloom dynamics are associated with meteorological, oceanographic and coastal forcing mechanisms. Mixing related to stratification and de-stratification is a key process of the physical environment that can control the timing and magnitude of blooms. Using data from satellite, coastal ocean observatory and bio-physical model, this study investigated the seasonal and decadal variability of chlorophyll in the Mid-Atlantic Bight and how different forcing mechanisms affect the phytoplankton bloom. The temporal and spatial distribution of chlorophyll a in the MAB was quantified using satellite data collected by the Sea-viewing Wide Field of view Sensor (SeaWiFS). The MAB undergoes a fall-winter bloom in the middle-outer shelf region and spring bloom in the shelf-break region. The interannual variability of bloom magnitude is associated with wind-induced mixing. Mixing has been recognized as having an important role in influencing underwater light and nutrient budgets and thus regulating phytoplankton bloom. The ratio of light over mixed layer depth (MLD) was used to determine the trade-off effects of mixing on phytoplankton bloom activity. We find that a critical light value around 60 (W m-2) for the shelf region and 150 (W m-2) for the shelf-break front region in promoting maximum phytoplankton biomass and there is a predictable linear regression relationship between the critical light value and depth. The bio-physical model identified the wind-induced mixing, net heat flux and river run-off are the most important factors influencing water column stability. Sensitivity studies showed that the timing of the destratification and initiation of fall bloom was closely related to the wind forcing. The river's role in bringing buoyancy was significant in increasing phytoplankton bloom. The decadal declines in the seasonal satellite estimates of chlorophyll a&barbelow; concentrations have been observed in the fall and winter in the MAB and are

  17. The dynamics of temperature and light on the growth of phytoplankton.

    Science.gov (United States)

    Chen, Ming; Fan, Meng; Liu, Rui; Wang, Xiaoyu; Yuan, Xing; Zhu, Huaiping

    2015-11-21

    Motivated by some lab and field observations of the hump shaped effects of water temperature and light on the growth of phytoplankton, a bottom-up nutrient phytoplankton model, which incorporates the combined effects of temperature and light, is proposed and analyzed to explore the dynamics of phytoplankton bloom. The population growth model reasonably captures such observed dynamics qualitatively. An ecological reproductive index is defined to characterize the growth of the phytoplankton which also allows a comprehensive analysis of the role of temperature and light on the growth and reproductive characteristics of phytoplankton in general. The model provides a framework to study the mechanisms of phytoplankton dynamics in shallow lake and may even be employed to study the controlled phytoplankton bloom. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

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

    2015-03-01

    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 rates in relation to nutrient concentration and the behaviour of a simple multi-species community model suggest that community growth rate does not respond to nutrient concentration according to the Monod equation. Through a simulation study we show this can be explained as a consequence of changes in size structure. Marine biogeochemical models must not parameterize phytoplankton community growth rate response to nutrient concentration using a single Monod equation but rather involve different phytoplankton functional groups each with different equation parameters.

  19. Phytoplankton biomass, production and potential export in the North Water

    Science.gov (United States)

    Klein, Bert; LeBlanc, Bernard; Mei, Zhi-Ping; Beret, Rachel; Michaud, Josée; Mundy, C.-J.; von Quillfeldt, Cecilie H.; Garneau, Marie-Ève; Roy, Suzanne; Gratton, Yves; Cochran, J. Kirk; Bélanger, Simon; Larouche, Pierre; Pakulski, J. Dean; Rivkin, Richard B.; Legendre, Louis

    The seasonal patterns of phytoplankton biomass and production were determined in the North Water, located between Greenland and Ellesmere Island (Canadian Arctic), in August 1997, April-July 1998, and August-September 1999. The patterns differed among the four defined regions of this large polynya, i.e. North (>77.5°N), East (>75°W), West (5 μm) fraction dominated the biomass and production during the bloom. During July, August, and September, biomass and production decreased over the whole region, with the highest biomass, dominated by large cells, occurring in the North. The annual particulate and dissolved phytoplankton production were the highest ever reported for the high Arctic, reaching maximum values of 254 and 123 g C m -2 yr -1, respectively, in the East. Rates in the North and West were considerably lower than in the East (ca. two- and three-fold, respectively). The f-ratios (i.e. ratio of new to total production), derived from the size structure of phytoplankton, were high north of 76°N (0.4-0.7). Regionally, this indicated a high potential export of particulate organic carbon ( EPOC) from the phytoplankton community to other trophic compartments and/or downwards in the East (155 g C m -2 yr -1), with lower values in the North and West (i.e. 77 and 42 g C m -2 yr -1, respectively). The seasonal and spatial patterns of EPOC were consistent with independent estimates of potential carbon export. Phytoplankton biomass and production were generally dominated by the large size fraction, whereas EPOC seemed to be dominated by the large size fraction early in the season and by the small size fraction (<5 μm) from June until the end of the growing season.

  20. Differential Growth Responses of Marine Phytoplankton to Herbicide Glyphosate

    Science.gov (United States)

    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 dissolved inorganic phosphorus (DIP) conditions, we found that phytoplankton species could be classified into five groups. Group I (Emiliania huxleyi, Skeletonema costatum, Phaeodactylum tricornutum) could utilize glyphosate as sole P-source to support growth in axenic culture, but in the presence of DIP, they were inhibited by both 36-μM and 360-μM glyphosate. Group II (Karenia mikimotoi, Prorocentrum minimum, Dunaliella tertiolecta, Symbiodinium sp., Heterosigma akashiwo and Alexandrium catenella) could not utilize glyphosate as sole P-source to support growth, and in the presence of DIP growth was not affected by 36-μM but inhibited by 360-μM glyphosate. Glyphosate consistently enhanced growth of Group III (Isochrysis galbana) and inhibited Group IV (Thalassiosira weissflogii, Thalassiosira pseudonana and Chattonella marina) regardless of DIP condition. Group V (Amphidinium carterae) exhibited no measurable response to glyphosate regardless of DIP condition. This grouping is not congruent with the phylogenetic relationships of the phytoplankton species suggesting functional differentiation driven by environmental pressure. We conclude that glyphosate could be used as P-source by some species while is toxic to some other species and yet has no effects on others. The observed differential effects suggest that the continued use of glyphosate and increasing concentration of this herbicide in the coastal waters will likely exert significant impact on coastal marine phytoplankton

  1. Simulated ocean acidification reveals winners and losers in coastal phytoplankton

    Science.gov (United States)

    Alvarez-Fernandez, Santiago; Hornick, Thomas; Stuhr, Annegret; Riebesell, Ulf

    2017-01-01

    The oceans absorb ~25% of the annual anthropogenic CO2 emissions. This causes a shift in the marine carbonate chemistry termed ocean acidification (OA). OA is expected to influence metabolic processes in phytoplankton species but it is unclear how the combination of individual physiological changes alters the structure of entire phytoplankton communities. To investigate this, we deployed ten pelagic mesocosms (volume ~50 m3) for 113 days at the west coast of Sweden and simulated OA (pCO2 = 760 μatm) in five of them while the other five served as controls (380 μatm). We found: (1) Bulk chlorophyll a concentration and 10 out of 16 investigated phytoplankton groups were significantly and mostly positively affected by elevated CO2 concentrations. However, CO2 effects on abundance or biomass were generally subtle and present only during certain succession stages. (2) Some of the CO2-affected phytoplankton groups seemed to respond directly to altered carbonate chemistry (e.g. diatoms) while others (e.g. Synechococcus) were more likely to be indirectly affected through CO2 sensitive competitors or grazers. (3) Picoeukaryotic phytoplankton (0.2–2 μm) showed the clearest and relatively strong positive CO2 responses during several succession stages. We attribute this not only to a CO2 fertilization of their photosynthetic apparatus but also to an increased nutrient competitiveness under acidified (i.e. low pH) conditions. The stimulating influence of high CO2/low pH on picoeukaryote abundance observed in this experiment is strikingly consistent with results from previous studies, suggesting that picoeukaryotes are among the winners in a future ocean. PMID:29190760

  2. Simulated ocean acidification reveals winners and losers in coastal phytoplankton.

    Directory of Open Access Journals (Sweden)

    Lennart T Bach

    Full Text Available The oceans absorb ~25% of the annual anthropogenic CO2 emissions. This causes a shift in the marine carbonate chemistry termed ocean acidification (OA. OA is expected to influence metabolic processes in phytoplankton species but it is unclear how the combination of individual physiological changes alters the structure of entire phytoplankton communities. To investigate this, we deployed ten pelagic mesocosms (volume ~50 m3 for 113 days at the west coast of Sweden and simulated OA (pCO2 = 760 μatm in five of them while the other five served as controls (380 μatm. We found: (1 Bulk chlorophyll a concentration and 10 out of 16 investigated phytoplankton groups were significantly and mostly positively affected by elevated CO2 concentrations. However, CO2 effects on abundance or biomass were generally subtle and present only during certain succession stages. (2 Some of the CO2-affected phytoplankton groups seemed to respond directly to altered carbonate chemistry (e.g. diatoms while others (e.g. Synechococcus were more likely to be indirectly affected through CO2 sensitive competitors or grazers. (3 Picoeukaryotic phytoplankton (0.2-2 μm showed the clearest and relatively strong positive CO2 responses during several succession stages. We attribute this not only to a CO2 fertilization of their photosynthetic apparatus but also to an increased nutrient competitiveness under acidified (i.e. low pH conditions. The stimulating influence of high CO2/low pH on picoeukaryote abundance observed in this experiment is strikingly consistent with results from previous studies, suggesting that picoeukaryotes are among the winners in a future ocean.

  3. Characterizing the Phytoplankton Community of the South China Sea

    Science.gov (United States)

    Aleman, M.; Subramaniam, A.; Hay, I.

    2016-12-01

    The South China Sea (SCS) is a semi-enclosed tropical basin that receives nutrients from two main sources: coastal upwelling and river runoff from the surrounding countries. The southwest (SW) summer monsoon that occurs between March and September drives upwelling off the coast of Vietnam, a rarity compared to most upwelling systems that are driven by eastern boundary current systems. The upwelling in the SCS and the intensity of the SW monsoon are sensitive to climate variability and are affected by phenomenon such as El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). The size and location of the Mekong River plume also varies from year to year due to the variation in rainfall and wind strength of the monsoon. The riverine input is also influenced by anthropogenic activity such as agriculture, damming, and land-use changes. Different nutrients are supplied from these two main sources and in different quantities, and affect the structure of the phytoplankton community. Phytoplankton comprise the base of the food web, supporting the growth of higher organisms and ultimately support fisheries. We need to understand how the supply of different nutrients alters the phytoplankton community of the SCS. We sampled 22 stations along the coast of Vietnam aboard the R/V Falkor of the Schmidt Ocean Institute during the pre-monsoon season. High performance liquid chromatography (HPLC) and flow cytometric techniques will be used to characterize the phytoplankton community. The relationship between the different water masses, nutrient sources, and phytoplankton community found in the SCS will be presented.

  4. Iron from melting glaciers fuels phytoplankton blooms in the Amundsen Sea (Southern Ocean): Phytoplankton characteristics and productivity

    NARCIS (Netherlands)

    Alderkamp, A.C.; Mills, M.M.; van Dijken, G.L.; Laan, P.; Thuróczy, C.-E.; Gerringa, L.J.A.; de Baar, H.J.W.; Payne, C.D.; Visser, R.J.W.; Buma, A.G.J.; Arrigo, K.R.

    2012-01-01

    The phytoplankton community composition and productivity in waters of the Amundsen Sea and surrounding sea ice zone were characterized with respect to iron (Fe) input from melting glaciers. High Fe input from glaciers such as the Pine Island Glacier, and the Dotson and Crosson ice shelves resulted

  5. Feedback Interactions between Trace Metal Nutrients and Phytoplankton in the Ocean

    Science.gov (United States)

    Sunda, William G.

    2012-01-01

    In addition to control by major nutrient elements (nitrogen, phosphorus, and silicon) the productivity and species composition of marine phytoplankton communities are also regulated by a number of trace metal nutrients (iron, zinc, cobalt, manganese, copper, and cadmium). Of these, iron is most limiting to phytoplankton growth and has the greatest effect on algal species diversity. It also plays an important role in limiting di-nitrogen (N2) fixation rates, and thus is important in controlling ocean inventories of fixed nitrogen. Because of these effects, iron is thought to play a key role in regulating biological cycles of carbon and nitrogen in the ocean, including the biological transfer of carbon to the deep sea, the so-called biological CO2 pump, which helps regulate atmospheric CO2 and CO2-linked global warming. Other trace metal nutrients (zinc, cobalt, copper, and manganese) have lesser effects on productivity; but may exert an important influence on the species composition of algal communities because of large differences in metal requirements among species. The interactions between trace metals and ocean plankton are reciprocal: not only do the metals control the plankton, but the plankton regulate the distributions, chemical speciation, and cycling of these metals through cellular uptake and recycling processes, downward flux of biogenic particles, biological release of organic chelators, and mediation of redox reactions. This two way interaction has influenced not only the biology and chemistry of the modern ocean, but has had a profound influence on biogeochemistry of the ocean and earth system as a whole, and on the evolution of marine and terrestrial biology over geologic history. PMID:22701115

  6. 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

  7. Retrieval of phytoplankton and colored detrital matter absorption coefficients with remote sensing reflectance in an ultraviolet band.

    Science.gov (United States)

    Wei, Jianwei; Lee, Zhongping

    2015-02-01

    The light absorption of phytoplankton and colored detrital matter (CDM), which includes contribution of gelbstoff and detrital matters, has distinctive yet overlapping features in the ultraviolet (UV) and visible domain. The CDM absorption (a(dg)) increases exponentially with decreasing wavelength while the absorption coefficient of phytoplankton (a(ph)) generally decreases toward the shorter bands for the range of 350-450 nm. It has long been envisioned that including ocean color measurements in the UV range may help the separation of these two components from the remotely sensed ocean color spectrum. An attempt is made in this study to provide an analytical assessment of this expectation. We started with the development of an absorption decomposition model [quasi-analytical algorithm (QAA)-UV], analogous to the QAA, that partitions the total absorption coefficient using information at bands 380 and 440 nm. Compared to the retrieval results relying on the absorption information at 410 and 440 nm of the original QAA, our analyses indicate that QAA-UV can improve the retrieval of a(ph) and a(dg), although the improvement in accuracy is not significant for values at 440 nm. The performance of the UV-based algorithm is further evaluated with in situ measurements. The limited improvement observed with the field measurements highlights that the separation of a(dg) and a(ph) is highly dependent on the accuracy of the ocean color measurements and the estimated total absorption coefficient.

  8. 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

  9. Community stoichiometry in a changing world: combined effects of warming and eutrophication on phytoplankton dynamics.

    Science.gov (United States)

    Domis, Lisette N De Senerpont; Van de Waal, Dedmer B; Helmsing, Nico R; Van Donk, Ellen; Mooij, Wolf M

    2014-06-01

    The current changes in our climate will likely have far-reaching consequences for aquatic ecosystems. These changes in the climate, however, do not act alone, and are often accompanied by additional stressors such as eutrophication. Both global warming and eutrophication have been shown to affect the timing and magnitude of phytoplankton blooms. Little is known about the combined effects of rising temperatures and eutrophication on the stoichiometry of entire phytoplankton communities. We exposed a natural phytoplankton spring community to different warming and phosphorus-loading scenarios using a full-factorial design. Our results demonstrate that rising temperatures promote the growth rate of an entire phytoplankton community. Furthermore, both rising temperatures and phosphorus loading stimulated the maximum biomass built up by the phytoplankton community. Rising temperatures led to higher carbon: nutrient stoichiometry of the phytoplankton community under phosphorus-limited conditions. Such a shift towards higher carbon: nutrient ratios, in combination with a higher biomass buildup, suggests a temperature-driven increase in nutrient use efficiency, the phytoplankton community. Importantly, with higher carbon: nutrient stoichiometry, phytoplankton is generally of poorer nutritional value for zooplankton. Thus, although warming may result in higher phytoplankton biomass, this may be accompanied by a stoichiometric mismatch between phytoplankton and their grazers, with possible consequences for the entire aquatic food web.

  10. Discriminating Phytoplankton Functional Types (PFTs) in the Coastal Ocean Using the Inversion Algorithm Phydotax and Airborne Imaging Spectrometer Data

    Science.gov (United States)

    Palacios, Sherry L.; Schafer, Chris; Broughton, Jennifer; Guild, Liane S.; Kudela, Raphael M.

    2013-01-01

    There is a need in the Biological Oceanography community to discriminate among phytoplankton groups within the bulk chlorophyll pool to understand energy flow through ecosystems, to track the fate of carbon in the ocean, and to detect and monitor-for harmful algal blooms (HABs). The ocean color community has responded to this demand with the development of phytoplankton functional type (PFT) discrimination algorithms. These PFT algorithms fall into one of three categories depending on the science application: size-based, biogeochemical function, and taxonomy. The new PFT algorithm Phytoplankton Detection with Optics (PHYDOTax) is an inversion algorithm that discriminates taxon-specific biomass to differentiate among six taxa found in the California Current System: diatoms, dinoflagellates, haptophytes, chlorophytes, cryptophytes, and cyanophytes. PHYDOTax was developed and validated in Monterey Bay, CA for the high resolution imaging spectrometer, Spectroscopic Aerial Mapping System with On-board Navigation (SAMSON - 3.5 nm resolution). PHYDOTax exploits the high spectral resolution of an imaging spectrometer and the improved spatial resolution that airborne data provides for coastal areas. The objective of this study was to apply PHYDOTax to a relatively lower resolution imaging spectrometer to test the algorithm's sensitivity to atmospheric correction, to evaluate capability with other sensors, and to determine if down-sampling spectral resolution would degrade its ability to discriminate among phytoplankton taxa. This study is a part of the larger Hyperspectral Infrared Imager (HyspIRI) airborne simulation campaign which is collecting Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) imagery aboard NASA's ER-2 aircraft during three seasons in each of two years over terrestrial and marine targets in California. Our aquatic component seeks to develop and test algorithms to retrieve water quality properties (e.g. HABs and river plumes) in both marine and in

  11. Visibility of natural tertiary rainbows.

    Science.gov (United States)

    Lee, Raymond L; Laven, Philip

    2011-10-01

    Naturally occurring tertiary rainbows are extraordinarily rare and only a handful of reliable sightings and photographs have been published. Indeed, tertiaries are sometimes assumed to be inherently invisible because of sun glare and strong forward scattering by raindrops. To analyze the natural tertiary's visibility, we use Lorenz-Mie theory, the Debye series, and a modified geometrical optics model (including both interference and nonspherical drops) to calculate the tertiary's (1) chromaticity gamuts, (2) luminance contrasts, and (3) color contrasts as seen against dark cloud backgrounds. Results from each model show that natural tertiaries are just visible for some unusual combinations of lighting conditions and raindrop size distributions.

  12. Marine phytoplankton and the changing ocean iron cycle

    Science.gov (United States)

    Hutchins, D. A.; Boyd, P. W.

    2016-12-01

    The availability of the micronutrient iron governs phytoplankton growth across much of the ocean, but the global iron cycle is changing rapidly due to accelerating acidification, stratification, warming and deoxygenation. These mechanisms of global change will cumulatively affect the aqueous chemistry, sources and sinks, recycling, particle dynamics and bioavailability of iron. Biological iron demand will vary as acclimation to environmental change modifies cellular requirements for photosynthesis and nitrogen acquisition and as adaptive evolution or community shifts occur. Warming, acidification and nutrient co-limitation interactions with iron biogeochemistry will all strongly influence phytoplankton dynamics. Predicting the shape of the future iron cycle will require understanding the responses of each component of the unique biogeochemistry of this trace element to many concurrent and interacting environmental changes.

  13. 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...

  14. Initial size structure of natural phytoplankton communities determines the response to Daphnia diel vertical migration

    Directory of Open Access Journals (Sweden)

    Maarten Boersma

    2012-01-01

    Full Text Available Diel vertical migration (DVM is a common behavior of many pelagic herbivorous zooplankton species in response to predation pressure. It is characterized by a twice daily habitat shift of the zooplankton species: staying in the epilimnion only during night time and migrating down in the crack of dawn in deeper water layers, staying there during the day time. This causes a discontinuous grazing regime and previous studies have shown that the direction and strength of phytoplankton community responses to zooplankton DVM most probably depends on the size of phytoplankton species. To examine the influence of zooplankton DVM on different sized phytoplankton communities, we designed an experiment where we manipulated the size distribution of a natural phytoplankton community a priori in field mesocosms. We investigated the influence of DVM of the cladoceran Daphnia hyalina on two different phytoplankton communities, by the use of deep (10 m field enclosures. Epilimnetic lake water, containing a summer phytoplankton community, was filtered with two different mesh sizes (11 mm and 64 mm. The 11 mm phytoplankton community (“small” contained mainly small algal species, while the 64 mm community (“large” had a wider range of phytoplankton sizes. To simulate zooplankton DVM, D. hyalina were placed in mesh cages that were lowered or raised (“migration” as dictated by the study design; a “no migration” (representing absence of DVM treatment was also tested. Phytoplankton abundance was measured using chlorophyll-a and biovolume; size distribution of the algae and nutrient availability was also determined in each treatment. The results indicated that DVM had contrasting effects on the two evaluated phytoplankton communities. Comparison of “migration” and “no migration” zooplankton treatments showed that nutrient availability and total phytoplankton biovolume was higher in (1 “no migration” treatments with phytoplankton communities

  15. VIIRS captures phytoplankton vertical migration in the NE Gulf of Mexico.

    Science.gov (United States)

    Qi, Lin; Hu, Chuanmin; Barnes, Brian B; Lee, Zhongping

    2017-06-01

    In summer 2014, a toxic Karenia brevis bloom (red tide) occurred in the NE Gulf of Mexico, during which vertical migration of K. brevis has been observed from glider measurements. The current study shows that satellite observations from the Visible Infrared Imaging Radiometer Suite (VIIRS) can capture changes in surface reflectance and chlorophyll concentration occurring within 2h, which may be attributed this K. brevis vertical migration. The argument is supported by earlier glider measurements in the same bloom, by the dramatic changes in the VIIRS-derived surface chlorophyll, and by the consistency between the short-term reflectance changes and those reported earlier from field-measured K. brevis vertical migration. Estimates using the quasi-analytical algorithm also indicate significant increases in both total absorption coefficient and backscattering coefficient in two hours. The two observations in a day from a single polar-orbiting satellite sensor are thus shown to be able to infer phytoplankton vertical movement within a short timeframe, a phenomenon difficult to capture with other sensors as each sensor can provide at most one observation per day, and cross-sensor inconsistency may make interpretation of merged-sensor data difficult. These findings strongly support geostationary satellite missions to study short-term bloom dynamics. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Visibility Management and the Body

    Science.gov (United States)

    Lasser, Jon; Wicker, Nichole

    2008-01-01

    The authors employed grounded theory to explore the high school experiences of gay, lesbian, and bisexual students in Central Texas. The central phenomenon that emerged from the study was Visibility Management, or decisions made regarding the disclosure of invisible traits. This article reviews the results of this research with an emphasis on the…

  17. Early Learning Theories Made Visible

    Science.gov (United States)

    Beloglovsky, Miriam; Daly, Lisa

    2015-01-01

    Go beyond reading about early learning theories and see what they look like in action in modern programs and teacher practices. With classroom vignettes and colorful photographs, this book makes the works of Jean Piaget, Erik Erikson, Lev Vygotsky, Abraham Maslow, John Dewey, Howard Gardner, and Louise Derman-Sparks visible, accessible, and easier…

  18. Visible fluorescent proteins for FRET

    NARCIS (Netherlands)

    Kremers, G.J.; Goedhart, J.; Gadella, T.W.J.

    2009-01-01

    This chapter discusses the use of Visible fluorescent proteins (VFPs) for FRET studies, a comprehensive table with Förster radii of VFP pairs is presented and recommendations for choosing the right pairs are made. The chapter discusses VFPs that are used for studies that use fluorescence resonance

  19. Technology Advancement of the Visible Nulling Coronagraph

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Petrone, Peter; Thompson, Patrick; Bolcar, Matt; Madison, Timothy; Woodruff, Robert; Noecker, Charley; Kendrick, Steve

    2010-01-01

    The critical high contrast imaging technology for the Extrasolar Planetary Imaging Coronagraph (EPIC) mission concept is the visible nulling coronagraph (VNC). EPIC would be capable of imaging jovian planets, dust/debris disks, and potentially super-Earths and contribute to answering how bright the debris disks are for candidate stars. The contrast requirement for EPIC is 10(exp 9) contrast at 125 milli-arseconds inner working angle. To advance the VNC technology NASA/Goddard Space Flight Center, in collaboration with Lockheed-Martin, previously developed a vacuum VNC testbed, and achieved narrowband and broadband suppression of the core of the Airy disk. Recently our group was awarded a NASA Technology Development for Exoplanet Missions to achieve two milestones: (i) 10(exp 8) contrast in narrowband light, and, (ii) 10(ecp 9) contrast in broader band light; one milestone per year, and both at 2 Lambda/D inner working angle. These will be achieved with our 2nd generation testbed known as the visible nulling testbed (VNT). It contains a MEMS based hex-packed segmented deformable mirror known as the multiple mirror array (MMA) and coherent fiber bundle, i.e. a spatial filter array (SFA). The MMA is in one interferometric arm and works to set the wavefront differences between the arms to zero. Each of the MMA segments is optically mapped to a single mode fiber of the SFA, and the SFA passively cleans the sub-aperture wavefront error leaving only piston, tip and tilt error to be controlled. The piston degree of freedom on each segment is used to correct the wavefront errors, while the tip/tilt is used to simultaneously correct the amplitude errors. Thus the VNT controls both amplitude and wavefront errors with a single MMA in closed-loop in a vacuum tank at approx.20 Hz. Herein we will discuss our ongoing progress with the VNT.

  20. Bacterial and protist community changes during a phytoplankton bloom

    KAUST Repository

    Pearman, John K.

    2015-10-01

    The present study aims to characterize the change in the composition and structure of the bacterial and microzooplankton planktonic communities in relation to the phytoplankton community composition during a bloom. High-throughput amplicon sequencing of regions of the 16S and 18S rRNA gene was undertaken on samples collected during a 20 day (d) mesocosm experiment incorporating two different nutrient addition treatments [Nitrate and Phosphate (NPc) and Nitrate, Phosphate and Silicate (NPSc)] as well as a control. This approach allowed us to discriminate the changes in species composition across a broad range of phylogenetic groups using a common taxonomic level. Diatoms dominated the bloom in the NPSc treatment while dinoflagellates were the dominant phytoplankton in the control and NPc treatment. Network correlations highlighted significant interactions between OTUs within each treatment including changes in the composition of Paraphysomonas OTUs when the dominant Chaetoceros OTU switched. The microzooplankton community composition responded to changes in the phytoplankton composition while the prokaryotic community responded more to changes in ammonia concentration.

  1. Distribution of phytoplankton groups within the deep chlorophyll maximum

    KAUST Repository

    Latasa, Mikel

    2016-11-01

    The fine vertical distribution of phytoplankton groups within the deep chlorophyll maximum (DCM) was studied in the NE Atlantic during summer stratification. A simple but unconventional sampling strategy allowed examining the vertical structure with ca. 2 m resolution. The distribution of Prochlorococcus, Synechococcus, chlorophytes, pelagophytes, small prymnesiophytes, coccolithophores, diatoms, and dinoflagellates was investigated with a combination of pigment-markers, flow cytometry and optical and FISH microscopy. All groups presented minimum abundances at the surface and a maximum in the DCM layer. The cell distribution was not vertically symmetrical around the DCM peak and cells tended to accumulate in the upper part of the DCM layer. The more symmetrical distribution of chlorophyll than cells around the DCM peak was due to the increase of pigment per cell with depth. We found a vertical alignment of phytoplankton groups within the DCM layer indicating preferences for different ecological niches in a layer with strong gradients of light and nutrients. Prochlorococcus occupied the shallowest and diatoms the deepest layers. Dinoflagellates, Synechococcus and small prymnesiophytes preferred shallow DCM layers, and coccolithophores, chlorophytes and pelagophytes showed a preference for deep layers. Cell size within groups changed with depth in a pattern related to their mean size: the cell volume of the smallest group increased the most with depth while the cell volume of the largest group decreased the most. The vertical alignment of phytoplankton groups confirms that the DCM is not a homogeneous entity and indicates groups’ preferences for different ecological niches within this layer.

  2. Environmental Conditions Determine the Course and Outcome of Phytoplankton Chytridiomycosis.

    Directory of Open Access Journals (Sweden)

    Thomas Rohrlack

    Full Text Available Chytrid fungi are highly potent parasites of phytoplankton. They are thought to force phytoplankton organisms into an evolutionary arms race with high population diversity as the outcome. The underlying selection regime is known as Red Queen dynamics. However, our study suggests a more complex picture for chytrid parasitism in the cyanobacterium Planktothrix. Laboratory experiments identified a "cold thermal refuge", inside which Planktothrix can grow without chytrid infection. A field study in two Norwegian lakes underlined the ecological significance of this finding. The study utilized sediment DNA as a biological archive in combination with existing monitoring data. In one lake, temperature and light conditions forced Planktothrix outside the thermal refuge for most of the growing season. This probably resulted in Red Queen dynamics as suggested by a high parasitic pressure exerted by chytrids, an increase in Planktothrix genotype diversity over time, and a correlation between Planktothrix genotype diversity and duration of bloom events. In the second lake, a colder climate allowed Planktothrix to largely stay inside the thermal refuge. The parasitic pressure exerted by chytrids and Planktothrix genotype diversity remained low, indicating that Planktothrix successfully evaded the Red Queen dynamics. Episodic Planktothrix blooms were observed during spring and autumn circulation, in the metalimnion or under the ice. Interestingly, both lakes were dominated by the same or related Planktothrix genotypes. Taken together, our data suggest that, depending on environmental conditions, chytrid parasitism can impose distinct selection regimes on conspecific phytoplankton populations with similar genotype composition, causing these populations to behave and perhaps to evolve differently.

  3. [Temporal dynamics of phytoplankton and nutrients during red tides].

    Science.gov (United States)

    Qiu, Yaowen; Zhu, Liangsheng; Li, Jinrong; Liang, Song; Qi, Yuzao

    2003-07-01

    The relationships between temporal dynamics of phytoplankton density and nutrients (NO3-, NH4+, PO4(3-), SiO3(2-), Fe) contents in the water body at Aotou waters of Daya Bay during red tide were comprehensively analysed based on the fixed position investigation of red tide in the summer of 2000 and the several years investigation data by using grey linear regression model. The relationships between phytoplankton cell density and chlorophyll a content were also analysed. The results showed that the predicted values were well consistent with the measurement values, and their correlation coefficients were between 0.51-0.83. Red tide might break out if chlorophyll a contents in water body were larger than 5.8 micrograms.dm-3. The study could provide a simple effective method to forecast red tide by sampling water samples to analyse chlorophyll a concentration, or using SeaWiFS data, and then, to calculating phytoplankton density. In addition, the primary productivity of the water areas was controlled by phosphorus.

  4. Abundance, Composition and Distribution of Phytoplankton in Calamianes, Palawan

    Directory of Open Access Journals (Sweden)

    Jules Jason C Asis

    2006-12-01

    Full Text Available Phytoplankton in Coron Bay of the Calamianes Islands, Palawan were investigated from 27-29 May2004. Samples were collected from 33 stations by filtering five 10 L buckets of surface water througha net with a 20mm mesh bag. The phytoplankton consisted of four major groups. Diatoms, showed thehighest mean density of 1432.9indivL-1. Silicoflagellates comprised the next most abundant group witha mean density of 132.3 indivL-1. Dinoflagellates followed with a mean density of 94.8 indivL-1, while thecyanobacteria (blue-green algae had a mean density of 19.4 indivL-1. The top three diatoms wereChaetoceros, Bacteriastrum and Coscinodiscus. The genus Peridinium was the most abundantdinoflagellate, while Tintinnopsis dominated the silicoflagellates. Among the cyanophytes, Trichodesmiumshowed the highest density. High phytoplankton concentrations were observed in the vicinity of a pearlfarm and in areas adjacent to mangrove forests. Overall abundance and diversity in the study area arehigher than in other similarly reef-dominated areas in the country. This may be attributed to factors onboth large and local scales.

  5. On the variation of alkalinity during phytoplankton photosynthesis

    Directory of Open Access Journals (Sweden)

    2005-01-01

    Full Text Available The alkalinity of the organic constituents of marine phytoplankton and their participation in the total alkalinity (TA change of seawater during photosynthesis are carefully assessed. Quantification of the contribution of phytoplankton chlorophyll, proteins and phosphorus compounds to the hydrogen ion balance of seawater in terms of total inorganic nitrogen (∆[NT] = ∆[NH4 +] + ∆[N2] + ∆[NO2 –] + ∆[NO3 –] and total inorganic phosphorus (∆[PT] changes during photosynthesis yielded that the organic components of marine phytoplankton are alkaline by –0.06 × ∆[NT] – 0.49 × ∆[PT], and that the potential total alkalinity (TAP during photosynthesis is TAP = TA – [NH4 –] + 0.93 × [NO2 –] + [NO3 –] + 0.08 × [NT] + 0.23 × [PT] for unfiltered seawater samples and TAP = TA – [NH4 –] + 0.93 × [NO2 –] + [NO3 –] + 0.02 × [NT] + 0.26 × [PT] for filtered seawater samples. These equations correct the traditionally used expression TAP = TA + [NO3 –]. The TAP anomalies are produced, in order of increasing importance, by N2 fixation, DMSP production and CaCO3 fixation.

  6. Selection of phytoplankton species in culture by gradual salinity changes

    Science.gov (United States)

    Rijstenbil, J. W.

    Continuous cultures of mixed phytoplankton populations were subjected to gradual salinity changes. The phytoplankton was exposed to defined regimes of high, low or fluctuating salinity, in artificial brackish media. In several experiments ammonium was the limiting nutrient. A rapid selection process was observed in natural phytoplankton assemblages. A gradual freshening caused the dominance of Chaetoceros mülleri at low salinity (S = 5). Skeletonema costatum became dominant at higher, constant or fluctuating salinities, accompanied by Ditylum brightwellii in low cell numbers. Ammonium limitation was not achieved in this experiment. Competition for ammonium was studied in a second experiment, using an inoculum of two species. At S = 18 D. brighwellii became the dominant species in this competition. A minor shift towards S = 15 reversed the affinities for ammonium, and S. costatum won the competition. At S = 8 S. costatum had the highest affinity for ammonium after a period of osmotic adjustment. Ammonium became limiting when salinities arrived at constant meso- or polyhaline levels. Both species were able to grow in fluctuating osmotic environments (S = 5 to 19). The growth of D. brightwellii decreased below S = 8 and after repeated variations of the salinity. These salinity fluctuations suppressed growth and ammonium uptake of both species, thus preventing ammonium limitation. These competition experiments indicate that unstable salinity may stimulate the mass development of S. costatum in brackish lakes.

  7. Hydrodynamic control of phytoplankton loss to the benthos in an estuarine environment

    Science.gov (United States)

    Jones, Nicole L.; Thompson, Janet K.; Arrigo, Kevin R.; Monismith, Stephen G.

    2009-01-01

    Field experiments were undertaken to measure the influence of hydrodynamics on the removal of phytoplankton by benthic grazers in Suisun Slough, North San Francisco Bay. Chlorophyll a concentration boundary layers were found over beds inhabited by the active suspension feeders Corbula amurensis and Corophium alienense and the passive suspension feeders Marenzellaria viridis and Laonome sp. Benthic losses of phytoplankton were estimated via both the control volume and the vertical flux approach, in which chlorophyll a concentration was used as a proxy for phytoplankton biomass. The rate of phytoplankton loss to the bed was positively correlated to the bed shear stress. The maximum rate of phytoplankton loss to the bed was five times larger than estimated by laboratory-derived pumping rates for the active suspension feeders. Reasons for this discrepancy are explored including a physical mechanism whereby phytoplankton is entrained in a near-bed fluff layer where aggregation is mediated by the presence of mucus produced by the infaunal community.

  8. Phytoplankton response to winter warming modified by large-bodied zooplankton: an experimental microcosm study

    Directory of Open Access Journals (Sweden)

    Hu He

    2015-03-01

    Full Text Available While several field investigations have demonstrated significant effects of cool season (winter or spring warming on phytoplankton development, the role played by large-bodied zooplankton grazers for the responses of phytoplankton to winter warming is ambiguous. We conducted an outdoor experiment to compare the effect of winter warming (heating by 3°C in combination with presence and absence of Daphnia grazing (D. similis on phytoplankton standing crops and community structure under eutrophic conditions. When Daphnia were absent, warming was associated with significant increases in phytoplankton biomass and cyanobacterial dominance. In contrast, when Daphnia were present, warming effects on phytoplankton dynamics were offset by warming-enhanced grazing, resulting in no significant change in biomass or taxonomic dominance. These results emphasize that large-bodied zooplankton like Daphnia spp. may play an important role in modulating the interactions between climate warming and phytoplankton dynamics in nutrient rich lake ecosystems.

  9. Interannual Variation in Phytoplankton Primary Production at a Global Scale

    Science.gov (United States)

    Rousseaux, Cecile Severine; Gregg, Watson W.

    2013-01-01

    We used the NASA Ocean Biogeochemical Model (NOBM) combined with remote sensing data via assimilation to evaluate the contribution of four phytoplankton groups to the total primary production. First, we assessed the contribution of each phytoplankton groups to the total primary production at a global scale for the period 1998-2011. Globally, diatoms contributed the most to the total phytoplankton production ((is)approximately 50%, the equivalent of 20 PgC·y1). Coccolithophores and chlorophytes each contributed approximately 20% ((is) approximately 7 PgC·y1) of the total primary production and cyanobacteria represented about 10% ((is) approximately 4 PgC·y1) of the total primary production. Primary production by diatoms was highest in the high latitudes ((is) greater than 40 deg) and in major upwelling systems (Equatorial Pacific and Benguela system). We then assessed interannual variability of this group-specific primary production over the period 1998-2011. Globally the annual relative contribution of each phytoplankton groups to the total primary production varied by maximum 4% (1-2 PgC·y1). We assessed the effects of climate variability on group-specific primary production using global (i.e., Multivariate El Niño Index, MEI) and "regional" climate indices (e.g., Southern Annular Mode (SAM), Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO)). Most interannual variability occurred in the Equatorial Pacific and was associated with climate variability as indicated by significant correlation (p (is) less than 0.05) between the MEI and the group-specific primary production from all groups except coccolithophores. In the Atlantic, climate variability as indicated by NAO was significantly correlated to the primary production of 2 out of the 4 groups in the North Central Atlantic (diatoms/cyanobacteria) and in the North Atlantic (chlorophytes and coccolithophores). We found that climate variability as indicated by SAM had only a limited effect

  10. [Studies on relationship of phytoplankton and water environmental factors in Shahu Lake].

    Science.gov (United States)

    Qiu, Xiao-Cong; Zhao, Hong-Xue; Sun, Xiao-Xue

    2012-07-01

    Analysis approaches of correlation, multiple stepwise regression and canonical correspondence analysis were employed between phytoplankton and water environmental factors in ShaHu Lake based on the data from Apr. 2009 to Jan. 2010. The results showed that the correlation between phytoplankton density, phytoplankton biomass, chlorophyll-a and water temperature (WT), total nitrogen (TN), total phosphorus (TP), potassium permanganate index,5 days biochemical oxygen demand (BOD5) was positive, and phytoplankton density, phytoplankton biomass, chlorophyll-a and Secchi-depth (SD) was negatively correlated. Followed by the importance of environmental factors which affected phytoplankton density in Shahu Lake ranged as follows: WT, potassium permanganate index, SD, BOD5, TP, TN. Those affected phytoplankton biomass ranged as follows: WT,TP, potassium permanganate index,SD,TN. Those affected on chlorophyll-a ranged as follows: potassium permanganate index, WT, SD, TP, TN, BOD5. CCA result showed that 16 species of phytoplankton were divided into 3 groups which had the obvious seasonal distribution characteristics in Shahu Lake. SD, potassium permanganate index,WT, TN, TP were the main water environmental factors correlated with the distribution of phytoplankton community of Shahu Lake.

  11. Temporal and spatial variations in phytoplankton: correlations with environmental factors in Shengjin Lake, China.

    Science.gov (United States)

    Wang, Lan; Wang, Chao; Deng, Daogui; Zhao, Xiuxia; Zhou, Zhongze

    2015-09-01

    Temporal and spatial variations in the phytoplankton community and environmental variables were investigated from February to July 2014, in the upper lake of Shengjin Lake, China. We identified 192 species of phytoplankton belonging to 8 phyla and 84 genera, of which 46.4% of Chlorophyta, 29.2% of Bacillariophyta, and 12.5% of Cyanophyta. There were 14 predominant species. Marked temporal and spatial variations were observed in the phytoplankton community. The total abundance of phytoplankton ranged from 3.66 × 10(5) to 867.93 × 10(5) cells/L and total biomass ranging from 0.40 to 20.89 mg/L. The Shannon-Wiener diversity index varied from 3.50 to 8.35 with an average of 5.58, revealing high biodiversity in the phytoplankton community. There were substantial temporal changes in the dominant species, from Bacillariophyta and Cryptophyta to Cyanophyta and Chlorophyta. Phytoplankton biomass and abundance showed a similar increasing trend from February to July. Pearson correlations and Redundancy analysis revealed that the most significant environmental factors influencing phytoplankton community were water temperature (T), transparency (SD), and nutrient concentration. The positive correlation between the key water bird areas and phytoplankton biomass indicated that the droppings of wintering water birds had an important influence on the phytoplankton community in the upper lake of Shengjin Lake.

  12. Phytoplankton Diversity Effects on Community Biomass and Stability along Nutrient Gradients in a Eutrophic Lake

    Directory of Open Access Journals (Sweden)

    Wang Tian

    2017-01-01

    Full Text Available The relationship between biodiversity and ecosystem functioning is a central issue in ecology, but how this relationship is affected by nutrient stress is still unknown. In this study, we analyzed the phytoplankton diversity effects on community biomass and stability along nutrient gradients in an artificial eutrophic lake. Four nutrient gradients, varying from slightly eutrophic to highly eutrophic states, were designed by adjusting the amount of polluted water that flowed into the lake. Mean phytoplankton biomass, species richness, and Shannon diversity index all showed significant differences among the four nutrient gradients. Phytoplankton community biomass was correlated with diversity (both species richness and Shannon diversity index, varying from positive to negative along the nutrient gradients. The influence of phytoplankton species richness on resource use efficiency (RUE also changed from positive to negative along the nutrient gradients. However, the influence of phytoplankton Shannon diversity on RUE was not significant. Both phytoplankton species richness and Shannon diversity had a negative influence on community turnover (measured as community dissimilarity, i.e., a positive diversity–stability relationship. Furthermore, phytoplankton spatial stability decreased along the nutrient gradients in the lake. With increasing nutrient concentrations, the variability (standard deviation of phytoplankton community biomass increased more rapidly than the average total biomass. Results in this study will be helpful in understanding the phytoplankton diversity effects on ecosystem functioning and how these effects are influenced by nutrient conditions in aquatic ecosystems.

  13. Annual cycle and composition of the phytoplankton in the Quempillen River Estuary, southern Chile

    Science.gov (United States)

    Toro, J. E.

    1985-10-01

    Phytoplankton species and abundance were studied in the Quempillen River Estuary, from August 1979 to July 1980 in addition to some important environmental factors: salinity, temperature and dissolved oxygen. In order to determine the seasonal variations in cell density and biomass of the phytoplankton in this brackish aquatic environment, phytoplankton data obtained by the Uthermöhl (1958) technique were analysed. A total of 109 phytoplankton species were identified within the samples. Throughout the year there were two periods of population maxima, September and May, and one period of high biomass, February. The phytoflagellates were always present but only dominated the flora when diatoms were extremely reduced, especially during low tide periods.

  14. Phytoplankton Diversity Effects on Community Biomass and Stability along Nutrient Gradients in a Eutrophic Lake.

    Science.gov (United States)

    Tian, Wang; Zhang, Huayong; Zhao, Lei; Zhang, Feifan; Huang, Hai

    2017-01-20

    The relationship between biodiversity and ecosystem functioning is a central issue in ecology, but how this relationship is affected by nutrient stress is still unknown. In this study, we analyzed the phytoplankton diversity effects on community biomass and stability along nutrient gradients in an artificial eutrophic lake. Four nutrient gradients, varying from slightly eutrophic to highly eutrophic states, were designed by adjusting the amount of polluted water that flowed into the lake. Mean phytoplankton biomass, species richness, and Shannon diversity index all showed significant differences among the four nutrient gradients. Phytoplankton community biomass was correlated with diversity (both species richness and Shannon diversity index), varying from positive to negative along the nutrient gradients. The influence of phytoplankton species richness on resource use efficiency (RUE) also changed from positive to negative along the nutrient gradients. However, the influence of phytoplankton Shannon diversity on RUE was not significant. Both phytoplankton species richness and Shannon diversity had a negative influence on community turnover (measured as community dissimilarity), i.e., a positive diversity-stability relationship. Furthermore, phytoplankton spatial stability decreased along the nutrient gradients in the lake. With increasing nutrient concentrations, the variability (standard deviation) of phytoplankton community biomass increased more rapidly than the average total biomass. Results in this study will be helpful in understanding the phytoplankton diversity effects on ecosystem functioning and how these effects are influenced by nutrient conditions in aquatic ecosystems.

  15. Riverine phytoplankton shifting along a lentic-lotic continuum under hydrological, physiochemical conditions and species dispersal.

    Science.gov (United States)

    Qu, Yueming; Wu, Naicheng; Guse, Björn; Fohrer, Nicola

    2017-10-21

    The importance of phytoplankton-based bio-assessment has been recently recognized in lowland rivers which are affected by multi-environmental factors. However, some basic questions remain unclear to date, such as: (i) spatial and temporal variations of phytoplankton, (ii) the impact of upstream lakes on downstream community, (iii) the main drivers for species composition or (iv) the regional biodiversity along a lentic-lotic continuum. To answer these questions, we collected and analyzed the fluvial phytoplankton communities along a lentic-lotic continuum from a German lowland catchment, where a well-established ecohydrological modeling predicted long-term discharges at each sampling site. Our results revealed very high spatial and temporal variations of phytoplankton community. The changes of a lake on downstream phytoplankton assemblages were significant, especially the nearest reach after the lake. However, these influences varied along with seasons and limited in a relatively short distance to the lake. Redundancy analysis and Mantel tests showed that phytoplankton composition and dissimilarities along the lentic-lotic continuum attributed more to local hydrological and physicochemical variables than species dispersal, which confirmed the suitability of lowland phytoplankton-based bioassessment. In addition, our findings highlighted the importance of flow regime in shaping phytoplankton community composition and regional beta diversities. This study emphasized the necessity to include the hydrological variables and their relationship with phytoplankton community in future bio-monitoring investigations. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Phytoplankton community and limnology of Chatla floodplain wetland of Barak valley, Assam, North-East India

    Directory of Open Access Journals (Sweden)

    Sultana Laskar H.

    2013-09-01

    Full Text Available Phytoplankton diversity was investigated over a period of two years (2006 to 2008 in Chatla floodplain wetland in Barak valley, Assam, North-East India. Site 1 and site 2 are two inlets and site 3 is a lentic system associated with vegetation cover of Calamus tenuis and Baringtonia acutangula. The floodplain has a unique hydrology because of the presence of different types of habitats (inlets, fisheries, beels and outlets which maintains a network among the floodplains, rivers and streams. Phytoplankton community composition, density and diversity were studied in relation to environmental variables. All the variables were estimated by following standard methods. Phytoplankton was collected by plankton net and quantitative estimation was made by using Sedgwick Rafter counting cell. Phytoplankton community comprised 53 taxa represented by Chlorophyceae (31, Cyanophyceae (11, Bacillariophyceae (7, Euglenophyceae (1 and Dinophyceae (3. Phytoplankton taxa was dominated by Volvox sp., Nostoc sp., Eunotia sp., Navicula sp., Euglena spp. and density was found highest in site 3 and lowest in site 1. Shannon diversity index (H′ for phytoplankton community varied between 2.4 to 2.65 indicating fairly high species diversity. The varying magnitude of correlationship among environmental variables and phytoplankton species density as shown by Canonical correspondence analysis (CCA indicated that some of the environmental variables (water temperature, transparency, rainfall, nitrate and ammonia are the driving factors for governing the phytoplankton species assemblages in Chatla floodplain wetland. Fluctuation of phytoplankton density and community composition in different habitats indicated various niche apportionment as well as anthropogenic influences.

  17. Ultraviolet, Visible, and Fluorescence Spectroscopy

    Science.gov (United States)

    Penner, Michael H.

    Spectroscopy in the ultraviolet-visible (UV-Vis) range is one of the most commonly encountered laboratory techniques in food analysis. Diverse examples, such as the quantification of macrocomponents (total carbohydrate by the phenol-sulfuric acid method), quantification of microcomponents, (thiamin by the thiochrome fluorometric procedure), estimates of rancidity (lipid oxidation status by the thiobarbituric acid test), and surveillance testing (enzyme-linked immunoassays), are presented in this text. In each of these cases, the analytical signal for which the assay is based is either the emission or absorption of radiation in the UV-Vis range. This signal may be inherent in the analyte, such as the absorbance of radiation in the visible range by pigments, or a result of a chemical reaction involving the analyte, such as the colorimetric copper-based Lowry method for the analysis of soluble protein.

  18. Seasonal distribution of phytoplankton assemblages and nutrient-enriched bioassays as indicators of nutrient limitation of phytoplankton growth in Gwangyang Bay, Korea

    Science.gov (United States)

    Baek, Seung Ho; Kim, Dongseon; Son, Moonho; Yun, Suk Min; Kim, Young Ok

    2015-09-01

    To assess the effect of nutrient limitation on phytoplankton growth, and its influence on seasonal variation in phytoplankton community structure, we investigated abiotic and biotic factors in surface and bottom waters at 20 stations in inner and offshore areas of Gwangyang Bay, Korea. Algal bioassay experiments were also conducted using surface water, to assess the effects of nutrient addition on the phytoplankton assemblages. The fate of major nutrients in the bay was strongly dependent on the discharge of freshwater from the Seomjin River. River flow during the rainy season provides a high nitrogen (N) influx, pushing the system toward stoichiometric phosphorus (P) limitation. However, at some times during the rainy season there was insufficient N to maintain phytoplankton growth because it was rapidly consumed through nutrient uptake by phytoplankton under stratified environmental conditions. Diatoms made a relatively large contribution to total phytoplankton biomass. The dominant diatoms, particularly in winter and summer, were Skeletonema marinoi-dohrnii complex and Skeletonema tropicum, respectively, while Eucampia zodiacus and the cryptophyte Cryptomonas spp. dominated in spring and autumn, respectively, comprising more than 75% of the community at most stations. In the bioassay experiments the phytoplankton biomass increased by 30-600% in the +N (added nitrogen) and +NP (added nitrogen and phosphorus) treatments relative to the control and the +P (added phosphorus) treatments, indicating that phytoplankton growth can respond rapidly to pulsed nitrate loading events. Based on the algal bioassay and the field survey, the abrupt input of high nutrient levels following rainfall stimulated the growth of diatom assemblages including the Skeletonema genus. Our results demonstrate that the growth of centric diatoms was enhanced by inputs of N and Si, and that the concentrations of these nutrients may be among the most important factors controlling phytoplankton

  19. Book Review: Making Thinking Visible

    OpenAIRE

    ROYAL, KENNETH; Hardie, Lizette

    2015-01-01

    Recent trends in medical education emphasize the importance of producing well-rounded graduates who not only possess a sufficient fund of medical knowledge but who can think clearly and deeply. Unfortunately, many medical educators struggle with what exactly it means to ?think? and do not know where to begin when asked to teach ?thinking.? We believe the book Making Thinking Visible, though written for K-12, will be of great interest to medical educators. The book describes different types of...

  20. Visibility of halos and rainbows.

    Science.gov (United States)

    Gedzelman, S D

    1980-09-15

    A theory for the visibility of halos and rainbows is presented. The light reaching the observer's eye from the direction of the halo or rainbow is assumed to consist of two parts: (1) a beam of singly scattered sunlight (or moonlight) from a cloud of ice crystals or a rainswath, which, in turn, has suffered depletion by scattering or absorption in its passage to the observer, and (2) the general background brightness. The model is able to account for several long-known qualitative observations concerning halos, namely, that the brightest halos are produced by optically thin cirrostratus clouds (i.e., for which the cloud optical depth tau(c), rainbow the brightness of the beam increases monotonically with the optical depth tau(R) of the sunlit part of the rainswath, but the increase is quite small for tau(R) >/=1. On the other hand, the brightness of the background increases more rapidly with tau(R) for tau(R)> 1 so that the rainbow appears most easily visible for tau(R) less, similar1. This implies that the most easily visible rainbows are produced by light or moderate showers rather than heavy downpours. Finally, suggestions are made for applying the theory to other atmospheric optical phenomena, such as coronas and glories.

  1. Size Class Dependent Relationships between Temperature and Phytoplankton Photosynthesis-Irradiance Parameters in the Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    Alex Robinson

    2018-01-01

    Full Text Available Over the past decade, a number of methods have been developed to estimate size-class primary production from either in situ phytoplankton pigment data or remotely-sensed data. In this context, the first objective of this study was to compare two methods of estimating size class specific (micro-, nano-, and pico-phytoplankton photosynthesis-irradiance (PE parameters from pigment data. The second objective was to analyse the relationship between environmental variables (temperature, nitrate and PAR and PE parameters in the different size-classes. A large dataset was used of simultaneous measurements of the PE parameters (n = 1,260 and phytoplankton pigment markers (n = 2,326, from 3 different institutes. There were no significant differences in mean PE parameters of the different size classes between the chemotaxonomic method of Uitz et al. (2008 and the pigment markers and carbon-to-Chl a ratios method of Sathyendranath et al. (2009. For both methods, mean maximum photosynthetic rates (PmB for micro-phytoplankton were significantly lower than those for pico-phytoplankton and nano-phytoplankton. The mean light limited slope (αB for nano-phytoplankton were significantly higher than for the other size taxa. For micro-phytoplankton dominated samples identified using the Sathyendranath et al. (2009 method, both PmB and αB exhibited a significant, positive linear relationship with temperature, whereas for pico-phytoplankton the correlation with temperature was negative. Nano-phytoplankton dominated samples showed a positive correlation between PmB and temperature, whereas for αB and the light saturation parameter (Ek the correlations were not significant. For the Uitz et al. (2008 method, only micro-phytoplankton PmB, pico-phytoplankton αB, nano- and pico-phytoplankton Ek exhibited significant relationships with temperature. The temperature ranges occupied by the size classes derived using these methods differed. The Uitz et al. (2008 method

  2. Small phytoplankton contribution to the standing stocks and the total primary production in the Amundsen Sea

    Directory of Open Access Journals (Sweden)

    S. H. Lee

    2017-08-01

    Full Text Available Small phytoplankton are anticipated to be more important in a recently warming and freshening ocean condition. However, little information on the contribution of small phytoplankton to overall phytoplankton production is currently available in the Amundsen Sea. To determine the contributions of small phytoplankton to total biomass and primary production, carbon and nitrogen uptake rates of total and small phytoplankton were obtained from 12 productivity stations in the Amundsen Sea. The daily carbon uptake rates of total phytoplankton averaged in this study were 0.42 g C m−2 d−1 (SD  =  ± 0.30 g C m−2 d−1 and 0.84 g C m−2 d−1 (SD  =  ± 0.18 g C m−2 d−1 for non-polynya and polynya regions, respectively, whereas the daily total nitrogen (nitrate and ammonium uptake rates were 0.12 g N m−2 d−1 (SD  =  ± 0.09 g N m−2 d−1 and 0.21 g N m−2 d−1 (SD  =  ± 0.11 g N m−2 d−1, respectively, for non-polynya and polynya regions, all of which were within the ranges reported previously. Small phytoplankton contributed 26.9 and 27.7 % to the total carbon and nitrogen uptake rates of phytoplankton in this study, respectively, which were relatively higher than the chlorophyll a contribution (19.4 % of small phytoplankton. For a comparison of different regions, the contributions for chlorophyll a concentration and primary production of small phytoplankton averaged from all the non-polynya stations were 42.4 and 50.8 %, which were significantly higher than those (7.9 and 14.9 %, respectively in the polynya region. A strong negative correlation (r2 = 0. 790, p<0. 05 was found between the contributions of small phytoplankton and the total daily primary production of phytoplankton in this study. This finding implies that daily primary production decreases as small phytoplankton contribution increases, which is

  3. Phytoplankton Distribution in Relation to Environmental Drivers on the North West European Shelf Sea.

    Science.gov (United States)

    Siemering, Beatrix; Bresnan, Eileen; Painter, Stuart C; Daniels, Chris J; Inall, Mark; Davidson, Keith

    2016-01-01

    The edge of the North West European Shelf (NWES) is characterised by a steep continental slope and a northward flowing slope current. These topographic/hydrographic features separate oceanic water and shelf water masses hence potentially separate phytoplankton communities. The slope current may facilitate the advective transport of phytoplankton, with mixing at the shelf edge supporting nutrient supply and therefore phytoplankton production. On the west Scottish shelf in particular, little is known about the phytoplankton communities in and around the shelf break and adjacent waters. Hence, to improve our understanding of environmental drivers of phytoplankton communities, biological and environmental data were collected on seven cross-shelf transects across the Malin and Hebridean Shelves during autumn 2014. Density profiles indicated that shelf break and oceanic stations had a 100 m deep mixed surface layer while stations on the shelf were generally well mixed. Analysis of similarity and multidimensional scaling of phytoplankton counts revealed that phytoplankton communities on the shelf were significantly different to those found at the shelf break and at oceanic stations. Shelf stations were dominated by dinoflagellates, with diatoms contributing a maximum of 37% of cells. Shelf break and oceanic stations were also dinoflagellate dominated but displayed a lower species diversity. Significant difference between shelf and shelf break stations suggested that the continental slope limited cross shelf phytoplankton exchange. Northern and southern phytoplankton communities on the shelf were approximately 15% dissimilar while there was no latitudinal gradient for stations along the slope current, suggesting this current provided south to north connectivity. Fitting environmental data to phytoplankton ordination showed a significant relationship between phytoplankton community dissimilarities and nutrient concentrations and light availability on the shelf compared to

  4. STS-4 earth observations from space

    Science.gov (United States)

    1982-01-01

    STS-4 earth observations from space. Views include both Florida coasts, with Cape Canaveral visible at the center of the frame. The photo was exposed through the aft window on the flight deck of the Columbia. The vertical tail and both orbital maneuvering systems (OMS) pods are visible in the foreground. Other features on the Earth which are visible include Tampa Bay and several lakes, including Apopka, Tohopekaliga, East Tahopekaliga, Harris, Cypress and a number of small reservoirs (33223); This is a north-easterly looking view toward California's Pacific Coast. The coastal area covered includes San Diego northward to Pismo Beach. Los Angeles is near center. The arc of the Temblor-Tehachapi-Sierra Nevada surrounds the San Joaquin Valley at left. The Mojave desert lies between the San Andres and Garlock Faults (33224); Mexico's Baja California and Sonora state are visible in the STS-4 frame. The islands of Angel de la Guardia and Tiburon stand out above and right of center. Low clouds

  5. Shifts in bacterial community composition associated with increased carbon cycling in a mosaic of phytoplankton blooms.

    Science.gov (United States)

    Landa, Marine; Blain, Stéphane; Christaki, Urania; Monchy, Sébastien; Obernosterer, Ingrid

    2016-01-01

    Marine microbes have a pivotal role in the marine biogeochemical cycle of carbon, because they regulate the turnover of dissolved organic matter (DOM), one of the largest carbon reservoirs on Earth. Microbial communities and DOM are both highly diverse components of the ocean system, yet the role of microbial diversity for carbon processing remains thus far poorly understood. We report here results from an exploration of a mosaic of phytoplankton blooms induced by large-scale natural iron fertilization in the Southern Ocean. We show that in this unique ecosystem where concentrations of DOM are lowest in the global ocean, a patchwork of blooms is associated with diverse and distinct bacterial communities. By using on-board continuous cultures, we identify preferences in the degradation of DOM of different reactivity for taxa associated with contrasting blooms. We used the spatial and temporal variability provided by this natural laboratory to demonstrate that the magnitude of bacterial production is linked to the extent of compositional changes. Our results suggest that partitioning of the DOM resource could be a mechanism that structures bacterial communities with a positive feedback on carbon cycling. Our study, focused on bacterial carbon processing, highlights the potential role of diversity as a driving force for the cycling of biogeochemical elements.

  6. A universal driver of macroevolutionary change in the size of marine phytoplankton over the Cenozoic.

    Science.gov (United States)

    Finkel, Z V; Sebbo, J; Feist-Burkhardt, S; Irwin, A J; Katz, M E; Schofield, O M E; Young, J R; Falkowski, P G

    2007-12-18

    The size structure of phytoplankton assemblages strongly influences energy transfer through the food web and carbon cycling in the ocean. We determined the macroevolutionary trajectory in the median size of dinoflagellate cysts to compare with the macroevolutionary size change in other plankton groups. We found the median size of the dinoflagellate cysts generally decreases through the Cenozoic. Diatoms exhibit an extremely similar pattern in their median size over time, even though species diversity of the two groups has opposing trends, indicating that the macroevolutionary size change is an active response to selection pressure rather than a passive response to changes in diversity. The changes in the median size of dinoflagellate cysts are highly correlated with both deep ocean temperatures and the thermal gradient between the surface and deep waters, indicating the magnitude and frequency of nutrient availability may have acted as a selective factor in the macroevolution of cell size in the plankton. Our results suggest that climate, because it affects stratification in the ocean, is a universal abiotic driver that has been responsible for macroevolutionary changes in the size structure of marine planktonic communities over the past 65 million years of Earth's history.

  7. Biophysical modelling of phytoplankton communities from first principles using two-layered spheres: Equivalent Algal Populations (EAP) model

    CSIR Research Space (South Africa)

    Robertson Lain, L

    2014-07-01

    Full Text Available in various inland waters in Southern Africa present valuable opportunities for the development of such modelling capabilities. The phytoplankton-dominated signal of these waters additionally addresses an increased interest in Phytoplankton Functional Type...

  8. Beyond Language Equivalence on Visibly Pushdown Automata

    DEFF Research Database (Denmark)

    Srba, Jiri

    2009-01-01

    We study (bi)simulation-like preorder/equivalence checking on the class of visibly pushdown automata and its natural subclasses visibly BPA (Basic Process Algebra) and visibly one-counter automata. We describe generic methods for proving complexity upper and lower bounds for a number of studied...... preorders and equivalences like simulation, completed simulation, ready simulation, 2-nested simulation preorders/equivalences and bisimulation equivalence. Our main results are that all the mentioned equivalences and preorders are EXPTIME-complete on visibly pushdown automata, PSPACE-complete on visibly...... one-counter automata and P-complete on visibly BPA. Our PSPACE lower bound for visibly one-counter automata improves also the previously known DP-hardness results for ordinary one-counter automata and one-counter nets. Finally, we study regularity checking problems for visibly pushdown automata...

  9. Earth mortars and earth-lime renders

    Directory of Open Access Journals (Sweden)

    Maria Fernandes

    2008-01-01

    Full Text Available Earth surface coatings play a decorative architectural role, apart from their function as wall protection. In Portuguese vernacular architecture, earth mortars were usually applied on stone masonry, while earth renders and plasters were used on indoors surface coatings. Limestone exists only in certain areas of the country and consequently lime was not easily available everywhere, especially on granite and schist regions where stone masonry was a current building technique. In the central west coast of Portugal, the lime slaking procedure entailed slaking the quicklime mixed with earth (sandy soil, in a pit; the resulting mixture would then be combined in a mortar or plaster. This was also the procedure for manufactured adobes stabilized with lime. Adobe buildings with earth-lime renderings and plasters were also traditional in the same region, using lime putty and lime wash for final coat and decoration. Classic decoration on earth architecture from the 18th-19th century was in many countries a consequence of the François Cointeraux (1740-1830 manuals - Les Cahiers d'Architecture Rurale" (1793 - a French guide for earth architecture and building construction. This manual arrived to Portugal in the beginning of XIX century, but was never translated to Portuguese. References about decoration for earth houses were explained on this manual, as well as procedures about earth-lime renders and ornamentation of earth walls; in fact, these procedures are exactly the same as the ones used in adobe buildings in this Portuguese region. The specific purpose of the present paper is to show some cases of earth mortars, renders and plasters on stone buildings in Portugal and to explain the methods of producing earth-lime renders, and also to show some examples of rendering and coating with earth-lime in Portuguese adobe vernacular architecture.

  10. Near Earth Objects

    DEFF Research Database (Denmark)

    Wolff, Stefan

    2006-01-01

    , Near Earth Objects: Asteroids and comets following paths that bring them near the Earth. NEOs have collided with the Earth since its formation, some causing local devastation, some causing global climate changes, yet the threat from a collision with a near Earth object has only recently been recognised...

  11. Remote Sensing the Phytoplankton Seasonal Succession of the Red Sea

    KAUST Repository

    Raitsos, Dionysios E.

    2013-06-05

    The Red Sea holds one of the most diverse marine ecosystems, primarily due to coral reefs. However, knowledge on large-scale phytoplankton dynamics is limited. Analysis of a 10-year high resolution Chlorophyll-a (Chl-a) dataset, along with remotely-sensed sea surface temperature and wind, provided a detailed description of the spatiotemporal seasonal succession of phytoplankton biomass in the Red Sea. Based on MODIS (Moderate-resolution Imaging Spectroradiometer) data, four distinct Red Sea provinces and seasons are suggested, covering the major patterns of surface phytoplankton production. The Red Sea Chl-a depicts a distinct seasonality with maximum concentrations seen during the winter time (attributed to vertical mixing in the north and wind-induced horizontal intrusion of nutrient-rich water in the south), and minimum concentrations during the summer (associated with strong seasonal stratification). The initiation of the seasonal succession occurs in autumn and lasts until early spring. However, weekly Chl-a seasonal succession data revealed that during the month of June, consistent anti-cyclonic eddies transfer nutrients and/or Chl-a to the open waters of the central Red Sea. This phenomenon occurs during the stratified nutrient depleted season, and thus could provide an important source of nutrients to the open waters. Remotely-sensed synoptic observations highlight that Chl-a does not increase regularly from north to south as previously thought. The Northern part of the Central Red Sea province appears to be the most oligotrophic area (opposed to southern and northern domains). This is likely due to the absence of strong mixing, which is apparent at the northern end of the Red Sea, and low nutrient intrusion in comparison with the southern end. Although the Red Sea is considered an oligotrophic sea, sporadic blooms occur that reach mesotrophic levels. The water temperature and the prevailing winds control the nutrient concentrations within the euphotic zone

  12. Evolving Phytoplankton Stoichiometry Fueled Diversification of the Marine Biosphere

    Directory of Open Access Journals (Sweden)

    Antonietta Quigg

    2012-05-01

    Full Text Available The availability of nutrients and the quantity and quality of food at the base of food webs have largely been ignored in discussions of the Phanerozoic record of biodiversity. We examine the role of nutrient availability and phytoplankton stoichiometry (the relative proportions of inorganic nutrients to carbon in the diversification of the marine biosphere. Nutrient availability and phytoplankton stoichiometry played a critical role in the initial diversification of the marine biosphere during the Neoproterozoic. Initial biosphere expansion during this time resulted in the massive sequestration of nutrients into biomass which, along with the geologically slow input of nutrients from land, set the stage for severe nutrient limitation and relatively constant marine biodiversity during the rest of the Paleozoic. Given the slow nutrient inputs from land and low recycling rates, the growth of early-to-middle Paleozoic metazoans remained limited by their having to expend energy to first “burn off” (respire excess carbon in food before the associated nutrients could be utilized for growth and reproduction; the relative equilibrium in marine biodiversity during the Paleozoic therefore appears to be real. Limited nutrient availability and the consequent nutrient imbalance may have delayed the appearance of more advanced carnivores until the Permo-Carboniferous, when widespread orogeny, falling sea level, the spread of forests, greater weathering rates, enhanced ocean circulation, oxygenation, and upwelling all combined to increase nutrient availability. During the Meso-Cenozoic, rising oxygen levels, the continued nutrient input from land, and, especially, increasing rates of bioturbation, enhanced nutrient availability, increasing the nutrient content of phytoplankton that fueled the diversification of the Modern Fauna.

  13. Impacts of metal oxide nanoparticles on marine phytoplankton.

    Science.gov (United States)

    Miller, Robert J; Lenihan, Hunter S; Muller, Erik B; Tseng, Nancy; Hanna, Shannon K; Keller, Arturo A

    2010-10-01

    Information on the toxicity of environmentally relevant concentrations of nanoparticles in marine ecosystems is needed for informed regulation of these emerging materials. We tested the effects of two types of metal oxide nanoparticles, TiO(2) and ZnO, on population growth rates of four species of marine phytoplankton representing three major coastal groups (diatoms, chlorophytes, and prymnesiophytes). These metal oxide nanoparticles (NPs) are becoming common components in many industrial, household, and cosmetic products that are released into coastal ecosystems. Titania NPs showed no measurable effect on growth rates of any species, while ZnO NPs significantly depressed growth rate of all four species. ZnO NPs aggregated rapidly in seawater, forming particles >400 nm hydrodynamic diameter within 30 min, and dissolved quickly, reaching equilibrium concentrations within 12 h. Toxicity of ZnO NPs to phytoplankton was likely due to dissolution, release, and uptake of free zinc ions, but specific nanoparticulate effects may be difficult to disentangle from effects due to free zinc ions. A modeling approach based on a Dynamic Energy Budget (DEB) framework was used to estimate sublethal effects of the two NPs on phytoplankton populations. Concentrations that were estimated to have no effect on population growth (NEC) were (one standard error in parentheses) 428 (58) μg L(-1) ZnO for the diatom Skeletonema marinoi and 223 (56) μg L(-1) for Thalassiosira pseudonana. NEC could not be estimated for the other taxa but were within the range of 500-1000 μg L(-1). Our results suggest that effects of metal oxide NPs on marine organisms is likely to vary with particle type and organism taxonomy.

  14. On the phytoplankton of Awba reservoir, Ibadan, Nigeria

    Directory of Open Access Journals (Sweden)

    G. A. Akin-Oriola

    2003-03-01

    Full Text Available The physico-chemical characteristics and phytoplankton of Awba reservoir in the University of Ibadan, Nigeria, were monitored to determine the impact of eutrophication on phytoplankton composition. The principal component analysis identified three major components influencing the physicochemistry of the water, namely trace metals, dissolved oxygen and ionic composition. Comparative analysis with a previous study showed a phenomenal increase in zinc, copper and iron levels over a 10-year period. Furthermore, the ferruginous nature of the soil contributed to the high levels of iron which exceeded the World Health Organization Standards for drinking water quality. The most abundant phytoplankton species was Microcystis aeruginosa which has been implicated in toxic blooms in freshwaters. The conditions favouring cyanophyte blooms and their implications are discussed.Las características físico-químicas y el fitoplancton de la represa Awba en la Universidad de Ibadan, Nigeria fueron monitoreadas para determinar el impacto de la eutroficación en la composición del fitoplancton. El análisis de componentes principales identificó tres denominados metales traza, oxígeno disuelto y composición iónica, como los mayores componentes que influencian la físico-química del agua. El análisis comparativo con un estudio previo mostró un fenómeno de incremento en los niveles de zinc, cobre e hierro en un periodo de 10 años. Además, la naturaleza ferruginosa del suelo contribuyó a los altos niveles de hierro que exceden los estándares de la Organización Mundial de la Salud para agua potable. La especie más abundante de fitoplancton fue Microcystis aeruginosa la que ha sido implicada en floraciones tóxicas en agua dulce. Se discuten las condiciones que favorecen el crecimiento de cianófitas y sus implicaciones.

  15. Cellular partitioning of nanoparticulate versus dissolved metals in marine phytoplankton.

    Science.gov (United States)

    Bielmyer-Fraser, Gretchen K; Jarvis, Tayler A; Lenihan, Hunter S; Miller, Robert J

    2014-11-18

    Discharges of metal oxide nanoparticles into aquatic environments are increasing with their use in society, thereby increasing exposure risk for aquatic organisms. Separating the impacts of nanoparticle from dissolved metal pollution is critical for assessing the environmental risks of the rapidly growing nanomaterial industry, especially in terms of ecosystem effects. Metal oxides negatively affect several species of marine phytoplankton, which are responsible for most marine primary production. Whether such toxicity is generally due to nanoparticles or exposure to dissolved metals liberated from particles is uncertain. The type and severity of toxicity depends in part on whether phytoplankton cells take up and accumulate primarily nanoparticles or dissolved metal ions. We compared the responses of the marine diatom, Thalassiosira weissflogii, exposed to ZnO, AgO, and CuO nanoparticles with the responses of T. weissflogii cells exposed to the dissolved metals ZnCl2, AgNO3, and CuCl2 for 7 d. Cellular metal accumulation, metal distribution, and algal population growth were measured to elucidate differences in exposure to the different forms of metal. Concentration-dependent metal accumulation and reduced population growth were observed in T. weissflogii exposed to nanometal oxides, as well as dissolved metals. Significant effects on population growth were observed at the lowest concentrations tested for all metals, with similar toxicity for both dissolved and nanoparticulate metals. Cellular metal distribution, however, markedly differed between T. weissflogii exposed to nanometal oxides versus those exposed to dissolved metals. Metal concentrations were highest in the algal cell wall when cells were exposed to metal oxide nanoparticles, whereas algae exposed to dissolved metals had higher proportions of metal in the organelle and endoplasmic reticulum fractions. These results have implications for marine plankton communities as well as higher trophic levels, since

  16. Nutrient and phytoplankton analysis of a Mediterranean coastal area.

    Science.gov (United States)

    Sebastiá, M T; Rodilla, M

    2013-01-01

    Identifying and quantifying the key anthropogenic nutrient input sources are essential to adopting management measures that can target input for maximum effect in controlling the phytoplankton biomass. In this study, three systems characterized by distinctive main nutrient sources were sampled along a Mediterranean coast transect. These sources were groundwater discharge in the Ahuir area, the Serpis river discharge in the Venecia area, and a submarine wastewater outfall 1,900 m from the coast. The study area includes factors considered important in determining a coastal area as a sensitive area: it has significant nutrient sources, tourism is a major source of income in the region, and it includes an area of high water residence time (Venecia area) which is affected by the harbor facilities and by wastewater discharges. We found that in the Ahuir and the submarine wastewater outfall areas, the effects of freshwater inputs were reduced because of a greater water exchange with the oligotrophic Mediterranean waters. On the other hand, in the Venecia area, the highest levels of nutrient concentration and phytoplankton biomass were attributed to the greatest water residence time. In this enclosed area, harmful dinoflagellates were detected (Alexandrium sp. and Dinophysis caudata). If the planned enlargement of the Gandia Harbor proceeds, it may increase the vulnerability of this system and provide the proper conditions of confinement for the dinoflagellate blooms' development. Management measures should first target phosphorus inputs as this is the most potential-limiting nutrient in the Venecia area and comes from a point source that is easier to control. Finally, we recommend that harbor environmental management plans include regular monitoring of water quality in adjacent waters to identify adverse phytoplankton community changes.

  17. Nutrient and Phytoplankton Analysis of a Mediterranean Coastal Area

    Science.gov (United States)

    Sebastiá, M. T.; Rodilla, M.

    2013-01-01

    Identifying and quantifying the key anthropogenic nutrient input sources are essential to adopting management measures that can target input for maximum effect in controlling the phytoplankton biomass. In this study, three systems characterized by distinctive main nutrient sources were sampled along a Mediterranean coast transect. These sources were groundwater discharge in the Ahuir area, the Serpis river discharge in the Venecia area, and a submarine wastewater outfall 1,900 m from the coast. The study area includes factors considered important in determining a coastal area as a sensitive area: it has significant nutrient sources, tourism is a major source of income in the region, and it includes an area of high water residence time (Venecia area) which is affected by the harbor facilities and by wastewater discharges. We found that in the Ahuir and the submarine wastewater outfall areas, the effects of freshwater inputs were reduced because of a greater water exchange with the oligotrophic Mediterranean waters. On the other hand, in the Venecia area, the highest levels of nutrient concentration and phytoplankton biomass were attributed to the greatest water residence time. In this enclosed area, harmful dinoflagellates were detected ( Alexandrium sp. and Dinophysis caudata). If the planned enlargement of the Gandia Harbor proceeds, it may increase the vulnerability of this system and provide the proper conditions of confinement for the dinoflagellate blooms' development. Management measures should first target phosphorus inputs as this is the most potential-limiting nutrient in the Venecia area and comes from a point source that is easier to control. Finally, we recommend that harbor environmental management plans include regular monitoring of water quality in adjacent waters to identify adverse phytoplankton community changes.

  18. Studies on the phytoplankton of the deep subalpine Lake Iseo

    Directory of Open Access Journals (Sweden)

    Rosario MOSELLO

    2003-08-01

    Full Text Available This paper reports the results of investigations carried out on the chemical characteristics and phytoplankton community of Lake Iseo. Samplings were performed on a monthly basis from 1998 to 2000. At least three main algal groups dominated the community throughout the study period. The large Bacillariophyceae were dominant mainly during late winter and early spring (Aulacoseira spp., Melosira varians, Asterionella formosa, with few species able to maintain occasional positive growth also during mid summer and/or autumn (Fragilaria crotonensis and Diatoma elongatum. The thermal stability of the water column and silica depletion were the main factors responsible for the decline of the large spring diatoms. The subsequent growth of Mougeotia sp. (Conjugatophyceae was favoured by its lower sinking rate and resistance to increasing grazing pressure by the dominant copepods (Copidodiaptomus steueri and cladocerans (Daphnia hyalina × galeata. Among the cyanobacteria, the greater development of Planktothrix rubescens in the autumn months, with conditions of vertical homogenisation and decreasing Zeu/Zmix ratios, was favoured by its ability to survive at low light irradiances. The temporal replacement of these three groups constitutes the main sequence of the annual phytoplankton succession in Lake Iseo. A large development of other algal groups was recorded only in one or two of the three study years (e.g. Dinophyceae and Chlorococcales. The changes observed in the annual phytoplankton development are discussed in the light of differences in the spring fertilisation of the waters, caused by differences in the depth of the layer involved in the late winter and spring vertical mixing.

  19. Phytoplankton virus production negatively affected by iron limitation

    Directory of Open Access Journals (Sweden)

    Hans A Slagter

    2016-08-01

    Full Text Available Fe-limited monocultures of the ubiquitous algae Micromonas pusilla and Phaeocystis globosa were infected with their respective viruses (MpV and PgV to ascertain the effect of Fe-limitation on phytoplankton host-virus dynamics. The effect of the viral shunt on Fe concentrations and bioavailability is starting to gain attention, since not only is Fe released through lysis, but also its solubility is increased by the simultaneous release of Fe-binding dissolved organic ligands. However, the effect of Fe-limitation on the process of viral lysis itself is poorly understood. In this study fine adjustment of a seawater-based culture medium including the use of ultra-clean trace metal conditions and protocols allowed for Fe-limited growth at nanomolar amounts as opposed to micromolar amounts typically employed in culturing. Viral lysates derived from Fe-limited and Fe-replete (for comparison hosts were cross-inoculated in hosts of both Fe treatments, to judge the quality of the resulting lysate as well as the effect of Fe introduction after initial infection. For both phytoplankton host-virus systems, the virus burst size reduced strongly under Fe stress, i.e. on average 28 ±1% of replete. Moreover, the MpV virus progeny showed highly reduced infectivity of 30±7%, whereas PgV infectivity was not affected. A small addition of Fe to Fe-limited cultures coming from the Fe-replete lysate counteracted the negative effect of Fe-limitation on phytoplankton virus production to some extent (but still half of replete, implying that the physiological history of the host at the moment of infection was an important underlying factor. These results indicate that Fe-limitation has the strong potential to reduce the loss of phytoplankton due to virus infection, thereby affecting the extent of Fe-cycling through the viral shunt. To what extent this affects the contribution of viral lysis-induced organic ligand release needs further study.

  20. Phytoplankton of the North Sea and its dynamics: A review

    Science.gov (United States)

    Reid, P. C.; Lancelot, C.; Gieskes, W. W. C.; Hagmeier, E.; Weichart, G.

    Phytoplankton is the major contributor to algal biomass and primary production of the North Sea, although crops of macroalgae can locally be up to 2000 g C.m -2 along the coast of the U.K. and Norway, and microphytobenthos dominates production in the shallow tidal flat areas bordering the coasts of England, the Netherlands, Germany and Denmark. Data collected since 1932 during the Continuous Plankton Recorder Survey show consistent patterns of geographical, seasonal and annual variation in the distribution of phytoplankton and its major taxonomic components. There is a trend of increased colouration in Recorder silks in the southern North Sea until approximately 1975 since when Colour levels (assumed to be indicative of algal biomass) have declined. In the eutrophic Dutch Wadden Sea the algal crop continued to increase; in Dutch coastal North Sea waters a trend of biomass increase reversed since 1984, apparently due to a reduction in Rhine river outflow. Long-term observations made at Helgoland since the 60's also show trends of increasing nutrients and phytoplankton biomass only to 1984. Adverse effects such as deoxygenation, foam formation and toxin production have been linked to mass concentrations of algae known as blooms. There is no evidence from existing reports for an increase in their frequency, although some years stand out with larger numbers. Occurrence of blooms can partly be explained by hydrographic conditions. More than 30 taxa are recognised as occurring in bloom proportions in the North Sea, approximately one third of which can be toxic. The crop of Bacillariophyceae (diatoms) is not likely to increase with eutrophication due to silicate limitation. An extensive subsurface maximum of armoured dinoflagellates, its abundance gouverned by hydrographic conditions, is the most characteristic feature of the central and northern North Sea in the summer months. Abundance, sometimes dominance, of picoplankton and of species that are not readily detected by

  1. Large yearly production of phytoplankton in the Western bering strait.

    Science.gov (United States)

    Sambrotto, R N; Goering, J J; McRoy, C P

    1984-09-14

    Production in the western Bering Strait is estimated at 324 grams of carbon per square meter per year over 2.12x 10(4) square kilometers. An ice-reduced growing season makes this large amount of primary production unexpected, but it is consistent with the area's large upper trophic level stocks. The productivity is fueled by a cross-shelf flow of nutrient-rich water from the Bering Sea continental slope. This phytoplankton production system from June through September is analogous to a laboratory continuous culture.

  2. Visibility and invisibility in chronic illness

    NARCIS (Netherlands)

    Hoppe, S.

    2010-01-01

    Does the visibility of a condition necessarily lead to stigmatization? Is it easier to suffer from an invisible than a visible condition? And what are the consequences of living with an invisible or visible illness? In this article the author draws on the concepts of stigma and concealability to

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

    NARCIS (Netherlands)

    Mojica, K.D.A.; Huisman, J.; Wilhelm, S.W.; Brussaard, C.P.D.

    2016-01-01

    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

  4. UV damage to plant life in a photobiologically dynamic environment : The case of marine phytoplankton

    NARCIS (Netherlands)

    Gieskes, W.W C; Buma, A.G.J.

    1997-01-01

    The effect of UV-B radiation on growth of marine phytoplankton was investigated in relation to DNA damage induced by a range of biologically effective doses (BEDs). Emiliania huxleyi (Prymnesiophyceae) was chosen as a model organism of the ocean's phytoplankton because of its importance in global

  5. A prospective study of marine phytoplankton and reported illness among recreational beachgoers in Puerto Rico, 2009

    Science.gov (United States)

    BACKGROUND: Blooms of marine phytoplankton may adversely affect human health. The potential public health impact of low-level exposures is not well established, and few prospective cohort studies of recreational exposures to marine phytoplankton have been conducted.OBJECTIVE: We ...

  6. Phytoplankton dynamics in contrasting early stage North Atlantic spring blooms: composition, succession, and potential drivers

    DEFF Research Database (Denmark)

    Daniels, C.J.; Poulton, A. J.; Esposito, M.

    2015-01-01

    by a lack of in situ observations of the phytoplankton community composition and its evolution during this critical period. We investigated the dynamics of the phytoplankton community structure at two contrasting sites in the Iceland and Norwegian Basins during the early stage (25 March–25 April...

  7. A FIVE YEAR RECORD OF PHYTOPLANKTON PIGMENT PATTERNS IN ESCAMBIA/PENSACOLA BAY, FL

    Science.gov (United States)

    Phytoplankton pigments were monitored quarterly at over 50 stations in Escambia/Pensacola Bay System (Pensacola, FL) from spring of 1996 to fall 2000. HPLC accessory pigments were used to analyze the phytoplankton community structure. HPLC data suggest a dominance of blue-green a...

  8. UV-induced changes in phytoplankton cells and its effects on grazers

    NARCIS (Netherlands)

    Hessen, D.O.; DeLange, H.J.; Van Donk, E.

    1997-01-01

    This review addresses the effects of UV-radiation on the morphology and biochemistry of phytoplankton and the potential effects on grazers. UVA and UVB radiation inhibit the uptake of inorganic nutrients in phytoplankton. Reduced rates of ammonium and nitrate uptake in marine diatoms, and reduced

  9. Contaminated sediment resuspension induces shifts in phytoplankton structure and function in a eutrophic Mediterranean lagoon

    OpenAIRE

    Lafabrie C.; Hlaili A.S.; Leboulanger C.; Tarhouni I.; Othman H.B.; Mzoughi N.; Chouba L.; Pringault O.

    2013-01-01

    The combined effects of contaminants and nutrients released from sediment into the water column during resuspension-mixing events were assessed on the phytoplankton composition and productivity in the anthropized lagoon of Bizerte (Tunisia, Mediterranean Sea). During a 4-day experiment, phytoplankton was exposed in in situ immersed microcosms to sediment elutriates (untreated: El and sterilized: S-El), prepared from a sediment r...

  10. Spatial distribution of phytoplankton in the Gulf of Riga during spring and summer stages

    Science.gov (United States)

    Seppälä, J.; Balode, M.

    1999-12-01

    Distribution patterns of chlorophyll a, phytoplankton species and biomass were studied in the Gulf of Riga, one of the most eutrophicated areas of the Baltic Sea. Quasi-synoptic measurements were carried out during four seasonal stages (spring bloom 1995, early-summer stage 1994, cyanobacterial bloom 1994, and late summer stage 1993). For each stage, common factor analysis was used to simplify the highly correlated patterns of nutrients, salinity, temperature and the depth of mixed layer. Obtained latent variables were used to explain spatial distribution of phytoplankton. Generally, the distribution of phytoplankton variables followed closely the patterns of nutrient rich fresh water. During the spring bloom in 1995, the spatial structures of phytoplankton biomass (4-27 mg l -1) and chlorophyll a (13-50 μg l -1) were well explained ( r=0.68 and 0.69, respectively, pcryptomonads (on the average 50% of total biomass). At that stage the distribution of phytoplankton was obviously governed by biological interactions and the multivariate methods were not especially successful to explain the spatial distribution of the main components of phytoplankton community. Excluding the late summer phase, the statistical methods used in this study revealed well the relationships between phytoplankton variables and nutrient rich fresh water. It is evident that nutrient load from the River Daugava is a reason for higher phytoplankton biomass in the southern Gulf of Riga, especially during bloom occasions.

  11. Short-term photoacclimation effects on photoinhibition of phytoplankton in the Drake Passage (Southern Ocean)

    NARCIS (Netherlands)

    Alderkamp, A.C.; Garcon, V.; de Baar, H.J.W.; Arrigo, K.R.

    2011-01-01

    We assessed whether short-term photoacclimation responses of natural phytoplankton populations in the Drake Passage (Southern Ocean) were affecting protection from photodamage as cells are mixed up to the surface from depth. To this end, we measured phytoplankton fluorescence characteristics and

  12. PHYTOPLANKTON AND ZOOPLANKTON SEASONAL DYNAMICS IN A SUBTROPICAL ESTUARY: IMPORTANCE OF CYANOBACTERIA

    Science.gov (United States)

    Murrell, Michael C. and Emile M. Lores. 2004. Phytoplankton and Zooplankton Seasonal Dynamics in a Subtropical Estuary: Importance of Cyanobacteria. J. Plankton Res. 26(3):371-382. (ERL,GB 1190). A seasonal study of phytoplankton and zooplankton was conducted from 1999-20...

  13. Phytoplankton absorption and pigment adaptation of a red tide in the ...

    African Journals Online (AJOL)

    Phytoplankton absorption and pigment characteristics of a red tide were investigated in coastal waters of the southern Benguela. Diagnostic indices indicated that dinoflagellates were the dominant phytoplankton group, with diatoms and small flagellates being of secondary importance. Very high biomass was observed ...

  14. Variation of phytoplankton community structure from the Pearl River estuary to South China Sea.

    Science.gov (United States)

    Jiang, Zhao-Yu; Wang, You-Shao; Cheng, Hao; Sun, Cui-Ci; Wu, Mei-Lin

    2015-10-01

    The Pearl River is located in the northern part of South China Sea. The environment of the Pearl River estuary (PRE) is significantly impacted by nutrients from anthropogenic activities. Along the anthropogenic pollution gradient from the PRE to South China Sea, the phylogenetic diversity and biomass of phytoplankton was examined in relation to physic-chemical variables. The richness of rbcL gene was higher in the open sea than the estuary, while the concentration of chlorophyll a (Chl a) was higher in the estuary than in the open sea. The cluster analysis of the sequences data resulted in seven phytoplankton community types and the dominant species of phytoplankton changed from Cryptophytes and Diatoms to Prymnesiophytes and Diatoms along the gradient. The community structure of phytoplankton was shaped by nutrients and salinity. The phytoplankton biomass was significantly positively affected by phosphorus, nitrite and ammonium (P phytoplankton diversity was highly positively affected by salinity (P phytoplankton distribution and biomass of the study area. Further research is necessary to reveal the influence mechanism of environmental factors on the phytoplankton.

  15. Allelopathic effect of the aquatic macrophyte, Stratiotes aloides, on natural phytoplankton

    NARCIS (Netherlands)

    Mulderij, G.; Mau, B.; Smolders, A.J.P.; Van Donk, E.

    2006-01-01

    A survey of different Dutch Stratiotes stands showed that the density of phytoplankton (except cyanobacteria) was always higher outside S. aloides than between the rosettes of S. aloides. Analyses of water samples revealed that nutrient limitation was unlikely to have caused the lower phytoplankton

  16. Phytoplankton dynamics of a tropical river: A dry and rainy season ...

    African Journals Online (AJOL)

    A study was carried out in River Ethiope in the Niger Delta area ofNigeria, to assess the influence of seasonal dynamics on the phytoplankton composition, density and diversity. Samples were collected in the dry and rainy season. Qualitative phytoplankton samples were collected by towing 55 ìm mesh plankton net while ...

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

    NARCIS (Netherlands)

    Zagaris, Antonios; Doelman, A.

    2011-01-01

    Co-limitation of marine phytoplankton growth by light and nutrient, both of which are essential for phytoplankton, leads to complex dynamic behaviour 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

  18. The influence of plant-associated filter feeders on phytoplankton biomass: a mesocosm study

    NARCIS (Netherlands)

    Vanderstukken, M.; Declerck, S.A.J.; Pals, A.; De Meester, L.; Muylaert, K.

    2010-01-01

    Low phytoplankton biomass usually occurs in the presence of submerged macrophytes, possibly because submerged macrophytes enhance top-down control of phytoplankton by offering a refuge for efficient grazers like Daphnia against fish predation. However, other field studies also suggest that submerged

  19. Silicate availability, vertical mixing and grazing control of phytoplankton blooms in mesocosms

    NARCIS (Netherlands)

    Escaravage, V.L.; Prins, T.C.

    2002-01-01

    The present paper explores (i) the way silicate concentrations may control the switch from diatom to non-diatom dominated phytoplankton, (ii) the consequence of mixing intensity and nutrient loading on phytoplankton composition (and potentially harmful species), (iii) to what extent trophic

  20. A Comparison of Three Approaches to Predict Phytoplankton Biomass in Gonghu Bay of Lake Taihu

    NARCIS (Netherlands)

    Huang, J.C.; Gao, J.F.; Mooij, W.M.

    2014-01-01

    Algal blooms have caused severe problems in Lake Taihu, China. Early warning of phytoplankton accumulation can support decision-making against harmful algal bloom events. To investigate the performance of different models in forecasting high phytoplankton biomass, we developed a mechanistic, a

  1. Spectroscopy and Device Performance of Rare Earth Doped III-Nitrides

    National Research Council Canada - National Science Library

    Hommerich, Uwe

    2002-01-01

    The recent demonstration of visible thin-film electroluminescence (TFEL) devices based on rare earth doped GaN has spurred great interest in this class of materials for possible applications in full color displays...

  2. Visible spectrum of stable sonoluminescence

    Science.gov (United States)

    Carlson, Joseph T.

    1992-12-01

    Synchronous emissions of picosecond pulses of light are observed to originate from a bubble trapped at the pressure antinode of a resonant sound field. The spectrum has been measured using a single slit spectrometer equipped with a linear array CCD detector. Spectra from differing solutions of water and glycerin are compared to the visible blackbody spectrum distribution. Assuming a blackbody model, apparent temperatures of 18,900 Kelvins are observed in pure water. Increasing glycerin concentration appears to correlate with cooler blackbody temperatures. The spectrum is also found to continually change with time, independent of input parameters.

  3. Book Review: Making Thinking Visible

    OpenAIRE

    Kenneth Royal; Lizette Hardie

    2015-01-01

    Recent trends in medical education emphasize the importance of producing well-rounded graduates who not only possess a sufficient fund of medical knowledge but who can think clearly and deeply. Unfortunately, many medical educators struggle with what exactly it means to “think” and do not know where to begin when asked to teach “thinking.” We believe the book Making Thinking Visible, though written for K-12, will be of great interest to medical educators. The book describes different types of...

  4. Book Review: Making Thinking Visible

    Directory of Open Access Journals (Sweden)

    Kenneth Royal

    2015-12-01

    Full Text Available Recent trends in medical education emphasize the importance of producing well-rounded graduates who not only possess a sufficient fund of medical knowledge but who can think clearly and deeply. Unfortunately, many medical educators struggle with what exactly it means to “think” and do not know where to begin when asked to teach “thinking.” We believe the book Making Thinking Visible, though written for K-12, will be of great interest to medical educators. The book describes different types of thinking and presents more than 20 teaching routines that can help engage learners and improve learning to think.

  5. Book Review: Making Thinking Visible

    Science.gov (United States)

    Royal, Kenneth; Hardie, Lizette

    2015-01-01

    Recent trends in medical education emphasize the importance of producing well-rounded graduates who not only possess a sufficient fund of medical knowledge but who can think clearly and deeply. Unfortunately, many medical educators struggle with what exactly it means to “think” and do not know where to begin when asked to teach “thinking.” We believe the book Making Thinking Visible, though written for K-12, will be of great interest to medical educators. The book describes different types of thinking and presents more than 20 teaching routines that can help engage learners and improve learning to think.

  6. Dynamical analysis of a toxin-producing phytoplankton-zooplankton model with refuge.

    Science.gov (United States)

    Li, Juan; Song, Yongzhong; Wan, Hui

    2017-04-01

    To study the impacts of toxin produced by phytoplankton and refuges provided for phytoplankton on phytoplankton-zooplankton interactions in lakes, we establish a simple phytoplankton-zooplankton system with Holling type II response function. The existence and stability of positive equilibria are discussed. Bifurcation analyses are given by using normal form theory which reveals reasonably the mechanisms and nonlinear dynamics of the effects of toxin and refuges, including Hopf bifurcation, Bogdanov-Takens bifurcation of co-dimension 2 and 3. Numerical simulations are carried out to intuitively support our analytical results and help to explain the observed biological behaviors. Our findings finally show that both phytoplankton refuge and toxin have a significant impact on the occurring and terminating of algal blooms in freshwater lakes.

  7. 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 functional...

  8. Diversity of Phytoplankton of a sub-tropical reservoir of Mizoram, northeast India

    Directory of Open Access Journals (Sweden)

    Bhushan Kumar Sharma

    2016-12-01

    Full Text Available Phytoplankton of Khawiva reservoir of Mizoram, northeast India (NEI revealed a total of 55 species; nearly concurrent mean monthly richness and high community similarities (vide Sørensen index during two years affirmed homogeneity in its species composition. Phytoplankton comprised dominant component (61.1±14.3% of net plankton and recorded wider density variations. Chlorophyta influenced phytoplankton abundance with quantitative importance of Staurastrum spp. >Xanthidium spp. >Cosmarium spp. in particular. Bacillariophyta formed subdominant group; Cryptophyta and Cyanophyta showed limited importance; and Euglenophyta and Dinophyta recorded poor densities. Phytoplankton is characterized by moderate species diversity, high evenness and low dominance but with wide variations. Richness, abundance and species diversity followed no definite patterns of monthly variations during two years. Insignificant influence of individual abiotic factors on phytoplankton assemblages coupled with low cumulative influence of fifteen abiotic parameters (vide CCA yielded little insight on overall role of abiotic parameters.

  9. Moon-based visibility analysis for the observation of “The Belt and Road”

    Science.gov (United States)

    REN, Yuanzhen; GUO, Huadong; LIU, Guang; YE, Hanlin; DING, Yixing; RUAN, Zhixing; LV, Mingyang

    2016-11-01

    Aiming at promoting the economic prosperity and regional economic cooperation, the “Silk Road Economic Belt” and the “21st Century Maritime Silk Road” (hereinafter referred to as the Belt and Road) was raised. To get a better understanding of “the Belt and Road” whole region, considering the large-scale characteristic, the Moon platform is a good choice. In this paper, the ephemeris is taken as data source and the positions and attitudes of Sun, Earth and Moon are obtained based on the reference systems transformation. Then we construct a simplified observation model and calculate the spatial and angular visibility of the Moon platform for “the Belt and Road” region. It turns out that Moon-based observation of this region shows a good performance of spatial visibility and variable angular visibility, indicating the Moon being a new potential platform for large-scale Earth observation.

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

    Science.gov (United States)

    Galloway, Aaron W E; Winder, Monika

    2015-01-01

    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 diatoms

  11. Decadal phytoplankton dynamics in response to episodic climatic disturbances in a subtropical deep freshwater ecosystem.

    Science.gov (United States)

    Ko, Chia-Ying; Lai, Chao-Chen; Hsu, Huang-Hsiung; Shiah, Fuh-Kwo

    2017-02-01

    Information of the decadal timescale effects of episodic climatic disturbances (i.e., typhoons) on phytoplankton in freshwater ecosystems have received less attention and fewer seasonal evaluations partly due to the lack of long-term time-series monitoring data in typhoon prevailing areas. Through field observations of a total 36 typhoon cases in a subtropical deep freshwater ecosystem in the period of 2005-2014, we quantified phytoplankton biomass, production and growth rate in response to meteorological and hydrological changes in the weeks before, during and after typhoons between summer and autumn, and also investigated the effects of typhoon characteristics on the aforementioned phytoplankton responses. The results showed that phytoplankton exposed to typhoon disturbances generally exhibited an increasing trend over the weeks before, during and after typhoons in summer but varied in autumn. The correlations and multivariate regressions showed different contributions of meteorological and hydrological variables to individual phytoplankton responses before, during and after typhoons between seasons. The post-typhoon weeks (i.e., within two weeks after a typhoon had passed) were especially important for the timeline of phytoplankton increases and with a detectable seasonal variation that the chlorophyll a concentration significantly increased in autumn whereas both primary production and growth rate were associated with significant changes in summer. Additionally, phytoplankton responses during the post-typhoon weeks were significantly different between discrete or continuous types of typhoon events. Our work illustrated the fact that typhoons did influence phytoplankton responses in the subtropical deep freshwater ecosystem and typhoon passages in summer and autumn affected the phytoplankton dynamics differently. Nevertheless, sustained and systematic monitoring in order to advance our understanding of the role of typhoons between seasons in the modulation of

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

    Science.gov (United States)

    Galloway, Aaron W. E.; Winder, Monika

    2015-01-01

    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 diatoms

  13. Predator-induced fleeing behaviors in phytoplankton: a new mechanism for harmful algal bloom formation?

    Directory of Open Access Journals (Sweden)

    Elizabeth L Harvey

    Full Text Available In the plankton, heterotrophic microbes encounter and ingest phytoplankton prey, which effectively removes >50% of daily phytoplankton production in the ocean and influences global primary production and biochemical cycling rates. Factors such as size, shape, nutritional value, and presence of chemical deterrents are known to affect predation pressure. Effects of movement behaviors of either predator or prey on predation pressure, and particularly fleeing behaviors in phytoplankton are thus far unknown. Here, we quantified individual 3D movements, population distributions, and survival rates of the toxic phytoplankton species, Heterosigma akashiwo in response to a ciliate predator and predator-derived cues. We observed predator-induced defense behaviors previously unknown for phytoplankton. Modulation of individual phytoplankton movements during and after predator exposure resulted in an effective separation of predator and prey species. The strongest avoidance behaviors were observed when H. akashiwo co-occurred with an actively grazing predator. Predator-induced changes in phytoplankton movements resulted in a reduction in encounter rate and a 3-fold increase in net algal population growth rate. A spatially explicit population model predicted rapid phytoplankton bloom formation only when fleeing behaviors were incorporated. These model predictions reflected field observations of rapid H. akashiwo harmful algal bloom (HAB formation in the coastal ocean. Our results document a novel behavior in phytoplankton that can significantly reduce predation pressure and suggests a new mechanism for HAB formation. Phytoplankton behaviors that minimize predatory losses, maximize resource acquisition, and alter community composition and distribution patterns could have major implications for our understanding and predictive capacity of marine primary production and biochemical cycling rates.

  14. Predator-induced fleeing behaviors in phytoplankton: a new mechanism for harmful algal bloom formation?

    Science.gov (United States)

    Harvey, Elizabeth L; Menden-Deuer, Susanne

    2012-01-01

    In the plankton, heterotrophic microbes encounter and ingest phytoplankton prey, which effectively removes >50% of daily phytoplankton production in the ocean and influences global primary production and biochemical cycling rates. Factors such as size, shape, nutritional value, and presence of chemical deterrents are known to affect predation pressure. Effects of movement behaviors of either predator or prey on predation pressure, and particularly fleeing behaviors in phytoplankton are thus far unknown. Here, we quantified individual 3D movements, population distributions, and survival rates of the toxic phytoplankton species, Heterosigma akashiwo in response to a ciliate predator and predator-derived cues. We observed predator-induced defense behaviors previously unknown for phytoplankton. Modulation of individual phytoplankton movements during and after predator exposure resulted in an effective separation of predator and prey species. The strongest avoidance behaviors were observed when H. akashiwo co-occurred with an actively grazing predator. Predator-induced changes in phytoplankton movements resulted in a reduction in encounter rate and a 3-fold increase in net algal population growth rate. A spatially explicit population model predicted rapid phytoplankton bloom formation only when fleeing behaviors were incorporated. These model predictions reflected field observations of rapid H. akashiwo harmful algal bloom (HAB) formation in the coastal ocean. Our results document a novel behavior in phytoplankton that can significantly reduce predation pressure and suggests a new mechanism for HAB formation. Phytoplankton behaviors that minimize predatory losses, maximize resource acquisition, and alter community composition and distribution patterns could have major implications for our understanding and predictive capacity of marine primary production and biochemical cycling rates.

  15. The Coverage Analysis for Low Earth Orbiting Satellites at Low Elevation

    OpenAIRE

    Shkelzen Cakaj; Bexhet Kamo; Algenti Lala; Alban Rakipi

    2014-01-01

    Low Earth Orbit (LEO) satellites are used for public networking and for scientific purposes. Communication via satellite begins when the satellite is positioned in its orbital position. Ground stations can communicate with LEO satellites only when the satellite is in their visibility region. The duration of the visibility and the communication vary for each LEO satellite pass over the station, since LEO satellites move too fast over the Earth. The satellite coverage area is defined as a regio...

  16. JPEG ringing artifact visibility evaluation

    Science.gov (United States)

    Hu, Sirui; Pizlo, Zygmunt; Allebach, Jan P.

    2014-01-01

    To achieve high perceptual quality of compressed images, many objective image quality metrics for compression artifacts evaluation and reduction have been developed based on characterization of local image features. However, it is the end user who is judging the image quality in various applications, so the validation of how well these metrics predict human perception is important and necessary. In this paper, we present a preliminary psychophysics experiment method to capture human perception of local ringing artifacts in JPEG images with different severity levels. Observers are asked to annotate the compressed image where they perceive artifacts along the edges, directly on the screen using an interactive tablet display. They are asked to catalog the severity of artifacts into one of the three levels: Strong, Medium, and Light. We process the hand-marked data into a ringing visibility edge map showing a ringing severity mean opinion score (MOS) at every edge pixel. The perceptual information captured in this experiment, enables us to study the correlation between human perception and local image features, which is an important step towards the goal of developing a non-reference (NR) objective metric to predict the visibility of JPEG ringing artifacts in alignment with the assessments of human observers.

  17. In situ measurements of phytoplankton fluorescence using low cost electronics.

    Science.gov (United States)

    Leeuw, Thomas; Boss, Emmanuel S; Wright, Dana L

    2013-06-19

    Chlorophyll a fluorometry has long been used as a method to study phytoplankton in the ocean. In situ fluorometry is used frequently in oceanography to provide depth-resolved estimates of phytoplankton biomass. However, the high price of commercially manufactured in situ fluorometers has made them unavailable to some individuals and institutions. Presented here is an investigation into building an in situ fluorometer using low cost electronics. The goal was to construct an easily reproducible in situ fluorometer from simple and widely available electronic components. The simplicity and modest cost of the sensor makes it valuable to students and professionals alike. Open source sharing of architecture and software will allow students to reconstruct and customize the sensor on a small budget. Research applications that require numerous in situ fluorometers or expendable fluorometers can also benefit from this study. The sensor costs US$150.00 and can be constructed with little to no previous experience. The sensor uses a blue LED to excite chlorophyll a and measures fluorescence using a silicon photodiode. The sensor is controlled by an Arduino microcontroller that also serves as a data logger.

  18. Generalized receptor law governs phototaxis in the phytoplankton Euglena gracilis.

    Science.gov (United States)

    Giometto, Andrea; Altermatt, Florian; Maritan, Amos; Stocker, Roman; Rinaldo, Andrea

    2015-06-02

    Phototaxis, the process through which motile organisms direct their swimming toward or away from light, is implicated in key ecological phenomena (including algal blooms and diel vertical migration) that shape the distribution, diversity, and productivity of phytoplankton and thus energy transfer to higher trophic levels in aquatic ecosystems. Phototaxis also finds important applications in biofuel reactors and microbiopropellers and is argued to serve as a benchmark for the study of biological invasions in heterogeneous environments owing to the ease of generating stochastic light fields. Despite its ecological and technological relevance, an experimentally tested, general theoretical model of phototaxis seems unavailable to date. Here, we present accurate measurements of the behavior of the alga Euglena gracilis when exposed to controlled light fields. Analysis of E. gracilis' phototactic accumulation dynamics over a broad range of light intensities proves that the classic Keller-Segel mathematical framework for taxis provides an accurate description of both positive and negative phototaxis only when phototactic sensitivity is modeled by a generalized "receptor law," a specific nonlinear response function to light intensity that drives algae toward beneficial light conditions and away from harmful ones. The proposed phototactic model captures the temporal dynamics of both cells' accumulation toward light sources and their dispersion upon light cessation. The model could thus be of use in integrating models of vertical phytoplankton migrations in marine and freshwater ecosystems, and in the design of bioreactors.

  19. Network of interactions between ciliates and phytoplankton during spring

    Directory of Open Access Journals (Sweden)

    Thomas ePosch

    2015-11-01

    Full Text Available The annually recurrent spring phytoplankton blooms in freshwater lakes initiate pronounced successions of planktonic ciliate species. Although there is considerable knowledge on the taxonomic diversity of these ciliates, their species-specific interactions with other microorganisms are still not well understood. Here we present the succession patterns of 20 morphotypes of ciliates during spring in Lake Zurich, Switzerland, and we relate their abundances to phytoplankton genera, flagellates, heterotrophic bacteria, and abiotic parameters. Interspecific relationships were analyzed by contemporaneous correlations and time-lagged co-occurrence and visualized as association networks. The contemporaneous network pointed to the pivotal role of distinct ciliate species (e.g., Balanion planctonicum, Rimostrombidium humile as primary consumers of cryptomonads, revealed a clear overclustering of mixotrophic / omnivorous species, and highlighted the role of Halteria / Pelagohalteria as important bacterivores. By contrast, time-lagged statistical approaches (like local similarity analyses, LSA proved to be inadequate for the evaluation of high-frequency sampling data. LSA led to a conspicuous inflation of significant associations, making it difficult to establish ecologically plausible interactions between ciliates and other microorganisms. Nevertheless, if adequate statistical procedures are selected, association networks can be powerful tools to formulate testable hypotheses about the autecology of only recently described ciliate species.

  20. Plastids of Marine Phytoplankton Produce Bioactive Pigments and Lipids

    Directory of Open Access Journals (Sweden)

    Benoît Schoefs

    2013-09-01

    Full Text Available Phytoplankton is acknowledged to be a very diverse source of bioactive molecules. These compounds play physiological roles that allow cells to deal with changes of the environmental constrains. For example, the diversity of light harvesting pigments allows efficient photosynthesis at different depths in the seawater column. Identically, lipid composition of cell membranes can vary according to environmental factors. This, together with the heterogenous evolutionary origin of taxa, makes the chemical diversity of phytoplankton compounds much larger than in terrestrial plants. This contribution is dedicated to pigments and lipids synthesized within or from plastids/photosynthetic membranes. It starts with a short review of cyanobacteria and microalgae phylogeny. Then the bioactivity of pigments and lipids (anti-oxidant, anti-inflammatory, anti-mutagenic, anti-cancer, anti-obesity, anti-allergic activities, and cardio- neuro-, hepato- and photoprotective effects, alone or in combination, is detailed. To increase the cellular production of bioactive compounds, specific culture conditions may be applied (e.g., high light intensity, nitrogen starvation. Regardless of the progress made in blue biotechnologies, the production of bioactive compounds is still limited. However, some examples of large scale production are given, and perspectives are suggested in the final section.

  1. Phytoplankton and nutrient dynamics in Winyah Bay, SC.

    Science.gov (United States)

    Boneillo, G. E.; Brooks, S. S.; Brown, S. L.; Woodford, K. M.; Wright, C. R.

    2016-02-01

    Winyah Bay is a coastal plain estuary located in South Carolina that has been classified for a moderate risk of Eutrophication by NOAA. Winyah Bay receives freshwater input from four rivers, the Waccamaw, Sampit, Black, and Pee Dee Rivers. The Waccamaw, Sampit and Black River are blackwater systems that discharge elevated amounts of colored dissolved organic matter. During the summer and fall of 2015, bioassay experiments were performed to simultaneously examine both light and nutrient (nitrogen & phosphate) limitation throughout Winyah Bay. Sampling stations near the mouth of the Waccamaw and Sampit Rivers showed that phytoplankton were light limited in the late summer instead of nutrient limited. These stations were located in the industrialized area of the bay and typically had the highest nutrient concentrations and highest turbidity, with Secchi depths typically less than 0.5 meters. Results indicated that phytoplankton may be nitrogen limited near the mouth of Winyah Bay, where nutrient concentrations and turbidity were observed to be lower than locations further upstream. There was also an observed dissolved oxygen and pH gradient during the summer of 2015. Dissolved oxygen levels less than 4.0 mg/L were routinely observed near the industrialized head of the estuary and corresponded with lower pH values.

  2. In situ Measurements of Phytoplankton Fluorescence Using Low Cost Electronics

    Directory of Open Access Journals (Sweden)

    Dana L. Wright

    2013-06-01

    Full Text Available Chlorophyll a fluorometry has long been used as a method to study phytoplankton in the ocean. In situ fluorometry is used frequently in oceanography to provide depth-resolved estimates of phytoplankton biomass. However, the high price of commercially manufactured in situ fluorometers has made them unavailable to some individuals and institutions. Presented here is an investigation into building an in situ fluorometer using low cost electronics. The goal was to construct an easily reproducible in situ fluorometer from simple and widely available electronic components. The simplicity and modest cost of the sensor makes it valuable to students and professionals alike. Open source sharing of architecture and software will allow students to reconstruct and customize the sensor on a small budget. Research applications that require numerous in situ fluorometers or expendable fluorometers can also benefit from this study. The sensor costs US$150.00 and can be constructed with little to no previous experience. The sensor uses a blue LED to excite chlorophyll a and measures fluorescence using a silicon photodiode. The sensor is controlled by an Arduino microcontroller that also serves as a data logger.

  3. Phytoplankton community of Reis lake in the Brazilian Amazon

    Directory of Open Access Journals (Sweden)

    ISE G. SILVA

    2013-06-01

    Full Text Available Reis Lake is located in the municipality of Caracaraí, state of Roraima (Brazil and is subject to fluctuations in water level. The aim of this study was to analyze the structure of the phytoplankton community on the nictemeral and seasonal scales and determined the influence of limnological variables. Sampling was performed in the rainy season (June/2006 and dry season (November/2006, considering two nictemeral cycles. The phytoplankton community was assessed with regard to composition and density, abiotic variables were analyzed simultaneously. The lake had low concentrations of oxygen, clinograde profile and water stratified during the day and homogenous at night, with low concentrations of nutrients and waters ranging from slightly acidic to alkaline. The phytoplankton was represented by 43 taxa, 35 species in the dry season and 29 species in the rainy season. Low densities of phytoplankton occurred in both nictemeral cycles, with accentuated vertical gradient. The highest densities were recorded in the dry season. Reis Lake exhibits characteristics that classify it as a polymythic and oligotrophic environment. The variability in the data was more important seasonally than on the nictemeral scale, supporting the hypothesis of the influence of the hydrological cycle on the dynamics of phytoplankton communities in floodplain lakes.O lago dos Reis está localizado no município de Caracaraí, no estado de Roraima (Brasil e está sujeito a flutuações no nível da água. O objetivo do estudo foi analisar a estrutura da comunidade fitoplanctônica nas escalas nictemeral e sazonal e determinar a influência de variáveis limnológicas nesta comunidade. As amostragens foram realizadas nos periodos chuvoso e seco, considerando dois ciclos nictemeral. A comunidade fitoplanctônica foi avaliada no que diz respeito à composição e densidade, simultaneamente, variáveis abióticas foram analisadas. O lago apresentou baixas concentrações de oxig

  4. Review: phytoplankton primary production in the world's estuarine-coastal ecosystems

    Science.gov (United States)

    Cloern, J. E.; Foster, S. Q.; Kleckner, A. E.

    2013-11-01

    between 30° N and 60° N; we found only 36 for sites south of 20° N. Second, of the 131 ecosystems where APPP has been reported, 37% are based on measurements at only one location during one year. The accuracy of these values is unknown but probably low, given the large inter-annual and spatial variability within ecosystems. Finally, global assessments are confounded by measurements that are not intercomparable because they were made with a broad range of methods. Phytoplankton primary production along the continental margins is tightly linked to variability of water quality, biogeochemical processes including ocean-atmosphere CO2 exchange, and production at higher trophic levels including species we harvest as food. The empirical record has deficiencies that preclude reliable global assessment of this key Earth-system process. We face two grand challenges to resolve these deficiencies: (1) organize and fund an international effort to use a common method and measure APPP regularly across a network of coastal sites that are globally representative and sustained over time, and (2) integrate data into a unifying model to explain the wide range of variability across ecosystems and to project responses of APPP to regional manifestations of global change as it continues to unfold.

  5. The Lifeworld Earth and a Modelled Earth

    Science.gov (United States)

    Juuti, Kalle

    2014-01-01

    The goal of this paper is to study the question of whether a phenomenological view of the Earth could be empirically endorsed. The phenomenological way of thinking considers the Earth as a material entity, but not as an object as viewed in science. In the learning science tradition, tracking the process of the conceptual change of the shape of the…

  6. Remote estimation of phytoplankton size fractions using the spectral shape of light absorption.

    Science.gov (United States)

    Wang, Shengqiang; Ishizaka, Joji; Hirawake, Toru; Watanabe, Yuji; Zhu, Yuanli; Hayashi, Masataka; Yoo, Sinjae

    2015-04-20

    Phytoplankton size structure plays an important role in ocean biogeochemical processes. The light absorption spectra of phytoplankton provide a great potential for retrieving phytoplankton size structure because of the strong dependence on the packaging effect caused by phytoplankton cell size and on different pigment compositions related to phytoplankton taxonomy. In this study, we investigated the variability in light absorption spectra of phytoplankton in relation to the size structure. Based on this, a new approach was proposed for estimating phytoplankton size fractions. Our approach use the spectral shape of the normalized phytoplankton absorption coefficient (a(ph)(λ)) through principal component analysis (PCA). Values of a(ph)(λ) were normalized to remove biomass effects, and PCA was conducted to separate the spectral variance of normalized a(ph)(λ) into uncorrelated principal components (PCs). Spectral variations captured by the first four PC modes were used to build relationships with phytoplankton size fractions. The results showed that PCA had powerful ability to capture spectral variations in normalized a(ph)(λ), which were significantly related to phytoplankton size fractions. For both hyperspectral a(ph)(λ) and multiband a(ph)(λ), our approach is applicable. We evaluated our approach using wide in situ data collected from coastal waters and the global ocean, and the results demonstrated a good and robust performance in estimating phytoplankton size fractions in various regions. The model performance was further evaluated by a(ph)(λ) derived from in situ remote sensing reflectance (R(rs)(λ)) with a quasi-analytical algorithm. Using R(rs)(λ) only at six bands, accurate estimations of phytoplankton size fractions were obtained, with R(2) values of 0.85, 0.61, and 0.76, and root mean-square errors of 0.130, 0.126, and 0.112 for micro-, nano-, and picophytoplankton, respectively. Our approach provides practical basis for remote estimation of

  7. Impacts of warming on phytoplankton abundance and phenology in a typical tropical marine ecosystem

    KAUST Repository

    Gittings, John

    2018-01-29

    In the tropics, thermal stratification (during warm conditions) may contribute to a shallowing of the mixed layer above the nutricline and a reduction in the transfer of nutrients to the surface lit-layer, ultimately limiting phytoplankton growth. Using remotely sensed observations and modelled datasets, we study such linkages in the northern Red Sea (NRS) - a typical tropical marine ecosystem. We assess the interannual variability (1998-2015) of both phytoplankton biomass and phenological indices (timing of bloom initiation, duration and termination) in relation to regional warming. We demonstrate that warmer conditions in the NRS are associated with substantially weaker winter phytoplankton blooms, which initiate later, terminate earlier and are shorter in their overall duration (~ 4 weeks). These alterations are directly linked with the strength of atmospheric forcing (air-sea heat fluxes) and vertical stratification (mixed layer depth [MLD]). The interannual variability of sea surface temperature (SST) is found to be a good indicator of phytoplankton abundance, but appears to be less important for predicting bloom timing. These findings suggest that future climate warming scenarios may have a two-fold impact on phytoplankton growth in tropical marine ecosystems: 1) a reduction in phytoplankton abundance and 2) alterations in the timing of seasonal phytoplankton blooms.

  8. [Yearly Changes of Phytoplankton Community in the Ecology-monitoring Area of Changli, Hebei in Summer].

    Science.gov (United States)

    Liang, Xiao-lin; Yang, Yang; Wang, Yu-liang; Zhang, Yue-ming; Zhao, Zhi-nan; Han, Xiao-qing; Zhang, Jian-da; Gao, Wei-ming

    2015-04-01

    Based on the investigation of phytoplankton and water body nutrient concentration in the ecology-monitoring area of Changli in summer from 2005 to 2013, the phytoplankton community structure was analyzed. The result showed that in recent 9 years, 3 phyla including 23 families, 39 genera and 105 species of phytoplankton were identified, in which 85.7% were diatoms and 13.3% were dinoflagellate. Only one species was found belonging to golden algae. There was great difference in dominant species among different years. According to the value of dominance, there were Coscinodiscus radiatus, Coscinodiscus debilis, Rhizosolenia styliformis, Cerataulina bergoni, Coscinodiscus wailesii, Thalassiosira sp., Ceratium tripos, Chaetoceros lorenzianus, Skeletonema costatum. The cell abundance was decreased yearly. The Shannon-Wiener index of phytoplankton community ranged from 0.015 to 3.889, and the evenness index ranged from 0.009 to 1, which showed little yearly change. And phytoplankton species were unevenly distributed among the 19 sites, there were relatively low amount of dominant species, but the dominance was relatively high. Canonical Correspondence Analysis (CCA) results of the phytoplankton community and its environmental factors showed that the environmental factors influencing the change of phytoplankton community structure in summer included water temperature, nutrients (TP, TN and NO3(-) -N, NH4(+)-N) and salinity, and the structural change was the result of the interactions of different environmental factors.

  9. [Community structure characteristics of phytoplankton and related affecting factors in Hengshan Reservoir, Zhejiang, China].

    Science.gov (United States)

    Yang, Liang-Jie; Yu, Peng-Fei; Zhu, Jun-Quan; Xu, Zhen; Lü, Guang-Han; Jin, Chun-Hua

    2014-02-01

    In order to reveal the community structure characteristics of phytoplankton and the relationships with environmental factors in Hengshan Reservoir, the phytoplankton species composition, abundance, biomass and 12 environmental factors at 4 sampling sites were analyzed from March 2011 to February 2012. A total of 246 phytoplankton species were identified, which belong to 78 genera and 7 phyla. The dominant species were Melosira varians, M. granulate, Cyclotella meneghiniana, Asterianella formosa, Synedra acus, Achnanthes exigua, Ankistrodesmus falcatus, Oscillatoria lacustris, Cryptomonas erosa, Chroomonas acuta, Phormidium tenue and Microcystis aeruginosa, etc. Seasonal variations of species were obvious. The annual abundance and biomass of the phytoplankton were 0.51 x 10(5)-14.22 x 10(5) ind x L(-1) and 0.07-1.27 mg x L(-1), respectively. The values of the Margelef index, Pielou index and Shannon index of the phytoplankton community were 1.10-3.33, 0.26-0.81 and 0.51-2.38, respectively. The phytoplankton community structure was of Bacillariophyta-Cryptophyta type in spring and winter, of Chlorophyta-Cyanophyta type in summer, and of Bacillariophyta type in autumn. Canonical correlation analysis (CCA) showed that temperature, transparency, chemical oxygen demand and pH had the closest relationships with the phytoplankton community structure in the reservoir. Water quality evaluation showed that Hengshan Reservoir was in a secondary pollution with a meso-trophic level.

  10. [Phytoplankton assemblages and their relation to environmental factors by multivariate statistic analysis in Bohai Bay].

    Science.gov (United States)

    Zhou, Ran; Peng, Shi-Tao; Qin, Xue-Bo; Shi, Hong-Hua; Ding, De-Wen

    2013-03-01

    A detailed field survey of hydrological, chemical and biological resources was conducted in the Bohai Bay in spring and summer 2007. The distributions of phytoplankton and their relations to environmental factors were investigated with multivariate analysis techniques. Totally 17 and 23 taxa were identified in spring and summer, respectively. The abundance of phytoplankton in spring was 115 x 10(4) cells x m(-3), which was significantly higher than that in summer (3.1 x 10(4) cells x m(-3)). Characteristics of phytoplankton assemblages in the two seasons were identified using principal component analysis (PCA), while redundancy analysis (RDA) was used to examine the environmental variables that may explain the patterns of variation of the phytoplankton community. Based on PCA results, in the spring, the phytoplankton was mainly distributed in the center and northern water zone, where the nitrate nitrogen concentration was higher. However, in summer, phytoplankton was found distributed in all zones of Bohai Bay, while the dominant species was mainly distributed in the estuary. RDA indicated that the key environmental factors that influenced phytoplankton assemblages in the spring were nitrate nitrogen (NO3(-) -N), nitrite nitrogen (NO2(-) -N) and soluble reactive phosphorus (SRP), while ammonium nitrogen (NH4(+) -N) and water temperature (WT) played key roles in summer.

  11. Nitrogen deposition and warming - effects on phytoplankton nutrient limitation in subarctic lakes.

    Science.gov (United States)

    Bergström, Ann-Kristin; Faithfull, Carolyn; Karlsson, Daniel; Karlsson, Jan

    2013-08-01

    The aim of this study was to predict the combined effects of enhanced nitrogen (N) deposition and warming on phytoplankton development in high latitude and mountain lakes. Consequently, we assessed, in a series of enclosure experiments, how lake water nutrient stoichiometry and phytoplankton nutrient limitation varied over the growing season in 11 lakes situated along an altitudinal/climate gradient with low N-deposition (phytoplankton in high-alpine lakes were more prone to P-limitation, and with decreasing altitude became increasingly N- and NP-colimited. Nutrient limitation was additionally most obvious in midsummer. There was also a strong positive correlation between phytoplankton growth and water temperature in the bioassays. Although excess nutrients were available in spring and autumn, on these occasions growth was likely constrained by low water temperatures. These results imply that enhanced N-deposition over the Swedish mountain areas will, with the exception of high-alpine lakes, enhance biomass and drive phytoplankton from N- to P-limitation. However, if not accompanied by warming, N-input from deposition will stimulate limited phytoplankton growth due to low water temperatures during large parts of the growing season. Direct effects of warming, allowing increased metabolic rates and an extension of the growing season, seem equally crucial to synergistically enhance phytoplankton development in these lakes. © 2013 John Wiley & Sons Ltd.

  12. Effects of nutrients, temperature and their interactions on spring phytoplankton community succession in Lake Taihu, China.

    Science.gov (United States)

    Deng, Jianming; Qin, Boqiang; Paerl, Hans W; Zhang, Yunlin; Wu, Pan; Ma, Jianrong; Chen, Yuwei

    2014-01-01

    We examined the potential effects of environmental variables, and their interaction, on phytoplankton community succession in spring using long-term data from 1992 to 2012 in Lake Taihu, China. Laboratory experiments were additionally performed to test the sensitivity of the phytoplankton community to nutrient concentrations and temperature. A phytoplankton community structure analysis from 1992 to 2012 showed that Cryptomonas (Cryptophyta) was the dominant genus in spring during the early 1990s. Dominance then shifted to Ulothrix (Chlorophyta) in 1996 and 1997. However, Cryptomonas again dominated in 1999, 2000, and 2002, with Ulothrix regaining dominance from 2003 to 2006. The bloom-forming cyanobacterial genus Microcystis dominated in 1995, 2001 and 2007-2012. The results of ordinations indicated that the nutrient concentration (as indicated by the trophic state index) was the most important factor affecting phytoplankton community succession during the past two decades. In the laboratory experiments, shifts in dominance among phytoplankton taxa occurred in all nutrient addition treatments. Results of both long term monitoring and experiment indicated that nutrients exert a stronger control than water temperature on phytoplankton communities during spring. Interactive effect of nutrients and water temperature was the next principal factor. Overall, phytoplankton community composition was mediated by nutrients concentrations, but this effect was strongly enhanced by elevated water temperatures.

  13. Resource supply overrides temperature as a controlling factor of marine phytoplankton growth.

    Science.gov (United States)

    Marañón, Emilio; Cermeño, Pedro; Huete-Ortega, María; López-Sandoval, Daffne C; Mouriño-Carballido, Beatriz; Rodríguez-Ramos, Tamara

    2014-01-01

    The universal temperature dependence of metabolic rates has been used to predict how ocean biology will respond to ocean warming. Determining the temperature sensitivity of phytoplankton metabolism and growth is of special importance because this group of organisms is responsible for nearly half of global primary production, sustains most marine food webs, and contributes to regulate the exchange of CO2 between the ocean and the atmosphere. Phytoplankton growth rates increase with temperature under optimal growth conditions in the laboratory, but it is unclear whether the same degree of temperature dependence exists in nature, where resources are often limiting. Here we use concurrent measurements of phytoplankton biomass and carbon fixation rates in polar, temperate and tropical regions to determine the role of temperature and resource supply in controlling the large-scale variability of in situ metabolic rates. We identify a biogeographic pattern in phytoplankton metabolic rates, which increase from the oligotrophic subtropical gyres to temperate regions and then coastal waters. Variability in phytoplankton growth is driven by changes in resource supply and appears to be independent of seawater temperature. The lack of temperature sensitivity of realized phytoplankton growth is consistent with the limited applicability of Arrhenius enzymatic kinetics when substrate concentrations are low. Our results suggest that, due to widespread resource limitation in the ocean, the direct effect of sea surface warming upon phytoplankton growth and productivity may be smaller than anticipated.

  14. Net-phytoplankton communities in the Western Boundary Currents and their environmental correlations

    Science.gov (United States)

    Chen, Yunyan; Sun, Xiaoxia; Zhun, Mingliang

    2017-05-01

    This study investigated net-phytoplankton biomass, species composition, the phytoplankton abundance horizontal distribution, and the correlations between net-phytoplankton communities and mesoscale structure that were derived from the net samples taken from the Western Boundary Currents during summer, 2014. A total of 199 phytoplankton species belonging to 61 genera in four phyla were identified. The dominant species included Climacodium frauenfeldianum, Thalassiothrix longissima, Rhizosolenia styliformis var. styliformis, Pyrocystis noctiluca, Ceratium trichoceros, and Trichodesmium thiebautii. Four phytoplankton communities were divided by cluster analysis and the clusters were mainly associated with the North Equatorial Counter Current (NECC), the North Equatorial Current (NEC), the Subtropical Counter Current (STCC), and the Luzon Current (LC), respectively. The lowest phytoplankton cell abundance and the highest Trichodesmium filament abundance were recorded in the STCC region. The principal component analysis showed that T. thiebautii preferred warm and nutrient poor water. There was also an increase in phytoplankton abundance and biomass near 5°N in the NECC region, where they benefit from upwellings and eddies.

  15. Influence of re-flooding on phytoplankton assemblages in a temperate wetland following prolonged drought

    Directory of Open Access Journals (Sweden)

    Luciana Avigliano

    2014-02-01

    Full Text Available Wetlands can experience drying and flooding cycles which influence the dynamics of the phytoplankton assemblages. The aim of our study was to evaluate changes in the phytoplankton structure during a drought/flood period in a warm-temperate wetland. We hypothesized that fluctuations in water level and development of macrophytes favour the development of fast-growing algae with adaptations to low light conditions. We studied algal and cyanobacterial colonization and succession in the nascent planktonic habitat in a wetland in the Southern Hemisphere (Argentina. We assessed changes in phytoplankton biovolume, chlorophyll a concentration (Chl a, richness, diversity, and evenness throughout a drought/flood period. Phytoplankton species were classified into ecological functional groups (FG. Multivariate analysis (RDA showed that water level, conductivity and percentage macrophyte cover of the site surface (PCSS explained the variability in the phytoplankton assemblage structure in terms of classes and FG. Particularly, FGs T and LM responded to the changes during the drought/flood cycle, probably due to light constraints and stability of the water column induced by the development of emergent and free-floating macrophytes. Our study expands the knowledge of phytoplankton species composition and ecological FG succession under free-floating macrophyte cover in a re-flooding episode. We conclude that water depth and development of macrophytes are the key factors in shaping phytoplankton species structure in a temporary wetland.

  16. Closely related phytoplankton species produce similar suites of dissolved organic matter

    Directory of Open Access Journals (Sweden)

    Jamie William Becker

    2014-03-01

    Full Text Available Production of dissolved organic matter (DOM by marine phytoplankton supplies the majority of organic substrate consumed by heterotrophic bacterioplankton in the sea. This production and subsequent consumption converts a vast quantity of carbon, nitrogen and phosphorus between organic and inorganic forms, directly impacting global cycles of these biologically important elements. Details regarding the chemical composition of DOM produced by marine phytoplankton are sparse, and while often assumed, it is not currently known if phylogenetically distinct groups of marine phytoplankton release characteristic suites of DOM. To investigate the relationship between specific phytoplankton groups and the DOM they release, hydrophobic phytoplankton-derived dissolved organic matter (DOMP from eight axenic strains was analyzed using high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS. Identification of DOM features derived from Prochlorococcus, Synechococcus, Thalassiosira and Phaeodactylum revealed DOMP to be complex and highly strain dependent. Connections between DOMP features and the phylogenetic relatedness of these strains were identified on multiple levels of phylogenetic distance, suggesting that marine phytoplankton produce DOM that in part reflects its phylogenetic origin. Chemical information regarding the size and polarity ranges of features from defined biological sources was also obtained. Our findings reveal DOMP composition to be partially conserved among related phytoplankton species, and implicate marine DOM as a potential factor influencing microbial diversity in the sea by acting as a link between autotrophic and heterotrophic microbial community structures.

  17. Phytoplankton community dynamic detection from the chlorophyll-specific absorption coefficient in productive inland waters

    Directory of Open Access Journals (Sweden)

    Fernanda Sayuri Yoshino Watanabe

    2017-10-01

    Full Text Available Abstract Aim: In this research, we investigated the spectral variability of the specific phytoplankton absorption coefficient, a*φ, measured in a tropical meso-to-hypertrophic reservoir, aiming to find spectral features associated with the chlorophyll-a (chla and other accessory pigments present in different phytoplankton species. Methods To accomplish this research, two fieldworks were carried out in different seasons in order to report a high bio-optical variation. Phytoplankton absorption coefficient, aφ, and chla concentration were measured in laboratory to estimate a*φ. Results The outcomes have indicated that there is a remarkable phytoplankton community dynamic as spatially as seasonally. Chla absorption features were well-defined at 440 nm and 675 nm. Conclusions All the a*φ spectra exhibited the absorption peak around 630 nm associated with phycocyanin pigment present in cyanobacteria. Some spectra have shown a peak at about 460 nm, which is related to chlorophyll b and chlorophyll c (chlb and chlc, respectively found in different phytoplankton species. In turn, absorption features of carotenoids around 490 nm also were identified, however, well defined just in curves measured in austral autumn. Such spectral features are found in phytoplankton groups already identified in the study area such as Chlorophyceae, Bacillariophyceae, Cyanophyceae, Conjugatophyceae, Chrysophyceae, among others. We expect that the results are useful in researches about remote sensing of phytoplankton and eutrophication in reservoirs.

  18. Phytoplankton and water quality in a Mediterranean drinking-water reservoir (Marathonas Reservoir, Greece).

    Science.gov (United States)

    Katsiapi, Matina; Moustaka-Gouni, Maria; Michaloudi, Evangelia; Kormas, Konstantinos Ar

    2011-10-01

    Phytoplankton and water quality of Marathonas drinking-water Reservoir were examined for the first time. During the study period (July-September 2007), phytoplankton composition was indicative of eutrophic conditions although phytoplankton biovolume was low (max. 2.7 mm³ l⁻¹). Phytoplankton was dominated by cyanobacteria and diatoms, whereas desmids and dinoflagellates contributed with lower biovolume values. Changing flushing rate in the reservoir (up to 0.7% of reservoir's water volume per day) driven by water withdrawal and occurring in pulses for a period of 15-25 days was associated with phytoplankton dynamics. Under flushing pulses: (1) biovolume was low and (2) both 'good' quality species and the tolerant to flushing 'nuisance' cyanobacterium Microcystis aeruginosa dominated. According to the Water Framework Directive, the metrics of phytoplankton biovolume and cyanobacterial percentage (%) contribution indicated a moderate ecological water quality. In addition, the total biovolume of cyanobacteria as well as the dominance of the known toxin-producing M. aeruginosa in the reservoir's phytoplankton indicated a potential hazard for human health according to the World Health Organization.

  19. [Phytoplankton Light Absorption Properties During the Blooms in Adjacent Waters of the Changjiang Estuary].

    Science.gov (United States)

    Liu, Yang-yang; Shen, Fang; Li, Xiu-zhen

    2015-06-01

    Phytoplankton dominant species and their light absorption properties during the blooms occurred in August 2013 in adjacent waters of the Changjiang Estuary were analyzed. The results showed that phytoplankton blooms broke out in 10 out of 34 investigation stations, among which diatom blooms occurred in 6 stations while 3 stations were predominated by dinoflagellate. Phytoplankton absorption coefficients of both bloom and non-bloom waters exhibited large variations, with respective ranges of 0.199-0.832 m(-1) and 0.012-0.109 m(-1), while phytoplankton specific absorption coefficients spanned much narrower range, with the average values of bloom and non-bloom waters being 0.023 and 0.035 m2 x mg(-1), respectively. When transitioned from bloom to non-bloom waters, the proportion of phytoplankton with larger cell size lowered while that of smaller phytoplankton elevated, causing a less extent of package effect and thus higher specific absorption coefficients. Distinctive absorption spectra were observed between different types of bloom (such as diatom and dinoflagellate blooms) with similar phytoplankton cell size, mostly attributed to distinctive accessory pigment composition. The ratios of diadinoxanthin and chlorophyll-c2 concentrations to chlorophyll-a concentration in dinoflagellate blooms were higher than those in diatom blooms, which largely contributed to the shoulder peaks at 465 nm in dinoflagellate blooms.

  20. Using photopigment biomarkers to quantify sub-lethal effects of petroleum pollution on natural phytoplankton assemblages

    Energy Technology Data Exchange (ETDEWEB)

    Swistak, J.; Pinckney, J.; Piehler, M.; Paerl, H. [Univ. of North Carolina, Morehead City, NC (United States). Inst. of Marine Sciences

    1995-12-31

    Although much work has been undertaken to determine the toxicity of petroleum pollutants to phytoplankton, most studies have used pure cultures to monitor growth of selected phytoplankton species. Fewer have considered the net effect on entire microalgal communities. Using high performance liquid chromatography (HPLC) to characterize diagnostic microalgal pigments, the authors were able to simultaneously assess sub-lethal pollutant effects on entire communities as well as on individual phytoplankton functional groups. Incubations of natural water samples with diesel fuel, an important contributor to coastal petroleum pollution, revealed significant changes in photopigments and relative abundance of taxonomic groups at sub-lethal concentrations. Differential rates of change of indicator pigment concentrations suggest a range of sensitivity among phytoplankton groups. In preliminary experiments, cyanobacteria exhibited the greatest overall tolerance to the diesel fuel concentrations tested, while cryptomonads displayed the most sensitivity. The authors are currently evaluating the responses of seasonal phytoplankton populations from 3 sites exposed to varied levels of petroleum pollution. HPLC will be used to characterize phytoplankton populations and to determine if the most abundant groups are also the most tolerant of diesel fuel. Preliminary experiments indicate that diesel fuel pollution may modify the structure and function of phytoplankton communities and subsequently alter the trophodynamics of impacted systems.

  1. Enhanced crude oil biodegradative potential of natural phytoplankton-associated hydrocarbonoclastic bacteria.

    Science.gov (United States)

    Thompson, Haydn; Angelova, Angelina; Bowler, Bernard; Jones, Martin; Gutierrez, Tony

    2017-07-01

    Phytoplankton have been shown to harbour a diversity of hydrocarbonoclastic bacteria (HCB), yet it is not understood how these phytoplankton-associated HCB would respond in the event of an oil spill at sea. Here, we assess the diversity and dynamics of the bacterial community associated with a natural population of marine phytoplankton under oil spill-simulated conditions, and compare it to that of the free-living (non phytoplankton-associated) bacterial community. While the crude oil severely impacted the phytoplankton population and was likely conducive to marine oil snow formation, analysis of the MiSeq-derived 16S rRNA data revealed dramatic and differential shifts in the oil-amended communities that included blooms of recognized HCB (e.g., Thalassospira, Cycloclasticus), including putative novel phyla, as well as other groups with previously unqualified oil-degrading potential (Olleya, Winogradskyella, and members of the inconspicuous BD7-3 phylum). Notably, the oil biodegradation potential of the phytoplankton-associated community exceeded that of the free-living community, and it showed a preference to degrade substituted and non-substituted polycyclic aromatic hydrocarbons. Our study provides evidence of compartmentalization of hydrocarbon-degrading capacity in the marine water column, wherein HCB associated with phytoplankton are better tuned to degrading crude oil hydrocarbons than that by the community of planktonic free-living bacteria. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  2. Winds and the distribution of nearshore phytoplankton in a stratified lake.

    Science.gov (United States)

    Cyr, Hélène

    2017-10-01

    The distribution of phytoplankton in lakes is notoriously patchy and dynamic, but wind-driven currents and algal buoyancy/motility are thought to determine where algae accumulate. In this study, nearshore phytoplankton were sampled from different parts of a lake basin twice a day for 4-5 consecutive days, in the spring and in late summer, to test whether short-term changes in phytoplankton biomass and community composition can be predicted from wind-driven currents. On windy days, phytoplankton biomass was higher at downwind than at upwind nearshore sites, and the magnitude of this difference increased linearly with increasing wind speed. However, contrary to the generally assumed downwind phytoplankton aggregations, these differences were mostly due to upwelling activity and the dilution of phytoplankton at upwind nearshore sites. The distribution of individual taxa was also related to wind speed, but only during late stratification (except for cryptophytes), and these relationships were consistent with the buoyancy and motility of each group. On windy days, large diatoms and cyanobacteria concentrated upwind, neutrally buoyant taxa (green algae, small diatoms) were homogeneously distributed, and motile taxa (cryptophytes, chrysophytes, dinoflagellates) concentrated downwind. Predictable differences in the biomass and composition of phytoplankton communities could affect the efficiency of trophic transfers in nearshore areas. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Resource Supply Overrides Temperature as a Controlling Factor of Marine Phytoplankton Growth

    Science.gov (United States)

    Marañón, Emilio; Cermeño, Pedro; Huete-Ortega, María; López-Sandoval, Daffne C.; Mouriño-Carballido, Beatriz; Rodríguez-Ramos, Tamara

    2014-01-01

    The universal temperature dependence of metabolic rates has been used to predict how ocean biology will respond to ocean warming. Determining the temperature sensitivity of phytoplankton metabolism and growth is of special importance because this group of organisms is responsible for nearly half of global primary production, sustains most marine food webs, and contributes to regulate the exchange of CO2 between the ocean and the atmosphere. Phytoplankton growth rates increase with temperature under optimal growth conditions in the laboratory, but it is unclear whether the same degree of temperature dependence exists in nature, where resources are often limiting. Here we use concurrent measurements of phytoplankton biomass and carbon fixation rates in polar, temperate and tropical regions to determine the role of temperature and resource supply in controlling the large-scale variability of in situ metabolic rates. We identify a biogeographic pattern in phytoplankton metabolic rates, which increase from the oligotrophic subtropical gyres to temperate regions and then coastal waters. Variability in phytoplankton growth is driven by changes in resource supply and appears to be independent of seawater temperature. The lack of temperature sensitivity of realized phytoplankton growth is consistent with the limited applicability of Arrhenius enzymatic kinetics when substrate concentrations are low. Our results suggest that, due to widespread resource limitation in the ocean, the direct effect of sea surface warming upon phytoplankton growth and productivity may be smaller than anticipated. PMID:24921945

  4. Response of phytoplankton to an experimental fish culture in net cages in a subtropical reservoir.

    Science.gov (United States)

    Bartozek, E C R; Bueno, N C; Feiden, A; Rodrigues, L C

    2016-01-01

    This study aimed to evaluate nutrients concentration and spatial-temporal changes in phytoplankton biovolume during an experimental fish culture in net cages in a lateral arm of Salto Caxias reservoir, Brazil. Two sampling stations were placed in the affected lateral arm and other two in a cageless lateral arm. Neither abiotic variables nor phytoplankton biovolume presented significant differences between the treatments. Only temporal changes were confirmed by the analysis performed. Both lateral arms were classified as oligotrophic, reflecting low influence of the net cages. Phytoplankton growth seems to be limited by nitrogen. Biovolume values were, in general, low and five major functional groups were recognized (E, F, G, K and P). In summer higher biovolume values were observed and representatives of Chlorophyceae and Cyanobacteria belonging to the functional groups F and K, respectively, were the most important. In winter phytoplankton was mainly composed by Bacillariophyceae taxa from P group. G group was also restricted to winter and E group occurred in winter and summer. The variations recorded in phytoplankton structure appear to have been mainly influenced by seasonal changes in temperature, precipitation and nutrients availability. The effects of net cages on the abiotic variables and phytoplankton biovolume appear to have been small, probably due to the small number of net cages employed and the system dilution capacity. However, a permanent monitoring of phytoplankton is recommended, since this environment has a carrying capacity, from which the trophic state may increase.

  5. NASA Earth Exchange (NEX)

    Data.gov (United States)

    National Aeronautics and Space Administration — The NASA Earth Exchange (NEX) represents a new platform for the Earth science community that provides a mechanism for scientific collaboration and knowledge sharing....

  6. EarthKAM

    Data.gov (United States)

    National Aeronautics and Space Administration — Sponsored by NASA, EarthKAM (Earth Knowledge Acquired by Middle School Students) is an educational outreach program allowing middle school students to take pictures...

  7. Structure and dynamics of phytoplankton in an Amazon lake, Brazil

    Directory of Open Access Journals (Sweden)

    Ise de Goreth Silva

    2010-12-01

    Full Text Available Natural lake systems represent important reservoirs for residential water supply, fish production, recreational activities and enjoyment of their natural beauty. Nevertheless, human impacts may affect their health status resulting in degradation and loss of biodiversity. The aim of the present study was to obtain data on the health status of a natural lake located in an indigenous reservation in the Brazilian Amazon, using the phytoplankton community changes along the rainy (June and dry (November seasons of 2006. We collected water (temperature, pH, Secchi depth and conductivity and phytoplankton samples from the subsurface, middle of the water column, and approximately 30cm above the bottom, over 24-hour sampling periods, from a central station in the lake. Samples taken from biotic and abiotic variables were correlated using canonical correspondence analysis (CCA. Results showed that the lake exhibited high temperatures in both seasons, and showed thermal stratification only during the rainy season. Dissolved oxygen exhibited a clinograde pattern in the rainy season and high oxygen in the hypolimnion in the dry season. In the rainy season, the water near the bottom was acidic, turbid and had a greater concentration of phosphorus. Dissolved oxygen, conductivity, pH, nitrite, total phosphorus and total dissolved phosphorus exhibited diel variations in the rainy season, whereas water temperature, dissolved oxygen, total nitrogen and total dissolved phosphorus exhibited significant differences between hours of the day in the dry season. The phytoplankton was represented by 39 taxa, and Chlorophyta showed the greatest species richness, totaling 25 taxa. Among Chlorophyta, desmids were the most diverse, accounting 52%. Bacillariophyta (nine species was the second most diverse group. Cyanophyta was represented by three species, including Merismopedia tenuissima, the most abundant taxon. Despite the occurrence of taxa that indicate organic pollution

  8. Phytoplankton assemblage of a small, shallow, tropical African reservoir

    Directory of Open Access Journals (Sweden)

    Moshood K Mustapha

    2009-12-01

    Full Text Available I measured physico-chemical properties and phytoplankton in the small, shallow tropical reservoir of Oyun (Offa, Nigeria between January 2002 and December 2003. I identified 25 phytoplankton genera in three sampling stations. Bacillariophyceae dominated (75.3%, followed by Chlorophyceae (12.2%, Cyanobacteria (11.1% and Desmidiaceae (0.73%. The high amount of nutrients (e.g. nitrate, phosphate, sulphate and silica explain phytoplankton heterogeneity (pInvestigué las propiedades físico-químicas y el fitoplancton del pequeño embalse tropical Oyun (Offa, Nigeria entre enero de 2002 y diciembre de 2003, para determinar el efecto de las propiedades físico-químicas en el fitoplancton y la producción de peces. En las tres estaciones estudiadas identifiqué 25 géneros de fitoplancton pertenecientes a cuatro clases. Bacillariophyceae dominó (75.3%, seguida de Chlorophyceae (12.2%, Desmidiaceae (11.1% y Cianobacteria (0.73%. La gran cantidad de nutrientes (e.g. nitrato, fosfato, sulfato y sílice explica la heterogeneidad del fitoplancton (p<0.05, el cual fue abundante durante la época de lluvias. La zona de transición de la reserva tuvo el conjunto más rico y abundante. Las fluctuaciones en la densidad del fitoplancton fueron resultado de la concentración estacional de los nutrientes, la presión del forrajeo y la hidrología. El embalse es eutrófico con agua excelente y fitoplancton diverso, y por tanto su producción pesquera sería alta. Estas condiciones son consecuencia de estrategias como mejores prácticas de gestión de cuencas (BPM para controlar la eutroficación y la sedimentación, y el establecimiento de prioridades legales para un buen uso del agua. Recomiendo medidas adicionales contra la oligotrofía, la hipereutrofia, el exceso de fitoplancton, las cianobacterias tóxicas, las escorrentías de residuos orgánicos y el exceso de sales disueltas.

  9. 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.

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

    Directory of Open Access Journals (Sweden)

    Gerardo Umaña-Villalobos

    2014-08-01

    Full Text Available 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.

  11. Synchronous dynamics and correlations between bacteria and phytoplankton in a subtropical drinking water reservoir.

    Science.gov (United States)

    Liu, Lemian; Yang, Jun; Lv, Hong; Yu, Zheng

    2014-10-01

    Both phytoplankton and bacteria are key and abundant components of aquatic ecosystems and play pivotal roles in maintaining ecosystem structure and function. However, the extent to which phytoplankton community succession influences changes in bacterial community composition (BCC) is largely unknown. In this study, we evaluated the correlations between bacteria and phytoplankton communities and determined the relative contribution of phytoplankton community succession to temporal variation of BCC in a subtropical drinking water reservoir (Tingxi Reservoir, southeast China). Bacterial communities were investigated by quantitative PCR and 454 pyrosequencing of 16S rRNA genes, while phytoplankton communities were analyzed by light microscopy. A remarkable seasonal succession from Cyanophyta to Bacillariophyta was observed during the study period, and this succession can accurately predict the distribution and abundance of the bacterial OTUs based on the discriminant function analysis. Association networks revealed that 38 of the 46 abundant bacterial OTUs exhibited significant correlations with phytoplankton. More interestingly, the positive correlations dominated the associated network, which may suggest that facilitative correlations between phytoplankton and bacteria are more important than inhibitory correlations in the Tingxi Reservoir. In addition, some bacterial OTUs were closely correlated with the dynamics of Microcystis, and they were affiliated with the divisions Acidobacteria, Actinobacteria, and Proteobacteria. Structural equation model showed that succession of phytoplankton community explained the largest part of temporal variation in BCC. Therefore, our data suggest that the distinct succession of phytoplankton community may mediate the temporal dynamics of bacterial community in the Tingxi Reservoir. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

  12. [Temporal and spatial pattern of phytoplankton community and its biodiversity indices in the Danjiangkou Reservoir].

    Science.gov (United States)

    Tan, Xiang; Xia, Xiao-Ling; Cheng, Xiao-Li; Zhang, Quan-Fa

    2011-10-01

    Temporal and spatial patterns of phytoplankton community and their associated influencing factors using canonical correspondence analysis (CCA) were analyzed in the Danjiangkou Reservoir, China. Water quality of the reservoir was also assessed using phytoplankton cell density and biodiversity indices. Results showed that Bacillariophyta and Cyanophyta accounted for 51.08% and 18.39% of all the species, respectively. There was great seasonal variation in phytoplankton assemblage composition, cell density and biodiversity index. In summer, Cyanophyta was dominant and composed of 42.24% of the phytoplankton composition, whereas Bacillariophyta was dominant in spring, summer and winter, and accounted for 77.13%, 61.29% and 50.91% of all species, respectively. The phytoplankton density reached the maximum of 1.76 x 10(6) cells/L in summer, while the lowest value was 2.32 x 10(5) cells/L in autumn. Seasonal variability was the same for the indices of Shannon-Wiener, Simpson and Pielou, and they were 2.08, 0.77, 0.65 in autumn, and decreased to 0.85, 0.32, 0.28 in winter, respectively. Though the spatial variability was not significant in indices H', D, D(m) and J, the difference was significant between the Dan and the Han Reservoirs in terms of phytoplankton composition. The dominant phytoplankton was Bacillariophyta in Dan Reservoir and Cyanophyta in Han Reservoir. The results also indicated that conductivity was the main environmental factor influencing variation in phytoplankton composition except in autumn. The reservoir could be classified as oligotrophication by cell density and the middle level between beta-mesosaprobic zone and oligosaprobic zone using biodiversity indices. The research demonstrated the potential to use phytoplankton community and its biodiversity indices to monitor water quality in the Danjingkou Reservoir.

  13. Phytoplankton community and limnochemistry of Piburger See (Tyrol, Austria 28 years after lake restoration

    Directory of Open Access Journals (Sweden)

    Hansjörg THIES

    2002-02-01

    Full Text Available Phytoplankton community and limnochemistry of Piburger See, a small soft-water, meromictic lake situated at 913 m a.s.l. in a crystalline area of the Central Eastern Alps of Tyrol (Austria, were investigated 28 years after the beginning of lake restoration. Although long-term data of the lake show a declining trend in total phosphorus concentrations and phytoplankton biovolume, the response of Piburger See to the restoration measures carried out in 1970 was delayed by about 20 years. At present the lake is approaching its former oligotrophic level. The most evident difference between the past and present phytoplankton species composition of Piburger See is the actual absence of the Cyanophycean Oscillatoria limosa C. A. Agardh, which markedly increased during the first two decades after the lake restoration (1970-1987. The phytoplankton biovolume recorded in 1998 was lower than in the 1970s and 1980s, while seasonal patterns were similar to those recorded before and later on in the lake restoration. The lowest annual phytoplankton biovolume in 1998 occurred in early winter, while the absolute maximum was observed in metalimnetic water layers in late spring. In 1998 the intra-annual patterns of phytoplankton biovolume and chlorophyll-a compare well. Phytoplankton succession started in early 1998 under ice with coccal green algae followed by flagellated Chrysophyceae during spring. The mid-summer phytoplankton community was dominated by centric Bacillariophyceae, which were later replaced by coccal Cyanophyceae. During autumn, Dinophyceae and Chrysophyceae prevailed. Epilimnetic dominance of centric diatoms during mid summer appears to be a new feature, which in 1998 was related to a strong depletion of dissolved silica and nitrate. Long-term water chemistry and phytoplankton data were checked against local weather data in order to explain the delay in the re-oligotrophication process of Piburger See. However, no clear relationship could be

  14. Phytoplankton species composition of four ecological provinces in Yellow Sea, China

    Science.gov (United States)

    Li, Xiaoqian; Feng, Yuanyuan; Leng, Xiaoyun; Liu, Haijiao; Sun, Jun

    2017-12-01

    The ecological province based on phytoplankton species composition is important to understanding the interplay between environmental parameters and phytoplankton species composition. The aim of this study was to establish phytoplankton species composition ecological pattern thus elucidate the relationship between environmental factors and the phytoplankton species composition in the ecological provinces. Phytoplankton samples were collected from 31 stations in Yellow Sea (121.00°-125.00°E, 32.00°-39.22°N) in November 2014. The samples were enumerated and identified with the Utermöhl method under an optical inverted microscope-AE2000 with magnifications of 200 × or 400 ×. In the present study, a total of 141 taxa belonging to 60 genera of 4 phyla of phytoplankton were identified, among them 101 species of 45 genera were Bacillariophyta, 36 species of 11 genera were Dinophyta, 3 species of 3 genera were Chrysophyta and 1 species of 1 genera was Chlorophyta. The study area was divided into 4 ecological provinces according to an unsupervised cluster algorithm applied to the phytoplankton biomass. A T-S (Temperature-Salinity) scatter diagram depicted with data of water temperature and salinity defined by environmental provinces matched well with the ecological provinces. The results of Canonical Correspondence Analysis (CCA) indicated that the phytoplankton species composition was mainly correlated with temperature, salinity and silicate concentration in the studied area. A method of establishing ecological provinces is useful to further understanding the environmental effects on the marine phytoplankton species composition and the consequent marine biogeochemistry.

  15. Spectroscopic characterization of manganese-doped alkaline earth ...

    Indian Academy of Sciences (India)

    Alkaline earth lead zinc phosphate glasses doped with Mn(II) are characterized by spectroscopic techniques like X-ray diffraction (XRD), UV–visible, differential scanning calorimetry (DSC), electron paramagnetic resonance (EPR), Fourier transform infrared (FTIR) and Raman. Optical absorption spectrum exhibits four ...

  16. Envilab: Measuring phytoplankton in-vivo absorption and scattering properties under tunable environmental conditions.

    Science.gov (United States)

    Göritz, Anna; von Hoesslin, Stefan; Hundhausen, Felix; Gege, Peter

    2017-10-16

    Optical remote sensing of phytoplankton draws on distinctive spectral features which can vary with both species and environmental conditions. Here, we present a set-up (Envilab) for growing phytoplankton under well-defined light, temperature and nutrient conditions. The custom-built light source enables creation of light with spectral composition similar to natural aquatic environments. Spectral tuning allows for light quality studies. Attenuation is monitored with a spectrometer in transmission mode. In combination with automated spectrophotometer and fluorimeter measurements, absorption and excitation-emission-fluorescence spectra are recorded. The set-up opens the door for systematic studies on phytoplankton optical properties and physiology.

  17. Phytoplankton diversity of the Gharni Reservoir in Latur district, Maharashtra, India

    Directory of Open Access Journals (Sweden)

    Vishwas Balasaheb Sakhare

    2015-08-01

    Full Text Available The phytoplanktonic samples were collected from the Gharni Reservoir of Latur district of Maharashtra for a period of one year, from June 2013 to May 2014. Totally 18 species of phytoplankton belonging to different taxonomic groups were identified. Among these 7 species belong to Chlorophyceae, 5 species to Cyanophyceae, 3 species to Bacillariophyceae and 3 species to Euglenophyceae. The phytoplankton productivity fluctuated seasonally and the maximum number of 560 units/liter was recorded during month of February and March and minimum number of 95 units/liter during the month of September.

  18. Phytoplankton in the Upper San Francisco Estuary: Recent Biomass Trends, Their Causes, and Their Trophic Significance

    Directory of Open Access Journals (Sweden)

    Alan Jassby

    2008-02-01

    Full Text Available Several pelagic fish populations in the upper San Francisco Estuary have recently declined to historically low abundances, prompting an interest in the status of their food supply. Previous studies have indicated that the primary food supply for metazoans in the Delta is phytoplankton productivity, and the long-term decrease in phytoplankton over the last few decades may very well play a role in the long-term decline of pelagic fish abundance. Regional phytoplankton biomass trends during 1996–2005, however, are positive in the Delta and neutral in Suisun Bay, the two major sub-regions of the upper estuary. The trend in Delta primary productivity is also positive. Changes in phytoplankton biomass and production during the last decade are therefore unlikely to be the cause of these more recent metazoan declines. The main source of interannual phytoplankton variability in the Delta during 1996–2005, including the upward trend, appears to have been freshwater flow variability and its effect on particle residence time. This conclusion is supported by trend analyses; the concurrence of these time trends at widely-separated stations; empirical models at the annual and monthly time scales; particle residence time estimates; and experience from other estuaries. A significant temperature increase was also noticed, at least partially independent of flow changes, but its net effect on the phytoplankton community is unknown because of differential effects on growth and loss processes. Phytoplankton biomass in Suisun Bay, in contrast to the Delta, did not increase during 1996–2005. Consistent with this observation, Suisun Bay phytoplankton exhibited relatively low responsiveness to flow variability. This behavior differs from earlier chlorophyll-flow relationships reported in the literature. The reason appears to be the invasion of Suisun Bay by a clam—Corbula amurensis—in 1986, which has since maintained the phytoplankton community mostly at low

  19. The community of phytoplankton of the Dagestan area of Caspian Sea in the new ecological conditions

    Directory of Open Access Journals (Sweden)

    A. Sh. Gasanova

    2008-01-01

    Full Text Available The materials about the phytoplankton composition and distribution in the Daghestan region of the Caspian Sea in connection with changing hydrologicaly-hydrochemical regime in conditions of anthropological and biological environment are presented. It was shown, that the change of water regime brought to alterations in floristic composition of sea weeds and succession of phytoplankton change group. Water biocoenosises of different seacoast zone distinguished specific characterdynamics. Introduction of Mnemiopsis leidyi (A. Agassiz influences on phytoplankton association structure

  20. 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

    velocities, settling of cells attached to marine snow aggregates formed from discarded larvacean houses or pteropod feeding webs, and packaging of cells into rapidly falling zooplankton fecal pellets. We quantified the relative significance of these different mechanisms during a diatom bloom in a temperate...... recorded in the water column (by divers) nor in sediment traps. The low coagulation rates were due to a very low 'stickiness' of suspended particles. The dominant diatom, Thalassiosira mendiolana, that accounted for up to 75% of the phytoplankton biomass, was not sticky at al, and did not turn sticky upon...... nutrient depletion in culture experiments. The low particle stickiness recorded may be related to low formation rates by diatoms of transparent exopolymeric particles (TEP), that occurred in low concentrations throughout the study period. Zooplankton grazing rate did not respond to the development...