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Sample records for summer phytoplankton dynamics

  1. Dynamics of phytoplankton communities during late summer around the tip of the Antarctic Peninsula

    Science.gov (United States)

    Mendes, Carlos Rafael Borges; de Souza, Márcio Silva; Garcia, Virginia Maria Tavano; Leal, Miguel Costa; Brotas, Vanda; Garcia, Carlos Alberto Eiras

    The composition and distribution of phytoplankton assemblages around the tip of the Antarctic Peninsula were studied during two summer cruises (February/March 2008 and 2009). Water samples were collected for HPLC/CHEMTAX pigment and microscopic analysis. A great spatial variability in chlorophyll a (Chl a) was observed in the study area: highest levels in the vicinity of the James Ross Island (exceeding 7 mg m-3 in 2009), intermediate values (0.5 to 2 mg m-3) in the Bransfield Strait, and low concentrations in the Weddell Sea and Drake Passage (below 0.5 mg m-3). Phytoplankton assemblages were generally dominated by diatoms, especially at coastal stations with high Chl a concentration, where diatom contribution was above 90% of total Chl a. Nanoflagellates, such as cryptophytes and/or Phaeocystis antarctica, replaced diatoms in open-ocean areas (e.g., Weddell Sea). Many species of peridinin-lacking autotrophic dinoflagellates (e.g., Gymnodinium spp.) were also important to total Chl a biomass at well-stratified stations of Bransfield Strait. Generally, water column structure was the most important environmental factor determining phytoplankton communities' biomass and distribution. The HPLC pigment data also allowed the assessment of different physiological responses of phytoplankton to ambient light variation. The present study provides new insights about the dynamics of phytoplankton in an undersampled region of the Southern Ocean highly susceptible to global climate change.

  2. Dynamics of late spring and summer phytoplankton communities on Georges Bank, with emphasis on diatoms, Alexandrium spp., and other dinoflagellates

    Science.gov (United States)

    Gettings, Rachel M.; Townsend, David W.; Thomas, Maura A.; Karp-Boss, Lee

    2014-05-01

    We analyzed the distribution, abundance, and succession patterns of major phytoplankton taxa on Georges Bank in relation to hydrography, nutrients, and size-fractionated chlorophyll concentrations (>20 μm; Gymnodinium spp., and Prorocentrum spp., had become more abundant. Patches of regenerated silicate during the June-July period appeared to support a post-spring-bloom diatom community on the central crest of the Bank (total diatom cell densities >180,000 cellsl-1) of Leptocylindrus spp., Dactyliosolen spp., and Guinardia flaccida. Multivariate statistical analyses of phytoplankton taxa and station locations revealed distinct assemblages of diatom and dinoflagellate taxa on the Bank throughout the late spring and summer. Results are interpreted in the ecological context of earlier-reported laboratory culture experiments on the competitive interactions between Alexandrium fundyense and diatoms.

  3. 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

  4. 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

  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. The Gulf of Aden Intermediate Water Intrusion Regulates the Southern Red Sea Summer Phytoplankton Blooms.

    Science.gov (United States)

    Dreano, Denis; Raitsos, Dionysios E; Gittings, John; Krokos, George; Hoteit, Ibrahim

    2016-01-01

    Knowledge on large-scale biological processes in the southern Red Sea is relatively limited, primarily due to the scarce in situ, and satellite-derived chlorophyll-a (Chl-a) datasets. During summer, adverse atmospheric conditions in the southern Red Sea (haze and clouds) have long severely limited the retrieval of satellite ocean colour observations. Recently, a new merged ocean colour product developed by the European Space Agency (ESA)-the Ocean Color Climate Change Initiative (OC-CCI)-has substantially improved the southern Red Sea coverage of Chl-a, allowing the discovery of unexpected intense summer blooms. Here we provide the first detailed description of their spatiotemporal distribution and report the mechanisms regulating them. During summer, the monsoon-driven wind reversal modifies the circulation dynamics at the Bab-el-Mandeb strait, leading to a subsurface influx of colder, fresher, nutrient-rich water from the Indian Ocean. Using satellite observations, model simulation outputs, and in situ datasets, we track the pathway of this intrusion into the extensive shallow areas and coral reef complexes along the basin's shores. We also provide statistical evidence that the subsurface intrusion plays a key role in the development of the southern Red Sea phytoplankton blooms.

  7. The Gulf of Aden Intermediate Water Intrusion Regulates the Southern Red Sea Summer Phytoplankton Blooms

    KAUST Repository

    Dreano, Denis; Raitsos, Dionysios E.; Gittings, John; Krokos, George; Hoteit, Ibrahim

    2017-01-01

    Knowledge on large-scale biological processes in the southern Red Sea is relatively limited, primarily due to the scarce in situ, and satellite-derived chlorophyll-a (Chl-a) datasets. During summer, adverse atmospheric conditions in the southern Red Sea (haze and clouds) have long severely limited the retrieval of satellite ocean colour observations. Recently, a new merged ocean colour product developed by the European Space Agency (ESA)-the Ocean Color Climate Change Initiative (OC-CCI)-has substantially improved the southern Red Sea coverage of Chl-a, allowing the discovery of unexpected intense summer blooms. Here we provide the first detailed description of their spatiotemporal distribution and report the mechanisms regulating them. During summer, the monsoon-driven wind reversal modifies the circulation dynamics at the Bab-el-Mandeb strait, leading to a subsurface influx of colder, fresher, nutrient-rich water from the Indian Ocean. Using satellite observations, model simulation outputs, and in situ datasets, we track the pathway of this intrusion into the extensive shallow areas and coral reef complexes along the basin's shores. We also provide statistical evidence that the subsurface intrusion plays a key role in the development of the southern Red Sea phytoplankton blooms.

  8. The Gulf of Aden Intermediate Water Intrusion Regulates the Southern Red Sea Summer Phytoplankton Blooms

    KAUST Repository

    Dreano, Denis

    2017-01-09

    Knowledge on large-scale biological processes in the southern Red Sea is relatively limited, primarily due to the scarce in situ, and satellite-derived chlorophyll-a (Chl-a) datasets. During summer, adverse atmospheric conditions in the southern Red Sea (haze and clouds) have long severely limited the retrieval of satellite ocean colour observations. Recently, a new merged ocean colour product developed by the European Space Agency (ESA)-the Ocean Color Climate Change Initiative (OC-CCI)-has substantially improved the southern Red Sea coverage of Chl-a, allowing the discovery of unexpected intense summer blooms. Here we provide the first detailed description of their spatiotemporal distribution and report the mechanisms regulating them. During summer, the monsoon-driven wind reversal modifies the circulation dynamics at the Bab-el-Mandeb strait, leading to a subsurface influx of colder, fresher, nutrient-rich water from the Indian Ocean. Using satellite observations, model simulation outputs, and in situ datasets, we track the pathway of this intrusion into the extensive shallow areas and coral reef complexes along the basin\\'s shores. We also provide statistical evidence that the subsurface intrusion plays a key role in the development of the southern Red Sea phytoplankton blooms.

  9. Variation of phytoplankton biomass and primary production in Daya Bay during spring and summer

    International Nuclear Information System (INIS)

    Song Xingyu; Huang Liangmin; Zhang Jianlin; Huang, Xiaoping; Zhang Junbin; Yin Jianqiang; Tan Yehui; Liu Sheng

    2004-01-01

    Environmental factors, phytoplankton biomass (Chl a) and primary production of two water areas in Daya Bay (Dapeng'ao Bay and Aotou Bay) were investigated during the transition period from spring to summer. Chl a ranged from 3.20 to 13.62 and 13.43 to 26.49 mg m -3 in Dapeng'ao Bay and Aotou Bay respectively, if data obtained during red tides are excluded. Primary production varied between 239.7 and 1001.4 mgC m -2 d -1 in Dapeng'ao Bay. The regional distribution of Chl a and primary production were mostly consistent from spring to summer in both bays. Seasonal transition characters have been found in Daya Bay from spring to summer, including high values of DO, nitrate and silicate. Size structures of phytoplankton and its primary production do not change very much from spring to summer, with micro-phytoplankton dominating and contributing about 50% of the whole. In Daya Bay, phytoplankton is limited by nitrogen in spring, and by phosphate in summer. Artificial impacts are evident from high temperature effluent from nuclear power stations, aquaculture and sewage. During the investigation, a red tide occurred in Aotou Bay, with a maximum Chl a of 103.23 mg m -3 at surface and primary production of 2721.9 mgC m -2 d -1 in the red tide center. Raised water temperature and nutrient supply from land-sources help to stimulate annual red tides

  10. Seasonal variations of phytoplankton dynamics in Nunatsiavut fjords (Labrador, Canada) and their relationships with environmental conditions

    Science.gov (United States)

    Simo-Matchim, Armelle-Galine; Gosselin, Michel; Blais, Marjolaine; Gratton, Yves; Tremblay, Jean-Éric

    2016-04-01

    We assessed phytoplankton dynamics and its environmental control in four Labrador fjords (Nachvak, Saglek, Okak, and Anaktalak) during summer, early fall and late fall. Primary production and chlorophyll a (chl a) biomass were measured at seven optical depths, including the depth of subsurface chl a maximum (SCM). Phytoplankton abundance, size structure and taxonomy were determined at the SCM. Principal component analysis and non-metric multidimensional scaling were used to analyze relationships between production, biomass and community composition in relation to environmental variables. We observed a marked seasonal variability, with significant differences in phytoplankton structure and function between summer and fall. Surprisingly, primary production and chl a biomass were not significantly different from one fjord to another. The highest values of primary production (1730 mg C m- 2 day- 1) and chl a biomass (96 mg chl a m- 2) were measured during the summer bloom, and those high values indicate that Labrador fjords are highly productive ecosystems. The summer community showed relatively high abundance of nanophytoplankton (2-20 μm) while the fall community was characterized by low primary production and chl a biomass as well as relatively high abundance of picophytoplankton (< 2 μm). The low value of carbon potentially exported out of the euphotic zone throughout the study (≤ 31% of total primary production) suggests that phytoplankton production was mainly grazed by microzooplankton rather than being exported to greater depths. We observed a mixed assemblage of diatoms and flagellates in summer, whereas the fall community was largely dominated by flagellates. Seasonal variations in phytoplankton dynamics were mainly controlled by the strength of the vertical stratification and by the large differences in day length due to the northerly location of Labrador fjords. This study documents for the very first time phytoplankton structure and function in

  11. UVR-induced photoinhibition of summer marine phytoplankton communities from Patagonia

    NARCIS (Netherlands)

    Villafane, Virginia E.; Janknegt, Paul J.; de Graaff, Marco; Visser, Ronald J. W.; de Poll, Willem H. van; Buma, Anita G. J.; Helbling, E. Walter

    During austral summer 2006, experiments were carried out to evaluate the effects of ultraviolet radiation (UVR, 280-400 nm) on carbon fixation of natural phytoplankton assemblages from Patagonia (Argentina). Surface water samples were collected (ca. 100 m offshore) at mid morning using an

  12. 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....

  13. 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

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

    African Journals Online (AJOL)

    Phytoplankton/protozoan dynamics in the Nyara Estuary, a small temporarily open system in the Eastern Cape (South Africa) ... 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.

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

    African Journals Online (AJOL)

    1991-09-04

    Sep 4, 1991 ... warm-water reservoirs from 1989 to 1997 – taxonomic and ... Consideration of phytoplankton dynamics in terms of functional groups offers certain advantages over conventional ... (drinking water) in South Africa (DWA 1986).

  16. 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.

  17. Dynamics of phytoplankton blooms in turbulent vortex cells

    DEFF Research Database (Denmark)

    Lindemann, Christian; Visser, Andre; Mariani, Patrizio

    2017-01-01

    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...... can be maintained with increasing turbulent flow velocities, allowing the apparently counter-intuitive persistence of fast sinking phytoplankton populations in highly turbulent and deep mixed layers. These dynamics demonstrate the role of considering advective transport within a turbulent vortex...

  18. Composition of phytoplankton in the Bransfield Strait and Elephant Island during austral summer of 1999

    Directory of Open Access Journals (Sweden)

    Sonia Sánchez

    2014-06-01

    Full Text Available The authors inform about the composition and distribution of phytoplanktonic community between the first 75 m of depth in Bransfield Strait y around the Elephant island, during the ANTAR X expedition in the 1999 Austral Summer (22nd–29th January 1999. The higher cellular concentration (500 cel/mL was given by the autotrophic nanoplankton, with a high density mainly on the bay stations and down the first 25 m of depth. Among the most representative species we have Leucocryptos marina, Phaeocystis antarctica, the Monadas and the pennate diatoms.

  19. A Satellite-Based Lagrangian View on Phytoplankton Dynamics

    Science.gov (United States)

    Lehahn, Yoav; d'Ovidio, Francesco; Koren, Ilan

    2018-01-01

    The well-lit upper layer of the open ocean is a dynamical environment that hosts approximately half of global primary production. In the remote parts of this environment, distant from the coast and from the seabed, there is no obvious spatially fixed reference frame for describing the dynamics of the microscopic drifting organisms responsible for this immense production of organic matter—the phytoplankton. Thus, a natural perspective for studying phytoplankton dynamics is to follow the trajectories of water parcels in which the organisms are embedded. With the advent of satellite oceanography, this Lagrangian perspective has provided valuable information on different aspects of phytoplankton dynamics, including bloom initiation and termination, spatial distribution patterns, biodiversity, export of carbon to the deep ocean, and, more recently, bottom-up mechanisms that affect the distribution and behavior of higher-trophic-level organisms. Upcoming submesoscale-resolving satellite observations and swarms of autonomous platforms open the way to the integration of vertical dynamics into the Lagrangian view of phytoplankton dynamics.

  20. A Satellite-Based Lagrangian View on Phytoplankton Dynamics.

    Science.gov (United States)

    Lehahn, Yoav; d'Ovidio, Francesco; Koren, Ilan

    2018-01-03

    The well-lit upper layer of the open ocean is a dynamical environment that hosts approximately half of global primary production. In the remote parts of this environment, distant from the coast and from the seabed, there is no obvious spatially fixed reference frame for describing the dynamics of the microscopic drifting organisms responsible for this immense production of organic matter-the phytoplankton. Thus, a natural perspective for studying phytoplankton dynamics is to follow the trajectories of water parcels in which the organisms are embedded. With the advent of satellite oceanography, this Lagrangian perspective has provided valuable information on different aspects of phytoplankton dynamics, including bloom initiation and termination, spatial distribution patterns, biodiversity, export of carbon to the deep ocean, and, more recently, bottom-up mechanisms that affect the distribution and behavior of higher-trophic-level organisms. Upcoming submesoscale-resolving satellite observations and swarms of autonomous platforms open the way to the integration of vertical dynamics into the Lagrangian view of phytoplankton dynamics.

  1. Global patterns of phytoplankton dynamics in coastal ecosystems

    Science.gov (United States)

    Paerl, H.; Yin, Kedong; Cloern, J.

    2011-01-01

    Scientific Committee on Ocean Research Working Group 137 Meeting; Hangzhou, China, 17-21 October 2010; Phytoplankton biomass and community structure have undergone dramatic changes in coastal ecosystems over the past several decades in response to climate variability and human disturbance. These changes have short- and long-term impacts on global carbon and nutrient cycling, food web structure and productivity, and coastal ecosystem services. There is a need to identify the underlying processes and measure the rates at which they alter coastal ecosystems on a global scale. Hence, the Scientific Committee on Ocean Research (SCOR) formed Working Group 137 (WG 137), "Global Patterns of Phytoplankton Dynamics in Coastal Ecosystems: A Comparative Analysis of Time Series Observations" (http://wg137.net/). This group evolved from a 2007 AGU-sponsored Chapman Conference entitled "Long Time-Series Observations in Coastal Ecosystems: Comparative Analyses of Phytoplankton Dynamics on Regional to Global Scales.".

  2. Distribution of Cd, Pb and Cu between dissolved fraction, inorganic particulate and phytoplankton in seawater of Terra Nova Bay (Ross Sea, Antarctica) during austral summer 2011-12.

    Science.gov (United States)

    Illuminati, S; Annibaldi, A; Romagnoli, T; Libani, G; Antonucci, M; Scarponi, G; Totti, C; Truzzi, C

    2017-10-01

    During the austral summer 2011-2012, the metal quotas of Cd, Pb and Cu in the phytoplankton of Terra Nova Bay (TNB, Antarctica) were measured for the first time. Evolution of all the three metal distributions between dissolved and particulate fractions during the season was also evaluated. Metal concentrations were mainly affected by the dynamic of the pack ice melting and phytoplankton activity. In mid-December when TNB area was covered by a thick pack ice layer and phytoplankton activity was very low, all the three metals were present mainly in their dissolved species. When the pack ice started to melt and the water column characteristics became ideal (i.e. moderate stratification, ice free area), the phytoplankton bloom occurred. Cd showed a nutrient-type behaviour with dissolved and particulate fractions mainly influenced by phytoplankton activity. Cd quota showed a mean value of 0.12 ± 0.07 nmol L -1 (30-100% of the total particulate). Also Cu showed a nutrient-type behaviour, with its quota in phytoplankton varying between 0.08 and 2.1 nmol L -1 (20-100% of the total particulate). Pb features the typical distribution of a scavenged element with very low algal content (0.03 ± 0.02 nmol L -1 , representing 20-50% of the total particulate). The vertical distribution of this element was influenced by several factors (e.g. pack ice melting, atmospheric inputs), the phytoplankton activity affecting Pb behaviour only partially. Metal:C ratios provide valuable information on the biological requirements for Cd, Pb and Cu, leading us to better understand their biogeochemical cycles. Copyright © 2017 Elsevier Ltd. All rights reserved.

  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

    International Nuclear Information System (INIS)

    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 N 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 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.

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

    African Journals Online (AJOL)

    In addition to annual patterns, changes in chlorophyll content implied progressive long-term changes in trophic status, especially in Albert Falls, with the emergence of various 'new' taxa (and/or higher peak densities of others). Consideration of phytoplankton dynamics in terms of functional groups offers certain advantages ...

  6. 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.

  7. Recent Primary Production and Small Phytoplankton Contribution in the Yellow Sea during the Summer in 2016

    Science.gov (United States)

    Jang, Hyo Keun; Kang, Jae Jung; Lee, Jae Hyung; Kim, Myungjoon; Ahn, So Hyun; Jeong, Jin-Yong; Yun, Mi Sun; Han, In-Seong; Lee, Sang Heon

    2018-05-01

    The high nutrient concentration associated with the mixing dynamics of two warm and cold water masses supports high primary production in the Yellow Sea. Although various environmental changes have been reported, no recent information on small phytoplankton contribution to the total primary production as an important indicator for marine ecosystem changes is currently available in the Yellow Sea. The major objective of this study is to determine the small (values decades ago. The higher contributions of small phytoplankton to the total chlorophyll a concentration and primary production might be caused by P-limited conditions and this resulted in lower chlorophyll a concentration and total primary production in this study compared to previous studies.

  8. Environmental controls on spatial variability of summer phytoplankton structure and biomass in the Bering Sea

    Science.gov (United States)

    Wang, Yu; Xiang, Peng; Kang, Jian-hua; Ye, You-yin; Lin, Geng-ming; Yang, Qing-liang; Lin, Mao

    2018-01-01

    the community was mainly dominated by Thalassiosira nordenskiöldii, Leptocylindrus danicus, Chaetoceros socialis, Chaetoceros debilis, Fragilariopsis oceanica, Nitzschia closterium and Chaetoceros furcellatus. A diatom bloom was observed near the Bering Strait in the summer of 2010 induced by high availability of nitrate particularly in the Bering Shelf, while water mass transportation mainly influenced communities in the Bering Basin and Slope. The observed fluctuation in both biomass and summer phytoplankton communities in the Bering Sea were mostly influenced by events related to the spring sea ice retreat in 2010.

  9. 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.

  10. 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.

  11. 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

  12. Links between phytoplankton dynamics and shell growth of Arctica islandica on the Faroe Shelf

    Science.gov (United States)

    Bonitz, Fabian Georg Wulf; Andersson, Carin; Trofimova, Tamara; Hátún, Hjálmar

    2018-03-01

    The phytoplankton dynamics on the Faroe Shelf are strongly connected to higher trophic levels, and their inter-annual variability has great importance for many organisms, including the principal fish stocks. Hence, information on the marked phytoplankton variability is scientifically and economically valuable. We show here that the shell growth variability in Arctica islandica shells has the potential to identify periods of increased and decreased phytoplankton concentrations on the Faroe Shelf and in the wider Faroese region in previous centuries. The growth of A. islandica has often been linked to changes in phytoplankton concentrations, i.e., food availability. By cross-matching life-collected and sub-fossil A. islandica shells from two separate locations on the Faroe Shelf, we have built a master chronology, which reaches back to the 17th century. This master chronology correlates well with a Primary Production index for the Faroe Shelf (r = 0.65; p phytoplankton concentrations over the wider Faroese Channel Region, as represented in the Continuous Plankton Recorder surveys, especially for the months June-September (r = 0.39; p < 0.01). In addition, an inverse relationship is observed between the master chronology and on-shelf water temperatures from June-September (r = - 0.29; p < 0.01), which is likely associated with a previously reported inverse relationship between temperatures and the on-shelf primary production. An analysis of the δ18O in the shells shows that the main growing season of the shells presumably occurs during the spring and summer months, which concurs with the main spring bloom.

  13. Microbial activity during a coastal phytoplankton bloom on the Western Antarctic Peninsula in late summer.

    Science.gov (United States)

    Alcamán-Arias, María E; Farías, Laura; Verdugo, Josefa; Alarcón-Schumacher, Tomás; Díez, Beatriz

    2018-05-01

    Phytoplankton biomass during the austral summer is influenced by freezing and melting cycles as well as oceanographic processes that enable nutrient redistribution in the West Antarctic Peninsula (WAP). Microbial functional capabilities, metagenomic and metatranscriptomic activities as well as inorganic 13C- and 15N-assimilation rates were studied in the surface waters of Chile Bay during two contrasting summer periods in 2014. Concentrations of Chlorophyll a (Chla) varied from 0.3 mg m-3 in February to a maximum of 2.5 mg m-3 in March, together with a decrease in nutrients; however, nutrients were never depleted. The microbial community composition remained similar throughout both sampling periods; however, microbial abundance and activity changed with Chla levels. An increased biomass of Bacillariophyta, Haptophyceae and Cryptophyceae was observed along with night-grazing activity of Dinophyceae and ciliates (Alveolates). During high Chla conditions, HCO3- uptake rates during daytime incubations increased 5-fold (>2516 nmol C L-1 d-1), and increased photosynthetic transcript numbers that were mainly associated with cryptophytes; meanwhile night time NO3- (>706 nmol N L-1 d-1) and NH4+ (41.7 nmol N L-1 d-1) uptake rates were 2- and 3-fold higher, respectively, due to activity from Alpha-/Gammaproteobacteria and Bacteroidetes (Flavobacteriia). Due to a projected acceleration in climate change in the WAP, this information is valuable for predicting the composition and functional changes in Antarctic microbial communities.

  14. 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.

  15. Diurnal and spatial (vertical dynamics of nutrients (N, P, Si in four sampling days (summer, fall, winter, and spring in a tropical shallow reservoir and their relationships with the phytoplankton community

    Directory of Open Access Journals (Sweden)

    J. J. Ramírez

    Full Text Available The vertical and diurnal variation of nitrogen and phosphorus forms, as well as that of soluble reactive silica (SRS, were studied in four sampling days at Garças reservoir, a shallow tropical one located in the city of São Paulo, in southeastern Brazil. Except for N-NH4, all other inorganic forms of nitrogen (N-NO2, N-NO3, and total N demonstrated decreased concentrations toward the bottom of reservoir. Similarly, all showed significant diurnal differences on every sampling day, with increased values during the night due to absence of photosynthetic assimilation during that period. In the sampling days, these forms decreased on the spring sampling day due to the bloom of Microcystis registered during this period of the year. All three forms of phosphorus (SRP, particulate P, and total P showed significant vertical variation, except on the fall sampling day. On the summer sampling day there was an increase of both total P and particulate P, the latter because it constitutes more than 70% of the total P during all sampling days. Hourly phosphorus variation was significant during all sampling days, except for the summer one. The SRS vertical variation was significant during all sampling days, except for that in the spring. It was also different hourly on sampling days.

  16. 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

  17. 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

  18. Phytoplankton dynamics in the Gulf of Aqaba (Eilat, Red Sea): A simulation study of mariculture effects

    International Nuclear Information System (INIS)

    Laiolo, Leonardo; Barausse, Alberto; Dubinsky, Zvy; Palmeri, Luca; Goffredo, Stefano; Kamenir, Yury; Al-Najjar, Tariq; Iluz, David

    2014-01-01

    Highlights: • Fish farms in the Gulf of Aqaba strongly affect phytoplankton levels. • Integrating statistics and ecological models help understand phytoplankton dynamics. • Phytoplankton dynamics are driven by mariculture activity and natural forces. • Mariculture can alter typical phytoplankton dynamics and seasonal succession. - Abstract: The northern Gulf of Aqaba is an oligotrophic water body hosting valuable coral reefs. In the Gulf, phytoplankton dynamics are driven by an annual cycle of stratification and mixing. Superimposed on that fairly regular pattern was the establishment of a shallow-water fish-farm initiative that increased gradually until its activity was terminated in June 2008. Nutrient, water temperature, irradiation, phytoplankton data gathered in the area during the years 2007–2009, covering the peak of the fish-farm activity and its cessation, were analyzed by means of statistical analyses and ecological models of phytoplankton dynamics. Two datasets, one from an open water station and one next to the fish farms, were used. Results show that nutrient concentrations and, consequently, phytoplankton abundance and seasonal succession were radically altered by the pollution originating from the fish-farm in the sampling station closer to it, and also that the fish-farm might even have influenced the open water station

  19. Spatial variations of DMS, DMSP and phytoplankton in the Bay of Bengal during the summer monsoon 2001.

    Science.gov (United States)

    Shenoy, D M; Paul, Jane T; Gauns, Mangesh; Ramaiah, N; Kumar, M Dileep

    2006-08-01

    Data on the distribution of dimethylsulphide (DMS) and dimethylsulphoniopropionate (DMSP) in relation to phytoplankton abundance in different oceanic environments is important to understand the biogeochemistry of DMS, which plays an important role in the radiation balance of the earth. During the summer monsoon of 2001 measurements were made for DMS and DMSPt (total DMSP) together with related biological parameters in the Bay of Bengal. Both DMS and DMSPt were restricted to the upper 40 m of the water column. Diatoms accounted for more than 95% of the phytoplankton and were the major contributors to the DMS and DMSPt pool. The mean concentration of DMS in the upper 40 m was observed to be around 1.8+/-1.9 nM in the study area, while DMSPt concentrations varied between 0.7 nM and 40.2 nM with a mean of 10.4+/-8.2 nM. The observed lower DMSPt in the northern Bay in spite of higher mean primary productivity, chlorophyll a and phytoplankton cell counts seemed to result from grazing. Though salinity divides the Bay into different biogeochemical provinces there is no relation between salinity and DMS or DMSPt. On the other hand DMS was linearly related to chlorophyll a:phaeopigments ratio. The results suggest the need for deeper insight into the role of diatoms in the biogeochemical cycling of DMS.

  20. The Temporal Dynamics of Coastal Phytoplankton and Bacterioplankton in the Eastern Mediterranean Sea.

    Directory of Open Access Journals (Sweden)

    Ofrat Raveh

    Full Text Available This study considers variability in phytoplankton and heterotrophic bacterial abundances and production rates, in one of the most oligotrophic marine regions in the world-the Levantine Basin. The temporal dynamics of these planktonic groups were studied in the coastal waters of the southeastern Mediterranean Sea approximately every two weeks for a total of two years. Heterotrophic bacteria were abundant mostly during late summer and midwinter, and were positively correlated with bacterial production and with N2 fixation. Based on size fractionating, picophytoplankton was abundant during the summer, whereas nano-microphytoplankton predominated during the winter and early spring, which were also evident in the size-fractionated primary production rates. Autotrophic abundance and production correlated negatively with temperature, but did not correlate with inorganic nutrients. Furthermore, a comparison of our results with results from the open Levantine Basin demonstrates that autotrophic and heterotrophic production, as well as N2 fixation rates, are considerably higher in the coastal habitat than in the open sea, while nutrient levels or cell abundance are not different. These findings have important ecological implications for food web dynamics and for biological carbon sequestration in this understudied region.

  1. 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

  2. Micro-tidal dependent phytoplankton C-biomass dynamics over two ...

    African Journals Online (AJOL)

    Micro-tidal dependent phytoplankton C-biomass dynamics over two shallow tropical coral reefs. Shamimtaz Bibi Sadally, Nawsheen Taleb-Hossenkhan, Beatriz Casareto, Yoshimi Suzuki, Ranjeet Bhagooli ...

  3. Phytoplankton dynamic responses to oil spill in Mumbai Harbour

    Digital Repository Service at National Institute of Oceanography (India)

    JiyalalRam, M.J.; Ram, A.; Rokade, M.A.; Karangutkar, S.H.; Yengal, B.; Dalvi, S.; Acharya, D.; Sharma, S.; Gajbhiye, S.N.

    have shown that the high concen- tration of oil reduces the phytoplankton growth but when oil becomes in low concentration it, stimulates the growth of microalgae [29-31]. Aksmann and Tukaj [32], believed that the reac- tive oxygen free radicals... in phytoplankton cells increased under the stress of oil pollution and such increment of reactive oxygen free radicals promoted the content of superoxide dismutase in cells at low concentrations of oil, which enhanced the defensive reaction of algae cells...

  4. Seasonal and interannual variability in the taxonomic composition and production dynamics of phytoplankton assemblages in Crater Lake, Oregon

    Science.gov (United States)

    C. David, McIntire; Larson, Gary L.; Truitt, Robert E.

    2007-01-01

    Taxonomic composition and production dynamics of phytoplankton assemblages in Crater Lake, Oregon, were examined during time periods between 1984 and 2000. The objectives of the study were (1) to investigate spatial and temporal patterns in species composition, chlorophyll concentration, and primary productivity relative to seasonal patterns of water circulation; (2) to explore relationships between water column chemistry and the taxonomic composition of the phytoplankton; and (3) to determine effects of primary and secondary consumers on the phytoplankton assemblage. An analysis of 690 samples obtained on 50 sampling dates from 14 depths in the water column found a total of 163 phytoplankton taxa, 134 of which were identified to genus and 101 were identified to the species or variety level of classification. Dominant species by density or biovolume included Nitzschia gracilis, Stephanodiscus hantzschii, Ankistrodesmus spiralis, Mougeotia parvula, Dinobryon sertularia, Tribonema affine, Aphanocapsa delicatissima, Synechocystis sp., Gymnodinium inversum, and Peridinium inconspicuum. When the lake was thermally stratified in late summer, some of these species exhibited a stratified vertical distribution in the water column. A cluster analysis of these data also revealed a vertical stratification of the flora from the middle of the summer through the early fall. Multivariate test statistics indicated that there was a significant relationship between the species composition of the phytoplankton and a corresponding set of chemical variables measured for samples from the water column. In this case, concentrations of total phosphorus, ammonia, total Kjeldahl nitrogen, and alkalinity were associated with interannual changes in the flora; whereas pH and concentrations of dissolved oxygen, orthophosphate, nitrate, and silicon were more closely related to spatial variation and thermal stratification. The maximum chlorophyll concentration when the lake was thermally stratified

  5. Nitrogen uptake by phytoplankton in the Atlantic sector of the Southern Ocean during late austral summer

    CSIR Research Space (South Africa)

    Joubert, WR

    2011-01-01

    Full Text Available are limiting phytoplankton growth despite sufficient irradiance (see also Boyd et al., 2001; Lu- cas et al., 2007). ??N from this study (7.5 mmol m?2 d?1) was in a similar range to the ??N (9.6 mmol m?2 d?1) of the permanently open AZ in the Australian.... Joubert1,2, S. J. Thomalla1,2, H. N. Waldron2, M. I. Lucas3, M. Boye4, F. A. C. Le Moigne4, F. Planchon4, and S. Speich5 1Council for Scientific and Industrial Research, P.O. Box 320, Stellenbosch, 7599, South Africa 2Department of Oceanography...

  6. Nitrogen uptake by phytoplankton in surface waters of the Indian sector of Southern Ocean during austral summer

    Science.gov (United States)

    Tripathy, S. C.; Patra, Sivaji; Vishnu Vardhan, K.; Sarkar, A.; Mishra, R. K.; Anilkumar, N.

    2018-03-01

    This study reports the nitrogen uptake rate (using 15N tracer) of phytoplankton in surface waters of different frontal zones in the Indian sector of the Southern Ocean (SO) during austral summer of 2013. The investigated area encompasses four major frontal systems, i.e., the subtropical front (STF), subantarctic front (SAF), polar front-1 (PF1) and polar front-2 (PF2). Southward decrease of surface water temperature was observed, whereas surface salinity did not show any significant trend. Nutrient (NO3 - and SiO4 4-) concentrations increased southward from STF to PF; while ammonium (NH4 +), nitrite (NO2 -) and phosphate (PO4 3-) remained comparatively stable. Analysis of nutrient ratios indicated potential N-limited conditions at the STF and SAF but no such scenario was observed for PF. In terms of phytoplankton biomass, PF1 was found to be the most productive followed by SAF, whereas PF2 was the least productive region. Nitrate uptake rate increased with increasing latitude, as no systematic spatial variation was discerned for NH4 + and urea (CO(NH2)2). Linear relationship between nitrate and total N-uptake reveals that the studied area is capable of exporting up to 60% of the total production to the deep ocean if the environmental settings are favorable. Like N-uptake rates the f-ratio also increased towards PF region indicating comparatively higher new production in the PF than in the subtropics. The moderately high average f-ratio (0.53) indicates potentially near equal contributions by new production and regenerated production to the total productivity in the study area. Elevation in N-uptake rates with declining temperature suggests that the SO with its vast quantity of cool water could play an important role in drawing down the atmospheric CO2 through the "solubility pump".

  7. Effect of flow rate on environmental variables and phytoplankton dynamics: results from field enclosures

    Science.gov (United States)

    Zhang, Haiping; Chen, Ruihong; Li, Feipeng; Chen, Ling

    2015-03-01

    To investigate the effects of flow rate on phytoplankton dynamics and related environment variables, a set of enclosure experiments with different flow rates were conducted in an artificial lake. We monitored nutrients, temperature, dissolved oxygen, pH, conductivity, turbidity, chlorophyll- a and phytoplankton levels. The lower biomass in all flowing enclosures showed that flow rate significantly inhibited the growth of phytoplankton. A critical flow rate occurred near 0.06 m/s, which was the lowest relative inhibitory rate. Changes in flow conditions affected algal competition for light, resulting in a dramatic shift in phytoplankton composition, from blue-green algae in still waters to green algae in flowing conditions. These findings indicate that critical flow rate can be useful in developing methods to reduce algal bloom occurrence. However, flow rate significantly enhanced the inter-relationships among environmental variables, in particular by inducing higher water turbidity and vegetative reproduction of periphyton ( Spirogyra). These changes were accompanied by a decrease in underwater light intensity, which consequently inhibited the photosynthetic intensity of phytoplankton. These results warn that a universal critical flow rate might not exist, because the effect of flow rate on phytoplankton is interlinked with many other environmental variables.

  8. Assessing spatial and temporal variability of phytoplankton communities' composition in the Iroise Sea ecosystem (Brittany, France): A 3D modeling approach. Part 2: Linking summer mesoscale distribution of phenotypic diversity to hydrodynamism

    Science.gov (United States)

    Cadier, Mathilde; Sourisseau, Marc; Gorgues, Thomas; Edwards, Christopher A.; Memery, Laurent

    2017-05-01

    Tidal front ecosystems are especially dynamic environments usually characterized by high phytoplankton biomass and high primary production. However, the description of functional microbial diversity occurring in these regions remains only partially documented. In this article, we use a numerical model, simulating a large number of phytoplankton phenotypes to explore the three-dimensional spatial patterns of phytoplankton abundance and diversity in the Iroise Sea (western Brittany). Our results suggest that, in boreal summer, a seasonally marked tidal front shapes the phytoplankton species richness. A diversity maximum is found in the surface mixed layer located slightly west of the tidal front (i.e., not strictly co-localized with high biomass concentrations) which separates tidally mixed from stratified waters. Differences in phenotypic composition between sub-regions with distinct hydrodynamic regimes (defined by vertical mixing, nutrients gradients and light penetration) are discussed. Local growth and/or physical transport of phytoplankton phenotypes are shown to explain our simulated diversity distribution. We find that a large fraction (64%) of phenotypes present during the considered period of September are ubiquitous, found in the frontal area and on both sides of the front (i.e., over the full simulated domain). The frontal area does not exhibit significant differences between its community composition and that of either the well-mixed region or an offshore Deep Chlorophyll Maximum (DCM). Only three phenotypes (out of 77) specifically grow locally and are found at substantial concentration only in the surface diversity maximum. Thus, this diversity maximum is composed of a combination of ubiquitous phenotypes with specific picoplankton deriving from offshore, stratified waters (including specific phenotypes from both the surface and the DCM) and imported through physical transport, completed by a few local phenotypes. These results are discussed in light

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

    Directory of Open Access Journals (Sweden)

    Randhir Singh Baghel

    2012-02-01

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

  10. Connections between the growth of Arctica islandica and phytoplankton dynamics on the Faroe Shelf

    Science.gov (United States)

    Bonitz, Fabian; Andersson, Carin; Trofimova, Tamara

    2017-04-01

    In this study we use molluscan sclerochronological techniques in order to obtain closer insights into environmental and ecological dynamics of Faroe Shelf waters. The Faroe Shelf represents a special ecosystem with rich benthic and neritic communities, which also have great importance for many economically relevant fish stocks. Thus, a better understanding of seasonal and year-to-year phytoplankton and stratification dynamics would be useful because they also have implications for higher trophic levels. The water masses of the Faroe Shelf are fairly homogenous and isolated from off-shelf waters but at a certain depth, which is referred to as transition zone, seasonal stratification and horizontal exchange occur. Systematic observations and phytoplankton dynamic investigations have only been performed during the last 29 years but longer records are missing. Thus, we use the growth increment variability in long-lived Arctica islandica shells from the transition zone of the eastern Faroe Shelf to evaluate its potential to estimate on-shelf phytoplankton and stratification dynamics since previous studies have shown that the growth of A. islandica is highly dependent on food availability. We have built a shell-based master-chronology reaching back to the 17th century. Comparisons between the growth indices of our chronology and fluorescence data reveal significant positive relationships. In combination with an index that accounts for stratification even stronger correlations are obtained. This indicates that the growth of A. islandica is largely influenced by a combination of how much phytoplankton is produced and how much actually reaches the bottom, i.e. how well-mixed the water column is. Further significant positive correlations can also be found between the growth indices and other primary productivity data from the Faroe Shelf. In conclusion, our results suggest that the growth indices can be related to year-to-year changes in phytoplankton production and

  11. 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

  12. Dynamics of particulate and dissolved organic and inorganic phosphorus during the peak and declining phase of an iron-induced phytoplankton bloom in the eastern subarctic Pacific

    Science.gov (United States)

    Yoshimura, Takeshi; Nishioka, Jun; Ogawa, Hiroshi; Tsuda, Atsushi

    2018-01-01

    Phosphorus (P) is an essential element for all organisms and thus the P cycle plays a key role in determining the dynamics of lower trophic levels in marine ecosystems. P in seawater occurs conceptually in particulate and dissolved organic and inorganic (POP, PIP, DOP, and DIP, respectively) pools and clarification of the dynamics in these P pools is the basis to assess the biogeochemical cycle of P. Despite its importance, behaviors of each P pool with phytoplankton dynamics have not been fully examined. We measured the four operationally defined P pools (POPop, PIPop, DOPop, and SRP) during an iron-induced phytoplankton bloom (as part of the subarctic ecosystem response to iron enrichment study (SERIES)) in the eastern subarctic Pacific in summer 2002. During our observations of the iron-enriched patch from day 15 to day 26 after the iron infusion, chlorophyll-a concentration in the surface layer decreased from 6.3 to 1.2 μg L- 1, indicating the peak through decline phase of the phytoplankton bloom. At the bloom peak, P was partitioned into POPop, PIPop, and DOPop in proportions of 60, 27, and 13%, respectively. While chlorophyll-a and POPop showed similar temporal variations during the declining phase, PIPop showed a different peak timing with a 2 day delay compared to POPop, resulting in a rapid change in the relative proportion of PIPop to total particulate P (TPP = POPop + PIPop) at the peak (25%) and during the declining phase of the bloom (50%). A part of POPop was replaced by PIPop just after slowing down of phytoplankton growth. This process may have a significant role in the subsequent regeneration of P. We conclude that measurement of TPP alone is insufficient to show the interaction between P and phytoplankton dynamics and fractionation of TPP into POPop and PIPop provides useful insights to clarify the biogeochemical cycle of P.

  13. Exploring the link between micro-nutrients and phytoplankton in the Southern Ocean during the 2007 austral summer

    Directory of Open Access Journals (Sweden)

    Christel eHassler

    2012-07-01

    Full Text Available Bottle assays and large-scale fertilisation experiments have demonstrated that, in the Southern Ocean, iron often controls the biomass and the biodiversity of primary producers. To grow, phytoplankton need numerous other trace metals (micronutrients required for the activity of key enzymes and other intracellular functions. However, little is known of the potential these other trace elements have to limit the growth of phytoplankton in the Southern Ocean. This study investigates the link between the distribution of several micronutrients (Zn, Co, Cu, Cd, Ni and phytoplankton from samples collected during the SAZ-Sense oceanographic expedition (RV Aurora Australis, Jan.–Feb. 2007. Larger phytoplankton are usually associated with lower diffusive supply and higher micronutrient requirement; for this reason, the delineation between phytoplankton larger than 10 µm and those with a size ranging from 0.8–10 µm was made. In addition, different species of phytoplankton may have different requirements to sustain their growth; the phytoplankton biodiversity here was inferred using biomarker pigments. This study, therefore, attempts to elucidate whether micronutrients other than iron need to be considered as parameters for controlling the phytoplankton growth in the Australian sector of the Southern Ocean. Understanding of the parameters controlling phytoplankton is paramount, as it affects the functioning of the Southern Ocean, its marine resources and ultimately the global carbon cycle.

  14. Host-Specificity and Dynamics in Bacterial Communities Associated with Bloom-Forming Freshwater Phytoplankton

    Science.gov (United States)

    Bagatini, Inessa Lacativa; Eiler, Alexander; Bertilsson, Stefan; Klaveness, Dag; Tessarolli, Letícia Piton; Vieira, Armando Augusto Henriques

    2014-01-01

    Many freshwater phytoplankton species have the potential to form transient nuisance blooms that affect water quality and other aquatic biota. Heterotrophic bacteria can influence such blooms via nutrient regeneration but also via antagonism and other biotic interactions. We studied the composition of bacterial communities associated with three bloom-forming freshwater phytoplankton species, the diatom Aulacoseira granulata and the cyanobacteria Microcystis aeruginosa and Cylindrospermopsis raciborskii. Experimental cultures incubated with and without lake bacteria were sampled in three different growth phases and bacterial community composition was assessed by 454-Pyrosequencing of 16S rRNA gene amplicons. Betaproteobacteria were dominant in all cultures inoculated with lake bacteria, but decreased during the experiment. In contrast, Alphaproteobacteria, which made up the second most abundant class of bacteria, increased overall during the course of the experiment. Other bacterial classes responded in contrasting ways to the experimental incubations causing significantly different bacterial communities to develop in response to host phytoplankton species, growth phase and between attached and free-living fractions. Differences in bacterial community composition between cyanobacteria and diatom cultures were greater than between the two cyanobacteria. Despite the significance, major differences between phytoplankton cultures were in the proportion of the OTUs rather than in the absence or presence of specific taxa. Different phytoplankton species favoring different bacterial communities may have important consequences for the fate of organic matter in systems where these bloom forming species occur. The dynamics and development of transient blooms may also be affected as bacterial communities seem to influence phytoplankton species growth in contrasting ways. PMID:24465807

  15. Phytoplankton dynamics in a highly eutrophic estuary in tropical Brazil

    Directory of Open Access Journals (Sweden)

    Marilene Felipe Santiago

    2010-09-01

    Full Text Available The port of Recife in northeastern Brazil is an important ecological and social area but little is known about its environmental quality. Observations, sampling and measurements of phytoplankton were performed during spring and neap tides in the dry (January-February, 2005 and rainy (June, 2005 seasons to assess the environmental quality of the port of Recife. The area had chlorophyll-a concentrations ranging from 3.30 to 54.40 mg m-3, the highest values occurring at low tide during the dry season. A total of 129 species were identified: 53 of them in the dry season and 97 in the rainy season. Diatoms were the most diverse group and comprised 75.47% of the phytoplankton collected in the dry season and 60.82% of those collected in the rainy season. The dry season was characterized by Coscinodiscus sp. and Helicotheca tamesis; the rainy season by Oscillatoria sp. and Coscinodiscus centralis. Species diversity indices varied from 1.06 to 3.74 bits cel-1. Low indices were related to the dominance of Helicotheca tamesis, Coscinodiscus centralis, Coscinodiscus sp. and Aulacoseira granulata. Seasonal forcing, rather than the estuarine flux, determined the phytoplankton community structure. The area is exposed to seasonally varying negative impacts due to metropolitan degradation and the high level of eutrophication.Para avaliar a qualidade ambiental Porto do Recife (Nordeste do Brasil, uma área ecológica e socialmente importante mas pouco investigada, observações, medições e amostragem do fitoplâncton foram realizadas durante as marés de sizígia e quadratura no período de estiagem (janeiro-fevereiro / 2005 e chuvoso (junho/2005. A área apresentou concentração de clorofila a variando de 3,30 a 54,40 mg m-3, com maiores valores registrados durante a maré baixa no período de estiagem. Um total de 129 espécies foi identificada com 53 espécies durante o período de estiagem e 97 espécies no chuvoso. As diatomáceas formaram o grupo mais

  16. Fish and phytoplankton exhibit contrasting temporal species abundance patterns in a dynamic north temperate lake.

    Directory of Open Access Journals (Sweden)

    Gretchen J A Hansen

    Full Text Available Temporal patterns of species abundance, although less well-studied than spatial patterns, provide valuable insight to the processes governing community assembly. We compared temporal abundance distributions of two communities, phytoplankton and fish, in a north temperate lake. We used both 17 years of observed relative abundance data as well as resampled data from Monte Carlo simulations to account for the possible effects of non-detection of rare species. Similar to what has been found in other communities, phytoplankton and fish species that appeared more frequently were generally more abundant than rare species. However, neither community exhibited two distinct groups of "core" (common occurrence and high abundance and "occasional" (rare occurrence and low abundance species. Both observed and resampled data show that the phytoplankton community was dominated by occasional species appearing in only one year that exhibited large variation in their abundances, while the fish community was dominated by core species occurring in all 17 years at high abundances. We hypothesize that the life-history traits that enable phytoplankton to persist in highly dynamic environments may result in communities dominated by occasional species capable of reaching high abundances when conditions allow. Conversely, longer turnover times and broad environmental tolerances of fish may result in communities dominated by core species structured primarily by competitive interactions.

  17. Shallow water processes govern system-wide phytoplankton bloom dynamics: A modeling study

    Science.gov (United States)

    Lucas, L.V.; Koseff, Jeffrey R.; Monismith, Stephen G.; Thompson, J.K.

    2009-01-01

    A pseudo-two-dimensional numerical model of estuarine phytoplankton growth and consumption, vertical turbulent mixing, and idealized cross-estuary transport was developed and applied to South San Francisco Bay. This estuary has two bathymetrically distinct habitat types (deep channel, shallow shoal) and associated differences in local net rates of phytoplankton growth and consumption, as well as differences in the water column's tendency to stratify. Because many physical and biological time scales relevant to algal population dynamics decrease with decreasing depth, process rates can be especially fast in the shallow water. We used the model to explore the potential significance of hydrodynamic connectivity between a channel and shoal and whether lateral transport can allow physical or biological processes (e.g. stratification, benthic grazing, light attenuation) in one sub-region to control phytoplankton biomass and bloom development in the adjacent sub-region. Model results for South San Francisco Bay suggest that lateral transport from a productive shoal can result in phytoplankton biomass accumulation in an adjacent deep, unproductive channel. The model further suggests that turbidity and benthic grazing in the shoal can control the occurrence of a bloom system-wide; whereas, turbidity, benthic grazing, and vertical density stratification in the channel are likely to only control local bloom occurrence or modify system-wide bloom magnitude. Measurements from a related field program are generally consistent with model-derived conclusions. ?? 2008 Elsevier B.V.

  18. Fish and Phytoplankton Exhibit Contrasting Temporal Species Abundance Patterns in a Dynamic North Temperate Lake

    Science.gov (United States)

    Hansen, Gretchen J. A.; Carey, Cayelan C.

    2015-01-01

    Temporal patterns of species abundance, although less well-studied than spatial patterns, provide valuable insight to the processes governing community assembly. We compared temporal abundance distributions of two communities, phytoplankton and fish, in a north temperate lake. We used both 17 years of observed relative abundance data as well as resampled data from Monte Carlo simulations to account for the possible effects of non-detection of rare species. Similar to what has been found in other communities, phytoplankton and fish species that appeared more frequently were generally more abundant than rare species. However, neither community exhibited two distinct groups of “core” (common occurrence and high abundance) and “occasional” (rare occurrence and low abundance) species. Both observed and resampled data show that the phytoplankton community was dominated by occasional species appearing in only one year that exhibited large variation in their abundances, while the fish community was dominated by core species occurring in all 17 years at high abundances. We hypothesize that the life-history traits that enable phytoplankton to persist in highly dynamic environments may result in communities dominated by occasional species capable of reaching high abundances when conditions allow. Conversely, longer turnover times and broad environmental tolerances of fish may result in communities dominated by core species structured primarily by competitive interactions. PMID:25651399

  19. 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

  20. 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

  1. Phytoplankton size structure in the southern Bay of Bengal modified by the Summer Monsoon Current and associated eddies: Implications on the vertical biogenic flux..

    Digital Repository Service at National Institute of Oceanography (India)

    Jyothibabu, R; Vinayachandran, P. N.; Madhu, N.V.; Robin, R; Karman, C.; Jagadeesan, L.; Anjusha, A.

    . Mar. Syst., vol.143; 2015; 98–119 Phytoplankton Size Structure in the Southern Bay of Bengal Modified by the Summer Monsoon Current and Associated Eddies: Implications on the Vertical Biogenic Flux R. Jyothibabu1*, P. N. Vinayachandran2, N. V.... Madhu1, R.S. Robin3, C. Karnan1, L. Jagadeesan1, A. Anjusha1 1CSIR – National Institute of Oceanography, Regional Centre, Kochi, India 2Centre for Atmospheric and Ocean Sciences, Indian Institute of Science, Bangalore, India 3Integrated Coastal...

  2. A comparison between late summer 2012 and 2013 water masses, macronutrients, and phytoplankton standing crops in the northern Bering and Chukchi Seas

    Science.gov (United States)

    Danielson, Seth L.; Eisner, Lisa; Ladd, Carol; Mordy, Calvin; Sousa, Leandra; Weingartner, Thomas J.

    2017-01-01

    Survey data from the northern Bering and Chukchi sea continental shelves in August-September 2012 and 2013 reveal inter-annual differences in the spatial structure of water masses along with statistically significant differences in thermohaline properties, chemical properties, and phytoplankton communities. We provide a set of water mass definitions applicable to the northern Bering and Chukchi continental shelves, and we find that the near-bottom Bering-Chukchi Summer Water (BCSW) was more saline in 2012 and Alaskan Coastal Water (ACW) was warmer in 2013. Both of these water masses carried higher nutrient concentrations in 2012, supporting a larger chlorophyll a biomass that was comprised primarily of small (<10 μm) size class phytoplankton, so the classical relation between higher nutrient loads and larger phytoplankton does not hold for this region in late summer. The distributions of phytoplankton biomass and size structure reveal linkages between the wind fields, seafloor topography, water mass distributions and the pelagic production. The water mass structure, including the strength and location of stratification and fronts, respectively, differed primarily because of the August regional wind field, which was more energetic in 2012 but was more persistent in direction in 2013. High concentrations of ice in winter and early spring in 2012 and 2013 resembled conditions of the 1980s and early 1990s but the regional ice retreat rate has accelerated in the late 1990s and 2000s so the summer and fall ice concentrations more closely resembled those of the last two decades. Our data show that wind forcing can shut down the Alaskan Coastal Current in the NE Chukchi Sea for periods of weeks to months during the ice-covered winter and during the summer when buoyancy forcing is at its annual maximum. We hypothesize that a decrease in salinity and nutrients from 2012 to 2013 was a consequence of a decreased net Bering Strait transport from 2011 to 2012. Biological

  3. Disentangling physical and biological drivers of phytoplankton dynamics in a coastal system.

    Science.gov (United States)

    Cianelli, Daniela; D'Alelio, Domenico; Uttieri, Marco; Sarno, Diana; Zingone, Adriana; Zambianchi, Enrico; d'Alcalà, Maurizio Ribera

    2017-11-20

    This proof-of-concept study integrates the surface currents measured by high-frequency coastal radars with plankton time-series data collected at a fixed sampling point from the Mediterranean Sea (MareChiara Long Term Ecological Research site in the Gulf of Naples) to characterize the spatial origin of phytoplankton assemblages and to scrutinize the processes ruling their dynamics. The phytoplankton community generally originated from the coastal waters whereby species succession was mainly regulated by biological factors (life-cycle processes, species-specific physiological performances and inter-specific interactions). Physical factors, e.g. the alternation between coastal and offshore waters and the horizontal mixing, were also important drivers of phytoplankton dynamics promoting diversity maintenance by i) advecting species from offshore and ii) diluting the resident coastal community so as to dampen resource stripping by dominant species and thereby increase the numerical importance of rarer species. Our observations highlight the resilience of coastal communities, which may favour their persistence over time and the prevalence of successional events over small time and space scales. Although coastal systems may act differently from one another, our findings provide a conceptual framework to address physical-biological interactions occurring in coastal basins, which can be generalised to other areas.

  4. How the Subpolar gyre strength influences phytoplankton blooms dynamics in the North Atlantic

    DEFF Research Database (Denmark)

    Ferreira, Ana Sofia; Payne, Mark; MacKenzie, Brian

    2012-01-01

    height (SSH, from the AVISO project) as a proxy of current strength. Three regions were strategically chosen to characterize positions relative to the NASPG, describing: region 1—the northern part of NASPG, including the Irminger Current (IC); region 2—the North Atlantic Current (NAC), its northwards......Changes in the North Atlantic Subpolar gyre (NASPG) have been linked to the interannual variability of primary production. However, little is known about the mechanisms behind both environmental processes, and how the NASPG strength may extend its potential impacts to higher trophic levels......, including early life stages of commercial fish species. We assess NASPG strength effect on North Atlantic phytoplankton bloom dynamics. We analyse time‐series (from 1998 to 2010) of chlorophyll a (Chl a, from the Globcolour project) annual anomaly as a proxy of phytoplankton abundance, and of sea surface...

  5. Relating coccolithophore calcification rates to phytoplankton community dynamics: Regional differences and implications for carbon export

    Science.gov (United States)

    Poulton, Alex J.; Adey, Tim R.; Balch, William M.; Holligan, Patrick M.

    2007-03-01

    Recent measurements of surface coccolithophore calcification from the Atlantic Ocean (50°N-50°S) are compared to similar measurements from other oceanic settings. By combining the different data sets of surface measurements, we examine general and regional patterns of calcification relative to organic carbon production (photosynthesis) and other characteristics of the phytoplankton community. Generally, surface calcification and photosynthesis are positively correlated, although the strength of the relationship differs between biogeochemical provinces. Relationships between surface calcification, chlorophyll- a and calcite concentrations are also statistically significant, although again there is considerable regional variability. Such variability appears unrelated to phytoplankton community composition or hydrographic conditions, and may instead reflect variations in coccolithophore physiology. The contribution of inorganic carbon fixation (calcification) to total carbon fixation (calcification plus photosynthesis) is ˜1-10%, and we estimate a similar contribution from coccolithophores to total organic carbon fixation. However, these contributions vary between biogeochemical provinces, and occasionally coccolithophores may account for >20% of total carbon fixation in unproductive central subtropical gyres. Combining surface calcification and photosynthetic rates with standing stocks of calcite, particulate organic carbon, and estimated phytoplankton carbon allows us to examine the fates of these three carbon pools. The relative turnover times vary between different biogeochemical provinces, with no clear relationship to the overall productivity or phytoplankton community structure found in each province. Rather, interaction between coccolithophore physiology (coccolith production and detachment rates), species diversity (cell size), and food web dynamics (grazer ecology) may control the composition and turnover times of calcite particles in the upper ocean.

  6. Spin Glasses : Statics and Dynamics : Summer School

    CERN Document Server

    Bovier, Anton

    2009-01-01

    Over the last decade, spin glass theory has turned from a fascinating part of t- oretical physics to a ?ourishing and rapidly growing subject of probability theory as well. These developments have been triggered to a large part by the mathem- ical understanding gained on the fascinating and previously mysterious “Parisi solution” of the Sherrington–Kirkpatrick mean ?eld model of spin glasses, due to the work of Guerra, Talagrand, and others. At the same time, new aspects and applications of the methods developed there have come up. The presentvolumecollects a number of reviewsaswellas shorterarticlesby lecturers at a summer school on spin glasses that was held in July 2007 in Paris. These articles range from pedagogical introductions to state of the art papers, covering the latest developments. In their whole, they give a nice overview on the current state of the ?eld from the mathematical side. The review by Bovier and Kurkova gives a concise introduction to mean ?eld models, starting with the Curie–...

  7. Seasonal Dynamics of Sublittoral Meiobenthos in Relation to Phytoplankton Sedimentation in the Baltic Sea

    Science.gov (United States)

    Ólafsson, E.; Elmgren, R.

    1997-08-01

    Meiobenthic metazoans (40-500) μm were sampled monthly at a 37 m deep station in the north-western Baltic Sea proper. Nematodes dominated the meiofauna, ranging from 67% of total abundance in February to 91% in September. Harpacticoid copepods were the second most common group, ranging from 2% in September to 15% in February. Total meiofauna shell-free dry weight biomass was lowest in winter (0·9 mg 10 cm -2in January), and increased rapidly following the spring bloom, to high values in May-July (peak 1·7 mg 10 cm -2in July). As an annual average, ostracods contributed most to biomass, 38%, while nematodes and harpacticoids made up 24 and 15%, respectively. Only nematodes were common below 2 cm depth in the sediment, and few nematodes penetrated below 4 cm. Of Wieser's morphologically based nematode feeding groups, epistrate feeders dominated the surface sediment, and non-selective deposit feeders dominated the deeper layer in May. Total nematode abundance was significantly different among dates, with lowest numbers in winter and spring (October-April), and almost doubled within about 2 months after the spring phytoplankton bloom in March. There was a significant increase in selective deposit feeders and epistrate feeders after the spring bloom. Harpacticoid copepods were almost all of two species, Pseudobradyasp. and Microarthridion littorale, both of which differed significantly in abundance among months, and displayed continuous reproduction throughout the year, with a peak in pairs in precopula in winter for Pseudobradyasp. and in ovigerous females in M. littoraleafter the spring bloom. Pseudobradyawas significantly more numerous in winter than in other seasons. Microarthridion littoralehad its highest abundance from July to October. Three species of ostracods were common throughout the year and all differed significantly in numbers among months. Turbellaria, Kinorhyncha were found in lowest numbers during winter and peaked in summer. The peak of newly

  8. Phytoplankton bloom and subpolar gyre induced dynamics in the North Atlantic

    DEFF Research Database (Denmark)

    Ferreira, Ana Sofia; Hátún, H.; Counillon, F.

    Several hypotheses have been promoted for phytoplankton bloom onset in the North Atlantic. First we show that the bloom dynamics in the northeastern corner stand out from the rest of the subpolar Atlantic, and thus warrants focused attention. We hypothesized that, for this region, late and weak...... blooms are expected in years of a strong subpolar gyre, i.e. strong atmospheric forcing, and cold and low saline conditions. We apply novel phenology algorithms to satellite ocean colour data, and analyse the outcome together with the subpolar gyre index. We find that the relationship between the bloom...

  9. Seasonal dynamics of phytoplankton in two tropical rivers of varying size and human impact in Southeast Nigeria

    Directory of Open Access Journals (Sweden)

    Okechukwu Idumah Okogwu

    2013-12-01

    Full Text Available Phytoplankton occurrence and dynamics in rivers are mainly shaped by hydrophysical conditions and nutrient availability. Phytoplankton main structuring factors have been poorly studied in West African rivers, and this study was undertaken to identify these conditions in two tropical rivers that vary in size and human impact. For this, environmental variables and phytoplankton monthly samples were collected from the middle reaches of Asu and Cross rivers during an 18 months survey from March 2005-July 2006. Phytoplankton biomass (F=11.87, p=0.003, Shannon-Weiner diversity and species richness (F=5.93, p=0.003 showed significant seasonality in Asu but not in Cross River. Data was analyzed with Canonical correspondence analysis (CCA and showed environmental differences between the two rivers, nitrate in Asu River (5.1-15.5mg/L was significantly higher than Cross River (0.03-1.7mg/L, while PO4 (0.2-0.9mg/L was significantly lower in Asu River compared to Cross River (0.03-2.6mg/L (p<0.05. Eutrophic factors (NO3 determined primarily phytoplankton dynamics in Asu River, especially during the dry season, whereas hydrophysical factors (depth, transparency and temperature shaped phytoplankton in Cross River. Taxa indicative of an eutrophic condition, such as Euglena, Chlorella, Chlorococcus, Ceratium, Peridinium, Anabaena, Aphanizomenon, Closterium, Scenedesmus and Pediastrum spp., were frequently encountered in the shallow impounded Asu River, while riverine species, such as Frustulia rhomboids, Gyrosigma sp., Opephora martyr and Surirella splendida dominated Cross River. A succession pattern was observed in the functional groups identified: Na/MP→TB→P (rainy→dry season was observed in Asu River, whereas MP/D predominated in Cross River for both seasons. We concluded that, if nutrients predominate hydrophysical factors in shaping phytoplankton during dry season (half of the year then, they are as important as hydrophysical factors structuring

  10. Further Studies on the Physical and Biogeochemical Causes for Large Interannual Changes in the Patagonian Shelf Spring-Summer Phytoplankton Bloom Biomass

    Science.gov (United States)

    Signorini, Sergio R.; Garcia, Virginia M.T.; Piola, Alberto R.; Evangelista, Heitor; McClain, Charles R.; Garcia, Carlos A.E.; Mata, Mauricio M.

    2009-01-01

    A very strong and persistent phytoplankton bloom was observed by ocean color satellites during September - December 2003 along the northern Patagonian shelf. The 2003 bloom had the highest extent and chlorophyll a (Chl-a) concentrations of the entire Sea-viewing Wide Field-of-view Sensor (SeaWiFS) period (1997 to present). SeaWiFS-derived Chl-a exceeded 20 mg/cu m in November at the bloom center. The bloom was most extensive in December when it spanned more than 300 km across the shelf and nearly 900 km north-south (35degS to 43degS). The northward reach and the deep penetration on the shelf of the 2003 bloom were quite anomalous when compared with other years, which showed the bloom more confined to the Patagonian shelf break (PSB). The PSB bloom is a conspicuous austral spring-summer feature detected by ocean color satellites and its timing can be explained using the Sverdrup critical depth theory. Based on high-resolution numerical simulations, in situ and remote sensing data, we provide some suggestions for the probable mechanisms responsible for that large interannual change of biomass as seen by ocean color satellites. Potential sources of macro and micro (e.g., Fe) nutrients that sustain the high phytoplankton productivity of the Patagonian shelf waters are identified, and the most likely physical processes that maintain the nutrient balance in the region are discussed.

  11. Spatial variations of DMS, DMSP and phytoplankton in the Bay of Bengal during the summer monsoon 2001

    Digital Repository Service at National Institute of Oceanography (India)

    Shenoy, D.M.; Paul, J.T.; Gauns, M.; Ramaiah, N.; DileepKumar, M.

    in the radiation balance of the earth. During the summer monsoon of 2001 measurements were made for DMS and DMSPt (total DMSP) together with related biological parameters in the Bay of Bengal. Both DMS and DMSPt were restricted to the upper 40 m of the water column...

  12. Cell viability, pigments and photosynthetic performance of Arctic phytoplankton in contrasting ice-covered and open-water conditions during the spring-summer transition

    KAUST Repository

    Alou-Font, E

    2015-12-02

    © Inter-Research 2016. We examined phytoplankton biomass and community composition (mostly based on pigments) as well as cell viability with the cell digestion assay in surface waters of the Canadian Beaufort Sea during the spring-summer transition. Our aim was to understand phytoplankton responses to the large environmental changes (irradiance, temperature and nutrients) occurring during this period. Two categories of stations were visited in May and June 2008: ice-covered (IC), exposed to low irradiances, and open-water (OW), exposed to higher irradiances. We observed a large variation in the percentage of living cells (%LC) relative to the total community. No relationship was found between %LC and nitrate concentration (the nutrient potentially limiting in this environment). The in situ irradiance influenced the status of the cells at OW stations. Mean surface mixed layer irradiances >600 μmol photons m-2 s-1 were associated with low cell viability and a decline in photosynthetic performance (Fv/Fm). For IC stations, %LC declined at temperatures above 0°C, whereas for OW stations, it increased, suggesting that ice melting resulted in the release into surface waters of unhealthy cells from the bottom ice in one case, and that seasonal warming favored the communities present in open waters. A chlorophyll degradation pigment tentatively identified as pyropheophorbide a-\\'like\\' showed a significant negative relationship between its concentration (relative to chlorophyll a) and the %LC and Fv/Fm. Our results suggest that the melting conditions influence the distribution of this pigment and that it may be useful as a marker for low cell viability of ice algae being released into surface waters.

  13. Cell viability, pigments and photosynthetic performance of Arctic phytoplankton in contrasting ice-covered and open-water conditions during the spring-summer transition

    KAUST Repository

    Alou-Font, E; Roy, S; Agusti, Susana; Gosselin, M

    2015-01-01

    © Inter-Research 2016. We examined phytoplankton biomass and community composition (mostly based on pigments) as well as cell viability with the cell digestion assay in surface waters of the Canadian Beaufort Sea during the spring-summer transition. Our aim was to understand phytoplankton responses to the large environmental changes (irradiance, temperature and nutrients) occurring during this period. Two categories of stations were visited in May and June 2008: ice-covered (IC), exposed to low irradiances, and open-water (OW), exposed to higher irradiances. We observed a large variation in the percentage of living cells (%LC) relative to the total community. No relationship was found between %LC and nitrate concentration (the nutrient potentially limiting in this environment). The in situ irradiance influenced the status of the cells at OW stations. Mean surface mixed layer irradiances >600 μmol photons m-2 s-1 were associated with low cell viability and a decline in photosynthetic performance (Fv/Fm). For IC stations, %LC declined at temperatures above 0°C, whereas for OW stations, it increased, suggesting that ice melting resulted in the release into surface waters of unhealthy cells from the bottom ice in one case, and that seasonal warming favored the communities present in open waters. A chlorophyll degradation pigment tentatively identified as pyropheophorbide a-'like' showed a significant negative relationship between its concentration (relative to chlorophyll a) and the %LC and Fv/Fm. Our results suggest that the melting conditions influence the distribution of this pigment and that it may be useful as a marker for low cell viability of ice algae being released into surface waters.

  14. Dynamics of phytoplankton productivity and exopolysaccharides (EPS and TEP) pools in the Seine Estuary (France, Normandy) over tidal cycles and over two contrasting seasons.

    Science.gov (United States)

    Morelle, Jérôme; Schapira, Mathilde; Claquin, Pascal

    2017-10-01

    Exopolysaccharides (EPS) play an important role in the carbon flux and may be directly linked to phytoplankton and microphytobenthos production, most notably in estuarine systems. However the temporal and spatial dynamics of estuarine EPS are still not well understood, nor how primary productivity triggers this variability at these different scales. The aim of this study was to investigate the primary productivity of phytoplankton and EPS dynamics in the Seine estuary over a tidal cycle in three different haline zones over two contrasted seasons. The other objectives was to investigate the origin of pools of soluble carbohydrates (S-EPS) and transparent exopolymeric particles (TEP) in phytoplankton, microphytobenthos or other compartments. High frequency measurements of productivity were made in winter and summer 2015. Physical and chemical parameters, biomass and EPS were measured at hourly intervals in sub-surface waters and just above the water sediment-interface. Our results confirmed that high frequency measurements improve the accuracy of primary productivity estimations and associated carbon fluxes in estuaries. The photosynthetic parameters were shown to be strongly controlled by salinity and by the concentrations of suspended particle matter at the smallest temporal and at spatial scales. At these scales, our results showed an inverse relationship between EPS concentrations and biomass and productivity, and a positive relationship with sediment resuspension. Additionally, the distribution of EPS appears to be linked to hydrodynamics with the tide at daily scale and with the winter at seasonal scale. At spatial scale, the maximum turbidity zone played an important role in the distribution of TEP. Our results suggest that, in the Seine estuary, between 9% and 33% of the S-EPS pool in the water column can be attributed to phytoplankton excretion, while only 0.4%-1.6% (up to 6.14% in exceptional conditions) originates from the microphytobenthos compartments

  15. Phytoplankton biomass dynamics and environmental variables around the Rocas Atoll Biological Reserve, South Atlantic

    Directory of Open Access Journals (Sweden)

    Marina Cavalcanti Jales

    2015-12-01

    Full Text Available Abstract The Rocas Atoll Biological Reserve is located in the Atlantic Ocean, at 3º 51' S and 33º 49' W. It lies 143 nautical miles from the City of Natal, Rio Grande do Norte (Brazil. The purpose of this study was to analyze the hydrology, water masses, currents and chlorophyll a content to determine the dynamics of phytoplankton biomass around the Rocas Atoll. Samples were collected in July 2010 in the area around the Atoll, using the Research Vessel Cruzeiro do Sul of the Brazilian Navy. Two transects were established according to the surface currents, one of which at the southeast of the Atoll (SE and the other at norwest (NW. Three collection points were determined on each of these transects. Samples were collected at different depths (surface and DCM - Deep Chlorophyll Maximum and different times (day and night. According to PCA (Principal Component Analysis, the nutrients analyzed, DIN (dissolved inorganic nitrogen, DIP (dissolved inorganic phosphorus and silicate, were inversely correlated with temperature and dissolved oxygen. Most environmental variables showed a significant increase due to the turbulence on the Northwest transect. There was an increase in the concentration of chlorophyll a and nutrients when the temperature and oxygen in the mixed layer was reduced due to the influence of the SACW (South Atlantic Central Water. Despite the increase observed in some variables such as nutrient salts and chlorophyll a, the temperature in the mixed layer attained a mean value of 23.23 ºC due to the predominance of Tropical Water. The increase of the phytoplankton biomass on the NW transect was, therefore, caused by the "island effect" and not by upwelling.

  16. Dynamics of phytoplankton community structure in the South China Sea in response to the East Asian aerosol input

    Science.gov (United States)

    Guo, C.; Yu, J.; Ho, T.-Y.; Wang, L.; Song, S.; Kong, L.; Liu, H.

    2012-04-01

    Recent studies have demonstrated atmospheric deposition as an important source of bioreactive compounds to the ocean. The South China Sea (SCS), where aerosol loading is among the highest in the world, however, is poorly studied, particularly on the in situ response of phytoplankton community structures to atmospheric deposition. By conducting a series of microcosm bioassays at different hydrographical locations and simulating different aerosol event scales, we observed both positive and negative responses to the input of East Asian (EA) aerosol with high nitrogen (N) and trace metal contents, in terms of biomass, composition and physiological characteristics of phytoplankton communities. High levels of aerosol loading relieved phytoplankton nitrogen and trace metal limitations in SCS, and thus increased total phytoplankton biomass, enhanced their physiological indicators (e.g. photosynthetic efficiency) and shifted phytoplankton assemblages from being dominated by picoplankton to microphytoplanton, especially diatoms. However, under low levels of aerosol loading, the composition shift and biomass accumulation were not apparent, suggesting that the stimulation effects might be counterbalanced by enhanced grazing mortality indicated by increased abundance of protist grazers. Trace metal toxicity of the aerosols might also be the reason for the reduction of picocyanobacteria when amended with high EA aerosols. The magnitude and duration of the deposition event, as well as the hydrographical and trophic conditions of receiving waters are also important factors when predicting the influence of an aerosol deposition event. Our results demonstrated different responses of phytoplankton and microbial food web dynamics to different scales of atmospheric input events in SCS and highlighted the need for achieving an accurate comprehension of atmospheric nutrient on the biogeochemical cycles of the oceans.

  17. How do copper contamination pulses shape the regime shifts of phytoplankton-zooplankton dynamics?

    Science.gov (United States)

    Camara, B. I.; Yamapi, R.; Mokrani, H.

    2017-07-01

    The presence of pollutants in waters, particularly from heavy metals, is of grave concern worldwide due to its cytotoxicity to organisms. Fish and aquatic organisms are very sensitive to the increasing Cu concentrations in water. Therefore, Cu toxicity partly depends on water quality. To address the effects of impulsive copper contamination of the phytoplankton-zooplankton population dynamics, we've built a model that focuses on the interaction between algae and Daphnia with deterministic and stochastic impulse copper. In fact the Results have shown three types of outcomes depending on copper concentration. In low (4.4 μgL-1) copper concentration, deterministic and stochastic pulses may promote the persistence of Daphnia and algae populations unlike the absence of pulses. Whereas, in high (28 μgL-1) concentration, it accelerates deficiency and toxicity processes, leads to the extinction of all populations and in intermediate concentrations. Deterministic and stochastic pulses may transform population dynamics in complex oscillations. Numerical results show that the system that has been considered has more complex dynamics including bifurcation, period-doubling oscillations and chaos. Depending on minimum copper concentration in the environment, the bifurcation diagram has highlighted the resilience or the regime shifts of the system in occurrence of pulse contamination.

  18. Dynamical seasonal prediction of Southern African summer precipitation

    CSIR Research Space (South Africa)

    Yuan, C

    2014-01-01

    Full Text Available Pacific as predictors. More recently, they were replaced by two- and one-tiered dynamical 75 forecast systems, but raw model outputs, such as geopotential height at 850 hPa, are often 76 statistically downscaled to achieve better prediction skills... above-normal years, all have a distinct La Niña signal in the tropical Pacific, and 315 among six successfully predicted below-normal years, all but the 2000/2001 austral summer 316 have a distinct El Niño signal. As a result, composites of SST...

  19. The role of phytoplankton dynamics in the seasonal and interannual variability of carbon in the subpolar North Atlantic – a modeling study

    Directory of Open Access Journals (Sweden)

    S. R. Signorini

    2012-05-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

  1. Dynamics of size-fractionated phytoplankton biomass in a monsoonal estuary: Patterns and drivers for seasonal and spatial variability

    Science.gov (United States)

    Rajaneesh, K. M.; Mitbavkar, Smita; Anil, Arga Chandrashekar

    2018-07-01

    Phytoplankton size-fractionated biomass is an important determinant of the type of food web functioning in aquatic ecosystems. Knowledge about the effect of seasonal salinity gradient on the size-fractionated biomass dynamics is still lacking, especially in tropical estuaries experiencing monsoon. The phytoplankton size-fractionated chlorophyll a biomass (>3 μm and 3 μm size-fraction was the major contributor to the total phytoplankton chlorophyll a biomass with the ephemeral dominance of biomass concentration of both size-fractions showed signs of recovery with increasing salinity downstream towards the end of the monsoon season. In contrast, the chlorophyll a biomass response was size-dependent during the non-monsoon seasons with the sporadic dominance (>50%) of biomass during high water temperature episodes from downstream to middle estuary during pre-monsoon and at low salinity and high nutrient conditions upstream during post-monsoon. These conditions also influenced the picophytoplankton community structure with picoeukaryotes dominating during the pre-monsoon, phycoerythrin containing Synechococcus during the monsoon and phycocyanin containing Synechococcus during the post-monsoon. This study highlights switching over of dominance in size-fractionated phytoplankton chlorophyll a biomass at intra, inter-seasonal and spatial scales which will likely govern the estuarine trophodynamics.

  2. Temporal and spatial dynamics of phytoplankton near farm fish in eutrophic reservoir in Pernambuco, Brazil

    Directory of Open Access Journals (Sweden)

    Ariadne do Nascimento Moura

    2012-06-01

    Full Text Available Spatial and temporal variations in phytoplankton communities in continental waters have received attention from limnologists, since they are differently influenced by many physico-chemical and biological factors. This study was undertaken with the aim to identify the environmental variables that influence the temporal and spatial dynamics of the phytoplankton near a fish farm in the Jucazinho reservoir, in a semi-arid region of Northeastern Brazil. Samples were taken from three sampling sites, at two depths during the rainy (Aug 2008, Feb and Mar 2009 and dry (Oct, Nov and Dec 2008 seasons. Phytoplankton was identified, density determined, and biomass values obtained. Concomitantly, abiotic analyses were performed for the characterization of the system. The reservoir was homogeneous with regard to the spatial-temporal variation in hydrological variables: water well oxygenated at the surface and anoxic at the bottom; pH ranging from neutral to alkaline; temperatures always above 25ºC; high turbidity; and high electrical conductivity at all sampling sites and both depths. For both seasons, there was limited nitrogen and high concentrations of phosphorus. Cyanophyta species were predominant, generally representing 80% of the phytoplankton biomass throughout practically the entire study, at all sampling sites and both depths. Co-dominance of cyanobacteria belonging to H1, MP, S1 and Sn associations was recorded in most of the months studied, except August 2008, when there was a substitution of the S1 association (Planktothrix agardhii by the P association (Aulacoseira granulata. Water temperature, precipitation and pH were the parameters with the greatest influence over the temporal variation in phytoplankton, whereas the vertical distribution of the phytoplankton biomass was directly related to the availability of light in the wáter column. There were no spatial or temporal differences in water quality, likely due to the fact that the sampling

  3. Dynamical effects of vegetation on the 2003 summer heat waves

    Science.gov (United States)

    Stéfanon, M.

    2012-04-01

    Dynamical effects of vegetation on the 2003 summer heat waves Marc Stéfanon(1), Philippe Drobinski(1), Fabio D'Andrea(1), Nathalie de Noblet(2) (1) IPSL/LMD, France; (2) IPSL/LSCE, France The land surface model (LSM) in regional climate models (RCMs) plays a key role in energy and water exchanges between land and atmosphere. The vegetation can affect these exchanges through physical, biophysical and bio-geophysical mechanisms. It participates to evapo-transpiration process which determines the partitioning of net radiation between sensible and latent heat flux, through water evaporation from soil throughout the entire root system. For seasonal timescale leaf cover change induced leaf-area index (LAI) and albedo changes, impacting the Earth's radiative balance. In addition, atmospheric chemistry and carbon concentration has a direct effect on plant stomatal structure, the main exchange interface with the atmosphere. Therefore the surface energy balance is intimately linked to the carbon cycle and vegetation conditions and an accurate representation of the Earth's surface is required to improve the performance of RCMs. It is even more crucial for extreme events as heat waves and droughts which display highly nonlinear behaviour. If triggering of heat waves is determined by the large scale, local coupled processes over land can amplify or inhibit heat trough several feedback mechanism. One set of two simulation has been conducted with WRF, using different LSMs. They aim to study drought and vegetation effect on the dynamical and hydrological processes controlling the occurrence and life cycle of heat waves In the MORCE plateform, the dynamical global vegetation model (DGVM) ORCHIDEE is implemented in the atmospheric module WRF. ORCHIDEE is based on three different modules. The first module, called SECHIBA, describes the fast processes such as exchanges of energy and water between the atmosphere and the biosphere, and the soil water budget. The phenology and carbon

  4. Summer drought predictability over Europe: empirical versus dynamical forecasts

    Science.gov (United States)

    Turco, Marco; Ceglar, Andrej; Prodhomme, Chloé; Soret, Albert; Toreti, Andrea; Doblas-Reyes Francisco, J.

    2017-08-01

    Seasonal climate forecasts could be an important planning tool for farmers, government and insurance companies that can lead to better and timely management of seasonal climate risks. However, climate seasonal forecasts are often under-used, because potential users are not well aware of the capabilities and limitations of these products. This study aims at assessing the merits and caveats of a statistical empirical method, the ensemble streamflow prediction system (ESP, an ensemble based on reordering historical data) and an operational dynamical forecast system, the European Centre for Medium-Range Weather Forecasts—System 4 (S4) in predicting summer drought in Europe. Droughts are defined using the Standardized Precipitation Evapotranspiration Index for the month of August integrated over 6 months. Both systems show useful and mostly comparable deterministic skill. We argue that this source of predictability is mostly attributable to the observed initial conditions. S4 shows only higher skill in terms of ability to probabilistically identify drought occurrence. Thus, currently, both approaches provide useful information and ESP represents a computationally fast alternative to dynamical prediction applications for drought prediction.

  5. Dynamics and Composition of the Asian Summer Monsoon Anticyclone

    Science.gov (United States)

    Gottschaldt, K. D.; Schlager, H.; Baumann, R.; Bozem, H.; Cai, D. S.; Eyring, V.; Hoor, P. M.; Graf, P.; Joeckel, P.; Jurkat, T.; Voigt, C.; Grewe, V.; Zahn, A.; Ziereis, H.

    2017-12-01

    This study places trace gas observations in the upper-tropospheric Asian summer monsoon anticyclone (ASMA) obtained with the HALO research aircraft during the ESMVal campaign into the context of regional, intra-annual variability by hindcasts with the EMAC model. The simulations demonstrate that tropospheric trace gas profiles in the monsoon season are distinct from the rest of the year. Air uplifted from the lower troposphere to the tropopause layer dominates the eastern part of the ASMA's interior, while the western part is characterized by subsidence down to the mid-troposphere. Soluble compounds are being washed out when uplifted by convection in the eastern part, where lightning simultaneously replenishes reactive nitrogen in the upper troposphere. Net photochemical ozone production is significantly enhanced in the ASMA, contrasted by an ozone depleting regime in the mid-troposphere and more neutral conditions in autumn and winter. An analysis of multiple monsoon seasons in the simulation shows that stratospherically influenced tropopause layer air is regularly entrained at the eastern ASMA flank, and then transported in the southern fringe around the interior region. Observed and simulated tracer-tracer relations reflect photochemical O3 production, as well as in-mixing from the lower troposphere and the tropopause layer. The simulation additionally shows entrainment of clean air from the equatorial region by northerly winds at the western ASMA flank. Although the in situ measurements were performed towards the end of summer, the main ingredients needed for their interpretation are present throughout the monsoon season.Subseasonal dynamical instabilities of the ASMA effectively overcome horizontal transport barriers, occur quite frequently, and are of paramount importance for the trace gas composition of the ASMA and its outflow into regions around the world.

  6. Modelling system dynamics and phytoplankton diversity at Ranchi lake using the carbon and nutrient mass balance equations.

    Science.gov (United States)

    Mukherjee, B; Nivedita, M; Mukherjee, D

    2014-05-01

    Modelling system dynamics in a hyper-eutrophic lake is quite complex especially with a constant influx of detergents and sewage material which continually changes the state variables and interferes with the assessment of the chemical rhythm occurring in polluted conditions as compared to unpolluted systems. In this paper, a carbon and nutrient mass balance model for predicting system dynamics in a complex environment was studied. Studies were conducted at Ranchi lake to understand the altered environmental dynamics in hyper-eutrophic conditions, and its impact on the plankton community. The lake was monitored regularly for five years (2007 - 2011) and the data collected on the carbon flux, nitrates, phosphates and silicates was used to design a mass balance model for evaluating and predicting the system. The model was then used to correlate the chemical rhythm with that of the phytoplankton dynamics and diversity. Nitrates and phosphates were not limiting (mean nitrate and phosphate concentrations were 1.74 and 0.83 mgl⁻¹ respectively). Free carbon dioxide was found to control the system and, interacting with other parameters determined the diversity and dynamics of the plankton community. N/P ratio determined which group of phytoplankton dominated the community, above 5 it favoured the growth of chlorophyceae while below 5 cyanobacteria dominates. TOC/TIC ratio determined the abundance. The overall system was controlled by the availability of free carbon dioxide which served as a limiting factor.

  7. Thermal ecology of phytoplankton in a desert reservoir

    International Nuclear Information System (INIS)

    Olsen, R.D.; Sommerfeld, M.R.

    1976-01-01

    The physical--chemical limnology and phytoplankton dynamics of Canyon Lake, Arizona, were investigated from February 1971 to July 1973. The reservoir is a warm monomictic lake with pronounced thermal stratification during the summer months. Chemically the lake is hard water of moderate to high alkalinity and salinity. Annual peaks in the phytoplankton standing crop were recorded during early spring and mid- to late summer, and significant depressions occurred during April--May and November to January. The spring peak was composed primarily of centric diatoms, whereas the summer peak was dominated by filamentous Cyanophyceae. The seasonal appearance and variation in population size of individual species were correlated in varying degrees with one or more physical--chemical parameters. Indications are that physical factors (particularly light and water temperature), rather than water chemistry, were the primary parameters regulating seasonal succession

  8. Dynamics of motile phytoplankton in turbulence: Laboratory investigation of microscale patchiness

    Science.gov (United States)

    Crimaldi, J. P.; True, A.; Stocker, R.

    2016-02-01

    Phytoplankton represent the basis of oceanic life and play a critical role in biogeochemical cycles. While phytoplankton are traditionally studied in bulk, their collective impact stems from cell-level processes and interactions at the microscale. A fundamental element that determines these interactions is the small-scale spatial distribution of individual cells: this directly determines the local cell concentration and the probability that two cells contact or interact with each other. The traditional, bulk perspective on phytoplankton distributions is that turbulence acts to smear out patchiness and locally homogenizes the distributions. However, recent numerical simulations suggest that the action of turbulence on motile phytoplankton may be precisely the opposite: by biasing the swimming direction of cells through the action of viscous torques, turbulence is predicted to generate strong patchiness at small scales. Flow-mediated patch formation has been demonstrated experimentally in simple laminar flows, but has never been tested experimentally in turbulence. In this talk we report on preliminary laboratory experiments performed in a purpose-built flow facility that uses a pair of computer-controlled oscillating grids to generate approximately homogenous isotropic 3D turbulence. Turbulent flow characteristics and dissipation rates are first quantified using particle image velocimetry (PIV). Then, 2D distributions of the motile dinoflagellate Heterosigma akashiwo are imaged using planar laser-induced fluorescence (PLIF). Analysis of imaged phytoplankton distributions for patchiness is performed using a Voronoi tessellation approach. Results suggest that motile phytoplankton distributions differ from those of passive particles. Furthermore, computed values for the patch enhancement factor are shown to be roughly consistent with those of previous DNS predictions.

  9. Exploring dynamical complexity in diffusion driven predator-prey systems: Effect of toxin producing phytoplankton and spatial heterogeneities

    International Nuclear Information System (INIS)

    Upadhyay, Ranjit Kumar; Kumari, Nitu; Rai, Vikas

    2009-01-01

    In this paper, dynamical complexities in two reaction-diffusion (RD) model systems are explored. A spatial heterogeneity in the form of linear spatial gradient in the reproductive growth rate of the phytoplankton is incorporated in both the model systems. Extra mortality of the zooplankton due to toxin production by the phytoplankton is included in the second reaction diffusion model system. Effect of toxin production and spatial heterogeneity in the model systems are studied. Toxin production does not seem to have an appreciable effect on the asymptotic dynamics of the model systems. On the other hand, spatial heterogeneity does influence the dynamics. In particular, it increases the frequency of occurrence of chaos as evident from two dimensional parameter scans. Both these model systems display short term recurrent chaos [Rai V. Chaos in natural populations: edge or wedge? Ecol Complex 2004;1: 127-38] as they reside on 'edges of chaos' (EOC) [Rai V, Upadhyay RK. Evolving to the edge of chaos: chance or necessity? Chaos, Solitons and Fractals 2006;30:1074-87]. This suggests that the ecological systems have a tendency to evolve to EOC. The study corroborates the inferences drawn from an earlier study by Rai and Upadhyay [Rai V, Upadhyay RK. Evolving to the edge of chaos: chance or necessity? Chaos, Solitons and Fractals 2006;30:1074-87]. The system's dynamics is largely unpredictable and admits bursts of short-term predictability.

  10. Dynamics and composition of the Asian summer monsoon anticyclone

    Science.gov (United States)

    Gottschaldt, Klaus-Dirk; Schlager, Hans; Baumann, Robert; Sinh Cai, Duy; Eyring, Veronika; Graf, Phoebe; Grewe, Volker; Jöckel, Patrick; Jurkat-Witschas, Tina; Voigt, Christiane; Zahn, Andreas; Ziereis, Helmut

    2018-04-01

    This study places HALO research aircraft observations in the upper-tropospheric Asian summer monsoon anticyclone (ASMA) into the context of regional, intra-annual variability by hindcasts with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. The observations were obtained during the Earth System Model Validation (ESMVal) campaign in September 2012. Observed and simulated tracer-tracer relations reflect photochemical O3 production as well as in-mixing from the lower troposphere and the tropopause layer. The simulations demonstrate that tropospheric trace gas profiles in the monsoon season are distinct from those in the rest of the year, and the measurements reflect the main processes acting throughout the monsoon season. Net photochemical O3 production is significantly enhanced in the ASMA, where uplifted precursors meet increased NOx, mainly produced by lightning. An analysis of multiple monsoon seasons in the simulation shows that stratospherically influenced tropopause layer air is regularly entrained at the eastern ASMA flank and then transported in the southern fringe around the interior region. Radial transport barriers of the circulation are effectively overcome by subseasonal dynamical instabilities of the anticyclone, which occur quite frequently and are of paramount importance for the trace gas composition of the ASMA. Both the isentropic entrainment of O3-rich air and the photochemical conversion of uplifted O3-poor air tend to increase O3 in the ASMA outflow.

  11. Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles

    DEFF Research Database (Denmark)

    Le Quéré, Corinne; Buitenhuis, Erik T.; Moriarty, Róisín

    2016-01-01

    zooplankton community, despite iron limitation of phytoplankton community growth rates. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean....

  12. PHYTOPLANKTON OF THE NORTH-SEA AND ITS DYNAMICS - A REVIEW

    NARCIS (Netherlands)

    REID, PC; LANCELOT, C; GIESKES, WWC; HAGMEIER, E; WEICHART, G

    1990-01-01

    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

  13. PHYTOPLANKTON OF THE NORTH-SEA AND ITS DYNAMICS - A REVIEW

    NARCIS (Netherlands)

    REID, PC; LANCELOT, C; GIESKES, WWC; 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

  14. Bivalve grazing, nutrient cycling and phytoplankton dynamics in an estuarine ecosystem

    NARCIS (Netherlands)

    Prins, T.C.

    1996-01-01


    This thesis has considered the impact of the suspension feeding bivalve Mytilusedulis on nutrient cycling and phytoplankton in an estuarine ecosystem. The research was started within the framework of an extensive research project with the

  15. Dynamic modelling of five different phytoplankton groups in the River Thames (UK)

    Science.gov (United States)

    Bussi, Gianbattista; Whitehead, Paul; Bowes, Michael; Read, Daniel; Dadson, Simon

    2015-04-01

    Phytoplankton play a vital role in fluvial ecosystems, being a major producer of organic carbon, a food source for primary consumers and a relevant source of oxygen for many low-gradient rivers, but also a producer of potentially harmful toxins (e.g. cyanobacteria). For these reasons, the forecast and prevention of algal blooms is fundamental for the safe management of river systems. In this study, we developed a new process-based phytoplankton model for operational management and forecast of algal and cyanobacteria blooms subject to environmental change. The model is based on a mass-balance and it reproduces phytoplankton growth and death, taking into account the controlling effect played by water temperature, solar radiation, self-shading and dissolved phosphorus and silicon concentrations. The model was implemented in five reaches of the River Thames (UK) with a daily time step over a period of three years, and its results were compared to a novel dataset of cytometric data which includes community cell abundance of chlorophytes, diatoms, cyanobacteria, microcystis-like cyanobacteria and picoalgae. The model results were satisfactory in terms of fitting the observed data. A Multi-Objective General Sensitivity Analysis was also carried out in order to quantify model sensitivity to its parameters. It showed that the most influential parameters are phytoplankton growth and death rates, while phosphorus concentration showed little influence on phytoplankton growth, due to the high levels of phosphorus in the River Thames. The model was demonstrated to be a reliable tool to be used in algal bloom forecasting and management.

  16. Phytoplankton Ecology and Hydrological Dynamics of the Yahuarcaca Lake System, Amazonas, Colombia: Integrated Analysis of 16 Years of Study

    Directory of Open Access Journals (Sweden)

    Maria Juliana Salcedo-Hernández

    2012-09-01

    Full Text Available This article provides a synthesis of the current knowledge on the evolving relation between the Amazon River and the Yahuarcaca lagoon system, through the limnological features and the ecology of phytoplankton in a period of sixteen years. The synthesis of the information was conducted by reviewing existing data about the system, for the time indicated, and analyzing it by means of descriptive statistics and linear correlation between the variables found. Also, it contains a summary of the most important aspects of the first attempt in Colombia to evaluate the influence of the flood pulse on the phytoplankton in a daily time scale. The thermal pattern of this laggon system corresponds to a warm and constant polymicthic lake type according to the de Lewis (1983 classification. The physical, chemical and biological variables examined in this várzea system change according to the hydrologic period. The conductivity, transparency and richness of the phytoplankton increase in the low water season, while the nutrient concentration, and the density, productivity and the biomass of phytoplankton increase during the high water season. Nitrate during the low water season and phosphate during the high water season are the most restricting nutrients. The changes that have taken place through these years in the connectivity between the river and the Yahuarcaca lagoon system are reflected in the dynamics of the structure and composition of the phytoplankton. Normal 0 21 false false false ES-CO X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif"; mso-bidi-font-family:"Times New Roman"; mso-ansi-language:ES-CO; mso-fareast-language:ES-CO;}

  17. A river-scale Lagrangian experiment examining controls on phytoplankton dynamics in the presence and absence of treated wastewater effluent high in ammonium

    Science.gov (United States)

    Kraus, Tamara; Carpenter, Kurt; Bergamaschi, Brian; Parker, Alexander; Stumpner, Elizabeth; Downing, Bryan D.; Travis, Nicole; Wilkerson, Frances; Kendall, Carol; Mussen, Timothy

    2017-01-01

    Phytoplankton are critical component of the food web in most large rivers and estuaries, and thus identifying dominant controls on phytoplankton abundance and species composition is important to scientists, managers, and policymakers. Recent studies from a variety of systems indicate that ammonium ( NH+4) in treated wastewater effluent decreases primary production and alters phytoplankton species composition. However, these findings are based mainly on laboratory and enclosure studies, which may not adequately represent natural systems. To test effects of effluent high in ammonium on phytoplankton at the ecosystem scale, we conducted whole-river–scale experiments by halting discharges to the Sacramento River from the regional wastewater treatment plant (WWTP), and used a Lagrangian approach to compare changes in phytoplankton abundance and species composition in the presence (+EFF) and absence (−EFF) of effluent. Over 5 d of downstream travel from 20 km above to 50 km below the WWTP, chlorophyll concentrations declined from 15–25 to ∼2.5 μg L−1, irrespective of effluent addition. Benthic diatoms were dominant in most samples. We found no significant difference in phytoplankton abundance or species composition between +EFF and −EFF conditions. Moreover, greatest declines in chlorophyll occurred upstream of the WWTP where NH+4 concentrations were low. Grazing by clams and zooplankton could not account for observed losses, suggesting other factors such as hydrodynamics and light limitation were responsible for phytoplankton declines. These results highlight the advantages of conducting ecosystem-scale, Lagrangian-based experiments to understand the dynamic and complex interplay between physical, chemical, and biological factors that control phytoplankton populations.

  18. Effects of increase glacier discharge on phytoplankton bloom dynamics and pelagic geochemistry in a high Arctic fjord

    KAUST Repository

    Calleja, Maria Ll.

    2017-07-26

    Arctic fjords experience extremely pronounced seasonal variability and spatial heterogeneity associated with changes in ice cover, glacial retreat and the intrusion of continental shelf’s adjacent water masses. Global warming intensifies natural environmental variability on these important systems, yet the regional and global effects of these processes are still poorly understood. In the present study, we examine seasonal and spatial variability in Kongsfjorden, on the western coast of Spitsbergen, Svalbard. We report hydrological, biological, and biogeochemical data collected during spring, summer, and fall 2012. Our results show a strong phytoplankton bloom with the highest chlorophyll a (Chla) levels ever reported in this area, peaking 15.5 µg/L during late May and completely dominated by large diatoms at the inner fjord, that may sustain both pelagic and benthic production under weakly stratified conditions at the glacier front. A progressively stronger stratification of the water column during summer and fall was shaped by the intrusion of warm Atlantic water (T > 3°C and Sal > 34.65) into the fjord at around 100 m depth, and by turbid freshwater plumes (T < 1°C and Sal < 34.65) at the surface due to glacier meltwater input. Biopolymeric carbon fractions and isotopic signatures of the particulate organic material (POM) revealed very fresh and labile material produced during the spring bloom (13C enriched, with values up to -22.7‰ at the highest Chl a peak, and high in carbohydrates and proteins content -up to 167 and 148 µg/L, respectively-), and a clear and strong continental signature of the POM present during late summer and fall (13C depleted, with values averaging -26.5 ‰, and high in lipid content –up to 92 µg/L-) when freshwater melting is accentuated. Our data evidence the importance of combining both physical (i.e. water mass dominance) and geochemical (i.e. characteristics of material released by glacier runoff) data in order to

  19. Effects of increase glacier discharge on phytoplankton bloom dynamics and pelagic geochemistry in a high Arctic fjord

    KAUST Repository

    Calleja, Maria Ll.; Kerhervé , P.; Bourgeois, S.; Kędra, M.; Leynaert, A.; Devred, E.; Babin, M.; Morata, N.

    2017-01-01

    Arctic fjords experience extremely pronounced seasonal variability and spatial heterogeneity associated with changes in ice cover, glacial retreat and the intrusion of continental shelf’s adjacent water masses. Global warming intensifies natural environmental variability on these important systems, yet the regional and global effects of these processes are still poorly understood. In the present study, we examine seasonal and spatial variability in Kongsfjorden, on the western coast of Spitsbergen, Svalbard. We report hydrological, biological, and biogeochemical data collected during spring, summer, and fall 2012. Our results show a strong phytoplankton bloom with the highest chlorophyll a (Chla) levels ever reported in this area, peaking 15.5 µg/L during late May and completely dominated by large diatoms at the inner fjord, that may sustain both pelagic and benthic production under weakly stratified conditions at the glacier front. A progressively stronger stratification of the water column during summer and fall was shaped by the intrusion of warm Atlantic water (T > 3°C and Sal > 34.65) into the fjord at around 100 m depth, and by turbid freshwater plumes (T < 1°C and Sal < 34.65) at the surface due to glacier meltwater input. Biopolymeric carbon fractions and isotopic signatures of the particulate organic material (POM) revealed very fresh and labile material produced during the spring bloom (13C enriched, with values up to -22.7‰ at the highest Chl a peak, and high in carbohydrates and proteins content -up to 167 and 148 µg/L, respectively-), and a clear and strong continental signature of the POM present during late summer and fall (13C depleted, with values averaging -26.5 ‰, and high in lipid content –up to 92 µg/L-) when freshwater melting is accentuated. Our data evidence the importance of combining both physical (i.e. water mass dominance) and geochemical (i.e. characteristics of material released by glacier runoff) data in order to

  20. Effects of increase glacier discharge on phytoplankton bloom dynamics and pelagic geochemistry in a high Arctic fjord

    Science.gov (United States)

    Calleja, Maria Ll.; Kerhervé, P.; Bourgeois, S.; Kędra, M.; Leynaert, A.; Devred, E.; Babin, M.; Morata, N.

    2017-12-01

    Arctic fjords experience extremely pronounced seasonal variability and spatial heterogeneity associated with changes in ice cover, glacial retreat and the intrusion of continental shelf's adjacent water masses. Global warming intensifies natural environmental variability on these important systems, yet the regional and global effects of these processes are still poorly understood. In the present study, we examine seasonal and spatial variability in Kongsfjorden, on the western coast of Spitsbergen, Svalbard. We report hydrological, biological, and biogeochemical data collected during spring, summer, and fall 2012. Our results show a strong phytoplankton bloom with the highest chlorophyll a (Chla) levels ever reported in this area, peaking 15.5 μg/L during late May and completely dominated by large diatoms at the inner fjord, that may sustain both pelagic and benthic production under weakly stratified conditions at the glacier front. A progressively stronger stratification of the water column during summer and fall was shaped by the intrusion of warm Atlantic water (T > 3 °C and Sal > 34.65) into the fjord at around 100 m depth, and by turbid freshwater plumes (T carbon fractions and isotopic signatures of the particulate organic material (POM) revealed very fresh and labile material produced during the spring bloom (13C enriched, with values up to -22.7‰ at the highest Chl a peak, and high in carbohydrates and proteins content - up to 167 and 148 μg/L, respectively-), and a clear and strong continental signature of the POM present during late summer and fall (13C depleted, with values averaging -26.5‰, and high in lipid content - up to 92 μg/L-) when freshwater melting is accentuated. Our data evidence the importance of combining both physical (i.e. water mass dominance) and geochemical (i.e. characteristics of material released by glacier runoff) data in order to understand the timing, intensity and characteristics of the phytoplankton bloom in

  1. Dynamic Analysis of a Phytoplankton-Fish Model with Biological and Artificial Control

    OpenAIRE

    Wang, Yapei; Zhao, Min; Pan, Xinhong; Dai, Chuanjun

    2014-01-01

    We investigate a nonlinear model of the interaction between phytoplankton and fish, which uses a pair of semicontinuous systems with biological and artificial control. First, the existence of an order-1 periodic solution to the system is analyzed using a Poincaré map and a geometric method. The stability conditions of the order-1 periodic solution are obtained by a theoretical mathematical analysis. Furthermore, based on previous analysis, we investigate the bifurcation in the order-1 periodi...

  2. The Impact of High-Turbidity Water's Seasonal and Decadal Variations on Offshore Phytoplankton and Nutrients Dynamics around The Changjiang Estuary

    Science.gov (United States)

    Ge, J.; Torres, R.; Chen, C.; Bellerby, R. G. J.

    2017-12-01

    The Changjiang Estuary is characterized as strong river discharge into the inner shelf of the East China Sea with abundant sediment load, producing significant high-turbidity water coverage from river mouth to deep region. The growth of offshore phytoplankton is dynamically controlled by river flushed low-salinity and high-turbidity water, and salter water from inner shelf of East China Sea. During last decade, the sediment and nutrients from the Changjiang River has significantly changed, which lead to the variation of offshore phytoplankton dynamics. The variations of sediment, nutrients, and their influenced phytoplankton has been simulated through a comprehensive modeling system, which integrated a multi-scale current-wave-sediment FVCOM model and generic marine biogeochemistry and ecosystem ERSEM model through The Framework for Aquatic Biogeochemical Models (FABM). This model system has successfully revealed the seasonal and decadal variations of sediment, nutrients transport around the inner shelf of the East China Sea. The spring and autumn peaks of phytoplankton growth were correctly captured by simulation. The modeling results, as well as MODIS and GOCI remote sensing, shows a strong sediment decreasing from northern to southern region, which creates different patterns of Chlorophyll-a distribution and seasonal variations. These results indicate the high-turbidity water in northern region strongly influenced the light attenuation in the water column and limits the phytoplankton growth in this relatively higher-nutrient area, especially in the wintertime. The relatively low-turbidity southern region has significant productivity of phytoplankton, even during low-temperature winter. The phytoplankton growth increased in the northern region from 2005 to 2010, with the increase of the nutrient load during this period. Then it became a decreasing trend after 2010.

  3. Phytoplankton dynamics in relation to seasonal variability and upwelling and relaxation patterns at the mouth of Ria de Aveiro (West Iberian Margin over a four-year period.

    Directory of Open Access Journals (Sweden)

    Tânia Vidal

    Full Text Available From June 2004 to December 2007, samples were weekly collected at a fixed station located at the mouth of Ria de Aveiro (West Iberian Margin. We examined the seasonal and inter-annual fluctuations in composition and community structure of the phytoplankton in relation to the main environmental drivers and assessed the influence of the oceanographic regime, namely changes in frequency and intensity of upwelling events, over the dynamics of the phytoplankton assemblage. The samples were consistently handled and a final subset of 136 OTUs (taxa with relative abundance > 0.01% was subsequently submitted to various multivariate analyses. The phytoplankton assemblage showed significant changes at all temporal scales but with an overriding importance of seasonality over longer- (inter-annual or shorter-term fluctuations (upwelling-related. Sea-surface temperature, salinity and maximum upwelling index were retrieved as the main driver of seasonal change. Seasonal signal was most evident in the fluctuations of chlorophyll a concentration and in the high turnover from the winter to spring phytoplankton assemblage. The seasonal cycle of production and succession was disturbed by upwelling events known to disrupt thermal stratification and induce changes in the phytoplankton assemblage. Our results indicate that both the frequency and intensity of physical forcing were important drivers of such variability, but the outcome in terms of species composition was highly dependent on the available local pool of species and the timing of those events in relation to the seasonal cycle. We conclude that duration, frequency and intensity of upwelling events, which vary seasonally and inter-annually, are paramount for maintaining long-term phytoplankton diversity likely by allowing unstable coexistence and incorporating species turnover at different scales. Our results contribute to the understanding of the complex mechanisms of coastal phytoplankton dynamics in

  4. 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.

  5. Dynamics and composition of the Asian summer monsoon anticyclone

    NARCIS (Netherlands)

    Gottschaldt, Klaus Dirk; Schlager, Hans; Baumann, Robert; Sinh Cai, Duy; Eyring, Veronika; Graf, Phoebe; Grewe, V.; Jöckel, Patrick; Jurkat-Witschas, Tina; Voigt, Christiane; Zahn, Andreas; Ziereis, Helmut

    2018-01-01

    This study places HALO research aircraft observations in the upper-tropospheric Asian summer monsoon anticyclone (ASMA) into the context of regional, intra-annual variability by hindcasts with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. The observations were obtained during the Earth

  6. The effect of environmental parameters and cyanobacterial blooms on phytoplankton dynamics of a Portuguese temperate lake

    DEFF Research Database (Denmark)

    De Figueiredo, Daniela R.; P. S. Reboleira, Ana Sofia; Antunes, Sara C.

    2006-01-01

    The increasing occurrence of cyanobacterial blooms in freshwaters is of great concern due to the ability of many cyanobacteria to produce cyanotoxins. In the present work, the eutrophied Vela Lake (Central Portugal), used for recreational purposes and as a water source for agriculture, was monito...... for the phytoplanktonic assemblage during the study period was increased in about 7% achieving a total of 61.0%, indicating a correlation that may be due to the known competitive advantage and/or allelopathy of the bloom-forming cyanobacteria towards microalgae....

  7. 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.

  8. Improved monitoring of phytoplankton bloom dynamics in a Norwegian fjord by integrating satellite data, pigment analysis, and Ferrybox data with a coastal observation network

    Science.gov (United States)

    Volent, Zsolt; Johnsen, Geir; Hovland, Erlend K.; Folkestad, Are; Olsen, Lasse M.; Tangen, Karl; Sørensen, Kai

    2011-01-01

    Monitoring of the coastal environment is vitally important as these areas are of economic value and at the same time highly exposed to anthropogenic influence, in addition to variation of environmental variables. In this paper we show how the combination of bio-optical data from satellites, analysis of water samples, and a ship-mounted automatic flow-through sensor system (Ferrybox) can be used to detect and monitor phytoplankton blooms both spatially and temporally. Chlorophyll a (Chl a) data and turbidity from Ferrybox are combined with remotely sensed Chl a and total suspended matter from the MERIS instrument aboard the satellite ENVISAT (ENVIronmental SATellite) European Space Agency. Data from phytoplankton speciation and enumeration obtained by a national coastal observation network consisting of fish farms and the Norwegian Food Safety Authority are supplemented with data on phytoplankton pigments. All the data sets are then integrated in order to describe phytoplankton bloom dynamics in a Norwegian fjord over a growth season, with particular focus on Emiliania huxleyi. The approach represents a case example of how coastal environmental monitoring can be improved with existing instrument platforms. The objectives of the paper is to present the operative phytoplankton monitoring scheme in Norway, and to present an improved model of how such a scheme can be designed for a large part of the world's coastal areas.

  9. 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.

  10. 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

    The spring bloom is a key annual event in the phenology of pelagic ecosystems, making a major contribution to the oceanic biological carbon pump through the production and export of organic carbon. However, there is little consensus as to the main drivers of spring bloom formation, exacerbated......) of the 2012 North Atlantic spring bloom. The plankton composition and characteristics of the initial stages of the bloom were markedly different between the two basins. The Iceland Basin (ICB) appeared well mixed to > 400 m, yet surface chlorophyll a (0.27–2.2 mg m–3) and primary production (0.06–0.66 mmol C...... suggest micro-zooplankton grazing, potentially coupled with the lack of a seed population of bloom forming diatoms, was restricting diatom growth in the NWB, and that large diatoms may be absent in NWB spring blooms. Despite both phytoplankton communities being in the early stages of bloom formation...

  11. Recent dynamics (1995-1999 of the phytoplankton assemblages in Lago Maggiore as a basic tool for defining association patterns in the Italian deep lakes

    Directory of Open Access Journals (Sweden)

    Pierisa PANZANI

    2002-02-01

    Full Text Available The main goal of the study presented here is to identify a repeatable pattern in the seasonal succession of phytoplankton assemblages in Lago Maggiore. In order to fulfil this objective we analysed the phytoplaktonic succession during a five years period (1995-1999, through the calculation of the Bray-Curtis similarity index applied to biovolume data. A cluster analysis has been then applied to the distance matrix, allowing the identification of sample clusters possessing a similar species composition. The comparison, through the whole period considered, of the phytoplankton assemblages characterising each cluster allowed to recognise six seasonal periods (Winter, Early Spring, Late Spring, Early Summer, Late Summer, Autumn, each of them characterised by a peculiar and repeatable species assemblage. Among the most interesting findings we would mention the existence of a Late Spring/Early Summer association, dominated by Planktothrix rubescens and Fragilaria crotonensis, probably peculiar of the deep subalpine lakes, where these species can better take advantage of the physical and chemical environment of the metalimnetic niche. The identification of a pool of dominant and sub-dominant species common to other southern subalpine lakes and the existence of a similar time periodicity in the development and decline of most of them across this lake district seem to be promising in order to give our results a wider application.

  12. Phytoplankton Communities in Green Bay, Lake Michigan after Invasion by Dreissenid Mussels: Increased Dominance by Cyanobacteria

    Directory of Open Access Journals (Sweden)

    Bart T. De Stasio

    2014-11-01

    Full Text Available Biological invasions of aquatic systems disrupt ecological communities, and cause major changes in diversity and ecosystem function. The Laurentian Great Lakes of North America have been dramatically altered by such invasions, especially zebra (Dreissena polymorpha and quagga (D. rostriformis bugensis mussels. Responses to mussel invasions have included increased water clarity, and decreased chlorophyll and phytoplankton abundance. Although not all systems have responded similarly, in general, mussels have changed nutrient dynamics and physical habitat conditions. Therefore examination of different impacts can help us further understand mechanisms that underlie ecosystem responses to biological invasions. To aid our understanding of ecosystem impacts, we sampled established locations along a well-studied trophic gradient in Green Bay, Lake Michigan, after the 1993 zebra mussel invasion. A strong trophic gradient remained during the period sampled after the mussel invasion (2000–2012. However, mean summer chlorophyll increased and other measures of phytoplankton biomass (microscope and electronic cell counting did not change significantly. Multivariate analyses of phytoplankton community structure demonstrate a significant community shift after the invasion. Cyanobacteria increased in dominance, with Microcystis becoming the major summer taxon in lower Green Bay. Diatom diversity and abundance also increased and Chlorophyta became rare. Phytoplankton responses along the trophic gradient of Green Bay to zebra mussel invasion highlight the importance of mussel effects on nutrient dynamics and phytoplankton diversity and function.

  13. Planetary Boundary Layer Dynamics over Reno, Nevada in Summer

    Science.gov (United States)

    Liming, A.; Sumlin, B.; Loria Salazar, S. M.; Holmes, H.; Arnott, W. P.

    2014-12-01

    Quantifying the height of the planetary boundary layer (PBL) is important to understand the transport behavior, mixing, and surface concentrations of air pollutants. In Reno, NV, located in complex, mountainous terrain with high desert climate, the daytime boundary layer can rise to an estimated 3km or more on a summer day due to surface heating and convection. The nocturnal boundary layer, conversely, tends to be much lower and highly stable due to radiative cooling from the surface at night and downslope flow of cool air from nearby mountains. With limited availability of radiosonde data, current estimates of the PBL height at any given time or location are potentially over or underestimated. To better quantify the height and characterize the PBL physics, we developed portable, lightweight sensors that measure CO2 concentrations, temperature, pressure, and humidity every 5 seconds. Four of these sensors are used on a tethered balloon system to monitor CO2 concentrations from the surface up to 300m. We will combine this data with Radio Acoustic Sounding System (RASS) data that measures vertical profiles of wind speed, temperature, and humidity from 40m to 400m. This experiment will characterize the diurnal evolution of CO2 concentrations at multiple heights in the PBL, provide insight into PBL physics during stability transition periods at sunrise and sunset, and estimate the nighttime PBL depth during August in Reno. Further, we expect to gain a better understanding of the impact of mixing volume changes (i.e., PBL height) on air quality and pollution concentrations in Reno. The custom portable sensor design will also be presented. It is expected that these instruments can be used for indoor or outdoor air quality studies, where lightness, small size, and battery operation can be of benefit.

  14. Impacts of sea ice retreat, thinning, and melt-pond proliferation on the summer phytoplankton bloom in the Chukchi Sea, Arctic Ocean

    Science.gov (United States)

    Palmer, Molly A.; Saenz, Benjamin T.; Arrigo, Kevin R.

    2014-07-01

    In 2011, a massive phytoplankton bloom was observed in the Chukchi Sea under first-year sea ice (FYI), an environment in which primary productivity (PP) has historically been low. In this paper, we use a 1-D biological model of the Chukchi shelf ecosystem, in conjunction with in situ chemical and physiological data, to better understand the conditions that facilitated the development of such an unprecedented bloom. In addition, to assess the effects of changing Arctic environmental conditions on net PP (NPP), we perform model runs with varying sea ice and snow thickness, timing of melt, melt ponds, and biological parameters. Results from model runs with conditions similar to 2011 indicate that first-year ice (FYI) with at least 10% melt pond coverage transmits sufficient light to support the growth of shade-adapted Arctic phytoplankton. Increasing pond fraction by 20% enhanced peak under-ice NPP by 26% and produced rates more comparable to those measured during the 2011 bloom, but there was no effect of further increasing pond fraction. One of the important consequences of large under-ice blooms is that they consume a substantial fraction of surface nutrients such that NPP is greatly diminished in the marginal ice zone (MIZ) following ice retreat, where NPP has historically been the highest. In contrast, in model runs with ultraviolet radiation and zooplankton grazers reduce peak open water NPP but have little impact on under-ice NPP, which has important implications for the relative proportion of NPP concentrated in pelagic vs. benthic food webs. Finally, the shift in the relative amount of NPP occurring in under-ice vs. open-water environments may affect total ecosystem productivity.

  15. Coastal Zone Color Scanner (CZCS): Imagery of near-surface phytoplankton pigment concentrations from the first coastal ocean dynamics experiment (CODE-1), March - July 1981

    Science.gov (United States)

    Abbott, M. R.; Zion, P. M.

    1984-01-01

    As part of the first Coastal Ocean Dynamics Experiment, images of ocean color were collected from late March until late July, 1981, by the Coastal Zone Color Scanner aboard Nimbus-7. Images that had sufficient cloud-free area to be of interest were processed to yield near-surface phytoplankton pigment concentrations. These images were then remapped to a fixed equal-area grid. This report contains photographs of the digital images and a brief description of the processing methods.

  16. Primary production, nutrient dynamics and mineralisation in a northeastern Greenland fjord during the summer thaw

    DEFF Research Database (Denmark)

    Rysgaard, S.; Finster, K.; Dahlgaard, H.

    1996-01-01

    This investigation represents the first integrated study of primary production, nutrient dynamics and mineralisation in a northeastern fjord of Greenland. The data presented represent conditions and activities during the early summer thaw (first 2 weeks of July). Primary production (5.3 mmol C m(...

  17. Positive and negative feedback loops in nutrient phytoplankton interactions related to climate dynamics factors in a shallow temperate estuary (Vistula Lagoon, southern Baltic)

    Science.gov (United States)

    Kruk, Marek; Kobos, Justyna; Nawrocka, Lidia; Parszuto, Katarzyna

    2018-04-01

    This study aims to demonstrate that factors associated with climate dynamics, such as temperature and wind, affect the ecosystem of the shallow Vistula Lagoon in the southern Baltic and cause nutrient forms phytoplankton interactions: the growth of biomass and constraints of it. This occurs through a network of direct and indirect relationships between environmental and phytoplankton factors, including interactions of positive and negative feedback loops. Path analysis supported by structural equation modeling (SEM) was used to test hypotheses regarding the impact of climate factors on algal assemblages. Increased phytoplankton biomass was affected directly by water temperature and salinity, while the wind speed effect was indirect as it resulted in increased concentrations of suspended solids (SS) in the water column. Simultaneously, the concentration of SS in the water was positively correlated with particulate organic carbon (POC), particulate nitrogen (PN), and particulate phosphorus (PP), and was negatively correlated with the total nitrogen to phosphorus (N:P) ratio. Particulate forms of C, N, and phosphorus (P), concentrations of soluble reactive phosphorus (SRP) and nitrate and nitrite nitrogen (NO3-N + NO2-N), and ratios of the total N:P and DIN:SRP, all indirectly effected Cyanobacteria C concentrations. These processes influence other phytoplankton groups (Chlorophyta, Bacillariophyceae and the picophytoplankton fraction). Increased levels of SRP associated with organic matter (POC), which stemmed from reduced DIN:SRP ratios, contributed to increased Cyanoprokaryota and picophytoplankton C concentrations, which created a positive feedback loop. However, a simultaneous reduction in the total N:P ratio could have inhibited increases in the biomass of these assemblages by limiting N, which likely formed a negative feedback loop. The study indicates that the nutrients-phytoplankton feedback loop phenomenon can intensify eutrophication in a temperate lagoon

  18. 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

  19. Unravel the submesoscale dynamics of the phytoplanktonic community in the NW Mediterranean Sea by in situ observations: the 2015 OSCAHR cruise

    Science.gov (United States)

    Marrec, Pierre; Doglioli, Andrea M.; Grégori, Gérald; Della Penna, Alice; Wagener, Thibaut; Rougier, Gille; Bhairy, Nagib; Dugenne, Mathilde; Lahbib, Soumaya; Thyssen, Melilotus

    2017-04-01

    Submesoscale phenomena have been recently recognized as a key factor in physical-biological-biogeochemical interactions, even if it remains unclear how these processes affect the global state of the ocean. Significant large-scale impacts of submesoscale structures on primary production and influence on the phytoplankton community structure and diversity have also been reported. In the past decade submesoscale dynamics have been predominately studied through the analysis of numerical simulations. Observing the coupled physical and biogeochemical variability at this scale remains challenging due to the ephemeral nature of submesoscale structures. The in-situ study of such structures necessitates multidisciplinary approaches involving in situ observations, remote sensing and modeling. Last progresses in biogeochemical sensor development and advanced methodology including Lagrangian real-time adaptative strategies represent outstanding opportunities. The OSCAHR (Observing Submesoscale Coupling At High Resolution) campaign has been conducted thanks to a multidisciplinary approach in order to improve the understanding of submesoscale processes. An ephemeral submesoscale structure was first identified in the Ligurian Sea in fall 2015 using both satellite and numerical modeling data before the campaign. Afterwards, advanced observing systems for the physical, biological and biogeochemical characterization of the sea surface layer at a high spatial and temporal frequency were deployed during a 10-days cruise. A MVP (Moving Vessel Profiler) was used to obtain high resolution CTD profiles associated to a new pumping system with 1-m vertical resolution. Moreover, along the ship track, in addition to the standard measurements of seawater surface samples (Chl-a, nutrients, O2, SST, SSS …), we deployed an automated flow cytometer for near real-time characterization of phytoplankton functional groups (from micro-phytoplankton down to cyanobacteria). The observed submesoscale

  20. Dynamic and thermodynamic impacts of the winter Arctic Oscillation on summer sea ice extent.

    Science.gov (United States)

    Park, H. S.; Stewart, A.

    2017-12-01

    Arctic summer sea ice extent exhibits substantial interannual variability, as is highlighted by the remarkable recovery in sea ice extent in 2013 following the record minimum in the summer of 2012. Here, we explore the mechanism via which Arctic Oscillation (AO)-induced ice thickness changes impact summer sea ice, using observations and reanalysis data. A positive AO weakens the basin-scale anticyclonic sea ice drift and decreases the winter ice thickness by 15cm and 10cm in the Eurasian and the Pacific sectors of the Arctic respectively. Three reanalysis datasets show that the (upward) surface heat fluxes are reduced over wide areas of the Arctic, suppressing the ice growth during the positive AO winters. The winter dynamic and thermodynamic thinning preconditions the ice for enhanced radiative forcing via the ice-albedo feedback in late spring-summer, leading to an additional 8-10 cm of thinning over the Pacific sector of the Arctic. Because of these winter AO-induced dynamic and thermodynamics effects, the winter AO explains about 22% (r = -0.48) of the interannual variance of September sea ice extent from year 1980 to 2015.

  1. Winter climate controls soil carbon dynamics during summer in boreal forests

    International Nuclear Information System (INIS)

    Haei, Mahsa; Öquist, Mats G; Ilstedt, Ulrik; Laudon, Hjalmar; Kreyling, Juergen

    2013-01-01

    Boreal forests, characterized by distinct winter seasons, store a large proportion of the global terrestrial carbon (C) pool. We studied summer soil C-dynamics in a boreal forest in northern Sweden using a seven-year experimental manipulation of soil frost. We found that winter soil climate conditions play a major role in controlling the dissolution/mineralization of soil organic-C in the following summer season. Intensified soil frost led to significantly higher concentrations of dissolved organic carbon (DOC). Intensified soil frost also led to higher rates of basal heterotrophic CO 2 production in surface soil samples. However, frost-induced decline in the in situ soil CO 2 concentrations in summer suggests a substantial decline in root and/or plant associated rhizosphere CO 2 production, which overrides the effects of increased heterotrophic CO 2 production. Thus, colder winter soils, as a result of reduced snow cover, can substantially alter C-dynamics in boreal forests by reducing summer soil CO 2 efflux, and increasing DOC losses. (letter)

  2. Seasonal phytoplankton blooms in the Gulf of Aden revealed by remote sensing

    KAUST Repository

    Gittings, John

    2016-11-25

    The Gulf of Aden, situated in the northwest Arabian Sea and linked to the Red Sea, is a relatively unexplored ecosystem. Understanding of large-scale biological dynamics is limited by the lack of adequate datasets. In this study, we analyse 15 years of remotely-sensed chlorophyll-a data (Chl-a, an index of phytoplankton biomass) acquired from the Ocean Colour Climate Change Initiative (OC-CCI) of the European Space Agency (ESA). The improved spatial coverage of OC-CCI data in the Gulf of Aden allows, for the first time, an investigation into the full seasonal succession of phytoplankton biomass. Analysis of indices of phytoplankton phenology (bloom timing) reveals distinct phytoplankton growth periods in different parts of the gulf: a large peak during August (mid-summer) in the western part of the gulf, and a smaller peak during November (mid-autumn) in the lower central gulf and along the southern coastline. The summer bloom develops rapidly at the beginning of July, and its peak is approximately three times higher than that of the autumnal bloom. Remotely-sensed sea-surface temperature (SST), wind-stress curl, vertical nutrient profiles and geostrophic currents inferred from the sea-level anomaly, were analysed to examine the underlying physical mechanisms that control phytoplankton growth. During summer, the prevailing southwesterlies cause upwelling along the northern coastline of the gulf (Yemen), leading to an increase in nutrient availability and enhancing phytoplankton growth along the coastline and in the western part of the gulf. In contrast, in the central region of the gulf, lowest concentrations of Chl-a are observed during summer, due to strong downwelling caused by a mesoscale anticyclonic eddy. During autumn, the prevailing northeasterlies enable upwelling along the southern coastline (Somalia) causing local nutrient enrichment in the euphotic zone, leading to higher levels of phytoplankton biomass along the coastline and in the lower central gulf

  3. A numerical investigation of phytoplankton and Pseudocalanus elongatus dynamics in the spring bloom time in the Gdańsk Gulf

    Science.gov (United States)

    Dzierzbicka-Głowacka, Lidia

    2005-01-01

    A nutrient-phytoplankton-zooplankton-detritus (1D-NPZD) `phytoplankton {Phyt} and Pseudocalanus elongatus {Zoop} dynamics in the spring bloom time in the Gdańsk Gulf. The 1D-NPZD model consists of three coupled, partial second-order differential equations of the diffusion type for phytoplankton {Phyt}, zooplankton {Zoop}, nutrients {Nutr} and one ordinary first-order differential equation for benthic detritus pool {Detr}, together with initial and boundary conditions. In this model, the {Zoop} is presented by only one species of copepod ( P. elongatus) and {Zoop} is composed of six cohorts of copepods with weights ( Wi) and numbers ( Zi); where Zoop= limit∑i=16W iZ i. The calculations were made for 90 days (March, April, May) for two stations at Gdańsk Gulf with a vertical space step of 0.5m and a time step of 900 s. The flow field and water temperature used as the inputs in the biological model 1D-NPZD were reproduced by the prognostic numerical simulation technique using hydrographic climatological data. The results of the numerical investigations described here were compared with the mean observed values of surface chlorophyll- a and depth integrated P. elongatus biomass for 10 years, 1980-1990. The slight differences between the calculated and mean observed values of surface chlorophyll- a and zooplankton biomass are ca. 10-60 mg C m -3 and ca. 5-23 mg C m -2, respectively, depending on the location of the hydrographic station. The 1D-NPZD model with a high-resolution zooplankton module for P. elongatus can be used to describe the temporal patterns for phytoplankton biomass and P. elongatus in the centre of the Gdańsk Gulf.

  4. Projected change in East Asian summer monsoon by dynamic downscaling: Moisture budget analysis

    Science.gov (United States)

    Jung, Chun-Yong; Shin, Ho-Jeong; Jang, Chan Joo; Kim, Hyung-Jin

    2015-02-01

    The summer monsoon considerably affects water resource and natural hazards including flood and drought in East Asia, one of the world's most densely populated area. In this study, we investigate future changes in summer precipitation over East Asia induced by global warming through dynamical downscaling with the Weather Research and Forecast model. We have selected a global model from the Coupled Model Intercomparison Project Phase 5 based on an objective evaluation for East Asian summer monsoon and applied its climate change under Representative Concentration Pathway 4.5 scenario to a pseudo global warming method. Unlike the previous studies that focused on a qualitative description of projected precipitation changes over East Asia, this study tried to identify the physical causes of the precipitation changes by analyzing a local moisture budget. Projected changes in precipitation over the eastern foothills area of Tibetan Plateau including Sichuan Basin and Yangtze River displayed a contrasting pattern: a decrease in its northern area and an increase in its southern area. A local moisture budget analysis indicated the precipitation increase over the southern area can be mainly attributed to an increase in horizontal wind convergence and surface evaporation. On the other hand, the precipitation decrease over the northern area can be largely explained by horizontal advection of dry air from the northern continent and by divergent wind flow. Regional changes in future precipitation in East Asia are likely to be attributed to different mechanisms which can be better resolved by regional dynamical downscaling.

  5. Joint effect of freshwater plume and coastal upwelling on phytoplankton growth off the Changjiang River

    Science.gov (United States)

    Tseng, Y.-F.; Lin, J.; Dai, M.; Kao, S.-J.

    2014-01-01

    The Changjiang (Yangtze) River discharges vast amount of unbalanced nutrients (dissolved inorganic nitrogen and phosphorus with N / P ratio > 80 in general) into the East China Sea in summer. To study nutrient dynamics and P-stress potential for phytoplankton, a cruise was conducted in the Changjiang plume during summer 2011. With 3-D observations of nutrients, chlorophyll a (Chl a), and bulk alkaline phosphatase activity (APA), we concluded that the Changjiang Diluted Water and coastal upwelling significantly influenced the horizontal and vertical heterogeneities of phytoplankton P deficiency in the Changjiang plume. Allochthonous APA was detected at nutrient-enriched freshwater end. Excessive N (~ 10 to 112 μM) was observed throughout the entire plume surface. In the plume fringe featuring stratification and excess N, diapycnal phosphate supply was blocked and phytoplankton APA was stimulated for growth. We observed an upwelling just attaching to the turbidity front at seaward side where Chl a peaked yet much less APA was detected. An external phosphate supply from subsurface, which promoted phytoplankton growth but inhibited APA, was suggested to be sourced from the Nearshore Kuroshio Branch Current. In the so hydrographically complicated Changjiang plume, phosphate supply instead of its concentration may be more important in determining the expression of APA. Meanwhile, allochthonous APA may also alter the usefulness of APA as a P-stress indicator.

  6. Size-dependent photoacclimation of the phytoplankton community in temperate shelf waters (southern Bay of Biscay)

    KAUST Repository

    Álvarez, E

    2015-12-09

    © Inter-Research 2016. Shelf waters of the Cantabrian Sea (southern Bay of Biscay) are productive ecosystems with a marked seasonality. We present the results from 1 yr of monthly monitoring of the phytoplankton community together with an intensive sampling carried out in 2 contrasting scenarios during the summer and autumn in a mid-shelf area. Stratification was apparent on the shelf in summer, while the water column was comparatively well mixed in autumn. The size structure of the photoautotrophic community, from pico-to micro-phytoplankton, was tightly coupled with the meteo-climatic and hydrographical conditions. Over the short term, variations in the size structure and chlorophyll content of phytoplankton cells were related to changes in the physico-chemical environment, through changes in the availability of nutrients and light. Uncoupling between the dynamics of carbon biomass and chlorophyll resulted in chlorophyll to carbon ratios dependent on body size. The slope of the size dependence of chlorophyll content increased with increasing irradiance, reflecting different photoacclimation plasticity from pico-to micro-phytoplankton. The results have important implications for the productivity and the fate of biogenic carbon in this region, since the size dependence of photosynthetic rates is directly related to the size scaling of chlorophyll content.

  7. Size-dependent photoacclimation of the phytoplankton community in temperate shelf waters (southern Bay of Biscay)

    KAUST Repository

    Á lvarez, E; Moran, Xose Anxelu G.; Ló pez-Urrutia, Á ; Nogueira, E

    2015-01-01

    © Inter-Research 2016. Shelf waters of the Cantabrian Sea (southern Bay of Biscay) are productive ecosystems with a marked seasonality. We present the results from 1 yr of monthly monitoring of the phytoplankton community together with an intensive sampling carried out in 2 contrasting scenarios during the summer and autumn in a mid-shelf area. Stratification was apparent on the shelf in summer, while the water column was comparatively well mixed in autumn. The size structure of the photoautotrophic community, from pico-to micro-phytoplankton, was tightly coupled with the meteo-climatic and hydrographical conditions. Over the short term, variations in the size structure and chlorophyll content of phytoplankton cells were related to changes in the physico-chemical environment, through changes in the availability of nutrients and light. Uncoupling between the dynamics of carbon biomass and chlorophyll resulted in chlorophyll to carbon ratios dependent on body size. The slope of the size dependence of chlorophyll content increased with increasing irradiance, reflecting different photoacclimation plasticity from pico-to micro-phytoplankton. The results have important implications for the productivity and the fate of biogenic carbon in this region, since the size dependence of photosynthetic rates is directly related to the size scaling of chlorophyll content.

  8. Phytoplankton bloom dynamics in coastal ecosystems: A review with some general lessons from sustained investigation of San Francisco Bay, California

    Science.gov (United States)

    Cloern, James E.

    1996-05-01

    Phytoplankton blooms are prominent features of biological variability in shallow coastal ecosystems such as estuaries, lagoons, bays, and tidal rivers. Long-term observation and research in San Francisco Bay illustrates some patterns of phytoplankton spatial and temporal variability and the underlying mechanisms of this variability. Blooms are events of rapid production and accumulation of phytoplankton biomass that are usually responses to changing physical forcings originating in the coastal ocean (e.g., tides), the atmosphere (wind), or on the land surface (precipitation and river runoff). These physical forcings have different timescales of variability, so algal blooms can be short-term episodic events, recurrent seasonal phenomena, or rare events associated with exceptional climatic or hydrologic conditions. The biogeochemical role of phytoplankton primary production is to transform and incorporate reactive inorganic elements into organic forms, and these transformations are rapid and lead to measurable geochemical change during blooms. Examples include the depletion of inorganic nutrients (N, P, Si), supersaturation of oxygen and removal of carbon dioxide, shifts in the isotopic composition of reactive elements (C, N), production of climatically active trace gases (methyl bromide, dimethylsulfide), changes in the chemical form and toxicity of trace metals (As, Cd, Ni, Zn), changes in the biochemical composition and reactivity of the suspended particulate matter, and synthesis of organic matter required for the reproduction and growth of heterotrophs, including bacteria, zooplankton, and benthic consumer animals. Some classes of phytoplankton play special roles in the cycling of elements or synthesis of specific organic molecules, but we have only rudimentary understanding of the forces that select for and promote blooms of these species. Mounting evidence suggests that the natural cycles of bloom variability are being altered on a global scale by human

  9. Contrasts between channels and backwaters in a large, floodplain river: Testing our understanding of nutrient cycling, phytoplankton abundance, and suspended solids dynamics

    Science.gov (United States)

    Houser, Jeff N.

    2016-01-01

    In floodplain rivers, variability in hydraulic connectivity interacts with biogeochemistry to determine the distribution of suspended and dissolved substances. Nutrient, chlorophyll a, and suspended solids data spanning longitudinal (5 study reaches across 1300 river km), lateral (main channel and backwaters), and temporal (1994–2011) gradients in the Upper Mississippi River (UMR) were used to examine the extent to which observed differences between the main channel and backwaters were consistent with expectations based on current understanding of biogeochemical processes in large rivers. For N and P, the results largely conformed to expectations. N concentrations were greater in the main channel than in the backwaters in 82 to 96% of the observations across river reaches. Maximum TP concentrations generally occurred in backwaters during summer, when backwater TP often exceeded that of the main channel. Flux of P from sediments may be a substantial source of water-column P in UMR backwaters in summer. The data for suspended solids and chlorophyll a suggest that some refinements are needed of our understanding of ecosystem processes in large rivers. During low-discharge conditions, concentrations of inorganic suspended solids often were greater in backwaters than in the main channel, suggesting the importance of sediment resuspension. Chlorophyll a concentrations were usually greater in backwaters than in the main channel, but exceptions indicate that phytoplankton abundance in the main channel of the UMR can sometimes be greater than is typically expected for large rivers.

  10. Summer and Winter Effect of Innovative Cool Roof Tiles on the Dynamic Thermal Behavior of Buildings

    Directory of Open Access Journals (Sweden)

    Anna Laura Pisello

    2014-04-01

    Full Text Available Cool roofs represent an acknowledged passive cooling technique to reduce building energy consumption for cooling and to mitigate urban heat island effects. This paper concerns the evaluation of the dynamic effect of new cool roof clay tiles on building thermal performance in summer and winter conditions. To this end, these properties have been analyzed on traditional roof brick tiles through an indoor and outdoor two-year long continuous monitoring campaign set up in a residential building located in central Italy. The analysis and the cooperation with industrial companies producing brick tiles and reflective coatings allowed the production of a new tile with notable “cool roof” properties through the traditional industrial manufacturing path of such tiles. Notable results show that during summer the high reflection tiles are able to decrease the average external roof surface temperature by more than 10 °C and the indoor operative temperature by more than 3 °C. During winter the average external surface temperature is lower with high reflection tiles by about 1 °C. Singular optic-thermal phenomena are registered while evaluating the dynamics of the cool roof effect. Interesting findings show how the sloped cool roof application could suggest further considerations about the dynamic effect of cool roofs.

  11. Climatic change of summer temperature and precipitation in the Alpine region - a statistical-dynamical assessment

    Energy Technology Data Exchange (ETDEWEB)

    Heimann, D.; Sept, V.

    1998-12-01

    Climatic changes in the Alpine region due to increasing greenhouse gas concentrations are assessed by using statistical-dynamical downscaling. The downscaling procedure is applied to two 30-year periods (1971-2000 and 2071-2100, summer months only) of the output of a transient coupled ocean/atmosphere climate scenario simulation. The downscaling results for the present-day climate are in sufficient agreement with observations. The estimated regional climate change during the next 100 years shows a general warming. The mean summer temperatures increase by about 3 to more than 5 Kelvin. The most intense climatic warming is predicted in the western parts of the Alps. The amount of summer precipitation decreases in most parts of central Europe by more than 20 percent. Only over the Adriatic area and parts of eastern central Europe an increase in precipitation is simulated. The results are compared with observed trends and results of regional climate change simulations of other authors. The observed trends and the majority of the simulated trends agree with our results. However, there are also climate change estimates which completely contradict with ours. (orig.) 29 refs.

  12. Par Pond phytoplankton in association with refilling of the pond: Final Report for sampling from February 1995 -- September 1996

    International Nuclear Information System (INIS)

    Wilde, E.W.; Johnson, M.A.; Cody, W.C.

    1996-01-01

    This report describes the results of phytoplankton analyses from Par Pond samples collected between February 1995 and September 1996. The principal objective of the study was to determine the effect of refilling of Par Pond following repair of the dam on the phytoplankton community. Algal blooms are often responsible for fish kills and other detrimental effects in ponds and lakes, and it was postulated that decaying vegetation from formerly exposed sediments might trigger algal blooms that could result in fish kills in Par Pond following the refill. Sporadic algal blooms involving blue-green algae were detected, especially during the summer of 1996. However, the data derived from the study demonstrates that overall, the refilling effort caused no significant negative impact to the pond attributable to phytoplankton dynamics

  13. Par Pond phytoplankton in association with refilling of the pond: Final Report for sampling from February 1995 -- September 1996

    Energy Technology Data Exchange (ETDEWEB)

    Wilde, E.W.; Johnson, M.A.; Cody, W.C.

    1996-12-31

    This report describes the results of phytoplankton analyses from Par Pond samples collected between February 1995 and September 1996. The principal objective of the study was to determine the effect of refilling of Par Pond following repair of the dam on the phytoplankton community. Algal blooms are often responsible for fish kills and other detrimental effects in ponds and lakes, and it was postulated that decaying vegetation from formerly exposed sediments might trigger algal blooms that could result in fish kills in Par Pond following the refill. Sporadic algal blooms involving blue-green algae were detected, especially during the summer of 1996. However, the data derived from the study demonstrates that overall, the refilling effort caused no significant negative impact to the pond attributable to phytoplankton dynamics.

  14. Dynamics of microbial biomass and respiratory activity during late summer in a site of Arctic Kongsfjorden

    Directory of Open Access Journals (Sweden)

    Rosabruna La Ferla

    2014-06-01

    The Kongsfjorden was affected by inflow of Atlantic water as well as glacier melt water runoff (Cottier et al., 2005. The experiment comprised 5 samplings performed during a 7 day period in MDI station. For each sampling, photosynthetically active radiation (PAR, temperature and conductivity (salinity were recorded along the water column with a PNF-300 profiler and a SeaBird Electronics SBE-911 plus profiler, respectively . Water samples were taken at five different depths (surface, 5, 25, 50 and 100 m to determine nutrients, particulate organic carbon, prokaryotes and phytoplankton biomass, and community respiration. In addition, prokaryotes sunk with the particulate matter were studied into the sediment trap positioned in the MDI during the period between June and September 2013. The latter assessment allowed us to determine the flow of prokaryotes, conveyed from organic matter sinking, throughout the summer. Due to melting of the glaciers in the surface water of the study site, there were sediment loads which strongly limited light penetration and low irradiance (~0.7% E0+ at 5 meters below the surface. Along the water column the intrusion of the salty and warm Atlantic water was visible in the study site and the warm core was at about 25 m depth. PO4 concentrations ranged between 0.43 (surface and 1 µM (100 m and in general the values increased from surface to bottom. NH4, NO2 and NO3 significantly changed along the vertical and with time and varied between 0.39 and 5.05µM, 0.01 and 0.67µM, 0.001 and 4.18µM, respectively. Prokaryotic abundances and cell volumes ranged between 5.6 and 15.9 E+05 cells ml-1 and 0.033 and 0.093 µm3, respectively. These latter parameters showed a peak at 25 m depth in the core of incoming Atlantic water. This evidence was not determined in chlorophyll a (range 0.034-1.102 mg m-3, where the highest values were determined at the surface and 5 m depth. Speculations will be made on the variability of the fluxes of carbon

  15. Phytoplankton response to a plume front in the northern South China Sea

    Science.gov (United States)

    Li, Qian P.; Zhou, Weiwen; Chen, Yinchao; Wu, Zhengchao

    2018-04-01

    Due to a strong river discharge during April-June 2016, a persistent salinity front, with freshwater flushing seaward on the surface but seawater moving landward at the bottom, was formed in the coastal waters west of the Pearl River estuary (PRE) over the northern South China Sea (NSCS) shelf. Hydrographic measurements revealed that the salinity front was influenced by both the river plume and coastal upwelling. On shipboard nutrient-enrichment experiments with size-fractionation chlorophyll a measurements were taken on both sides of the front as well as in the frontal zone to diagnose the spatial variations of phytoplankton physiology across the frontal system. We also assessed the size-fractionated responses of phytoplankton to the treatment of plume water at the frontal zone and the sea side of the front. The biological impact of vertical mixing or upwelling was further examined by the response of surface phytoplankton to the addition of local bottom water. Our results suggested that there was a large variation in phytoplankton physiology on the sea side of the front, driven by dynamic nutrient fluxes, although P limitation was prevailing on the shore side of the front and at the frontal zone. The spreading of plume water at the frontal zone would directly improve the growth of microphytoplankton, while nano- and picophytoplankton growths could have become saturated at high percentages of plume water. Also, the mixing of bottom water would stimulate the growth of surface phytoplankton on both sides of the front by altering the surface N/P ratio to make it closer to the Redfield stoichiometry. In summary, phytoplankton growth and physiology could be profoundly influenced by the physical dynamics in the frontal system during the spring-summer of 2016.

  16. Decreased summer drought affects plant productivity and soil carbon dynamics in a Mediterranean woodland

    Science.gov (United States)

    Cotrufo, M. F.; Alberti, G.; Inglima, I.; Marjanović, H.; Lecain, D.; Zaldei, A.; Peressotti, A.; Miglietta, F.

    2011-09-01

    Precipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP) and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR). Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 58 % and 220 %, respectively, as compared to the control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction in precipitation) did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction) in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodlands. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long-term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long-term soil C stocks.

  17. Decreased summer drought affects plant productivity and soil carbon dynamics in a Mediterranean woodland

    Directory of Open Access Journals (Sweden)

    M. F. Cotrufo

    2011-09-01

    Full Text Available Precipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR. Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 58 % and 220 %, respectively, as compared to the control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction in precipitation did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodlands. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long-term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long-term soil C stocks.

  18. Decreased summer drought affects plant productivity and soil carbon dynamics in Mediterranean woodland

    Science.gov (United States)

    Cotrufo, M. F.; Alberti, G.; Inglima, I.; Marjanović, H.; Lecain, D.; Zaldei, A.; Peressotti, A.; Miglietta, F.

    2011-06-01

    Precipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP) and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR). Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. The throughfall manipulation experiment started in 2004 and we report data up to the 2009 growing season. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 50 % and 220 %, respectively, as compared to control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction of precipitation) did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction) in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodland. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long term soil C stocks.

  19. Dynamics of sea-ice biogeochemistry in the coastal Antarctica during transition from summer to winter

    Directory of Open Access Journals (Sweden)

    Suhas Shetye

    2017-05-01

    Full Text Available The seasonality of carbon dioxide partial pressure (pCO2, air-sea CO2 fluxes and associated environmental parameters were investigated in the Antarctic coastal waters. The in-situ survey was carried out from the austral summer till the onset of winter (January 2012, February 2010 and March 2009 in the Enderby Basin. Rapid decrease in pCO2 was evident under the sea-ice cover in January, when both water column and sea-ice algal activity resulted in the removal of nutrients and dissolved inorganic carbon (DIC and increase in pH. The major highlight of this study is the shift in the dominant biogeochemical factors from summer to early winter. Nutrient limitation (low Si/N, sea-ice cover, low photosynthetically active radiation (PAR, deep mixed layer and high upwelling velocity contributed towards higher pCO2 during March (early winter. CO2 fluxes suggest that the Enderby Basin acts as a strong CO2 sink during January (−81 mmol m−2 d−1, however it acts as a weak sink of CO2 with −2.4 and −1.7 mmol m−2 d−1 during February and March, respectively. The present work, concludes that sea ice plays a dual role towards climate change, by decreasing sea surface pCO2 in summer and enhancing in early winter. Our observations emphasize the need to address seasonal sea-ice driven CO2 flux dynamics in assessing Antarctic contributions to the global oceanic CO2 budget.

  20. Deep winter convection and phytoplankton dynamics in the NW Mediterranean Sea under present climate and future (horizon 2030) scenarios.

    Science.gov (United States)

    Macias, Diego; Garcia-Gorriz, Elisa; Stips, Adolf

    2018-04-26

    Deep water convection (DC) in winter is one of the major processes driving open-ocean primary productivity in the Northwestern Mediterranean Sea. DC is highly variable in time, depending on the specific conditions (stratification, circulation and ocean-atmosphere interactions) of each specific winter. This variability also drives the interannual oscillations of open-ocean primary productivity in this important region for many commercially-important fish species. We use a coupled model system to 1) understand to what extent DC impacts phytoplankton seasonality in the present-day and 2) to explore potential changes in future scenarios (~2030). Our model represents quite accurately the present-day characteristics of DC and its importance for open-ocean phytoplankton blooms. However, for the future scenarios the importance of deep nutrients in fertilizing the euphotic layer of the NW Mediterranean decreases. The model simulates changes in surface density and on the levels of kinetic energy that make mesoscale activity associated with horizontal currents to become a more important fertilization mechanism, inducing subsequently phenological changes in seasonal plankton cycles. Because of our focus on the open-sea, an exact quantification of the impact of those changes on the overall biological production of the NW Mediterranean cannot be made at the moment.

  1. Increasing phytoplankton-available phosphorus and inhibition of macrophyte on phytoplankton bloom.

    Science.gov (United States)

    Dai, Yanran; Wu, Juan; Ma, Xiaohang; Zhong, Fei; Cui, Naxin; Cheng, Shuiping

    2017-02-01

    We assembled mesocosms to address the coherent mechanisms that an increasing phosphorus (P) concentration in water columns coupled with the phytoplankton bloom and identify the performance gap of regulating phytoplankton growth between two macrophyte species, Ceratophyllum demersum L. and Vallisneria spiralis L. Intense alkaline phosphatase activities (APA) were observed in the unplanted control, with their predominant part, phytoplankton APA (accounting for up to 44.7% of the total APA), and another large share, bacterial APA. These correspond with the large average concentration of total phosphorus (TP), total dissolved phosphorus (TDP) and soluble reactive (SRP) as well as high phytoplankton density in the water column. The consistency among P concentrations, phytoplankton density and APA, together with the positive impact of phytoplankton density on total APA revealed by the structural equation modelling (SEM), indicates that facilitated APA levels in water is an essential strategy for phytoplankton to enhance the available P. Furthermore, a positive interaction between phytoplankton APA and bacteria APA was detected, suggesting a potential collaboration between phytoplankton and bacteria to boost available P content in the water column. Both macrophyte species had a prominent performance on regulating phytoplankton proliferation. The phytoplankton density and quantum yield in C. demersum systems were all significantly lower (33.8% and 24.0%) than those in V. spiralis systems. Additionally, a greater decoupling effect of C. demersum on the relationship between P, APA, phytoplankton density, bacteria dynamic and quantum yield was revealed by SEM. These results imply that the preferred tactic of different species could lead to the performance gap. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Atmospheric Dynamics Leading to West European Summer Hot Temperatures Since 1851

    Directory of Open Access Journals (Sweden)

    M. Carmen Alvarez-Castro

    2018-01-01

    Full Text Available Summer hot temperatures have many impacts on health, economy (agriculture, energy, and transports, and ecosystems. In Western Europe, the recent summers of 2003 and 2015 were exceptionally warm. Many studies have shown that the genesis of the major heat events of the last decades was linked to anticyclonic atmospheric circulation and to spring precipitation deficit in Southern Europe. Such results were obtained for the second part of the 20th century and projections into the 21st century. In this paper, we challenge this vision by investigating the earlier part of the 20th century from an ensemble of 20CR reanalyses. We propose an innovative description of Western-European heat events applying the dynamical system theory. We argue that the atmospheric circulation patterns leading to the most intense heat events have changed during the last century. We also show that the increasing temperature trend during major heatwaves is encountered during episodes of Scandinavian Blocking, while other circulation patterns do not yield temperature trends during extremes.

  3. Frontal dynamics boost primary production in the summer stratified Mediterranean sea

    Science.gov (United States)

    Olita, Antonio; Capet, Arthur; Claret, Mariona; Mahadevan, Amala; Poulain, Pierre Marie; Ribotti, Alberto; Ruiz, Simón; Tintoré, Joaquín; Tovar-Sánchez, Antonio; Pascual, Ananda

    2017-06-01

    Bio-physical glider measurements from a unique process-oriented experiment in the Eastern Alboran Sea (AlborEx) allowed us to observe the distribution of the deep chlorophyll maximum (DCM) across an intense density front, with a resolution (˜ 400 m) suitable for investigating sub-mesoscale dynamics. This front, at the interface between Atlantic and Mediterranean waters, had a sharp density gradient (Δ ρ ˜ 1 kg/m3 in ˜ 10 km) and showed imprints of (sub-)mesoscale phenomena on tracer distributions. Specifically, the chlorophyll-a concentration within the DCM showed a disrupted pattern along isopycnal surfaces, with patches bearing a relationship to the stratification (buoyancy frequency) at depths between 30 and 60 m. In order to estimate the primary production (PP) rate within the chlorophyll patches observed at the sub-surface, we applied the Morel and Andrè (J Geophys Res 96:685-698 1991) bio-optical model using the photosynthetic active radiation (PAR) from Argo profiles collected simultaneously with glider data. The highest production was located concurrently with domed isopycnals on the fresh side of the front, suggestive that (sub-)mesoscale upwelling is carrying phytoplankton patches from less to more illuminated levels, with a contemporaneous delivering of nutrients. Integrated estimations of PP (1.3 g C m-2d-1) along the glider path are two to four times larger than the estimations obtained from satellite-based algorithms, i.e., derived from the 8-day composite fields extracted over the glider trip path. Despite the differences in spatial and temporal sampling between instruments, the differences in PP estimations are mainly due to the inability of the satellite to measure DCM patches responsible for the high production. The deepest (depth > 60 m) chlorophyll patches are almost unproductive and probably transported passively (subducted) from upper productive layers. Finally, the relationship between primary production and oxygen is also investigated

  4. The design of a dynamic security system at the XXIII Summer Olympics at Los Angeles

    International Nuclear Information System (INIS)

    Bruckner, D.G.

    1985-01-01

    The security requirements of the XXIII Summer Olympic Games at Los Angeles provided a challenge unparalleled in the history of the modern games. This paper discusses the dynamics involved and suggests that the principles used are applicable to many of today's security environments. The success of the Intrusion Detection Systems (IDS) employed at each of the three Olympic villages and at the Piper Technical Center is a known fact. How it was accomplished is addressed in a straightforward, systematic way. The paper also recognizes the contributions made by the security community, law enforcement agencies, the government, military, the security industry and RandD organizations. It was a team effort that reflected the spirit of the games and the American ''can-do'' attitude

  5. Phytoplankton of the Boguchany reservoir in 2016-2017 at the stations in front of the hydroelectric dam

    Directory of Open Access Journals (Sweden)

    M. V. Usoltseva

    2017-12-01

    Full Text Available The species structure and seasonal dynamics of the phytoplankton of the dam area of the Boguchany Reservoir were studied in the first years of operation of the hydroelectric power station in 2016-2017. Two peaks of algal bloom are noted in spring and summer. Mass species were: diatom Stephanodiscus minutulus and dinophyte Gymnodinium baicalense in spring; diatoms Asterionella formosa and Fragilaria crotonensis, blue-green Dolichospermum lemmermannii, D. flosaquae, D. flosaquae f. spiroides and Aphanizomenon flosaquae; green Sphaerocystis planctonica and dinophyte Ceratium hirundinella in summer; diatoms F. crotonensis and A. formosa, cryptophytic Rhodomonas pusilla and Cryptomonas ovata in autumn. The cryptophyte R. pusilla and the Cryptomonas species were dominated under the ice. The maximum number of phytoplankton (9 million cells in liter was recorded in the spring. According to the indixes of saprobity, the purity of water corresponded to II-III quality classes (pure and moderately polluted water.

  6. Environmental biogeography of near-surface phytoplankton in the southeast Pacific Ocean

    Science.gov (United States)

    Hardy, John; Hanneman, Andrew; Behrenfeldt, Michael; Horner, Rita

    1996-10-01

    Biogeographic interpretation of large-scale phytoplankton distribution patterns in relation to surface hydrography is essential to understanding pelagic food web dynamics and biogeochemical processes influencing global climate. We examined the abundance and biomass of phytoplankton in relation to physical and chemical parameters in the southeast Pacific Ocean. Samples were collected along longitude 110°W, between 10°N and 60°S during late austral summer. Patterns of taxa abundance and hydrographic variables were interpreted by principal components analysis. Five distinct phytohydrographic regions were identified: (i) a north equatorial region of moderate productivity dominated by small flagellates, low nitrate and low-to-moderate pCO 2; (ii) a south equatorial region characterized by high primary productivity dominated by diatoms, high nutrient levels, and relatively high pCO 2; (iii) a central gyre region characterized by low productivity dominated by small flagellates, low nitrate, and high pCO 2; (iv) a sub-Antarctic region with moderate productivity dominated by coccolithophores, moderate nitrate concentrations, and low pCO 2; and (v) an Antarctic region with high productivity dominated by diatoms, very high nitrate, and low pCO 2. Productivity and average phytoplankton cell size were positively correlated with nitrate concentration. Total phytoplankton abundance was negatively correlated with pCO 2, photosynthetically active radiation, and ultraviolet-B radiation. The interaction between phytoplankton carbon assimilation, atmospheric CO2, and the inhibitory effect of ultraviolet radiation could have implications for the global climate. These data suggest that the effects would be greatest at southern mid-latitudes (40-50°S) where present phytoplankton production and predicted future increases in UV-B are both relatively high.

  7. Impacts of an uncontrolled phosphogypsum dumpsite on summer distribution of phytoplankton, copepods and ciliates in relation to abiotic variables along the near-shore of the southwestern Mediterranean coast

    International Nuclear Information System (INIS)

    Rekik, Amira; Drira, Zaher; Guermazi, Wassim; Elloumi, Jannet; Maalej, Sami; Aleya, Lotfi; Ayadi, Habib

    2012-01-01

    In connection with the Taparura Project, studies of spatial distribution of the crustacean zooplankton community, nutrients, phytoplankton and ciliates were conducted in July 2007 at 45 stations spread over fifteen transects along the coast north of Sfax. The results showed that the N/P ratio was lower than the Redfield ratio, suggesting potential N limitation. Phytoplankton was characterised by the proliferation of several diatoms, while ciliates were largely dominated by spirotrichs. Copepods were the most abundant zooplankton present during the entire study period, comprising 61% of the total zooplankton community. Twelve copepod families were identified at every station, with a high percentage of Oithonidae (77% of copepods) dominated by Oithona nana. The abundance of this species was correlated with that of diatoms, Cocoolithophorideae and ciliated Colpodea, suggesting that O. nana may feed on a wide range of prey. Despite human pressure and industrial activities, the coastal waters north of Sfax showed a wide diversity of phytoplankton, ciliates and zooplankton.

  8. Short-term recurrent chaos and role of Toxin Producing Phytoplankton (TPP) on chaotic dynamics in aquatic systems

    International Nuclear Information System (INIS)

    Upadhyay, Ranjit Kumar; Rao, V. Sree Hari

    2009-01-01

    We propose a new mathematical model for aquatic populations. This model incorporates mutual interference in all the three populations and an extra mortality term in zooplankton population and also taking into account the toxin liberation process of TPP population. The proposed model generalizes several other known models in the literature. The principal interest in this paper is in a numerical study of the model's behaviour. It is observed that both types of food chains display same type of chaotic behaviour, short-term recurrent chaos, with different generating mechanisms. Toxin producing phytoplankton (TPP) reduces the grazing pressure of zooplankton. To observe the role of TPP, we consider Holling types I, II and III functional forms for this process. Our study suggests that toxic substances released by TPP population may act as bio-control by changing the state of chaos to order and extinction.

  9. Seasonal dynamics of plankton communities coupled with ...

    African Journals Online (AJOL)

    In this study, we studied the influence of the physical-chemical and biological factors (bacterioplankton and phytoplankton abundances) for zooplankton dynamics in a Sidi Saâd reservoir in Centre of Tunisia. The samplings were carried out in spring, summer, autumn and winter (2005 to 2006) in the deepest station (surface ...

  10. The contribution of phytoplankton degradation to chromophoric dissolved organic matter (CDOM) in eutrophic shallow lakes: field and experimental evidence.

    Science.gov (United States)

    Zhang, Yunlin; van Dijk, Mark A; Liu, Mingliang; Zhu, Guangwei; Qin, Boqiang

    2009-10-01

    Eight field campaigns in the eutrophic, shallow, Lake Taihu in the summers from 2005 to 2007, and a phytoplankton degradation experiment of 33 days, were carried out to determine the contribution of phytoplankton degradation to CDOM. Significant and positive correlations were found between the CDOM absorption coefficient at 355 nm [a(CDOM)(355)], normalized fluorescence emission (QSU) at 450 nm from excitation at 355 nm [F(n)(355)], and the chlorophyll a (Chla) concentration for all eight field campaigns, which indicates that the decomposition and degradation of phytoplankton is an important source of CDOM. In the degradation experiment, the CDOM absorption coefficient increased as phytoplankton broke down during the first 12 days, showing the production of CDOM from phytoplankton. After 12 days, a(CDOM)(355) had increased from the initial value 0.41+/-0.03 m(-1) to 1.37+/-0.03 m(-1) (a 234% increase), and the Chla concentration decreased from the initial value of 349.1+/-11.2 microg/L to 30.4+/-13.2 microg/L (a 91.3% decrease). The mean daily production rate of CDOM from phytoplankton was 0.08 m(-1) for a(CDOM)(355). Parallel Factor Analysis (PARAFAC) was used to assess CDOM composition from EEM spectra, and four components were identified: a terrestrial-like humic component, two marine-like humic components, and a protein-like component. The rapid increase in marine-like humic fluorophores (C3 and C4) during the degradation experiment suggests that in situ production of CDOM plays an important role in the dynamics of CDOM. The field campaigns and experimental data in the present study show that phytoplankton can be one of the important CDOM producers in eutrophic shallow lakes.

  11. Comparative summer dynamics of surface cyanobacterial communities in two connected lakes from the west of Ireland

    Energy Technology Data Exchange (ETDEWEB)

    Touzet, N., E-mail: touzet.nicolas@itsligo.ie [Centre for Environmental Research, Innovation and Sustainability, School of Science, Department of Environmental Science, Institute of Technology Sligo, Sligo (Ireland); McCarthy, D.; Gill, A.; Fleming, G.T.A. [Microbiology, School of Natural Sciences, National University of Ireland, Galway, Galway (Ireland)

    2016-05-15

    The eutrophication of lakes is typically associated with high biomass proliferations of potentially toxic cyanobacteria. At a regional level, the sustainable management of water resources necessitates an approach that recognises the interconnectivity of multiple water systems within river catchments. This study examined the dynamics in summer diversity of planktonic cyanobacterial communities and microcystin toxin concentrations in two inter-connected lakes from the west of Ireland prone to nutrient enrichment. DGGE analysis of 16S rRNA gene amplicons of genotype-I cyanobacteria (typically spherical) showed changes in the communities of both Lough Corrib and Ballyquirke Lough throughout the summer, and identified cyanobacterial genotypes both unique and shared to both lakes. Microcystin concentrations, estimated via the protein phosphatase 2A inhibition assay, were greater in August than in July and June in both lakes. This was concomitant to the increased occurrence of Microcystis as evidenced by DGGE band excision and subsequent sequencing and BLAST analysis. RFLP analysis of PCR amplified mcy-A/E genes clustered together the August samples of both lakes, highlighting a potential change in microcystin producers across the two lakes. Finally, the multiple factor analysis of the combined environmental data set for the two lakes highlighted the expected pattern opposing greater water temperature and chlorophyll concentration against macronutrient concentrations, but also indicated a negative relationship between microcystin concentration and cyanobacterial diversity, possibly underlining allelopathic interactions. Despite some element of connectivity, the dissimilarity in the composition of the cyanobacterial assemblages and the timing of community change in the two lakes likely were a reflexion of niche differences determined by meteorologically-forced variation in physico-chemical parameters in the two water bodies. - Highlights: • DGGE highlighted

  12. Comparative summer dynamics of surface cyanobacterial communities in two connected lakes from the west of Ireland

    International Nuclear Information System (INIS)

    Touzet, N.; McCarthy, D.; Gill, A.; Fleming, G.T.A.

    2016-01-01

    The eutrophication of lakes is typically associated with high biomass proliferations of potentially toxic cyanobacteria. At a regional level, the sustainable management of water resources necessitates an approach that recognises the interconnectivity of multiple water systems within river catchments. This study examined the dynamics in summer diversity of planktonic cyanobacterial communities and microcystin toxin concentrations in two inter-connected lakes from the west of Ireland prone to nutrient enrichment. DGGE analysis of 16S rRNA gene amplicons of genotype-I cyanobacteria (typically spherical) showed changes in the communities of both Lough Corrib and Ballyquirke Lough throughout the summer, and identified cyanobacterial genotypes both unique and shared to both lakes. Microcystin concentrations, estimated via the protein phosphatase 2A inhibition assay, were greater in August than in July and June in both lakes. This was concomitant to the increased occurrence of Microcystis as evidenced by DGGE band excision and subsequent sequencing and BLAST analysis. RFLP analysis of PCR amplified mcy-A/E genes clustered together the August samples of both lakes, highlighting a potential change in microcystin producers across the two lakes. Finally, the multiple factor analysis of the combined environmental data set for the two lakes highlighted the expected pattern opposing greater water temperature and chlorophyll concentration against macronutrient concentrations, but also indicated a negative relationship between microcystin concentration and cyanobacterial diversity, possibly underlining allelopathic interactions. Despite some element of connectivity, the dissimilarity in the composition of the cyanobacterial assemblages and the timing of community change in the two lakes likely were a reflexion of niche differences determined by meteorologically-forced variation in physico-chemical parameters in the two water bodies. - Highlights: • DGGE highlighted

  13. Is the future blue-green or brown? The effects of extreme events on phytoplankton dynamics in a semi-arid man-made lake

    NARCIS (Netherlands)

    Meideiros, L.D.C.; Mattos, A.; Lurling, M.F.L.L.W.; Becker, V.

    2015-01-01

    In arid and semi-arid regions, a hydrological regime characterized by an annual cycle of drought and rainy seasons changes the volume and retention time of reservoirs. Such changes affect the limnological characteristics and lead to changes on phytoplankton community. Phytoplankton seasonal

  14. The Indian summer monsoon rainfall: interplay of coupled dynamics, radiation and cloud microphysics

    Directory of Open Access Journals (Sweden)

    P. K. Patra

    2005-01-01

    Full Text Available The Indian summer monsoon rainfall (ISMR, which has a strong connection to agricultural food production, has been less predictable by conventional models in recent times. Two distinct years 2002 and 2003 with lower and higher July rainfall, respectively, are selected to help understand the natural and anthropogenic influences on ISMR. We show that heating gradients along the meridional monsoon circulation are reduced due to aerosol radiative forcing and the Indian Ocean Dipole in 2002. An increase in the dust and biomass-burning component of the aerosols through the zonal monsoon circulation resulted in reduction of cloud droplet growth in July 2002. These conditions were opposite to those in July 2003 which led to an above average ISMR. In this study, we have utilized NCEP/NCAR reanalyses for meteorological data (e.g. sea-surface temperature, horizontal winds, and precipitable water, NOAA interpolated outgoing long-wave radiation, IITM constructed all-India rainfall amounts, aerosol parameters as observed from the TOMS and MODIS satellites, and ATSR fire count maps. Based on this analysis, we suggest that monsoon rainfall prediction models should include synoptic as well as interannual variability in both atmospheric dynamics and chemical composition.

  15. Kaolin modulates ABA and IAA dynamics and physiology of grapevine under Mediterranean summer stress.

    Science.gov (United States)

    Dinis, L-T; Bernardo, S; Luzio, A; Pinto, G; Meijón, M; Pintó-Marijuan, M; Cotado, A; Correia, C; Moutinho-Pereira, J

    2018-01-01

    The foliar exogenous application of kaolin, a radiation-reflecting inert mineral, has proven to be an effective short-term climate change mitigation strategy for Mediterranean vineyards. In this work, we address the hypothesis that kaolin could improve both the hormonal dynamics and physiological responses of grapevines growing in Douro Region, northern Portugal. For this purpose, the leaf water potential, gas exchange and chlorophyll a fluorescence parameters were monitored, as well as the abscisic acid (ABA) and indole-3-acetic acid (IAA) quantification and immunolocalization were assessed. The study revealed a slight decrease in ABA and an increase in IAA in the kaolin treatment, which in turn were associated with the improvement of physiological performance. A month after spraying, kaolin improves the water potential respectively, 30% and 17% in the predawn and midday periods. Besides, plants treated with kaolin showed higher values of stomatal conductance, net CO 2 assimilation rate and intrinsic water use efficiency. Kaolin also ameliorates the effective PSII efficiency (67%), as well as the maximum quantum efficiency of photosystem II and the photosynthetic electron transport rate (>73%). These results were consistent with the higher photochemical quenching and the lower non-photochemical quenching observed in treated leaves and with the better performance obtained by the JIP test parameters. Physiological and hormonal analysis confirmed that kaolin effectively enhance grapevine summer stress tolerance. Copyright © 2017 Elsevier GmbH. All rights reserved.

  16. 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…

  17. 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.

  18. 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

  19. FOREWORD: International Summer School for Advanced Studies 'Dynamics of open nuclear systems' (PREDEAL12)

    Science.gov (United States)

    Delion, D. S.; Zamfir, N. V.; Raduta, A. R.; Gulminelli, F.

    2013-02-01

    This proceedings volume contains the invited lectures and contributions presented at the International Summer School on Nuclear Physics held at Trei Brazi, a summer resort of the Bioterra University, near the city of Predeal, Romania, on 9-20 July 2012. The long tradition of International Summer Schools on Nuclear Physics in Romania dates as far back as 1964, with the event being scheduled every two years. During this period of almost 50 years, many outstanding nuclear scientists have lectured on various topics related to nuclear physics and particle physics. This year we celebrate the 80th birthday of Aureliu Sandulescu, one of the founders of the Romanian school of theoretical nuclear physics. He was Serban Titeica's PhD student, one of Werner Heisenberg's PhD students, and he organized the first edition of this event. Aureliu Sandulescu's major contributions to the field of theoretical nuclear physics are related in particular to the prediction of cluster radioactivity, the physics of open quantum systems and the innovative technique of detecting superheavy nuclei using the double magic projectile 48Ca (Calcium), nowadays a widely used method at the JINR—Dubna and GSI—Darmstadt laboratories. The title of the event, 'Dynamics of Open Nuclear Systems', is in recognition of Aureliu Sandulescu's great personality. The lectures were attended by Romanian and foreign Master and PhD students and young researchers in nuclear physics. About 25 reputable professors and researchers in nuclear physics delivered lectures during this period. According to a well-established tradition, an interval of two hours was allotted for each lecture (including discussions). Therefore we kept a balance between the school and conference format. Two lectures were held during the morning and afternoon sessions. After lecture sessions, three or four oral contributions were given by young scientists. This was a good opportunity for them to present the results of their research in front of

  20. 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...

  1. Succession of phytoplankton assemblages in response to large-scale reservoir operation: a case study in a tributary of the Three Gorges Reservoir, China.

    Science.gov (United States)

    Xiao, Yan; Li, Zhe; Guo, Jinsong; Fang, Fang; Smith, Val H

    2016-03-01

    The Three Gorges Dam (TGD) has greatly altered ecological and environmental conditions within the reservoir region, but it is not known how these changes affect phytoplankton structure and dynamics. Here, a bimonthly monitoring program was implemented from 2007 to 2009 to study the impact of damming on phytoplankton assemblages in the backwater area of the Pengxi River (PBA). By application of the phytoplankton functional group (C strategists, competitive species; S strategists, stress-tolerant species; R strategists, rapid propagation species), seasonal changes in phytoplankton relative to environmental variations were evaluated using ordination analysis. Seasonal patterns of phytoplankton dynamics were detected during this study, with CS/S strategists causing algal blooms from mid-spring to early summer, CS/CR strategists often observed during flood season, and CS strategists dominant during mid-autumn. CR/R groups dominated during winter and caused algal blooms in February. Our results indicated that phytoplankton assemblages were directly related to reservoir operation effects. Generally, the TGD had a low water level during flood season, resulting in a relatively short hydraulic retention time and intensive variability, which supported the cooccurrence of CS and CR species. During the winter drought season, water storage in the TGD increased the water level and the hydraulic retention time in the PBA, enabling R/CR strategists to overcome the sedimentation effect and to out-compete S/CS species in winter. As expected, these diversity patterns were significantly correlated with the hydraulic retention time and nutrient limitation pattern in the PBA. This study provides strategic insight for evaluating the impacts of reservoir operations on phytoplankton adaptation.

  2. Initial growth of phytoplankton in turbid estuaries: a simple model

    NARCIS (Netherlands)

    de Swart, H.E.; Schuttelaars, H.; Talke, S.A.

    2009-01-01

    An idealised model is presented and analysed to gain more fundamental understanding about the dynamics of phytoplankton blooms in well-mixed, suspended sediment dominated estuaries. The model describes the behaviour of subtidal currents, suspended sediments, nutrients and phytoplankton in a channel

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

    African Journals Online (AJOL)

    Seasonal Variability of Phytoplankton Population in the Brahmani Estuary of Orissa, India. S Palleyi, RN Kar, CR Panda. Abstract. The dynamic relationship of water physico-chemical characteristics with phytoplankton has long been of great interest in both experimental ecology and environmental management. This study ...

  4. Remote sensing the phytoplankton seasonal succession of the Red Sea.

    Science.gov (United States)

    Raitsos, Dionysios E; Pradhan, Yaswant; Brewin, Robert J W; Stenchikov, Georgiy; Hoteit, Ibrahim

    2013-01-01

    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

  5. 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

  6. Developing a Phytoplankton Biotic Index as an Indicator of Freshwater Inflow within a Subtropical Estuary

    Science.gov (United States)

    Steichen, J. L.; Quigg, A.; Lucchese, A.; Preischel, H.

    2016-02-01

    Freshwater inflows drive the water and sediment quality in coastal bays and estuaries influencing the ecosystem and health of the biological community. Phytoplankton accessory pigments (used as a proxy for major taxonomic groups) have been utilized to develop a biotic index of physical, chemical and biotic disturbances in Chesapeake Bay (USA) and other estuarine systems. In this study we have used the Chesapeake Bay - Phytoplankton Index of Biotic Integrity model as a guide in developing an index for Galveston Bay, TX (USA) as an indicator of sufficient freshwater inflow to a subtropical estuary. Multivariate statistical analyses were run using PRIMER-E+PERMANOVA to determine the correlations between phytoplankton accessory pigment concentrations and a suite of abiotic factors associated with freshwater inflow (salinity, DIN, PO4, secchi). Phytoplankton pigment concentrations and water quality parameters were collected across Galveston Bay on a monthly basis from 2008-2013. In the upper region of the bay nearest the river source Dinophyceae, Cryptophyceae (winter (Dec-Feb)) and Chlorophyceae (winter and spring (Mar-May)) were significantly correlated to freshwater inflow and nutrient concentrations PO4 (p<0.05). Increased concentrations of Bacillariophyceae and Cyanophyceae (summer (Jun-Aug)) were significantly correlated to lower concentrations of DIN (p<0.05). Near the mouth of the estuary there was a significant correlation between the increase in Bacillariophyceae, Cyanophyceae, Cryptophyceae and Dinophyceae with decreasing PO4 (p<0.05). Within the dynamic system of Galveston Bay we are working to apply a Phytoplankton Index of Biotic Integrity as a means of monitoring the biological health of this ecologically and economically important estuarine ecosystem.

  7. 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...

  8. 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...

  9. Indian Summer Monsoon dynamics during Termination II and MIS 5e

    Science.gov (United States)

    Magiera, Matthias; Erhardt, Andrea M.; Hartland, Adam; Kwiecien, Ola; Cheng, Hai; Immenhauser, Adrian; Turchyn, Alexandra; Breitenbach, Sebastian F. M.

    2017-04-01

    The interpretation of speleothem oxygen isotope ratios (δ18O) as proxy for Indian Summer Monsoon (ISM) dynamics is ambiguous, due to multiple influencing factors. Here we combine δ18O and calcium isotope δ44Ca analyses with elemental data to delineate regional shifts in moisture source, local rainfall amount, and changes in ISM intensity and length during Termination II and MIS 5e. Oxygen isotope ratios reflect a mixed signal of moisture source dynamics and rainfall amount; δ44Ca and Mg/Ca ratios are interpreted as proxies for local effective moisture and prior calcite precipitation (PCP) in the epikarst. The age of stalagmite MAW-3 from Mawmluh Cave, NE India, is constraint by six U-series dates. 108 samples, obtained at 0.4 mm resolution from the 70 mm long speleothem sample, have been analysed for δ18O, δ44Ca and Mg/Ca. Oxygen isotope ratios were measured on a ThermoFisher Scientific MAT 253 at Ruhr-University Bochum. Elemental ratios were measured on a quadrupole ICP-MS at Waikato University. Calcium isotope ratios were analyzed on a ThermoFisher Scientific Triton at University of Cambridge. MAW-3 grew from 136 kyrs BP to 96 kyrs BP, covering Termination II and MIS 5e. Oxygen isotope values are high (ca. +0.91 ‰) during Termination II, reach a minimum during MIS 5e (-3.5 ‰), and rise again to -0.2 ‰ at the end of MIS 5e. Calcium isotope ratios range from -0.32 ‰ to -0.70 ‰ and show a positive correlation (R2= 0.7) with δ18O. High δ18O values during Termination II reflect reduced atmospheric circulation and/or a proximal moisture source (Bay of Bengal), implying lowered ISM intensity. A positive correlation of δ18O with δ44Ca suggests concurrent changes of moisture source location and local rainfall amount, with a proximal moisture source and reduced effective rainfall during periods of weak ISM. Elevated Mg/Ca ratios at such intervals corroborate PCP occurrence, which reflects dry conditions. The beginning of MIS 5e (ca. 132 kyrs BP) is

  10. Relationships between Concentrations of Phytoplankton Chlorophyll a and Total Nitrogen in Ten U.S. Estuaries

    Science.gov (United States)

    This presentation focuses on the summertime response of phytoplankton chlorophyll to nitrogen concentrations in the upper water columns of ten U.S. estuaries. Using publicly available data from monitoring programs, regression relationships have been developed between summer surfa...

  11. Towards an Understanding of the Interactions between Freshwater Inflows and Phytoplankton Communities in a Subtropical Estuary in the Gulf of Mexico.

    Directory of Open Access Journals (Sweden)

    Samuel Dorado

    Full Text Available Subtropical estuaries worldwide face increased pressure on their ecosystem health and services due to increasing human population growth and associated land use/land cover changes, expansion of ports, and climate change. We investigated freshwater inflows (river discharge and the physico-chemical characteristics of Galveston Bay (Texas, USA as mechanisms driving variability in phytoplankton biomass and community composition between February 2008 and December 2009. Results of multivariate analyses (hierarchical cluster analysis, PERMANOVA, Mantel test, and nMDS ordination coupled to environmental vector fitting revealed that temporal and spatial differences in phytoplankton community structure correlate to differences in hydrographic and water quality parameters. Spatially, phytoplankton biomass and community composition responded to nutrient loading from the San Jacinto River in the northwest region of the bay (consistent with nutrient limitation while hydraulic displacement (and perhaps other processes resulted in overall lower biomass in the Trinity River delta (northeast region. The influence of inflows on phytoplankton diminished along a north to south gradient in the bay. Temporally, temperature and variables associated with freshwater inflow (discharge volume, salinity, inorganic nitrogen and phosphorus concentrations were major influences on phytoplankton dynamics. Dissolved inorganic nitrogen: phosphorus (DIN:DIP ratios suggest that phytoplankton communities will be predominately nitrogen limited. Diatoms dominated during periods of moderate to high freshwater inflows in winter/spring and were more abundant in the upper bay while cyanobacteria dominated during summer/fall when inflow was low. Given the differential influences of freshwater inflow on the phytoplankton communities of Galveston Bay, alterations upstream (magnitude, timing, frequency will likely have a profound effect on downstream ecological processes and corresponding

  12. Pigment signatures of phytoplankton communities in the Beaufort Sea

    Science.gov (United States)

    Coupel, P.; Matsuoka, A.; Ruiz-Pino, D.; Gosselin, M.; Marie, D.; Tremblay, J.-É.; Babin, M.

    2015-02-01

    Phytoplankton are expected to respond to recent environmental changes of the Arctic Ocean. In terms of bottom-up control, modifying the phytoplankton distribution will ultimately affect the entire food web and carbon export. However, detecting and quantifying changes in phytoplankton communities in the Arctic Ocean remains difficult because of the lack of data and the inconsistent identification methods used. Based on pigment and microscopy data sampled in the Beaufort Sea during summer 2009, we optimized the chemotaxonomic tool CHEMTAX (CHEMical TAXonomy) for the assessment of phytoplankton community composition in an Arctic setting. The geographical distribution of the main phytoplankton groups was determined with clustering methods. Four phytoplankton assemblages were determined and related to bathymetry, nutrients and light availability. Surface waters across the whole survey region were dominated by prasinophytes and chlorophytes, whereas the subsurface chlorophyll maximum was dominated by the centric diatoms Chaetoceros socialis on the shelf and by two populations of nanoflagellates in the deep basin. Microscopic counts showed a high contribution of the heterotrophic dinoflagellates Gymnodinium and Gyrodinium spp. to total carbon biomass, suggesting high grazing activity at this time of the year. However, CHEMTAX was unable to detect these dinoflagellates because they lack peridinin. In heterotrophic dinoflagellates, the inclusion of the pigments of their prey potentially leads to incorrect group assignments and some misinterpretation of CHEMTAX. Thanks to the high reproducibility of pigment analysis, our results can serve as a baseline to assess change and spatial or temporal variability in several phytoplankton populations that are not affected by these misinterpretations.

  13. Photosynthetic carbon metabolism in freshwater phytoplankton

    International Nuclear Information System (INIS)

    Groeger, A.W.

    1986-01-01

    Photosynthetic carbon metabolism of natural assemblages of freshwater phytoplankton was measured by following the flow of inorganic 14 C into the photosynthetic end products polysaccharide protein, lipid, and soluble metabolites. Data were collected from a wide range of physical, chemical, and trophic conditions in six southern United States reservoirs, with the primary environmental variables of interest being light intensity and nutrient supply. Polysaccharide and protein were consistently the primary products of photosynthetic carbon metabolism, comprising an average of 70% of the total carbon fixation over a wide range of light intensities. Polysaccharide was quantitatively more important at higher light intensities, and protein at lower light intensities, as light intensity varied both with depth within the water column and over diurnal cycles. Polysaccharide synthesis was more variable over the diurnal period than was protein synthesis. Phytoplankton in the downlake epilimnion of Normandy Lake, a central Tennessee reservoir, responded to summer nitrogen (N) deficiency by increasing relative rates of lipid synthesis from 10-15% to 20-25% of the total photosynthetic carbon fixation. Phytoplankton in more nitrogen-sufficient areas of the reservoir maintained lower rates of lipid synthesis throughout the summer. These results document the occurrence in nature of a relationship between N-deficiency and increased lipid synthesis previously observed only in laboratory algal culture studies

  14. Trace metal dynamics in zooplankton from the Bay of Bengal during summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Rejomon, G.; DineshKumar, P.K.; Nair, M.; Muraleedharan, K.R.

    Trace metal (Fe, Co, Ni, Cu, Zn, Cd, and Pb) concentrations in zooplankton from the mixed layer were investigated at 8 coastal and 20 offshore stations in the western Bay of Bengal during the summer monsoon of 2003. The ecotoxicological importance...

  15. Dynamics of sea-ice biogeochemistry in the coastal Antarctica during transition from summer to winter

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S; Jena, B.; Mohan, R.

    The seasonality of carbon dioxide partial pressure (pCO2), air-sea CO2 fluxes and associated environmental parameters were investigated in the Antarctic coastal waters. The in-situ survey was carried out from the austral summer...

  16. Dynamical and thermodynamical coupling between the North Atlantic subtropical high and the marine boundary layer clouds in boreal summer

    Science.gov (United States)

    Wei, Wei; Li, Wenhong; Deng, Yi; Yang, Song; Jiang, Jonathan H.; Huang, Lei; Liu, W. Timothy

    2018-04-01

    This study investigates dynamical and thermodynamical coupling between the North Atlantic subtropical high (NASH), marine boundary layer (MBL) clouds, and the local sea surface temperatures (SSTs) over the North Atlantic in boreal summer for 1984-2009 using NCEP/DOE Reanalysis 2 dataset, various cloud data, and the Hadley Centre sea surface temperature. On interannual timescales, the summer mean subtropical MBL clouds to the southeast of the NASH is actively coupled with the NASH and local SSTs: a stronger (weaker) NASH is often accompanied with an increase (a decrease) of MBL clouds and abnormally cooler (warmer) SSTs along the southeast flank of the NASH. To understand the physical processes between the NASH and the MBL clouds, the authors conduct a data diagnostic analysis and implement a numerical modeling investigation using an idealized anomalous atmospheric general circulation model (AGCM). Results suggest that significant northeasterly anomalies in the southeast flank of the NASH associated with an intensified NASH tend to induce stronger cold advection and coastal upwelling in the MBL cloud region, reducing the boundary surface temperature. Meanwhile, warm advection associated with the easterly anomalies from the African continent leads to warming over the MBL cloud region at 700 hPa. Such warming and the surface cooling increase the atmospheric static stability, favoring growth of the MBL clouds. The anomalous diabatic cooling associated with the growth of the MBL clouds dynamically excites an anomalous anticyclone to its north and contributes to strengthening of the NASH circulation in its southeast flank. The dynamical and thermodynamical couplings and their associated variations in the NASH, MBL clouds, and SSTs constitute an important aspect of the summer climate variability over the North Atlantic.

  17. Multicellular Features of Phytoplankton

    Directory of Open Access Journals (Sweden)

    Adi Abada

    2018-04-01

    Full Text Available Microscopic marine phytoplankton drift freely in the ocean, harvesting sunlight through photosynthesis. These unicellular microorganisms account for half of the primary productivity on Earth and play pivotal roles in the biogeochemistry of our planet (Field et al., 1998. The major groups of microalgae that comprise the phytoplankton community are coccolithophores, diatoms and dinoflagellates. In present oceans, phytoplankton individuals and populations are forced to rapidly adjust, as key chemical and physical parameters defining marine habitats are changing globally. Here we propose that microalgal populations often display the characteristics of a multicellular-like community rather than a random collection of individuals. Evolution of multicellularity entails a continuum of events starting from single cells that go through aggregation or clonal divisions (Brunet and King, 2017. Phytoplankton may be an intermediate state between single cells and aggregates of physically attached cells that communicate and co-operate; perhaps an evolutionary snapshot toward multicellularity. In this opinion article, we journey through several studies conducted in two key phytoplankton groups, coccolithophores and diatoms, to demonstrate how observations in these studies could be interpreted in a multicellular context.

  18. Function assessment of coastal ecosystem based on phytoplankton community structure

    DEFF Research Database (Denmark)

    Haraguchi, Lumi

    2018-01-01

    on phytoplankton community structure; and 3) investigating the role of planktonic communities on the cycling of dissolved organic matter. Those objectives were addressed focusing the temperate mesohaline estuary of Roskilde Fjord (Denmark). Paper I, explores the use of Pulse-shape recording flow cytometry (PFCM...... as an energy reservoir, buffering changes in the nutrient supply. Finally, the results embedded in this thesis demonstrate the importance of integrating different time scales to understand functioning of phytoplankton communities. Phytoplankton dynamics should not be regarded just in light of inorganic......This Ph.D. project aimed to improve the knowledge on phytoplankton community structure and its influence in the carbon transfer and nutrient cycling in coastal waters, by: 1) assessing the importance of phytoplankton

  19. On the key role of droughts in the dynamics of summer fires in Mediterranean Europe.

    Science.gov (United States)

    Turco, Marco; von Hardenberg, Jost; AghaKouchak, Amir; Llasat, Maria Carmen; Provenzale, Antonello; Trigo, Ricardo M

    2017-03-06

    Summer fires frequently rage across Mediterranean Europe, often intensified by high temperatures and droughts. According to the state-of-the-art regional fire risk projections, in forthcoming decades climate effects are expected to become stronger and possibly overcome fire prevention efforts. However, significant uncertainties exist and the direct effect of climate change in regulating fuel moisture (e.g. warmer conditions increasing fuel dryness) could be counterbalanced by the indirect effects on fuel structure (e.g. warmer conditions limiting fuel amount), affecting the transition between climate-driven and fuel-limited fire regimes as temperatures increase. Here we analyse and model the impact of coincident drought and antecedent wet conditions (proxy for the climatic factor influencing total fuel and fine fuel structure) on the summer Burned Area (BA) across all eco-regions in Mediterranean Europe. This approach allows BA to be linked to the key drivers of fire in the region. We show a statistically significant relationship between fire and same-summer droughts in most regions, while antecedent climate conditions play a relatively minor role, except in few specific eco-regions. The presented models for individual eco-regions provide insights on the impacts of climate variability on BA, and appear to be promising for developing a seasonal forecast system supporting fire management strategies.

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

    Directory of Open Access Journals (Sweden)

    M. J. Behrenfeld

    2009-05-01

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

  1. Monitoring natural phytoplankton communities

    DEFF Research Database (Denmark)

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

    2017-01-01

    -consuming and/or expensive, limiting sampling frequency. The use of faster methods, such as flow cytometry, has become more frequent in phytoplankton studies, although comparisons between this technique and traditional ones are still scarce. This study aimed to assess if natural phytoplankton communities...... 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...

  2. Temporal and vertical variability in optical properties of New England shelf waters during late summer and spring

    Science.gov (United States)

    Sosik, Heidi M.; Green, Rebecca E.; Pegau, W. Scott; Roesler, Collin S.

    2001-05-01

    Relationships between optical and physical properties were examined on the basis of intensive sampling at a site on the New England continental shelf during late summer 1996 and spring 1997. During both seasons, particles were found to be the primary source of temporal and vertical variability in optical properties since light absorption by dissolved material, though significant in magnitude, was relatively constant. Within the particle pool, changes in phytoplankton were responsible for much of the observed optical variability. Physical processes associated with characteristic seasonal patterns in stratification and mixing contributed to optical variability mostly through effects on phytoplankton. An exception to this generalization occurred during summer as the passage of a hurricane led to a breakdown in stratification and substantial resuspension of nonphytoplankton particulate material. Prior to the hurricane, conditions in summer were highly stratified with subsurface maxima in absorption and scattering coefficients. In spring, stratification was much weaker but increased over the sampling period, and a modest phytoplankton bloom caused surface layer maxima in absorption and scattering coefficients. These seasonal differences in the vertical distribution of inherent optical properties were evident in surface reflectance spectra, which were elevated and shifted toward blue wavelengths in the summer. Some seasonal differences in optical properties, including reflectance spectra, suggest that a significant shift toward a smaller particle size distribution occurred in summer. Shorter timescale optical variability was consistent with a variety of influences including episodic events such as the hurricane, physical processes associated with shelfbreak frontal dynamics, biological processes such as phytoplankton growth, and horizontal patchiness combined with water mass advection.

  3. Interactive effect of temperature and CO2 increase in Arctic phytoplankton

    Directory of Open Access Journals (Sweden)

    Alexandra eCoello-Camba

    2014-10-01

    Full Text Available An experiment was performed in order to analyze the effects of the increase in water temperature and CO2 partial pressure expected for the end of this century in a present phytoplankton community inhabiting the Arctic Ocean. We analyzed both factors acting independently and together, to test possible interactions between them. The arctic planktonic community was incubated under 6 different treatments combining three experimental temperatures (1 ºC, 6 ºC and 10 ºC with two different CO2 levels of 380 ppm or 1000 ppm, at the UNIS installations in Longyearbyen (Svalbard, in summer 2010. Under warmer temperatures, a decrease in chlorophyll a concentration, biovolume and primary production was found, together with a shift in community structure towards a dominance of smaller cells (nano-sized. Effects of increased pCO2 were more modest, and although interactions were weak, our results suggest antagonistic interactive effects amongst increased temperature and CO2 levels, as elevated CO2 compensated partially the decrease in phytoplankton biomass induced by temperature in some groups. Interactions between the two stressors were generally weak, but elevated CO2 was observed to lead to a stepper decline in primary production with warming. Our results also suggest that future increases in water temperature and pCO2 would lead to a decrease in the community chl a concentration and biomass in the Arctic phytoplankton communities examined, leading to communities dominated by smaller nano-phytoplankton groups, with important consequences for the flow of carbon and food web dynamics.

  4. Long-term changes of the phytoplankton community and biomass in the subtropical shallow Patos Lagoon Estuary, Brazil

    Science.gov (United States)

    Haraguchi, Lumi; Carstensen, Jacob; Abreu, Paulo Cesar; Odebrecht, Clarisse

    2015-09-01

    Seasonal and interannual changes (1993-2012) of water temperature and transparency, river discharge, salinity, water quality properties, chlorophyll a (chl-a) and the carbon biomass of the main taxonomical phytoplankton groups were evaluated at a shallow station (∼2 m) in the subtropical Patos Lagoon Estuary (PLE), Brazil. Large variations in salinity (0-35), due to a complex balance between Patos Lagoon outflow and oceanic inflows, affected significantly other water quality variables and phytoplankton dynamics, masking seasonal and interannual variability. Therefore, salinity effect was filtered out by means of a Generalized Additive Model (GAM). River discharge and salinity had a significant negative relation, with river discharge being highest and salinity lowest during July to October. Diatoms comprised the dominant phytoplankton group, contributing substantially to the seasonal cycle of chl-a showing higher values in austral spring/summer (September to April) and lowest in autumn/winter (May to August). PLE is a nutrient-rich estuary and the phytoplankton seasonal cycle was largely driven by light availability, with few exceptions in winter. Most variables exhibited large interannual variability. When varying salinity effect was accounted for, chl-a concentration and diatom biomass showed less irregularity over time, and significant increasing trends emerged for dinoflagellates and cyanobacteria. Long-term changes in phytoplankton and water quality were strongly related to variations in salinity, largely driven by freshwater discharge influenced by climatic variability, most pronounced for ENSO events. However, the significant increasing trend of the N:P ratio indicates that important environmental changes related to anthropogenic effects are undergoing, in addition to the hydrology in the PLE.

  5. 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.

  6. 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...

  7. 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.

  8. Latitudinal variation of phytoplankton communities in the western Arctic Ocean

    Science.gov (United States)

    Min Joo, Hyoung; Lee, Sang H.; Won Jung, Seung; Dahms, Hans-Uwe; Hwan Lee, Jin

    2012-12-01

    Recent studies have shown that photosynthetic eukaryotes are an active and often dominant component of Arctic phytoplankton assemblages. In order to explore this notion at a large scale, samples were collected to investigate the community structure and biovolume of phytoplankton along a transect in the western Arctic Ocean. The transect included 37 stations at the surface and subsurface chlorophyll a maximum (SCM) depths in the Bering Sea, Chukchi Sea, and Canadian Basin from July 19 to September 5, 2008. Phytoplankton (>2 μm) were identified and counted. A cluster analysis of abundance and biovolume data revealed different assemblages over the shelf, slope, and basin regions. Phytoplankton communities were composed of 71 taxa representing Dinophyceae, Cryptophyceae, Bacillariophyceae, Chrysophyceae, Dictyochophyceae, Prasinophyceae, and Prymnesiophyceae. The most abundant species were of pico- to nano-size at the surface and SCM depths at most stations. Nano- and pico-sized phytoplankton appeared to be dominant in the Bering Sea, whereas diatoms and nano-sized plankton provided the majority of taxon diversity in the Bering Strait and in the Chukchi Sea. From the western Bering Sea to the Bering Strait, the abundance, biovolume, and species diversity of phytoplankton provided a marked latitudinal gradient towards the central Arctic. Although pico- and nano-sized phytoplankton contributed most to cell abundance, their chlorophyll a contents and biovolumes were less than those of the larger micro-sized taxa. Micro-sized phytoplankton contributed most to the biovolume in the largely ice-free waters of the western Arctic Ocean during summer 2008.

  9. Physical and Biogeochemical Controls of the Phytoplankton Blooms in North Western Mediterranean Sea: A Multiplatform Approach Over a Complete Annual Cycle (2012-2013 DEWEX Experiment)

    Science.gov (United States)

    Mayot, Nicolas; D'Ortenzio, Fabrizio; Taillandier, Vincent; Prieur, Louis; de Fommervault, Orens Pasqueron; Claustre, Hervé; Bosse, Anthony; Testor, Pierre; Conan, Pascal

    2017-12-01

    The North Western Mediterranean Sea exhibits recurrent and significant autumnal and spring phytoplankton blooms. The existence of these two blooms coincides with typical temperate dynamics. To determine the potential control of physical and biogeochemical factors on these phytoplankton blooms, data from a multiplatform approach (combining ships, Argo and BGC-Argo floats, and bio-optical gliders) were analyzed in association with satellite observations in 2012-2013. The satellite framework allowed a simultaneous analysis over the whole annual cycle of in situ observations of mixed layer depth, photosynthetical available radiation, particle backscattering, nutrients (nitrate and silicate), and chlorophyll-a concentrations. During the year 2012-2013, satellite ocean color observations, confirmed by in situ data, have revealed the existence of two areas (or bioregions) with comparable autumnal blooms but contrasting spring blooms. In both bioregions, the ratio of the euphotic zone (defined as the isolume 0.415 mol photons m-2 d-1, Z0.415) and the MLD identified the initiation of the autumnal bloom, as well as the maximal annual increase in [Chl-a] in spring. In fact, the autumnal phytoplankton bloom might be initiated by mixing of the summer shallowing deep chlorophyll maximum, while the spring restratification (when Z0.415/MLD ratio became >1) might induce surface phytoplankton production that largely overcomes the losses. Finally, winter deep convection events that took place in one of the bioregions induced higher net accumulation rate of phytoplankton in spring associated with a diatom-dominated phytoplankton community principally. We suggest that very deep winter MLD lead to an increase in surface silicates availability, which favored the development of diatoms.

  10. The contribution of phytoplankton degradation to chromophoric dissolved organic matter (CDOM) in eutrophic shallow lakes: Field and experimental evidence

    NARCIS (Netherlands)

    Zhang, Y.; Van Dijk, M.A.; Liu, M.; Zhu, G.; Qin, B.

    2009-01-01

    Eight field campaigns in the eutrophic, shallow, Lake Taihu in the summers from 2005 to 2007, and a phytoplankton degradation experiment of 33 days, were carried out to determine the contribution of phytoplankton degradation to CDOM. Significant and positive correlations were found between the CDOM

  11. Photoreception in Phytoplankton.

    Science.gov (United States)

    Colley, Nansi Jo; Nilsson, Dan-Eric

    2016-11-01

    In many species of phytoplankton, simple photoreceptors monitor ambient lighting. Photoreceptors provide a number of selective advantages including the ability to assess the time of day for circadian rhythms, seasonal changes, and the detection of excessive light intensities and harmful UV light. Photoreceptors also serve as depth gauges in the water column for behaviors such as diurnal vertical migration. Photoreceptors can be organized together with screening pigment into visible eyespots. In a wide variety of motile phytoplankton, including Chlamydomonas, Volvox, Euglena, and Kryptoperidinium, eyespots are light-sensitive organelles residing within the cell. Eyespots are composed of photoreceptor proteins and typically red to orange carotenoid screening pigments. This association of photosensory pigment with screening pigment allows for detection of light directionality, needed for light-guided behaviors such as positive and negative phototaxis. In Chlamydomonas, the eyespot is located in the chloroplast and Chlamydomonas expresses a number of photosensory pigments including the microbial channelrhodopsins (ChR1 and ChR2). Dinoflagellates are unicellular protists that are ecologically important constituents of the phytoplankton. They display a great deal of diversity in morphology, nutritional modes and symbioses, and can be photosynthetic or heterotrophic, feeding on smaller phytoplankton. Dinoflagellates, such as Kryptoperidinium foliaceum, have eyespots that are used for light-mediated tasks including phototaxis. Dinoflagellates belonging to the family Warnowiaceae have a more elaborate eye. Their eye-organelle, called an ocelloid, is a large, elaborate structure consisting of a focusing lens, highly ordered retinal membranes, and a shield of dark pigment. This complex eye-organelle is similar to multicellular camera eyes, such as our own. Unraveling the molecular makeup, structure and function of dinoflagellate eyes, as well as light-guided behaviors in

  12. ESA-MERIS 10-Year Mission Reveals Contrasting Phytoplankton Bloom Dynamics in Two Tropical Regions of Northern Australia

    Directory of Open Access Journals (Sweden)

    David Blondeau-Patissier

    2014-04-01

    Full Text Available The spatial and temporal variability of phytoplankton blooms was investigated in two tropical coastal regions of northern Australia using the MEdium Resolution Imaging Spectrometer (MERIS full mission (2002–2012 reduced resolution dataset. Satellite-derived proxies for phytoplankton (Chlorophyll-a (Chl, Fluorescence Line Height (FLH, Maximum Chlorophyll Index (MCI and suspended sediment (Total Suspended Matter (TSM were jointly analyzed for two clusters of the Great Barrier Reef Wet tropics (GBRW; 15°–19.5°S; Queensland and the Van Diemen Gulf (VDG; 9°–13°S; Northern Territory. The analysis of time-series and Hovmöller diagrams of the four MERIS products provided a unique perspective on the processes linking phytoplankton blooms and river runoff, or resuspension, across spatio-temporal scales. Both regions are characterized by a complex oceanography and seasonal inflows of sediment, freshwater and nutrients during the tropical wet season months (November to April. The GBRW is characterized by a great variability in water clarity (Secchi depth 0–25 m. A long history of agricultural land use has led to a large increase in the seasonal discharge of sediments and nutrients, triggering seasonal phytoplankton blooms (>0.4 mg∙m−3 between January and April. In contrast, the VDG is a poorly flushed, turbid (Secchi depth <5 m environment with strong tidal-energy (4–8 m and very limited land use. Phytoplankton blooms here were found to have higher Chl concentrations (>1.0 mg∙m−3 than in the GBRW, occurring up to twice a year between January and April. Over the 10-year MERIS mission, a weak decline in Chl and TSM was observed for the VDG (Sen slope: −2.85%/decade, τ = −0.32 and −3.57%/decade, τ = −0.24; p 0.05, while no significant trend in those two satellite products was observed in the GBRW. Cyanobacteria surface algal blooms occur in both regions between August and October. The MCI and FLH products were found to

  13. Assessing spatial and temporal variability of phytoplankton communities' composition in the Iroise Sea ecosystem (Brittany, France): A 3D modeling approach. Part 1: Biophysical control over plankton functional types succession and distribution

    Science.gov (United States)

    Cadier, Mathilde; Gorgues, Thomas; Sourisseau, Marc; Edwards, Christopher A.; Aumont, Olivier; Marié, Louis; Memery, Laurent

    2017-01-01

    Understanding the dynamic interplay between physical, biogeochemical and biological processes represents a key challenge in oceanography, particularly in shelf seas where complex hydrodynamics are likely to drive nutrient distribution and niche partitioning of phytoplankton communities. The Iroise Sea includes a tidal front called the 'Ushant Front' that undergoes a pronounced seasonal cycle, with a marked signal during the summer. These characteristics as well as relatively good observational sampling make it a region of choice to study processes impacting phytoplankton dynamics. This innovative modeling study employs a phytoplankton-diversity model, coupled to a regional circulation model to explore mechanisms that alter biogeography of phytoplankton in this highly dynamic environment. Phytoplankton assemblages are mainly influenced by the depth of the mixed layer on a seasonal time scale. Indeed, solar incident irradiance is a limiting resource for phototrophic growth and small phytoplankton cells are advantaged over larger cells. This phenomenon is particularly relevant when vertical mixing is intense, such as during winter and early spring. Relaxation of wind-induced mixing in April causes an improvement of irradiance experienced by cells across the whole study area. This leads, in late spring, to a competitive advantage of larger functional groups such as diatoms as long as the nutrient supply is sufficient. This dominance of large, fast-growing autotrophic cells is also maintained during summer in the productive tidally-mixed shelf waters. In the oligotrophic surface layer of the western part of the Iroise Sea, small cells coexist in a greater proportion with large, nutrient limited cells. The productive Ushant tidal front's region (1800 mgC·m- 2·d- 1 between August and September) is also characterized by a high degree of coexistence between three functional groups (diatoms, micro/nano-flagellates and small eukaryotes/cyanobacteria). Consistent with

  14. NATO Advanced Study Institute on International Summer School on Chaotic Dynamics and Transport in Classical and Quantum Systems

    CERN Document Server

    Collet, P; Métens, S; Neishtadt, A; Zaslavsky, G; Chaotic Dynamics and Transport in Classical and Quantum Systems

    2005-01-01

    This book offers a modern updated review on the most important activities in today dynamical systems and statistical mechanics by some of the best experts in the domain. It gives a contemporary and pedagogical view on theories of classical and quantum chaos and complexity in hamiltonian and ergodic systems and their applications to anomalous transport in fluids, plasmas, oceans and atom-optic devices and to control of chaotic transport. The book is issued from lecture notes of the International Summer School on "Chaotic Dynamics and Transport in Classical and Quantum Systems" held in Cargèse (Corsica) 18th to the 30th August 2003. It reflects the spirit of the School to provide lectures at the post-doctoral level on basic concepts and tools. The first part concerns ergodicity and mixing, complexity and entropy functions, SRB measures, fractal dimensions and bifurcations in hamiltonian systems. Then, models of dynamical evolutions of transport processes in classical and quantum systems have been largely expla...

  15. Recent changes in the summer monsoon circulation and their impact on dynamics and thermodynamics of the Arabian Sea

    Science.gov (United States)

    Pratik, Kad; Parekh, Anant; Karmakar, Ananya; Chowdary, Jasti S.; Gnanaseelan, C.

    2018-05-01

    The present study examines changes in the low-level summer monsoon circulation over the Arabian Sea and their impact on the ocean dynamics using reanalysis data. The study confirms intensification and northward migration of low-level jet during 1979 to 2015. Further during the study period, an increase in the Arabian Sea upper ocean heat content is found in spite of a decreasing trend in the net surface heat flux, indicating the possible role of ocean dynamics in the upper ocean warming. Increase in the anti-cyclonic wind stress curl associated with the change in the monsoon circulation induces downwelling over the central Arabian Sea, favoring upper ocean warming. The decreasing trend of southward Ekman transport, a mechanism transporting heat from the land-locked north Indian Ocean to southern latitudes, also supports increasing trend of the upper ocean heat content. To reinstate and quantify the role of changing monsoon circulation in increasing the heat content over the Arabian Sea, sensitivity experiment is carried out using ocean general circulation model. In this experiment, the model is forced by inter-annual momentum forcing while rest of the forcing is climatological. Experiment reveals that the changing monsoon circulation increases the upper ocean heat content, effectively by enhancing downwelling processes and reducing southward heat transport, which strongly endorses our hypothesis that changing ocean dynamics associated with low-level monsoon circulation is causing the increasing trend in the heat content of the Arabian Sea.

  16. Lack of seasonality in phytoplankton standing stock (chlorophyll a) and production in the western Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Madhu, N.V.; Jyothibabu, R.; Maheswaran, P.A.; Gerson, V.J.; Gopalakrishnan, T.C.; Nair, K.K.C.

    The investigations in the western Bay of Bengal (BoB) during summer, winter and spring intermonsoon periods evidenced lack of pronounced seasonal variation in phytoplankton standing stock (chlorophyll a) and primary production. The supply...

  17. Summer Study Program in Geophysical Fluid Dynamics, Woods Hole Oceanographic Institution: Chaos.

    Science.gov (United States)

    1985-11-01

    Cleopatra, periodic solutions to Galileo and perhaps chaos to Poincar. Today we often think about dynamical systems in terms o- oincae surfaces of section...P. Berge, 1983. Phys. Rev. Lett. L51, 1446 and 2345. Nadal, J.P., B. Derrida and J. Vannimenus, 1982. J. de Phys. 43, , 1561 and V. Hakim and J.P

  18. 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.

  19. Phytoplankton distribution in three thermally distinct reactor cooling reservoirs

    International Nuclear Information System (INIS)

    Wilde, E.W.

    1983-01-01

    Phytoplankton community structure was studied in relation to physicochemical characteristics of three South Carolina reservoirs in close proximity and of similar age and bottom type. Thermal alteration, resulting from the input of cooling water from a nuclear reactor, was substantially different in each reservoir. This provided an opportunity to compare water temperature effects separated from season. Water temperature (when examined independently in statistical models) appeared to be less important than other environmental variables in determining phytoplankton community structure. Pond C, a reservoir receiving intensely heated effluent (> 20 0 C ΔT), displayed low species diversity (Shannon-Weaver H 0 C in summer. Par Pond, having a maximum ΔT of 5 0 C, displayed no temperature-induced alteration of phytoplankton community structure

  20. 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.

  1. Evaluation of thermal and dynamic impacts of summer dust aerosols on the Red Sea

    KAUST Repository

    Cahill, Bronwyn

    2017-01-16

    The seasonal response of upper ocean processes in the Red Sea to summer-time dust aerosol perturbations is investigated using an uncoupled regional ocean model. We find that the upper limit response is highly sensitive to dust-induced reductions in radiative fluxes. Sea surface cooling of −1°C and −2°C is predicted in the northern and southern regions, respectively. This cooling is associated with a net radiation reduction of −40 W m−2 and −90 W m−2 over the northern and southern regions, respectively. Larger cooling occurs below the mixed layer at 75 m in autumn, −1.2°C (north) and −1.9°C (south). SSTs adjust more rapidly (ca. 30 days) than the subsurface temperatures (seasonal time scales), due to stronger stratification and increased mixed layer stability inhibiting the extent of vertical mixing. The basin average annual heat flux reverses sign and becomes positive, +4.2 W m−2 (as compared to observed estimates −17.3 W m−2) indicating a small gain of heat from the atmosphere. When we consider missing feedbacks from atmospheric processes in our uncoupled experiment, we postulate that the magnitude of cooling and the time scales for adjustment will be much less, and that the annual heat flux will not reverse sign but nevertheless be reduced as a result of dust perturbations. While our study highlights the importance of considering coupled ocean-atmosphere processes on the net surface energy flux in dust perturbation studies, the results of our uncoupled dust experiment still provide an upper limit estimate of the response of the upper ocean to dust-induced radiative forcing perturbations.

  2. Evaluation of thermal and dynamic impacts of summer dust aerosols on the Red Sea

    KAUST Repository

    Cahill, Bronwyn; Toumi, Ralf; Stenchikov, Georgiy L.; Osipov, Sergey; Brindley, Helen

    2017-01-01

    The seasonal response of upper ocean processes in the Red Sea to summer-time dust aerosol perturbations is investigated using an uncoupled regional ocean model. We find that the upper limit response is highly sensitive to dust-induced reductions in radiative fluxes. Sea surface cooling of −1°C and −2°C is predicted in the northern and southern regions, respectively. This cooling is associated with a net radiation reduction of −40 W m−2 and −90 W m−2 over the northern and southern regions, respectively. Larger cooling occurs below the mixed layer at 75 m in autumn, −1.2°C (north) and −1.9°C (south). SSTs adjust more rapidly (ca. 30 days) than the subsurface temperatures (seasonal time scales), due to stronger stratification and increased mixed layer stability inhibiting the extent of vertical mixing. The basin average annual heat flux reverses sign and becomes positive, +4.2 W m−2 (as compared to observed estimates −17.3 W m−2) indicating a small gain of heat from the atmosphere. When we consider missing feedbacks from atmospheric processes in our uncoupled experiment, we postulate that the magnitude of cooling and the time scales for adjustment will be much less, and that the annual heat flux will not reverse sign but nevertheless be reduced as a result of dust perturbations. While our study highlights the importance of considering coupled ocean-atmosphere processes on the net surface energy flux in dust perturbation studies, the results of our uncoupled dust experiment still provide an upper limit estimate of the response of the upper ocean to dust-induced radiative forcing perturbations.

  3. Contrasting effects of summer and winter warming on body mass explain population dynamics in a food-limited Arctic herbivore.

    Science.gov (United States)

    Albon, Steve D; Irvine, R Justin; Halvorsen, Odd; Langvatn, Rolf; Loe, Leif E; Ropstad, Erik; Veiberg, Vebjørn; van der Wal, René; Bjørkvoll, Eirin M; Duff, Elizabeth I; Hansen, Brage B; Lee, Aline M; Tveraa, Torkild; Stien, Audun

    2017-04-01

    The cumulative effects of climate warming on herbivore vital rates and population dynamics are hard to predict, given that the expected effects differ between seasons. In the Arctic, warmer summers enhance plant growth which should lead to heavier and more fertile individuals in the autumn. Conversely, warm spells in winter with rainfall (rain-on-snow) can cause 'icing', restricting access to forage, resulting in starvation, lower survival and fecundity. As body condition is a 'barometer' of energy demands relative to energy intake, we explored the causes and consequences of variation in body mass of wild female Svalbard reindeer (Rangifer tarandus platyrhynchus) from 1994 to 2015, a period of marked climate warming. Late winter (April) body mass explained 88% of the between-year variation in population growth rate, because it strongly influenced reproductive loss, and hence subsequent fecundity (92%), as well as survival (94%) and recruitment (93%). Autumn (October) body mass affected ovulation rates but did not affect fecundity. April body mass showed no long-term trend (coefficient of variation, CV = 8.8%) and was higher following warm autumn (October) weather, reflecting delays in winter onset, but most strongly, and negatively, related to 'rain-on-snow' events. October body mass (CV = 2.5%) increased over the study due to higher plant productivity in the increasingly warm summers. Density-dependent mass change suggested competition for resources in both winter and summer but was less pronounced in recent years, despite an increasing population size. While continued climate warming is expected to increase the carrying capacity of the high Arctic tundra, it is also likely to cause more frequent icing events. Our analyses suggest that these contrasting effects may cause larger seasonal fluctuations in body mass and vital rates. Overall our findings provide an important 'missing' mechanistic link in the current understanding of the population biology of a

  4. Vertical and temporal dynamics of phytoplanktonic associations and the application of index assembly in tropical semi-arid eutrophic reservoir, northeastern Brazil

    Directory of Open Access Journals (Sweden)

    Pryscila Cynara Soares Vieira

    2015-03-01

    Full Text Available AimTo determine the composition and biomass of functional groups around the vertical and temporal gradient correlated with environmental conditions and apply the index Q in a water-supply reservoir.MethodsWater samples were collected monthly (n = 92 between 2009 and 2011 in two points of the dam for physicochemical and biological analysis.ResultsThe pH, dissolved oxygen and water temperature showed significant differences between the photic and aphotic zones (p<0.05. The vertical variation of dissolved oxygen and water temperature, showed a profile of stratification. The phytoplankton community was represented by 11 functional groups: S1, M, H1, Lo, P, F, SN, J, W2, MP and R.ConclusionsThe vertical variations were less pronounced than the temporal variations in the phytoplankton community. The Q index pointed out poor water quality, corresponding to the current state of eutrophication in the reservoir and it was sensitive to responsive to environmental and hydrodynamic changes in these systems, demonstrating to be an appropriate tool for monitoring and evaluating the quality of water in tropical semi-arid reservoirs.

  5. 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.

  6. Summer 2011

    Directory of Open Access Journals (Sweden)

    Eric G. Strauss

    2011-01-01

    Full Text Available Cities and the Environment Editor, Eric Strauss, provides an introduction to the Summer 2011 issue. He discusses the journal's transition to its new home at Loyola Marymount University and the creation of the Center for Urban Resilience and Ecological Solution, while underscoring highlights of the special topics section on Urban Predators. The contributors to this section participated in the International Symposium on Urban Wildlife and the Environment hosted by the Wildlife Society at the University of Massachusetts Amherst in June of 2009. Finally, Dr. Strauss notes the breadth of our issue by mentioning the additional articles' focus on rain gardens, water quality, arthropod diversity, green roofs, and socio-ecological dynamics.

  7. Seasonal development of phytoplankton populations in offshore Lake Michigan in 1975

    International Nuclear Information System (INIS)

    Parker, J.I.; Conway, H.L.; Yaguchi, E.M.

    1975-01-01

    Relationships between phytoplankton bloom sequences and environmental factors that may account for seasonal variations have not been thoroughly evaluated in Lake Michigan. We investigated the seasonal periodicity of phytoplankton in the offshore water from April to December, 1975. The seasonal distributions of phytoplankton biomass, chlorophyll a, and primary productivity per unit of lake surface area were measured at station 5. These measurements demonstrated a bimodal seasonal distribution, with maxima occurring in June and October. Previous investigators have shown that the seasonal periodicity was unimodal, with a summer maximum. Our observations demonstrated year to year variations in this abundance pattern

  8. 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.

  9. Phytoplankton Identification Manual

    Digital Repository Service at National Institute of Oceanography (India)

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

    . Bacillariophyceae (Diatoms) 6.1 Structure of the diatom cell 6.2 Gross vegetative structure 6.3 Cell division 6.4 Classification of Diatoms 7. Phyrrophyceae (Dinoflagellates) 8. Micrometry 9. Measurement of Biomass 9.1 Chlorophyll measurements 9.2 Cell... counts 9.3 Cell count by drop count method 10. Measurement of productivity 11. Bibliography 1 1. Introduction Phytoplankton (?phyto? = plant; ?planktos? = made to wander) are single celled marine algae, some of which are capable of movement through...

  10. 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...

  11. Phytoplankton in the cooling pond of a nuclear fuel plant. II. Spectral analysis

    International Nuclear Information System (INIS)

    Tokarskaya, Z.B.; Smagin, A.I.; Ryzhkov, E.G.; Nikitina, L.V.

    1995-01-01

    This study continues investigations into the development dynamics of phytoplankton and hydrochemical and meteorological factors over a periods of 26 years in the cooling pond of the Mayak Production Association in the Kyzyl-Trash Lake. The aim is to evaluate the long-term oscillations in phytoplankton owing to changes in hydrochemical and meteorological factors. 6 refs., 2 figs., 1 tab

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

    Directory of Open Access Journals (Sweden)

    K. Fennel

    2011-07-01

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

  13. Controls on summer low flow

    Science.gov (United States)

    Graham, C. B.; McNamara, J. P.

    2012-12-01

    Summer low flow has significant impacts on aquatic flora and fauna, municipal water use, and power generation. However, the controls on the minimum annual summer discharge are complex, including a combination of snowmelt dynamics, summer evapotranspiration demand, and spring, summer precipitation patterns and surface - groundwater interactions. This is especially true in the Rocky Mountain West of the United States, where snowpack provides the majority of water available for spring runoff and groundwater replenishment. In this study, we look at summer low flow conditions at four snow dominated catchments (26 km2 - 2200 km2) in South-central Idaho currently feeling the effects of climate change. Measures of snowmelt dynamics, summer evapotranspiration demand and spring and summer precipitation are used to determine the dominant controls on late summer low flow magnitude, timing and duration. These analyses show that the controls vary between watersheds, with significant implications for the impacts of climate change in snow dominated areas of the Rocky Mountain West.

  14. Seasonal phytoplankton blooms associated with monsoonal influences and coastal environments in the sea areas either side of the Indochina Peninsula

    Science.gov (United States)

    Tang, Dan Ling; Kawamura, Hiroshi; Shi, Ping; Takahashi, Wataru; Guan, Lei; Shimada, Teruhisa; Sakaida, Futoki; Isoguchi, Osamu

    2006-03-01

    The Gulf of Thailand (GoT) is a semienclosed sea on the west and southwest side of the Indochina Peninsula and connects with the near-coastal waters of the South China Sea (SCS) on the east and northeast side of the Malay Peninsula. The objective of the present study is to understand dynamic features of the phytoplankton biology in the GoT and the nearby SCS, on both sides of the Indochina Peninsula, using remote-sensing measurements of chlorophyll-a (Chl a), sea surface temperature (SST), and surface vector winds obtained during the period from September 1997 to March 2003. Results show that seasonal variations of the phytoplankton blooms are primarily controlled by the monsoonal winds and related coastal environments. The GoT and the near-coastal SCS have a peak in the averaged monthly Chl a in December and January, which is associated with the winter northeaster monsoon. The near-coastal SCS have another big peak in the averaged monthly Chl a in summer (July to September), which is associated with the summer southwest monsoon. The offshore bloom in the GoT occurs in its southern part and enhances the December-January peak of averaged monthly Chl a. By contrast, the offshore bloom in the nearby SCS is observed northeast of the Peninsula, and represents the primary source of the July-September peak Chl a. Here the coastal upwelling associated with the offshore Ekman transport caused by the coastal surface winds parallel to the Vietnam east coast gives physical conditions favorable to the development of offshore phytoplankton blooms. The Mekong River discharge waters flow in different directions, depending on the monsoon winds, and contributes to seasonal blooms on both sides of the Peninsula.

  15. The seasonal cycle of mixed layer dynamics and phytoplankton biomass in the Sub-Antarctic Zone: A high-resolution glider experiment

    CSIR Research Space (South Africa)

    Swart, S

    2014-06-01

    Full Text Available -resolution glider data (3 hourly, 2 km horizontal resolution), from~6 months of sampling (spring through summer) in the Sub-Antarctic Zone, is used to assess 1) the different forcing mechanisms driving variability in upper ocean physics and 2) how thesemay...

  16. 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

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

    Data.gov (United States)

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

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

    Science.gov (United States)

    Needham, David M; Fuhrman, Jed A

    2016-02-29

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

  19. Decomposition of lake phytoplankton. 1

    International Nuclear Information System (INIS)

    Hansen, L.; Krog, G.F.; Soendergaard, M.

    1986-01-01

    Short-time (24 h) and long-time (4-6 d) decomposition of phytoplankton cells were investigasted under in situ conditions in four Danish lakes. Carbon-14-labelled, dead algae were exposed to sterile or natural lake water and the dynamics of cell lysis and bacterial utilization of the leached products were followed. The lysis process was dominated by an initial fast water extraction. Within 2 to 4 h from 4 to 34% of the labelled carbon leached from the algal cells. After 24 h from 11 to 43% of the initial particulate carbon was found as dissolved carbon in the experiments with sterile lake water; after 4 to 6 d the leaching was from 67 to 78% of the initial 14 C. The leached compounds were utilized by bacteria. A comparison of the incubations using sterile and natural water showed that a mean of 71% of the lysis products was metabolized by microorganisms within 24 h. In two experiments the uptake rate equalled the leaching rate. (author)

  20. Connecting pigment composition and dissolved trace elements to phytoplankton population in the southern Benguela Upwelling zone (St. Helena Bay)

    Science.gov (United States)

    Das, Supriyo Kumar; Routh, Joyanto; Roychoudhury, Alakendra N.; Veldhuis, Marcel J. W.; Ismail, Hassan E.

    2017-12-01

    Rich in upwelled nutrients, the Southern Benguela is one of the most productive ecosystems in the world ocean. However, despite its ecological significance the role of trace elements influencing phytoplankton population in the Southern Benguela Upwelling System (SBUS) has not been thoroughly investigated. Here, we report pigment composition, macronutrients (nitrate, phosphate and silicate) and concentrations of dissolved Cd, Co, Fe and Zn during late austral summer and winter seasons in 2004 to understand the relationship between the selected trace elements and phytoplankton biomass in St. Helena Bay (SHB), which falls within the southern boundary of the SBUS. Chlorophyll a concentrations indicate higher phytoplankton biomass associated with high primary production during late summer in SHB where high diatom population is inferred from the presence of fucoxanthin. Diminished phytoplankton biomass and a shift from diatoms to dinoflagellates as the dominant phytoplankton taxa are indicated by diagnostic pigments during late winter. Dissolved trace elements (Cd, Co and Zn) and macronutrients play a significant role in phytoplankton biomass, and their distribution is affected by biological uptake and export of trace elements. Continuous uptake of Zn by diatoms may cause an onset of Zn depletion leading to a period of extended diatom proliferation during late summer. Furthermore, the transition from diatom to dinoflagellate dominated phytoplankton population is most likely facilitated by depletion of trace elements (Cd and Co) in the water column.

  1. [Dynamic changes of soil microbial populations and enzyme activities in super-high yielding summer maize farmland soil].

    Science.gov (United States)

    Hou, Peng; Wang, Yong-jun; Wang, Kong-jun; Yang, Jin-sheng; Li, Deng-hai; Dong, Shu-ting; Liu, Jing-guo

    2008-08-01

    To reveal the characteristics of the dynamic changes of soil microbial populations and enzyme activities in super-high yielding ( > 15,000 kg x hm(-2)) summer maize farmland soil, a comparative study was conducted in the experimental fields in National Maize Engineering Research Center (Shandong). On the fields with an annual yield of >15,000 kg x hm(-2) in continuous three years, a plot with the yield of 20 322 kg x hm(-2) (HF) was chosen to make comparison with the conventional farmland (CF) whose maize yield was 8920. 1 kg x hm(-2). The numbers of bacteria, fungi, and actinomycetes as well as the activities of urease and invertase in 0-20 cm soil layer were determined. The results showed that in the growth period of maize, the numbers of bacteria, fungi, and actinomycetes in the two farmland soils increased first and declined then. At the later growth stages of maize, the numbers of soil microbes, especially those of bacteria and actinomycetes, were lower in HF than those in CF. At harvest stage, the ratio of the number of soil bacteria to fungi (B/ F) in HF was 2.03 times higher than that at sowing stage, and 3.02 times higher than that in CF. The B/F in CF had less difference at harvest and sowing stages. The soil urease activity in HF was significantly lower than that in CF at jointing stage, and the invertase activity in HF decreased rapidly after blooming stage, being significantly lower than that in CF.

  2. Impact of wastewater on phytoplankton

    Digital Repository Service at National Institute of Oceanography (India)

    Jaiswar, M.J.R.

    A number of studies on phytoplankton were conducted by National Institute of Oceanography, Goa, India at Thane Creek, Maharashtra, India, Ulhas River estuary, Versova Creek and Mahim Creek under Coastal Ocean Monitoring and Prediction System (COMAPS...

  3. 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.

  4. The effects of combining dynamic pricing, AC load control, and real-time energy feedback. SMUD'S 2011 Residential Summer Solutions Study

    Energy Technology Data Exchange (ETDEWEB)

    Herter, K. [Herter Energy Research Solutions, El Dorado Hills, CA (United States); Wood, V. [Sacramento Municipal Utility District, Sacramento, CA (United States); Blozis, S. [University of California, Davis, CA (United States)

    2013-11-15

    The 2011 Residential Summer Solutions Study compared the hourly load effects of three different real-time information treatments and two program options. The information treatments included: Baseline information (no real-time data), real-time Home information (whole-house data), and real-time Appliance information (data for the whole house plus three individual appliances). Compared to the Baseline group, real-time Home information lowered overall energy use by about 4 %. Real-time information at both the Home and Appliance levels had a significant effect on non-event peak loads: compared to the Baseline group, real-time Home data lowered peak load by 5 %, while Appliance data lowered peak load by 7 %. All three information treatments averaged a 1-kW (40 %) load shed during events. The customer-chosen program options included a dynamic time-of-use rate and a load control incentive program. Customers were more likely to sign up for the dynamic rate, and those who did saved significantly more peak load on both event days (>50 % savings) and non-event days (>20 % savings) than did those on the load control program alone. In addition, those on the dynamic rate saved twice as much on their summer bills as did those who chose to remain on the standard tiered rate. At the end of the summer, more than 90 % of participants signed up to participate again the following year.

  5. The first decade of oligotrophication in Lake Constance : I. The response of phytoplankton biomass and cell size.

    Science.gov (United States)

    Gaedke, Ursula; Schweizer, Anette

    1993-03-01

    Phytoplankton biomass and species composition were measured with a relatively high temporal resolution (once or twice a week during the growing season) from 1979 to 1989 in Lake Constance/Überlingersee. Over this period soluble reactive phosphorus (SRP) concentrations during winter mixing were reduced by ca. 50% from 104 to 47 μg 1 -1 , which caused a prolongation and amplification of the epilimnetic P depletion during the growth period. Seasonal dynamics of phytoplankton reacted to the decrease of SRP in the following ways: (1) Algal biomass decreased at least proportionally to the winter SRP concentrations in summer, but not in spring and autumn when biomass fluctuated irregularly. (2) The peak of biomass concentration changed from summer to spring. (3) The earlier onset of epilimnetic P depletion during the season in recent years promoted a stronger growth of some pennate diatoms in spring. It caused an amplification of the silicon depletion in summer, which may cause still greater reduction of diatoms and total algal biomass in summer. (4) Reduction of algal biomass during the clear-water phase proper became shorter and less pronounced. (5) The temporal variability of algal biomass decreased in summer and autumn but not in spring. (6) Average cell sizes remained unchanged in summer and autumn but increased in spring during the beginning of oligotrophication. These results are largely in agreement with other studies on lake restoration and expectations derived from the PEG (Plankton Ecology Group) model (Sommer et al. 1986). They show that a 50% reduction of SRP concentrations during homothermy may have pronounced effects on seasonal dynamics of algal biomass in a large and deep lake. The algal response to the external change of SRP concentrations can be described by the Le Chatelier principle, implying that the internal structure of the system (e.g. species composition) changes in order to minimize the effect of the external pressure (e.g. reduction of total

  6. 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 ...

  7. 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

  8. 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

  9. Warming accelerates termination of a phytoplankton spring bloom by fungal parasites

    NARCIS (Netherlands)

    Frenken, Thijs; Velthuis, M.; De Senerpont Domis, Lisette; Stephan, Susanne; Aben, Ralf Cornelis; Kosten, S.; van Donk, E.; Van de Waal, D.B.

    2016-01-01

    Climate change is expected to favour infectious diseases across ecosystems worldwide. In freshwater and marine environments, parasites play a crucial role in controlling plankton population dynamics. Infection of phytoplankton populations will cause a transfer of carbon and nutrients into parasites,

  10. Qualitative and quantitative studies on phytoplankton and chlorophyll content in the pelagic water of Lake Żarnowieckie in 1974

    Directory of Open Access Journals (Sweden)

    Józefa Sosnowska

    2015-01-01

    Full Text Available Species composition of phytoplankton, its biomass, share of nannoplankton, and concentration of chlorophyll and pheophytin in phytoplankton and nannoplankton were assessed basing on the materials collected from two pelagic stations of Lakę Żarnowieckie during the period 30 March - 6 December 1974. Average and maximal values of phytoplankton biomass (4-5 and 10-11 mg/1 respectively, as well as the concentration of chlorophyll (1.7 -10.0 μg/l together with pheophytin point to slightly advanced eutrophication of the lake. Share of nannoplankton in total phytoplankton biomass was very low (as a rule below 3% with an increase to 15% only in spring. Relatively slight taxonomic differentiation of phytoplankton (164 taxons, its qualitative composition with the predominance of Cyanophyceae in summer, and of Bacillariophyceae in spring and autumn, as also seasonal succession of algae, point to eutrophic character of the lake.

  11. A Dynamic Analysis of the Role of the Planetary- and Synoptic-Scale in the Summer of 2010 Blocking Episodes over the European Part of Russia

    Directory of Open Access Journals (Sweden)

    Anthony R. Lupo

    2012-01-01

    Full Text Available During the summer of 2010, an unusually persistent blocking episode resulted in anomalously warm dry weather over the European part of Russia. The excessive heat resulted in forest and peat fires, impacted terrestrial ecosystems, greatly increased pollution in urban areas, and increased mortality rates in the region. Using the National Centers for Atmospheric Research (NCAR, National Centers for Environmental Prediction (NCEP reanalysis datasets, the climatological and dynamic character of blocking events for summer 2010 and a precursor May blocking event were examined. We found that these events were stronger and longer lived than typical warm season events. Using dynamic methods, we demonstrate that the July 2010 event was a synoptic-scale dominant blocking event; unusual in the summer season. An analysis of phase diagrams demonstrated that the planetary-scale did not become stable until almost one week after block onset. For all other blocking events studied here and previously, the planetary-scale became stable around onset. Analysis using area integrated regional enstrophy (IRE demonstrated that for the July 2010 event, synoptic-scale IRE increased at block onset. This was similar for the May 2010 event, but different from case studies examined previously that demonstrated the planetary-scale IRE was prominent at block onset.

  12. Phytoplankton growth, dissipation, and succession in estuarine environments. [Chesapeake Bay

    Energy Technology Data Exchange (ETDEWEB)

    Seliger, H H

    1976-01-01

    Two major advances in a study of phytoplankton ecology in the Chesapeake Bay are reported. The annual subsurface transport of a dinoflagellate species (Prorocentrum mariae labouriae) from the mouth of the bay a distance northward of 120 nautical miles to the region of the Bay Bridge was followed. Prorocentrum is a major seasonal dinoflagellate in the Chespeake Bay and annually has been reported to form mahogany tides, dense reddish-brown patches, in the northern bay beginning in late spring and continuing through the summer. Subsequent to this annual appearance the Prorocentrum spread southward and into the western tributary estuaries. The physiological behavioral characteristics of the Prorocentrum were correlated with the physical water movements in the bay. A phytoplankton cage technique for the measurement in situ of the growth rates of natural mixed populations is described. (CH)

  13. Phytoplankton biomass and pigment responses to Fe amendments in the Pine Island and Amundsen polynyas

    NARCIS (Netherlands)

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

    2012-01-01

    Nutrient addition experiments were performed during the austral summer in the Amundsen Sea (Southern Ocean) to investigate the availability of organically bound iron (Fe) to the phytoplankton communities, as well as assess their response to Fe amendment. Changes in autotrophic biomass, pigment

  14. Summer Appendicitis

    African Journals Online (AJOL)

    hanumantp

    The increasing number of “fast food” restaurants where mainly high‑carbohydrate ... factors, food culture and the effect of migration for touristic purposes during the summer. .... Lal A, Hales S, French N, Baker MG. Seasonality in human.

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

    African Journals Online (AJOL)

    USER

    2007-03-20

    Mar 20, 2007 ... distribution of phytoplankton species were also determined. Phytoplankton classes ... could have a significant impact on water quality. (Carpenter and Kitchell ..... Environmental Impact assessment Report on proposed Shagari ...

  16. Summer cooling in the east central Arabian Sea - a process of dynamic response to the southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    RameshBabu, V.; Sastry, J.S.

    The cooling of the east central Arabian Sea during summer monsoon season is examined using data sets of MONEX '79 and MONSOON '77 programmes. These studies have revealed that downward transfer of heat due to the mixing of warm surface and cold sub...

  17. Interactions of phytoplankton, zooplankton and microorganisms

    Science.gov (United States)

    Pomeroy, L. R.; Paffenhöfer, G.-A.; Yoder, J. A.

    We present evidence that there are significant interactions between heterotrophic microorganisms, doliolids and Fritillaria within intrusions of nutrient-rich Gulf Stream water stranding on the continental shelf. During the summer of 1981 cold, nutrient-rich water from below the surface of the Gulf Stream was repeatedly intruded and stranded on the continental shelf off northeastern Florida. On August 6 old, stranded Gulf Stream water depleted of nitrate occupied the lower layer on the outer shelf. The upper water was continental shelf water, older but of undefined age. On August 6 free-living bacteria were >10 6ml -1 everywhere at all depths, an order of magnitude greater than normal bacterial numbers on the northeastern Florida continental shelf. Over 10 days the numbers of free bacteria doubled while bacteria attached to particles increased by a factor of four. The adenylate/chlorophyll ratio showed that phytoplankton dominated the lower layers of intruded water, while the surface water became increasingly dominated by heterotrophic microorganisms (bacteria and protozoa) over 10 days. There were significant, negative correlations between bacteria and doliolids and between bacteria and Fritillaria. Regions of maximum bacterial numbers did not coincide with locations of salp swarms. The increased numbers of bacteria at all depths in a highly stratified system in which most phytoplankton are in the lower layer suggests a diverse source of bacterial growth substrates, some of which involve zooplankton as intermediaries. Production of autotrophs is more than twice that of microheterotrophs on average, but because of their differential distribution, microheterotrophs are the dominant biomass in much of the surface water and may be significant in energy flux to metazoan consumers as well as competitors for mutually useable sources of nutrition.

  18. 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

  19. Response patterns of phytoplankton growth to variations in resuspension in the German Bight revealed by daily MERIS data in 2003 and 2004

    Directory of Open Access Journals (Sweden)

    Jian Su

    2015-10-01

    Full Text Available Chlorophyll (chl a concentration in coastal seas exhibits variability on various spatial and temporal scales. Resuspension of particulate matter can somewhat limit algal growth, but can also enhance productivity because of the intrusion of nutrient-rich pore water from sediments or bottom water layers into the whole water column. This study investigates whether characteristic changes in net phytoplankton growth can be directly linked to resuspension events within the German Bight. Satellite-derived chl a were used to derive spatial patterns of net rates of chl a increase/decrease (NR in 2003 and 2004. Spatial correlations between NR and mean water column irradiance were analysed. High correlations in space and time were found in most areas of the German Bight (R2 > 0.4, suggesting a tight coupling between light availability and algal growth during spring. These correlations were reduced within a distinct zone in the transition between shallow coastal areas and deeper offshore waters. In summer and autumn, a mismatch was found between phytoplankton blooms (chl a > 6 mg m−3 and spring-tidal induced resuspension events as indicated by bottom velocity, suggesting that there is no phytoplankton resuspension during spring tides. It is instead proposed here that frequent and recurrent spring-tidal resuspension events enhance algal growth by supplying remineralized nutrients. This hypothesis is corroborated by a lag correlation analysis between resuspension events and in-situ measured nutrient concentrations. This study outlines seasonally different patterns in phytoplankton productivity in response to variations in resuspension, which can serve as a reference for modelling coastal ecosystem dynamics.

  20. Spatio-temporal dynamics of phytoplankton and primary production in Lake Tanganyika using a MODIS based bio-optical time series

    DEFF Research Database (Denmark)

    Bergamino, N; Horion, Stéphanie; Stenuite, S

    2010-01-01

    dynamics throughout the lake. In the present work, daily MODIS-AQUA satellite measurements were used to estimate chlorophyll-a concentrations and the diffuse attenuation coefficient (K490) for surface waters. The spatial regionalisation of Lake Tanganyika, based on Empirical Orthogonal Functions...

  1. Atlantic advection driven changes in glacial meltwater: Effects on phytoplankton chlorophyll-a and taxonomic composition in Kongsfjorden, Spitsbergen.

    NARCIS (Netherlands)

    van de Poll, Willem; Maat, Douwe S.; Fischer, Philipp; Rozema, Patrick; Daly, Oonagh; Koppelle, Sebastiaan; Visser, Ronald; Buma, Anita

    2016-01-01

    Phytoplankton biomass and composition was investigated in a high Arctic fjord (Kongsfjorden, 79°N, 11°40′E) using year round weekly pigment samples collected from October 2013 to December 2014. In addition, phytoplankton dynamics supplemented with physical and chemical characteristics of the 2014

  2. Seasonality in Abundance, Biomass and Production of the Phytoplankton of Welala and Shesher Wetlands, Lake Tana Sub-Basin (Ethiopia)

    NARCIS (Netherlands)

    Wondmagegne, K.; Wondie, A.; Mingist, M.; Vijverberg, J.

    2012-01-01

    The species composition and production of the phytoplankton community of the Shesher and Welala floodplain Wetlands, on the eastern side of Lake Tana, were studied during four seasons from July 2009 to May 2010. We investigated the spatial and temporal dynamics of phytoplankton, densities, biomass,

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

    Directory of Open Access Journals (Sweden)

    Alessandro OGGIONI

    2006-02-01

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

  4. 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.

  5. Phytoplankton distribution and their relationship to environmental variables in Sanya Bay, South China Sea

    Directory of Open Access Journals (Sweden)

    Yanying Zhang

    2010-11-01

    Full Text Available Phytoplankton quantification was conducted in Sanya Bay from January 2005 to February 2006. A submersible in situ spectrofluorometer, which permits the differentiation of four algal groups (green algae, diatoms and dinoflagellates, cryptophytes and cyanobacteria was used. Seasonal variation of total chlorophyll a concentration showed that high value appeared in summer and low concentration occurred in spring. Diatoms and dinoflagellates group was the predominant phytoplankton all year in the Bay. The stable stratification of phytoplankton vertical distribution came into being in July. During the stratification event, the total chlorophyll a concentration of deep layer was much higher than the surface; cyanobacteria and cryptophyta groups decreased and almost disappeared, however, the concentration of green algae and diatoms and dinoflagellates groups increased. In deep layer, the concentration of diatoms and dinoflagellates group increased sharply, which was about eight times more than that in the surface layer. The vertical profiles character of phytoplankton showed that from inshore stations to outer bay the stratification of phytoplankton vertical distribution gradually strengthened. Dissolved inorganic nutrient especially phosphate and inorganic nitrogen and cold-water upwelling were the main regulating factor for phytoplankton distribution.

  6. Role of Delay on Planktonic Ecosystem in the Presence of a Toxic Producing Phytoplankton

    Directory of Open Access Journals (Sweden)

    Swati Khare

    2011-01-01

    Full Text Available A mathematical model is proposed to study the role of distributed delay on plankton ecosystem in the presence of a toxic producing phytoplankton. The model includes three state variables, namely, nutrient concentration, phytoplankton biomass, and zooplankton biomass. The release of toxic substance by phytoplankton species reduces the growth of zooplankton and this plays an important role in plankton dynamics. In this paper, we introduce a delay (time-lag in the digestion of nutrient by phytoplankton. The stability analysis of all the feasible equilibria are studied and the existence of Hopf-bifurcation for the interior equilibrium of the system is explored. From the above analysis, we observe that the supply rate of nutrient and delay parameter play important role in changing the dynamical behaviour of the underlying system. Further, we have derived the explicit algorithm which determines the direction and the stability of Hopf-bifurcation solution. Finally, numerical simulation is carried out to support the theoretical result.

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

    Directory of Open Access Journals (Sweden)

    Oscar Schofield

    2015-10-01

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

  8. 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.

  9. Phytoplankton growth, dissipation, and succession in estuarine environments. Renewal proposal and annual summary report, August 1, 1977--July 31, 1978

    Energy Technology Data Exchange (ETDEWEB)

    Seliger, H H

    1978-01-01

    The directions of the research program in understanding the dynamics of the natural phytoplankton populations of the Chesapeake Bay, the methodology, the statistical analysis, and the description of the system are parallel to the requirements for environmental impact studies. Results are reported for the following studies: development of instrumentation and the synoptic isopleth methodology for relating the dynamic distributions of natural phytoplankton populations to water circulation patterns; phytoplankton cage experiments for assessment of nutrient dynamics; sub-lethal concentrations and effects of polycyclic aromatic hydrocarbons; and studies on concentration and time kinetics of induction of liver aryl hydrocarbon hydroxylase system in Fundulus heteroclitus by benzopyrene and 3-methyl cholanthrene. (HLW)

  10. Physiological ecology of SRS Carolina bay phytoplankton communities: Effects of nutrient changes and CO2 sources

    International Nuclear Information System (INIS)

    Williams, J.B.

    1992-11-01

    Impacts of land-use activities on wetland ecosystems are important issues for environmental planners, conservation groups, and government agencies. The progress report of this project at DOE's Savannah River Site focused on two specific objectives: determination of the effects of nutrient enrichment (fertilizing during wetlands restoration) on phytoplankton communities and comparison of phytoplankton community dynamics during the current extended hydroperiod for Carolina Bays with patterns in previous drier years

  11. 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.

  12. 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.

  13. 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.

  14. Population dynamics of toxic phytoplankton and bacterial flora in the waters of the low Adriatic sea; Dinamica di popolazione di fitoplancton tossico e flora batterica nel basso Adriatico

    Energy Technology Data Exchange (ETDEWEB)

    Caroppo, C.; Stabili, L.; Cavallo, R.A.; Pastore, M. [CNR, Ist. Sperimentale Talassografico Attlio Cerruti, Taranto (Italy); Marchiori, E. [Rome Univ., Rome (Italy). Dipt. di Chimica Organica; Bruno, M. [Istituto Superiore di Sanita' , Laboratorio di Igiene Ambientale, Rome (Italy)

    2000-07-01

    The coastal areas of the Southern Adriatic Sea, in particular the Apulian ones, may be considered an example of intact ecosystem and represent an ideal term of comparison to other marine ecosystems having higher levels of pollution (Northern Adriatic Sea). In order to evaluate the sanitary levels of this environment, four transect were investigated during two years monitoring (April 1995-March 1997) along the Otranto Channel coasts, by joint research groups of the Environmental Hygiene Laboratory of the Istituto Superiore di Sanita' and the Istituto Sperimentale Talassografico A. Cerruti of CNR in Taranto. The study underlines the phytoplanktic and bacterial population dynamics, and the detection of the microbiological water quality along the coast tract Brindisi-Lecce-Otranto-S. Maria di Leuca. The results acquired pointed out population dynamics of some potantially toxic species of Dinophysis genus and Pseudo-nitzschia delicatissima. These depended on the winter nutrient loads due to the ASW (Adriatic Superficial Waters) and to the LIW (Levantine Intermediate Waters). The bacterial community was mainly constituted by genera Aeromonas, Photobacterium, Cytophaga and Pseudomonas. Also the presence of Enterobacteriaceae family was relevant. Among the pathogenic vibrios the most frequently isolated species were Vibrio alginolyticus and Vibrio vulnificus. [Italian] Considerando che le zone del basso Adriatico, in particolare quelle pugliesi, costituiscono un biotopo ancora relativamente inalterato, esse sono state oggetto di un'indagine sperimentale condotta in 24 mesi di attivita' (aprile 1995-marzo 1997) lungo le coste del Canale di Otranto, ad opera di un gruppo congiunto del Laboratorio di Igiene Ambientale dell'Istituto Superiore di Sanita' e dei laboratori dell'Istituto Sperimentale Talassografico A. Cerruti del CNR di Taranto, ai fini di valutare lo stato di salute di questo ambiente, che fornisce, con buona probabilita', un

  15. The light absorption by suspended particles, phytoplankton and dissolved organic matter in deep-and coastal waiters of the Black Sea impact on algorithms for remote sensing of chlorophyll -a-.

    Science.gov (United States)

    Churilova, T.; Suslin, V.; Berseneva, G.; Georgieva, L.

    At present time for the analysis and prediction of marine ecosystem state Chlorophyll and Primary production models based on optical satellite data are widely used. However, the SeaWiFS algorithms providing the transformation of color images to chlorophyll maps give inaccurate estimation of chlorophyll "a" (Chl "a") concentration in the Black Sea - an overestimation approximately two times in summer and an underestimation - ~1,5 times during the large diatom bloom in winter-spring. A development of the regional Chl "a" algorithm requires an estimation of spectral characteristics of all light absorbing components and their relationships with Chl "a" concentration. With this aim bio-optical monitoring was organized in two fixed stations in deep-water central western part of the Black Sea and in shelf waters near the Crimea. The weekly monitoring in deep-waters region allowed to determine phytoplankton community succession: seasonal dynamics of size and taxonomic structure, development of large diatoms blooming in March and coccolithophores - in June. The significant variability in pigment concentration and species content of phytoplankton is accompanied by high variability in shape of the phytoplankton absorption spectra and in values of chl a-specific absorption coefficients. This variability had seasonal character depending mostly on the optical status of phytoplankton cells and partly on taxonomic structure of phytoplankton. The pigment packaging parameter fluctuated from 0.64-0.68 (October-December) to 0.95-0.97 (April-May). The package effect depended on intracellular pigment concentration and the size and geometry of cells, which change significantly over the year, because of extremely different environmental conditions. The relationships between phytoplankton specific absorption coefficients (at 412, 443, 490, 510, 555, 678 nm) and Chl "a" concentration have been described by power functions. The contribution of detritus to total particulate absorption

  16. A stochastic analysis for a phytoplankton-zooplankton model

    International Nuclear Information System (INIS)

    Ge, G; Wang, H-L; Xu, J

    2008-01-01

    A simple phytoplankton-zooplankton nonlinear dynamical model was proposed to study the coexistence of all the species and a Hopf bifurcation was observed. In order to study the effect of environmental robustness on this system, we have stochastically perturbed the system with respect to white noise around its positive interior equilibrium. We have observed that the system remains stochastically stable around the positive equilibrium for same parametric values in the deterministic situation

  17. Spatio-temporal interdependence of bacteria and phytoplankton during a Baltic Sea spring bloom

    Directory of Open Access Journals (Sweden)

    Carina eBunse

    2016-04-01

    Full Text Available In temperate systems, phytoplankton spring blooms deplete inorganic nutrients and are major sources of organic matter for the microbial loop. In response to phytoplankton exudates and environmental factors, heterotrophic microbial communities are highly dynamic and change their abundance and composition both on spatial and temporal scales. Yet, most of our understanding about these processes comes from laboratory model organism studies, mesocosm experiments or single temporal transects. Spatial-temporal studies examining interactions of phytoplankton blooms and bacterioplankton community composition and function, though being highly informative, are scarce. In this study, pelagic microbial community dynamics (bacteria and phytoplankton and environmental variables were monitored during a spring bloom across the Baltic Proper (two cruises between North Germany to Gulf of Finland. To test to what extent bacterioplankton community composition relates to the spring bloom, we used next generation amplicon sequencing of the 16S rRNA gene, phytoplankton diversity analysis based on microscopy counts and population genotyping of the dominating diatom Skeletonema marinoi. Several phytoplankton bloom related and environmental variables were identified to influence bacterial community composition. Members of Bacteroidetes and Alphaproteobacteria dominated the bacterial community composition but the bacterial groups showed no apparent correlation with direct bloom related variables. The less abundant bacterial phyla Actinobacteria, Planctomycetes, and Verrucomicrobia, on the other hand, were strongly associated with phytoplankton biomass, diatom:dinoflagellate ratio and colored dissolved organic matter (cDOM. Many bacterial operational taxonomic units (OTUs showed high niche specificities. For example, particular Bacteroidetes OTUs were associated with two distinct genetic clusters of S. marinoi. Our study revealed the complexity of interactions of bacterial

  18. Recurrent daily rainfall patterns over South Africa and associated dynamics during the core of the austral summer

    CSIR Research Space (South Africa)

    Cretat, J

    2010-12-01

    Full Text Available field instead of atmospheric processes and dynamics. An original agglomerative hierarchical clustering approach is used to classify daily rainfall patterns recorded at 5352 stations from DJF 1971 to DJF 1999. Five clusters are retained for analysis...

  19. Phytoplankton phenology indices in coral reef ecosystems: Application to ocean-color observations in the Red Sea

    KAUST Repository

    Racault, Marie-Fanny

    2015-02-18

    Phytoplankton, at the base of the marine food web, represent a fundamental food source in coral reef ecosystems. The timing (phenology) and magnitude of the phytoplankton biomass are major determinants of trophic interactions. The Red Sea is one of the warmest and most saline basins in the world, characterized by an arid tropical climate regulated by the monsoon. These extreme conditions are particularly challenging for marine life. Phytoplankton phenological indices provide objective and quantitative metrics to characterize phytoplankton seasonality. The indices i.e. timings of initiation, peak, termination and duration are estimated here using 15 years (1997–2012) of remote sensing ocean-color data from the European Space Agency (ESA) Climate Change Initiative project (OC-CCI) in the entire Red Sea basin. The OC-CCI product, comprising merged and bias-corrected observations from three independent ocean-color sensors (SeaWiFS, MODIS and MERIS), and processed using the POLYMER algorithm (MERIS period), shows a significant increase in chlorophyll data coverage, especially in the southern Red Sea during the months of summer NW monsoon. In open and reef-bound coastal waters, the performance of OC-CCI chlorophyll data is shown to be comparable with the performance of other standard chlorophyll products for the global oceans. These features have permitted us to investigate phytoplankton phenology in the entire Red Sea basin, and during both winter SE monsoon and summer NW monsoon periods. The phenological indices are estimated in the four open water provinces of the basin, and further examined at six coral reef complexes of particular socio-economic importance in the Red Sea, including Siyal Islands, Sharm El Sheikh, Al Wajh bank, Thuwal reefs, Al Lith reefs and Farasan Islands. Most of the open and deeper waters of the basin show an apparent higher chlorophyll concentration and longer duration of phytoplankton growth during the winter period (relative to the summer

  20. Effects of N and P enrichment on competition between phytoplankton and benthic algae in shallow lakes: a mesocosm study.

    Science.gov (United States)

    Zhang, Xiufeng; Mei, Xueying; Gulati, Ramesh D; Liu, Zhengwen

    2015-03-01

    Competition for resources between coexisting phytoplankton and benthic algae, but with different habitats and roles in functioning of lake ecosystems, profoundly affects dynamics of shallow lakes in the process of eutrophication. An experiment was conducted to test the hypothesis that combined enrichment with nitrogen (N) and phosphorus (P) would be a greater benefit to phytoplankton than benthic algae. The growth of phytoplankton and benthic algae was measured as chlorophyll a (Chl a) in 12 shallow aquatic mesocosms supplemented with N, P, or both. We found that enrichment with N enhanced growth of benthic algae, but not phytoplankton. P enrichment had a negative effect on benthic algal growth, and no effect on the growth of phytoplankton. N+P enrichment had a negative effect on benthic algae, but enhanced the growth of phytoplankton, thus reducing the proportion of benthic algae contributing to the combined biomass of these two groups of primary producers. Thus, combined N+P enrichment is more favorable to phytoplankton in competition with benthic algae than enrichment with either N or P alone. Our study indicates that combined enrichment with N+P promotes the dominance of phytoplankton over benthic algae, with consequences for the trophic dynamics of shallow lake ecosystems.

  1. 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.

  2. 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 nutritiona......-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....

  3. 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

  4. Climate dynamics of South America during summer: Connections between the large-scale circulation and regional precipitation

    Science.gov (United States)

    Lenters, Johh Derick

    1997-05-01

    Relationships between the large-scale circulation and regional precipitation over South America during austral summer are examined using a GCM, linear model, and observational analyses. Emphasis is placed on understanding the origin of upper-tropospheric circulation features such as the Bolivian high and its effects on South American precipitation variability, particularly on the Central Andean Altiplano. Results from the linear model indicate that the Bolivian high and 'Nordeste low' are generated in response to precipitation over the Amazon basin, Central Andes, and South Atlantic convergence zone (SACZ), with African precipitation also playing a crucial role in the formation of the low. The direct mechanical and sensible heating effects of the Andes are minimal, acting only to induce a weak lee trough in midlatitudes and a shallow monsoonal circulation over the Central Andes. In the GCM the effects of the Andes include a strengthening of the Bolivian high and northward shift of the Nordeste low, primarily through changes in the precipitation field. The position of the Bolivian high is primarily determined by Amazonian precipitation and is little affected by the removal of the Andes. Strong subsidence to the west of the high is found to be important for the maintenance of the high's warm core, while large-scale convective overshooting to the east is responsible for a layer of cold air above the high. Observations from eight summer seasons reveal a close relationship between precipitation variability in the Central Andes and the position and intensity of the Bolivian high. The physical mechanisms of this connection are explored using composite, EOF, and correlation techniques. On intraseasonal to interannual timescales, rainy episodes on the Altiplano are found to be associated with warm, moist, poleward flow along the eastern flank of the Andes, often in conjunction with extratropical disturbances and a westward displacement of the SACZ. Corresponding to this

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

    Digital Repository Service at National Institute of Oceanography (India)

    Jayalakshmy, K.V.

    and temperature, zooplankton and phytoplankton, zooplankton and PO sub(4)-P and phytoplankton and PO sub(4)-P. Linear regression model is found to be significant at 1% level of significance. Since zooplankton and phytoplankton are significantly positively...

  6. Variation of phytoplankton functional groups modulated by hydraulic controls in Hongze Lake, China.

    Science.gov (United States)

    Tian, Chang; Pei, Haiyan; Hu, Wenrong; Hao, Daping; Doblin, Martina A; Ren, Ying; Wei, Jielin; Feng, Yawei

    2015-11-01

    Hongze Lake is a large, shallow, polymictic, eutrophic lake in the eastern China. Phytoplankton functional groups in this lake were investigated from March 2011 to February 2013, and a comparison was made between the eastern, western, and northern regions. The lake shows strong fluctuations in water level caused by monsoon rains and regular hydraulic controls. By application of the phytoplankton functional group approach, this study aims to investigate the spatial and temporal dynamics and analyze their influencing factors. Altogether, 18 functional groups of phytoplankton were identified, encompassing 187 species. In order to seek the best variable describing the phytoplankton functional group distribution, 14 of the groups were analyzed in detail using redundancy analysis. Due to the turbid condition of the lake, the dominant functional groups were those tolerant of low light. The predominant functional groups in the annual succession were D (Cyclotella spp. and Synedra acus), T (Planctonema lauterbornii), P (Fragilaria crotonensis), X1 (Chlorella vulgaris and Chlorella pyrenoidosa), C (Cyclotella meneghiniana and Cyclotella ocellata), and Y (Cryptomonas erosa). An opposite relationship between water level and the biomass of predominant groups was observed in the present study. Water level fluctuations, caused by monsoonal climate and artificial drawdown, were significant factors influencing phytoplankton succession in Hongze Lake, since they alter the hydrological conditions and influence light and nutrient availability. The clearly demonstrated factors, which significantly influence phytoplankton dynamics in Hongze Lake, will help government manage the large shallow lakes with frequent water level fluctuations.

  7. Influence of a large late summer precipitation event on food limitation and grasshopper population dynamics in a northern Great Plains grassland.

    Science.gov (United States)

    Branson, David H

    2008-06-01

    The complex interplay between grasshoppers, weather conditions, and plants that cause fluctuations in grasshopper populations remains poorly understood, and little is known about the ecological processes that generate grasshopper outbreaks. Grasshopper populations respond to interacting extrinsic and intrinsic factors, with yearly and decadal weather patterns and the timing of precipitation all potentially important. The effects of initial and increasing grasshopper densities on grasshopper survival and reproductive correlates were examined at a northern mixed-grass prairie site through manipulations of grasshopper densities inside 10-m2 cages. High-quality grass growth occurred after a 9.1-cm mid-August rain. Reduced proportional survival was apparent in the two higher density treatments before the rain, indicative of food-limited density-dependent mortality. However, the large late summer rainfall event mediated the effects of exploitative competition on demographic characteristics because of the high-quality vegetation growth. This led to weaker effects of food limitation on survival and reproduction at the end of the experiment. The results indicate a direct link between weather variation, resource quality and grasshopper population dynamics led to a severe grasshopper outbreak and show that infrequent large precipitation events can have significant effects on population dynamics. Additional research is needed to examine the importance of infrequent large precipitation events on grasshopper population dynamics in grassland ecosystems.

  8. Combined analysis of field and model data: A case study of the phosphate dynamics in the German Bight in summer 1994

    Science.gov (United States)

    Pohlmann, Th.; Raabe, Th.; Doerffer, R.; Beddig, S.; Brockmann, U.; Dick, S.; Engel, M.; Hesse, K.-J.; König, P.; Mayer, B.; Moll, A.; Murphy, D.; Puls, W.; Rick, H.-J.; Schmidt-Nia, R.; Schönfeld, W.; Sündermann, J.

    1999-09-01

    The intention of this paper is to analyse a specific phenomenon observed during the KUSTOS campaigns in order to demonstrate the general capability of the KUSTOS and TRANSWATT approach, i.e. the combination of field and modelling activities in an interdisciplinary framework. The selected phenomenon is the increase in phosphate concentrations off the peninsula of Eiderstedt on the North Frisian coast sampled during four subsequent station grids of the KUSTOS summer campaign in 1994. First of all, a characterisation of the observed summer situation is given. The phosphate increase is described in detail in relation to the dynamics of other nutrients. In a second step, a first-order estimate of the dispersion of phosphate is discussed. The estimate is based on the box model approach and will focus on the effects of the river Elbe and Wadden Sea inputs on phosphate dynamics. Thirdly, a fully three-dimensional model system is presented, which was implemented in order to analyse the phosphate development. The model system is discussed briefly, with emphasis on phosphorus-related processes. The reliability of one of the model components, i.e. the hydrodynamical model, is demonstrated by means of a comparison of model results with observed current data. Thereafter, results of the German Bight seston model are employed to interpret the observed phosphate increase. From this combined analysis, it was possible to conclude that the phosphate increase during the first three surveys was due to internal transformation processes within the phosphorus cycle. On the other hand, the higher phosphate concentrations measured in the last station grid survey were caused by a horizontal transport of phosphate being remobilised in the Wadden Sea.

  9. Summer Students

    CERN Multimedia

    2005-01-01

    SUMMER STUDENT LECTURE PROGRAMME Main Auditorium, bldg. 500 DATE TIME LECTURER TITLE Wednesday 6 July 09:15 - 10:00 F. CERUTTI (CERN) Presentation of the Summer Student Programme D. Heagerty (CERN) Computer rules O. ULLALAND (CERN) Workshops presentation 10:15 - 11:00 D. SCHLATTER (CERN) Introduction to CERN 11:15 Film on CERN Thursday 7 July 09:15 - 11:00 L. Di Lella (CERN) Introduction to Particle Physics (1-2/4) 11:15 - 12:00 P. Chomaz (GANIL / CERN) Introduction to Nuclear Physics (1/3) 12:00 Discussion Session 14:00 - 14:45 M. Lindroos (CERN) ISOLDE Facility 15:00 M. Lindroos (CERN) ISOLDE Visit Friday 8 July 09:15 - 10:00 L. Di Lella (CERN) Introduction to Particle Physics (3/4) 10:15 - 11:00 P. Chomaz (GANIL / CERN) Introduction to Nuclear Physics (2/3) 11:15 - 12:00 G. ROLANDI (CERN) How an experiment is designed (1/2) 12:00 Discussion Session Monday 11 July 09:15 - 10:00 L. Di Lella (CERN) Introduction to Particle Physi...

  10. Dynamical linkage of tropical and subtropical weather systems to the intraseasonal oscillations of the Indian summer monsoon rainfall. Part II: Simulations in the ENSEMBLES project

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Shujie [Institut Catala de Ciencies del Clima (IC3), Barcelona, Catalonia (Spain); Rodo, Xavier [Institut Catala de Ciencies del Clima (IC3), Barcelona, Catalonia (Spain); Institut Catala de Recerca i Estudis Avancats (ICREA), Barcelona, Catalonia (Spain); Song, Yongjia [Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States); Cash, Benjamin A. [Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States)

    2012-09-15

    We assess the ability of individual models (single-model ensembles) and the multi-model ensemble (MME) in the European Union-funded ENSEMBLES project to simulate the intraseasonal oscillations (ISOs; specifically in 10-20-day and 30-50-day frequency bands) of the Indian summer monsoon rainfall (ISMR) over the Western Ghats (WG) and the Bay of Bengal (BoB), respectively. This assessment is made on the basis of the dynamical linkages identified from the analysis of observations in a companion study to this work. In general, all models show reasonable skill in simulating the active and break cycles of the 30-50-day ISOs over the Indian summer monsoon region. This skill is closely associated with the proper reproduction of both the northward propagation of the intertropical convergence zone (ITCZ) and the variations of monsoon circulation in this band. However, the models do not manage to correctly simulate the eastward propagation of the 30-50-day ISOs in the western/central tropical Pacific and the eastward extension of the ITCZ in a northwest to southeast tilt. This limitation is closely associated with a limited capacity of models to accurately reproduce the magnitudes of intraseasonal anomalies of both the ITCZ in the Asian tropical summer monsoon regions and trade winds in the tropical Pacific. Poor reproduction of the activity of the western Pacific subtropical high on intraseasonal time scales also amplify this limitation. Conversely, the models make good reproduction of the WG 10-20-day ISOs. This success is closely related to good performance of the models in the representation of the northward propagation of the ITCZ, which is partially promoted by local air-sea interactions in the Indian Ocean in this higher-frequency band. Although the feature of westward propagation is generally represented in the simulated BoB 10-20-day ISOs, the air-sea interactions in the Indian Ocean are spuriously active in the models. This leads to active WG rainfall, which is not

  11. 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; Vardi, Assaf

    2015-01-01

    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. PMID:25964340

  12. Spatial and temporal patterns of phytoplankton composition in Burullus Lagoon, Southern Mediterranean Coast, Egypt

    Directory of Open Access Journals (Sweden)

    Mohamed Zein Alabedin Nassar

    2014-01-01

    Full Text Available Burullus Lagoon is a shallow, turbid, and nutrient replete system, suffering from high level of aquatic plants, expansion in fish farming and agricultural drainage discharges. Phytoplankton was evaluated based on four years monitoring seasonally from summer 2009 to spring 2013 at 12 stations representing the eastern, central and western basins of the lagoon. Over the 4-year study period, a total of 283 taxa from 96 genera and eight classes were recorded. The lagoon showed a pronounced algal periodicity. Phytoplankton community was generally dominated by Chlorophyceae, Bacillariophyceae and Cyanobacteria. The western basin had the lowest mean salinity values and highest phytoplankton abundance, in which, blooms of Chlorophyceae, Bacillariophyceae and Cyanobacteria were common. The eastern basin had lowest phytoplankton density and chlorophytes were dominant followed by Bacillariophyceae and/or Cyanobacteria. Euglenophyceae strongly appeared in the eastern basin especially at the second station, which is located in front of El Burullus Drain. The central basin is subjecting to high loading of phosphorus and nitrogen from agricultural drains and had a prevalence of chlorophyte blooms which constituted more than 50% of the total abundance. This study has provided substantial evidence that the phytoplankton abundance and community are governed by the environmental conditions which vary each year, so does the phytoplankton seasonal succession. Generally, about 25-50% reduction was recorded in the phytoplankton densities between 2009 and 2013 and a dramatic decrease in the abundance of many nuisance and eutrophic species was evident. No sign of eutrophication was observed, and recession of Cyanobacteria blooming suggests a major improvement in the water quality of Burullus Lagoon.

  13. 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

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

    Directory of Open Access Journals (Sweden)

    Alexandra Coello-Camba

    2017-06-01

    Full Text Available 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

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

    KAUST Repository

    Coello-Camba, Alexandra; Agusti, Susana

    2017-01-01

    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

  16. Key role of organic complexation of iron in sustaining phytoplankton blooms in the Pine Island and Amundsen Polynyas (Southern Ocean)

    NARCIS (Netherlands)

    Thuroczy, Charles-Edouard; Alderkamp, Anne-Carlijn; Laan, Patrick; Gerringa, Loes J. A.; Mills, Matthew M.; Van Dijken, Gert L.; De Baar, Hein J. W.; Arrigo, Kevin R.

    2012-01-01

    Primary productivity in the Amundsen Sea (Southern Ocean) is among the highest in Antarctica. The summer phytoplankton bloom in 2009 lasted for > 70 days in both the Pine Island and Amundsen Polynyas. Such productive blooms require a large supply of nutrients, including the trace metal iron (Fe).

  17. Phytoplankton chlorophyll a biomass, composition, and productivity along a temperature and stratification gradient in the northeast Atlantic Ocean

    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° N in the northeast Atlantic

  18. Phytoplankton chlorophyll a biomass, composition, and productivity along a temperature and stratification gradient in the northeast Atlantic Ocean

    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

  19. Macroecological patterns in the distribution of marine phytoplankton

    DEFF Research Database (Denmark)

    Mousing, Erik Askov

    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...... production, biochemical cycling and have a direct impact on the global carbon cycle through the biological pump. Understanding the processes controlling phytoplankton primary production and community composition at the global scale and how these interact with climate change are, therefore, imperative...... to in situ abiotic conditions (primarily temperature, salinity, mixed layer dynamics and ambient nutrient concentrations) in order to elucidate the primary bottom-up processes that control phytoplankton communities. In order to do this, I investigate and present several data sets that have been assembled...

  20. Iron availability, nitrate uptake, and exportable new production in the subarctic Pacific. [phytoplankton population growth support and atmospheric CO2 removal

    Science.gov (United States)

    Banse, Karl

    1991-01-01

    This paper presents a critique of experimental data and papers by Martin et al. (1989, 1990), who suggested that the phytoplankton growth is iron-limited and that, small additions of iron to large subarctic ocean areas might be a way of removing significant amounts of atmospheric CO2 by increasing phytoplancton growth. Data are presented to show that, in the summer of 1987, the phytoplankton assemblage as a whole was not iron limited, as measured by the bulk removal of nitrate or by the increase of chlorophyll. It is suggested that grazing normally prevents the phytoplankton from reaching concentrations that reduce the iron (and nitrate) to levels that depress division rates drastically.

  1. Competition for light between phytoplankton species : Experimental tests of mechanistic theory

    NARCIS (Netherlands)

    Huisman, J.; Jonker, R.R.; Zonneveld, C.; Weissing, F.J.

    1999-01-01

    According to recent competition theory, the population dynamics of phytoplankton species in monoculture can be used to make a priori predictions of the dynamics and outcome of competition for light. The species with lowest "critical light intensity" should be the superior light competitor. To test

  2. Dual character of Sundarban estuary as a source and sink of CO2 during summer: an investigation of spatial dynamics.

    Science.gov (United States)

    Akhand, Anirban; Chanda, Abhra; Dutta, Sachinandan; Manna, Sudip; Sanyal, Pranabes; Hazra, Sugata; Rao, K H; Dadhwal, V K

    2013-08-01

    A comprehensive attempt has been made to evaluate the diurnal and spatial pattern of CO2 exchange between the atmosphere and water along the estuarine track of Indian Sundarbans during the two summer months, April and May, 2011. Rigorous field observations were carried out which included the hourly measurements of total alkalinity, pH, fugacity of CO2 in ambient air and water surface, dissolved oxygen, and chlorophyll a. The estuarine water was found rich in total alkalinity and was oversaturated with CO2 throughout the diurnal cycle in the two stations situated at the inner and middle estuary, respectively, whereas an entirely reverse situation was observed in the outer fringes. The fugacity of CO2 in water ranged from 152 to 657 μatm during the study period. The percentage of over-saturation in inner and middle estuary varied from 103 to 168 and 103 to 176 %, respectively, whereas the degree of under-saturation in the outer estuary lied between 40 and 99 %. Chlorophyll a concentrations were found higher in the outer estuary (12.3 ± 2.2 mg m(-3)) compared to the middle (6.4 ± 0.6 mg m(-3)) and inner parts (1.6 ± 0.2 mg m(-3)), followed by a similar decreasing pattern in nutrient availability from the outer to inner estuary. The sampling stations situated at the inner and middle estuary acted as a net source of 29.69 and 23.62 mg CO2 m(-2) day(-1), respectively, whereas the outer station behaved as a net sink of -33.37 mg CO2 m(-2) day(-1). The study of primary production and community respiration further supports the heterotrophic nature of the estuary in the inner region while the outer periphery was marked by dominant autotrophic character. These contrasting results are in parity with the source characters of many inner estuaries and sinking characters of the outer estuaries situated at the distal continental shelf areas.

  3. Aragonite saturation state in a tropical coastal embayment dominated by phytoplankton blooms (Guanabara Bay - Brazil).

    Science.gov (United States)

    Cotovicz, Luiz C; Knoppers, Bastiaan A; Brandini, Nilva; Poirier, Dominique; Costa Santos, Suzan J; Abril, Gwenaël

    2018-04-01

    The dynamics of the aragonite saturation state (Ω arag ) were investigated in the eutrophic coastal waters of Guanabara Bay (RJ-Brazil). Large phytoplankton blooms stimulated by a high nutrient enrichment promoted the production of organic matter with strong uptake of dissolved inorganic carbon (DIC) in surface waters, lowering the concentrations of dissolved carbon dioxide (CO 2aq ), and increasing the pH, Ω arag and carbonate ion (CO 3 2- ), especially during summer. The increase of Ω arag related to biological activity was also evident comparing the negative relationship between the Ω arag and the apparent utilization of oxygen (AOU), with a very close behavior between the slopes of the linear regression and the Redfield ratio. The lowest values of Ω arag were found at low-buffered waters in regions that receive direct discharges from domestic effluents and polluted rivers, with episodic evidences of corrosive waters (Ω arag <1). This study showed that the eutrophication controlled the variations of Ω arag in Guanabara Bay. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Production dynamics and life cycle of dominant chironomids (diptera, chironomidae) in a subtropical stream in China: adaptation to variable flow conditions in summer and autumn

    Science.gov (United States)

    Yan, Yunjun; Li, Xiaoyu

    2007-07-01

    The production dynamics and trophic basis of 7 dominant species of chironomids were investigated in the area of a second-order river of the Hanjiang River basin, in central China from June 2003 to June 2004. The results showed that Tvetenia discoloripes was by far the most abundant chironomid, dominating the overall standing stock of the taxa. In terms of lif ecycle, Chaetocladius sp., Eukiefferiella potthasti and T. discoloripes developed 1 generation a year, whereas Microtendipes sp. and Pagastia sp. developed two, while Pentaneura sp. and Polypedilum sp. developed three. T. discoloripes was the most productive chironomid with 120.305 8 g/m2. a, Pentaneura sp. and E. potthasti had relatively high production values of >17 g/m2.a, and the rest were 0.5), especially for filter-collectors Microtendipes sp., Chaetocladius sp., Chaetocladius sp., T. discoloripes and Pagastia sp. All species except Pentaneura sp. consumed a large portion of amorphous detritus, constituting more than 90% of their diets, and contributing nearly 90% to their secondary production. All the 7 chironomids represent obvious adaptation to local highly variable climate in summer and autumn in life cycle pattern, production dynamics, and food type.

  5. Occurrence and biosynthesis of carotenoids in phytoplankton.

    Science.gov (United States)

    Huang, Jim Junhui; Lin, Shaoling; Xu, Wenwen; Cheung, Peter Chi Keung

    2017-09-01

    Naturally occurring carotenoids are important sources of antioxidants, anti-cancer compounds and anti-inflammatory agents and there is thus considerable market demand for their pharmaceutical applications. Carotenoids are widely distributed in marine and freshwater organisms including microalgae, phytoplankton, crustaceans and fish, as well as in terrestrial plants and birds. Recently, phytoplankton-derived carotenoids have received much attention due to their abundance, rapid rate of biosynthesis and unique composition. The carotenoids that accumulate in particular phytoplankton phyla are synthesized by specific enzymes and play unique physiological roles. This review focuses on studies related to the occurrence of carotenoids in different phytoplankton phyla and the molecular aspects of their biosynthesis. Recent biotechnological advances in the isolation and characterization of some representative carotenoid synthases in phytoplankton are also discussed. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. The role of phytoplankton in the modulation of dissolved and oyster cadmium concentrations in Deep Bay, British Columbia, Canada

    International Nuclear Information System (INIS)

    Cassis, David; Lekhi, Priyanka; Pearce, Christopher M.; Ebell, Nadene; Orians, Kristin; Maldonado, Maria T.

    2011-01-01

    We previously identified dissolved cadmium (Cd diss ) as the main source of this metal in cultured Pacific oysters, Crassostrea gigas, in Deep Bay, British Columbia, Canada (Lekhi et al., 2008). Total suspended particulate Cd (Cd part ) was not found to be a significant source of oyster Cd (Cd oys ), with Cd part > 20 μm negatively correlated with Cd oys concentration. High phytoplankton abundance in spring and summer was hypothesized to reduce Cd oys indirectly by drawing down Cd diss and increasing oyster growth. In the present study we expanded on these results by examining specifically how the phytoplankton community composition modulates both Cd diss and Cd oys concentrations in Deep Bay. Based on calculations of nutrients and Cd diss drawdown, phytoplankton accounted for approximately 90% of the overall summer reduction in Cd diss in the bay. Diatoms were the dominant phytoplankton group, being correlated negatively with Cd oys and positively with Cd part . This suggests that diatom growth mediates the transfer of Cd from the dissolved to the particulate phase, resulting in lower Cd oys . Spring blooms and sporadic harmful algal blooms may mediate a large flux of Cd part to the sediments. Thus, phytoplankton act as a sink, rather than a source, of Cd to oysters in Deep Bay and have a crucial role in the seasonality of Cd oys by reducing the concentration of Cd diss during the summer. Based on environmental variables, two descriptive models for annual Cd oys concentrations were developed using multiple linear regression. The first model (R 2 = 0.870) was created to explain the maximum variability in Cd oys concentrations throughout the year, while the second (R 2 = 0.806) was based on parameters that could be measured easily under farm conditions. Oyster age heavily affected both models, with the first model being secondarily affected by temperature and the second one being more sensitive to changes in salinity. - Highlights: → Phytoplankton and

  7. The role of phytoplankton in the modulation of dissolved and oyster cadmium concentrations in Deep Bay, British Columbia, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Cassis, David, E-mail: dcassis@telus.net [Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 (Canada); Lekhi, Priyanka [Department of Chemistry, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 (Canada); Pearce, Christopher M. [Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, BC, Canada V9T 6N7 (Canada); Ebell, Nadene [Ministry of Agriculture, Nanaimo, BC, Canada V9T 6J9 (Canada); Orians, Kristin [Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 (Canada); Department of Chemistry, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 (Canada); Maldonado, Maria T. [Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 (Canada)

    2011-09-15

    We previously identified dissolved cadmium (Cd{sub diss}) as the main source of this metal in cultured Pacific oysters, Crassostrea gigas, in Deep Bay, British Columbia, Canada (Lekhi et al., 2008). Total suspended particulate Cd (Cd{sub part}) was not found to be a significant source of oyster Cd (Cd{sub oys}), with Cd{sub part} > 20 {mu}m negatively correlated with Cd{sub oys} concentration. High phytoplankton abundance in spring and summer was hypothesized to reduce Cd{sub oys} indirectly by drawing down Cd{sub diss} and increasing oyster growth. In the present study we expanded on these results by examining specifically how the phytoplankton community composition modulates both Cd{sub diss} and Cd{sub oys} concentrations in Deep Bay. Based on calculations of nutrients and Cd{sub diss} drawdown, phytoplankton accounted for approximately 90% of the overall summer reduction in Cd{sub diss} in the bay. Diatoms were the dominant phytoplankton group, being correlated negatively with Cd{sub oys} and positively with Cd{sub part}. This suggests that diatom growth mediates the transfer of Cd from the dissolved to the particulate phase, resulting in lower Cd{sub oys}. Spring blooms and sporadic harmful algal blooms may mediate a large flux of Cd{sub part} to the sediments. Thus, phytoplankton act as a sink, rather than a source, of Cd to oysters in Deep Bay and have a crucial role in the seasonality of Cd{sub oys} by reducing the concentration of Cd{sub diss} during the summer. Based on environmental variables, two descriptive models for annual Cd{sub oys} concentrations were developed using multiple linear regression. The first model (R{sup 2} = 0.870) was created to explain the maximum variability in Cd{sub oys} concentrations throughout the year, while the second (R{sup 2} = 0.806) was based on parameters that could be measured easily under farm conditions. Oyster age heavily affected both models, with the first model being secondarily affected by temperature and the

  8. Five Years of Experimental Warming Increases the Biodiversity and Productivity of Phytoplankton

    Science.gov (United States)

    Yvon-Durocher, Gabriel; Allen, Andrew P.; Cellamare, Maria; Dossena, Matteo; Gaston, Kevin J.; Leitao, Maria; Montoya, José M.; Reuman, Daniel C.; Woodward, Guy; Trimmer, Mark

    2015-01-01

    Phytoplankton are key components of aquatic ecosystems, fixing CO2 from the atmosphere through photosynthesis and supporting secondary production, yet relatively little is known about how future global warming might alter their biodiversity and associated ecosystem functioning. Here, we explore how the structure, function, and biodiversity of a planktonic metacommunity was altered after five years of experimental warming. Our outdoor mesocosm experiment was open to natural dispersal from the regional species pool, allowing us to explore the effects of experimental warming in the context of metacommunity dynamics. Warming of 4°C led to a 67% increase in the species richness of the phytoplankton, more evenly-distributed abundance, and higher rates of gross primary productivity. Warming elevated productivity indirectly, by increasing the biodiversity and biomass of the local phytoplankton communities. Warming also systematically shifted the taxonomic and functional trait composition of the phytoplankton, favoring large, colonial, inedible phytoplankton taxa, suggesting stronger top-down control, mediated by zooplankton grazing played an important role. Overall, our findings suggest that temperature can modulate species coexistence, and through such mechanisms, global warming could, in some cases, increase the species richness and productivity of phytoplankton communities. PMID:26680314

  9. Rising CO2 levels will intensify phytoplankton blooms in eutrophic and hypertrophic lakes.

    Directory of Open Access Journals (Sweden)

    Jolanda M H Verspagen

    Full Text Available Harmful algal blooms threaten the water quality of many eutrophic and hypertrophic lakes and cause severe ecological and economic damage worldwide. Dense blooms often deplete the dissolved CO2 concentration and raise pH. Yet, quantitative prediction of the feedbacks between phytoplankton growth, CO2 drawdown and the inorganic carbon chemistry of aquatic ecosystems has received surprisingly little attention. Here, we develop a mathematical model to predict dynamic changes in dissolved inorganic carbon (DIC, pH and alkalinity during phytoplankton bloom development. We tested the model in chemostat experiments with the freshwater cyanobacterium Microcystis aeruginosa at different CO2 levels. The experiments showed that dense blooms sequestered large amounts of atmospheric CO2, not only by their own biomass production but also by inducing a high pH and alkalinity that enhanced the capacity for DIC storage in the system. We used the model to explore how phytoplankton blooms of eutrophic waters will respond to rising CO2 levels. The model predicts that (1 dense phytoplankton blooms in low- and moderately alkaline waters can deplete the dissolved CO2 concentration to limiting levels and raise the pH over a relatively wide range of atmospheric CO2 conditions, (2 rising atmospheric CO2 levels will enhance phytoplankton blooms in low- and moderately alkaline waters with high nutrient loads, and (3 above some threshold, rising atmospheric CO2 will alleviate phytoplankton blooms from carbon limitation, resulting in less intense CO2 depletion and a lesser increase in pH. Sensitivity analysis indicated that the model predictions were qualitatively robust. Quantitatively, the predictions were sensitive to variation in lake depth, DIC input and CO2 gas transfer across the air-water interface, but relatively robust to variation in the carbon uptake mechanisms of phytoplankton. In total, these findings warn that rising CO2 levels may result in a marked

  10. Winter severity determines functional trait composition of phytoplankton in seasonally ice-covered lakes.

    Science.gov (United States)

    Özkundakci, Deniz; Gsell, Alena S; Hintze, Thomas; Täuscher, Helgard; Adrian, Rita

    2016-01-01

    How climate change will affect the community dynamics and functionality of lake ecosystems during winter is still little understood. This is also true for phytoplankton in seasonally ice-covered temperate lakes which are particularly vulnerable to the presence or absence of ice. We examined changes in pelagic phytoplankton winter community structure in a north temperate lake (Müggelsee, Germany), covering 18 winters between 1995 and 2013. We tested how phytoplankton taxa composition varied along a winter-severity gradient and to what extent winter severity shaped the functional trait composition of overwintering phytoplankton communities using multivariate statistical analyses and a functional trait-based approach. We hypothesized that overwintering phytoplankton communities are dominated by taxa with trait combinations corresponding to the prevailing winter water column conditions, using ice thickness measurements as a winter-severity indicator. Winter severity had little effect on univariate diversity indicators (taxon richness and evenness), but a strong relationship was found between the phytoplankton community structure and winter severity when taxon trait identity was taken into account. Species responses to winter severity were mediated by the key functional traits: motility, nutritional mode, and the ability to form resting stages. Accordingly, one or the other of two functional groups dominated the phytoplankton biomass during mild winters (i.e., thin or no ice cover; phototrophic taxa) or severe winters (i.e., thick ice cover; exclusively motile taxa). Based on predicted milder winters for temperate regions and a reduction in ice-cover durations, phytoplankton communities during winter can be expected to comprise taxa that have a relative advantage when the water column is well mixed (i.e., need not be motile) and light is less limiting (i.e., need not be mixotrophic). A potential implication of this result is that winter severity promotes different

  11. Rising CO2 Levels Will Intensify Phytoplankton Blooms in Eutrophic and Hypertrophic Lakes

    Science.gov (United States)

    Verspagen, Jolanda M. H.; Van de Waal, Dedmer B.; Finke, Jan F.; Visser, Petra M.; Van Donk, Ellen; Huisman, Jef

    2014-01-01

    Harmful algal blooms threaten the water quality of many eutrophic and hypertrophic lakes and cause severe ecological and economic damage worldwide. Dense blooms often deplete the dissolved CO2 concentration and raise pH. Yet, quantitative prediction of the feedbacks between phytoplankton growth, CO2 drawdown and the inorganic carbon chemistry of aquatic ecosystems has received surprisingly little attention. Here, we develop a mathematical model to predict dynamic changes in dissolved inorganic carbon (DIC), pH and alkalinity during phytoplankton bloom development. We tested the model in chemostat experiments with the freshwater cyanobacterium Microcystis aeruginosa at different CO2 levels. The experiments showed that dense blooms sequestered large amounts of atmospheric CO2, not only by their own biomass production but also by inducing a high pH and alkalinity that enhanced the capacity for DIC storage in the system. We used the model to explore how phytoplankton blooms of eutrophic waters will respond to rising CO2 levels. The model predicts that (1) dense phytoplankton blooms in low- and moderately alkaline waters can deplete the dissolved CO2 concentration to limiting levels and raise the pH over a relatively wide range of atmospheric CO2 conditions, (2) rising atmospheric CO2 levels will enhance phytoplankton blooms in low- and moderately alkaline waters with high nutrient loads, and (3) above some threshold, rising atmospheric CO2 will alleviate phytoplankton blooms from carbon limitation, resulting in less intense CO2 depletion and a lesser increase in pH. Sensitivity analysis indicated that the model predictions were qualitatively robust. Quantitatively, the predictions were sensitive to variation in lake depth, DIC input and CO2 gas transfer across the air-water interface, but relatively robust to variation in the carbon uptake mechanisms of phytoplankton. In total, these findings warn that rising CO2 levels may result in a marked intensification of

  12. Indian Summer

    Energy Technology Data Exchange (ETDEWEB)

    Galindo, E. [Sho-Ban High School, Fort Hall, ID (United States)

    1997-08-01

    This paper focuses on preserving and strengthening two resources culturally and socially important to the Shoshone-Bannock Indian Tribe on the Fort Hall Reservation in Idaho; their young people and the Pacific-Northwest Salmon. After learning that salmon were not returning in significant numbers to ancestral fishing waters at headwater spawning sites, tribal youth wanted to know why. As a result, the Indian Summer project was conceived to give Shoshone-Bannock High School students the opportunity to develop hands-on, workable solutions to improve future Indian fishing and help make the river healthy again. The project goals were to increase the number of fry introduced into the streams, teach the Shoshone-Bannock students how to use scientific methodologies, and get students, parents, community members, and Indian and non-Indian mentors excited about learning. The students chose an egg incubation experiment to help increase self-sustaining, natural production of steelhead trout, and formulated and carried out a three step plan to increase the hatch-rate of steelhead trout in Idaho waters. With the help of local companies, governmental agencies, scientists, and mentors students have been able to meet their project goals, and at the same time, have learned how to use scientific methods to solve real life problems, how to return what they have used to the water and land, and how to have fun and enjoy life while learning.

  13. Summer Students

    CERN Multimedia

    2005-01-01

    SUMMER STUDENT LECTURE PROGRAMME Main Auditorium, bldg. 500 Monday 8 August 09:15 - 10:00 A. Höcker CP Violation (3/4) 10:15 - 12:00 J-J. GOMEZ-CADENAS Neutrino Physics (1-2/4) 12:00 Discussion Session Tuesday 9 August 09:15 - 10:00 A. Höcker CP Violation (4/4) 10:15 - 11:00 J-J. GOMEZ-CADENAS Neutrino Physics (3/4) 11:15 - 12:00 F. GREY The GRID 12:00 Discussion Session 14:15 - 17:00 Student Sessions Wednesday 10 August 09:15 - 10:00 J-J. GOMEZ-CADENAS Neutrino Physics (4/4) 10:15 - 12:00 J. LESGOURGUES Introduction to Cosmology (1-2/5) 12:00 Discussion Session 14:15 - 17:00 Student Sessions Thursday 11 August 09:15 - 11:00 J. LESGOURGUES Introduction to Cosmology (3-4/5) 11:15 - 12:00 G. KALMUS The ILC Story 12:00 Discussion Session Friday 12 August 09:15 - 10:00 J. LESGOURGUES Introduction to Cosmology (5/5) 10:15 - 11:00 G. VENEZIANO String theory: has Einstein's dream come true? 11:00  Discussion...

  14. Summer Students

    CERN Multimedia

    2005-01-01

    SUMMER STUDENT LECTURE PROGRAMME Main Auditorium, bldg. 500 DATE TIME LECTURER TITLE Monday 1 August 09:15 - 10:00 P. WELLS The Higgs Saga at LEP 10:15 - 11:00 E. KIRITSIS Beyond the Standard Model (1/4) 11:15 - 12:00 G. COWAN Introduction to Statistics (1/3) 12:00 Discussion Session Tuesday 2 August 09:15 - 11:00 E. KIRITSIS Beyond the Standard Model (2-3/4) 11:15 - 12:00 G. COWAN Introduction to Statistics (2/3) 12:00 Discussion Session Wednesday 3 August 09:15 - 10:00 G. COWAN Introduction to Statistics (3/3) 10:15 - 11:00 E. KIRITSIS Beyond the Standard Model (4/4) 11:15 - 12:00 K. JAKOBS Physics at Hadronic Colliders (1/4) 12:00 Discussion Session Thursday 4 August 09:15 - 11:00 K. JAKOBS Physics at Hadronic Colliders (2-3/4) 11:15 - 12:00 A. WEINSTEIN Gravitation Waves 12:00 Discussion Session 16:30 - 18:00 Poster Session Friday 5 August 09:15 - 11:00 A. Höcker CP Violation (1-2/4) 11:15 - 12:00 K. JA...

  15. Summer Students

    CERN Multimedia

    2005-01-01

    SUMMER STUDENT LECTURE PROGRAMME Main Auditorium, bldg. 500 DATE TIME LECTURER TITLE Monday 18 July 09:15 - 11:00 G. ROSS Fundamental concepts in Particle Physics (1-2/6) 11:15 - 12:00 N. PALANQUE-DELABROUILLE Astroparticle Physics (1/3) 12:00 Discussion Session Tuesday 19 July 09:15 - 10:00 G. ROSS Fundamental concepts in Particle Physics (3/6) 10:15 - 12:00 N. PALANQUE-DELABROUILLE Astroparticle Physics (2-3/3) 12:00 Discussion Session Wednesday 20 July 09:15 - 10:00 G. ROSS Fundamental concepts in Particle Physics (4/6) 10:15 - 11:00 F. RADEMAKERS ROOT 11:15 - 12:00 L. ROSSI Super-conducting magnet technology for particle accelerators and detectors 12:00 Discussion Session Thursday 21 July 09:15 - 10:00 G. ROSS Fundamental concepts in Particle Physics (5/6) 10:15 - 12:00 C. DE LA TAILLE Introduction to Electronics (1-2/3) 12:00 Discussion Session Friday 22 July 09:15 - 10:00 C. DE LA TAILLE Introduction to Electronics (3/3) 10:15 -...

  16. Summer Students

    CERN Multimedia

    2005-01-01

    SUMMER STUDENT LECTURE PROGRAMME Main Auditorium, bldg. 500 DATE TIME LECTURER TITLE Monday 25 July 09:15 - 11:00 A. PICH The Standard Model (2-3/8) 11:15 - 12:00 J. STACHEL Quark Gluon Plasma Physics (1/3) 12:00 Discussion Session Tuesday 26 July 09:15 - 10:00 A. PICH The Standard Model (4/8) 10:15 - 12:00 J. STACHEL Quark Gluon Plasma Physics (2-3/3) 12:00 Discussion Session Wednesday 27 July 09:15 - 11:00 A. PICH The Standard Model (5-6/8) 11:15 - 12:00 J-P. DELAHAYE The CLIC Concept and Technology for an e+e-Collider at the Energy Frontier 11:15 - 12:00 Discussion Session Thursday 28 July 09:15 - 10:00 A. PICH The Standard Model (7/8) 10:15 - 11:00 P. SPHICAS Data Acquisition Systems (1/2) 11:15 - 12:00 R. JACOBSEN From Raw data to Physics Results (1/2) 12:00 Discussion Session Friday 29 July 09:15 - 10:00 A. PICH The Standard Model (8/8) 10:15 - 11:00 P. SPHICAS Data Acquisition Systems (2/2) 11:15 - 12:00 R. JACOBSEN Fr...

  17. Summer Students

    CERN Multimedia

    2005-01-01

    SUMMER STUDENT LECTURE PROGRAMME Main Auditorium, bldg. 500 DATE TIME LECTURER TITLE Monday 11 July 09:15 - 10:00 L. Di Lella (CERN) Introduction to Particle Physics (4/4) 10:15 - 11:00 P. Chomaz (GANIL / CERN) Introduction to Nuclear Physics (3/3) 11:15 - 12:00 G. ROLANDI (CERN) How an experiment is designed (2/2) 12:00 Discussion Session Tuesday 12 July  09:15 - 11:00 O. BrÜning (CERN) Accelerators (1-2/5) 11:15 - 12:00 O. ULLALAND (CERN) Detectors (1/5) 12:00 Discussion Session Wednesday 13 July 09:15 - 10:00 O. BrÜning (CERN) Accelerators (3/5) 10:15 - 11:00 R. LANDUA (CERN) Antimatter in the Lab (1/2) 11:15 - 12:00 O. ULLALAND (CERN) Detectors (2/5) 12:00 Discussion Session Thursday 14 July 09:15 - 10:00 O. ULLALAND (CERN) Detectors (3/5) 10:15 - 11:00 G. ROLANDI (CERN) Antimatter in the Lab (2/2) 11:15 - 12:00 O. BrÜning (CERN) Accelerators (4/5) 12:00 Discussion Session Friday 1...

  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. Dinâmica de crescimento da abobrinha italiana em duas estações de cultivo = Growth dynamic of summer squash in two crop seasons.

    Directory of Open Access Journals (Sweden)

    André Samuel Strassburger

    2011-04-01

    Full Text Available O objetivo deste trabalho foi quantificar os índices de crescimento, a produção e a distribuição de matéria seca da cultura da abobrinha italiana cultivada em substrato de casca de arroz in natura com solução nutritiva recirculante, em duas épocas de cultivo: primavera-verão de 2005 e verão-outono de 2006, caracterizadas, respectivamente, como períodos de alta e baixa disponibilidades de radiação solar. Cada tratamento correspondeu a uma época de amostragem, sendo a produção de matéria seca quantificada aos 0, 18, 32, 46 e 68 dias após o transplante (DAT no cultivo de primavera-verão, e aos 0, 15, 29, 43 e 55 DAT no cultivo de verão-outono.A produção de matéria seca foi maior quando a disponibilidade de radiação solar foi mais elevada. Nessa situação (alta disponibilidade de radiação solar, os frutos caracterizaram-se como os maiores drenos da cultura, não ocorrendo o mesmo em condições de baixa disponibilidade de radiação solar. As taxas de crescimento (da cultura, dos frutos, dos órgãos vegetativos aéreos e relativa também foram mais elevadas quando a radiação solar disponível foi mais elevada. A razão de área foliar e a área foliar específica apresentaram dinâmicas semelhantes à taxa de crescimento relativo, decrescendo com o decorrer do período de cultivo.The objective of this work was to quantify the growth rates, dry matter production and distribution of summer squash grown in raw rice husk medium with recirculating nutrient solution, in two crop seasons:spring-summer 2005 and summer-autumn 2006, which are periods characterized by high and low solar radiation availability, respectively. Each treatment corresponded to a sampling date and dry matter production was evaluated at 18, 32, 46 and 68 days after setting (DAS in springsummer, and 15, 29, 43 and 55 DAS in the summer-autumn crop season. Dry matter production was highest in high solar radiation availability conditions. In those

  20. Tolerance of polar phytoplankton communities to metals

    International Nuclear Information System (INIS)

    Echeveste, P.; Tovar-Sánchez, A.; Agustí, S.

    2014-01-01

    Large amounts of pollutants reach polar regions, particularly the Arctic, impacting their communities. In this study we analyzed the toxic levels of Hg, Cd and Pb to natural phytoplankton communities of the Arctic and Southern Oceans, and compared their sensitivities with those observed on phytoplankton natural communities from temperate areas. Mercury was the most toxic metal for both Arctic and Antarctic communities, while both Cd and Pb were toxic only for the Antarctic phytoplankton. Total cell abundance of the populations forming the Arctic community increased under high Cd and Pb concentrations, probably due to a decrease of the grazing pressure or the increase of the most resistant species, although analysis of individual cells indicated that cell death was already induced at the highest levels. These results suggest that phytoplankton may have acquired adapting mechanisms to face high levels of Pb and Cd in the Arctic Ocean. Highlights: • First study analyzing the toxicity of Hg, Cd or Pb to natural polar phytoplankton. • Arctic Ocean communities highly resistant to Cd and Pb, but not to Hg. • Southern Ocean communities sensitive to Cd, Pb and Hg. • Both communities incorporated Pb at a similar level. • Arctic phytoplankton may have acquired adapting mechanisms against Cd and Pb. -- Polar phytoplankton communities are tolerant to Cd and Pb, specially the Arctic ones, suggesting the acquisition of adapting mechanisms to face metals' toxicity

  1. Phytoplankton can actively diversify their migration strategy in response to turbulent cues.

    Science.gov (United States)

    Sengupta, Anupam; Carrara, Francesco; Stocker, Roman

    2017-03-23

    Marine phytoplankton inhabit a dynamic environment where turbulence, together with nutrient and light availability, shapes species fitness, succession and selection. Many species of phytoplankton are motile and undertake diel vertical migrations to gain access to nutrient-rich deeper layers at night and well-lit surface waters during the day. Disruption of this migratory strategy by turbulence is considered to be an important cause of the succession between motile and non-motile species when conditions turn turbulent. However, this classical view neglects the possibility that motile species may actively respond to turbulent cues to avoid layers of strong turbulence. Here we report that phytoplankton, including raphidophytes and dinoflagellates, can actively diversify their migratory strategy in response to hydrodynamic cues characteristic of overturning by Kolmogorov-scale eddies. Upon experiencing repeated overturning with timescales and statistics representative of ocean turbulence, an upward-swimming population rapidly (5-60 min) splits into two subpopulations, one swimming upward and one swimming downward. Quantitative morphological analysis of the harmful-algal-bloom-forming raphidophyte Heterosigma akashiwo together with a model of cell mechanics revealed that this behaviour was accompanied by a modulation of the cells' fore-aft asymmetry. The minute magnitude of the required modulation, sufficient to invert the preferential swimming direction of the cells, highlights the advanced level of control that phytoplankton can exert on their migratory behaviour. Together with observations of enhanced cellular stress after overturning and the typically deleterious effects of strong turbulence on motile phytoplankton, these results point to an active adaptation of H. akashiwo to increase the chance of evading turbulent layers by diversifying the direction of migration within the population, in a manner suggestive of evolutionary bet-hedging. This migratory behaviour

  2. Spatial-temporal distribution of phytoplankton pigments in relation to nutrient status in Jiaozhou Bay, China

    Science.gov (United States)

    Yao, Peng; Yu, Zhigang; Deng, Chunmei; Liu, Shuxia; Zhen, Yu

    2010-10-01

    We conducted studies of phytoplankton and hydrological variables in a semi-enclosed bay in northern China to understand the spatial-temporal variability and relationship between these variables. Samples were collected during seven cruises in Jiaozhou Bay from November 2003 to October 2004, and were analyzed for temperature, nutrients and phytoplankton pigments. Pigments from eight possible phytoplankton classes (Diatoms, Dinoflagellates, Chlorophyceae, Prasinophyceae, Chrysophyceae, Haptophyceae, Cryptophyceae and Caynophyceae) were detected in surface water by high performance liquid chromatography (HPLC). Phytoplankton pigment and nutrient concentrations in Jiaozhou Bay were spatially and temporally variable, and most of them were highest in the northern and eastern parts of the sampling regions in spring (May) and summer (August), close to areas of shellfish culturing, river estuaries, dense population and high industrialization, reflecting human activities. Chlorophyll a was recorded in all samples, with an annual mean concentration of 1.892 μg L -1, and fucoxanthin was the most abundant accessory pigment, with a mean concentration of 0.791 μg L -1. The highest concentrations of chlorophyll a (15.299 μg L -1) and fucoxanthin (9.417 μg L -1) were observed in May 2004 at the station close to the Qingdao Xiaogang Ferry, indicating a spring bloom of Diatoms in this area. Although chlorophyll a and other biomarker pigments showed significant correlations, none of them showed strong correlations with temperature and nutrients, suggesting an apparent de-coupling between the pigments and these hydrological variables. The nutrient composition and phytoplankton community composition of Jiaozhou Bay have changed significantly in the past several decades, reflecting the increasing nutrient concentrations and decline of phytoplankton cell abundance. The unchanged total chlorophyll a levels indicated that smaller species have filled the niche vacated by the larger

  3. Phytoplankton Regulation in a Eutrophic Tidal River (San Joaquin River, California

    Directory of Open Access Journals (Sweden)

    Alan D. Jassby

    2005-03-01

    Full Text Available As in many U.S. estuaries, the tidal San Joaquin River exhibits elevated organic matter production that interferes with beneficial uses of the river, including fish spawning and migration. High phytoplankton biomass in the tidal river is consequently a focus of management strategies. An unusually long and comprehensive monitoring dataset enabled identification of the determinants of phytoplankton biomass. Phytoplankton carrying capacity may be set by nitrogen or phosphorus during extreme drought years but, in most years, growth rate is light-limited. The size of the annual phytoplankton bloom depends primarily on river discharge during late spring and early summer, which determines the cumulative light exposure in transit downstream. The biomass-discharge relationship has shifted over the years, for reasons as yet unknown. Water diversions from the tidal San Joaquin River also affect residence time during passage downstream and may have resulted in more than a doubling of peak concentration in some years. Dam construction and accompanying changes in storage-and-release patterns from upstream reservoirs have caused a long-term decrease in the frequency of large blooms since the early 1980s, but projected climate change favors a future increase. Only large decreases in nonpoint nutrient sources will limit phytoplankton biomass reliably. Growth rate and concentration could increase if nonpoint source management decreases mineral suspensoid load but does not decrease nutrient load sufficiently. Small changes in water storage and release patterns due to dam operation have a major influence on peak phytoplankton biomass, and offer a near-term approach for management of nuisance algal blooms.

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

    Science.gov (United States)

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

    2015-08-11

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

  5. Phytoplankton response to fish-induced environmental changes in a temperate shallow pond-type lake

    Directory of Open Access Journals (Sweden)

    Napiórkowska-Krzebietke Agnieszka

    2017-12-01

    Full Text Available Since 1967, the temperate, shallow, pond-type Lake Warniak has been subjected to different biomanipulation methods including the introduction of common carp, Cyprinus carpio L., grass carp, Ctenopharyngodon idella (Val., silver carp, Hypophthalmichthys molitrix (Val., and bighead carp, Hypophthalmichthys nobilis (Richardson and then their removal in an effort to control macrophytes and phytoplankton. Recently, pilot stocking with predatory fish, particularly pike, Esox lucius L., has also been conducted. Hence, an examination of the long-term response patterns of phytoplankton to multiple fish-induced stressors was undertaken. In recent years, Chara domination (2000-2004 has helped to stabilize a clear-water state, high/good ecological status, and meso-eutrophic conditions. After the disappearance of Charales in 2004, the rapid, unstable changes in phytoplankton biomass, structure, and biodiversity suggested a shift toward a turbid-water state. As a result, the phytoplankton assemblages changed from those dominated by cryptophytes Y+X2+X1+LO (2000-2004 through those dominated by cyanobacteria K (2005-2008, dinoflagellates LO+Y (2009-2011, and cryptophytes Y+LO+F+X2 (2012, to those dominated by diatoms D+K+P+A (2013-2014 with representative taxa that occur in nutrient-rich and/or nutrient-poor water bodies. The 1967-2014 changes indicated that four periods, two with clear-water state and two with turbid-water state, alternately, one after the other, resulted from different fish pressure. Higher autochthonous fish biomass was usually accompanied by lower phytoplankton biomass. In contrast, the introduction of Cyprinidae fish had a stimulating effect on summer phytoplankton dominated by cyanobateria. Among the nutrients, only phosphorus played an important role.

  6. Seasonal changes in nutrients, chlorophyll a and the phytoplankton assemblage of the western subarctic gyre in the Pacific Ocean

    Science.gov (United States)

    Mochizuki, Mamiko; Shiga, Naonobu; Saito, Masaru; Imai, Keiri; Nojiri, Yukihiro

    The standing stock and species composition of phytoplankton (>10 μm) were studied using monthly water samples collected at Stn KNOT (Kyodo North Pacific Ocean Time Series; 44°N, 155°E) in the western subarctic gyre in the Pacific Ocean through June 1998 to June 1999 (except for January-April 1999) and January-February 2000. One-liter water samples were preserved in 1% neutrally buffered formalin. Identification and enumeration of phytoplankton were made with an inverted microscope. Nutrients did not appear to be depleted for phytoplakton growth during any season. The vertical distribution of phytoplankton was primarily restricted by the pycnocline, and the bulk of phytoplankton assemblage existed within the surface mixed layer. In July, however, some senescent cells were observed at 200 m. Phytoplankton abundance clearly showed a spring maximum (i.e. spring bloom) in May. The seasonal change in cell numbers, however, did not coincide closely with the change in chlorophyll a concentration. Centric diatoms, which were composed of Thalassiosira, Chaetoceros, and Coscinodiscus, dominated all year round, and showed temporal succession. Pennate diatoms (mostly Neodenticula seminae and Fragilariopsis) increased only during the spring bloom. Dinoflagellates (mostly Gymnodinium and Prorocentrum) were low in abundance, although they increased in summer when the phytoplankton standing stock was low. Silicoflagellate abundance was extremely low. Comparing the annual species composition of phytoplankton between Stn KNOT and Stn P (50°N, 145°W) in the Alaskan Gyre, there was a remarkable difference between the two sites. The phytoplankton assemblage at Stn P is characterized by a high abundance of Rhizosolenia alata and low abundance of Thalassiosira. In contrast, Thalassiosira dominates at Stn KNOT during most seasons.

  7. A major seasonal phytoplankton bloom in the Madagascar Basin

    Science.gov (United States)

    Longhurst, Alan

    2001-11-01

    A hitherto-unnoticed phytoplankton bloom, of dimension 3000×1500 km, occupies the Madagascar Basin in late austral summer, being a prominent feature in SeaWiFS images. A first-order interpretation of the bloom mechanism invokes the seasonal deepening of the mixed layer within a strong mesoscale eddy-field and the consequent entrainment of nutrients into the photic zone. Features of the bloom correspond closely and appropriately with features of the eddy-field as observed by TOPEX-POSEIDON sea level anomalies. The bloom failed to develop in 1998, the second year of a two-year ENSO episode, when anomalously weak Southeast Trades will have failed to deepen the mixed layer as in other years.

  8. Modeling phytoplankton community in reservoirs. A comparison between taxonomic and functional groups-based models.

    Science.gov (United States)

    Di Maggio, Jimena; Fernández, Carolina; Parodi, Elisa R; Diaz, M Soledad; Estrada, Vanina

    2016-01-01

    In this paper we address the formulation of two mechanistic water quality models that differ in the way the phytoplankton community is described. We carry out parameter estimation subject to differential-algebraic constraints and validation for each model and comparison between models performance. The first approach aggregates phytoplankton species based on their phylogenetic characteristics (Taxonomic group model) and the second one, on their morpho-functional properties following Reynolds' classification (Functional group model). The latter approach takes into account tolerance and sensitivity to environmental conditions. The constrained parameter estimation problems are formulated within an equation oriented framework, with a maximum likelihood objective function. The study site is Paso de las Piedras Reservoir (Argentina), which supplies water for consumption for 450,000 population. Numerical results show that phytoplankton morpho-functional groups more closely represent each species growth requirements within the group. Each model performance is quantitatively assessed by three diagnostic measures. Parameter estimation results for seasonal dynamics of the phytoplankton community and main biogeochemical variables for a one-year time horizon are presented and compared for both models, showing the functional group model enhanced performance. Finally, we explore increasing nutrient loading scenarios and predict their effect on phytoplankton dynamics throughout a one-year time horizon. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Emergent neutrality drives phytoplankton species coexistence

    Science.gov (United States)

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

    2011-01-01

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

  10. Taxonomic composition of phytoplankton in the Vakh River (Western Siberia)

    Science.gov (United States)

    Skorobogatova, O. N.

    2018-03-01

    This paper provides data on the hydrological and hydrochemical parameters of the Vakh River in the Middle Ob region. In 2005-2008 we have identified 404 taxonomic units represented by 463 species, types and forms of algae, belonging to 140 genera, 52 families, 13 classes and 7 divisions. 386 species were identified for the first time, 141 taxa were identified as rare and 22 taxa as new for Western Siberia. Leading divisions, Bacillariophyta and Chlorophyta, make up for 78.9% of total phytoplankton diversity. Cyanobacteria, Chrysophyta and Euglenophyta form a community of 88 taxonomic units having a rank lower than genus level, and represent 19.0% of the total number. The floral role of Xanthophyta and Dinophyta is insignificant (2.1%). The main structure-forming species are 14: vegetating throughout the year (Aulacoseira italica, Asterionella formosa), summer taxa (Microcystis aeruginosa, Melosira varians, Aulacoseira granulata, Pandorina morum, Pediastrum boryanum, P. duplex, Lacunastrum gracillimum, Scenedesmus quadricauda) and summer-autumn (Microcystis pulverea, Tabellaria fenestrata, T. flocculosa, Mucidosphaerium pulchellum). The Vakh River demonstrates specific characteristics of boreal flowing waterways. The northern composition is represented in a big rate of families (44.2%) and genera (109 77.9) with one to three species. The richest genera Closterium (31 taxa), Eunotia (27 taxa), Pinnularia (22 taxa), Desmidium (11 taxa) and the family Desmidiaceae (45 taxa) ensure diversity of phytoplankton. Ecological and geographical analysis demonstrates predominance of cosmopolitan algae (56.6%). Plankton represents 44.7% of all algae, oligogalobs - 78.8% and indifferent algae – 36.7%. Water meets the requirements for β-mezosaprobian pollution zone, class of satisfactory purity (III class).

  11. 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...

  12. Studies on phytoplankton with reference to dinoflagellates

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, R.K.

    Bibliography Publications Appendices Statement As required under the University ordinance 0.19.8 (vi), I state that the present thesis titled ³Studies on phytoplankton with reference to dinoflagellates´ is my original contribution...

  13. Photophysiological and light absorption properties of phytoplankton communities in the river-dominated margin of the northern Gulf of Mexico

    Science.gov (United States)

    Chakraborty, Sumit; Lohrenz, Steven E.; Gundersen, Kjell

    2017-06-01

    optical properties as key factors in explaining the variability of photosynthesis-light relationships in the dynamic and complex continental margin of the northern Gulf of Mexico. Photoacclimation of phytoplankton in different light environments, from the highly turbid Mississippi River delta to relatively oligotrophic offshore waters, was evident and considered to be a factor regulating the efficiency of carbon fixation in photosynthesis. Our findings were unprecedented in revealing significant differences in photosynthetic parameters between the major phytoplankton groups in northern Gulf of Mexico waters. This enabled us to build an empirical model to predict photosynthetic parameters for the major phytoplankton groups across the entire study area. These findings provide a basis for further efforts to apply this approach for wider-scale modeling of primary production in the northern Gulf of Mexico.

  14. Ecotoxicology of bromoacetic acid on estuarine phytoplankton

    International Nuclear Information System (INIS)

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

    2015-01-01

    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 EC 50 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 EC 50 s 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 EC 50 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 EC 50 decrease in mixed natural phytoplankton populations affirms the importance of field confirmation for establishing water quality criteria. - Highlights: • Bromoacetic acid exposure resulted in lethal impacts to estuarine phytoplankton. • Cultured phytoplankton were less sensitive to bromoacetic acid than natural communities. • Lab results should be confirmed with field experiments whenever possible. - The toxicology of haloacetic acids has been studied in freshwater ecosystems, and urbanization of the coastal zone is making effects in marine ecosystems equally relevant.

  15. 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.

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

    Science.gov (United States)

    Rousseaux, Cecile Severine; Gregg, Watson W.

    2013-01-01

    on group-specific primary production in the Southern Ocean. 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.

  17. Warming accelerates termination of a phytoplankton spring bloom by fungal parasites

    NARCIS (Netherlands)

    Frenken, Thijs; Velthuis, Mandy; Senerpont Domis, de L.N.; Stephan, Susanne; Aben, Ralf; Kosten, Sarian; Donk, van Ellen; Waal, Van de D.B.

    2016-01-01

    Climate change is expected to favour infectious diseases across ecosystems worldwide. In freshwater and marine environments, parasites play a crucial role in controlling plankton population dynamics. Infection of phytoplankton populations will cause a transfer of carbon and nutrients into

  18. Phospholipid-derived fatty acids as chemotaxonomic markers for phytoplankton: application for inferring phytoplankton composition

    NARCIS (Netherlands)

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

    2006-01-01

    Phospholipid-derived fatty acids (PLFA) are widely used as chemotaxonomic markers in microbial ecology. In this paper we explore the use of PLFA as chemotaxonomic markers for phytoplankton species. The PLFA composition was determined for 23 species relevant to estuarine phytoplankton. The taxonomic

  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. Moisture dynamics of the northward and eastward propagating boreal summer intraseasonal oscillations: possible role of tropical Indo-west Pacific SST and circulation

    Science.gov (United States)

    Pillai, Prasanth A.; Sahai, A. K.

    2016-08-01

    Boreal summer intraseasonal oscillation (BSISO) has complex spatial structure due to the co-existence of equatorial eastward and off-equatorial northward propagation in the equatorial Indian Ocean. As a result, equatorial Indian Ocean convection has simultaneous northward and eastward (NE), northward only (N-only) and eastward only (E-only) propagations. It is well established that the convection propagates in the direction of increasing moist static energy (MSE). The moisture and MSE budget analysis reveals that the horizontal advection of anomalous MSE contributes to positive MSE tendency, which is in agreement with the horizontal advection of column integrated moisture anomaly. Northward movement of warm SST and the anomalous moisture advected by zonal wind are the major initiative for the northward propagation of convection from the equatorial Indian Ocean in both NE and N-only category. At the same time warm SST anomaly in the equatorial west Pacific along with moisture advection caused by anomalous meridional wind is important for the equatorial eastward branch of NE propagation. As these anomalies in the west Pacific moves northward, equatorial Indian Ocean convection establishes over the equatorial west Pacific. The absence of these processes confines the BSISO in northward direction for N-only category. In the case of E-only movement, warm SST anomaly and moisture advection by zonal component of wind causes the eastward propagation of convection. Boundary layer moisture convergence always remains east of convection center in E-only propagation, while it coincides with convection centre in other two categories. Thus the present study concludes that the difference in underlying SST and atmospheric circulation in tropical Indo-west Pacific oceanic regions encourage the differential propagation of BSISO convection through moisture dynamics.

  1. Decomposition of lake phytoplankton. 2

    International Nuclear Information System (INIS)

    Hansen, L.; Krog, G.F.; Soendergaard, M.

    1986-01-01

    The lysis process of phytoplankton was followed in 24 h incubations in three Danish lakes. By means of gel-chromatography it was shown that the dissolved carbon leaching from different algal groups differed in molecular weight composition. Three distinct molecular weight classes (>10,000; 700 to 10,000 and < 700 Daltons) leached from blue-green algae in almost equal proportion. The lysis products of spring-bloom diatoms included only the two smaller size classes, and the molecules between 700 and 10,000 Daltons dominated. Measurements of cell content during decomposition of the diatoms revealed polysaccharides and low molecular weight compounds to dominate the lysis products. No proteins were leached during the first 24 h after cell death. By incubating the dead algae in natural lake water, it was possible to detect a high bacterial affinity towards molecules between 700 and 10,000 Daltons, although the other size classes were also utilized. Bacterial transformation of small molecules to larger molecules could be demonstrated. (author)

  2. 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.

  3. Effects of Nutrient Dynamics, Light and Temperature on the Patchiness of Phytoplankton and Primary Production in the Estuarine and Coastal Zones of Liaodong Bay, China: A Typical Case Study

    Science.gov (United States)

    Pei, S.; Laws, E. A.; Ye, S.

    2017-12-01

    Fluvial inputs of nutrients and efficient nutrient recycling mechanisms make estuarine and coastal zones highly productive bodies of water. For the same reasons, they are susceptible to eutrophication problems. In China, eutrophication problems along coasts are becoming serious because of discharges of domestic sewage and industrial wastewater and runoff of agricultural fertilizer. Addressing these problems requires an informed assessment of the factors that controlling algal production. Our study aims at determining the factors that controlling patchiness of phytoplankton and primary production in Liaodong Bay, China that receives large inputs of nutrients from human activities in its watershed, and examining the variation patterns of phytoplankton photosynthesis under both stressors of climate change and human activities. Results of our field study suggest that nutrient concentrations were above growth-rate-saturating concentrations throughout Liaodong bay, with the possible exception of phosphate at some stations. This assessment was consistent with the results of nutrient enrichment experiments and the values of light-saturated photosynthetic rates and areal photosynthetic rates. Two large patches of high biomass and production with dimensions on the order of 10 km reflect the effects of water temperature and variation of light penetration restricted by water turbidity. To examine the effects of irradiance and temperature on light-saturated photosynthetic rates normalized to chlorophyll a concentrations (Popt), light-conditioned Popt values were modeled as a function of the temperature with a satisfactory fit to our field data (R2 = 0.60, p = 0.003). In this model, light-conditioned Popt values increased with temperatures from 22°C to roughly 25°C but declined precipitously at higher temperatures. The relatively high Popt values and low ratios of light absorbed to photosynthesis at coastal stations suggest the highly efficient usage of absorbed light by

  4. A numerical analysis of carbon dynamics of the Southern Ocean phytoplankton community: the roles of light and grazing in effecting both sequestration of atmospheric CO 2 and food availability to larval krill

    Science.gov (United States)

    Walsh, John J.; Dieterle, Dwight A.; Lenes, Jason

    2001-01-01

    Reduced ice extent within coastal regions of the Southern Ocean may lead to deeper surface mixed layers (SML), as prevail in offshore areas. A future decline of ice melt-induced stability of the water column may be associated with a shift in dominant food webs, from larger, sun-adapted diatoms grazed by euphausiids to smaller, shade-adapted flagellates consumed by salps. A basically one-dimensional numerical model of three dominant groups of the Antarctic phytoplankton community (diatoms, cryptophytes, and colonial prymnesiophytes) and four types of herbivore (protozoans, salps, copepods, and euphausiids) is used to explore the seasonal importance of both light limitation and grazing pressure on the amount of annual carbon sequestration and larval krill survival within contrasting oceanic and neritic waters, where respective validation data have been gathered during austral spring by the European JGOFS and RACER programs. With imposition of moderate and large grazing stresses, thought to be typical of offshore waters, we were able to replicate the European JGOFS 1992 observations of light penetration, phytoplankton biomass, primary production, pCO 2, bacterial biomass, labile DOC, ammonium, and total particle effluxes at 100 m within the deep SML of our model. The fidelity of such a large set of simulated state variables suggests that multiple limiting factors are indeed operating on different components of the oceanic phytoplankton community — selective grazing losses on the flagellates, but light limitation of diatoms. Release of protozoan grazing pressure in our model instead leads to unobserved spring blooms of cryptophytes, found only in laboratory enclosures. On an annual basis, weak sequestration of atmospheric CO 2 is simulated in a habitat typical of the Polar Front, while evasion of carbon dioxide occurs under biophysical conditions of the Antarctic Circumpolar Current. Stratification in shallow SML and the same absolute grazing demands by krill and

  5. Phytoplankton absorption predicts patterns in primary productivity in Australian coastal shelf waters

    Science.gov (United States)

    Robinson, C. M.; Cherukuru, N.; Hardman-Mountford, N. J.; Everett, J. D.; McLaughlin, M. J.; Davies, K. P.; Van Dongen-Vogels, V.; Ralph, P. J.; Doblin, M. A.

    2017-06-01

    The phytoplankton absorption coefficient (aPHY) has been suggested as a suitable alternate first order predictor of net primary productivity (NPP). We compiled a dataset of surface bio-optical properties and phytoplankton NPP measurements in coastal waters around Australia to examine the utility of an in-situ absorption model to estimate NPP. The magnitude of surface NPP (0.20-19.3 mmol C m-3 d-1) across sites was largely driven by phytoplankton biomass, with higher rates being attributed to the microplankton (>20 μm) size class. The phytoplankton absorption coefficient aPHY for PAR (photosynthetically active radiation; āPHY)) ranged from 0.003 to 0.073 m-1, influenced by changes in phytoplankton community composition, physiology and environmental conditions. The aPHY coefficient also reflected changes in NPP and the absorption model-derived NPP could explain 73% of the variability in measured surface NPP (n = 41; RMSE = 2.49). The absorption model was applied to two contrasting coastal locations to examine NPP dynamics: a high chlorophyll-high variation (HCHV; Port Hacking National Reference Station) and moderate chlorophyll-low variation (MCLV; Yongala National Reference Station) location in eastern Australia using the GIOP-DC satellite aPHY product. Mean daily NPP rates between 2003 and 2015 were higher at the HCHV site (1.71 ± 0.03 mmol C m-3 d-1) with the annual maximum NPP occurring during the austral winter. In contrast, the MCLV site annual NPP peak occurred during the austral wet season and had lower mean daily NPP (1.43 ± 0.03 mmol C m-3 d-1) across the time-series. An absorption-based model to estimate NPP is a promising approach for exploring the spatio-temporal dynamics in phytoplankton NPP around the Australian continental shelf.

  6. Remote sensing of particle dynamics: a two-component unmixing model in a western UK shelf sea.

    Science.gov (United States)

    Mitchell, Catherine; Cunningham, Alex

    2014-05-01

    The relationship between the backscattering and absorption coefficients, in particular the backscattering to absorption ratio, is mediated by the type of particles present in the water column. By considering the optical signals to be driven by phytoplankton and suspended minerals, with a relatively constant influence from CDOM, radiative transfer modelling is used to propose a method for retrieving the optical contribution of phytoplankton and suspended minerals to the total absorption coefficient with mean percentage errors of below 5% for both components. These contributions can be converted to constituent concentrations if the appropriate specific inherent optical properties are known or can be determined from the maximum and minimum backscattering to absorption ratios of the data. Remotely sensed absorption and backscattering coefficients from eight years of MODIS data for the Irish Sea reveal maximum backscattering to absorption coefficient ratios over the winter (with an average for the region of 0.27), which then decrease to a minimum over the summer months (with an average of 0.06) before increasing again through to winter, indicating a change in the particles present in the water column. Application of the two-component unmixing model to this data showed seasonal cycles of both phytoplankton and suspended mineral concentrations which vary in both amplitude and periodicity depending on their location. For example, in the Bristol Channel the amplitude of the suspended mineral concentration throughout one cycle is approximately 75% greater than a yearly cycle in the eastern Irish Sea. These seasonal cycles give an insight into the complex dynamics of particles in the water column, indicating the suspension of sediment throughout the winter months and the loss of sediments from the surface layer over the summer during stratification. The relationship between the timing of the phytoplankton spring bloom and changes in the availability of light in the water

  7. Seasonal changes in temperature and nutrient control of photosynthesis, respiration and growth of natural phytoplankton communities

    DEFF Research Database (Denmark)

    Stæhr, P. A.; Sand-Jensen, K.

    2006-01-01

    cultures in seasons of low ambient nutrient availability. 3. Temperature stimulation of growth and metabolism was higher at low than high ambient temperature showing that long-term temperature acclimation of the phytoplankton community before the experiments was of great importance for the measured rates...... +2, +4 and +6 °C for 2 weeks with and without addition of extra inorganic nutrients. 2. Rates of photosynthesis, respiration and growth generally increased with temperature, but this effect was strongly enhanced by high nutrient availability, and therefore was most evident for nutrient amended......1. To investigate the influence of elevated temperatures and nutrients on photosynthesis, respiration and growth of natural phytoplankton assemblages, water was collected from a eutrophic lake in spring, summer, autumn, winter and the following spring and exposed to ambient temperature and ambient...

  8. Data on abiotic (nutrients and biotic (phytoplankton quality elements in Fortuna ecologically reconstructed area (Danube Delta Biosphere Reserve - Romania

    Directory of Open Access Journals (Sweden)

    TÖRÖK Liliana

    2013-12-01

    Full Text Available The impact of inorganic nutrient enrichment on reophillic ecosystems has been observed and intensively studied in many rivers. Due to the scarcity of information on ecological conditions in the channel-network of the Danube Delta it is very important to have reliable information on the trend of the abiotic and biotic quality elements in the Danube River and channel system – in order to fulfill the Water Framework Directive objectives and to implement the rehabilitation projects in area affected by nutrient pollution. The purpose of this paper is to present, analyze and discuss the results of evaluation of nutrient variation and phytoplankton quantification obtained in Fortuna area - one of the seven reconstructed areas of the Danube Delta Biosphere Reserve. In order to improve the quality of data on phytoplankton biomass distribution from Fortuna area, in the summer of 2008 there has been used a submersible spectrofluorometer with automatic algae class determination and chlorophyll analysis (bbe Fluoro Probe. According to the results of analyses on relation between phytoplankton communities and water-column, the phytoplankton development in the channel network of the Fortuna reconstructed area seems to be influenced mainly by nitrogen concentration than by phosphorus concentration, as in case of phytoplankton development in Danube Delta’s lakes

  9. Monitoring and toxicity evaluation of phytoplankton on lithium manganese oxide adsorbents at lithium recovery pilot plant field.

    Science.gov (United States)

    Yoon, H. O.; Kim, J. A.; Kim, J. C.; Chung, K. S.; Ryu, J. H.

    2015-12-01

    For recovery of rare mineral resources such as lithium or boron from seawater, the lithium adsorbent material have been made by Korea Institute of Geoscience and Mineral Resources (KIGAM) and pilot plant was conducted in Okgye Harbor, Gangneung, Korea. The application of lithium adsorbent in pilot plant, it is important to consider the impact on the marine environment. Especially phytoplankton communities are important marine microorganism to represent marine primary product. At the same time, phytoplankton is possible to induce the decrease of lithium recovery rate due to cause of biofouling to surfaces of lithium adsorbents. Therefore long-term and periodic monitoring of phytoplankton is necessary to understand the environmental impact and biofouling problems near the lithium pilot plant. The abundance and biomass of phytoplankton have been evaluated through monthly interval sampling from February 2013 to May 2015. Abundance and species diversity of phytoplankton went up to summer from winter. When lithium adsorbents were immersing to seawater, eco-toxicities of released substances were determined using Microtox with bioluminescence bacteria Vibrio fischeri. The adsorbents were soaked in sterilized seawater and aeration for 1, 3, 5, 7, 10 and 14 days intervals under controlled temperature. Maximum EC50 concentration was 61.4% and this toxicity was showed in more than 10 days exposure.

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

    Science.gov (United States)

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

    2012-01-01

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

  11. Temporal Succession of Phytoplankton Assemblages in a Tidal Creek System of the Sundarbans Mangroves: An Integrated Approach

    Directory of Open Access Journals (Sweden)

    Dola Bhattacharjee

    2013-01-01

    Full Text Available Sundarbans, the world's largest mangrove ecosystem, is unique and biologically diverse. A study was undertaken to track temporal succession of phytoplankton assemblages at the generic level (≥10 µm encompassing 31 weeks of sampling (June 2010–May 2011 in Sundarbans based on microscopy and hydrological measurements. As part of this study, amplification and sequencing of type ID rbcL subunit of RuBisCO enzyme were also applied to infer chromophytic algal groups (≤10 µm size from one of the study points. We report the presence of 43 genera of Bacillariophyta, in addition to other phytoplankton groups, based on microscopy. Phytoplankton cell abundance, which was highest in winter and spring, ranged between 300 and 27,500 cells/L during this study. Cell biovolume varied between winter of 2010 (90–35281.04 µm3 and spring-summer of 2011 (52–33962.24 µm3. Winter supported large chain forming diatoms, while spring supported small sized diatoms, followed by other algal groups in summer. The clone library approach showed dominance of Bacillariophyta-like sequences, in addition to Cryptophyta-, Haptophyta-, Pelagophyta-, and Eustigmatophyta-like sequences which were detected for the first time highlighting their importance in mangrove ecosystem. This study clearly shows that a combination of microscopy and molecular tools can improve understanding of phytoplankton assemblages in mangrove environments.

  12. Phytoplankton variability and community structure in relation to hydrographic features in the NE Aegean frontal area (NE Mediterranean Sea)

    Science.gov (United States)

    Lagaria, A.; Mandalakis, M.; Mara, P.; Frangoulis, C.; Karatsolis, B.-Th.; Pitta, P.; Triantaphyllou, M.; Tsiola, A.; Psarra, S.

    2017-10-01

    The structure of phytoplankton community in the salinity-stratified Northeastern Aegean frontal area adjacent to the Dardanelles Straits was investigated on a seasonal basis (autumn, spring and summer) and in relation to circulating water masses: the modified Black Sea Water (BSW) and the Levantine Water (LW). By employing High Performance Liquid Chromatography (HPLC) for the analysis of phytoplankton pigments in conjunction with conventional cell counting methodologies (i.e. inverted light microscopy, flow cytometry) and primary production measurements, a comprehensive qualitative and quantitative characterization of phytoplankton community composition and its activity was conducted. Chlorophyll-a normalized production and estimated growth rates presented the highest values within the 'fresh' BSW mass during summer, though generally growth rates were low (production. Large cell organisms, and in particular diatoms, were closely associated with the surface BSW masses outflowing from the Straits. Our results showed that all phytoplankton size components were significant over time and space suggesting a rather multivorous food web functioning of the system.

  13. 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.

  14. Retention time generates short-term phytoplankton blooms in a shallow microtidal subtropical estuary

    Science.gov (United States)

    Odebrecht, Clarisse; Abreu, Paulo C.; Carstensen, Jacob

    2015-09-01

    In this study it was hypothesised that increasing water retention time promotes phytoplankton blooms in the shallow microtidal Patos Lagoon estuary (PLE). This hypothesis was tested using salinity variation as a proxy of water retention time and chlorophyll a for phytoplankton biomass. Submersible sensors fixed at 5 m depth near the mouth of PLE continuously measured water temperature, salinity and pigments fluorescence (calibrated to chlorophyll a) between March 2010 and 12th of December 2011, with some gaps. Salinity variations were used to separate alternating patterns of outflow of lagoon water (salinity 24; 35% of the time). The two transition phases represented a rapid change from lagoon water outflow to marine water inflow and a more gradually declining salinity between the dominating inflow and outflow conditions. During the latter of these, a significant chlorophyll a increase relative to that expected from a linear mixing relationship was observed at intermediate salinities (10-20). The increase in chlorophyll a was positively related to the duration of the prior coastal water inflow in the PLE. Moreover, chlorophyll a increase was significantly higher during austral spring-summer than autumn-winter, probably due to higher light and nutrient availability in the former. Moreover, the retention time process operating on time scales of days influences the long-term phytoplankton variability in this ecosystem. Comparing these results with monthly data from a nearby long-term water quality monitoring station (1993-2011) support the hypothesis that chlorophyll a accumulations occur after marine inflow events, whereas phytoplankton does not accumulate during high water outflow, when the water residence time is short. These results suggest that changing hydrological pattern is the most important mechanism underlying phytoplankton blooms in the PLE.

  15. DMSP synthesis and exudation in phytoplankton : a modeling approach

    NARCIS (Netherlands)

    Laroche, D; Vézina, A.F; Levasseur, M; Gosselin, M; Stefels, J.; Keller, M.D; Matrai, P.A; Kwint, R.L J

    1999-01-01

    In the marine environment, phytoplankton are the fundamental producers of dimethylsulfoniopropionate (DMSP), the precursor of the climatically active gas dimethylsulfide (DMS). DMSP is released by exudation, cell autolysis, and zooplankton grazing during phytoplankton blooms. In this study, we

  16. Phytoplankton and nutrients studies in Magu bay, Speke gulf, Lake ...

    African Journals Online (AJOL)

    Phytoplankton were generally dominated by the cyanobacteria Microcystis and Anabaena species though the diatoms Nitzschia and Melosira species were more abundant in some sampling ... Phytoplankton production was possibly light limited in areas with simultaneously high nutrient concentrations and high turbidity.

  17. 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...

  18. phytoplankton diversity indices of Osse River, Edo State, Nigeria

    African Journals Online (AJOL)

    USER

    The phytoplankton diversity indices of Osse River, Edo State, Nigeria, were investigated monthly from January ... In terms of abundance, Bacillariophyceae had the highest distribution of phytoplankton (79.00%), ...... erosion beach in Lagos.

  19. Phytoplankton diversity and their succession in water bodies of the Lednice park during 2002 season

    Directory of Open Access Journals (Sweden)

    Zohreh Ramezanpoor

    2004-01-01

    Full Text Available Phytoplankton communities of three water bodies in the Lednice park were studied from 22nd April till 1st October 2002. These water bodies are the Zámecký pond, Růžový pond and the Dyje River, which is water source of both ponds.Phytoplankton samples were taken every two weeks between 8 - 9 am. Collected phytoplankton samples were preserved with 4% formalin solution and Lugol solution (JJK and transported to the laboratory. They were determined and counted using inverted microscope. Water temperature, pH and dissolved oxygen were measured in the field using digital portable instruments. Total of 317 phytoplankton species were determined in this study.Heavy algal bloom was observed in the Zámecký pond in mid-summer coinciding with increase in water temperature. Fish diseases and partial mortality occurred during the period of algal bloom and unpleasant smell was dominant feature. A light algal bloom was also observed in the Růžový pond and the Dyje River nearly by the end of summer.The main algae species responsible for blue-green algae bloom were Anabaena flos-aquae, Microcystis aeruginosa, M. ichtyoblabe, M. flos-aquae and M. wesenbergii. Dissolved oxygen values varied between 3.4 - 19.5 mg l-1, pH ranged from 7.6 - 9.7. Secchi depth varied from 0- 65 cm in the Zámecký pond, 15-45 cm in the Růžový pond and 35-65 cm in the Dyje River. Concentration of total phosphate, nitrate and chlorophyll-a in the Dyje River before drainage into the Zámecký and Růžový pond verified heavy nutrient load (Total-P = 0.3, NO3- = 12 mg.l-1 of the river. Although the Dyje River is main water source for both ponds, presence of relatively different phytoplankton communities in these two ponds suggest that probably different nutrient sources might be responsible for differences in phytoplankton communities and eutrophication patterns in the Zámecký pond as compared to the Růžový pond.

  20. 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.

  1. Phytoplankton from Lake Magelungen, Central Sweden 1960-1963

    Energy Technology Data Exchange (ETDEWEB)

    Willen, Torbjoern [Inst. of Limnology, Univ of Uppsala, Uppsala (Sweden)

    1966-03-15

    The investigation of the qualitative and quantitative composition of phytoplankton in Lake Magelungen, Central Sweden, was carried out over a period of three years to illustrate the conditions before the release of waste water from the Aagesta Heat and Power Station began. Vertical sampling series were taken about once a month and samples from three different stations (named MA, MOB and MH) in the lake were analysed and compared. Most importance was laid on the quantitative composition and the differences in total volumes between the different stations. Highest volume values were always recorded in late spring and in summer. Two algal groups predominated every year, viz. chlorophytes and cyanophytes. After a moderate spring outburst caused by diatoms (Stephanodiscus, Synedra and Asterionella) peak volume values of chlorophytes were recorded in June and July. Predominating genera were Scenedesmus, Coelastrum and Pediastrum. The chlorophyte maximum was always followed by an immense development of cyanophytes (Anabaena, Aphanizomenon and Microcystis). The diatoms were well developed only during short periods, the chrysophyceans were of little significance as were all other algal groups. A marked difference existed between the Station MOB compared with the two other stations. The water at Station MOB was more polluted and several algal genera indicating the pollution were recorded. Both chlorophytes and cyanophytes were often developed in very great quantities at this station. The total volumes of phytoplankton in Lake Magelungen already are very high and the lake is to be considered as highly eutrophic. It is very possible that changes as to further additions of nutritional elements or/and changes in the thermal balance will increase the algal populations and accelerate the normal development of the lake.

  2. Phytoplankton from Lake Magelungen, Central Sweden 1960-1963

    International Nuclear Information System (INIS)

    Willen, Torbjoern

    1966-03-01

    The investigation of the qualitative and quantitative composition of phytoplankton in Lake Magelungen, Central Sweden, was carried out over a period of three years to illustrate the conditions before the release of waste water from the Aagesta Heat and Power Station began. Vertical sampling series were taken about once a month and samples from three different stations (named MA, MOB and MH) in the lake were analysed and compared. Most importance was laid on the quantitative composition and the differences in total volumes between the different stations. Highest volume values were always recorded in late spring and in summer. Two algal groups predominated every year, viz. chlorophytes and cyanophytes. After a moderate spring outburst caused by diatoms (Stephanodiscus, Synedra and Asterionella) peak volume values of chlorophytes were recorded in June and July. Predominating genera were Scenedesmus, Coelastrum and Pediastrum. The chlorophyte maximum was always followed by an immense development of cyanophytes (Anabaena, Aphanizomenon and Microcystis). The diatoms were well developed only during short periods, the chrysophyceans were of little significance as were all other algal groups. A marked difference existed between the Station MOB compared with the two other stations. The water at Station MOB was more polluted and several algal genera indicating the pollution were recorded. Both chlorophytes and cyanophytes were often developed in very great quantities at this station. The total volumes of phytoplankton in Lake Magelungen already are very high and the lake is to be considered as highly eutrophic. It is very possible that changes as to further additions of nutritional elements or/and changes in the thermal balance will increase the algal populations and accelerate the normal development of the lake

  3. Summer Meal Capacity Builder

    Data.gov (United States)

    Department of Agriculture — Allows users to search for summer meal sites from the previous summer by zip code, adding “layers” of information, such as free and reduced-price lunch participation...

  4. Effects of Phytoplankton Growth Phase on Delayed Settling Behavior of Marine Snow Aggregates at Sharp Density Transitions

    Science.gov (United States)

    Proctor, K. W.; Montgomery, Q. W.; Prairie, J. C.

    2016-02-01

    Marine snow aggregates play a fundamental role in the marine carbon cycle. Since marine snow aggregates are larger and thus sink faster than individual phytoplankton, aggregates often dominate carbon flux. Previous studies have shown that marine snow aggregates will significantly decrease their settling velocity when passing through sharp density transitions within the ocean, a phenomenon defined as delayed settling. Given the importance of aggregate settling to carbon export, these small-scale changes in aggregate settling dynamics may have significant impacts on the efficiency of the biological pump. However, there is still a lack of knowledge about how different physical properties of aggregates can affect this delayed settling. In this study, we investigated the effect of phytoplankton growth phase on delayed settling behavior. Using phytoplankton cultures stopped at four different growth phases, we formed marine snow aggregates in the laboratory in rotating cylindrical tanks. We then observed individual aggregates as they settled through a stratified tank. We will present data which illustrates that aggregates experience greatly reduced settling rates when passing through sharp density gradients and that the growth phase of the phytoplankton used to form these aggregates has a significant effect on this delayed settling behavior. A thorough understanding of the impact of phytoplankton growth phase on the delayed settling behavior of marine snow will offer insight into the way phytoplankton growth phase may influence the efficiency of the biological pump, carbon flux, and the carbon cycle as a whole.

  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. Structure and temporal variation of the phytoplankton of a macrotidal beach from the Amazon coastal zone.

    Science.gov (United States)

    Matos, Jislene B; Oliveira, Suellen M O DE; Pereira, Luci C C; Costa, Rauquírio M DA

    2016-09-01

    The present study aimed to analyze the structure and the temporal variation of the phytoplankton of Ajuruteua beach (Bragança, Pará) and to investigate the influence of environmental variables on the dynamics of this community to provide a basis about the trophic state of this environment. Biological, hydrological and hydrodynamic samplings were performed during a nyctemeral cycle in the months of November/08, March/09, June/09 and September/09. We identified 110 taxa, which were distributed among the diatoms (87.3%), dinoflagellates (11.8%) and cyanobacteria (0.9%), with the predominance of neritic species, followed by the tychoplankton species. Chlorophyll-a concentrations were the highest during the rainy period (24.5 mg m-3), whereas total phytoplankton density was higher in the dry period (1,255 x 103 cell L-1). However, phytoflagellates density was significantly higher during the rainy period. Cluster Analysis revealed the formation of four groups, which were influenced by the monthly differences in the environmental variables. The Principal Component Analysis indicated salinity and chlorophyll-a as the main variables that explained the components. Spearman correlation analysis supported the influence of these variables on the local phytoplankton community. Overall, the results obtained suggest that rainfall and strong local hydrodynamics play an important role in the dynamic of the phytoplankton of Ajuruteua beach, by influencing both environmental and biological variables.

  7. A model for variable phytoplankton stoichiometry based on cell protein regulation

    Directory of Open Access Journals (Sweden)

    J. A. Bonachela

    2013-06-01

    Full Text Available The elemental ratios of marine phytoplankton emerge from complex interactions between the biotic and abiotic components of the ocean, and reflect the plastic response of individuals to changes in their environment. The stoichiometry of phytoplankton is, thus, dynamic and dependent on the physiological state of the cell. We present a theoretical model for the dynamics of the carbon, nitrogen and phosphorus contents of a phytoplankton population. By representing the regulatory processes controlling nutrient uptake, and focusing on the relation between nutrient content and protein synthesis, our model qualitatively replicates existing experimental observations for nutrient content and ratios. The population described by our model takes up nutrients in proportions that match the input ratios for a broad range of growth conditions. In addition, there are two zones of single-nutrient limitation separated by a wide zone of co-limitation. Within the co-limitation zone, a single point can be identified where nutrients are supplied in an optimal ratio. When different species compete, the existence of a wide co-limitation zone implies a more complex pattern of coexistence and exclusion compared to previous model predictions. However, additional comprehensive laboratory experiments are needed to test our predictions. Our model contributes to the understanding of the global cycles of oceanic nitrogen and phosphorus, as well as the elemental ratios of these nutrients in phytoplankton populations.

  8. The development and decline of phytoplankton blooms in the southern Benguela upwelling region

    International Nuclear Information System (INIS)

    Brown, P.C.

    1986-10-01

    Productivity/chlorophyll a relationship are investigated with a view to estimating phytoplankton productivity from extensive chlorophyll a measurements in the southern Benguela region. Phytoplankton bloom dynamics in newly upwelled water off the Cape Peninsula are investigated on five different occasions during the upwelling season. A drogue was used to tag a 'parcel' of upwelled water which was monitored for between 4 and 8 days. In upwelling source water, mean chlorophyll a concentrations were typically low (0.7 mg.m -3 ) and nutrient concentrations were high (nitrates, silicates and phosphates were 20.8, 16.6 and 1.88 mmol.m -3 respectively). Along the drogue tracks nutrients decreased rapidly in the euphotic zone as chlorophyll increased to peak at concentrations of up to 26 mg.m -3 . Elemental changes in nitrates, silicates, phosphates and oxygen were used to estimate primary productivity. These 'Redfield productivity estimates' were similar to 14 C-uptake productivity but lower than estimates obtained from changes in particle volume. Daily rates of 14 C-uptake water column productivity ranged between 0.94 and 14.01 g C.m -2 .d -1 (mean 3.80 g C.m -2 .d -1 ) and were similar to or higher than productivity estimates reported for other upwelling areas. Phytoplankton biomass in the upper 50 metres ranged between 8 and 506 mg chll a. m -2 (mean 208 mg chll a.m -2 ). The temporal scale of phytoplankton bloom development was investigated in terms of changes in chlorophyll a concentrations in the euphotic zone. The build up and decline of the primary phytoplankton (diatom) bloom in newly upwelled water occurred within 6-8 days. The initiation of blooming was controlled by the stability of the water body. The decline of the bloom was associated with reduced nutrient levels and is considered to result mainly from phytoplankton cells sinking out of the surface layers

  9. 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.

  10. Phytoplankton community characteristics of the icebound season ...

    African Journals Online (AJOL)

    The taxonomic structure and spatial variability of phytoplankton abundance in the icebound season was obtained from the Zhalong Wetland. A total of 109 taxa were identified in all samples, 92 taxa occurring in at least two samples or the percentages over 1% in at least one sample were utilized in further study. The algal ...

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

    African Journals Online (AJOL)

    The role of algal and phytoplankton research and the focus shift to cyanobacteria, because of eutrophication in South African aquatic systems, are highlighted, which indicates the different modelling and management methods that have been used and tested. Recommendations are made for future research. Keywords: ...

  12. 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.

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

    African Journals Online (AJOL)

    It was carried out between February and July, 2014, in three distinct zones in Ogun State coastal estuary: brush park (Zone I), open water (Zone II) and wetland (Zone III). Data collected were subjected to community structure analysis using trophic state index, species richness and diversity indices. A total of 42 phytoplankton ...

  14. 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…

  15. 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...

  16. 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...

  17. 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.

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

    African Journals Online (AJOL)

    Distribution of nutrients, chlorophyll and phytoplankton primary production in ... Two cruises were undertaken in the vicinity of the Cape Frio upwelling cell ... and concentrations of nitrate, phosphate, silicate, oxygen and chlorophyll a. ... Estimates of the annual primary production for each of the water bodies were calculated.

  19. Seasonal and size-dependent variations in the phytoplankton growth and microzooplankton grazing in the southern South China Sea under the influence of the East Asian monsoon

    Science.gov (United States)

    Zhou, L.; Tan, Y.; Huang, L.; Hu, Z.; Ke, Z.

    2015-11-01

    To examine seasonal and size-dependent variations in the phytoplankton growth and microzooplankton grazing in oligotrophic tropical waters under the influence of seasonal reversing monsoon, dilution experiments were conducted during the summer of 2009 (21 May to 9 June) and winter 2010 (9 to 18 November) in the southern South China Sea (SSCS). The results showed that environmental variables, phytoplankton biomass, phytoplankton growth rate (μ), microzooplankton grazing rate (m), and correlationship (coupling) between the μ and m, rather than the microzooplankton grazing impact on phytoplankton (m/μ) significantly varied between the two seasons. Higher relative preference index (RPI) for the larger-sized (> 3 μm) phytoplankton than pico-phytoplankton (intermittent arrivals of the northeast winter monsoon could lead to the low μ and m, and the decoupling between the μ and m in the SSCS, through influencing nutrient supply to the surface water, and inducing surface seawater salinity decrease. The low m/μ (waters such as that of the SSCS.

  20. 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.

  1. Nutrients, phytoplankton, zooplankton, and macrobenthos

    Science.gov (United States)

    Rudstam, Lars G.; Holeck, Kristen T.; Watkins, James M.; Hotaling, Christopher; Lantry, Jana R.; Bowen, Kelly L.; Munawar, Mohi; Weidel, Brian C.; Barbiero, Richard; Luckey, Frederick J.; Dove, Alice; Johnson, Timothy B.; Biesinger, Zy

    2017-01-01

    Lower trophic levels support the prey fish on which most sport fish depend. Therefore, understanding the production potential of lower trophic levels is integral to the management of Lake Ontario’s fishery resources. Lower trophic-level productivity differs among offshore and nearshore waters. In the offshore, there is concern about the ability of the lake to support Alewife (Table 1) production due to a perceived decline in productivity of phytoplankton and zooplankton whereas, in the nearshore, there is a concern about excessive attached algal production (e.g., Cladophora) associated with higher nutrient concentrations—the oligotrophication of the offshore and the eutrophication of the nearshore (Mills et al. 2003; Holeck et al. 2008; Dove 2009; Koops et al. 2015; Stewart et al. 2016). Even though the collapse of the Alewife population in Lake Huron in 2003 (and the associated decline in the Chinook Salmon fishery) may have been precipitated by a cold winter (Dunlop and Riley 2013), Alewife had not returned to high abundances in Lake Huron as of 2014 (Roseman et al. 2015). Failure of the Alewife population to recover from collapse has been attributed to declines in lower trophic-level production (Barbiero et al. 2011; Bunnell et al. 2014; but see He et al. 2015). In Lake Michigan, concerns of a similar Alewife collapse led to a decrease in the number of Chinook Salmon stocked. If lower trophic-level production declines in Lake Ontario, a similar management action could be considered. On the other hand, in Lake Erie, which supplies most of the water in Lake Ontario, eutrophication is increasing and so are harmful algal blooms. Thus, there is also a concern that nutrient levels and algal blooms could increase in Lake Ontario, especially in the nearshore. Solutions to the two processes of concern—eutrophication in the nearshore and oligotrophication in the offshore—may be mutually exclusive. In either circumstance, fisheries management needs information on

  2. Spatial and seasonal variability of fractionated phytoplankton biomass and primary production in the frontal region of the Northern Adriatic Sea

    Directory of Open Access Journals (Sweden)

    M.R. VADRUCCI

    2005-06-01

    Full Text Available Spatial and seasonal patterns of variation of fractionated phytoplankton biomass and primary production and their relationships with nutrient concentrations were analyzed along an inshore - offshore gradient and in relation to the presence of a frontal system in the Northern Adriatic Sea. Sampling was carried out in winter and summer during four oceanographic cruises (June 1996 and 1997, February 1997 and 1998 as part of the PRISMA II project. Water samples for determining nutrient concentrations, phytoplankton biomass (as Chla and primary production (as 14 C assimilation were collected at five optical depths. Sampling stations were located along 2 or 4 parallel transects arranged perpendicularly to the shoreline and the frontal system. The transects were located at such a distance from the coast that the frontal system crossed them at their halfway point. Total dissolved nitrogen (TDN and total dissolved phosphorus concentrations (TDP were 12.41 ± 3 .95 mM and 0.146 ± 0 .070 mM, respectively. The values in the two seasonal periods were similar, decreasing along the inshore-offshore gradient. Values for phytoplankton biomass and primary productionwere higher in the winter than the summer cruises, and decreased, in both seasonal periods, along the inshore / offshore gradient. Moreover, in both seasonal periods, picophytoplankton dominated both biomass and productivity, (56% and 44%, respectively at stations beyond the frontal system, while microphytoplankton was more important at stations inside it (44% and 44%, respectively. Total phytoplankton biomass and primary production were directly related to nutrient concentrations. Regarding size classes, significant patterns of variation with nutrients were observed particularly for biomass. The results indicate that the size structure and function of phytoplankton guilds seem to be mediated by nutrient inflow, as well as by competitive interaction among size fractions.

  3. Constraining the variability of optical properties in the Santa Barbara Channel, CA: A phytoplankton story

    Science.gov (United States)

    Barron, Rebecca Katherine

    The research presented in this dissertation evaluates the direct relationships of phytoplankton community composition and inherent optical properties (IOP); that is, the absorption and scattering of light in the ocean. Phytoplankton community composition affect IOPs in both direct and indirect ways, thus creating challenges for optical measurements of biological and biogeochemical properties in aquatic systems. Studies were performed in the Santa Barbara Channel (SBC), CA where an array of optical and biogeochemical measurements were made. Phytoplankton community structure was characterized by an empirical orthogonal functional analysis (EOF) using phytoplankton accessory pigments. The results showed that phytoplankton community significantly correlated to all IOPs, e.g. phytoplankton specific absorption, detrital absorption, CDOM absorption and particle backscattering coefficients. Furthermore, the EOF analysis was unique in splitting the microphytoplankton size class into separate diatom and dinoflagellate regimes allowing for assessment optical property differences within the same size class, a technique previously not systematically achievable. The phytoplankton functional group dinoflagellates were particularly influential to IOPs in surprising ways. Dinoflagellates showed higher backscattering efficiencies than would be predicted based on Mie theory, and significantly influenced CDOM absorption via direct association with dissolved mycosproine-like amino acid absorption (MAA) peaks in CDOM spectra. A new index was developed in this work to quantify MAA absorption peaks in CDOM spectra, and was named the MAA Index. Prior to this research dissolved MAA absorption in natural waters was never quantified, and CDOM data containing these peaks were often disregarded and discarded from analysis. CDOM dynamics in the SBC were assessed for a 15-year study period, and this work shows that significantly large MAA Index values, e.g. MAA Index > 1, were present in

  4. Factors driving the spatiotemporal variability in phytoplankton in the Northern South China Sea

    Science.gov (United States)

    Wei, Na; Satheeswaran, Thangaraj; Jenkinson, Ian R.; Xue, Bing; Wei, Yuqiu; Liu, Haijiao; Sun, Jun

    2018-06-01

    The influence of oceanographic processes on phytoplankton diversity and community structure was examined during a cruise conducted from July to August 2012 in the northern South China Sea (nSCS). One hundred ninety seven seawater samples were collected and analyzed from 41 stations in the nSCS. A total of 215 species were identified belonging to 67 genera, mostly dominated by diatoms (67.36%) followed by dinoflagellates (28.16%). The mean cell abundance of diatoms and dinoflagellates were 1.954 × 103 cells L-1 and 0.817 × 103 cells L-1, respectively. Diatoms mainly distributed in coastal region whereas dianoflaglletes in the open sea. Margalaf's species richness (dMa) was maximum (3.96) at SQD1 station (Depth 15 m), whereas it was minimum (0.07) at SS1 (Depth 200 m). Further, Box-Whisker plot displayed that dissolved inorganic nutrients incresed with depth. Nevertheless, redundacy analysis reveled that phytoplankton density has a negative relationship with nutrients. Overall the presesant study provides latest in-depth information about how the factors influencing the phytoplankton density and diversity in the (nSCS) during summer based on the cruise data which could serve as a reference for the similar study.

  5. Zebra mussel filter feeding and food-limited production of Daphnia: Recent changes in lower trophic level dynamics of Oneida Lake, New York, U.S.A.

    Science.gov (United States)

    Horgan, M.J.; Mills, E.L.

    1999-01-01

    Exotic zebra mussels can alter lower trophic level dynamics in lakes that they colonize by consuming large quantities of phytoplankton. We simulated the indirect effects of zebra mussel grazing on Daphnia by artificially reducing phytoplankton concentration for in situ Daphnia reproduction experiments. The response of Daphnia reproduction to reduced phytoplankton was evaluated for both the in situ experiments and field observations in Oneida Lake, New York, U.S.A. Oneida Lake has had an abundant population of zebra mussels since 1992. Our experiments revealed that fecundity of individuals from two species of Daphnia was positively related to phytoplankton concentration during the spring clearwater phase, although there was no discernible effect of food concentration on fecundity in summer cyanobacteria-dominated assemblages. The experimental results suggest that Daphnia fecundity responds to chlorophyll a concentrations zebra mussels became abundant in Oneida Lake have been characterized by high water clarity, low chlorophyll concentrations, long clearwater phases, and low Daphnia biomass compared with the previous 17 years. The food web effects of zebra mussel grazing are complex and it will take more years for impacts at higher trophic levels to develop and be identified.

  6. 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.

  7. Does ecosystem variability explain phytoplankton diversity? Solving an ecological puzzle with long-term data sets

    Science.gov (United States)

    Sarker, Subrata; Lemke, Peter; Wiltshire, Karen H.

    2018-05-01

    Explaining species diversity as a function of ecosystem variability is a long-term discussion in community-ecology research. Here, we aimed to establish a causal relationship between ecosystem variability and phytoplankton diversity in a shallow-sea ecosystem. We used long-term data on biotic and abiotic factors from Helgoland Roads, along with climate data to assess the effect of ecosystem variability on phytoplankton diversity. A point cumulative semi-variogram method was used to estimate the long-term ecosystem variability. A Markov chain model was used to estimate dynamical processes of species i.e. occurrence, absence and outcompete probability. We identified that the 1980s was a period of high ecosystem variability while the last two decades were comparatively less variable. Ecosystem variability was found as an important predictor of phytoplankton diversity at Helgoland Roads. High diversity was related to low ecosystem variability due to non-significant relationship between probability of a species occurrence and absence, significant negative relationship between probability of a species occurrence and probability of a species to be outcompeted by others, and high species occurrence at low ecosystem variability. Using an exceptional marine long-term data set, this study established a causal relationship between ecosystem variability and phytoplankton diversity.

  8. Functional analysis and classification of phytoplankton based on data from an automated flow cytometer.

    Science.gov (United States)

    Malkassian, Anthony; Nerini, David; van Dijk, Mark A; Thyssen, Melilotus; Mante, Claude; Gregori, Gerald

    2011-04-01

    Analytical flow cytometry (FCM) is well suited for the analysis of phytoplankton communities in fresh and sea waters. The measurement of light scatter and autofluorescence properties of particles by FCM provides optical fingerprints, which enables different phytoplankton groups to be separated. A submersible version of the CytoSense flow cytometer (the CytoSub) has been designed for in situ autonomous sampling and analysis, making it possible to monitor phytoplankton at a short temporal scale and obtain accurate information about its dynamics. For data analysis, a manual clustering is usually performed a posteriori: data are displayed on histograms and scatterplots, and group discrimination is made by drawing and combining regions (gating). The purpose of this study is to provide greater objectivity in the data analysis by applying a nonmanual and consistent method to automatically discriminate clusters of particles. In other words, we seek for partitioning methods based on the optical fingerprints of each particle. As the CytoSense is able to record the full pulse shape for each variable, it quickly generates a large and complex dataset to analyze. The shape, length, and area of each curve were chosen as descriptors for the analysis. To test the developed method, numerical experiments were performed on simulated curves. Then, the method was applied and validated on phytoplankton cultures data. Promising results have been obtained with a mixture of various species whose optical fingerprints overlapped considerably and could not be accurately separated using manual gating. Copyright © 2011 International Society for Advancement of Cytometry.

  9. A nonlocal and periodic reaction-diffusion-advection model of a single phytoplankton species.

    Science.gov (United States)

    Peng, Rui; Zhao, Xiao-Qiang

    2016-02-01

    In this article, we are concerned with a nonlocal reaction-diffusion-advection model which describes the evolution of a single phytoplankton species in a eutrophic vertical water column where the species relies solely on light for its metabolism. The new feature of our modeling equation lies in that the incident light intensity and the death rate are assumed to be time periodic with a common period. We first establish a threshold type result on the global dynamics of this model in terms of the basic reproduction number R0. Then we derive various characterizations of R0 with respect to the vertical turbulent diffusion rate, the sinking or buoyant rate and the water column depth, respectively, which in turn give rather precise conditions to determine whether the phytoplankton persist or become extinct. Our theoretical results not only extend the existing ones for the time-independent case, but also reveal new interesting effects of the modeling parameters and the time-periodic heterogeneous environment on persistence and extinction of the phytoplankton species, and thereby suggest important implications for phytoplankton growth control.

  10. Preliminary aspects concerning phytoplankton structure in the Balta Mare – Carja 1 fish farm

    Directory of Open Access Journals (Sweden)

    Maria FETECAU

    2010-08-01

    Full Text Available The present paper presents information on the structure and the dynamics of the water ecosystem’s phytoplankton of the Carja 1 fish farm - Vaslui County, carps and Asian cyprinids are grown ascommon fish. To establish the structure and the dynamics of the phytoplankton, two samples from 6 stations were taken in the spring and in the autumn, using of a Garmin GPS 7- type navigation system.When analysing the number of individuals and the algae species present in the phytoplankton’s structure, one can notice the low development level of the vegetable plankton. From the quantity point of view, one can notice the numerical abundance of the clorophyceae in all the analysed samples. The dominant species were: Scenedesmus acuminatus, Scenedesmus quadricauda, Tetrastrum staurogenieforme. The small number of species and algae specimens determined in the phytoplankton’s structure emphasizes the reduced level of trophicity and biodiversity of the analysed ecosystem.

  11. What Controls Seasonal Variation of Phytoplankton Growth in the East China Sea?

    Science.gov (United States)

    Liu, K.; Chao, S.; Lee, H.; Gong, G.; Teng, Y.

    2009-05-01

    The seasonal variation of phytoplankton growth in the East China Sea (ECS) is simulated with a three- dimensional coupled physical-biogeochemical model, which includes discharges from Changjiang (aka the Yangtze River). The purpose is to determine the main control on the seasonality of primary productivity in the ECS shelf, which nurtures rich biological resources. The model has a horizontal resolution of 1/6 degree in the domain from 23N to 41N and from 116E to 134E, excluding the Japan/East Sea, and 33 layers in the vertical. The nitrogen-based biogeochemical model has four compartments: dissolved inorganic nitrogen (DIN), phytoplankton, zooplankton and detritus. The chlorophyll to phytoplankton ratio depends on light and DIN availability. The model is driven by monthly climatological winds with the sea surface temperature, salinity and DIN relaxed towards the climatological mean values. It successfully reproduces the observed seasonal variation of phytoplankton growth over the ECS shelf with a strong peak in later spring and summer. The modeled annual mean primary production over the entire ECS shelf is 439 mg C m-2 d-1, which falls within the reported range of 390-529 mg C m-2 d-1. It also reproduces the marked gradient of DIN across the shelf decreasing away from the Changjiang River plume. An alternative model run, Free-N, which deviates from the standard run by essentially removing nudging on DIN, generates the same seasonal pattern of primary productivity but somewhat reduced productivity. In yet another alternative run, Fix-PAR, which deviates from Free-N by removing the seasonal cycle of photosynthetically active radiation, the seasonality of primary productivity almost vanishes. These model results demonstrate that light availability is the major control on the seasonality of primary productivity. However, nutrient supply from vertical nutrient pumping and from Changjiang discharges is still important. It is the insufficient nutrient pumping that leads

  12. 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

  13. Southern Ocean Phytoplankton in a Changing Climate

    OpenAIRE

    Deppeler, Stacy L.; Davidson, Andrew T.

    2017-01-01

    Phytoplankton are the base of the Antarctic food web, sustain the wealth and diversity of life for which Antarctica is renowned, and play a critical role in biogeochemical cycles that mediate global climate. Over the vast expanse of the Southern Ocean (SO), the climate is variously predicted to experience increased warming, strengthening wind, acidification, shallowing mixed layer depths, increased light (and UV), changes in upwelling and nutrient replenishment, declining sea ice, reduced sal...

  14. Effects of Nitrogen Availability and Form on Phytoplankton Growth in a Eutrophied Estuary (Neuse River Estuary, NC, USA)

    Science.gov (United States)

    Paerl, Hans W.; Wetz, Michael S.

    2016-01-01

    Nitrogen availability and form are important controls on estuarine phytoplankton growth. This study experimentally determined the influence of urea and nitrate additions on phytoplankton growth throughout the growing season (March 2012, June 2011, August 2011) in a temperate, eutrophied estuary (Neuse River Estuary, North Carolina, USA). Photopigments (chlorophyll a and diagnostic photopigments: peridinin, fucoxanthin, alloxanthin, zeaxanthin, chlorophyll b) and microscopy-based cell counts were used as indicators of phytoplankton growth. In March, the phytoplankton community was dominated by Gyrodinium instriatum and only fucoxanthin-based growth rates were stimulated by nitrogen addition. The limited response to nitrogen suggests other factors may control phytoplankton growth and community composition in early spring. In June, inorganic nitrogen concentrations were low and stimulatory effects of both nitrogen forms were observed for chlorophyll a- and diagnostic photopigment-based growth rates. In contrast, cell counts showed that only cryptophyte and dinoflagellate (Heterocapsa rotundata) growth were stimulated. Responses of other photopigments may have been due to an increase in pigment per cell or growth of plankton too small to be counted with the microscopic methods used. Despite high nitrate concentrations in August, growth rates were elevated in response to urea and/or nitrate addition for all photopigments except peridinin. However, this response was not observed in cell counts, again suggesting that pigment-based growth responses may not always be indicative of a true community and/or taxa-specific growth response. This highlights the need to employ targeted microscopy-based cell enumeration concurrent with pigment-based technology to facilitate a more complete understanding of phytoplankton dynamics in estuarine systems. These results are consistent with previous studies showing the seasonal importance of nitrogen availability in estuaries, and also

  15. Effects of Nitrogen Availability and Form on Phytoplankton Growth in a Eutrophied Estuary (Neuse River Estuary, NC, USA).

    Science.gov (United States)

    Cira, Emily K; Paerl, Hans W; Wetz, Michael S

    2016-01-01

    Nitrogen availability and form are important controls on estuarine phytoplankton growth. This study experimentally determined the influence of urea and nitrate additions on phytoplankton growth throughout the growing season (March 2012, June 2011, August 2011) in a temperate, eutrophied estuary (Neuse River Estuary, North Carolina, USA). Photopigments (chlorophyll a and diagnostic photopigments: peridinin, fucoxanthin, alloxanthin, zeaxanthin, chlorophyll b) and microscopy-based cell counts were used as indicators of phytoplankton growth. In March, the phytoplankton community was dominated by Gyrodinium instriatum and only fucoxanthin-based growth rates were stimulated by nitrogen addition. The limited response to nitrogen suggests other factors may control phytoplankton growth and community composition in early spring. In June, inorganic nitrogen concentrations were low and stimulatory effects of both nitrogen forms were observed for chlorophyll a- and diagnostic photopigment-based growth rates. In contrast, cell counts showed that only cryptophyte and dinoflagellate (Heterocapsa rotundata) growth were stimulated. Responses of other photopigments may have been due to an increase in pigment per cell or growth of plankton too small to be counted with the microscopic methods used. Despite high nitrate concentrations in August, growth rates were elevated in response to urea and/or nitrate addition for all photopigments except peridinin. However, this response was not observed in cell counts, again suggesting that pigment-based growth responses may not always be indicative of a true community and/or taxa-specific growth response. This highlights the need to employ targeted microscopy-based cell enumeration concurrent with pigment-based technology to facilitate a more complete understanding of phytoplankton dynamics in estuarine systems. These results are consistent with previous studies showing the seasonal importance of nitrogen availability in estuaries, and also

  16. 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.

  17. Bioaccumulation of technetium by marine phytoplankton

    International Nuclear Information System (INIS)

    Fisher, N.S.

    1982-01-01

    /sup 95m/Tc, in the IV and VII oxidation states, was added in picomolar quantities to monocultures of seven species of marine phytoplankton, including a green algae (Dunaliella tertiolecta), a diatom (Thalassiosira pseudonana), a blue-green alga (Oscillatoria woronichinii), a prasinophyte (Testraselmis chuii), two haptophytes (Emiliania huxleyi and Cricosphaera carterae), and a dinoflagellate (Heterocapsa pygmaea). Cultures were incubated for 4 days, and uptake of Tc was periodically determined by ν spectroscopy of filtered and unfiltered samples. All the Tc remained in the water column in all flasks, but none of the species appreciably concentrated the element in either oxidation state. Mean uptake (measured as the fraction retained on filters) for all species was 0.029% for Tc(IV) and 0.023% for Tc(VII), neither of which was significantly different from the uninoculated control cultures. Wet weight concentration factors never exceeded 20 for any species, 3 orders of magnitude lower than previously reported for phytoplankton and Tc. The results indicate that phytoplankton are likely to have negligble influence on the cycling of Tc in marine systems

  18. Your Best Summer Ever

    Science.gov (United States)

    Cleaver, Samantha

    2012-01-01

    "It must be nice to have summers off." Only other teachers know just how short summer is, with much of August devoted to planning for the new school year. This article offers 17 fresh ideas for exploring, making money, and preparing for next year. Plus, a reading list that hits all the marks!

  19. Indian Summer Arts Festival


    OpenAIRE

    Martel, Yann; Tabu; Tejpal, Tarun; Kunzru, Hari

    2011-01-01

    The SFU Woodward's Cultural Unit partnered with the Indian Summer Festival Society to kick off the inaugural Indian Summer Festival. Held at the Goldcorp Centre for the Arts, it included an interactive Literature Series with notable authors from both India and Canada, including special guests Yann Martel, Bollywood superstar Tabu, journalist Tarun Tejpal, writer Hari Kunzru, and many others.

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

    International Nuclear Information System (INIS)

    Patara, Lavinia; Vichi, Marcello; Masina, Simona; Fogli, Pier Giuseppe; Manzini, Elisa

    2012-01-01

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

  2. Assessing Phytoplankton Nutritional Status and Potential Impact of Wet Deposition in Seasonally Oligotrophic Waters of the Mid-Atlantic Bight

    Science.gov (United States)

    Sedwick, P. N.; Bernhardt, P. W.; Mulholland, M. R.; Najjar, R. G.; Blumen, L. M.; Sohst, B. M.; Sookhdeo, C.; Widner, B.

    2018-04-01

    To assess phytoplankton nutritional status in seasonally oligotrophic waters of the southern Mid-Atlantic Bight, and the potential for rain to stimulate primary production in this region during summer, shipboard bioassay experiments were performed using natural seawater and phytoplankton collected north and south of the Gulf Stream. Bioassay treatments comprised iron, nitrate, iron + nitrate, iron + nitrate + phosphate, and rainwater. Phytoplankton growth was inferred from changes in chlorophyll a, inorganic nitrogen, and carbon-13 uptake, relative to unamended control treatments. Results indicated the greatest growth stimulation by iron + nitrate + phosphate, intermediate growth stimulation by rainwater, modest growth stimulation by nitrate and iron + nitrate, and no growth stimulation by iron. Based on these data and analysis of seawater and atmospheric samples, nitrogen was the proximate limiting nutrient, with a secondary limitation imposed by phosphorus. Our results imply that summer rain events increase new production in these waters by contributing nitrogen and phosphorus, with the availability of the latter setting the upper limit on rain-stimulated new production.

  3. Phytoplankton composition of Sazlidere Dam lake, Istanbul, Turkey

    Directory of Open Access Journals (Sweden)

    Nese Yilmaz

    2013-05-01

    Full Text Available The phytoplankton composition of Sazlidere Dam lake was studied at 5 sampling sites between December 2003 - November 2005. A total of 67 taxa were recorded, representing Bacillariophyta (31, Chlorophyta (18, Cyanophyta (9, Chrysophyta (1, Cryptophyta (1, Dinophyta (3 and Euglenophyta (4. Bacillariophyta members constituted the dominant phytoplankton group in terms of species number. Nygaard’s compound index value and composition of phytoplankton indicate that the trophic state of Sazlidere Dam lake was changing from oligotrophic to mesotrophic.

  4. Contrasting Patterns of Phytoplankton Assemblages in Two Coastal Ecosystems in Relation to Environmental Factors (Corsica, NW Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Marie Garrido

    2014-04-01

    Full Text Available Corsica Island is a sub-basin of the Northwestern Mediterranean Sea, with hydrological features typical of both oligotrophic systems and eutrophic coastal zones. Phytoplankton assemblages in two coastal ecosystems of Corsica (the deep Bay of Calvi and the shallow littoral of Bastia show contrasting patterns over a one-year cycle. In order to determine what drives these variations, seasonal changes in littoral phytoplankton are considered together with environmental parameters. Our methodology combined a survey of the physico-chemical structure of the subsurface water with a characterization of the phytoplankton community structure. Sampling provided a detailed record of the seasonal changes and successions that occur in these two areas. Results showed that the two sampled stations presented different phytoplankton abundance and distribution patterns, notably during the winter–spring bloom period. Successions in pico-, nano-, and microphytoplankton communities appeared mainly driven by differences in the ability to acquire nutrients, and in community-specific growth rates. Phytoplankton structure and dynamics are discussed in relation to available data on the Northwestern Mediterranean Sea. These results confirm that integrated monitoring of coastal areas is a requisite for gaining a proper understanding of marine ecosystems.

  5. Driving forces of the diel distribution of phytoplankton functional groups in a shallow tropical lake (Lake Monte Alegre, Southeast Brazil

    Directory of Open Access Journals (Sweden)

    LM. Rangel

    Full Text Available Phytoplankton vertical and diel dynamics in a small shallow lake (Lake Monte Alegre, Ribeirão Preto, state of São Paulo were investigated in two climatological periods: July 2001 (cool-dry season and March 2002 (warm-rainy season. Monte Alegre is a eutrophic reservoir, with a warm polymictic discontinuous circulation pattern. The lake was thermally stratified in both periods, although dissolved oxygen varied less in the cool-dry period. Phytoplankton biomass was higher in the warm-rainy season and the vertical distribution was stratified in both seasons. Flagellate groups (Lm, Y, W1 and W2 and functional groups typical of shallow eutrophic environments (J, X1 and Sn were important throughout the study period. The lake's thermal pattern strongly influenced the vertical distribution of the phytoplankton community in both periods. Biomass, functional groups and size classes of phytoplankton also were determined by the presence of more efficient herbivores in the lake, especially during the cool-dry period when phytoplankton biomass decreased.

  6. Negative effects of UVB-irradiated phytoplankton on life history traits and fitness of Daphnia magna

    NARCIS (Netherlands)

    Lange, de H.J.; Reeuwijk, van P.L.

    2003-01-01

    1. We tested the effect of ultraviolet-B (UVB)-irradiated phytoplankton on life history characteristics of Daphnia magna . Two phytoplankton species were used, Chlamydomonas reinhardtii and Cryptomonas pyrenoidifera . The phytoplankton species were cultured under photosynthetically active radiation

  7. A consistent structure of phytoplankton communities across the warm-cold regions of the water mass on a meridional transect in the East/Japan Sea

    Science.gov (United States)

    Kwak, Jung Hyun; Han, Eunah; Lee, Sang Heon; Park, Hyun Je; Kim, Kyung-Ryul; Kang, Chang-Keun

    2017-09-01

    Three cruises were undertaken along a meridional transect in the East/Japan Sea (EJS) in spring (May 2007), summer (July 2009), and fall (October 2012) to determine the geographic variations in phytoplankton biomass and community composition. This study revealed a gradient of surface temperature and a fluctuation of hydrographic conditions along the transect. Although a subpolar front (SPF) formed between the warm- and cold-water masses (37-40°N), no significant differences in phytoplankton biomass and community composition were detected between the southern and northern parts of the EJS. These results disprove our initial hypothesis that different water masses may contain differently structured phytoplankton communities. In the present study, isothermal layers (≤ 12 °C) fluctuated over a depth of 50 m in both warm- and cold-water masses, depending on the SPF. In contrast, the nitracline (i.e. 2.5 μM nitrate isopleth) depth was recorded within a limited range of 20-40 m in spring, 30-50 m in summer, and 40-60 m in fall. The chlorophyll a concentrations at the subsurface chlorophyll maxima (SCM) were significantly higher in spring and summer (356 ± 233 and 270 ± 182 ng L-1, respectively) than in fall (117 ± 89 ng L-1). The relative contributions of individual phytoplankton groups to the depth-integrated chlorophyll a concentration conformed to the composition of the phytoplankton community in the SCM layer, showing a dominance of diatoms (58 ± 19% in spring, 48 ± 11% in summer, and 30 ± 20% in fall). Canonical correspondence analysis revealed that the geographic structures of phytoplankton communities were strongly associated with the vertical structures of water temperature and nutrient concentration in the water column rather than with horizontal gradients of hydrographic conditions. Finally, our findings suggest that water column stability and light-nutrient availability in the euphotic zone play a key role in determining geographical consistency of

  8. Seasonal dynamics in colored dissolved organic matter in the Mediterranean Sea: Patterns and drivers

    Science.gov (United States)

    Xing, Xiaogang; Claustre, Hervé; Wang, Haili; Poteau, Antoine; D`Ortenzio, Fabrizio

    2014-01-01

    Two autonomous profiling “Bio-Argo” floats were deployed in the northwestern and eastern sub-basins of the Mediterranean Sea in 2008. They recorded at high vertical (1 m) and temporal (5 day) resolution, the vertical distribution and seasonal variation of colored dissolved organic matter (CDOM), as well as of chlorophyll-a concentration and hydrological variables. The CDOM standing stock presented a clear seasonal dynamics with the progressive summer formation and winter destruction of subsurface CDOM maxima (YSM, for Yellow Substance Maximum). It was argued that subsurface CDOM is a by-product of phytoplankton, based on two main characteristics, (1) the YSM was located at the same depth than the deep chlorophyll maximum (DCM) and (2) the CDOM increased in summer parallels the decline in chlorophyll-a. These observations suggested an indirect but tight coupling between subsurface CDOM and phytoplankton via microbial activity or planktonic foodweb interactions. Moreover, the surface CDOM variations observed both by floats and MODIS displayed different seasonal dynamics from what recorded at subsurface one. This implies that CDOM standing stock can be hardly detected by satellite. It is worthnoting that surface CDOM was found to be more related to the sea surface temperature (SST) than chlorophyll-a concentration, suggesting its physical origin, in contrast to the biological origin of YSM and subsurface standing stocks.

  9. Registration Summer Camp 2016

    CERN Multimedia

    2016-01-01

    Reminder: registration for the CERN Staff Association Summer Camp is now open for children from 4 to 6 years old.   More information on the website: http://nurseryschool.web.cern.ch/. The summer camp is open to all children. The proposed cost is 480.-CHF/week, lunch included. The camp will be open weeks 27, 28, 29 and 30, from 8:30 a.m. to 5:30 p.m. For further questions, you are welcome to contact us by email at Summer.Camp@cern.ch. CERN Staff Association

  10. Parameter constraints of grazing response functions. Implications for phytoplankton bloom initiation

    Directory of Open Access Journals (Sweden)

    Jordi Solé

    2016-09-01

    Full Text Available Phytoplankton blooms are events of production and accumulation of phytoplankton biomass that influence ecosystem dynamics and may also have effects on socio-economic activities. Among the biological factors that affect bloom dynamics, prey selection by zooplankton may play an important role. Here we consider the initial state of development of an algal bloom and analyse how a reduced grazing pressure can allow an algal species with a lower intrinsic growth rate than a competitor to become dominant. We use a simple model with two microalgal species and one zooplankton grazer to derive general relationships between phytoplankton growth and zooplankton grazing. These relationships are applied to two common grazing response functions in order to deduce the mathematical constraints that the parameters of these functions must obey to allow the dominance of the lower growth rate competitor. To assess the usefulness of the deduced relationships in a more general framework, the results are applied in the context of a multispecies ecosystem model (ERSEM.

  11. Nonresonant Double Hopf Bifurcation in Toxic Phytoplankton-Zooplankton Model with Delay

    Science.gov (United States)

    Yuan, Rui; Jiang, Weihua; Wang, Yong

    This paper investigates a toxic phytoplankton-zooplankton model with Michaelis-Menten type phytoplankton harvesting. The model has rich dynamical behaviors. It undergoes transcritical, saddle-node, fold, Hopf, fold-Hopf and double Hopf bifurcation, when the parameters change and go through some of the critical values, the dynamical properties of the system will change also, such as the stability, equilibrium points and the periodic orbit. We first study the stability of the equilibria, and analyze the critical conditions for the above bifurcations at each equilibrium. In addition, the stability and direction of local Hopf bifurcations, and the completion bifurcation set by calculating the universal unfoldings near the double Hopf bifurcation point are given by the normal form theory and center manifold theorem. We obtained that the stable coexistent equilibrium point and stable periodic orbit alternate regularly when the digestion time delay is within some finite value. That is, we derived the pattern for the occurrence, and disappearance of a stable periodic orbit. Furthermore, we calculated the approximation expression of the critical bifurcation curve using the digestion time delay and the harvesting rate as parameters, and determined a large range in terms of the harvesting rate for the phytoplankton and zooplankton to coexist in a long term.

  12. Seasonal patterns in phytoplankton photosynthetic parameters and primary production at a coastal NW Mediterranean site

    Directory of Open Access Journals (Sweden)

    Josep M. Gasol

    2016-09-01

    Full Text Available We carried out monthly photosynthesis-irradiance (P-E experiments with the 14C-method for 12 years (2003–2014 to determine the photosynthetic parameters and primary production of surface phytoplankton in the Blanes Bay Microbial Observatory, a coastal sampling station in the NW Mediterranean Sea. Our goal was to obtain seasonal trends and to establish the basis for detecting future changes of primary production in this oligotrophic area. The maximal photosynthetic rate PBmax ranged 30-fold (0.5-15 mg C mg Chl a–1 h–1, averaged 3.7 mg C mg Chl a–1 h–1 (±0.25 SE and was highest in August and lowest in April and December. We only observed photoinhibition twice. The initial or light-limited slope of the P-E relationship, αB, was low, averaging 0.007 mg C mg Chl a–1 h–1 (μmol photons m–2 s–1–1 (±0.001 SE, range 0.001-0.045 and showed the lowest values in spring (April-June. The light saturation parameter or saturation irradiance, EK, averaged 711 μmol photons m–2 s–1 (± 58.4 SE and tended to be higher in spring and lower in winter. Phytoplankton assemblages were typically dominated by picoeukaryotes in early winter, diatoms in late autumn and late winter, dinoflagellates in spring and cyanobacteria in summer. Total particulate primary production averaged 1.45 mg C m-3 h–1 (±0.13 SE with highest values in winter (up to 8.50 mg C m-3 h–1 and lowest values in summer (summer average, 0.30 mg C m-3 h–1, while chlorophyll-specific primary production averaged 2.49 mg C mg Chl a–1 h–1 (±0.19, SE and peaked in summer (up to 12.0 mg C mg Chl a–1 h–1 in August. 14C-determined phytoplankton growth rates varied between ca. 0.3 d–1 in winter and 0.5 d–1 in summer and were within 60-80% of the maximal rates of growth, based on PBmax. Chlorophyll a was a good predictor of primary production only in the winter and autumn. Seasonality appeared to explain most of the variability in the studied variables, while

  13. Seasonal patterns in phytoplankton photosynthetic parameters and primary production at a coastal NW Mediterranean site

    KAUST Repository

    Gasol, Josep M.

    2016-10-11

    We carried out monthly photosynthesis-irradiance (P-E) experiments with the 14C-method for 12 years (2003–2014) to determine the photosynthetic parameters and primary production of surface phytoplankton in the Blanes Bay Microbial Observatory, a coastal sampling station in the NW Mediterranean Sea. Our goal was to obtain seasonal trends and to establish the basis for detecting future changes of primary production in this oligotrophic area. The maximal photosynthetic rate PBmax ranged 30-fold (0.5-15 mg C mg Chl a–1 h–1), averaged 3.7 mg C mg Chl a–1 h–1 (±0.25 SE) and was highest in August and lowest in April and December. We only observed photoinhibition twice. The initial or light-limited slope of the P-E relationship, αB, was low, averaging 0.007 mg C mg Chl a–1 h–1 (μmol photons m–2 s–1)–1 (±0.001 SE, range 0.001-0.045) and showed the lowest values in spring (April-June). The light saturation parameter or saturation irradiance, EK, averaged 711 μmol photons m–2 s–1 (±58.4 SE) and tended to be higher in spring and lower in winter. Phytoplankton assemblages were typically dominated by picoeukaryotes in early winter, diatoms in late autumn and late winter, dinoflagellates in spring and cyanobacteria in summer. Total particulate primary production averaged 1.45 mg C m–3 h–1 (±0.13 SE) with highest values in winter (up to 8.50 mg C m–3 h–1) and lowest values in summer (summer average, 0.30 mg C m–3 h–1), while chlorophyll-specific primary production averaged 2.49 mg C mg Chl a–1 h–1 (±0.19, SE) and peaked in summer (up to 12.0 mg C mg Chl a–1 h–1 in August). 14C-determined phytoplankton growth rates varied between ca. 0.3 d–1 in winter and 0.5 d–1 in summer and were within 60-80% of the maximal rates of growth, based on PBmax. Chlorophyll a was a good predictor of primary production only in the winter and autumn. Seasonality appeared to explain most of the variability in the studied variables, while

  14. Spatial and temporal assessment of the initial pattern of phytoplankton population in a newly built coastal reservoir

    Science.gov (United States)

    Ren, Xiangyu; Yang, Kai; Che, Yue; Wang, Mingwei; Zhou, Lili; Chen, Liqiao

    2016-09-01

    For decades, the main threat to the water security of a metropolis, such as the city of Shanghai, has been the rapidly growing demand for water and at the same time, the decrease in water quality, including eutrophication. Therefore Shanghai shifted the preferred freshwater source to the Yangtze Estuary and constructed the Qingcaosha Reservoir, which is subject to less eutrophic water from the Yangtze River. To assess the population of phytoplankton for the first time in the newly built reservoir, this study improved an integrated method to assess the phytoplankton pattern in large-water-area reservoirs and lakes, using partial triadic analysis and Geographic Information Systems. Monthly sampling and monitoring from 10 stations in the reservoir from July 2010 to December 2011 were conducted. The study examined the common pattern of the phytoplankton population structure and determined the differences in the specific composition of the phytoplankton community during the transition period of the reservoir. The results suggest that in all but three sampling stations in the upper parts of Qingcaosha Reservoir, there was a strong common compromise in 2011. The two most important periods occurred from late summer to autumn and from winter to early spring. The former was characterized by the dominance of cyanobacteria, whereas the latter was characterized by the dominance of both chlorophyta and diatoms. Cyanobacteria ( Microcystis spp. as the main genus) were the monopolistic dominant species in the summer after reservoir operation. The statistical analysis also indicated the necessity for regular monitoring to focus on the stations in the lower parts of the reservoir and on several limited species.

  15. Variations in Spectral Absorption Properties of Phytoplankton, Non-algal Particles and Chromophoric Dissolved Organic Matter in Lake Qiandaohu

    Directory of Open Access Journals (Sweden)

    Liangliang Shi

    2017-05-01

    Full Text Available Light absorption by phytoplankton, non-algal particles (NAP and chromophoric dissolved organic matter (CDOM was investigated at 90 sites of a clear, deep artificial lake (Lake Qiandaohu to study natural variability of absorption coefficients. Our study shows that CDOM absorption is a major contributor to the total absorption signal in Lake Qiandaohu during all seasons, except autumn when it has an equivalent contribution as total particle absorption. The exponential slope of CDOM absorption varies within a narrow range around a mean value of 0.0164 nm−1 ( s d = 0.00176 nm−1. Our study finds some evidence for thIS autochthonous production of CDOM in winter and spring. Absorption by phytoplankton, and therefore its contribution to total absorption, is generally greatest in spring, suggesting that phytoplankton growth in Lake Qiandaohu occurs predominantly in the spring. Phytoplankton absorption in freshwater lakes generally has a direct relationship with chlorophyll-a concentration, similar to the one established for open ocean waters. The NAP absorption, whose relative contribution to total absorption is highest in summer, has a spectral shape that can be well fitted by an exponential function with an average slope of 0.0065 nm−1 ( s d = 0.00076 nm−1. There is significant spatial variability present in the summer of Lake Qiandaohu, especially in the northwestern and southwestern extremes where the optical properties of the water column are strongly affected by the presence of allochthonous matter. Variations in the properties of the particle absorption spectra with depths provides evidence that the water column was vertically inhomogeneous and can be monitored with an optical measurement program. Moreover, the optical inhomogeneity in winter is less obvious. Our study will support the parameterization of the Bio-optical model for Lake Qiandaohu from in situ or remotely sensing aquatic color signals.

  16. 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.

  17. 2003 SOLAS Summer School

    National Research Council Canada - National Science Library

    McGillis, Wade R

    2003-01-01

    In 2003, the United States provided support for the participation of 18 students, three research assistants, and seven lecturers in the first Surface Ocean Lower Atmosphere Study (SOLAS) Summer School...

  18. Summer Meal Sites

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — Information pertaining to Summer Meal Sites, as collected by Citiparks in the City of Pittsburgh Department of Parks and Recreation. This dataset includes the...

  19. Phytoplankton variability in relation to some environmental factors in the eastern coast of Suez Gulf, Egypt.

    Science.gov (United States)

    Nassar, Mohamed Z; El-Din, Nihal G Shams; Gharib, Samiha M

    2015-10-01

    Water samples were seasonally collected from 12 stations of the eastern coast of Suez Gulf during autumn of 2012 and winter, spring, and summer of 2013 in order to investigate phytoplankton community structure in relation to some physicochemical parameters. The study area harbored a diversified phytoplankton community (138 species), belonging to 67 genera. Four algal groups were represented and classified as Bacillariophyceae (90 species), Dinophyceae (28 species), Cyanophyceae (16 species), and Chlorophyceae (4 species). The results indicated a relative high occurrence of some species namely.; Pleurotaenium trabecula of green algae; Chaetoceros lorenzianus, Proboscia alata var. gracillima, Pseudosolenia calcar-avis, and Pseudo-nitzschia pungens of diatoms; Trichodesmium erythraeum and Pseudoanabaena limnetica of cyanophytes. Most of other algal species were fairly distributed at the selected stations of the study area. The total abundance of phytoplankton was relatively low (average of 2989 unit/L) in the eastern coast of Suez Gulf, as compared its western coast and the northern part of the Red Sea. The diversity of phytoplankton species was relatively high (2.35-3.82 nats) with an annual average of 3.22 nats in the present study. The results concluded that most of eastern coast of Suez Gulf is still healthy, relatively unpolluted, and oligotrophic area, which is clearly achieved by the low values of dissolved phosphate (0.025-0.3 μM), nitrate (0.18-1.26 μM), and dissolved ammonium (0.81-5.36 μM). Even if the occurrence of potentially harmful algae species was low, the study area should be monitored continuously. The dissolved oxygen ranged between 1.77 and 8.41 mg/L and pH values between 7.6 and 8.41. The multiple regression analysis showed that the dissolved nitrate and pH values were the most effective factors that controlled the seasonal fluctuations of phytoplankton along the eastern coast of Suez Gulf during 2012-2013.

  20. 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...

  1. Steady state of phytoplankton assemblage in tropical Lake Catemaco (Mexico)

    Czech Academy of Sciences Publication Activity Database

    Komárková, Jaroslava; Tavera, R.

    2003-01-01

    Roč. 502, - (2003), s. 187-196 ISSN 0018-8158. [Workshop of the International Association of Phytoplankton Taxonomy and Acology /13./. Castelbuono, 00.09.2002] R&D Projects: GA AV ČR KSK6005114 Keywords : lake Catemaco * phytoplankton * food web Subject RIV: EF - Botanics Impact factor: 0.720, year: 2003

  2. 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 ...

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

    African Journals Online (AJOL)

    Bacillariophyta was the most abundant group (48.17% of total phytoplankton) and was uniformly distributed in all waters, followed by Cyanobacteria (33.33%), which decreased with distance offshore. Chlorophyta, the third highest in abundance (15.5%), increased with distance offshore. A total of 92 phytoplankton species ...

  4. 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 ...

  5. 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.

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

    Science.gov (United States)

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

    2018-04-01

    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 picophytoplanktonenrichment. 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 Elsevier Inc. All rights reserved.

  7. Nutrients and toxin producing phytoplankton control algal blooms

    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 ...

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

    Digital Repository Service at National Institute of Oceanography (India)

    Devassy, V.P; Bhattathiri, P

    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...

  9. 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

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

    African Journals Online (AJOL)

    ... medium and there was no significant difference between Scenedesmus and Oscillatoria sp. whereas in the inorganic fertilizer, there was no significant difference between the growth response from all phytoplankton. All experiments lasted 14 days. Key words: Aquaculture, Phytoplankton Production, Biofertilizer, Inorganic

  11. 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 ...

  12. Community structure characteristics of phytoplankton in zhalong wetland, china

    International Nuclear Information System (INIS)

    Zhang, N.; Zang, S.S.

    2015-01-01

    In autumn 2010, the phytoplankton samples were collected in Zhalong Wetland. A total of 347 species belonging to 78 genera,6 phyla were identified, Chlorophyta and Bacillariophyta were dominated phytoplankton communities, including 143 species of Chlorophyta, 116 species of Bacillariophyta, 45 species of Cyanophyta, 39 species of Euglenophyta, 3 species of Pyrrophyta, 1 species of Chrysophyta. In the core area 66 genera, 222 species were identified, in the buffer area 63 genera, 210 species were identified, in the experiment area 63 genera, 167 species were identified. The dominant species in Zhalong Wetland included Cyclotella meneghiniana, Chlorella vulgaris, Trachelomonas volvocina, Nitzschia sp.. The average phytoplankton density was 12.13*10/sup 6/ in Zhalong Wetland, the phytoplankton density of Bacillariophyta was highest (32.82*10/sup 6/ ind L/sup -1/), and then Chlorophyta (23.73*10/sup 6/ ind L/sup -1/) and Cyanophyta (11.43*106 ind L-1), respectively. The results of cluster analysis showed that phytoplankton community structure could be divided into three types, and within-group similarities of phytoplankton community structure was not high, but inter-group non-similarity was high. Based on the species composition, phytoplankton density, phytoplankton pollution indicator, it suggested that Zhalong Wetland was mesotrophic state. (author)

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

    African Journals Online (AJOL)

    DR FONGE B

    African Journal of Environmental Science and Technology Vol. 6(6), pp. ... In the Philippines, around 67% of the mangrove has been lost over the last 60 years or so, ... Phytoplankton is an important primary producer, since ... area of 1,152 km2 and a population of about 160,000 inhabitants. It ... Phytoplankton assessment.

  14. 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 ...

  15. Under-Ice Phytoplankton Blooms Inhibited by Spring Convective Mixing in Refreezing Leads

    Science.gov (United States)

    Lowry, Kate E.; Pickart, Robert S.; Selz, Virginia; Mills, Matthew M.; Pacini, Astrid; Lewis, Kate M.; Joy-Warren, Hannah L.; Nobre, Carolina; van Dijken, Gert L.; Grondin, Pierre-Luc; Ferland, Joannie; Arrigo, Kevin R.

    2018-01-01

    Spring phytoplankton growth in polar marine ecosystems is limited by light availability beneath ice-covered waters, particularly early in the season prior to snowmelt and melt pond formation. Leads of open water increase light transmission to the ice-covered ocean and are sites of air-sea exchange. We explore the role of leads in controlling phytoplankton bloom dynamics within the sea ice zone of the Arctic Ocean. Data are presented from spring measurements in the Chukchi Sea during the Study of Under-ice Blooms In the Chukchi Ecosystem (SUBICE) program in May and June 2014. We observed that fully consolidated sea ice supported modest under-ice blooms, while waters beneath sea ice with leads had significantly lower phytoplankton biomass, despite high nutrient availability. Through an analysis of hydrographic and biological properties, we attribute this counterintuitive finding to springtime convective mixing in refreezing leads of open water. Our results demonstrate that waters beneath loosely consolidated sea ice (84-95% ice concentration) had weak stratification and were frequently mixed below the critical depth (the depth at which depth-integrated production balances depth-integrated respiration). These findings are supported by theoretical model calculations of under-ice light, primary production, and critical depth at varied lead fractions. The model demonstrates that under-ice blooms can form even beneath snow-covered sea ice in the absence of mixing but not in more deeply mixed waters beneath sea ice with refreezing leads. Future estimates of primary production should account for these phytoplankton dynamics in ice-covered waters.

  16. Summer Steelhead Distribution [ds341

    Data.gov (United States)

    California Natural Resource Agency — Summer Steelhead Distribution October 2009 Version This dataset depicts observation-based stream-level geographic distribution of anadromous summer-run steelhead...

  17. 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.

  18. Toxic phytoplankton in San Francisco Bay

    Science.gov (United States)

    Rodgers, Kristine M.; Garrison, David L.; Cloern, James E.

    1996-01-01

    The Regional Monitoring Program (RMP) was conceived and designed to document the changing distribution and effects of trace substances in San Francisco Bay, with focus on toxic contaminants that have become enriched by human inputs. However, coastal ecosystems like San Francisco Bay also have potential sources of naturally-produced toxic substances that can disrupt food webs and, under extreme circumstances, become threats to public health. The most prevalent source of natural toxins is from blooms of algal species that can synthesize metabolites that are toxic to invertebrates or vertebrates. Although San Francisco Bay is nutrient-rich, it has so far apparently been immune from the epidemic of harmful algal blooms in the world’s nutrient-enriched coastal waters. This absence of acute harmful blooms does not imply that San Francisco Bay has unique features that preclude toxic blooms. No sampling program has been implemented to document the occurrence of toxin-producing algae in San Francisco Bay, so it is difficult to judge the likelihood of such events in the future. This issue is directly relevant to the goals of RMP because harmful species of phytoplankton have the potential to disrupt ecosystem processes that support animal populations, cause severe illness or death in humans, and confound the outcomes of toxicity bioassays such as those included in the RMP. Our purpose here is to utilize existing data on the phytoplankton community of San Francisco Bay to provide a provisional statement about the occurrence, distribution, and potential threats of harmful algae in this Estuary.

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

    Science.gov (United States)

    Bermudez, A.; Rivas, D.

    2015-12-01

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

  20. Particulate matter and plankton dynamics in the Ross Sea Polynya of Terra Nova Bay during the Austral Summer 1997/98

    Science.gov (United States)

    Fonda Umani, S.; Accornero, A.; Budillon, G.; Capello, M.; Tucci, S.; Cabrini, M.; Del Negro, P.; Monti, M.; De Vittor, C.

    2002-07-01

    The structure and variability of the plankton community and the distribution and composition of suspended particulate matter, were investigated in the polynya of Terra Nova Bay (western Ross Sea) during the austral summer 1997/1998, with the ultimate objective of understanding the trophic control of carbon export from the upper water column. Sampling was conducted along a transect parallel to the shore, near the retreating ice edge at the beginning of December, closer to the coast at the beginning of February, and more offshore in late February. Hydrological casts and water sampling were performed at several depths to measure total particulate matter (TPM), particulate organic carbon (POC), biogenic silica (BSi), chlorophyll a (Chl a) and phaeopigment (Phaeo) concentrations. Subsamples were taken for counting autotrophic and heterotrophic pico- and nanoplankton and to assess the abundance and composition of microphyto- and microzooplankton. Statistical analysis identified two major groups of samples: the first included the most coastal surface samples of early December, characterized by the prevalence of autotrophic nanoplankton biomass; the second included all the remaining samples and was dominated by microphytoplankton. With regard to the relation of the plankton community composition to the biogenic suspended and sinking material, we identified the succession of three distinct periods. In early December Phaeocystis dominated the plankton assemblage in the well-mixed water column, while at the retreating ice-edge a bloom of small diatoms (ND) was developing in the lens of superficial diluted water. Concentrations of biogenic particulates were generally low and confined to the uppermost layer. The very low downward fluxes, the near absence of faecal pellets and the high Chl a/Phaeo ratios suggested that the herbivorous food web was not established yet or, at least, was not working efficiently. In early February the superficial pycnocline and the increased water

  1. Vegetation Response and Landscape Dynamics of Indian Summer Monsoon Variations during Holocene: An Eco-Geomorphological Appraisal of Tropical Evergreen Forest Subfossil Logs

    Science.gov (United States)

    Kumaran, Navnith K. P.; Padmalal, Damodaran; Nair, Madhavan K.; Limaye, Ruta B.; Guleria, Jaswant S.; Srivastava, Rashmi; Shukla, Anumeha

    2014-01-01

    The high rainfall and low sea level during Early Holocene had a significant impact on the development and sustenance of dense forest and swamp-marsh cover along the southwest coast of India. This heavy rainfall flooded the coastal plains, forest flourishing in the abandoned river channels and other low-lying areas in midland.The coastline and other areas in lowland of southwestern India supply sufficient evidence of tree trunks of wet evergreen forests getting buried during the Holocene period under varying thickness of clay, silty-clay and even in sand sequences. This preserved subfossil log assemblage forms an excellent proxy for eco-geomorphological and palaeoclimate appraisal reported hitherto from Indian subcontinent, and complements the available palynological data. The bulk of the subfossil logs and partially carbonized wood remains have yielded age prior to the Holocene transgression of 6.5 k yrs BP, suggesting therein that flooding due to heavy rainfall drowned the forest cover, even extending to parts of the present shelf. These preserved logs represent a unique palaeoenvironmental database as they contain observable cellular structure. Some of them can even be compared to modern analogues. As these woods belong to the Late Pleistocene and Holocene, they form a valuable source of climate data that alleviates the lack of contemporaneous meteorological records. These palaeoforests along with pollen proxies depict the warmer environment in this region, which is consistent with a Mid Holocene Thermal Maximum often referred to as Holocene Climate Optimum. Thus, the subfossil logs of tropical evergreen forests constitute new indices of Asian palaeomonsoon, while their occurrence and preservation are attributed to eco-geomorphology and hydrological regimes associated with the intensified Asian Summer Monsoon, as recorded elsewhere. PMID:24727672

  2. Phytoplankton chemotaxonomy in the Atlantic sector of the Southern Ocean during late summer 2009

    CSIR Research Space (South Africa)

    Gibberd, M-J

    2013-08-01

    Full Text Available chlorophyll-a (chl-a) was 41.5 mg l(sup-1) and diatoms comprised 480% of biomass. Pigment signatures representative of haptophytes-8, indicative of Phaeocystis antarctica, were dominant near the ice shelf. Chl-a concentrations were 0.2–0.6 mg l(sup-1) between...

  3. Molecular diversity patterns among various phytoplankton size-fractions in West Greenland in late summer

    Science.gov (United States)

    Elferink, Stephanie; Neuhaus, Stefan; Wohlrab, Sylke; Toebe, Kerstin; Voß, Daniela; Gottschling, Marc; Lundholm, Nina; Krock, Bernd; Koch, Boris P.; Zielinski, Oliver; Cembella, Allan; John, Uwe

    2017-03-01

    Arctic regions have experienced pronounced biological and biophysical transformations as a result of global change processes over the last several decades. Current hypotheses propose an elevated impact of those environmental changes on the biodiversity, community composition and metabolic processes of species. The effects on ecosystem function and services, particularly when invasive or toxigenic harmful species become dominant, can be expressed over a wide range of temporal and spatial scales in plankton communities. Our study focused on the comparison of molecular biodiversity of three size-fractions (micro-, nano-, picoplankton) in the coastal pelagic zone of West Greenland and their association with environmental parameters. Molecular diversity was assessed via parallel amplicon sequencing the 28S rRNA hypervariable D1/D2 region. We showed that biodiversity distribution within the area of Uummannaq Fjord, Vaigat Strait and Disko Bay differed markedly within and among size-fractions. In general, we observed a higher diversity within the picoplankton size fraction compared to the nano- and microplankton. In multidimensional scaling analysis, community composition of all three size fractions correlated with cell size, silicate and phosphate, chlorophyll a (chl a) and dinophysistoxin (DTX). Individually, each size fraction community composition also correlated with other different environmental parameters, i.e. temperature and nitrate. We observed a more homogeneous community of the picoplankton across all stations compared to the larger size classes, despite different prevailing environmental conditions of the sampling areas. This suggests that habitat niche occupation for larger-celled species may lead to higher functional trait plasticity expressed as an enhanced range of phenotypes, whereas smaller organisms may compensate for lower potential plasticity with higher diversity. The presence of recently identified toxigenic harmful algal bloom (HAB) species (such as Alexandrium fundyense and A. ostenfeldii) in the area points out the potential risk for this vulnerable ecosystem in a changing world.

  4. 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.

  5. Anthropogenic climate change drives shift and shuffle in North Atlantic phytoplankton communities.

    Science.gov (United States)

    Barton, Andrew D; Irwin, Andrew J; Finkel, Zoe V; Stock, Charles A

    2016-03-15

    Anthropogenic climate change has shifted the biogeography and phenology of many terrestrial and marine species. Marine phytoplankton communities appear sensitive to climate change, yet understanding of how individual species may respond to anthropogenic climate change remains limited. Here, using historical environmental and phytoplankton observations, we characterize the realized ecological niches for 87 North Atlantic diatom and dinoflagellate taxa and project changes in species biogeography between mean historical (1951-2000) and future (2051-2100) ocean conditions. We find that the central positions of the core range of 74% of taxa shift poleward at a median rate of 12.9 km per decade (km⋅dec(-1)), and 90% of taxa shift eastward at a median rate of 42.7 km⋅dec(-1) The poleward shift is faster than previously reported for marine taxa, and the predominance of longitudinal shifts is driven by dynamic changes in multiple environmental drivers, rather than a strictly poleward, temperature-driven redistribution of ocean habitats. A century of climate change significantly shuffles community composition by a basin-wide median value of 16%, compared with seasonal variations of 46%. The North Atlantic phytoplankton community appears poised for marked shift and shuffle, which may have broad effects on food webs and biogeochemical cycles.

  6. Summer Camp Registrations 2018

    CERN Multimedia

    Staff Association

    2018-01-01

    Registration for the CERN SA Summer camp, for children from 4 to 6 years old, is now open. The general conditions are available on the EVE and School website: http://nurseryschool.web.cern.ch For further questions, please contact us by email at  Summer.Camp@cern.ch An inscription per week is proposed, for 450.-CHF/week, lunch included. The camp will be open on weeks 27, 28, 29 and 30, from 8:30 am to 5:30 pm. This year the theme will be Vivaldi’s Four Seasons.

  7. Phytoplankton assemblage of a small, shallow, tropical African reservoir.

    Science.gov (United States)

    Mustapha, Moshood K

    2009-12-01

    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 (p<0.05). Phytoplankton was abundant during the rainy season, but the transition period had the richest assemblage and abundance. Fluctuations in phytoplankton density were a result of seasonal changes in concentration of nutrients, grazing pressure and reservoir hydrology. The reservoir is eutrophic with excellent water quality and a diverse phytoplankton assemblage: fish production would be high. These conditions resulted from strategies such as watershed best management practices (BMPs) to control eutrophication and sedimentation, and priorities for water usage established through legislation. Additional measures are recommended to prevent oligotrophy, hypereutrophy, excessive phytoplankton bloom, toxic cyanobacteria, and run-off of organic waste and salts.

  8. 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.

  9. Control of the phytoplankton response during the SAGE experiment: A synthesis

    Science.gov (United States)

    Peloquin, Jill; Hall, Julie; Safi, Karl; Ellwood, Michael; Law, Cliff S.; Thompson, Karen; Kuparinen, Jorma; Harvey, Michael; Pickmere, Stuart

    2011-03-01

    The SOLAS Air-Sea Gas Exchange (SAGE) experiment was conducted in Sub-Antarctic waters off the east coast of the South Island of New Zealand in the late summer of 2004. This mesoscale iron enrichment experiment was unique in that chlorophyll a (chl a) and primary productivity were only 2× OUT stations values toward the end of the experiment and this enhancement was due to increased activity of non-diatomaceous species. In addition, this enhancement in activity appeared to occur without a significant build up of particulate organic carbon. Picoeukaryotes (statistically significant increase, a doubling in biomass. To better understand the controls of phytoplankton growth and biomass, we present results from a series of on-deck perturbation experiments conducted during SAGE. Results suggest that the pico-dominated phytoplankton assemblage was only weakly inhibited by iron. Diatoms with high growth rates comprised a small (food web. A primary implication of this study is that any iron-mediated gain in fixed carbon with this set of environmental conditions has a high probability of being recycled in surface waters.

  10. Simultaneous effects of light intensity and phosphorus supply on the sterol content of phytoplankton.

    Directory of Open Access Journals (Sweden)

    Maike Piepho

    Full Text Available Sterol profiles of microalgae and their change with environmental conditions are of great interest in ecological food web research and taxonomic studies alike. Here, we investigated effects of light intensity and phosphorus supply on the sterol content of phytoplankton and assessed potential interactive effects of these important environmental factors on the sterol composition of algae. We identified sterol contents of four common phytoplankton genera, Scenedesmus, Chlamydomonas, Cryptomonas and Cyclotella, and analysed the change in sterol content with varying light intensities in both a high-phosphorus and a low-phosphorus approach. Sterol contents increased significantly with increasing light in three out of four species. Phosphorus-limitation reversed the change of sterol content with light intensity, i.e., sterol content decreased with increasing light at low phosphorus supply. Generally sterol contents were lower in low-phosphorus cultures. In conclusion, both light and phosphorus conditions strongly affect the sterol composition of algae and hence should be considered in ecological and taxonomic studies investigating the biochemical composition of algae. Data suggest a possible sterol limitation of growth and reproduction of herbivorous crustacean zooplankton during summer when high light intensities and low phosphorus supply decrease sterol contents of algae.

  11. Effects of ultraviolet radiation on rates and size distribution of primary production by Lake Erie phytoplankton

    International Nuclear Information System (INIS)

    Hiriart, V.P.; Greenberg, B.M.; Guildford, S.J.; Smith, R.E.H.

    2002-01-01

    The impact of natural solar ultraviolet radiation (UVR), particularly UVB (297-320 nm), on phytoplankton primary production in Lake Erie was investigated during the spring and summer of 1997. Radiocarbon incorporation and size-selective filtration was used to trace total production and its distribution among particulate and dissolved pools. On average, 1-h exposures produced half the UVB-dependent inhibition of total production realized in 8-h exposures, indicating rapid kinetics of photoinhibition. Cumulative UVB-dependent photoinhibition averaged 36% in 8-h simulated surface exposures. The efficiency of photoinhibition was greater for N-deficient than N-replete communities, but was not related to phytoplankton light history, P limitation, or the dominant genera. The proportion of recently fixed carbon occurring in the dissolved pool after 8-h exposures was significantly greater in higher-UVB treatments, whereas the share in picoplankton (<2 μm) was significantly lower. Significant UVB-dependent inhibition of total production was limited on average to relatively severe exposures, but the rapid kinetics of inhibition and the apparent effects on the allocation of carbon suggest it may be important to the lake's food web. Differences in optical properties and thermal stratification patterns suggested that the relatively turbid west basin was potentially more susceptible to UVR photoinhibition than the more transparent east or central basins. (author)

  12. Species- and community-level responses combine to drive phenology of lake phytoplankton

    Science.gov (United States)

    Walters, Annika; Sagrario, María de los Ángeles González; Schindler, Daniel E.

    2013-01-01

    Global change is leading to shifts in the seasonal timing of growth and maturation for primary producers. Remote sensing is increasingly used to measure the timing of primary production in both aquatic and terrestrial ecosystems, but there is often a poor correlation between these results and direct observations of life-history responses of individual species. One explanation may be that in addition to phenological shifts, global change is also causing shifts in community composition among species with different seasonal timing of growth and maturation. We quantified how shifts in species phenology and in community composition translated into phenological change in a diverse phytoplankton community from 1962-2000. During this time the aggregate community spring-summer phytoplankton peak has shifted 63 days earlier. The mean taxon shift was only 3 days earlier and shifts in taxa phenology explained only 40% of the observed community phenological shift. The remaining community shift was attributed to dominant early season taxa increasing in abundance while a dominant late season taxon decreased in abundance. In diverse producer communities experiencing multiple stressors, changes in species composition must be considered to fully understand and predict shifts in the seasonal timing of primary production.

  13. Absorption of ultraviolet radiation by antarctic phytoplankton

    Energy Technology Data Exchange (ETDEWEB)

    Vernet, M.; Mitchell, B.G. (Univ. of California-San Diego, La Jolla (United States))

    1990-01-09

    Antarctic phytoplankton contain UV-absorbing compounds that may block damaging radiation. Compounds that absorb from 320-340 nm were observed in spectral absorption of both particulates and in methanol extracts of the particulates. The decrease in the total concentration of these UV compounds with respect to chlorophyll a, as measured by the ratio of in vitro absorption at 335 nm to absorption at 665 nm is variable and decreases with depth. We observed up to 5-fold decrease in this ratio for samples within the physically mixes surface layer. The absorption of UV radiation in methanol extracts, which peaks from 320 to 340 nm, may be composed of several compounds. Shifts in peak absorption with depth (for example, from 331 nm at surface to 321 nm at 75 m), may be interpreted as a change in composition. Ratios of protective yellow xanthophylls (diadinoxanthin + diatoxanthin) to photosynthetic fucoxanthin-like pigments have highest values in surface waters. As these pigments also absorb in the near UV, their function might extend to protection as well as utilization of UV radiation for photosynthesis. We document strong absorption in the UV from 320-330 nm for Antarctic marine particulates. Below this region of the solar energy spectrum, absolute energy levels of incident radiation drop off dramatically. Only wavelengths shorter than about 320 nm will be significantly enhanced due to ozone depletion. If the absorption we observed serves a protective role for phytoplankton photosynthesis, it appears the peak band is in the region where solar energy increases rapidly, and not in the region where depletion would cause significant variations in absolute flux.

  14. ASHRAE Summer Meeting 1998

    DEFF Research Database (Denmark)

    Rudbeck, Claus Christian

    1998-01-01

    ASHRAE's (American Society for Heating, Refrigerating and Air- Condition Engineering) summer meeting was visited in June in Toronto. ASHRAE is an American organization dealing with American problems in HVAC, but many results can be used under Danish conditions. It is therefore essential that Danish...

  15. Summer of history

    NARCIS (Netherlands)

    Burman, Jeremy Trevelyan

    2017-01-01

    This summer, the University of Groningen will host three events—yes, three—that will be of special interest to the historically- and theoretically-inclined. The meeting of the International Society for the History of Philosophy of Science (HOPOS) will be held on July 9-12, a workshop exploring the

  16. Books for Summer Reading.

    Science.gov (United States)

    Phi Delta Kappan, 1992

    1992-01-01

    Advises administrators to use their summers to relax and recharge their intellectual batteries. Reading suggestions include Edith Wharton's "House of Mirth," Charlotte Perkins Gilman's "The Yellow Wallpaper," Amy Tan's "Joy Luck Club," China Achebe's "Things Fall Apart," Paule Marshall's "The Chosen…

  17. Daily Course of CO2 Fluxes in the Atmosphere-Water System and Variable Fluorescence of Phytoplankton during the Open-Water Period for Lake Baikal according to Long-Term Measurements

    Science.gov (United States)

    Zavoruev, V. V.; Domysheva, V. M.; Pestunov, D. A.; Sakirko, M. V.; Panchenko, M. V.

    2018-04-01

    The process of gas exchange of CO2 in the atmosphere-water system and its relation to the daily course of variable fluorescence of phytoplankton is studied on the basis of long-term (2004-2014) measurements during the open water period for Lake Baikal. It is found that the decrease in photosynthetic activity of plankton is almost synchronous to the increase in the CO2 flux from atmosphere to water. It follows from comparison of the spring and summer data with December measurements that the daily decrease in variable fluorescence of phytoplankton is caused by the internal daily rhythm of the photosynthetic activity of plankton.

  18. Coupling of heterotrophic bacteria to phytoplankton bloom development at different pCO2 levels: a mesocosm study

    Directory of Open Access Journals (Sweden)

    R. Thyrhaug

    2008-07-01

    Full Text Available The predicted rise in anthropogenic CO2 emissions will increase CO2 concentrations and decrease seawater pH in the upper ocean. Recent studies have revealed effects of pCO2 induced changes in seawater chemistry on a variety of marine life forms, in particular calcifying organisms. To test whether the predicted increase in pCO2 will directly or indirectly (via changes in phytoplankton dynamics affect abundance, activities, and community composition of heterotrophic bacteria during phytoplankton bloom development, we have aerated mesocosms with CO2 to obtain triplicates with three different partial pressures of CO2 (pCO2: 350 μatm (1×CO2, 700 μatm (2×CO2 and 1050 μatm (3×CO2. The development of a phytoplankton bloom was initiated by the addition of nitrate and phosphate. In accordance to an elevated carbon to nitrogen drawdown at increasing pCO2, bacterial production (BPP of free-living and attached bacteria as well as cell-specific BPP (csBPP of attached bacteria were related to the C:N ratio of suspended matter. These relationships significantly differed among treatments. However, bacterial abundance and activities were not statistically different among treatments. Solely community structure of free-living bacteria changed with pCO2 whereas that of attached bacteria seemed to be independent of pCO2 but tightly coupled to phytoplankton bloom development. Our findings imply that changes in pCO2, although reflected by changes in community structure of free-living bacteria, do not directly affect bacterial activity. Furthermore, bacterial activity and dynamics of heterotrophic bacteria, especially of attached bacteria, were tightly correlated to phytoplankton development and, hence, may also potentially depend on changes in pCO2.

  19. Effect of toxic substance on delayed competitive allelopathic phytoplankton system with varying parameters through stability and bifurcation analysis

    International Nuclear Information System (INIS)

    Pal, D.; Mahapatra, G.S.

    2016-01-01

    Highlights: • We study a delayed two species competitive system with imprecise biological parameters. • We consider impreciseness in the form of interval number. • We introduce parametric functional form of interval number to study the model. • We study the effect of toxicant and time delay under impreciseness. • We discuss the chaotic behavior of the model. - Abstract: We have studied the combined effect of toxicant and fluctuation of the biological parameters on the dynamical behaviors of a delayed two-species competitive system with imprecise biological parameters. Due to the global increase of harmful phytoplankton blooms, the study of dynamic interactions between two competing phytoplankton species in the presence of toxic substances is an active field of research now days. The ordinary mathematical formulation of models for two competing phytoplankton species, when one or both the species liberate toxic substances, is unable to capture the oscillatory and highly variable growth of phytoplankton populations. The deterministic model never predicts the sudden localized behavior of certain species. These obstacles of mathematical modeling can be overcomed if we include interval variability of biological parameters in our modeling approach. In this investigation, we construct imprecise models of allelopathic interactions between two competing phytoplankton species as a parametric differential equation model. We incorporate the effect of toxicant on the species in two different cases known as toxic inhibition and toxic stimulatory system. We have discussed the existence of various equilibrium points and stability of the system at these equilibrium points. In case of toxic stimulatory system, the delay model exhibits a stable limit cycle oscillation. Analytical findings are supported through exhaustive numerical simulations.

  20. Estimation of new production in the North Sea: consequences for temporal and spatial variability of phytoplankton

    DEFF Research Database (Denmark)

    Richardson, Katherine; Bo Pedersen, Flemming

    1998-01-01

    By coupling knowledge of oceanographic processes and phytoplankton responses to light and nutrient availability, we estimate a total potential new (sensu Dugdale and Goering,1967) production for the North Sea of approximately 15.6 million tons C per year. In a typical year, about 40......% of this production will be associated with the spring bloom in the surface waters of the seasonally stratified (central and northern) North Sea. About 40% is predicted to occur in the coastal waters while the remaining new production is predicted to take place in sub-surface chlorophyll peaks occuring in association...... with fronts in the North Sea during summer month. By considering the inter-annual variation in heat, wind and nutrient availability (light and tidal energy input are treated as non-varying from year to year), the inter-annual variability in the new production occuring in these different regions is estimated...

  1. Forcing of dissolved organic carbon release by phytoplankton by anticyclonic mesoscale eddies in the subtropical NE Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    S. Lasternas

    2013-03-01

    Full Text Available The organic carbon fluxes mediated by planktonic communities in two cyclonic eddies (CEs and two anticyclonic eddies (AEs at the Canary Eddy Corridor were studied and compared with the dynamics in two far-field (FF stations located outside the eddies. We observed favorable conditions and signs for upwelling at the center of CEs and for downwelling and mixing at the centers of AEs. CEs were characterized by a higher concentration of nutrients and the highest concentration of chlorophyll a (chl a, associated with the highest abundance of microphytoplankton and diatoms. AEs displayed concentrations of chl a values and nutrients similar to those at the FF stations, except for the highest ammonium concentration occurring at AE and a very low concentration of phosphorus at FF stations. AEs were transient systems characterized by an increasing abundance of picophytoplankton and heterotrophic bacteria. While primary production was similar between the systems, the production of dissolved organic carbon (PDOC was significantly higher in the AEs. Phytoplankton cell mortality was lowest in the CEs, and we found higher cell mortality rates at AE than at FF stations, despite similar chl a concentration. Environmental changes in the AEs have been significantly prejudicial to phytoplankton as indicated by higher phytoplankton cell mortality (60% of diatoms cells were dead and higher cell lysis rates. The adverse conditions for phytoplankton associated with the early-stage anticyclonic systems, mainly triggered by active downwelling, resulted in higher cell mortality, forcing photosynthesized carbon to fuel the dissolved pool.

  2. Impacts of a weather event on shelf circulation and CO2 and O2 dynamics on the Louisiana shelf during summer 2009

    Science.gov (United States)

    Huang, W.-J.; Cai, W.-J.; Wang, Y.; Hopkinson, C. S.

    2013-12-01

    While much is known about the physics of coastal currents, much less is known about the biogeochemical effects of surface currents on shelf carbon dioxide (CO2) and oxygen distribution and dynamics. The Mississippi and Atchafalaya River plume is usually observed along the Louisiana shelf with easterly winds. Such a typical pattern was observed in August 2007, i.e. a plume of low salinity and low partial pressure of CO2 (pCO2), indicating high biological production on the inner shelf; and higher salinity and pCO2 on the outer shelf. This high biological production induced by riverine nitrogen flux thus provided major organic matter sources for the shelf-wide hypoxia (dissolved oxygen [DO] hypoxic area. Furthermore, DIC concentration in bottom waters was higher than those predicted by the Redfield ratio, most likely because of much rapid O2 compensation than CO2 loss during air-sea exchange. Numerical models indicate such relocation of plume was mostly affected by the shelf circulation dominated by southerly and southwesterly winds. Consequently, we conclude that wind-forcing and shelf circulation are critical factors that influence the plume trajectories and the associated biogeochemical properties in coastal waters.

  3. Remote-Sensing Estimation of Phytoplankton Size Classes From GOCI Satellite Measurements in Bohai Sea and Yellow Sea

    Science.gov (United States)

    Sun, Deyong; Huan, Yu; Qiu, Zhongfeng; Hu, Chuanmin; Wang, Shengqiang; He, Yijun

    2017-10-01

    Phytoplankton size class (PSC), a measure of different phytoplankton functional and structural groups, is a key parameter to the understanding of many marine ecological and biogeochemical processes. In turbid waters where optical properties may be influenced by terrigenous discharge and nonphytoplankton water constituents, remote estimation of PSC is still a challenging task. Here based on measurements of phytoplankton diagnostic pigments, total chlorophyll a, and spectral reflectance in turbid waters of Bohai Sea and Yellow Sea during summer 2015, a customized model is developed and validated to estimate PSC in the two semienclosed seas. Five diagnostic pigments determined through high-performance liquid chromatography (HPLC) measurements are first used to produce weighting factors to model phytoplankton biomass (using total chlorophyll a as a surrogate) with relatively high accuracies. Then, a common method used to calculate contributions of microphytoplankton, nanophytoplankton, and picophytoplankton to the phytoplankton assemblage (i.e., Fm, Fn, and Fp) is customized using local HPLC and other data. Exponential functions are tuned to model the size-specific chlorophyll a concentrations (Cm, Cn, and Cp for microphytoplankton, nanophytoplankton, and picophytoplankton, respectively) with remote-sensing reflectance (Rrs) and total chlorophyll a as the model inputs. Such a PSC model shows two improvements over previous models: (1) a practical strategy (i.e., model Cp and Cn first, and then derive Cm as C-Cp-Cn) with an optimized spectral band (680 nm) for Rrs as the model input; (2) local parameterization, including a local chlorophyll a algorithm. The performance of the PSC model is validated using in situ data that were not used in the model development. Application of the PSC model to GOCI (Geostationary Ocean Color Imager) data leads to spatial and temporal distribution patterns of phytoplankton size classes (PSCs) that are consistent with results reported from

  4. Phytoplankton community as bioindicator of fertility in belawan river

    Science.gov (United States)

    Sari Yeanny, Mayang

    2018-03-01

    Belawan River is an important river for the Medan residents and its surroundings. It serves as the main raw material for the local drinking water company, as well as domestic, industrial, hotel and tourism. Many human activities had led to the declining condition of water in the river throughout the year. One way to approach the concept of bioindicator is by knowing Abundance, Relative Abundance, Frequency of Attendance, equitability, dominance, and diversity of the phytoplankton itself. Results indicated that the phytoplankton community was from 3 different classes: Chlorophyceae, Bacillariophyceae, and Cyanophyceae. Phytoplankton individual abundance was around 2612 to 17755 ind / L. The diversity index was around 2.15 to 2.58, which is considered to have low to moderate diversity with high pollution level. Equitability Index was approaching 0, with relatively high domination from Sphaeroplea and Asterionella. The water quality that influences the diversity of phytoplankton as bioindicator was dissolved oxygen.

  5. 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...

  6. Sedimentation of phytoplankton during a diatom bloom : Rates and mechanisms

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Hansen, J.L.S.; Alldredge, A.L.

    1996-01-01

    Phytoplankton blooms are uncoupled from grazing and are normally terminated by sedimentation. There are several potential mechanisms by which phytoplankton cells may settle out of the photic zone: sinking of individual cells or chains, coagulation of cells into aggregates with high settling...... 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...... to marine snow aggregates formed from discarded larvacean houses, whereas settling of unaggregated cells was insignificant. Formation rates of phytoplankton aggregates by physical coagulation was very low, and losses by this mechanism were much less than 0.07 d(-1); phytoplankton aggregates were neither...

  7. Phytoplankton models and life history strategies | Eilertsen | African ...

    African Journals Online (AJOL)

    Phytoplankton models and life history strategies. ... Chaetoceros bloom of the growth season usually starts in mid March, initiated by C. socialis. ... in some species, inoculation events are controlled by endogenous biological clocks.

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

    African Journals Online (AJOL)

    DR. MIKE HORSFALL

    This study was carried out to provide a concise set of structural based .... further growth of diatom in this zone due to rapid uptake of ... Table 1: Taxonomic listing and spatial distribution of phytoplankton species in Cross Rivers estuary. (+ =.

  9. PHYTOPLANKTON - WET WEIGHT and Other Data (NODC Accession 9400037)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Profiles of Chlorophyll data from NASA Goddard and Phytoplankton wet weight data in this accession was submitted by Mr. Charles R. McClain of US National...

  10. 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...

  11. Large Scale Variability of Phytoplankton Blooms in the Arctic and Peripheral Seas: Relationships with Sea Ice, Temperature, Clouds, and Wind

    Science.gov (United States)

    Comiso, Josefino C.; Cota, Glenn F.

    2004-01-01

    Spatially detailed satellite data of mean color, sea ice concentration, surface temperature, clouds, and wind have been analyzed to quantify and study the large scale regional and temporal variability of phytoplankton blooms in the Arctic and peripheral seas from 1998 to 2002. In the Arctic basin, phytoplankton chlorophyll displays a large symmetry with the Eastern Arctic having about fivefold higher concentrations than those of the Western Arctic. Large monthly and yearly variability is also observed in the peripheral seas with the largest blooms occurring in the Bering Sea, Sea of Okhotsk, and the Barents Sea during spring. There is large interannual and seasonal variability in biomass with average chlorophyll concentrations in 2002 and 2001 being higher than earlier years in spring and summer. The seasonality in the latitudinal distribution of blooms is also very different such that the North Atlantic is usually most expansive in spring while the North Pacific is more extensive in autumn. Environmental factors that influence phytoplankton growth were examined, and results show relatively high negative correlation with sea ice retreat and strong positive correlation with temperature in early spring. Plankton growth, as indicated by biomass accumulation, in the Arctic and subarctic increases up to a threshold surface temperature of about 276-277 degree K (3-4 degree C) beyond which the concentrations start to decrease suggesting an optimal temperature or nutrient depletion. The correlation with clouds is significant in some areas but negligible in other areas, while the correlations with wind speed and its components are generally weak. The effects of clouds and winds are less predictable with weekly climatologies because of unknown effects of averaging variable and intermittent physical forcing (e.g. over storm event scales with mixing and upwelling of nutrients) and the time scales of acclimation by the phytoplankton.

  12. f-Ratios calculated with and without urea uptake in nitrogen uptake by phytoplankton

    Digital Repository Service at National Institute of Oceanography (India)

    Wafar, M.V.M.; Corre, P.L.; L'Helguen, S.

    . Peterson (1979) Particulate organic matter Hux and planktonic new production in the deep ocean. Nature, 282,677-6X0. Epplcy R. W., .I. H. Sharp, E. H. Renger, M. J. Perry and W. G. Harrison (1977) Nitrogen assimilation by phytoplankton and other... f’rogress Serres. 67, 275-2X3. Harrison W. G.. I_. R. Harris, D. M. Karl. G. A. Knauer and D. G. Redaljc (1992) Nitrogen dynamics at the Vcrtcx time-series site. DeepSea Revearch. 39, 1.535-1557. Harvey W. A. and J. Caperon (1976) The rate...

  13. Zooplankton excretion metabolites stimulate Southern Ocean phytoplankton growth

    KAUST Repository

    Coello-Camba, A.; Llabré s, M.; Duarte, Carlos M.; Agusti, Susana

    2017-01-01

    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.

  14. 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.

  15. 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.

  16. 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.

  17. Summer 2014 Pathways Report

    Science.gov (United States)

    Hand, Zachary

    2014-01-01

    Over the summer I had the exciting opportunity to work for NASA at the Kennedy Space Center as a Mission Assurance Engineering intern. When I was offered a position in mission assurance for the Safety and Mission Assurance directorate's Launch Services Division, I didn't really know what I would be doing, but I knew it would be an excellent opportunity to learn and grow professionally. In this report I will provide some background information on the Launch Services Division, as well as detail my duties and accomplishments during my time as an intern. Additionally, I will relate the significance of my work experience to my current academic work and future career goals. This report contains background information on Mission Assurance Engineering, a description of my duties and accomplishments over the summer of 2014, and relates the significance of my work experience to my school work and future career goals. It is a required document for the Pathways program.

  18. Summer season | Cafeteria closures

    CERN Multimedia

    2013-01-01

    Please note the following cafeteria closures over the summer season: Bldg. 54 closed from 29/07/2013 to 06/09/2013. Bldg. 13: closed from 13/07/2013 to 06/09/2013. Restaurant No. 2, table service (brasserie and restaurant): closed from 01/08/2013 to 06/09/2013. Bldg. 864: closed from 29/07/2013 to 06/09/2013. Bldg. 865: closed from 29/07/2013 to 06/09/2013.

  19. Summer and Autumn activities

    CERN Multimedia

    Staff Association

    2013-01-01

    Time to recharge the batteries, and much more… The summer holidays are an ideal opportunity to spend more time with the family, to discover new countries, make new friends, in other words to take time away from the daily grind. This recharging is essential to your work-life balance, and CERN, as a modern and socially responsible employer, has recognized this as a central part of its human resources policy.Nevertheless we should not forget that, while many of you enjoy a well-deserved summer break, some of our colleagues are hard at work making LS1 (first Long Shutdown) a success in order to guarantee that at the beginning of 2015 the LHC will be able to start physics in an energy range never before reached by mankind. Preparing the questionnaire and the elections to the Staff Council During this summer your delegates in the Staff Council are hard at work preparing for the upcoming five-yearly review whose content will be decided by CERN Council in June 2014. Therefore, as every five years, to ...

  20. Allegheny County Summer Food Sites

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — This data set shows the Summer Food Sites located within Allegheny County for children (18 years and younger) for breakfast and lunch during summer recess. OPEN...

  1. Multi-nutrient, multi-group model of present and future oceanic phytoplankton communities

    Directory of Open Access Journals (Sweden)

    E. Litchman

    2006-01-01

    Full Text Available Phytoplankton community composition profoundly affects patterns of nutrient cycling and the dynamics of marine food webs; therefore predicting present and future phytoplankton community structure is crucial to understand how ocean ecosystems respond to physical forcing and nutrient limitations. We develop a mechanistic model of phytoplankton communities that includes multiple taxonomic groups (diatoms, coccolithophores and prasinophytes, nutrients (nitrate, ammonium, phosphate, silicate and iron, light, and a generalist zooplankton grazer. Each taxonomic group was parameterized based on an extensive literature survey. We test the model at two contrasting sites in the modern ocean, the North Atlantic (North Atlantic Bloom Experiment, NABE and subarctic North Pacific (ocean station Papa, OSP. The model successfully predicts general patterns of community composition and succession at both sites: In the North Atlantic, the model predicts a spring diatom bloom, followed by coccolithophore and prasinophyte blooms later in the season. In the North Pacific, the model reproduces the low chlorophyll community dominated by prasinophytes and coccolithophores, with low total biomass variability and high nutrient concentrations throughout the year. Sensitivity analysis revealed that the identity of the most sensitive parameters and the range of acceptable parameters differed between the two sites. We then use the model to predict community reorganization under different global change scenarios: a later onset and extended duration of stratification, with shallower mixed layer depths due to increased greenhouse gas concentrations; increase in deep water nitrogen; decrease in deep water phosphorus and increase or decrease in iron concentration. To estimate uncertainty in our predictions, we used a Monte Carlo sampling of the parameter space where future scenarios were run using parameter combinations that produced acceptable modern day outcomes and the

  2. Interannual Variation in Phytoplankton Class-Specific Primary Production at a Global Scale

    Science.gov (United States)

    Rousseaux, Cecile Severine; Gregg, Watson W.

    2014-01-01

    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.

  3. Effects of N and P enrichment on competition between phytoplankton and benthic algae in shallow lakes: a mesocosm study : Environmental Science and Pollution Research

    NARCIS (Netherlands)

    Zhang, Xiufeng; Mei, Xueying; Gulati, Ramesh; Liu, Zhengwen

    2015-01-01

    Competition for resources between coexisting phytoplankton and benthic algae, but with different habitats and roles in functioning of lake ecosystems, profoundly affects dynamics of shallow lakes in the process of eutrophication. An experiment was conducted to test the hypothesis that combined

  4. Links between ocean properties, ice cover, and plankton dynamics on interannual time scales in the Canadian Arctic Archipelago

    Science.gov (United States)

    Hamilton, James M.; Collins, Kate; Prinsenberg, Simon J.

    2013-10-01

    A decade of instrumented mooring data from Barrow Strait in the eastern Canadian Arctic Archipelago reveals connections between sea ice, water characteristics, and zooplankton dynamics on interannual time scales. On the North side of the Strait, the timing of breakup is positively related to the timing of freezeup in the previous year and negatively related to spring water temperature. This suggests that an early freezeup insulates the ocean from a cold autumn atmosphere, allowing heat to be retained until spring when it contributes to early sea ice erosion. There is also a very strong negative association between the timing of freezeup and late summer salinity, suggesting that monitoring of salinity in real time could be used to predict freezeup. A zooplankton biomass index derived from acoustic Doppler current profiler echo intensity data is used to demonstrate that on the North side there are also strong connections between early summer water temperature and the start, length, and productivity of the zooplankton growth season. On the South side of the Strait where currents are stronger, the relationships seen on the North side were not observed. But here integrated zooplankton biomass index and measured currents are used to identify interannual variability in the zooplankton biomass being delivered downstream into Lancaster Sound. Also on the South side, two yearlong records of daily fluorescence profiles reveal a large difference in the phytoplankton biomass being delivered downstream between years and demonstrate a strong relationship between the timing of the spring phytoplankton bloom and that of breakup.

  5. Cyanobacteria-phytoplankton dynamics of a hypertrophic African lake

    CSIR Research Space (South Africa)

    Zohary, T

    1995-01-01

    Full Text Available ). The earlier years of the study (1982-1986) were drought years characterized by low water levels (10-15 m below the level at full supply), excess supply of nutrients at all times of the year, and overwhelming dominance of Microcystis aeruginosa. This K...

  6. Assessing the Roles of Iron, Macronutrients and Wet deposition in Controlling Phytoplankton Growth in Seasonally Oligotrophic Waters of the Mid-Atlantic Bight

    Science.gov (United States)

    Sedwick, P.; Mulholland, M. R.; Najjar, R.; Bernhardt, P. W.; Price, L. M.; Sohst, B. M.; Sookhdeo, C.; Widner, B.

    2016-02-01

    The role of iron supply in regulating phytoplankton production in high-nutrient, low-chlorophyll ocean regions has been well established. Less clear, however, is the importance of iron for phytoplankton processes in other oceanic settings, such as coastal and oligotrophic waters, where differential changes in the supply and removal of dissolved iron (dFe) can result in limitation or co-limitation of growth due to iron deficiency. One such region of interest is the Mid-Atlantic Bight (MAB), where previous field experiments have provided some evidence of co-limitation of algal growth by nitrogen and iron. In summer 2014 we conducted field sampling and shipboard experiments to assess the role of iron and macronutrient availability in controlling primary production in seasonally oligotrophic waters over the MAB continental slope, with a focus on the the impacts of wet deposition. Our results indicate that nitrogen was the proximate limiting nutrient, with a secondary limitation imposed by availability of phosphorus; we found no evidence for a deficiency in dFe, which was present at concentrations in the range 0.3-0.9 nM. Phytoplankton growth was clearly stimulated by the addition of natural rainwater, suggesting that summer rain events stimulate primary production in the MAB by contributing new nitrogen (primarily as ammonium) and phosphorus, whilst maintaining iron-replete conditions.

  7. Emergence of Algal Blooms: The Effects of Short-Term Variability in Water Quality on Phytoplankton Abundance, Diversity, and Community Composition in a Tidal Estuary

    Directory of Open Access Journals (Sweden)

    Todd A. Egerton

    2014-01-01

    Full Text Available Algal blooms are dynamic phenomena, often attributed to environmental parameters that vary on short timescales (e.g., hours to days. Phytoplankton monitoring programs are largely designed to examine long-term trends and interannual variability. In order to better understand and evaluate the relationships between water quality variables and the genesis of algal blooms, daily samples were collected over a 34 day period in the eutrophic Lafayette River, a tidal tributary within Chesapeake Bay’s estuarine complex, during spring 2006. During this period two distinct algal blooms occurred; the first was a cryptomonad bloom and this was followed by a bloom of the mixotrophic dinoflagellate, Gymnodinium instriatum. Chlorophyll a, nutrient concentrations, and physical and chemical parameters were measured daily along with phytoplankton abundance and community composition. While 65 phytoplankton species from eight major taxonomic groups were identified in samples and total micro- and nano-phytoplankton cell densities ranged from 5.8 × 106 to 7.8 × 107 cells L−1, during blooms, cryptomonads and G. instriatum were 91.6% and 99.0%, respectively, of the total phytoplankton biomass during blooms. The cryptomonad bloom developed following a period of rainfall and concomitant increases in inorganic nitrogen concentrations. Nitrate, nitrite and ammonium concentrations 0 to 5 days prior were positively lag-correlated with cryptomonad abundance. In contrast, the G. insriatum bloom developed during periods of low dissolved nitrogen concentrations and their abundance was negatively correlated with inorganic nitrogen concentrations.

  8. Phytoplankton biomass and composition in a well-flushed, sub-tropical estuary: The contrasting effects of hydrology, nutrient loads and allochthonous influences.

    Science.gov (United States)

    Hart, J A; Phlips, E J; Badylak, S; Dix, N; Petrinec, K; Mathews, A L; Green, W; Srifa, A

    2015-12-01

    The primary objective of this study was to examine trends in phytoplankton biomass and species composition under varying nutrient load and hydrologic regimes in the Guana Tolomato Matanzas estuary (GTM), a well-flushed sub-tropical estuary located on the northeast coast of Florida. The GTM contains both regions of significant human influence and pristine areas with only modest development, providing a test case for comparing and contrasting phytoplankton community dynamics under varying degrees of nutrient load. Water temperature, salinity, Secchi disk depth, nutrient concentrations and chlorophyll concentrations were determined on a monthly basis from 2002 to 2012 at three representative sampling sites in the GTM. In addition, microscopic analyses of phytoplankton assemblages were carried out monthly for a five year period from 2005 through 2009 at all three sites. Results of this study indicate that phytoplankton biomass and composition in the GTM are strongly influenced by hydrologic factors, such as water residence times and tidal exchanges of coastal waters, which in turn are affected by shifts in climatic conditions, most prominently rainfall levels. These influences are exemplified by the observation that the region of the GTM with the longest water residence times but lowest nutrient loads exhibited the highest phytoplankton peaks of autochthonous origin. The incursion of a coastal bloom of the toxic dinoflagellate Karenia brevis into the GTM in 2007 demonstrates the potential importance of allochthonous influences on the ecosystem. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. 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-aTaiwan Island. Translation speed may be one of the important mechanisms that affect phytoplankton 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

  10. 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.

  11. 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.

  12. Next Generation Summer School

    Science.gov (United States)

    Eugenia, Marcu

    2013-04-01

    On 21.06.2010 the "Next Generation" Summer School has opened the doors for its first students. They were introduced in the astronomy world by astronomical observations, astronomy and radio-astronomy lectures, laboratory projects meant to initiate them into modern radio astronomy and radio communications. The didactic programme was structure as fallowing: 1) Astronomical elements from the visible spectrum (lectures + practical projects) 2) Radio astronomy elements (lectures + practical projects) 3) Radio communication base (didactic- recreative games) The students and professors accommodation was at the Agroturistic Pension "Popasul Iancului" situated at 800m from the Marisel Observatory. First day (summer solstice day) began with a practical activity: determination of the meridian by measurements of the shadow (the direction of one vertical alignment, when it has the smallest length). The experiment is very instructive and interesting because combines notions of physics, spatial geometry and basic astronomy elements. Next day the activities took place in four stages: the students processed the experimental data obtained on first day (on sheets of millimetre paper they represented the length of the shadow alignments according the time), each team realised its own sun quadrant, point were given considering the design and functionality of these quadrant, the four teams had to mimic important constellations on carton boards with phosphorescent sticky stars and the students, accompanied by the professors took a hiking trip to the surroundings, marking the interest point coordinates, using a GPS to establish the geographical coronations and at the end of the day the students realised a small map of central Marisel area based on the GPS data. On the third day, the students were introduced to basic notions of radio astronomy, the principal categories of artificial Earth satellites: low orbit satellites (LEO), Medium orbit satellites (MEO) and geostationary satellites (GEO

  13. Competition between a nonallelopathic phytoplankton and an allelopathic phytoplankton species under predation.

    Science.gov (United States)

    Kengwoung-Keumo, Jean-Jacques

    2016-08-01

    We propose a model of two-species competition in the chemostat for a single growth-limiting, nonreproducing resource that extends that of Roy [38]. The response functions are specified to be Michaelis-Menten, and there is no predation in Roy's work. Our model generalizes Roy's model to general uptake functions. The competition is exploitative so that species compete by decreasing the common pool of resources. The model also allows allelopathic effects of one toxin-producing species, both on itself (autotoxicity) and on its nontoxic competitor (phytotoxicity). We show that a stable coexistence equilibrium exists as long as (a) there are allelopathic effects and (b) the input nutrient concentration is above a critical value. The model is reconsidered under instantaneous nutrient recycling. We further extend this work to include a zooplankton species as a fourth interacting component to study the impact of predation on the ecosystem. The zooplankton species is allowed to feed only on the two phytoplankton species which are its perfectly substitutable resources. Each of the models is analyzed for boundedness, equilibria, stability, and uniform persistence (or permanence). Each model structure fits very well with some harmful algal bloom observations where the phytoplankton assemblage can be envisioned in two compartments, toxin producing and non-toxic. The Prymnesium parvum literature, where the suppressing effects of allelochemicals are quite pronounced, is a classic example. This work advances knowledge in an area of research becoming ever more important, which is understanding the functioning of allelopathy in food webs.

  14. Primary production of phytoplankton of Chascomus Pond (Prov. Buenos Aires (Argentina)). Critical evaluation of photosynthesis values obtained by O2 and 14 C methods

    International Nuclear Information System (INIS)

    Romero, M.C.; Arenas, P.M.

    1989-01-01

    The primary production of the phytoplankton of Chascomus pound was estimated with the dissolved oxygen and the assimilation of 14 CO 2 techniques, the laboratory, at light saturation. The bicarbonate consumptions by the phytoplankton was corrected by the excretion values, anaplerotic uptake of CO 2 by heterotrophic bacteria and for adsorption on suspended material. Gross production primary values fluctuated within 619,5 and 168,9 mg C.m -3 . h -1 , the net primary production within 564,8 (summer) and 93,8 (winter) mg C.m -3 . h -1 . Steemann Nielsen's technique subestimated the primary production in an average of the 21%; during the months of December, January and February those differences were only of the 8,6 and 1% respectively, implying that carrying out the respective corrections, both methods equalize themselves. (author)

  15. Modeling of primary production of phytoplankton in the wetland Jaboque, Bogotá D.C.

    Directory of Open Access Journals (Sweden)

    Julio Eduardo Beltrán Vargas

    2016-02-01

    Full Text Available A dynamic simulation model is presented to explain the general behavior of the  primary production of phytoplankton in the wetland Jaboque - Bogota, Colombia, in three sections with differential physical and chemical characteristics. The model takes into account the physicochemical variables, the basin area, depth, annual rainfall, water temperature, pH and concentration of chlorophyll _a. The dynamic modeling is based on differential equations and the Euler integration method is used, the modeling was developed using Stella 9.1® computer program. The model allows quantifying the primary production of phytoplankton in wetland Jaboque from chlorophyll _a monthly average concentration for each section. The results of the Ppf modeling show that Ppf concentration variations  in each section of the wetland follow a reverse pattern to the bimodal behavior of precipitation. A high degree of correspondence between the values of chlorophyll_a Ppf field and modeled in the following manner r2 = 0.86 for the first section and r2 = 0.86 and r2 = 0.79 for the remaining sections was found. Error determination was 0,57 relative to the first section and 0,35; 0,46, indicating that the results are not overstated. The model shows in general terms the functional aspects of behavior Ppf and its relation to the process of eutrophication, and it allows recommendations for the management and restoration of wetlands.

  16. Summer Camp, July 2016

    CERN Multimedia

    Staff Association

    2016-01-01

    During the month of July, the Staff Association’s Children’s Day-Care Centre and School EVEE held a summer camp for 4- to 6-year-olds. 24 children altogether joined in on the adventures. On the summer camp, the children got to “travel” to a different continent of the world every week. Day after day, they would pass through make-believe Customs upon arrival and get their passports stamped by a “customs officer”. For the first week, we went on a trip to Africa. In the spirit of the theme, the children got to do plenty of crafts and coloring, make their own little bindles and play various games. They even had the chance to visit the Museum of Ethnography in Geneva (MEG), learn to play the balafon and make musical instruments with Sterrenlab. For the second week, we set off to discover the Americas, exploring both the South and the North. Alongside different workshops (singing, dancing, storytelling, crafts), the children could enjoy several special ac...

  17. Impact of urban effluents on summer hypoxia in the highly turbid Gironde Estuary, applying a 3D model coupling hydrodynamics, sediment transport and biogeochemical processes

    Science.gov (United States)

    Lajaunie-Salla, Katixa; Wild-Allen, Karen; Sottolichio, Aldo; Thouvenin, Bénédicte; Litrico, Xavier; Abril, Gwenaël

    2017-10-01

    Estuaries are increasingly degraded due to coastal urban development and are prone to hypoxia problems. The macro-tidal Gironde Estuary is characterized by a highly concentrated turbidity maximum zone (TMZ). Field observations show that hypoxia occurs in summer in the TMZ at low river flow and a few days after the spring tide peak. In situ data highlight lower dissolved oxygen (DO) concentrations around the city of Bordeaux, located in the upper estuary. Interactions between multiple factors limit the understanding of the processes controlling the dynamics of hypoxia. A 3D biogeochemical model was developed, coupled with hydrodynamics and a sediment transport model, to assess the contribution of the TMZ and the impact of urban effluents through wastewater treatment plants (WWTPs) and sewage overflows (SOs) on hypoxia. Our model describes the transport of solutes and suspended material and the biogeochemical mechanisms impacting oxygen: primary production, degradation of all organic matter (i.e. including phytoplankton respiration, degradation of river and urban watershed matter), nitrification and gas exchange. The composition and the degradation rates of each variable were characterized by in situ measurements and experimental data from the study area. The DO model was validated against observations in Bordeaux City. The simulated DO concentrations show good agreement with field observations and satisfactorily reproduce the seasonal and neap-spring time scale variations around the city of Bordeaux. Simulations show a spatial and temporal correlation between the formation of summer hypoxia and the location of the TMZ, with minimum DO centered in the vicinity of Bordeaux. To understand the contribution of the urban watershed forcing, different simulations with the presence or absence of urban effluents were compared. Our results show that in summer, a reduction of POC from SO would increase the DO minimum in the vicinity of Bordeaux by 3% of saturation. Omitting

  18. 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.

  19. 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.

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

    Science.gov (United States)

    Mincer, Tracy J; Aicher, Athena C

    2016-01-01

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

  1. [Phytoplankton community in a recreational fishing lake, Brazil].

    Science.gov (United States)

    Matsuzaki, Mayla; Mucci, José Luiz Negrão; Rocha, Aristides Almeida

    2004-10-01

    The assessment of water quality and phytoplankton community in recreational environments allows to setting management programs aiming at preventing potential harm to human health. The purpose of the present study was to describe phytoplankton seasonal changes in a freshwater system and their relation to water quality. The recreational fishing lake is located in the southern area of the city of São Paulo, Brazil. Water samples were collected in three previously selected sites in the lake throughout a year and analyzed regarding floristic composition and physical and chemical parameters. The phytoplankton qualitative analysis revealed 91 taxa distributed among eight classes: Chlorophyceae, Cyanophyceae, Euglenophyceae, Zygnemaphyceae, Bacillariophyceae, Xantophyceae, Dinophyceae, and Chrysophyceae. Some physical and chemical parameters seemed to influence phytoplankton community behavior. Chlorophyceae development was favored by local conditions. Among the species of cyanobacteria identified, Microcystis paniformis, Cylindrospermopsis raciborskii, and Anabaena species were the most important due to their ability to produce toxins, posing a high risk to public health. Some physical and chemical parameters had an impact on the structure of phytoplankton community. The presence of Microcystis paniformis, Cylindrospermopsis raciborskii and Anabaena species indicates toxic potential and likelihood of public health problems unless there is constant monitoring. Further studies are recommended to prevent hazardous effects to the environment and public health.

  2. Application of a laser fluorometer for discriminating phytoplankton species

    Science.gov (United States)

    Chen, Peng; Pan, Delu; Mao, Zhihua

    2015-04-01

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

  3. 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

  4. 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

  5. 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.

  6. Estimating phytoplankton photosynthesis by active fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Falkowski, P.G.; Kolber, Z.

    1992-01-01

    Photosynthesis can be described by target theory, At low photon flux densities, photosynthesis is a linear function of irradiance (I), The number of reaction centers (n), their effective absorption capture cross section {sigma}, and a quantum yield {phi}. As photosynthesis becomes increasingly light saturated, an increased fraction of reaction centers close. At light saturation the maximum photosynthetic rate is given as the product of the number of reaction centers (n) and their maximum electron transport rate (I/{tau}). Using active fluorometry it is possible to measure non-destructively and in real time the fraction of open or closed reaction centers under ambient irradiance conditions in situ, as well as {sigma} and {phi} {tau} can be readily, calculated from knowledge of the light saturation parameter, I{sub k} (which can be deduced by in situ by active fluorescence measurements) and {sigma}. We built a pump and probe fluorometer, which is interfaced with a CTD. The instrument measures the fluorescence yield of a weak probe flash preceding (f{sub 0}) and succeeding (f{sub 0}) a saturating pump flash. Profiles of the these fluorescence yields are used to derive the instantaneous rate of gross photosynthesis in natural phytoplankton communities without any incubation. Correlations with short-term simulated in situ radiocarbon measurements are extremely high. The average slope between photosynthesis derived from fluorescence and that measured by radiocarbon is 1.15 and corresponds to the average photosynthetic quotient. The intercept is about 15% of the maximum radiocarbon uptake and corresponds to the average net community respiration. Profiles of photosynthesis and sections showing the variability in its composite parameters reveal a significant effect of nutrient availability on biomass specific rates of photosynthesis in the ocean.

  7. Estimating phytoplankton photosynthesis by active fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Falkowski, P.G.; Kolber, Z.

    1992-10-01

    Photosynthesis can be described by target theory, At low photon flux densities, photosynthesis is a linear function of irradiance (I), The number of reaction centers (n), their effective absorption capture cross section {sigma}, and a quantum yield {phi}. As photosynthesis becomes increasingly light saturated, an increased fraction of reaction centers close. At light saturation the maximum photosynthetic rate is given as the product of the number of reaction centers (n) and their maximum electron transport rate (I/{tau}). Using active fluorometry it is possible to measure non-destructively and in real time the fraction of open or closed reaction centers under ambient irradiance conditions in situ, as well as {sigma} and {phi} {tau} can be readily, calculated from knowledge of the light saturation parameter, I{sub k} (which can be deduced by in situ by active fluorescence measurements) and {sigma}. We built a pump and probe fluorometer, which is interfaced with a CTD. The instrument measures the fluorescence yield of a weak probe flash preceding (f{sub 0}) and succeeding (f{sub 0}) a saturating pump flash. Profiles of the these fluorescence yields are used to derive the instantaneous rate of gross photosynthesis in natural phytoplankton communities without any incubation. Correlations with short-term simulated in situ radiocarbon measurements are extremely high. The average slope between photosynthesis derived from fluorescence and that measured by radiocarbon is 1.15 and corresponds to the average photosynthetic quotient. The intercept is about 15% of the maximum radiocarbon uptake and corresponds to the average net community respiration. Profiles of photosynthesis and sections showing the variability in its composite parameters reveal a significant effect of nutrient availability on biomass specific rates of photosynthesis in the ocean.

  8. Observations of debris flows at Chalk Cliffs, Colorado, USA: Part 1, in-situ measurements of flow dynamics, tracer particle movement and video imagery from the summer of 2009

    Science.gov (United States)

    McCoy, Scott W.; Coe, Jeffrey A.; Kean, Jason W.; Tucker, Greg E.; Staley, Dennis M.; Wasklewicz, Thad A.

    2011-01-01

    Debris flows initiated by surface-water runoff during short duration, moderate- to high-intensity rainfall are common in steep, rocky, and sparsely vegetated terrain. Yet large uncertainties remain about the potential for a flow to grow through entrainment of loose debris, which make formulation of accurate mechanical models of debris-