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Sample records for living phytoplankton implications

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

    PubMed Central

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

    2011-01-01

    Phytoplankton abundance is inversely related to sea surface temperature (SST). However, a positive relationship is observed between SST and phytoplankton abundance in coastal waters of Bay of Bengal. This has led to an assertion that in a warming climate, rise in SST may increase phytoplankton blooms and, therefore, cholera outbreaks. Here, we explain why a positive SST-phytoplankton relationship exists in the Bay of Bengal and the implications of such a relationship on cholera dynamics. We found clear evidence of two independent physical drivers for phytoplankton abundance. The first one is the widely accepted phytoplankton blooming produced by the upwelling of cold, nutrient-rich deep ocean waters. The second, which explains the Bay of Bengal findings, is coastal phytoplankton blooming during high river discharges with terrestrial nutrients. Causal mechanisms should be understood when associating SST with phytoplankton and subsequent cholera outbreaks in regions where freshwater discharge are a predominant mechanism for phytoplankton production. PMID:21813852

  2. The percentage of living bacterial cells related to organic carbon release from senescent oceanic phytoplankton

    NASA Astrophysics Data System (ADS)

    Lasternas, S.; Agustí, S.

    2014-11-01

    Bacteria recycle vast amounts of organic carbon, playing key biogeochemical and ecological roles in the ocean. Bacterioplankton dynamics are expected to be dependent on phytoplankton primary production, but there is a high diversity of processes (e.g., sloppy feeding, cell exudation, viral lysis) involved in the transfer of primary production to dissolved organic carbon available to bacteria. Here, we show the percentage of living heterotrophic bacterioplankton in the subtropical NE Atlantic Ocean in relation to phytoplankton extracellular carbon release (PER). PER represents the fraction of primary production released as dissolved organic carbon. PER variability was explained by phytoplankton cell death, with communities experiencing higher phytoplankton cell mortality showing a larger proportion of phytoplankton extracellular carbon release. Both PER and the percentage of dead phytoplankton cells increased from eutrophic to oligotrophic waters, while abundance of heterotrophic bacteria was highest in the intermediate waters. The percentage of living heterotrophic bacterial cells (range: 60-95%) increased with increasing phytoplankton extracellular carbon release from productive to oligotrophic waters in the subtropical NE Atlantic. The lower PERs, observed at the upwelling waters, have resulted in a decrease in the flux of phytoplankton dissolved organic carbon (DOC) per bacterial cell. The results highlight phytoplankton cell death as a process influencing the flow of dissolved photosynthetic carbon in this region of the subtropical NE Atlantic Ocean, and suggest a close coupling between the fraction of primary production released and heterotrophic bacterial cell survival.

  3. Photoadaptation of photosynthetic carbon uptake by solitary Radiolaria: comparisons with free-living phytoplankton

    NASA Astrophysics Data System (ADS)

    Rivkin, Richard B.; Lessard, Evelyn J.

    1986-08-01

    Carbon uptake, the activity of carboxylating enzymes, and chlorophyll a concentrations of symbiont-containing radiolarians and free-living phytoplankton were examined in the Sargasso Sea. Unlike free-living phytoplankton, Radiolaria collected from the surface waters and at the base of the euphotic zone had identical photosynthetic characteristics: the assimilation ratio, photosynthetic capacity, RuBPCase activity and saturation light intensity were independent of the depth within the euphotic zone from which Radiolaria were collected. The radiolarian's intracellular environment is enriched with N and P relative to the nutrient dilute water column. Since RuBPCase can comprise a significant proportion of the symbiont's cellular nitrogen, the constant and high RuBPCase activity and photosynthetic capacity may result from the symbiotic algae devoting a larger proportion of their cellular nitrogen quota carboxylating enzymes than free-living algae.

  4. Iron limitation of a springtime bacterial and phytoplankton community in the ross sea: implications for vitamin b(12) nutrition.

    PubMed

    Bertrand, Erin M; Saito, Mak A; Lee, Peter A; Dunbar, Robert B; Sedwick, Peter N; Ditullio, Giacomo R

    2011-01-01

    The Ross Sea is home to some of the largest phytoplankton blooms in the Southern Ocean. Primary production in this system has previously been shown to be iron limited in the summer and periodically iron and vitamin B(12) colimited. In this study, we examined trace metal limitation of biological activity in the Ross Sea in the austral spring and considered possible implications for vitamin B(12) nutrition. Bottle incubation experiments demonstrated that iron limited phytoplankton growth in the austral spring while B(12), cobalt, and zinc did not. This is the first demonstration of iron limitation in a Phaeocystis antarctica-dominated, early season Ross Sea phytoplankton community. The lack of B(12) limitation in this location is consistent with previous Ross Sea studies in the austral summer, wherein vitamin additions did not stimulate P. antarctica growth and B(12) was limiting only when bacterial abundance was low. Bottle incubation experiments and a bacterial regrowth experiment also revealed that iron addition directly enhanced bacterial growth. B(12) uptake measurements in natural water samples and in an iron fertilized bottle incubation demonstrated that bacteria serve not only as a source for vitamin B(12), but also as a significant sink, and that iron additions enhanced B(12) uptake rates in phytoplankton but not bacteria. Additionally, vitamin uptake rates did not become saturated upon the addition of up to 95 pM B(12). A rapid B(12) uptake rate was observed after 13 min, which then decreased to a slower constant uptake rate over the next 52 h. Results from this study highlight the importance of iron availability in limiting early season Ross Sea phytoplankton growth and suggest that rates of vitamin B(12) production and consumption may be impacted by iron availability. PMID:21886638

  5. Iron Limitation of a Springtime Bacterial and Phytoplankton Community in the Ross Sea: Implications for Vitamin B12 Nutrition

    PubMed Central

    Bertrand, Erin M.; Saito, Mak A.; Lee, Peter A.; Dunbar, Robert B.; Sedwick, Peter N.; DiTullio, Giacomo R.

    2011-01-01

    The Ross Sea is home to some of the largest phytoplankton blooms in the Southern Ocean. Primary production in this system has previously been shown to be iron limited in the summer and periodically iron and vitamin B12 colimited. In this study, we examined trace metal limitation of biological activity in the Ross Sea in the austral spring and considered possible implications for vitamin B12 nutrition. Bottle incubation experiments demonstrated that iron limited phytoplankton growth in the austral spring while B12, cobalt, and zinc did not. This is the first demonstration of iron limitation in a Phaeocystis antarctica-dominated, early season Ross Sea phytoplankton community. The lack of B12 limitation in this location is consistent with previous Ross Sea studies in the austral summer, wherein vitamin additions did not stimulate P. antarctica growth and B12 was limiting only when bacterial abundance was low. Bottle incubation experiments and a bacterial regrowth experiment also revealed that iron addition directly enhanced bacterial growth. B12 uptake measurements in natural water samples and in an iron fertilized bottle incubation demonstrated that bacteria serve not only as a source for vitamin B12, but also as a significant sink, and that iron additions enhanced B12 uptake rates in phytoplankton but not bacteria. Additionally, vitamin uptake rates did not become saturated upon the addition of up to 95 pM B12. A rapid B12 uptake rate was observed after 13 min, which then decreased to a slower constant uptake rate over the next 52 h. Results from this study highlight the importance of iron availability in limiting early season Ross Sea phytoplankton growth and suggest that rates of vitamin B12 production and consumption may be impacted by iron availability. PMID:21886638

  6. Chromium uptake and adsorption in cultured marine phytoplankton - implications for the marine Cr cycle

    NASA Astrophysics Data System (ADS)

    Semeniuk, D.; Maldonado, M. T.; Jaccard, S.

    2015-12-01

    While chromium (Cr) is a known carcinogen and pervasive industrial contaminant, little is known about the processes that affect the distribution and speciation of Cr in uncontaminated seawater. Given the recent development and application of the stable Cr isotope system in the marine environment, a full account of the sources, sinks, and internal processes affecting the modern marine Cr cycle is prudent. Using the radioisotope 51Cr, we investigated the controls of cellular Cr accumulation in an array of marine phytoplankton grown in environmentally relevant Cr concentrations (1-10 nM). Given the affinity of Cr(III) for amorphous Fe-hydroxide mineral surfaces, and the formation of these mineral phases on the outside of phytoplankton cells, extracellular Cr was monitored in a model diatom species (Thalassiosira weissflogii) as extracellular Fe concentrations varied. Extracellular Cr in T. weissflogii increased with increasing extracellular Fe, demonstrating that Cr may be removed from seawater via extracellular adsorption to phytoplankton. Short-term Cr(VI) and Cr(III) uptake experiments performed with T. weissflogii demonstrated that Cr(III) both adsorbed to and was internalized by the cells ~20x faster than Cr(VI). This suggests that Cr(III) is the dominant oxidation state associated with phytoplankton cells. Cellular Cr:C ratios (<0.5 µmol Cr mol C-1) of the nine phytoplankton species surveyed were significantly lower than previously reported Cr:C ratios of sinking particulate organic matter (~500 µmol Cr mol C-1). Thus, Cr accumulates in sinking particles- likely as Cr(III) - as it travels to the seafloor. Given the large fractionation of stable Cr isotopes during Cr(VI) reduction, Cr associated with exported phytoplankton may be enriched in lighter Cr isotopes. These data will assist investigators using stable Cr isotopes to examine past and present Cr biogeochemical cycles.

  7. Chromium uptake and adsorption in marine phytoplankton - Implications for the marine chromium cycle

    NASA Astrophysics Data System (ADS)

    Semeniuk, David M.; Maldonado, Maria T.; Jaccard, Samuel L.

    2016-07-01

    Using the radioisotope 51Cr, we investigated the controls of cellular Cr accumulation in an array of marine phytoplankton grown in environmentally relevant Cr concentrations (1-10 nM). Given the affinity of Cr(III) for amorphous Fe-hydroxide mineral surfaces, and the formation of these mineral phases on the outside of phytoplankton cells, extracellular Cr was monitored in a model diatom species (Thalassiosira weissflogii) as extracellular Fe concentrations varied. Extracellular Cr in T. weissflogii increased with increasing extracellular Fe, demonstrating that Cr may be removed from seawater via extracellular adsorption to phytoplankton. Short-term Cr(VI) and Cr(III) uptake experiments performed with T. weissflogii demonstrated that Cr(III) was the primary oxidation state adsorbing to cells and being internalized by them. Cellular Cr:C ratios (<0.5 μmol Cr mol C-1) of the eight phytoplankton species surveyed were significantly lower than previously reported Cr:C ratios in marine particles with a high biogenic component (10-300 μmol Cr mol C-1). This indicates that Cr(III) likely accumulates in marine particles due to uptake and/or adsorption. Mass balance calculations demonstrate that surface water Cr deficits can be explained via loss of Cr(III) to exported particles, thereby providing a mechanism to account for the nutrient depth profile for Cr in modern seawater. Given the large fractionation of stable Cr isotopes during Cr(VI) reduction, Cr(III) associated with exported organic carbon is likely enriched in lighter isotopes. Most sedimentary Cr isotope studies have thus far neglected internal fractionating processes in the marine Cr cycle, but our data indicate that loss of Cr to exported particles may be traced in the sedimentary δ53Cr record.

  8. Lived religion: implications for nursing ethics.

    PubMed

    Reimer-Kirkham, Sheryl

    2009-07-01

    This article explores how ethics and religion interface in everyday life by drawing on a study examining the negotiation of religious and spiritual plurality in health care. Employing methods of critical ethnography, namely, interviews and participant observation, data were collected from patients, health care providers, administrators and spiritual care providers. The findings revealed the degree to which 'lived religion' was intertwined with 'lived ethics' for many participants; particularly for people from the Sikh faith. For these participants, religion was woven into everyday life, making distinctions between public and private, secular and sacred spaces improbable. Individual interactions, institutional resource allocation, and social discourses are all embedded in social relationships of power that prevent religion from being a solely personal or private matter. Strategies for the reintegration of religion into nursing ethics are: adjusting professional codes and theories of ethics to reflect the influence of religion; and the contribution of critical perspectives, such as postcolonial feminism, to the understanding of lived ethics. PMID:19528098

  9. MODEL OF PHYTOPLANKTON COMPETITION FOR LIMITING AND NONLIMITING NUTRIENTS: IMPLICATIONS FOR DEVELOPMENT OF ESTUARINE AND NEARSHORE MANAGEMENT SCHEMES

    EPA Science Inventory

    The global increase of noxious bloom occurrences has increased the need for phytoplankton management schemes. Such schemes require the ability to predict phytoplankton succession. Equilibrium Resources Competition theory, which is popular for predicting succession in lake systems...

  10. Living kidney donor experiences: implications for counselling.

    PubMed

    Walsh, A

    2004-01-01

    This study adds to previous, mostly quantitative, investigation into the experiences of living related kidney donors. Such investigation is important so that potential donors are supported effectively and donation programmes remain relevant and specific to need. Exploration takes place into donor decision-making processes and the most effective forms of professional support. A non-probability sampling technique highlighted eight living related kidney donors who were interviewed using a semi-structured interview format. Raw data was analysed through the qualitative technique of Interpretative Phenomenological Analysis. The decision to donate is made rapidly, decisively and rationally. Professional support provides reassurance to donors, particularly when experiencing acute psychological reaction. The need to provide support to the parents of living donors is specifically highlighted. A comprehensive range of Master Themes are generated through Interpretative Phenomenological Analysis and these reflect the complexity of the donation experience. This suggests donors are concerned with the management of psychological experience rather than with reviewing the appropriateness of an original decision to donate. Evidence indicates that concepts of attitude and self-efficacy belief can develop understanding of the psychological experience of being a living kidney donor. A counselling perspective, with Social Cognitive Theory at its core, is highlighted as a valid method for providing professional support to donors before and after surgery. PMID:15835410

  11. Temporal Succession of Ancient Phytoplankton Community in Qinghai Lake and Implication for Paleo-environmental Change.

    PubMed

    Li, Gaoyuan; Dong, Hailiang; Hou, Weiguo; Wang, Shang; Jiang, Hongchen; Yang, Jian; Wu, Geng

    2016-01-01

    Tibetan lake sediments in NW China are sensitive recorders of climate change. However, many important plankton members do not leave any microscopic features in sedimentary records. Here we used ancient DNA preserved in Qinghai Lake sediments to reconstruct the temporal succession of plankton communities in the past 18,500 years. Our results showed that seven classes and sixteen genera of phytoplankton in the lake underwent major temporal changes, in correlation with known climatic events. Trebouxiophyceae and Eustigmatophyceae were predominant during the cold periods, whereas Chlorophyceae, Phaeophyceae, Xanthophyceae, Bacillariophyceae, and Cyanophyceae were abundant during the warm periods. The inferred changes in temperature, nutrients, precipitation, and salinity, as driven by the Westerlies and summer Monsoon strength, likely contributed to these observed temporal changes. Based on these correlations, we propose the phytoplankton index as a proxy to reconstruct the stadial versus interstadial climate change history in Qinghai Lake. This taxon-specific index is free of terrestrial contamination, sensitive to short-term climatic oscillations, and continuous in recording all climatic events in the lake. The validity of this index and its applicability to other lakes is demonstrated by its good correlations with multiple climate records of Qinghai Lake and another lake on the Tibetan Plateau, Kusai Lake. PMID:26805936

  12. Temporal Succession of Ancient Phytoplankton Community in Qinghai Lake and Implication for Paleo-environmental Change

    PubMed Central

    Li, Gaoyuan; Dong, Hailiang; Hou, Weiguo; Wang, Shang; Jiang, Hongchen; Yang, Jian; Wu, Geng

    2016-01-01

    Tibetan lake sediments in NW China are sensitive recorders of climate change. However, many important plankton members do not leave any microscopic features in sedimentary records. Here we used ancient DNA preserved in Qinghai Lake sediments to reconstruct the temporal succession of plankton communities in the past 18,500 years. Our results showed that seven classes and sixteen genera of phytoplankton in the lake underwent major temporal changes, in correlation with known climatic events. Trebouxiophyceae and Eustigmatophyceae were predominant during the cold periods, whereas Chlorophyceae, Phaeophyceae, Xanthophyceae, Bacillariophyceae, and Cyanophyceae were abundant during the warm periods. The inferred changes in temperature, nutrients, precipitation, and salinity, as driven by the Westerlies and summer Monsoon strength, likely contributed to these observed temporal changes. Based on these correlations, we propose the phytoplankton index as a proxy to reconstruct the stadial versus interstadial climate change history in Qinghai Lake. This taxon-specific index is free of terrestrial contamination, sensitive to short-term climatic oscillations, and continuous in recording all climatic events in the lake. The validity of this index and its applicability to other lakes is demonstrated by its good correlations with multiple climate records of Qinghai Lake and another lake on the Tibetan Plateau, Kusai Lake. PMID:26805936

  13. Temporal Succession of Ancient Phytoplankton Community in Qinghai Lake and Implication for Paleo-environmental Change

    NASA Astrophysics Data System (ADS)

    Li, Gaoyuan; Dong, Hailiang; Hou, Weiguo; Wang, Shang; Jiang, Hongchen; Yang, Jian; Wu, Geng

    2016-01-01

    Tibetan lake sediments in NW China are sensitive recorders of climate change. However, many important plankton members do not leave any microscopic features in sedimentary records. Here we used ancient DNA preserved in Qinghai Lake sediments to reconstruct the temporal succession of plankton communities in the past 18,500 years. Our results showed that seven classes and sixteen genera of phytoplankton in the lake underwent major temporal changes, in correlation with known climatic events. Trebouxiophyceae and Eustigmatophyceae were predominant during the cold periods, whereas Chlorophyceae, Phaeophyceae, Xanthophyceae, Bacillariophyceae, and Cyanophyceae were abundant during the warm periods. The inferred changes in temperature, nutrients, precipitation, and salinity, as driven by the Westerlies and summer Monsoon strength, likely contributed to these observed temporal changes. Based on these correlations, we propose the phytoplankton index as a proxy to reconstruct the stadial versus interstadial climate change history in Qinghai Lake. This taxon-specific index is free of terrestrial contamination, sensitive to short-term climatic oscillations, and continuous in recording all climatic events in the lake. The validity of this index and its applicability to other lakes is demonstrated by its good correlations with multiple climate records of Qinghai Lake and another lake on the Tibetan Plateau, Kusai Lake.

  14. Light dependence of selenium uptake by phytoplankton and implications for predicting selenium incorporation into food webs

    USGS Publications Warehouse

    Baines, S.B.; Fisher, N.S.; Doblin, M.A.; Cutter, G.A.; Cutter, L.S.; Cole, B.

    2004-01-01

    The potentially toxic element selenium is first concentrated from solution to a large but highly variable degree by algae and bacteria before being passed on to consumers. The large loads of abiotic and detrital suspended particles often present in rivers and estuaries may obscure spatial and temporal patterns in Se concentrations at the base of the food web. We used radiotracers to estimate uptake of both selenite (Se(IV)) and C by intact plankton communities at two sites in the Sacramento/San Joaquin River Delta. Our goals were to determine (1) whether C and Se(IV) uptake were coupled, (2) the role of bacteria in Se(IV) uptake, and (3) the Se:C uptake ratio of newly produced organic material. Se(IV) uptake, like C uptake, was strongly related to irradiance. The shapes of both relationships were very similar except that at least 42-56% of Se(IV) uptake occurred in the dark, whereas C uptake in the dark was negligible. Of this dark Se(IV) uptake, 34-67% occurred in the 0.2-1.0-??m size fraction, indicating significant uptake by bacteria. In addition to dark uptake, total Se(IV) uptake consisted of a light-driven component that was in fixed proportion to C uptake. Our estimates of daily areal Se(IV):C uptake ratios agreed very well with particulate Se:C measured at a site dominated by phytoplankton biomass. Estimates of bacterial Se:C were 2.4-13 times higher than for the phytoplankton, suggesting that bacteriovores may be exposed to higher dietary Se concentrations than herbivores.

  15. Ice cover extent drives phytoplankton and bacterial community structure in a large north-temperate lake: implications for a warming climate.

    PubMed

    Beall, B F N; Twiss, M R; Smith, D E; Oyserman, B O; Rozmarynowycz, M J; Binding, C E; Bourbonniere, R A; Bullerjahn, G S; Palmer, M E; Reavie, E D; Waters, Lcdr M K; Woityra, Lcdr W C; McKay, R M L

    2016-06-01

    Mid-winter limnological surveys of Lake Erie captured extremes in ice extent ranging from expansive ice cover in 2010 and 2011 to nearly ice-free waters in 2012. Consistent with a warming climate, ice cover on the Great Lakes is in decline, thus the ice-free condition encountered may foreshadow the lakes future winter state. Here, we show that pronounced changes in annual ice cover are accompanied by equally important shifts in phytoplankton and bacterial community structure. Expansive ice cover supported phytoplankton blooms of filamentous diatoms. By comparison, ice free conditions promoted the growth of smaller sized cells that attained lower total biomass. We propose that isothermal mixing and elevated turbidity in the absence of ice cover resulted in light limitation of the phytoplankton during winter. Additional insights into microbial community dynamics were gleaned from short 16S rRNA tag (Itag) Illumina sequencing. UniFrac analysis of Itag sequences showed clear separation of microbial communities related to presence or absence of ice cover. Whereas the ecological implications of the changing bacterial community are unclear at this time, it is likely that the observed shift from a phytoplankton community dominated by filamentous diatoms to smaller cells will have far reaching ecosystem effects including food web disruptions. PMID:25712272

  16. FEEDING RATES OF THE MUD SHRIMP UPOGEBIA PUGETTENSIS AND IMPLICATIONS FOR ESTUARINE PHYTOPLANKTON ABUNDANCE

    EPA Science Inventory

    The burrowing shrimp Upogebia pugettensis is an abundant inhabitant of Pacific Northwest bays and estuaries where it lives commensally with the clam Cryptomya californica. Suspension-feeding activities of the shrimp and its commensal clam, as well as particle settlement within t...

  17. Does the 14C method estimate net photosynthesis? II. Implications from cyclostat studies of marine phytoplankton

    NASA Astrophysics Data System (ADS)

    Pei, Shaofeng; Laws, Edward A.

    2014-09-01

    Two species of marine phytoplankton, Isochrysis galbana and Chlorella kessleri, were grown in a continuous culture system on a 12-h:12-h light:dark cycle of illumination under nitrate-limited growth conditions. At growth rates of ~1 d-1, production rates estimated from 14C uptake were not significantly different from production rates estimated from changes in particulate organic carbon (POC) and total organic carbon (TOC). At growth rates of ~0.35 d-1, however, production rates based on uptake of 14C significantly (p<0.05) overestimated production rates based on changes in POC and TOC in all cases for C. kessleri and after 24 h for I. galbana. The ratio of production based on 14C uptake to production based on changes in POC and TOC concentrations was in all cases higher after 24 h than after 12 h. The extent of overestimation after a 24-h incubation at ~0.35 d-1 was about 23 and 40% in the cases of I. galbana and C. kessleri, respectively. Dark respiration rates estimated from changes in 14C activity during the dark period were lower than the rates estimated from changes of POC and TOC concentrations during the 12 h of darkness because only about 73% of the carbon respired during the dark period had been fixed during the previous 12-h photoperiod. The fact that the 14C method tends to overestimate net carbon assimilation by a greater percentage at low growth rates than at high growth rates probably reflects the greater efficiency of intracellular recycling of respired CO2 at high growth rates. The fact that the extent of overestimation is greater when cells are grown on a light:dark cycle probably reflects the fact that not all carbon respired in the dark was fixed during the previous photoperiod and that intracellular recycling of respired CO2 during the photoperiod is inefficient during some phases of the synchronized growth that tends to be entrained by light:dark cycles.

  18. High Sequence Variability, Diverse Subcellular Localizations, and Ecological Implications of Alkaline Phosphatase in Dinoflagellates and Other Eukaryotic Phytoplankton

    PubMed Central

    Lin, Xin; Zhang, Huan; Cui, Yudong; Lin, Senjie

    2012-01-01

    Alkaline phosphatase (AP) is a key enzyme for phytoplankton to utilize dissolved organic phosphorus (DOP) when dissolved inorganic phosphorus is limited. While three major types of AP and their correspondingly diverse subcellular localization have been recognized in bacteria, little is known about AP in eukaryotic phytoplankton such as dinoflagellates. Here, we isolated a full-length AP cDNA from a latest-diverging dinoflagellate genus Alexandrium, and conducted comparative analyses with homologs from a relatively basal (Amphidinium carterae) and late-diverging (Karenia brevis) lineage of dinoflagellates as well as other eukaryotic algae. New data and previous studies indicate that AP is common in dinoflagellates and most other major eukaryotic groups of phytoplankton. AP sequences are more variable than many other genes studied in dinoflagellates, and are divergent among different eukaryotic phytoplankton lineages. Sequence comparison to the other characterized APs suggests that dinoflagellates and some other eukaryotic phytoplankton possess the putative AP as phoA type, but some other eukaryotic phytoplankton seem to have other types. Phylogenetic analyses based on AP amino acid sequences indicated that the “red-type” eukaryotic lineages formed a monophyletic group, suggesting a common origin of their APs. As different amino acid sequences have been found to predictably determine different spatial distribution in the cells, which may facilitate access to different pools of DOP, existing computational models were adopted to predict the subcellular localizations of putative AP in the three dinoflagellates and other eukaryotic phytoplankton. Results showed different subcellular localizations of APs in different dinoflagellates and other lineages. The linkage between AP sequence divergence, subcellular localization, and ecological niche differentiation requires rigorous experimental verification, and this study now provides a framework for such a future effort

  19. Does the 14C method estimate net photosynthesis? Implications from batch and continuous culture studies of marine phytoplankton

    NASA Astrophysics Data System (ADS)

    Pei, Shaofeng; Laws, Edward A.

    2013-12-01

    We carried out batch culture studies with seven species of marine phytoplankton and chemostat studies with two of the seven species to determine whether and to what extent 14C uptake approximated net photosynthesis. In two of seven cases, Isochrysis galbana and Dunaliella tertiolecta, cells uniformly labeled with 14C lost no activity when they were transferred to a 14C-free medium and allowed to grow in the light. In similar experiments with four other species, uniformly labeled cells lost activity when incubated in the light, but the loss rates were only a few percent per day. Thus these six species appear to respire primarily recently fixed carbon. In the case of the remaining species, Chlorella kessleri, loss rates of 14C in the light from uniformly labeled cells were about 29% per day, the apparent ratio of respiration to net photosynthesis being 0.4. Follow-up chemostat studies with I. galbana and C. kessleri grown under both light- and nitrate-limited conditions produced results consistent with the implications of the batch culture work: uptake of 14C by I. galbana after incubations of 24 h yielded estimates of photosynthetic carbon fixation equal to the product of the chemostat dilution rate and the concentration of organic carbon in the growth chamber. Similar experiments with C. kessleri produced 14C-based estimates of photosynthetic carbon fixation that exceeded the net rates of organic carbon production in the growth chamber by roughly 55%. Time-course studies with both species indicated that at high growth rates recently fixed carbon began to enter the respiratory substrate pool after a time lag of several hours, a result consistent with previous work with D. tertiolecta. The lag time appeared to be much shorter at low growth rates. The results with C. kessleri are similar to results previously reported for Chlorella pyrenoidosa and Amphidium carteri. Collectively these results suggest that 14C uptake by species with relatively high ratios of

  20. Relationships Between Concentrations of Phytoplankton Chlorophyll a and Total Nitrogen in Estuaries: Implications for Development of Nutrient Criteria

    EPA Science Inventory

    Regression relationships between summer surface concentrations of phytoplankton chlorophyll a and total (inorganic + organic) nitrogen have been developed for four estuarine embayments and six riverine estuaries on the U.S. Atlantic and Gulf of Mexico coasts. All systems show spa...

  1. Metal uptake by phytoplankton during a bloom in South San Francisco Bay: Implications for metal cycling in estuaries

    USGS Publications Warehouse

    Luoma, S.N.; VanGeen, A.; Lee, B.-G.; Cloern, J.E.

    1998-01-01

    The 1994 spring phytoplankton bloom in South San Francisco Bay caused substantial reductions in concentrations of dissolved Cd, Ni, and Zn, but not Cu. We estimate that the equivalent of ~60% of the total annual input of Cd, Ni, and Zn from local waste-water treatment plants is cycled through the phytoplankton in South Bay. The results suggest that processes that affect phytoplankton bloom frequency or intensity in estuaries (e.g. nutrient enrichment) may also affect metal trapping. The bloom was characterized by hydrographic surveys conducted at weekly intervals for 9 weeks. Metal samples were collected from the water column on three occasions, timed to bracket the period when the bloom was predicted. Factors that might confound observations of biological influences, such as freshwater inputs, were relatively constant during the study. Before the bloom, concentrations of dissolved Cd were 0.81 ?? 0.02 nmol kg-1, Zn concentrations were 19.8 ?? 1.5 nmol kg-1, Ni were 42 ?? 1.4 nmol kg-1, and Cu were 37 ?? 1.4 nmol kg-1. The values are elevated relative to riverine and coastal end-members, reflecting inputs from wastewater and(or) sediments. At the height of the bloom, dissolved Zn, Cd, and Ni were reduced to 19, 50, and 75% of their prebloom concentrations, respectively. Dissolved Cu concentrations increased 20%. The mass of Cd taken up by phytoplankton was similar to the mass of Cd removed from solution if particle settling was considered, and Cd concentrations estimated in phytoplankton were higher than concentrations in suspended particulate material (SPM). Particulate concentrations of Zn and Ni during the bloom appeared to be dominated by the influence of changes in resuspension of Zn- and Ni-rich sediments.

  2. The Turbulent Life of Phytoplankton

    NASA Technical Reports Server (NTRS)

    Ghosal, S.; Rogers, M.; Wray, A.

    2000-01-01

    Phytoplankton is a generic name for photosynthesizing microscopic organisms that inhabit the upper sunlit layer (euphotic zone) of almost all oceans and bodies of freshwater. They are agents for "primary production," the incorporation of carbon from the environment into living organisms, a process that, sustains the aquatic food web. It is estimated that phytoplankton contribute about half of the global primary production, the other half being due to terrestrial plants. By sustaining the aquatic food web and controlling the biogeochemical cycles through primary production, phytoplankton exert a dominant influence on life on earth. Turbulence influences this process in three very important ways. First, essential mineral nutrients are transported from the deeper layers to the euphotic zone through turbulence. Second, turbulence helps to suspend phytoplankton in the euphotic zone since in still water, the phytoplankton, especially the larger species, tend to settle out of the sunlit layers. Third, turbulence transports phytoplankton from the surface to the dark sterile waters, and this is an important mechanism of loss. Thus, stable phytoplankton populations are maintained through a delicate dynamic balance between the processes of turbulence, reproduction, and sinking. The first quantitative model for this was introduced by Riley, Stommel and Bumpus in 1949. This is an attempt to extend their efforts through a combination of analysis and computer simulation in order to better understand the principal qualitative aspects of the physical/biological coupling of this natural system.

  3. The effects of prolonged darkness on temperate and tropical marine phytoplankton, and their implications for ballast water risk management.

    PubMed

    Carney, K J; Delany, J E; Sawant, S; Mesbahi, E

    2011-06-01

    Phytoplankton assemblages from tropical (Goa) and temperate (UK) locations were exposed to a 28 day dark period, followed by a period of re-exposure to light. During this time phytoplankton survival and changes in nutrient concentrations were mapped. The tropical plankton water samples showed high nutrient levels after the dark period which were utilised by cells during the re-exposure period. UK experiments looked at the effect of three different water types on population recovery after the 28 day dark period, and differences due to seasonal effects. The population growth observed during the re-exposure period in the tropical population was comparable to that of the temperate population. Water type affected recovery and of the three tested media fresh seawater promoted the highest levels of growth. Seasonality had a significant influence on species survival. Understanding the effects of all these factors can aid the development of effective risk assessments in ballast water management. PMID:21489565

  4. Distributions of particulate Heme b in the Atlantic and Southern Oceans—Implications for electron transport in phytoplankton

    NASA Astrophysics Data System (ADS)

    Gledhill, Martha; Achterberg, Eric P.; Honey, David J.; Nielsdottir, Maria C.; Rijkenberg, Micha J. A.

    2013-12-01

    Concentrations of heme b, the iron-containing component of b-type hemoproteins, ranged from < 0.4 to 5.3 pM with an average of 1.18 ± 0.8 pM (± 1σ; n = 86) in the Iceland Basin (IB), from < 0.4 to 19.1 pM with an average of 2.24 ± 1.67 pM (n = 269) in the tropical northeast Atlantic (TNA) and from 0.6 to 21 pM with an average of 5.1 ± 4.8 pM (n = 34) in the Scotia Sea (SS). Heme b concentrations were enhanced in the photic zone and decreased with depth. Heme b concentrations correlated positively with chlorophyll a (chl a) in the TNA (r = 0.41, p < 0.01, n = 269). Heme b did not correlate with chl a in the IB or SS. In the IB and SS, stations with high-chlorophyll and low-nutrient (Fe and/or Si) concentrations exhibited low heme b concentrations relative to particulate organic carbon (< 0.1 μmol mol-1), and high chl a:heme b ratios (> 500). High chl a:heme b ratios resulted from relative decreases in heme b, suggesting proteins such as cytochrome b6f, the core complex of photosystem II, and eukaryotic nitrate reductase were depleted relative to proteins containing chlorophyll such as the eukaryotic light-harvesting antenna. Relative variations in heme b, particulate organic carbon, and chl a can thus be indicative of a physiological response of the phytoplankton community to the prevailing growth conditions, within the context of large-scale changes in phytoplankton community composition.

  5. Shelf and open-ocean calcareous phytoplankton assemblages across the Paleocene-Eocene thermal maximum: Implications for global productivity gradients

    USGS Publications Warehouse

    Gibbs, S.J.; Bralower, T.J.; Bown, P.R.; Zachos, J.C.; Bybell, L.M.

    2006-01-01

    Abrupt global warming and profound perturbation of the carbon cycle during the Paleocene-Eocene Thermal Maximum (PETM, ca. 55 Ma) have been linked to a massive release of carbon into the ocean-atmosphere system. Increased phytoplankton productivity has been invoked to cause subsequent CO2 drawdown, cooling, and environmental recovery. However, interpretations of geochemical and biotic data differ on when and where this increased productivity occurred. Here we present high-resolution nannofossil assemblage data from a shelf section (the U.S. Geological Survey [USGS] drill hole at Wilson Lake, New Jersey) and an open-ocean location (Ocean Drilling Program [ODP] Site 1209, paleoequatorial Pacific). These data combined with published biotic records indicate a transient steepening of shelf-offshelf trophic gradients across the PETM onset and peak, with a decrease in open-ocean productivity coeval with increased nutrient availability in shelf areas. Productivity levels recovered in the open ocean during the later stages of the event, which, coupled with intensified continental weathering rates, may have played an important role in carbon sequestration and CO2 drawdown. ?? 2006 Geological Society of America.

  6. Early Jurassic schizosphaerellid crisis in Cantabria, Spain: Implications for calcification rates and phytoplankton evolution across the Toarcian oceanic anoxic event

    NASA Astrophysics Data System (ADS)

    Tremolada, Fabrizio; van de Schootbrugge, Bas; Erba, Elisabetta

    2005-06-01

    The Toarcian oceanic anoxic event (˜183 Myr ago) represents a global perturbation marked by increasing organic carbon burial and a general decrease in calcium carbonate production likely triggered by elevated carbon dioxide levels in the atmosphere. Here we present quantitative analyses of calcareous nannofossil diversity and abundance from the Castillo de Pedroso section in Cantabria, northern Spain. We compare these data with geochemical data (C and O isotopes) obtained from biogenic and bulk carbonate records in order to highlight the response of calcareous phytoplankton to major climatic and paleoceanographic changes. The Pliensbachian/Toarcian boundary is characterized by an abrupt decrease in abundance of Schizosphaerella punctulata, the most important lithogenic contributor to (hemi) pelagic carbonates in the Early Jurassic. The early Toarcian nannofloral assemblages show an increase in abundance of Mitrolithus jansae and small-sized r-selected taxa and a progressive decrease in S. punctulata percentages. The deep dwellers M. jansae and S. punctulata experienced a major crisis slightly prior to the deposition of the Toarcian black shales that are characterized by high abundances of eutrophic taxa such as Lotharingius spp. and Biscutum spp. The return of S. punctulata associated with lower percentages of eutrophic taxa was observed just above the Toarcian black shales. The Toarcian episode reveals that high CO2 levels and increasing primary productivity probably triggered a shift in abundance from highly calcified nannoliths such as S. punctulata and M. jansae to small-sized r-selected coccoliths that overall record a biocalcification crisis at the onset and during the Toarcian episode.

  7. Contrasting patterns of free-living bacterioplankton diversity in macrophyte-dominated versus phytoplankton blooming regimes in Dianchi Lake, a shallow lake in China

    NASA Astrophysics Data System (ADS)

    Wang, Yujing; Li, Huabing; Xing, Peng; Wu, Qinglong

    2016-04-01

    Freshwater shallow lakes typically exhibit two alternative stable states under certain nutrient loadings: macrophyte-dominated and phytoplankton-dominated water regimes. An ecosystem regime shift from macrophytes to phytoplankton blooming typically reduces the number of species of invertebrates and fishes and results in the homogenization of communities in freshwater lakes. We investigated how microbial biodiversity has responded to a shift of the ecosystem regime in Dianchi Lake, which was previously fully covered with submerged macrophytes but currently harbors both ecological states. We observed marked divergence in the diversity and community composition of bacterioplankton between the two regimes. Although species richness, estimated as the number of operational taxonomic units and phylogenetic diversity (PD), was higher in the phytoplankton dominated ecosystem after this shift, the dissimilarity of bacterioplankton community across space decreased. This decrease in beta diversity was accompanied by loss of planktonic bacteria unique to the macrophyte-dominated ecosystem. Mantel tests between bacterioplankton community distances and Euclidian distance of environmental parameters indicated that this reduced bacterial community diff erentiation primarily reflected the loss of environmental niches, particularly in the macrophyte regime. The loss of this small-scale heterogeneity in bacterial communities should be considered when assessing long-term biodiversity changes in response to ecosystem regime conversions in freshwater lakes.

  8. Measuring Phytoplankton From Satellites

    NASA Technical Reports Server (NTRS)

    Davis, C. O.

    1989-01-01

    Present and future methods examined. Report reviews methods of calculating concentration of phytoplankton from satellite measurements of color of ocean and using such calculations to estimate productivity of phytoplankton.

  9. High-resolution analysis of a North Sea phytoplankton community structure based on in situ flow cytometry observations and potential implication for remote sensing

    NASA Astrophysics Data System (ADS)

    Thyssen, M.; Alvain, S.; Lefèbvre, A.; Dessailly, D.; Rijkeboer, M.; Guiselin, N.; Creach, V.; Artigas, L.-F.

    2015-07-01

    Phytoplankton observation in the ocean can be a challenge in oceanography. Accurate estimations of its biomass and dynamics will help to understand ocean ecosystems and refine global climate models. Relevant data sets of phytoplankton defined at a functional level and on a sub-meso- and daily scale are thus required. In order to achieve this, an automated, high-frequency, dedicated scanning flow cytometer (SFC, Cytobuoy b.v., the Netherlands) has been developed to cover the entire size range of phytoplankton cells whilst simultaneously taking pictures of the largest of them. This cytometer was directly connected to the water inlet of a PocketFerryBox during a cruise in the North Sea, 08-12 May 2011 (DYMAPHY project, INTERREG IV A "2 Seas"), in order to identify the phytoplankton community structure of near surface waters (6 m) with a high spatial resolution basis (2.2 ± 1.8 km). Ten groups of cells, distinguished on the basis of their optical pulse shapes, were described (abundance, size estimate, red fluorescence per unit volume). Abundances varied depending on the hydrological status of the traversed waters, reflecting different stages of the North Sea blooming period. Comparisons between several techniques analysing chlorophyll a and the scanning flow cytometer, using the integrated red fluorescence emitted by each counted cell, showed significant correlations. For the first time, the community structure observed from the automated flow cytometry data set was compared with PHYSAT reflectance anomalies over a daily scale. The number of matchups observed between the SFC automated high-frequency in situ sampling and remote sensing was found to be more than 2 times better than when using traditional water sampling strategies. Significant differences in the phytoplankton community structure within the 2 days for which matchups were available suggest that it is possible to label PHYSAT anomalies using automated flow cytometry to resolve not only dominant groups but

  10. Spatial partitioning between species of the phytoplankton-feeding guild on an estuarine intertidal sand flat and its implication on habitat carrying capacity

    NASA Astrophysics Data System (ADS)

    Tamaki, Akio; Nakaoka, Ayumi; Maekawa, Hideki; Yamada, Fumihiko

    2008-07-01

    The fishery yield of Manila clams, Ruditapes philippinarum, increased considerably in the 1970s but has decreased rapidly since the middle 1980s on extensive intertidal sand flats in Ariake Sound (Kyushu, Japan). A survey conducted in 2004 on a 3.4-km 2 sand flat located in the central part of the Sound (Shirakawa sand flat) revealed four dominant species: two thalassinidean shrimps ( Upogebia major and Nihonotrypaea japonica), which are deep-reaching burrow dwellers with strong bioturbation activities, and two bivalves ( Mactra veneriformis and R. philippinarum). All four species belong to a phytoplankton (diatom)-feeding guild. In the late 1970s, the Manila clam population prevailed in high densities over the entire sand flat, whereas its distribution was restricted to the lowest quarter of the shore in 2004. In contrast, the population sizes and zones of occurrence of the other phytoplankton feeders have expanded in the absence of R. philippinarum, perhaps an indication of competitive release. After establishment, effects of the thalassinidean shrimps on sediment stability appear to have further reduced clam abundances. Across the sand flat in 2004, wet weight population biomass estimates for N. japonica, U. major, M. veneriformis, and R. philippinarum (whole body for shrimps and soft tissue for bivalves) were 304, 111, 378, and 234 tonnes, respectively. Based on Manila clam fishery yield records from Shirakawa, the carrying capacity of the Shirakawa sand flat in the late 1970s was estimated to be two times greater than the sum value for the whole phytoplankton-feeding guild in 2004. It is hypothesized that (1) the amount of phytoplankton determines the carrying capacity for the benthic community on the Shirakawa sand flat, with both phytoplankton and benthic biomass at maxima in the late 1970s, and (2) the subsequent increases in competition for space have caused further declines in the Manila clam population biomass to approximately one-eighth of its past

  11. Sea Soup: Phytoplankton.

    ERIC Educational Resources Information Center

    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…

  12. Phytoplankton and Climate

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  14. Resilience Processes Demonstrated by Young Gay and Bisexual Men Living with HIV: Implications for Intervention

    PubMed Central

    Bruce, Douglas; Hosek, Sybil G.; Fernandez, M. Isabel; Rood, Brian A.

    2014-01-01

    Abstract Given the increasing numbers of young gay/bisexual men (YGBM) diagnosed with HIV, it is important to understand the resilience processes enacted by this population in order to develop interventions that support their healthy development. Qualitative interviews were conducted with 54 YGBM (ages 17 to 24; 57% African American, 22% Latino) living with HIV from four geographically diverse clinics in the United States. Resilience processes clustered into four primary thematic areas: (1) engaging in health-promoting cognitive processes; (2) enacting healthy behavioral practices; (3) enlisting social support from others; and (4) empowering other young gay/bisexual men. These data suggest that YGBM living with HIV demonstrate resilience across multiple dimensions, including intrapersonal-level resilience related to individual cognitions and behaviors, as well as interpersonal-level resilience related to seeking support and providing support to others. Implications for the development of culturally-appropriate and strengths-based secondary prevention and other psychosocial interventions for YGBM living with HIV are discussed. PMID:25329778

  15. Andreas Acrivos Dissertation Prize Lecture: Phytoplankton in Flow

    NASA Astrophysics Data System (ADS)

    Durham, William M.

    2012-11-01

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

  16. Global Ocean Phytoplankton

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

    Phytoplankton are free-floating algae that grow in the euphotic zone of the upper ocean, converting carbon dioxide, sunlight, and available nutrients into organic carbon through photosynthesis. Despite their microscopic size, these photoautotrophs are responsible for roughly half the net primary production on Earth (NPP; gross primary production minus respiration), fixing atmospheric CO2 into food that fuels our global ocean ecosystems. Phytoplankton thus play a critical role in the global carbon cycle, and their growth patterns are highly sensitive to environmental changes such as increased ocean temperatures that stratify the water column and prohibit the transfer of cold, nutrient richwaters to the upper ocean euphotic zone.

  17. Ecotoxicology of bromoacetic acid on estuarine phytoplankton.

    PubMed

    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. PMID:26247379

  18. Global Ocean Phytoplankton

    NASA Technical Reports Server (NTRS)

    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.

  19. Genome sequences of three live attenuated vaccine strains of Brucella species and implications for pathogenesis and differential diagnosis.

    PubMed

    Wang, Yufei; Ke, Yuehua; Wang, Zhoujia; Yuan, Xitong; Qiu, Yefeng; Zhen, Qing; Xu, Jie; Li, Tiefeng; Wang, Dali; Huang, Liuyu; Chen, Zeliang

    2012-11-01

    Live attenuated vaccines play essential roles in the prevention of brucellosis. Here, we report the draft genome sequences of three vaccine strains, Brucella melitensis M5-10, B. suis S2-30, and B. abortus 104M. Primary genome sequence analysis identified mutations, deletions, and insertions which have implications for attenuation and signatures for differential diagnosis. PMID:23045513

  20. Changes in production and respiration during a spring phytoplankton bloom in San Francisco Bay, California, USA: Implications for net ecosystem metabolism

    USGS Publications Warehouse

    Caffrey, J.M.; Cloern, J.E.; Grenz, C.

    1998-01-01

    We present results of an intensive sampling program designed to measure weekly changes in ecosystem respiration (oxygen consumption in the water column and sediments) around the 1996 spring bloom in South San Francisco Bay, California, USA. Measurements were made at a shallow site (2 m, where mean photic depth was 60% of the water column height) and a deep site (15 m, mean photic depth was only 20% of the water column). We also estimated phytoplankton primary production weekly at both sites to develop estimates of net oxygen flux as the sum of pelagic production (PP), pelagic respiration (PR) and benthic respiration (BR). Over the 14 wk period from February 5 to May 14, PP ranged from 2 to 210, PR from 9 to 289, and BR from 0.1 to 48 mmol O2 m-2 d-1, illustrating large variability of estuarine oxygen fluxes at the weekly time scale. Pelagic production exceeded total respiration at the shallow site, but not at the deep site, demonstrating that the shallow domains are net autotrophic but the deep domains are net heterotrophic, even during the period of the spring bloom. If we take into account the potential primary production by benthic microalgae, the estuary as a whole is net autotrophic during spring, net heterotrophic during the nonbloom seasons, and has a balanced net metabolism over a full annual period. The seasonal shift from net autotrophy to heterotrophy during the transition from spring to summer was accompanied by a large shift from dominance by pelagic respiration to dominance by benthic respiration. This suggests that changes in net ecosystem metabolism can reflect changes in the pathways of energy flow in shallow coastal ecosystems.

  1. Phytoplankton Chytridiomycosis: Fungal Parasites of Phytoplankton and Their Imprints on the Food Web Dynamics

    PubMed Central

    Sime-Ngando, Télesphore

    2012-01-01

    Parasitism is one of the earlier and common ecological interactions in the nature, occurring in almost all environments. Microbial parasites typically are characterized by their small size, short generation time, and high rates of reproduction, with simple life cycle occurring generally within a single host. They are diverse and ubiquitous in aquatic ecosystems, comprising viruses, prokaryotes, and eukaryotes. Recently, environmental 18S rDNA surveys of microbial eukaryotes have unveiled major infecting agents in pelagic systems, consisting primarily of the fungal order of Chytridiales (chytrids). Chytrids are considered the earlier branch of the Eumycetes and produce motile, flagellated zoospores, characterized by a small size (2–6 μm), and a single, posterior flagellum. The existence of these dispersal propagules includes chytrids within the so-called group of zoosporic fungi, which are particularly adapted to the plankton lifestyle where they infect a wide variety of hosts, including fishes, eggs, zooplankton, algae, and other aquatic fungi but primarily freshwater phytoplankton. Related ecological implications are huge because chytrids can killed their hosts, release substrates for microbial processes, and provide nutrient-rich particles as zoospores and short fragments of filamentous inedible hosts for the grazer food chain. Furthermore, based on the observation that phytoplankton chytridiomycosis preferentially impacts the larger size species, blooms of such species (e.g., filamentous cyanobacteria) may not totally represent trophic bottlenecks. Besides, chytrid epidemics represent an important driving factor in phytoplankton seasonal successions. In this review, I summarize the knowledge on the diversity, community structure, quantitative importance, and functional roles of fungal chytrids, primarily those who are parasites of phytoplankton, and infer the ecological implications and potentials for the food web dynamics and properties. I reach the

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

    PubMed

    Sime-Ngando, Télesphore

    2012-01-01

    Parasitism is one of the earlier and common ecological interactions in the nature, occurring in almost all environments. Microbial parasites typically are characterized by their small size, short generation time, and high rates of reproduction, with simple life cycle occurring generally within a single host. They are diverse and ubiquitous in aquatic ecosystems, comprising viruses, prokaryotes, and eukaryotes. Recently, environmental 18S rDNA surveys of microbial eukaryotes have unveiled major infecting agents in pelagic systems, consisting primarily of the fungal order of Chytridiales (chytrids). Chytrids are considered the earlier branch of the Eumycetes and produce motile, flagellated zoospores, characterized by a small size (2-6 μm), and a single, posterior flagellum. The existence of these dispersal propagules includes chytrids within the so-called group of zoosporic fungi, which are particularly adapted to the plankton lifestyle where they infect a wide variety of hosts, including fishes, eggs, zooplankton, algae, and other aquatic fungi but primarily freshwater phytoplankton. Related ecological implications are huge because chytrids can killed their hosts, release substrates for microbial processes, and provide nutrient-rich particles as zoospores and short fragments of filamentous inedible hosts for the grazer food chain. Furthermore, based on the observation that phytoplankton chytridiomycosis preferentially impacts the larger size species, blooms of such species (e.g., filamentous cyanobacteria) may not totally represent trophic bottlenecks. Besides, chytrid epidemics represent an important driving factor in phytoplankton seasonal successions. In this review, I summarize the knowledge on the diversity, community structure, quantitative importance, and functional roles of fungal chytrids, primarily those who are parasites of phytoplankton, and infer the ecological implications and potentials for the food web dynamics and properties. I reach the

  3. Phytoplankton and nutrient distributions in a front-eddy area adjacent to the coastal upwelling zone off Concepcion (Chile): implications for ecosystem productivity.

    NASA Astrophysics Data System (ADS)

    Morales, Carmen; Anabalón, Valeria; Hormazábal, Samuel; Cornejo, Marcela; Bento, Joaquim; Silva, Nelson

    2016-04-01

    The impact that sub-mesoscale (1-10 km) to mesocale (50-100 km) oceanographic variability has on plankton and nutrient distributions (horizontal and vertical) in the coastal upwelling and transition zones off Concepcion was the focus of this study. Satellite time-series data (wind, sea-surface temperature (SST), and altimetry) were used to understand the dynamic context of in situ data derived from a short-term front survey (3 d) during the upwelling period (3-6 February, 2014). The survey included two transects perpendicular to the coast, covering the shelf and shelf-break areas just north of Punta Lavapie, a main upwelling center (˜37° S). Wind and SST time-series data indicated that the survey was undertaken just after a moderate upwelling event (end of January) which lead to a relaxation phase during early February. A submesoscale thermal front was detected previous to and during the survey and results from an eddy tracking algorithm based on altimetry data indicated that this front (F1) was flanked on its oceanic side by an anticyclonic, mesoscale eddy (M1), which was ˜25 d old at the sampling time. M1 strengthened the thermal gradient of F1 by bringing warmer oceanic water nearer to the colder coastal upwelling zone. The distributions of hydrographic variables and nutrients in the water column (<300 m depth) also denoted these two features. Phytoplankton biomass (Chl-a) and diatom abundance were highest in the surface layer (<20 m depth) between the coast and F1, with primary maxima in the latter, whereas they were highest at the subsurface (20-40 m depth) towards M1 and associated with secondary maxima. The distribution of dominant diatoms in the top layer (<100 m depth) indicated that both coastal and oceanic species were aggregated at F1 and in M1. These results suggest that the front-eddy interaction creates a complex field of submesoscale processes in the top layer, including vertical nutrient injections and lateral stirring, which contributes to the

  4. Short-term variability of water quality and its implications on phytoplankton production in a tropical estuary (Cochin backwaters-India).

    PubMed

    Madhu, N V; Balachandran, K K; Martin, G D; Jyothibabu, R; Thottathil, Shoji D; Nair, Maheswari; Joseph, T; Kusum, K K

    2010-11-01

    Changes in the phytoplankton biomass (chlorophyll a), production rate, and species composition were studied over two seasons using the time series measurements in the northern limb of the Cochin estuary in relation to the prevailing hydrological conditions. The present study showed the significant seasonal variation in water temperature (F=69.4, P<0.01), salinity (F=341.93, P<0.01), dissolved inorganic phosphorous (F=17.71, P<0.01), and silica (F=898.1, P<0.01) compared to nitrogen (F=1.646, P>0.05). The uneven input of ammonia (3.4-224.8 μM) from upstream (Periyar River) leads to the inconsistency in the N/P ratio (range 6.8-262). A distinct seasonality was observed in Si/N (F=382.9, P<0.01) and Si/P (F=290.3, P<0.01) ratios compared to the N/P ratio (F=1.646, P>0.05). The substantial increase in chlorophyll a (average, 34.8±10 mg m(-3)) and primary production (average, 1,304±694 mg C m(-3) day(-1)) indicated the mesotrophic condition of the study area during the premonsoon (PRM) and it was attributed to the large increase in the population of nanoplankton (size<20 μ) such as Skeletonema costatum, Thalassiosira subtilis, Nitzschia closterium, and Navicula directa. In contrast, during the post monsoon (PM), low chlorophyll a concentration (average, 9.3±9.2 mg m(-3)) and primary production (average, 124±219 mg C m(-3) day(-1)) showed heterotrophic condition. It can be stated that favorable environmental conditions (optimum nutrients and light intensity) prevailing during the PRM have enhanced the abundance of the nanoplankton community in the estuary, whereas during the PM, the light limitation due to high turbidity can reduce the nanoplankton growth and abundance, even though high nutrient level exists. PMID:19936957

  5. Regulation of phytoplankton dynamics by vitamin B12

    NASA Astrophysics Data System (ADS)

    Sañudo-Wilhelmy, S. A.; Gobler, C. J.; Okbamichael, M.; Taylor, G. T.

    2006-02-01

    Despite the biological necessity of vitamin B12 (cobalamin), its importance in phytoplankton ecology has been ignored for nearly three decades. Here we report strong and selective responses of phytoplankton communities to varying low levels (5-87 pM) of dissolved B12 in several coastal embayments. The ecological importance of this vitamin is inferred from observed declines in dissolved B12 levels as field populations of large (>5 μm) phytoplankton increased. In contrast, biomass of small (<5 μm) phytoplankton varied independently of B12 concentrations. These observations were corroborated by field-based nutrient amendment experiments, in which B12 additions stimulated growth of large phytoplankton taxa 6-fold over unamended controls. In contrast, small taxa (<5 μm) were largely unaffected. This study provides the first evidence of vitamin B12's influence on phytoplankton field population dynamics based on direct chemical measurements of cobalamin, and implicates B12 as an important organic regulator of photoautotrophic fertility in marine systems.

  6. Phytoplankton Bloom Off Portugal

    NASA Technical Reports Server (NTRS)

    2002-01-01

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

  7. Securing a Better Living Environment for Left-Behind Children: Implications and Challenges for Policies

    PubMed Central

    Lam, Theodora; Ee, Miriam; Anh, Hoang Lan; Yeoh, Brenda S.A.

    2014-01-01

    Migration is an increasingly significant driver of transformations in family configurations and caregiving practices as well as living arrangements. The sustainability of geographically-split family formations is dependent on several factors, including the presence and strength of care support networks among migrants and their left-behind families, access to communication infrastructure and the stability of the families’ financial resources. Drawing on both a selective review of relevant academic literature as well as key findings from the CHAMPSEA Project, the article first examines the effects of these three factors on the well-being of migrants’ left-behind family members, especially children. The article also considers major implications of the project’s findings, as well as possible challenges for migration and development policies. One area of concern for migration and development policy arising from our research findings is the need to provide better support for left-behind caregivers or carers who are substituting for the absent migrant in childcare and domestic work but who may also need care and support themselves. Another area relates to the need to improve communication infrastructure to help migrants and their families maintain their relationships across transnational spaces; while a third lies with the importance of minimizing migrant families’ economic stress stemming from the cycle of debts resulting from exorbitant broker fees and the mismanagement of remittances. By acknowledging both the social and economic costs of international labor migration on families, governments of labor-sending countries can create a more effective legal and institutional framework as well as design suitable supporting mechanisms for left-behind families. There is then a stronger possibility that migration can become a sustainable development strategy for transnational families in South-East Asia. PMID:24954965

  8. Repeated-Measures Implication of Hepatocellular Carcinoma Biomarkers in Living Donor Liver Transplantation

    PubMed Central

    Chiu, King-Wah; Nakano, Toshiaki; Chen, Kuang-Den; Hsu, Li-Wen; Lai, Chia-Yun; Huang, Ching-Yin; Cheng, Yu-Fan; Goto, Shigeru; Chen, Chao-Long

    2015-01-01

    Objective Hepatocellular carcinoma (HCC) and its recurrence are major problems in living donor liver transplantation (LDLT). Several biomarkers have been used to investigate this event. We conducted a prospective controlled study to determine the activities of the basic fibroblast growth factor (FGF-2), survivin, Ki67, endostatin, and vascular endothelial growth factor (VEGF) in different conditions before, early after, and late after LDLT with and without HCC recurrence. Methods Fifty patients with virus-related HCC who underwent LDLT were enrolled in this 2-year cross-sectional study. During the study period, recurrent HCC was identified in 9 patients (study group, n = 9) and 41 patients (control group, n = 41) had no recurrence after LDLT. The mean time to HCC recurrence was 587.11 ± 398.64 days (range, 90–1352 days). Microvascular invasion (MVI) was found in 66.7% (6/9) of the recipients, as determined on pathological examination. The serum biomarkers were investigated by using enzyme-linked immunosorbent assay at the different LDLT stages. Results The serum levels of the biomarkers significantly correlated with LDLT and HCC recurrence in the repeated-measures analysis (F = 31.676, P = 0.000). Significant differences were observed in the effects of all biomarkers (F = 85.313, P = 0.000) and the time to HCC recurrence after LDLT (F = 3.178, P = 0.046). The biomarkers, ordered by the observed power of the test for HCC recurrence after LDLT, were FGF-2 (1.000) > survivin (0.999) > Ki67 (0.949) > endostatin (0.411) > VEGF (0.305). Conclusions Different biomarker activities may be implicated in the pathogenesis of HCC recurrence after LDLT. Oncogenes may not exist in the new graft but may still be present in the peripheral blood. The timing of HCC recurrence and impact of MVI in the explanted liver requires confirmation in larger studies with a longer follow-up. PMID:25978323

  9. Phytoplankton Succession in Recurrently Fluctuating Environments

    PubMed Central

    Roelke, Daniel L.; Spatharis, Sofie

    2015-01-01

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

  10. Bacterial survival governed by organic carbon release from senescent oceanic phytoplankton

    NASA Astrophysics Data System (ADS)

    Lasternas, S.; Agustí, S.

    2013-10-01

    Bacteria recycle vast amounts of organic carbon, playing key biogeochemical and ecological roles in the ocean. Bacterioplankton dynamics are expected to be dependent on phytoplankton primary production, but there is a high diversity of processes (e.g. sloppy feeding, cell exudation, viral lysis) involved in the transference of primary production to dissolved organic carbon available to bacteria. Here we show cell survival of heterotrophic bacterioplankton in the subtropical Atlantic Ocean to be determined by phytoplankton extracellular carbon release (PER). PER represents the fraction of primary production released as dissolved organic carbon, and changes in the PER variability was explained by phytoplankton cell death, with the communities experiencing the highest phytoplankton cell mortality showing a larger proportion of extracellular carbon release. Both PER and the percent of dead phytoplankton cells increased from eutrophic to oligotrophic waters, while heterotrophic bacteria communities, including 60 to 95% of living cells (%LC), increased from the productive to the most oligotrophic waters. The percentage of living heterotrophic bacterial cells increased with increasing phytoplankton extracellular carbon release, across oligotrophic to productive waters in the NE Atlantic, where lower PER have resulted in a decrease in the flux of phytoplankton DOC per bacterial cell. The results highlight phytoplankton cell death as a process influencing the flow of dissolved photosynthetic carbon in the NE Atlantic Ocean, and demonstrated a close coupling between the fraction of primary production released and heterotrophic bacteria survival.

  11. Phytoplankton's motion in turbulent ocean

    NASA Astrophysics Data System (ADS)

    Fouxon, Itzhak; Leshansky, Alexander

    2015-07-01

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

  12. Phytoplankton's motion in turbulent ocean.

    PubMed

    Fouxon, Itzhak; Leshansky, Alexander

    2015-07-01

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

  13. Identifying Phytoplankton Classes In California Reservoirs Using HPLC Pigment Analysis

    NASA Astrophysics Data System (ADS)

    Siddiqui, S.; Peacock, M. B.; Kudela, R. M.; Negrey, K.

    2014-12-01

    Few bodies of water are routinely monitored for phytoplankton composition due to monetary and time constraints, especially the less accessible bodies of water in central and southern California. These lakes and estuaries are important for economic reasons such as tourism and fishing. This project investigated the composition of phytoplankton present using pigment analysis to identify dominant phytoplankton groups. A total of 28 different sites with a wide range of salinity (0 - 60) in central and southern California were examined. These included 13 different bodies of water in central California: 6 in the Sierras, 7 in the San Francisco Bay Estuary, and 15 from southern California. The samples were analyzed using high-performance liquid-chromatography (HPLC) to quantify the pigments present (using retention time and the spectral thumbprint). Diagnostic pigments were used to indicate the phytoplankton class composition, focusing on diatoms, dinoflagellates, cryptophytes, and cyanobacteria - all key phytoplankton groups indicative of the health of the sampled reservoir. Our results indicated that cyanobacteria dominated four of the seven bodies of central California water (Mono Lake, Bridgeport Reservoir, Steamboat Slough, and Pinto Lake); cryptophytes and nannoflagellates dominated two of the central California bodies of water (Mare Island Strait and Topaz Lake); and diatoms and dinoflagellates dominated one central California body of water, Oakland Inner Harbor, comprising more than 70% of the phytoplankton present. We expect the bodies of water from Southern California to be as disparate. Though this data is only a snapshot, it has significant implications in comparing different ecosystems across California, and it has the potential to provide valuable insight into the composition of phytoplankton communities.

  14. Why marine phytoplankton calcify.

    PubMed

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

    2016-07-01

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

  15. The Lived Experiences of African American Women with Breast Cancer: Implications for Counselors

    ERIC Educational Resources Information Center

    Clay, LaTasha K.

    2013-01-01

    Qualitative phenomenological methodology was used to explore the lived experiences of African American women diagnosed with breast cancer. Phenomenology focuses on the meaning of the lived experiences of individuals experiencing a concept, structure, or phenomenon (Creswell, 2007). The purpose of phenomenological research is to identify phenomena…

  16. Margalef's mandala and phytoplankton bloom strategies

    NASA Astrophysics Data System (ADS)

    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.

  17. Exceptionally Long-Lived Charge Separated State in Zeolitic Imidazolate Framework: Implication for Photocatalytic Applications.

    PubMed

    Pattengale, Brian; Yang, Sizhuo; Ludwig, John; Huang, Zhuangqun; Zhang, Xiaoyi; Huang, Jier

    2016-07-01

    Zeolitic imidazolate frameworks (ZIFs) have emerged as a novel class of porous metal-organic frameworks (MOFs) for catalysis application because of their exceptional thermal and chemical stability. Inspired by the broad absorption of ZIF-67 in UV-vis-near IR region, we explored its excited state and charge separation dynamics, properties essential for photocatalytic applications, using optical (OTA) and X-ray transient absorption (XTA) spectroscopy. OTA results show that an exceptionally long-lived excited state is formed after photoexcitation. This long-lived excited state was confirmed to be the charge-separated (CS) state with ligand-to-metal charge-transfer character using XTA. The surprisingly long-lived CS state, together with its intrinsic hybrid nature, all point to its potential application in heterogeneous photocatalysis and energy conversion. PMID:27322216

  18. Disassembling Iron Availability to Phytoplankton

    PubMed Central

    Shaked, Yeala; Lis, Hagar

    2012-01-01

    The bioavailability of iron to microorganisms and its underlying mechanisms have far reaching repercussions to many natural systems and diverse fields of research, including ocean biogeochemistry, carbon cycling and climate, harmful algal blooms, soil and plant research, bioremediation, pathogenesis, and medicine. Within the framework of ocean sciences, short supply and restricted bioavailability of Fe to phytoplankton is thought to limit primary production and curtail atmospheric CO2 drawdown in vast ocean regions. Yet a clear-cut definition of bioavailability remains elusive, with elements of iron speciation and kinetics, phytoplankton physiology, light, temperature, and microbial interactions, to name a few, all intricately intertwined into this concept. Here, in a synthesis of published and new data, we attempt to disassemble the complex concept of iron bioavailability to phytoplankton by individually exploring some of its facets. We distinguish between the fundamentals of bioavailability – the acquisition of Fe-substrate by phytoplankton – and added levels of complexity involving interactions among organisms, iron, and ecosystem processes. We first examine how phytoplankton acquire free and organically bound iron, drawing attention to the pervasiveness of the reductive uptake pathway in both prokaryotic and eukaryotic autotrophs. Turning to acquisition rates, we propose to view the availability of various Fe-substrates to phytoplankton as a spectrum rather than an absolute “all or nothing.” We then demonstrate the use of uptake rate constants to make comparisons across different studies, organisms, Fe-compounds, and environments, and for gaging the contribution of various Fe-substrates to phytoplankton growth in situ. Last, we describe the influence of aquatic microorganisms on iron chemistry and fate by way of organic complexation and bio-mediated redox transformations and examine the bioavailability of these bio-modified Fe species. PMID:22529839

  19. English in the Primary Classroom in Vietnam: Students' Lived Experiences and Their Social and Policy Implications

    ERIC Educational Resources Information Center

    Nguyen, Lan Chi; Hamid, M. Obaidul; Renshaw, Peter

    2016-01-01

    Although the teaching of English as a foreign language in primary schools has emerged as one of the major language-in-education policy decisions, students' perspectives on primary English have received very little research attention. Drawing on data from a larger study, this paper depicts primary school students' lived experiences in the English…

  20. An Expressed Preference Determination of College Students' Valuation of Statistical Lives: Methods and Implications

    ERIC Educational Resources Information Center

    Brady, Kevin L.

    2008-01-01

    Government agencies typically apply a general value of statistical life (VSL) estimate when performing cost-benefit analysis (CBA). However, theory suggests that college students attach a value to statistical lives that differs from society's VSL; therefore, CBA may lead to inefficient levels of risk reduction among students. A contingent…

  1. The Lived Experiences of Orphaned Learners in South Africa: Implications for the Provision of Quality Education

    ERIC Educational Resources Information Center

    Motha, Kholofelo Charlotte; Frempong, George

    2014-01-01

    Learners living in impoverished communities and subjected to the kind of disadvantage in operation in their home environment are at risk of receiving education of an inferior quality. The situation is worse for orphans, especially those residing in poor communities in that they bring to school peculiar attributes which poses challenges for the…

  2. Implications for Education of Recent Trends in Live Births and International and Interprovincial Migration of Children.

    ERIC Educational Resources Information Center

    Jackson, R. W. B.

    The two factors of live births and migration constitute the major determinants of the size and composition of the population for the provinces as well as for Canada as a whole. The decline in fertility has almost exactly offset the increase in the number of young women in the child-bearing age groups. The effective length of the reproductive…

  3. Musical Meaning in the Lives of Those Affected by the Holocaust: Implications for Music Education

    ERIC Educational Resources Information Center

    Cunningham, Deborah A.

    2014-01-01

    This qualitative study investigated the role of music in the lives of those affected by the Holocaust. Participants were identified through purposeful and snowball sampling techniques, and a total of five were selected based on their connection to the Holocaust. Participants included those incarcerated in camps and ghettos, those who escaped…

  4. Predator-Induced Fleeing Behaviors in Phytoplankton: A New Mechanism for Harmful Algal Bloom Formation?

    PubMed Central

    Harvey, Elizabeth L.; Menden-Deuer, Susanne

    2012-01-01

    In the plankton, heterotrophic microbes encounter and ingest phytoplankton prey, which effectively removes >50% of daily phytoplankton production in the ocean and influences global primary production and biochemical cycling rates. Factors such as size, shape, nutritional value, and presence of chemical deterrents are known to affect predation pressure. Effects of movement behaviors of either predator or prey on predation pressure, and particularly fleeing behaviors in phytoplankton are thus far unknown. Here, we quantified individual 3D movements, population distributions, and survival rates of the toxic phytoplankton species, Heterosigma akashiwo in response to a ciliate predator and predator-derived cues. We observed predator-induced defense behaviors previously unknown for phytoplankton. Modulation of individual phytoplankton movements during and after predator exposure resulted in an effective separation of predator and prey species. The strongest avoidance behaviors were observed when H. akashiwo co-occurred with an actively grazing predator. Predator-induced changes in phytoplankton movements resulted in a reduction in encounter rate and a 3-fold increase in net algal population growth rate. A spatially explicit population model predicted rapid phytoplankton bloom formation only when fleeing behaviors were incorporated. These model predictions reflected field observations of rapid H. akashiwo harmful algal bloom (HAB) formation in the coastal ocean. Our results document a novel behavior in phytoplankton that can significantly reduce predation pressure and suggests a new mechanism for HAB formation. Phytoplankton behaviors that minimize predatory losses, maximize resource acquisition, and alter community composition and distribution patterns could have major implications for our understanding and predictive capacity of marine primary production and biochemical cycling rates. PMID:23029518

  5. What is causing the phytoplankton increase in San Francisco Bay?

    USGS Publications Warehouse

    Cloern, J.E.; Jassby, A.D.; Schraga, T.S.; Dallas, K.L.

    2006-01-01

    The largest living component of San Francisco Bay is the phytoplankton, a suspension of microscopic cells that convert sunlight energy into new living biomass through the same process of photosynthesis used by land plants. This primary production is the ultimate source of food for clams, zooplankton, crabs, sardines, halibut, sturgeon, diving ducks, pelicans, and harbor seals. From measurements made in 1980, we estimated that phytoplankton primary production in San Francisco Bay was about 200,000 tons of organic carbon per year (Jassby et al. 1993). This is equivalent to producing the biomass of 5500 adult humpback whales, or the calories to feed 1.8 million people. These numbers may seem large, but primary production in San Francisco Bay is low compared to many other nutrient-enriched estuaries.

  6. Health Implications of Adults' Eating at and Living near Fast Food or Quick Service Restaurants

    PubMed Central

    Jiao, J; Moudon, A V; Kim, S Y; Hurvitz, P M; Drewnowski, A

    2015-01-01

    Background: This paper examined whether the reported health impacts of frequent eating at a fast food or quick service restaurant on health were related to having such a restaurant near home. Methods: Logistic regressions estimated associations between frequent fast food or quick service restaurant use and health status, being overweight or obese, having a cardiovascular disease or diabetes, as binary health outcomes. In all, 2001 participants in the 2008–2009 Seattle Obesity Study survey were included in the analyses. Results: Results showed eating ⩾2 times a week at a fast food or quick service restaurant was associated with perceived poor health status, overweight and obese. However, living close to such restaurants was not related to negative health outcomes. Conclusions: Frequent eating at a fast food or quick service restaurant was associated with perceived poor health status and higher body mass index, but living close to such facilities was not. PMID:26192449

  7. Techniques for Quantifying Phytoplankton Biodiversity

    NASA Astrophysics Data System (ADS)

    Johnson, Zackary I.; Martiny, Adam C.

    2015-01-01

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

  8. Comparative genomics of the Mycobacterium signaling architecture and implications for a novel live attenuated Tuberculosis vaccine.

    PubMed

    Zhou, Peifu; Xie, Jianping

    2014-01-01

    Tuberculosis (TB), caused by Mycobacterium tuberculosis (M.tb), remains a major threat to global public health. A new TB vaccine affording superior immune protection to M. bovis Bacillus Calmette-Guérin (BCG) is imperative. The advantage of a live attenuated vaccine is that it can mimic the bona fide pathogen, elicit immune responses similar to natural infection, and potentially provide more protection than other vaccines. BCG, the only vaccine and a live attenuated vaccine that is the result of cumulative mutations by serial passage of M. bovis, has provided clues for the construction of novel improved vaccines. A strategy is put forward for identifying a new live attenuated TB vaccine generated by cumulative mutation based on M.tb. Given the important role of the M.tb signaling network consisting of a two-component system, eukaryotic-like Ser/Thr protein kinase system and sigma factor system based on comparisons among M.tb H37Rv, M. bovis, and BCG, we have put a premium on this signaling circuit as the starting point for the generation of an attenuated TB vaccine. PMID:24013364

  9. Incarceration of people living with HIV/AIDS: Implications for Treatment-As-Prevention

    PubMed Central

    Milloy, M-J; Montaner, Julio S.G.; Wood, Evan

    2015-01-01

    Contact with the criminal justice system, including incarceration, is a common experience for many people living with HIV/AIDS. Optimism has recently been expressed that correctional facilities could be important locations for Treatment-as-Prevention (TasP)-based initiatives. We review recent findings regarding the effect of incarceration on patterns of HIV transmission, testing, treatment initiation and retention. We found that the prevalence of HIV infection among incarcerated individuals remains higher than analogous non-incarcerated populations. Recent studies have shown that voluntary HIV/AIDS testing is feasible in many correctional facilities, although the number of previously undiagnosed individuals identified has been modest. Studies have implied enhanced linkage to HIV/AIDS treatment and care in jails in the United States was associated with improvements in the HIV cascade of care. However, for many individuals living with HIV/AIDS, exposure to the correctional system remains an important barrier to retention in HIV/AIDS treatment and care. Future research should evaluate structural interventions to address these barriers and facilitate the scale-up of TasP-based efforts among individuals living in correctional settings. PMID:24962285

  10. Size-differential feeding in Pinna nobilis L. (Mollusca: Bivalvia): Exploitation of detritus, phytoplankton and zooplankton

    NASA Astrophysics Data System (ADS)

    Davenport, John; Ezgeta-Balić, Daria; Peharda, Melita; Skejić, Sanda; Ninčević-Gladan, Živana; Matijević, Slavica

    2011-04-01

    The endangered fan shell Pinna nobilis is a large bivalve mollusc (<120 cm shell length) endemic to the Mediterranean that lives one-third buried in soft substrata, generally in shallow coastal waters. We hypothesised that P. nobilis of different sizes would ingest different food sources, because small fan shells will inhale material from closer to the substratum than do large fan shells. We studied stomach contents and faeces of 18 fan shells, 6 small (mean 23.0 cm length), 6 medium-sized (mean 41.5 cm length) and 6 large (mean 62.7 cm length) living in a small area of a low-energy coastal detritic bottom characterised by mud, sand and macroalgae at Mali Ston Bay, Croatia. We found that all P. nobilis ingested copious quantities of undetermined detritus (probably at least 95% of ingested material), phytoplankton, micro and mesozooplankton and pollen grains. Large P. nobilis stomach contents showed a preponderance of water column calanoid copepods, while small fan shells had higher numbers of bivalve larvae. All fan shells took in high numbers of harpacticoid copepods that are benthonic, feeding on microbial communities of detritus and benthic vegetation. There was also a significant selection of phytoplankton species, some apparently occurring between inhalation and ingestion. The stomach contents of small P. nobilis had a higher organic matter content than either medium-sized or large fan shells; this indicated that small fan shells ingested detritus of higher organic content than did larger P. nobilis. As the faeces of all P. nobilis had similar organic matter content, this also indicates higher assimilation efficiencies in small fan shells. The demonstration of differential dietary selectivity by different sized animals has implications for future trophic studies of this endangered species. This study also provides the first demonstration of predation on zooplankton by P. nobilis.

  11. Seeds of alpine plants are short lived: implications for long-term conservation

    PubMed Central

    Mondoni, Andrea; Probert, Robin J.; Rossi, Graziano; Vegini, Emanuele; Hay, Fiona R.

    2011-01-01

    Background and Aims Alpine plants are considered one of the groups of species most sensitive to the direct and indirect threats to ecosystems caused by land use and climate change. Collecting and banking seeds of plant species is recognized as an effective tool for providing propagating material to re-establish wild plant populations and for habitat repair. However, seeds from cold wet environments have been shown to be relatively short lived in storage, and therefore successful long-term seed conservation for alpine plants may be difficult. Here, the life spans of 69 seed lots representing 63 related species from alpine and lowland locations from northern Italy are compared. Methods Seeds were placed into experimental storage at 45 °C and 60 % relative humidity (RH) and regularly sampled for germination. The time taken in storage for viability to fall to 50 % (p50) was determined using probit analysis and used as a measure of relative seed longevity between seed lots. Key Results Across species, p50 at 45 °C and 60 % RH varied from 4·7 to 95·5 d. Seed lots from alpine populations/species had significantly lower p50 values compared with those from lowland populations/species; the lowland seed lots showed a slower rate of loss of germinability, higher initial seed viability, or both. Seeds were progressively longer lived with increased temperature and decreased rainfall at the collecting site. Conclusions Seeds of alpine plants are short lived in storage compared with those from lowland populations/related taxa. The lower resistance to ageing in seeds of alpine plants may arise from low selection pressure for seed resistance to ageing and/or damage incurred during seed development due to the cool wet conditions of the alpine climate. Long-term seed conservation of several alpine species using conventional seed banking methods will be problematic. PMID:21081585

  12. Comparing families and staff in nursing homes and assisted living: implications for social work practice.

    PubMed

    Zimmerman, Sheryl; Cohen, Lauren W; Reed, David; Gwyther, Lisa P; Washington, Tiffany; Cagle, John G; Beeber, Anna S; Sloane, Philip D

    2013-01-01

    Nursing homes and residential care/assisted living settings provide care to 2.4 million individuals. Few studies compare the experience of, and relationships between, family and staff in these settings, despite ongoing family involvement and evidence that relationships are problematic. Data from 488 families and 397 staff members in 24 settings examined family involvement and family and staff burden, depressive symptoms, and perceptions; and staff absenteeism and turnover. There were few differences across setting types. Although conflict rarely occurred, there was room for improvement in family-staff relations; this area, and preparing family for their caregiving roles, are appropriate targets for social work intervention. PMID:23869592

  13. Characterization of the live salmonid movement network in Ireland: Implications for disease prevention and control.

    PubMed

    Yatabe, T; More, S J; Geoghegan, F; McManus, C; Hill, A E; Martínez-López, B

    2015-11-01

    Live fish movement is considered as having an important role in the transmission of infectious diseases. For that reason, interventions for cost-effective disease prevention and control rely on a sound understanding of the patterns of live fish movements in a region or country. Here, we characterize the network of live fish movements in the Irish salmonid farming industry during 2013, using social network analysis and spatial epidemiology methods, and identify interventions to limit the risk of disease introduction and spread. In the network there were 62 sites sending and/or receiving fish, with a total of 130 shipments (84 arcs) comprising approx. 17.2 million fish during the year. Atlantic salmon shipments covered longer distances than trout shipments, with some traversing the entire country. The average shipment of Atlantic salmon was 146,186 (SD 194,344) fish, compared to 77,928 (127,009) for trout, however, variability was high. There were 3 periods where shipments peaked (February-April, June-September, and November), which were related to specific stages of fish. The network was disconnected and had two major weak components, the first one with 39 nodes (mostly Atlantic salmon sites), and the second one with 10 nodes (exclusively trout sites). Correlation between in and out-degree at each site and assortativity coefficient were slightly low and non-significant: -0.08 (95% CI: -0.22, 0.06) and -0.13 (95% CI: -0.36, 0.08), respectively, indicating random mixing with regard to node degree. Although competing models also produced a good fit to degree distribution, it is likely that the network possesses both small-world and scale-free topology. This would facilitate the spread and persistence of infection in the salmon production system, but would also facilitate the design of risk-based surveillance strategies by targeting hubs, bridges or cut-points. Using Infomap community detection algorithms, 2 major communities were identified within the giant weak

  14. Emerging trends in free-living amebic infections of the brain: implications for organ transplantation.

    PubMed

    Diaz, James H; Boudreaux, J Philip

    2013-01-01

    This epidemiological review analyzed cases of Naegleria fowleri primary amebic meningoencephalitis (PAM) and Balamuthia mandrillaris granulomatous amebic encephalitis (GAE) for behavioral and demographic risk factors for pathogen exposures and potential transmission by organ transplantation. The Centers for Disease Control and Prevention (CDC) Naegleria Workgroup Registry provided 121 cases of laboratory-confirmed PAM over the period, 1937-2007. The CDC and the California Encephalitis Project provided 28 cases of GAE over the period, 1994-2010. There was a statistically significant increase in clusters of PAM cases between the periods, 1937-1996 and 1997-2007. Risk factors for PAM included male gender, freshwater exposures, summer exposures, and exposures in southern-tier US (United States) states. Risk factors for GAE included male gender, exposures in southern-tier US states, Hispanic ethnicity in California, occupational or recreational contacts with soil, and recent organ transplantation. Fatal free-living amebic infections of the brain are increasing today due to more frequent environmental, recreational, and occupational exposures; organ transplantation; and unanticipated clusters of PAM due to N. fowleri inoculations following nasal sinus irrigation using neti pots filled with municipal tap water. Potential organ donors dying from meningoencephalitis of unexplained causes should be screened for free-living amebic infections of the brain capable of hematogenous dissemination in organ recipients. PMID:25073256

  15. Perceived threat in childhood: a review of research and implications for children living in violent households.

    PubMed

    Miller, Laura E

    2015-04-01

    The current study is a review of existing literature on perceived threat across childhood (0-19 years). There is strong evidence from this body of research that threat detection emerges in infancy and is present throughout childhood, with meaningful links to child adjustment. The wide range of methodologies employed to assess threat include biological measures (event-related potential and functional magnetic resonance imaging), observational data (gaze duration and response time), and a range of ways of gathering cognitive data (threat appraisal). Across methodologies, a uniform finding is that children who have higher threat attenuation are at increased risk for the development of anxiety disorders. It also seems that children's attention to threatening stimuli may vary across development, with heightened attention in infancy and early childhood. These findings have meaningful extensions for children who are living in violent families. Since many children living in violent homes are exposed to the threat of violence beginning in infancy, these children may be at heightened risk as compared to their nonexposed peers for the development of maladaptive patterns of threat detection and response. There is some evidence that this long-standing pattern of vigilance toward threat in key developmental periods may in part explain the increased risk of the development of anxiety disorders and posttraumatic stress disorder following exposure to violence. PMID:24562723

  16. Why and how to compensate living organ donors: ethical implications of the new Australian scheme.

    PubMed

    Giubilini, Alberto

    2015-05-01

    The Australian Federal Government has announced a two-year trial scheme to compensate living organ donors. The compensation will be the equivalent of six weeks paid leave at the rate of the national minimum wage. In this article I analyse the ethics of compensating living organ donors taking the Australian scheme as a reference point. Considering the long waiting lists for organ transplantations and the related costs on the healthcare system of treating patients waiting for an organ, the 1.3 million AUD the Australian Government has committed might represent a very worthwhile investment. I argue that a scheme like the Australian one is sufficiently well designed to avoid all the ethical problems traditionally associated with attaching a monetary value to the human body or to parts of it, namely commodification, inducement, exploitation, and equality issues. Therefore, I suggest that the Australian scheme, if cost-effective, should represent a model for other countries to follow. Nonetheless, although I endorse this scheme, I will also argue that this kind of scheme raises issues of justice in regard to the distribution of organs. Thus, I propose that other policies would be needed to supplement the scheme in order to guarantee not only a higher number of organs available, but also a fair distribution. PMID:24654885

  17. Implications of living with a strong family history of breast cancer.

    PubMed

    Maheu, Christine

    2009-06-01

    The findings presented here are from a qualitative study in which data were gathered from 20 women who had received inconclusive genetic testing results for inherited breast cancer susceptibility. Before describing the significance, for them, of their genetic test results, all of the participants related what it was like to live with a strong family history of breast cancer. The focus of this article is the women's experience of living with a personal and strong family history of breast cancer. For these women, having such a history had become a fact of life that could not be ignored.Three themes were identified in the data: expecting and dealing with a diagnosis of breast cancer protecting oneself and others, and increasing exposure to cancer screening procedures. These themes address the underlying reality that having a personal and family history of breast cancer is not an isolated situation but part of one's journey in choosing to undergo genetic testing for inherited breast cancer susceptibility. PMID:19650516

  18. Depression and Apathy Among People Living with HIV: Implications for Treatment of HIV Associated Neurocognitive Disorders

    PubMed Central

    Whitehead, Nicole E.; Burrell, Larry E.; Dotson, Vonetta M.; Cook, Robert L.; Malloy, Paul; Devlin, Kathryn; Cohen, Ronald A.

    2015-01-01

    Depression and apathy are common among people living with HIV (PLWH). However, in PLWH, it is unclear whether depression and apathy are distinct conditions, which contribute to different patterns of disruption to cognitive processing and brain systems. Understanding these conditions may enable the development of prognostic indicators for HIV associated neurocognitive disorders (HAND). The present study examined substance use behavior and cognitive deficits, associated with depression and apathy, in 120 PLWH, using hierarchical regression analyses. Higher levels of depression were associated with a history of alcohol dependence and greater deficits in processing speed, motor and global cognitive functioning. Higher levels of apathy were associated with a history of cocaine dependence. It is recommended that PLWH get screened appropriately for apathy and depression, in order to receive the appropriate treatment, considering the comorbidities associated with each condition. Future research should examine the neurological correlates of apathy and depression in PLWH. PMID:25533921

  19. Microfinance: a general overview and implications for impoverished individuals living with HIV/AIDS.

    PubMed

    Caldas, Adolfo; Arteaga, Fernando; Muñoz, Maribel; Zeladita, Jhon; Albujar, Mayler; Bayona, Jaime; Shin, Sonya

    2010-08-01

    Microfinance among people living with HIV/AIDS (PLWHA) faces some opposition and remains understudied. This literature review examines microfinance's evolution and impact on a variety of social and health indicators and its emerging implementation as a primary prevention tool for HIV and economic intervention for PLWHA. There is an abundance of literature supporting the apparent utility of microfinance. However, our understanding of the subject remains clouded by the heterogeneity and methodological limitations of existing impact studies, and access limitations to microfinance curbs our understanding of microfinance for this population. Existing literature suggests PLWHA could attain economic stability from microfinance and achieve successful repayment rates in some settings. The precarious socioeconomic and health issues of PLWHA pose unique challenges to minimizing loan default risk. Carefully-designed clinical studies are needed to assess whether PLWHA can be as successful with microfinance as healthy individuals. PMID:20693740

  20. Live pig markets in eastern Indonesia: Trader characteristics, biosecurity and implications for disease spread.

    PubMed

    Leslie, Edwina E C; Geong, Maria; Abdurrahman, Muktasam; Ward, Michael P; Toribio, Jenny-Ann L M L

    2016-03-01

    Classical swine fever has been negatively impacting pig production in Nusa Tenggara Timur province in eastern Indonesia since its introduction in the 1990s, with live market trade contributing to disease spread. To understand market trader knowledge and practices regarding pig management, biosecurity, pig movements and pig health (specifically CSF), a repeated survey was conducted with pig sellers and pig buyers at 9 market sites across West Timor and the islands of Flores and Sumba. A total of 292 sellers and 281 buyers were interviewed in 2009 during two periods (rounds), a high-demand month (September) and a low-demand month (November). Information was collected via questionnaire. The majority of traders were male (sellers: 89%; buyers: 87%) with the highest level of completed education being primary school (sellers: 48%; buyers: 41%). The primary occupation of most respondents was farming: 90% of sellers and 87% of buyers were smallholder pig farmers and tended to sell their own home-raised pigs at market (52%). Pigs were sold for monetary gain either for primary (52%) or extra income (44%). Markets tended to be selected based on a good reputation (62%), a location close to residence (62%) and having the desired pig type (59%). Pig sales through markets were reported to be highest from August to October with 31% of sellers trading pigs at two or more markets. Prices at market were significantly higher on Sumba compared to West Timor and cross-bred pigs were significantly more expensive than indigenous pigs. Understanding of CSF and biosecurity was limited: 85% of sellers and 83% of buyers had no prior knowledge of CSF. Fifty-four percent of sellers reported no use of any biosecurity practices at market. Most respondents (88%) were able to recognise at least one clinical sign of a sick pig. Informal pig movements were also identified: 18% of pig buyers purchased pigs directly from other farmers. This study has provided baseline information on market trader

  1. Preserving the longevity of long-lived type II collagen and its implication for cartilage therapeutics.

    PubMed

    Tiku, Moti L; Madhan, Balaraman

    2016-07-01

    Human life expectancy has been steadily increasing at a rapid rate, but this increasing life span also brings about increases in diseases, dementia, and disability. A global burden of disease 2010 study revealed that hip and knee osteoarthritis ranked the 11th highest in terms of years lived with disability. Wear and tear can greatly influence the quality of life during ageing. In particular, wear and tear of the articular cartilage have adverse effects on joints and result in osteoarthritis. The articular cartilage uses longevity of type II collagen as the foundation around which turnover of proteoglycans and the homeostatic activity of chondrocytes play central roles thereby maintaining the function of articular cartilage in the ageing. The longevity of type II collagen involves a complex interaction of the scaffolding needs of the cartilage and its biochemical, structural and mechanical characteristics. The covalent cross-linking of heterotypic polymers of collagens type II, type IX and type XI hold together cartilage, allowing it to withstand ageing stresses. Discerning the biological clues in the armamentarium for preserving cartilage appears to be collagen cross-linking. Therapeutic methods to crosslink in in-vivo are non-existent. However intra-articular injections of polyphenols in vivo stabilize the cartilage and make it resistant to degradation, opening a new therapeutic possibility for prevention and intervention of cartilage degradation in osteoarthritis of aging. PMID:27133944

  2. Mortality among People Living with HIV and AIDS in China: Implications for Enhancing Linkage

    PubMed Central

    Li, Meng; Tang, Weiming; Bu, Kai; Mahapatra, Tanmay; Zhang, Xiayan; Feng, Yibing; Chen, Fangfang; Guo, Wei; Wang, Liyan; Ding, Zhengwei; Qin, Qianqian; Liu, Shiliang; Tucker, Joseph D.; Wang, Lu; Wang, Ning

    2016-01-01

    To assess the patterns and predictors of AIDS-related mortality and identify its correlates among adult people living with HIV/AIDS (PLWHA) in China, a retrospective record-based cohort study was conducted among 18 years or older PLWHA, who had at least one follow up reported to the national database between January-1989 and June-2012. Cumulative Incidence Function was used to calculate AIDS-related mortality rate. Gray’s test was used to determine the variation in cumulative incidence across strata. The Fine and Gray model was used to measure the burden of cumulative incidence of AIDS-related mortality and strength of its association with potential correlates. Among 375,629 patients, 107,634 died during study period, of which 54,759 (50.87%) deaths were AIDS-related. Cumulative mortality rates of AIDS-related death at one, two, five, 10 and 15 years post-diagnosis were 5.7%, 8.2%, 14.3%, 22.9% and 30.9%, respectively. Among PLWHA, male gender, ethnic minority and having AIDS were associated with significantly higher mortality. Further, homosexual transmission, being on ART and increasing CD4-testing frequency were associated with lower mortality. To reduce mortality among PLWHA, efficient interventions targeting males, ethnic minority, heterosexually infected and AIDS patients should be combined with immunologic monitoring, enhancement of coverage of HIV-testing and ART. PMID:27324204

  3. HIV stigma among substance abusing people living with HIV/AIDS: implications for HIV treatment.

    PubMed

    Levi-Minzi, Maria A; Surratt, Hilary L

    2014-08-01

    HIV-related stigma has a major impact on quality of life and health among people living with HIV and AIDS (PLWHA). This study examines demographic, mental health, behavioral, contextual, and HIV care-related correlates of HIV stigma among 503 substance abusing PLWHA. Stigma was measured with the HIV Internalized Stigma Measure which has four subscales: stereotypes about HIV, self-acceptance, disclosure concerns, and social relationships. Severe substance dependence (55.3%) and depression (54.7%) were associated with higher HIV stigma across all domains. 49.9% of the sample reported antiretroviral (ARV) medication diversion (the unlawful sale and trading of ARV medications); diverters endorsed significantly higher stigma related to disclosure. 54.1% of the sample reported ≥95% ARV adherence; these individuals reported significantly lower stigma for self-acceptance, disclosure, and social relationships. Multivariate linear regression showed that depression and social support demonstrated significant main effects across stigma domains. Findings suggest that interventions to decrease HIV related stigma may be an important component of initiatives to increase engagement in HIV care. PMID:24983302

  4. Mortality among People Living with HIV and AIDS in China: Implications for Enhancing Linkage.

    PubMed

    Li, Meng; Tang, Weiming; Bu, Kai; Mahapatra, Tanmay; Zhang, Xiayan; Feng, Yibing; Chen, Fangfang; Guo, Wei; Wang, Liyan; Ding, Zhengwei; Qin, Qianqian; Liu, Shiliang; Tucker, Joseph D; Wang, Lu; Wang, Ning

    2016-01-01

    To assess the patterns and predictors of AIDS-related mortality and identify its correlates among adult people living with HIV/AIDS (PLWHA) in China, a retrospective record-based cohort study was conducted among 18 years or older PLWHA, who had at least one follow up reported to the national database between January-1989 and June-2012. Cumulative Incidence Function was used to calculate AIDS-related mortality rate. Gray's test was used to determine the variation in cumulative incidence across strata. The Fine and Gray model was used to measure the burden of cumulative incidence of AIDS-related mortality and strength of its association with potential correlates. Among 375,629 patients, 107,634 died during study period, of which 54,759 (50.87%) deaths were AIDS-related. Cumulative mortality rates of AIDS-related death at one, two, five, 10 and 15 years post-diagnosis were 5.7%, 8.2%, 14.3%, 22.9% and 30.9%, respectively. Among PLWHA, male gender, ethnic minority and having AIDS were associated with significantly higher mortality. Further, homosexual transmission, being on ART and increasing CD4-testing frequency were associated with lower mortality. To reduce mortality among PLWHA, efficient interventions targeting males, ethnic minority, heterosexually infected and AIDS patients should be combined with immunologic monitoring, enhancement of coverage of HIV-testing and ART. PMID:27324204

  5. The consistency of self-reported preferences for everyday living: Implications for person centered care delivery

    PubMed Central

    Van Haitsma, Kimberly; Abbott, Katherine; Heid, Allison R.; Carpenter, Brian; Curyto, Kimberly; Kleban, Morton; Eshraghi, Karen; Duntzee, Christina I.; Spector, Abby

    2016-01-01

    Preferences are the expression of individuals’ basic psychosocial needs and are related to care outcomes. This study tested the consistency of people’s everyday preferences over one week, comparing responses of nursing home residents (n = 37; mean age 82) and university students (n = 50; average age 20). Participants completed the Preferences for Everyday Living Inventory at baseline and 5–7 days later. Preference consistency was calculated three ways. First, we calculated correlations (range = .11–.90), then the overall percent of exact agreement (e.g., response was “very important” at both time points), which was 66.1%. Lastly, we collapsed responses to “important” or “not important” and found an increase in percent agreement (86.6%). Personal care preferences were more stable, while leisure activities were less stable. The groups did not have significant differences in consistency. Some preferences are more consistent than others; age and frailty alone do not appear related to preference instability. PMID:25199153

  6. A model for partitioning particulate absorption into phytoplanktonic and detrital components

    NASA Astrophysics Data System (ADS)

    Cleveland, J. S.; Perry, M. J.

    1994-01-01

    A model for partitioning total particulate absorption, measured on glass fiber filters, into phytoplanktonic and detrital components is developed. The model reconstructs absorption spectra for living phytoplankton using total particulate absorption at the red absorption maxima for chlorophylls a and b, concentrations of chlorophyll a and pheopigment, and mean normalized absorption spectra for laboratory-grown algal cultures. The model was developed in stages for two types of phytoplankton assemblages. Section A of the model applies to waters dominated by eukaryotic algae and is based on absorption spectra for chromophytic (phytoplankton containing chlorophyll c) and chlorophytic (containing chlorophyll b) species. Section B of the model, allowing more variability in spectral shape, was developed for algal communities with more diverse pigmentation. All spectra are processed through Section A, with an internal evaluation determining whether processing continues through Section B. Detrital spectra, generated as the difference between total particulate and modelled phytoplanktonic spectra, included pheopigment absorption and had high blue absorption. Blind tests on samples of known composition predicted absorption within 8-10% at 436 nm and 1-13% when averaged from 400 to 700 nm, which is within the expected accuracy of the glass fiber filter method. No true measure of phytoplankton absorption in field samples is available for testing the model, but results from methanol-extractions were used for comparison despite inclusion of pheopigment absorption as "phytoplankton". For samples collected from coastal waters of Washington State, the Sargasso Sea and coastal waters of Norway, modelled absorption (averaged over 400-700 nm) ranged from 25% lower to 0.5% higher than the methanol-extraction results; pheopigment absorption inappropriately included in the phytoplankton component accounts for the higher phytoplanktonic absorption estimated by the methanol technique

  7. Production of n-alkyl lipids in living plants and implications for the geologic past

    NASA Astrophysics Data System (ADS)

    Diefendorf, Aaron F.; Freeman, Katherine H.; Wing, Scott L.; Graham, Heather V.

    2011-12-01

    Leaf waxes (i.e., n-alkyl lipids or n-alkanes) are land-plant biomarkers widely used to reconstruct changes in climate and the carbon isotopic composition of the atmosphere. There is little information available, however, on how the production of leaf waxes by different kinds of plants might influence the abundance and isotopic composition of n-alkanes in sedimentary archives. This lack of information increases uncertainty in interpreting n-alkyl lipid abundance and δ 13C signals in ancient settings. We provide here n-alkyl abundance distributions and carbon isotope fractionation data for deciduous and evergreen angiosperm and gymnosperm leaves from 46 tree species, representing 24 families. n-Alkane abundances are significantly higher in angiosperms than gymnosperms; many of the gymnosperm species investigated did not produce any n-alkanes. On average, deciduous angiosperms produce 200 times more n-alkanes than deciduous gymnosperms. Although differences between angiosperms and gymnosperms dominate the variance in n-alkane abundance, leaf life-span is also important, with higher n-alkane abundances in longer-lived leaves. n-Alkanol abundances covary with n-alkanes, but n-alkanoic acids have similar abundances across all plant groups. Isotopic fractionation between leaf tissue and individual alkanes ( ɛlipid) varies by as much as 10‰ among different chain lengths. Overall, ɛlipid values are slightly lower (-4.5‰) for angiosperm than for gymnosperm (-2.5‰) n-alkanes. Angiosperms commonly express slightly higher Δleaf (photosynthetic discrimination) relative to gymnosperms under similar growth conditions. As a result, angiosperm n-alkanes are expected to be generally 3-5‰ more depleted in 13C relative to gymnosperm alkanes for the same locality. Differences in n-alkane production indicate the biomarker record will largely (but not exclusively) reflect angiosperms if both groups were present, and also that evergreen plants will likely be overrepresented

  8. Caregiver satisfaction with paediatric HIV treatment and care in Nigeria and equity implications for children living with HIV

    PubMed Central

    Chamla, Dick; Asadu, Chukwuemeka; Adejuyigbe, Ebun; Davies, Abiola; Ugochukwu, Ebele; Umar, Lawal; Oluwafunke, Ilesanmi; Hassan-Hanga, Fatimah; Onubogu, Chinyere; Tunde-Oremodu, Immaculata; Madubuike, Chinelo; Umeadi, Esther; Epundu, Obed; Omosun, Adenike; Anigilaje, Emmanuel; Adeyinka, Daniel

    2016-01-01

    ABSTRACT Caregiver satisfaction has the potential to promote equity for children living with HIV, by influencing health-seeking behaviour. We measured dimensions of caregiver satisfaction with paediatric HIV treatment in Nigeria, and discuss its implications for equity by conducting facility-based exit interviews for caregivers of children receiving antiretroviral therapy in 20 purposively selected facilities within 5 geopolitical zones. Descriptive analysis and factor analysis were performed. Due to the hierarchical nature of the data, multilevel regression modelling was performed to investigate relationships between satisfaction factors and socio-demographic variables. Of 1550 caregivers interviewed, 63% (95% CI: 60.6–65.4) reported being very satisfied overall; however, satisfaction varied in some dimensions: only 55.6% (53.1–58.1) of caregivers could talk privately with health workers, 56.9% (54.4–59.3) reported that queues to see health workers were too long, and 89.9% (88.4–91.4) said that some health workers did not treat patients living with HIV with sufficient respect. Based on factor analysis, two underlying factors, labelled Availability and Attitude, were identified. In multilevel regression, the satisfaction with availability of services correlated with formal employment status (p < .01), whereas caregivers receiving care in private facilities were less likely satisfied with both availability (p < .01) and attitude of health workers (p < .05). State and facility levels influenced attitudes of the health workers (p < .01), but not availability of services. We conclude that high levels of overall satisfaction among caregivers masked dissatisfaction with some aspects of services. The two underlying satisfaction factors are part of access typology critical for closing equity gaps in access to HIV treatment between adults and children, and across socio-economic groups. PMID:27392010

  9. Phytoplankton fuels Delta food web

    USGS Publications Warehouse

    Jassby, Alan D.; Cloern, James E.; Muller-Solger, A. B.

    2003-01-01

    Populations of certain fishes and invertebrates in the Sacramento-San Joaquin Delta have declined in abundance in recent decades and there is evidence that food supply is partly responsible. While many sources of organic matter in the Delta could be supporting fish populations indirectly through the food web (including aquatic vegetation and decaying organic matter from agricultural drainage), a careful accounting shows that phytoplankton is the dominant food source. Phytoplankton, communities of microscopic free-floating algae, are the most important food source on a Delta-wide scale when both food quantity and quality are taken into account. These microscopic algae have declined since the late 1960s. Fertilizer and pesticide runoff do not appear to be playing a direct role in long-term phytoplankton changes; rather, species invasions, increasing water transparency and fluctuations in water transport are responsible. Although the potential toxicity of herbicides and pesticides to plank- ton in the Delta is well documented, the ecological significance remains speculative. Nutrient inputs from agricultural runoff at current levels, in combination with increasing transparency, could result in harmful al- gal blooms. 

  10. Zombies, vampires, werewolves: an adolescent's developmental system for the undead and their ambivalent dependence on the living, and technical implications.

    PubMed

    Szajnberg, Nathan Moses

    2012-12-01

    While vampires haunt contemporary American pop culture, the undead have populated psychoanalytic literature from Abraham's March 15, 1915 letter to Freud to today. PEP lists 439 psychoanalytic references to the undead (99 on zombies; 288 on vampires; 52 on werewolves). A selection of papers are cited, focusing on clinical cases, ethnography media and literature, even breast-feeding fantasized as blood sucking, associated with primitive dynamics. Previous works' libidinal, object relations, and dynamic perspectives on various "undeads" are summarized. This paper's contribution to the psychoanalytic literature is to examine the relationship of the three categories of undead both among each other and in their relation to the living. This paper presents a young adolescent's extensive play and fantasies about the undead, and his sophisticated intrapsychic model for the undead, developed prior to treatment, that kept him in psychical equilibrium, yet also kept him from feeling alive. This model has developmental implications for handling three types of transferences. Also, we may shed light on both contemporary preoccupation with the undead in contemporary American popular culture, and its endurance over time in Western culture. PMID:23253062

  11. State of Climate 2011 - Global Ocean Phytoplankton

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  12. Community composition has greater impact on the functioning of marine phytoplankton communities than ocean acidification.

    PubMed

    Eggers, Sarah L; Lewandowska, Aleksandra M; Barcelos E Ramos, Joana; Blanco-Ameijeiras, Sonia; Gallo, Francesca; Matthiessen, Birte

    2014-03-01

    Ecosystem functioning is simultaneously affected by changes in community composition and environmental change such as increasing atmospheric carbon dioxide (CO2 ) and subsequent ocean acidification. However, it largely remains uncertain how the effects of these factors compare to each other. Addressing this question, we experimentally tested the hypothesis that initial community composition and elevated CO2 are equally important to the regulation of phytoplankton biomass. We full-factorially exposed three compositionally different marine phytoplankton communities to two different CO2 levels and examined the effects and relative importance (ω(2) ) of the two factors and their interaction on phytoplankton biomass at bloom peak. The results showed that initial community composition had a significantly greater impact than elevated CO2 on phytoplankton biomass, which varied largely among communities. We suggest that the different initial ratios between cyanobacteria, diatoms, and dinoflagellates might be the key for the varying competitive and thus functional outcome among communities. Furthermore, the results showed that depending on initial community composition elevated CO2 selected for larger sized diatoms, which led to increased total phytoplankton biomass. This study highlights the relevance of initial community composition, which strongly drives the functional outcome, when assessing impacts of climate change on ecosystem functioning. In particular, the increase in phytoplankton biomass driven by the gain of larger sized diatoms in response to elevated CO2 potentially has strong implications for nutrient cycling and carbon export in future oceans. PMID:24115206

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

    PubMed

    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

  14. An unusually large phytoplankton spring bloom drives rapid changes in benthic diversity and ecosystem function

    NASA Astrophysics Data System (ADS)

    Zhang, Qingtian; Warwick, Richard M.; McNeill, Caroline L.; Widdicombe, Claire E.; Sheehan, Aaron; Widdicombe, Stephen

    2015-09-01

    In 2012, the Western English Channel experienced an unusually large and long-lived phytoplankton spring bloom. When compared with data from the past 20 years, average phytoplankton biomass at Station L4 (part of the Western Channel Observatory) was approximately 3× greater and lasted 50% longer than any previous year. Regular (mostly weekly) box core samples were collected from this site before, during and after the bloom to determine its impact on macrofaunal abundance, diversity, biomass, community structure and function. The spring bloom of 2012 was shown to support a large and rapid response in the majority of benthic taxa and functional groups. However, key differences in the precise nature of this response, as well as in its timing, was observed between different macrofauna feeding groups. Deposit feeders responded almost instantly at the start of the bloom, primarily thorough an increase in abundance. Suspension feeders and opportunistic/predatory/carnivorous taxa responded slightly more slowly and primarily with an increase in biomass. At the end of the bloom a rapid decline in macrobenthic abundance, diversity and biomass closely followed the decline in phytoplankton biomass. With suspension feeders showing evidence of this decline a few weeks before deposit feeders, it was concluded that this collapse in benthic communities was driven primarily by food availability and competition. However, it is possible that environmental hypoxia and the presence of toxic benthic cyanobacteria could also have contributed to this decline. This study shows evidence for strong benthic-pelagic coupling at L4; a shallow (50 m), coastal, fine-sand habitat. It also demonstrates that in such habitats, it is not just planktonic organisms that demonstrate clear community phenology. Different functional groups within the benthic assemblage will respond to the spring bloom in specific manner, with implications for key ecosystem functions and processes, such as secondary production

  15. Seasonal mercury levels in phytoplankton and their relationship with algal biomass in two dystrophic shield lakes

    SciTech Connect

    Kirkwood, A.E.; Chow-Fraser, P.; Mierle, G.

    1999-03-01

    This study focused on the seasonal dynamics of total Hg in the phytoplankton (living and dead) of two dystrophic shield lakes (Mouse and Ranger). Phytoplankton samples were taken from metalimnetic and hypolimnetic depths in the euphotic zone and were collected and analyzed using ultraclean techniques. In both lakes, phytoplankton Hg (PHYTO-Hg) levels (pg/L) in the metalimnion did not significantly change among dates over the season, although Ranger Lake exhibited significant differences between Hg values measured at the beginning and end of the season. In contrast, PHYTO-Hg significantly increased in the hypolimnia of both lakes by the end of the season. Combined influences of external Hg inputs, remineralization, phytoplankton sedimentation, and increased methylmercury production in the hypolimnia over the season may have contributed to these trends. A highly significant positive relationship existed between PHYTO-Hg levels and whole-water Hg levels, and the mean bioconcentration factor for Hg between the water column and phytoplankton was significantly higher in the hypolimnion compared to the metalimnion for both lakes. In most cases, parameters associated with algal biomass had significant positive correlations with PHYTO-Hg levels. Weight-specific PHYTO-Hg (pg/mg dry weight) varied significantly over the season, and there were interlake differences with respect to season trends. On the basis of these results, the authors recommend that the future sampling regimes include collection of phytoplankton at different limnetic depths through the season to account for spatial and temporal variations. Weight specific Hg levels in phytoplankton could not be explained well by the parameters tested, and the only significant regressions were with parameters reflecting algal biomass. This study provides in situ evidence of Hg accumulation in lake phytoplankton as a function of algal biomass on a seasonal basis and stresses the need to confirm these trends in other lake

  16. Phytoplankton Assemblage Characteristics in Recurrently Fluctuating Environments

    PubMed Central

    Roelke, Daniel L.; Spatharis, Sofie

    2015-01-01

    Annual variations in biogeochemical and physical processes can lead to nutrient variability and seasonal patterns in phytoplankton productivity and assemblage structure. In many coastal systems river inflow and water exchange with the ocean varies seasonally, and alternating periods can arise where the nutrient most limiting to phytoplankton growth switches. Transitions between these alternating periods can be sudden or gradual and this depends on human activities, such as reservoir construction and interbasin water transfers. How such activities might influence phytoplankton assemblages is largely unknown. Here, we employed a multispecies, multi-nutrient model to explore how nutrient loading switching mode might affect characteristics of phytoplankton assemblages. The model is based on the Monod-relationship, predicting an instantaneous growth rate from ambient inorganic nutrient concentrations whereas the limiting nutrient at any given time was determined by Liebig’s Law of the Minimum. Our simulated phytoplankton assemblages self-organized from species rich pools over a 15-year period, and only the surviving species were considered as assemblage members. Using the model, we explored the interactive effects of complementarity level in trait trade-offs within phytoplankton assemblages and the amount of noise in the resource supply concentrations. We found that the effect of shift from a sudden resource supply transition to a gradual one, as observed in systems impacted by watershed development, was dependent on the level of complementarity. In the extremes, phytoplankton species richness and relative overyielding increased when complementarity was lowest, and phytoplankton biomass increased greatly when complementarity was highest. For low-complementarity simulations, the persistence of poorer-performing phytoplankton species of intermediate R*s led to higher richness and relative overyielding. For high-complementarity simulations, the formation of phytoplankton

  17. Phytoplankton plasticity drives large variability in carbon fixation efficiency

    NASA Astrophysics Data System (ADS)

    Ayata, Sakina-Dorothée.; Lévy, Marina; Aumont, Olivier; Resplandy, Laure; Tagliabue, Alessandro; Sciandra, Antoine; Bernard, Olivier

    2014-12-01

    Phytoplankton C:N stoichiometry is highly flexible due to physiological plasticity, which could lead to high variations in carbon fixation efficiency (carbon consumption relative to nitrogen). However, the magnitude, as well as the spatial and temporal scales of variability, remains poorly constrained. We used a high-resolution biogeochemical model resolving various scales from small to high, spatially and temporally, in order to quantify and better understand this variability. We find that phytoplankton C:N ratio is highly variable at all spatial and temporal scales (5-12 molC/molN), from mesoscale to regional scale, and is mainly driven by nitrogen supply. Carbon fixation efficiency varies accordingly at all scales (±30%), with higher values under oligotrophic conditions and lower values under eutrophic conditions. Hence, phytoplankton plasticity may act as a buffer by attenuating carbon sequestration variability. Our results have implications for in situ estimations of C:N ratios and for future predictions under high CO2 world.

  18. Self-sedimentation of phytoplankton blooms in the geologic record

    NASA Astrophysics Data System (ADS)

    Grimm, Kurt A.; Lange, Carina B.; Gill, Amarpal S.

    1997-06-01

    Understanding the formation of laminated, organic-rich sediments is an essential topic for researchers interested in fossil fuels, biogeochemical cycles, Earth's environmental history and global change. Biologists have very recently demonstrated that some marine phytoplankton blooms actively govern their own sedimentation by the formation of sticky transparent gels that facilitate rapid aggregation, accelerated sinking and efficient export flux. Here we present fossil evidence of unfragmented, low-diversity phytoplankton assemblages preserved as sedimentary laminae and irregular flocs that are attributable to a similar phytoplankton-driven sedimentary mechanism we term 'self-sedimentation'. The geological evidence suggests that self-sedimentation precludes significant heterotrophic grazing, propels the formation of some conspicuous hemipelagic sedimentary laminae and results in efficient carbon and opal flux to the sediments. We suggest that the self-sedimentation phenomenon may have broad implications for the geological history of biogeochemical cycling, oceanic ecological dynamics, and abrupt atmospheric/environmental change. Broader recognition of the self-sedimentation phenomenon as explicitly defined here is a prerequisite to testing these unconventional hypotheses.

  19. The physiology of dimethylsulfoniopropionate (DMSP) production in phytoplankton

    SciTech Connect

    Keller, M.D.; Bellows, W.K. )

    1990-06-01

    Dimethylsulfoniopropionate (DMSP) is the precursor of dimethyl sulfide (DMS), the primary volatile organic sulfur compound released from the world's oceans. DMS flux from the oceans is estimated currently at {approximately}1.2 Tmol S.y{sup {minus}1}, or about half the amount of sulfur resulting from anthroprogenic activities, and has been implicated in important global atmospheric processes. Significant production of DMSP is confined to a few classes of marine phytoplankton, primarily the Dinophyceae and Prymnesiophyceae. In these groups, DMSP can account for up to 80% of total organic sulfur. DMSP remains intracellular and fairly constant over the growth cycle until late stationary phase when extracellular levels begin to rise, suggesting leakage. We have examined the effects of a number of environmental variables on DMSP production and release in several marine phytoplankton. In particular the effects of perturbations in light, temperature and nutrient status have been determined. These results will be discussed in relation to marine sulfur chemistry, with ancillary comments on freshwater phytoplankton.

  20. Iron bioavailability to phytoplankton: an empirical approach

    PubMed Central

    Lis, Hagar; Shaked, Yeala; Kranzler, Chana; Keren, Nir; Morel, François M M

    2015-01-01

    Phytoplankton are often limited by iron in aquatic environments. Here we examine Fe bioavailability to phytoplankton by analyzing iron uptake from various Fe substrates by several species of phytoplankton grown under conditions of Fe limitation and comparing the measured uptake rate constants (Fe uptake rate/ substrate concentration). When unchelated iron, Fe′, buffered by an excess of the chelating agent EDTA is used as the Fe substrate, the uptake rate constants of all the eukaryotic phytoplankton species are tightly correlated and proportional to their respective surface areas (S.A.). The same is true when FeDFB is the substrate, but the corresponding uptake constants are one thousand times smaller than for Fe′. The uptake rate constants for the other substrates we examined fall mostly between the values for Fe′ and FeDFB for the same S.A. These two model substrates thus empirically define a bioavailability envelope with Fe′ at the upper and FeDFB at the lower limit of iron bioavailability. This envelope provides a convenient framework to compare the relative bioavailabilities of various Fe substrates to eukaryotic phytoplankton and the Fe uptake abilities of different phytoplankton species. Compared with eukaryotic species, cyanobacteria have similar uptake constants for Fe′ but lower ones for FeDFB. The unique relationship between the uptake rate constants and the S.A. of phytoplankton species suggests that the uptake rate constant of Fe-limited phytoplankton has reached a universal upper limit and provides insight into the underlying uptake mechanism. PMID:25350155

  1. PHYTOPLANKTON COMPOSITION AND DISTRIBUTION IN SAGINAW BAY

    EPA Science Inventory

    This summarizes studies conducted during 1980 to assess the effects of reductions in phosphorus loading to Saginaw Bay on phytoplankton in the bay and the adjacent waters of Lake Huron. Quantitative estimates of phytoplankton abundance were developed from an array of stations sam...

  2. Phytoplankton and sediments in Yellow Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Sediment and phytoplankton cloud the waters of the Yellow Sea in this true-color MODIS image acquired March 18, 2002. The swirls of sediment appear as a murky brownish blue color, while the phytoplankton are purely blue green and are concentrated around the small island in the lower right corner of the image.

  3. Sea Soup: Discovering the Watery World of Phytoplankton and Zooplankton. Teacher's Guide.

    ERIC Educational Resources Information Center

    Stevens, Betsy T.

    This book is an inquiry- and discovery-based teacher's guide. The interesting and fun activities in this teacher's guide meet the challenge of relating tiny, microscopic organisms to the lives of children. The inquiry-based activities range from designing and making a phytoplankter and collecting phytoplankton to designing an experiment for…

  4. The trace element fingerprint of phytoplankton in ocean particulate matter: positive ID or smudged residue?

    NASA Astrophysics Data System (ADS)

    Sherrell, R. M.; Jimonet, A.

    2004-12-01

    The biogeochemical cycles of many trace metals are directly or indirectly driven by the growth, vertical transport, and remineralization of phytoplankton. One of Jack Dymond's research interests was how the geochemical signals of biological processes determine the composition of sinking particulate matter and ultimately the sedimentary record. It seems obvious that there must be links between fundamental aspects of the physiology and biochemistry of phytoplankton growing under a range of oceanic conditions, and the composition of bulk oceanic particulate matter. However, too few attempts have been made to use experimental or observational elemental data to constrain predictions of particulate metal fluxes and their relationship to primary biological processes. On one hand, laboratory-determined metal quotas may suffer from unrealistic species composition and metal availability, and on the other hand attempts to analyze phytoplankton in field samples are typically frustrated by the inability to separate living cells from the abundant organic and inorganic nonliving particles found in most natural waters. Using multi-element analyses of suspended particles in Mid-Atlantic Bight shelf-slope surface waters, and correction factors for non-living particles, we argue that phytoplankton dominate bulk particulate composition for some metals (Zn, Cu, Cd), that non-living particles dominate for other metals (Ti, Fe), and that some metals may fall into either group (Mn, Co). The results show quantitative consistencies with results from diatom lab cultures, and hold promise for improved predictions of vertical metal fluxes associated with carbon export from the euphotic zone of characteristic oceanic regimes.

  5. Influence of eutrophication on air-water exchange, vertical fluxes, and phytoplankton concentrations of persistent organic pollutants

    SciTech Connect

    Dachs, J.; Eisenreich, S.J.; Hoff, R.M.

    2000-03-15

    The influence of eutrophication on the biogeochemical cycles of persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) is largely unknown. In this paper, the application of a dynamic air-water-phytoplankton exchange model to Lake Ontario is used as a framework to study the influence of eutrophication on air-water exchange, vertical fluxes, and phytoplankton concentrations of POPs. The results of these simulations demonstrate that air-water exchange controls phytoplankton concentrations in remote aquatic environments with little influence from land-based sources of pollutants and supports levels in even historically contaminated systems. Furthermore, eutrophication or high biomass leads to a disequilibrium between the gas and dissolved phase, enhanced air-water exchange, and vertical sinking fluxes of PCBs. Increasing biomass also depletes the water concentrations leading to lower than equilibrium PCB concentrations in phytoplankton. Implications to future trends in PCB pollution in Lake Ontario are also discussed.

  6. Composition of phytoplankton communities and their contribution to secondary productivity in Carolina Bays on the Savannah River Plant

    SciTech Connect

    Williams, J.B. . Dept. of Natural Sciences)

    1989-08-01

    The overall goal of this three-year project is to determine the importance of phytoplankton (microscopic algae) as a component of the food chain base in SRS Carolina Bays (shallow temporary ponds endemic to the Southeastern US). Previous investigations and ongoing SREL studies have determined the importance of Carolina bay zooplankton (microscopic crustacean herbivores) to the early life stages of amphibians. Our project is testing the hypothesis that phytoplankton are the primary component of zooplankton diets in these bays. Carolina Bays represent critical habitats for a whole class of vertebrates at SRS, the amphibians. Details of phytoplankton dynamics and productivity gained from our project will advance our understanding of ecological energetics within Carolina Bay systems. These results will also help determine the potential impact that these minute, but productive plants can have on SRS biota beyond the bounds of these aquatic ecosystems. Additional implications can be made concerning chemical elemental uptake and transfer from phytoplankton to higher trophic levels. 12 figs.

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

    PubMed

    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. PMID:25843351

  8. Factors affecting phytoplankton distribution and production in the Elephant Island area, Antarctica

    SciTech Connect

    Helbling, E.W.

    1993-01-01

    During the austral summer of four years, 1990 to 1993, studies on phytoplankton were performed in the Elephant Island area as one component of the US Antarctica Marine Living Resources program. In addition to continuous measurements (temperature, salinity, chlorophyll-a, beam attenuation) made on ship's intake water, a profiling CTD-rosette unit was used to obtain water column characteristics (temperature, salinity, chlorophyll-a, attenuation of solar radiation, beam attenuation) from the surface to 750m depth and also water samples from at least 10 depths for chemical and biological analyses. The sampling grid consisted of an average of 70 stations, all of which were occupied two times each year. The Elephant Island area is a transition zone between the rich coastal areas, where phytoplankton can develop dense blooms, and pelagic waters where the phytoplankton biomass is in general very low. A frontal zone was usually found to the north of Elephant Island and over the continental slope, and high phytoplankton biomass was in general associated with this frontal region. Although the location of this frontal system showed seasonal movement in a north-south direction, it seems to be a consistent feature from year to year. There seems to be considerable year-to-year variability in physical (water temperatures and salinity) and phytoplankton characteristics within the study area, in regard to both distributional patterns in surface waters and to profile characteristics in the upper 100m of the water column. With shallow upper mixed layer depths of less than 50 m, phytoplankton can attain relatively high concentrations. Optimum light conditions for growth occurred when the mixed layer was less than 55% of the euphotic zone. As the area around Elephant Island is characterized by relatively strong and frequent winds, the depth of the upper mixed layer at many stations approached the depth of the euphotic zone, with the result that growth of phytoplankton was light limited.

  9. Phytoplankton bloom in Persian Gulf

    NASA Technical Reports Server (NTRS)

    2002-01-01

    There is a large amount of sediment clearly visible in the true-color image of the Persian Gulf, acquired on November 1, 2001, by MODIS. Carried by the confluence of the Tigris and Euphrates Rivers (at center), the sediment-laden waters appear light brown where they enter the northern end of the Persian Gulf and then gradually dissipate into turquoise swirls as they drift southward. The nutrients these sediments carry are helping to support a phytoplankton bloom in the region, which adds some darker green hues in the rich kaleidoscope of colors on the surface (see the high resolution image). The confluence of the Tigris and Euphrates Rivers marks the southernmost boundary between Iran (upper right) and Iraq (upper left). South of Iraq are the countries of Kuwait and Saudi Arabia. The red dots indicate the probable locations of fires burning at oil refineries. Thin black plumes of smoke can be seen streaming away from several of these.

  10. The impact of temperature on marine phytoplankton resource allocation and metabolism

    NASA Astrophysics Data System (ADS)

    Toseland, A.; Daines, S. J.; Clark, J. R.; Kirkham, A.; Strauss, J.; Uhlig, C.; Lenton, T. M.; Valentin, K.; Pearson, G. A.; Moulton, V.; Mock, T.

    2013-11-01

    Marine phytoplankton are responsible for ~50% of the CO2 that is fixed annually worldwide, and contribute massively to other biogeochemical cycles in the oceans. Their contribution depends significantly on the interplay between dynamic environmental conditions and the metabolic responses that underpin resource allocation and hence biogeochemical cycling in the oceans. However, these complex environment-biome interactions have not been studied on a larger scale. Here we use a set of integrative approaches that combine metatranscriptomes, biochemical data, cellular physiology and emergent phytoplankton growth strategies in a global ecosystems model, to show that temperature significantly affects eukaryotic phytoplankton metabolism with consequences for biogeochemical cycling under global warming. In particular, the rate of protein synthesis strongly increases under high temperatures even though the numbers of ribosomes and their associated rRNAs decreases. Thus, at higher temperatures, eukaryotic phytoplankton seem to require a lower density of ribosomes to produce the required amounts of cellular protein. The reduction of phosphate-rich ribosomes in warmer oceans will tend to produce higher organismal nitrogen (N) to phosphate (P) ratios, in turn increasing demand for N with consequences for the marine carbon cycle due to shifts towards N-limitation. Our integrative approach suggests that temperature plays a previously unrecognized, critical role in resource allocation and marine phytoplankton stoichiometry, with implications for the biogeochemical cycles that they drive.

  11. RubisCO is not a major fraction of total protein in marine phytoplankton

    NASA Astrophysics Data System (ADS)

    Losh, J.; Young, J. N.; Morel, F. M.

    2012-12-01

    Ribulose 1,5 bisphosphate carboxylase oxygnenase (Rubisco) concentrations were quantified as a proportion of total protein in diatoms to determine whether Rubisco is as abundant in phytoplankton as previously thought. This enzyme has been assumed to be a major fraction of total protein in phytoplankton, as has been demonstrated in plants, potentially constituting a large sink for cellular nitrogen (N). Marine diatoms were grown in batch cultures, and in N-limited continuous cultures at various carbon dioxide (CO2) levels. Quantitative western blots were performed using commercially available global antibodies and protein standards. Field incubations with natural populations of organisms from the coast of California were conducted under both N-limited and N-replete incubations with varying CO2. In all experiments, Rubisco represented less than 5% of total protein. Within exponentially growing batch cultures, concentrations ranged from 2-4%, while in N-limited laboratory and field cultures, concentrations were less than 1%. In some experiments under N-limiting conditions, Rubisco concentrations decreased with decreasing growth rates or with increasing CO2. These results were used as a basis of a theoretical calculation of maximum Rubisco activity and suggest that phytoplankton contain the minimum amount of Rubisco necessary to operate. Unlike plants, Rubisco is not a major sink of cellular N in phytoplankton. This has implications for phytoplankton's response to increasing CO2 under N-limitation.

  12. Linking Quality of Life and Standard of Living Priorities with Rates of Return in Education: Implications for Ontario's Community Colleges

    ERIC Educational Resources Information Center

    Menna, Agostino

    2012-01-01

    This study begins to develop a way to measure the returns and benefits of education using a standard of living and quality of life approach. It sought identification of school priorities among senior level managers at postsecondary institutions in Ontario, Canada, and found that these administrators prioritized standard of living over quality of…

  13. Biochemical oxygen demand and algae: Fractionation of phytoplankton and nonphytoplankton respiration in a large river

    SciTech Connect

    Cohen, R.R.H. )

    1990-04-01

    Mass balance equations for dissolved oxygen in streams are formulated to account for, among other variables, algal respiration (R), and biochemical oxygen demand (BOD). The oxygen consumption measured in primary productivity-respiration analyses is not R but is total community oxygen consumption (TCOC), and BOD measurements are complicated by undefined algal components. Ultimate BOD was found to be 0.24 mg of O{sub 2} consumed per {mu}g chlorophyll a and carbonaceous BOD was 0.20 per {mu}g chlorophyll a in excess of background BOD. The results were similar for live and dead algae. Phytoplankton respiration was fractionated from nonphytoplankton oxygen consumption (NPOC) by the regression of respiration against chlorophyll a to obtain a y intercept of zero chlorophyll. The intercepts, NPOC, closely matched O{sub 2} consumption measured when phytoplankton biomass was very low. Phytoplankton respiration, calculated as the residual of the difference between TCOC and NPOC,ranged from 0.2 to 1.5 (mean = 0.88) mg O{sub 2} per mg chlorophyll a per hour, close to the literature value of 1 (in cultures). Depth-integrated (DI) phytoplankton respiration was 1/4 to 1/3 of DI gross primary productivity and 1-3% of maximum primary productivity. The separation of phytoplankton R and NPOC permitted the demonstration that R probably is not a simple function of productivity.

  14. Marine biogeochemistry: Phytoplankton in a witch's brew

    NASA Astrophysics Data System (ADS)

    Behrenfeld, Michael

    2016-03-01

    Natural seafloor hydrocarbon seeps are responsible for roughly half of the oil released into the ocean. As these oils and gases rise to the surface, they transport nutrients upwards, benefiting phytoplankton in the upper sunlit layer.

  15. Determining the Population Size of Pond Phytoplankton.

    ERIC Educational Resources Information Center

    Hummer, Paul J.

    1980-01-01

    Discusses methods for determining the population size of pond phytoplankton, including water sampling techniques, laboratory analysis of samples, and additional studies worthy of investigation in class or as individual projects. (CS)

  16. Phytoplankton bloom along the coast of Namibia

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This MODIS true-color image, acquired March 4, 2002, shows a phytoplankton bloom along the coast of Namibia. Phytoplankton is a microscopic organism that utilizes chlorophyll, which sunlight reflects off of to create this intense blue-green color in the water. Also prominent in this image is the Skeleton Coast Game Park, which runs along Namibia's northern coast and here glows a beautiful coral-orange color.

  17. Challenges Experienced by Rural Women in India Living with AIDS and Implications for the Delivery of HIV/AIDS Care

    PubMed Central

    Nyamathi, Adeline M.; Sinha, Sanjeev; Ganguly, Kalyan K.; William, Ravi Raj; Heravian, Anisa; Ramakrishnan, Padma; Greengold, Barbara; Ekstrand, Maria; Rao, Pantangi Venkata Rama

    2012-01-01

    Researchers explored the barriers to AIDS care for rural women living with AIDS, and investigated alternative delivery models to increase the women’s adherence to anti-retroviral therapy. Community-based participatory research focus groups were conducted by the researchers with a convenience sample of 39 women living with AIDS from a Primary Health Center near Chennai, India and with nurses, physicians and Accredited Social Health Activists (Ashas), lay health care workers. The most prevalent barriers expressed by the women were sickness-related, psychological, financial issues with childcare, and distance and/or transportation to the site. Women living with AIDS reviewed Ashas favorably. PMID:21409663

  18. Determination of phytoplankton composition using absorption spectra.

    PubMed

    Martínez-Guijarro, R; Romero, I; Pachés, M; Del Río, J G; Martí, C M; Gil, G; Ferrer-Riquelme, A; Ferrer, J

    2009-05-15

    Characterisation of phytoplankton communities in aquatic ecosystems is a costly task in terms of time, material and human resources. The general objective of this paper is not to replace microscopic counts but to complement them, by fine-tuning a technique using absorption spectra measurements that reduces the above-mentioned costs. Therefore, the objective proposed in this paper is to assess the possibility of achieving a qualitative determination of phytoplankton communities by classes, and also a quantitative estimation of the number of phytoplankton cells within each of these classes, using spectrophotometric determination. Samples were taken in three areas of the Spanish Mediterranean coast. These areas correspond to estuary systems that are influenced by both continental waters and Mediterranean Sea waters. 139 Samples were taken in 7-8 stations per area, at different depths in each station. In each sample, the absorption spectrum and the phytoplankton classes (Bacyllariophyceae (diatoms), Cryptophyceae, Clorophyceae, Chrysophyceae, Prasynophyceae, Prymnesophyceae, Euglenophyceae, Cyanophyceae, Dynophyceae and the Synechococcus sp.) were determined. Data were analysed by means of the Partial Least Squares (PLS) multivariate statistical technique. The absorbances obtained between 400 and 750 nm were used as the independent variable and the cell/l of each phytoplankton class was used as the dependent variable, thereby obtaining models which relate the absorbance of the sample extract to the phytoplankton present in it. Good results were obtained for diatoms (Bacillarophyceae), Chlorophyceae and Cryptophyceae. PMID:19269434

  19. Copper sensitivity of Oregon coastal phytoplankton

    SciTech Connect

    Riedel, G.F.

    1983-01-01

    The copper sensitivity of natural populations of Oregon coastal phytoplankton was studied using both additions of ionic copper and Cu-TRIS free ion activity buffers in coastal seawater. Phytoplankton growth rate, taxonomic composition and copper content were examined in treatment additions. The growth rate results suggested that the deficiency of another trace metal increased the apparent toxicity of copper to phytoplankton, especially in TRIS-free ion activity buffered seawater. Laboratory experiments with isolated coastal phytoplankton species indicated that manganese deficiency exacerbated copper toxicity, and that manganese deficiency was induced in TRIS buffered seawater by a TRIS-catalyzed oxidation of Mn. When manganese additions to natural populations were employed inconjunction with ionic copper additions and TRIS-free ion regulated seawater, they showed that ambient manganese concentrations were low enough to shift the onset of copper toxicity to lower copper concentrations. The results suggest that while acute toxicity to phytoplankton by ambient concentrations of copper is unlikely, the interactions of copper and other metals, especially manganese, may influence natural coastal phytoplankton populations in more subtle ways, such as taxonomic composition.

  20. Nearshore phytoplankton of Hammond Bay, Lake Huron

    USGS Publications Warehouse

    Brown, Charles L.; Manny, Bruce A.

    1983-01-01

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

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

    PubMed

    Street, Joseph H; Paytan, Adina

    2005-01-01

    Iron is an essential nutrient for all living organisms. Iron is required for the synthesis of chlorophyll and of several photosynthetic electron transport proteins and for the reduction of CO2, SO4(2-), and NO3(-) during the photosynthetic production of organic compounds. Iron concentrations in vast areas of the ocean are very low (<1 nM) due to the low solubility of iron in oxic seawater. Low iron concentrations have been shown to limit primary production rates, biomass accumulation, and ecosystem structure in a variety of open-ocean environments, including the equatorial Pacific, the subarctic Pacific and the Southern Ocean and even in some coastal areas. Oceanic primary production, the transfer of carbon dioxide into organic carbon by photosynthetic plankton (phytoplankton), is one process by which atmospheric CO2 can be transferred to the deep ocean and sequestered for long periods of time. Accordingly, iron limitation of primary producers likely plays a major role in the global carbon cycle. It has been suggested that variations in oceanic primary productivity, spurred by changes in the deposition of iron in atmospheric dust, control atmospheric CO2 concentrations, and hence global climate, over glacial-interglacial timescales. A contemporary application of this "iron hypothesis" promotes the large-scale iron fertilization of ocean regions as a means of enhancing the ability of the ocean to store anthropogenic CO2 and mitigate 21st century climate change. Recent in situ iron enrichment experiments in the HNLC regions, however, cast doubt on the efficacy and advisability of iron fertilization schemes. The experiments have confirmed the role of iron in regulating primary productivity, but resulted in only small carbon export fluxes to the depths necessary for long-term sequestration. Above all, these experiments and other studies of iron biogeochemistry over the last two decades have begun to illustrate the great complexity of the ocean system. Attempts to

  2. Prevalence of Sexually Transmitted Co-Infections in People Living with HIV/AIDS: Systematic Review with Implications for using HIV Treatments for Prevention

    PubMed Central

    Kalichman, Seth C.; Pellowski, Jennifer; Turner, Christina

    2015-01-01

    Background Sexually transmitted co-infections increase HIV infectiousness through local inflammatory processes. The prevalence of STI among people living with HIV/AIDS has implications for containing the spread of HIV in general and the effectiveness of HIV treatments for prevention in particular. Methods A systematic review of studies examining STI co-infections in people living with HIV/AIDS. The review focuses on STI contracted after becoming HIV infected. Electronic database and manual searches located clinical and epidemiological studies of STI that increase HIV infectiousness. Results Thirty seven studies of STI-HIV co-infection prevalence were located. Studies of adults living with HIV/AIDS from developed and developing countries reported STI rates for 46 different samples (33 samples had clinical/laboratory confirmed STI). The overall mean point-prevalence for confirmed STI was16.3% (SD = 16.4), and median 12.4% STI prevalence in people living with HIV/AIDS. The most common STI studied were Syphilis with median 9.5% prevalence, gonorrhea 9.5%, Chlamydia 5%, and Trichamoniasis 18.8% prevalence. STI prevalence was greatest at the time of HIV diagnosis, reflecting the role of STI in HIV transmission. Prevalence of STI among individuals receiving HIV treatment was not appreciably different from untreated persons. Conclusions The prevalence of STI in people infected with HIV suggests that STI co-infections could undermine efforts to use HIV treatments for prevention by increasing genital secretion infectiousness. PMID:21330572

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

    PubMed

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

    2014-11-18

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

  4. Targeted metagenomics and ecology of globally important uncultured eukaryotic phytoplankton.

    PubMed

    Cuvelier, Marie L; Allen, Andrew E; Monier, Adam; McCrow, John P; Messié, Monique; Tringe, Susannah G; Woyke, Tanja; Welsh, Rory M; Ishoey, Thomas; Lee, Jae-Hyeok; Binder, Brian J; DuPont, Chris L; Latasa, Mikel; Guigand, Cédric; Buck, Kurt R; Hilton, Jason; Thiagarajan, Mathangi; Caler, Elisabet; Read, Betsy; Lasken, Roger S; Chavez, Francisco P; Worden, Alexandra Z

    2010-08-17

    Among eukaryotes, four major phytoplankton lineages are responsible for marine photosynthesis; prymnesiophytes, alveolates, stramenopiles, and prasinophytes. Contributions by individual taxa, however, are not well known, and genomes have been analyzed from only the latter two lineages. Tiny "picoplanktonic" members of the prymnesiophyte lineage have long been inferred to be ecologically important but remain poorly characterized. Here, we examine pico-prymnesiophyte evolutionary history and ecology using cultivation-independent methods. 18S rRNA gene analysis showed pico-prymnesiophytes belonged to broadly distributed uncultivated taxa. Therefore, we used targeted metagenomics to analyze uncultured pico-prymnesiophytes sorted by flow cytometry from subtropical North Atlantic waters. The data reveal a composite nuclear-encoded gene repertoire with strong green-lineage affiliations, which contrasts with the evolutionary history indicated by the plastid genome. Measured pico-prymnesiophyte growth rates were rapid in this region, resulting in primary production contributions similar to the cyanobacterium Prochlorococcus. On average, pico-prymnesiophytes formed 25% of global picophytoplankton biomass, with differing contributions in five biogeographical provinces spanning tropical to subpolar systems. Elements likely contributing to success include high gene density and genes potentially involved in defense and nutrient uptake. Our findings have implications reaching beyond pico-prymnesiophytes, to the prasinophytes and stramenopiles. For example, prevalence of putative Ni-containing superoxide dismutases (SODs), instead of Fe-containing SODs, seems to be a common adaptation among eukaryotic phytoplankton for reducing Fe quotas in low-Fe modern oceans. Moreover, highly mosaic gene repertoires, although compositionally distinct for each major eukaryotic lineage, now seem to be an underlying facet of successful marine phytoplankton. PMID:20668244

  5. Targeted metagenomics and ecology of globally important uncultured eukaryotic phytoplankton

    PubMed Central

    Cuvelier, Marie L.; Allen, Andrew E.; Monier, Adam; McCrow, John P.; Messié, Monique; Tringe, Susannah G.; Woyke, Tanja; Welsh, Rory M.; Ishoey, Thomas; Lee, Jae-Hyeok; Binder, Brian J.; DuPont, Chris L.; Latasa, Mikel; Guigand, Cédric; Buck, Kurt R.; Hilton, Jason; Thiagarajan, Mathangi; Caler, Elisabet; Read, Betsy; Lasken, Roger S.; Chavez, Francisco P.; Worden, Alexandra Z.

    2010-01-01

    Among eukaryotes, four major phytoplankton lineages are responsible for marine photosynthesis; prymnesiophytes, alveolates, stramenopiles, and prasinophytes. Contributions by individual taxa, however, are not well known, and genomes have been analyzed from only the latter two lineages. Tiny “picoplanktonic” members of the prymnesiophyte lineage have long been inferred to be ecologically important but remain poorly characterized. Here, we examine pico-prymnesiophyte evolutionary history and ecology using cultivation-independent methods. 18S rRNA gene analysis showed pico-prymnesiophytes belonged to broadly distributed uncultivated taxa. Therefore, we used targeted metagenomics to analyze uncultured pico-prymnesiophytes sorted by flow cytometry from subtropical North Atlantic waters. The data reveal a composite nuclear-encoded gene repertoire with strong green-lineage affiliations, which contrasts with the evolutionary history indicated by the plastid genome. Measured pico-prymnesiophyte growth rates were rapid in this region, resulting in primary production contributions similar to the cyanobacterium Prochlorococcus. On average, pico-prymnesiophytes formed 25% of global picophytoplankton biomass, with differing contributions in five biogeographical provinces spanning tropical to subpolar systems. Elements likely contributing to success include high gene density and genes potentially involved in defense and nutrient uptake. Our findings have implications reaching beyond pico-prymnesiophytes, to the prasinophytes and stramenopiles. For example, prevalence of putative Ni-containing superoxide dismutases (SODs), instead of Fe-containing SODs, seems to be a common adaptation among eukaryotic phytoplankton for reducing Fe quotas in low-Fe modern oceans. Moreover, highly mosaic gene repertoires, although compositionally distinct for each major eukaryotic lineage, now seem to be an underlying facet of successful marine phytoplankton. PMID:20668244

  6. "Social jetlag" in morning-type college students living on campus: implications for physical and psychological well-being.

    PubMed

    Lau, Esther Yuet Ying; Wong, Mark Lawrence; Ng, Eddie Chi Wai; Hui, Chi-chiu Harry; Cheung, Shu Fai; Mok, Doris Shui Ying

    2013-08-01

    Although on-campus residence allows easier access to campus facilities, existing studies showed mixed results regarding the relationship between college residence and students' well-being indicators, such as sleep behaviors and mood. There was also a lack of studies investigating the role of chronotype in the relationship between on-campus residence and well-being. In particular, the temporal relationships among these factors were unclear. Hence, this longitudinal study aims to fill in these gaps by first reporting the well-being (measured in terms of mood, sleep, and quality of life) among students living on and off campus across two academic semesters. We explored factors predicting students' dropout in university residences. Although students living on campus differ in their chronotypes, activities in campus residence (if any) are mostly scheduled in the nighttime. We therefore tested if individual differences in chronotype interact with campus residence in affecting well-being. Our final sample consisted of 215 campus residents and 924 off-campus-living students from 10 different universities or colleges in Hong Kong or Macau. Their mean age was 20.2 years (SD=2.3); 6.5% of the participants are female. Participants completed self-reported questionnaires online on their sleep duration, sleep quality, chronotype, mood, and physical and psychological quality of life. Across two academic semesters, we assessed if students living on and off campus differed in our well-being measures after we partialed out the effects of demographic information (including age, sex, family income, and parents' education) and the well-being measures at baseline (T1). The results showed that, campus residents exhibited longer sleep duration, greater sleep efficiency, better sleep quality, and less feeling of stress than off-campus-living students. From one semester to the next, around 10% of campus residents did not continue to live on campus. Logistic regression showed that a morning

  7. The influence of the Indian Ocean Dipole on interannual variations in phytoplankton size structure as revealed by Earth Observation

    NASA Astrophysics Data System (ADS)

    Brewin, Robert J. W.; Hirata, Takafumi; Hardman-Mountford, Nick J.; Lavender, Samantha J.; Sathyendranath, Shubha; Barlow, Ray

    2012-11-01

    Using a decade of satellite ocean-colour observations and a model that links chlorophyll-a to the size of the phytoplankton cells, parameterised using pigment data from the Indian Ocean, we examine the implications of the Indian Ocean Dipole (IOD) for phytoplankton size structure. The inferred interannual anomalies in phytoplankton size structure are related to those in sea-surface temperature (SST) and sea-surface height (SSH), derived using satellite radiometry and altimetry, and stratification, derived using the Simple Ocean Data Assimilation (SODA) database. In regions influenced by the Indian Ocean Dipole, we observe a tight correlation between phytoplankton size structure and the physical variables, such that interannual variations in the physical variables accounts for up to 70% of the total variance in phytoplankton size structure. For much of the Indian Ocean, low temperature, low SSH and low stratification (indicative of a turbulent environment) are correlated with larger size classes, consistent with theories on coupling between physical-chemical processes and ecosystem structure. To the extent that phytoplankton function is related to its size structure, changes in physical forcing are likely to influence biogeochemical cycles in the region and the pelagic food web. The limitations of our approach are discussed and we highlight future challenges in satellite ocean-colour monitoring, should climate change lead to any modification in our marine ecosystem.

  8. Influence of vitamin B auxotrophy on nitrogen metabolism in eukaryotic phytoplankton

    PubMed Central

    Bertrand, Erin M.; Allen, Andrew E.

    2012-01-01

    While nitrogen availability is known to limit primary production in large parts of the ocean, vitamin starvation amongst eukaryotic phytoplankton is becoming increasingly recognized as an oceanographically relevant phenomenon. Cobalamin (B12) and thiamine (B1) auxotrophy are widespread throughout eukaryotic phytoplankton, with over 50% of cultured isolates requiring B12 and 20% requiring B1. The frequency of vitamin auxotrophy in harmful algal bloom species is even higher. Instances of colimitation between nitrogen and B vitamins have been observed in marine environments, and interactions between these nutrients have been shown to impact phytoplankton species composition. This review surveys available data, including relevant gene expression patterns, to evaluate the potential for interactive effects of nitrogen and vitamin B12 and B1 starvation in eukaryotic phytoplankton. B12 plays essential roles in amino acid and one-carbon metabolism, while B1 is important for primary carbohydrate and amino acid metabolism and likely useful as an anti-oxidant. Here we will focus on three potential metabolic interconnections between vitamin, nitrogen, and sulfur metabolism that may have ramifications for the role of vitamin and nitrogen scarcities in driving ocean productivity and species composition. These include: (1) B12, B1, and N starvation impacts on osmolyte and antioxidant production, (2) B12 and B1 starvation impacts on polyamine biosynthesis, and (3) influence of B12 and B1 starvation on the diatom urea cycle and amino acid recycling through impacts on the citric acid cycle. We evaluate evidence for these interconnections and identify oceanographic contexts in which each may impact rates of primary production and phytoplankton community composition. Major implications include that B12 and B1 deprivation may impair the ability of phytoplankton to recover from nitrogen starvation and that changes in vitamin and nitrogen availability may synergistically impact harmful

  9. Astaxanthin production in marine pelagic copepods grazing on two different phytoplankton diets

    NASA Astrophysics Data System (ADS)

    Van Nieuwerburgh, Lies; Wänstrand, Ingrid; Liu, Jianguo; Snoeijs, Pauli

    2005-02-01

    The red carotenoid astaxanthin is a powerful natural antioxidant of great importance in aquatic food webs where it is abundant in eggs and body tissues of fish and crustaceans. Little is known about the impact of the phytoplankton diet on astaxanthin production in copepods, its major pelagic producers. We followed the transfer of carotenoids from phytoplankton to copepods in a mesocosm experiment on the northern Atlantic coast (Norway) and recorded the astaxanthin production in copepods. Wild copepods grazed on nutrient-manipulated phytoplankton blooms, which differed in community composition and nutrient status (nitrogen or silicate limitation). The copepod pigments consisted mainly of free astaxanthin and mono- and diesters of astaxanthin. We found no significant difference in astaxanthin production per copepod individual or per unit C depending on the phytoplankton community. However, in the mesocosms astaxanthin per unit C decreased compared with natural levels, probably through a lower demand for photoprotection by the copepods in the dense phytoplankton blooms. The total astaxanthin production per litre was higher in the silicate-limited mesocosms through increased copepod density. Pigment ratio comparisons suggested that the copepod diet here consisted more of diatoms than in the nitrogen-limited mesocosms. Silicate-saturated diatoms were less grazed, possibly because they could invest more in defence mechanisms against their predators. Our study suggests that the production of astaxanthin in aquatic systems can be affected by changes in nutrient dynamics mediated by phytoplankton community composition and copepod population growth. This bottom-up force may have implications for antioxidant protection at higher trophic levels in the food web.

  10. Generalized receptor law governs phototaxis in the phytoplankton Euglena gracilis

    PubMed Central

    Giometto, Andrea; Altermatt, Florian; Maritan, Amos; Stocker, Roman; Rinaldo, Andrea

    2015-01-01

    Phototaxis, the process through which motile organisms direct their swimming toward or away from light, is implicated in key ecological phenomena (including algal blooms and diel vertical migration) that shape the distribution, diversity, and productivity of phytoplankton and thus energy transfer to higher trophic levels in aquatic ecosystems. Phototaxis also finds important applications in biofuel reactors and microbiopropellers and is argued to serve as a benchmark for the study of biological invasions in heterogeneous environments owing to the ease of generating stochastic light fields. Despite its ecological and technological relevance, an experimentally tested, general theoretical model of phototaxis seems unavailable to date. Here, we present accurate measurements of the behavior of the alga Euglena gracilis when exposed to controlled light fields. Analysis of E. gracilis’ phototactic accumulation dynamics over a broad range of light intensities proves that the classic Keller–Segel mathematical framework for taxis provides an accurate description of both positive and negative phototaxis only when phototactic sensitivity is modeled by a generalized “receptor law,” a specific nonlinear response function to light intensity that drives algae toward beneficial light conditions and away from harmful ones. The proposed phototactic model captures the temporal dynamics of both cells’ accumulation toward light sources and their dispersion upon light cessation. The model could thus be of use in integrating models of vertical phytoplankton migrations in marine and freshwater ecosystems, and in the design of bioreactors. PMID:25964338

  11. Generalized receptor law governs phototaxis in the phytoplankton Euglena gracilis.

    PubMed

    Giometto, Andrea; Altermatt, Florian; Maritan, Amos; Stocker, Roman; Rinaldo, Andrea

    2015-06-01

    Phototaxis, the process through which motile organisms direct their swimming toward or away from light, is implicated in key ecological phenomena (including algal blooms and diel vertical migration) that shape the distribution, diversity, and productivity of phytoplankton and thus energy transfer to higher trophic levels in aquatic ecosystems. Phototaxis also finds important applications in biofuel reactors and microbiopropellers and is argued to serve as a benchmark for the study of biological invasions in heterogeneous environments owing to the ease of generating stochastic light fields. Despite its ecological and technological relevance, an experimentally tested, general theoretical model of phototaxis seems unavailable to date. Here, we present accurate measurements of the behavior of the alga Euglena gracilis when exposed to controlled light fields. Analysis of E. gracilis' phototactic accumulation dynamics over a broad range of light intensities proves that the classic Keller-Segel mathematical framework for taxis provides an accurate description of both positive and negative phototaxis only when phototactic sensitivity is modeled by a generalized "receptor law," a specific nonlinear response function to light intensity that drives algae toward beneficial light conditions and away from harmful ones. The proposed phototactic model captures the temporal dynamics of both cells' accumulation toward light sources and their dispersion upon light cessation. The model could thus be of use in integrating models of vertical phytoplankton migrations in marine and freshwater ecosystems, and in the design of bioreactors. PMID:25964338

  12. Host-specificity and dynamics in bacterial communities associated with Bloom-forming freshwater phytoplankton.

    PubMed

    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

  13. Systematic Evaluation of Bioorthogonal Reactions in Live Cells with Clickable HaloTag Ligands: Implications for Intracellular Imaging.

    PubMed

    Murrey, Heather E; Judkins, Joshua C; Am Ende, Christopher W; Ballard, T Eric; Fang, Yinzhi; Riccardi, Keith; Di, Li; Guilmette, Edward R; Schwartz, Joel W; Fox, Joseph M; Johnson, Douglas S

    2015-09-01

    Bioorthogonal reactions, including the strain-promoted azide-alkyne cycloaddition (SPAAC) and inverse electron demand Diels-Alder (iEDDA) reactions, have become increasingly popular for live-cell imaging applications. However, the stability and reactivity of reagents has never been systematically explored in the context of a living cell. Here we report a universal, organelle-targetable system based on HaloTag protein technology for directly comparing bioorthogonal reagent reactivity, specificity, and stability using clickable HaloTag ligands in various subcellular compartments. This system enabled a detailed comparison of the bioorthogonal reactions in live cells and informed the selection of optimal reagents and conditions for live-cell imaging studies. We found that the reaction of sTCO with monosubstituted tetrazines is the fastest reaction in cells; however, both reagents have stability issues. To address this, we introduced a new variant of sTCO, Ag-sTCO, which has much improved stability and can be used directly in cells for rapid bioorthogonal reactions with tetrazines. Utilization of Ag complexes of conformationally strained trans-cyclooctenes should greatly expand their usefulness especially when paired with less reactive, more stable tetrazines. PMID:26270632

  14. Global phytoplankton decline over the past century.

    PubMed

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

    2010-07-29

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

  15. Phytoplankton niche generation by interspecific stoichiometric variation

    NASA Astrophysics Data System (ADS)

    GöThlich, L.; Oschlies, A.

    2012-06-01

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

  16. Phytoplankton Bloom in North Sea off Scotland

    NASA Technical Reports Server (NTRS)

    2008-01-01

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

  17. β -Decay Half-Lives of 110 Neutron-Rich Nuclei across the N =82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process

    NASA Astrophysics Data System (ADS)

    Lorusso, G.; Nishimura, S.; Xu, Z. Y.; Jungclaus, A.; Shimizu, Y.; Simpson, G. S.; Söderström, P.-A.; Watanabe, H.; Browne, F.; Doornenbal, P.; Gey, G.; Jung, H. S.; Meyer, B.; Sumikama, T.; Taprogge, J.; Vajta, Zs.; Wu, J.; Baba, H.; Benzoni, G.; Chae, K. Y.; Crespi, F. C. L.; Fukuda, N.; Gernhäuser, R.; Inabe, N.; Isobe, T.; Kajino, T.; Kameda, D.; Kim, G. D.; Kim, Y.-K.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Lane, G. J.; Li, Z.; Montaner-Pizá, A.; Moschner, K.; Naqvi, F.; Niikura, M.; Nishibata, H.; Odahara, A.; Orlandi, R.; Patel, Z.; Podolyák, Zs.; Sakurai, H.; Schaffner, H.; Schury, P.; Shibagaki, S.; Steiger, K.; Suzuki, H.; Takeda, H.; Wendt, A.; Yagi, A.; Yoshinaga, K.

    2015-05-01

    The β -decay half-lives of 110 neutron-rich isotopes of the elements from Rb 37 to Sn 50 were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for r -process calculations and reinforce the notion that the second (A ≈130 ) and the rare-earth-element (A ≈160 ) abundance peaks may result from the freeze-out of an (n ,γ )⇄(γ ,n ) equilibrium. In such an equilibrium, the new half-lives are important factors determining the abundance of rare-earth elements, and allow for a more reliable discussion of the r process universality. It is anticipated that universality may not extend to the elements Sn, Sb, I, and Cs, making the detection of these elements in metal-poor stars of the utmost importance to determine the exact conditions of individual r -process events.

  18. Phytoplankton Communities in Louisiana coastal waters and the continental shelf

    EPA Science Inventory

    Louisiana coastal waters and the adjacent continental shelf receive large freshwater and nutrient inputs from the Mississippi and Atchafalaya Rivers, creating favorable conditions for increased phytoplankton productivity. To examine inshore-offshore patterns in phytoplankton comm...

  19. Biomarkers of safety and immune protection for genetically modified live attenuated leishmania vaccines against visceral leishmaniasis - discovery and implications.

    PubMed

    Gannavaram, Sreenivas; Dey, Ranadhir; Avishek, Kumar; Selvapandiyan, Angamuthu; Salotra, Poonam; Nakhasi, Hira L

    2014-01-01

    Despite intense efforts there is no safe and efficacious vaccine against visceral leishmaniasis, which is fatal and endemic in many tropical countries. A major shortcoming in the vaccine development against blood-borne parasitic agents such as Leishmania is the inadequate predictive power of the early immune responses mounted in the host against the experimental vaccines. Often immune correlates derived from in-bred animal models do not yield immune markers of protection that can be readily extrapolated to humans. The limited efficacy of vaccines based on DNA, subunit, heat killed parasites has led to the realization that acquisition of durable immunity against the protozoan parasites requires a controlled infection with a live attenuated organism. Recent success of irradiated malaria parasites as a vaccine candidate further strengthens this approach to vaccination. We developed several gene deletion mutants in Leishmania donovani as potential live attenuated vaccines and reported extensively on the immunogenicity of LdCentrin1 deleted mutant in mice, hamsters, and dogs. Additional limited studies using genetically modified live attenuated Leishmania parasites as vaccine candidates have been reported. However, for the live attenuated parasite vaccines, the primary barrier against widespread use remains the absence of clear biomarkers associated with protection and safety. Recent studies in evaluation of vaccines, e.g., influenza and yellow fever vaccines, using systems biology tools demonstrated the power of such strategies in understanding the immunological mechanisms that underpin a protective phenotype. Applying similar tools in isolated human tissues such as PBMCs from healthy individuals infected with live attenuated parasites such as LdCen(-/-) in vitro followed by human microarray hybridization experiments will enable us to understand how early vaccine-induced gene expression profiles and the associated immune responses are coordinately regulated in normal

  20. Biomarkers of Safety and Immune Protection for Genetically Modified Live Attenuated Leishmania Vaccines Against Visceral Leishmaniasis – Discovery and Implications

    PubMed Central

    Gannavaram, Sreenivas; Dey, Ranadhir; Avishek, Kumar; Selvapandiyan, Angamuthu; Salotra, Poonam; Nakhasi, Hira L.

    2014-01-01

    Despite intense efforts there is no safe and efficacious vaccine against visceral leishmaniasis, which is fatal and endemic in many tropical countries. A major shortcoming in the vaccine development against blood-borne parasitic agents such as Leishmania is the inadequate predictive power of the early immune responses mounted in the host against the experimental vaccines. Often immune correlates derived from in-bred animal models do not yield immune markers of protection that can be readily extrapolated to humans. The limited efficacy of vaccines based on DNA, subunit, heat killed parasites has led to the realization that acquisition of durable immunity against the protozoan parasites requires a controlled infection with a live attenuated organism. Recent success of irradiated malaria parasites as a vaccine candidate further strengthens this approach to vaccination. We developed several gene deletion mutants in Leishmania donovani as potential live attenuated vaccines and reported extensively on the immunogenicity of LdCentrin1 deleted mutant in mice, hamsters, and dogs. Additional limited studies using genetically modified live attenuated Leishmania parasites as vaccine candidates have been reported. However, for the live attenuated parasite vaccines, the primary barrier against widespread use remains the absence of clear biomarkers associated with protection and safety. Recent studies in evaluation of vaccines, e.g., influenza and yellow fever vaccines, using systems biology tools demonstrated the power of such strategies in understanding the immunological mechanisms that underpin a protective phenotype. Applying similar tools in isolated human tissues such as PBMCs from healthy individuals infected with live attenuated parasites such as LdCen−/− in vitro followed by human microarray hybridization experiments will enable us to understand how early vaccine-induced gene expression profiles and the associated immune responses are coordinately regulated in normal

  1. The evolution of modern eukaryotic phytoplankton.

    PubMed

    Falkowski, Paul G; Katz, Miriam E; Knoll, Andrew H; Quigg, Antonietta; Raven, John A; Schofield, Oscar; Taylor, F J R

    2004-07-16

    The community structure and ecological function of contemporary marine ecosystems are critically dependent on eukaryotic phytoplankton. Although numerically inferior to cyanobacteria, these organisms are responsible for the majority of the flux of organic matter to higher trophic levels and the ocean interior. Photosynthetic eukaryotes evolved more than 1.5 billion years ago in the Proterozoic oceans. However, it was not until the Mesozoic Era (251 to 65 million years ago) that the three principal phytoplankton clades that would come to dominate the modern seas rose to ecological prominence. In contrast to their pioneering predecessors, the dinoflagellates, coccolithophores, and diatoms all contain plastids derived from an ancestral red alga by secondary symbiosis. Here we examine the geological, geochemical, and biological processes that contributed to the rise of these three, distantly related, phytoplankton groups. PMID:15256663

  2. Microflow Cytometer for optical analysis of phytoplankton.

    PubMed

    Hashemi, Nastaran; Erickson, Jeffrey S; Golden, Joel P; Jackson, Kirsten M; Ligler, Frances S

    2011-07-15

    Analysis of the intrinsic fluorescence profiles of individual marine algae can be used in general classification of organisms based on cell size and fluorescence properties. We describe the design and fabrication of a Microflow Cytometer on a chip for characterization of phytoplankton. The Microflow Cytometer measured distinct side scatter and fluorescence properties of Synechococcus sp., Nitzschia d., and Thalassiosira p.; measurements were confirmed using the benchtop Accuri C6 flow cytometer. The Microflow Cytometer proved sensitive enough to detect and characterize picoplankton with diameter approximately 1 μm and larger phytoplankton of up to 80 μm in length. The wide range in size discrimination coupled with detection of intrinsic fluorescent pigments suggests that this Microflow Cytometer will be able to distinguish different populations of phytoplankton on unmanned underwater vehicles. PMID:21601442

  3. Iron–Nutrient Interactions within Phytoplankton

    PubMed Central

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

    2016-01-01

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

  4. Evolutionary inheritance of elemental stoichiometry in phytoplankton

    PubMed Central

    Quigg, Antonietta; Irwin, Andrew J.; Finkel, Zoe V.

    2011-01-01

    The elemental composition of phytoplankton is a fusion of the evolutionary history of the host and plastid, resulting in differences in genetic constraints and selection pressures associated with environmental conditions. The evolutionary inheritance hypothesis predicts similarities in elemental composition within related taxonomic lineages of phytoplankton. To test this hypothesis, we measured the elemental composition (C, N, P, S, K, Mg, Ca, Sr, Fe, Mn, Zn, Cu, Co, Cd and Mo) of 14 phytoplankton species and combined these with published data from 15 more species from both marine and freshwater environments grown under nutrient-replete conditions. The largest differences in the elemental profiles of the species distinguish between the prokaryotic Cyanophyta and primary endosymbiotic events that resulted in the green and red plastid lineages. Smaller differences in trace element stoichiometry within the red and green plastid lineages are consistent with changes in trace elemental stoichiometry owing to the processes associated with secondary endosymbioses and inheritance by descent with modification. PMID:20826483

  5. Phytoplankton and cloudiness in the Southern Ocean.

    PubMed

    Meskhidze, Nicholas; Nenes, Athanasios

    2006-12-01

    The effect of ocean biological productivity on marine clouds is explored over a large phytoplankton bloom in the Southern Ocean with the use of remotely sensed data. Cloud droplet number concentration over the bloom was twice what it was away from the bloom, and cloud effective radius was reduced by 30%. The resulting change in the short-wave radiative flux at the top of the atmosphere was -15 watts per square meter, comparable to the aerosol indirect effect over highly polluted regions. This observed impact of phytoplankton on clouds is attributed to changes in the size distribution and chemical composition of cloud condensation nuclei. We propose that secondary organic aerosol, formed from the oxidation of phytoplankton-produced isoprene, can affect chemical composition of marine cloud condensation nuclei and influence cloud droplet number. Model simulations support this hypothesis, indicating that 100% of the observed changes in cloud properties can be attributed to the isoprene secondary organic aerosol. PMID:17082422

  6. Iron-Nutrient Interactions within Phytoplankton.

    PubMed

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

    2016-01-01

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

  7. The species concept in phytoplankton ecology

    SciTech Connect

    Wood, A.M.; Leatham, T. )

    1992-12-01

    The authors discuss the broad aspects and difficulties of phytoplankton species identification. Phytoplankton ecology relies heavily on the use of taxon-insensitive indicies like chlorophyll a concentration, [sup 14]C incubations, and light-dark bottles for measurement of abundance and productivity. Numerous excellent studies have been done in comparative algal physiology, but none of them actually demonstrate species level differences in the traits of interest. Many of the studies underestimate genetic diversity within taxa because they rely on genotypes that can be cultured and maintained in the laboratory. Significant interclonal variablity is found every time that strains from the same putative taxon are compared, and the magnitude of these differences is not trivial. The authors follow this discussion by detailing several specific ways of approaching speciation in phytoplankton including identifying the ecological significance of morphological traits and ecologically important traits consistently correlated with mprphological features used to distinguish among speiceis or sub-species. 82 refs., 2 figs., 1 tab.

  8. [Tools for determining health of phytoplankton cells

    SciTech Connect

    Not Available

    1992-12-31

    The primary purpose of the proposed research is to develop molecular tools for determining the health of marine phytoplankton on an individual cell basis. Since the definition of healthy in phytoplankton cells is elusive, we propose to develop markers for several different metabolic processes indicative of physiological state: photosynthetic activity, esterase activity, membrane permeability, and mitochondrial activity. One underlying motivation is to develop methods which will allow us to evaluate the hypothesis that, while healthy cells release very little dissolved organic carbon (DOC), many phytoplankton communities are comprised of unhealthy or physiologically stressed cells which release a large proportion of total photosynthate directly into the pool of labile DOC. This is proposed to be especially true in continental shelf and coastal environments where zones of productivity are patchy and phytoplankton populations adapted to one regime can be easily transported into waters which differ in salinity, nutrient supply, and/or turbidity. The significance of the work, however, extends beyond this immediate goal since there are presently relatively few methods which allow us to estimate the physiological state of phytoplankton cells.When we evaluate population sizes of phytoplankton in the water column or examine fecal pellets, particulate aggregates, or other material, we generally work in ignorance of the activity of the cells except as the average cell-specific activity is estimated from bulk measurements. This approach effectively hides any differences in the relative contribution of different taxa or individuals to overall productivity eventhough most flux processes are sensitive to physiological and taxonomically determined differences among members of the community.

  9. [Tools for determining health of phytoplankton cells

    SciTech Connect

    Not Available

    1992-01-01

    The primary purpose of the proposed research is to develop molecular tools for determining the health of marine phytoplankton on an individual cell basis. Since the definition of healthy in phytoplankton cells is elusive, we propose to develop markers for several different metabolic processes indicative of physiological state: photosynthetic activity, esterase activity, membrane permeability, and mitochondrial activity. One underlying motivation is to develop methods which will allow us to evaluate the hypothesis that, while healthy cells release very little dissolved organic carbon (DOC), many phytoplankton communities are comprised of unhealthy or physiologically stressed cells which release a large proportion of total photosynthate directly into the pool of labile DOC. This is proposed to be especially true in continental shelf and coastal environments where zones of productivity are patchy and phytoplankton populations adapted to one regime can be easily transported into waters which differ in salinity, nutrient supply, and/or turbidity. The significance of the work, however, extends beyond this immediate goal since there are presently relatively few methods which allow us to estimate the physiological state of phytoplankton cells.When we evaluate population sizes of phytoplankton in the water column or examine fecal pellets, particulate aggregates, or other material, we generally work in ignorance of the activity of the cells except as the average cell-specific activity is estimated from bulk measurements. This approach effectively hides any differences in the relative contribution of different taxa or individuals to overall productivity eventhough most flux processes are sensitive to physiological and taxonomically determined differences among members of the community.

  10. The annual cycles of phytoplankton biomass

    USGS Publications Warehouse

    Winder, M.; Cloern, J.E.

    2010-01-01

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

  11. Bivalve grazing can shape phytoplankton communities

    USGS Publications Warehouse

    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.

  12. Mix and match: how climate selects phytoplankton.

    PubMed

    Falkowski, Paul G; Oliver, Matthew J

    2007-10-01

    Climate strongly influences the distribution and diversity of animals and plants, but its affect on microbial communities is poorly understood. By using resource competition theory, fundamental physical principles and the fossil record we review how climate selects marine eukaryotic phytoplankton taxa. We suggest that climate determines the equator-to-pole and continent-to-land thermal gradients that provide energy for the wind-driven turbulent mixing in the upper ocean. This mixing, in turn, controls the nutrient fluxes that determine cell size and taxa-level distributions. Understanding this chain of linked processes will allow informed predictions to be made about how phytoplankton communities will change in the future. PMID:17853908

  13. Production of volatile organohalogens by phytoplankton cultures

    SciTech Connect

    Tokarczyk, R.; Moore, R.M. )

    1994-02-15

    The authors report on laboratory experiments which have demonstrated that types of unialgal cultures of marine phytoplankton can produce a range of halocarbons, including CHBr[sub 3], CHBr[sub 2]Cl, CH[sub 2]Br[sub 2]. In the laboratory environment the production rate is shown to be dependent upon the species of phytoplankton, and the development stage. Such volatile halocarbons, coming from natural sources in the seas, are thought to be important sources of reactive halogens in the troposphere, and perhaps even in the stratosphere, if the compounds are stable enough.

  14. Investigating mechanisms for the variability in phytoplankton assemblages in the northeastern waters of the Philippines

    NASA Astrophysics Data System (ADS)

    Yniguez, A. T.; Camoying, M.; Bollozos, I.; Palermo, J. H.; Villanoy, C. L.

    2013-12-01

    The northeastern side of the Philippines, particularly off of Luzon Island, is strongly influenced by the Pacific Western Boundary current system. The North Equatorial Current bifurcates offshore feeding into the Mindanao current flowing south and the Kuroshio Current that begins to consolidate in the waters off of Luzon. Two cruises were conducted during May/June 2011 and April/May 2012 which showed distinctly different circulation patterns and strengths of water masses. Phytoplankton abundances and composition measurements were obtained using microscopy, as well as through an in situ fluorometer. Analysis of the phytoplankton assemblages from these two cruises showed variability in both space and time. Distinct assemblages could be observed amongst different water masses both in 2011 and 2012. There was also a significant difference in the phytoplankton abundances and composition seen between the two sampling years. Mechanisms such as circulation patterns and related physico-chemical characteristics leading to these spatio-temporal variabilities in phytoplankton concentrations and distributions are explored in this study. These shifts in primary producers and productivity have important implications in this region which is a key fishing area for both municipal and commercial fisheries.

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

    PubMed

    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. PMID:26063527

  16. Boundary influences on HAB phytoplankton ecology in a stratification-enhanced upwelling shadow

    NASA Astrophysics Data System (ADS)

    Ryan, J. P.; McManus, M. A.; Kudela, R. M.; Lara Artigas, M.; Bellingham, J. G.; Chavez, F. P.; Doucette, G.; Foley, D.; Godin, M.; Harvey, J. B. J.; Marin, R.; Messié, M.; Mikulski, C.; Pennington, T.; Py, F.; Rajan, K.; Shulman, I.; Wang, Z.; Zhang, Y.

    2014-03-01

    Coastal marine ecosystems are profoundly influenced by processes that originate from their boundaries. These include fluid boundaries—with the atmosphere, oceanic boundary currents and terrestrial aquatic systems, as well as solid boundaries—with the seafloor and coast. Phytoplankton populations transfer complexly interacting boundary influences into the biosphere. In this contribution, we apply data from an ocean observing and modeling system to examine boundary influences driving phytoplankton ecology in Monterey Bay, CA, USA. The study was focused on species that may cause harmful algal blooms (HABs). During September-October 2010, autonomous molecular analytical devices were moored at two locations characterized by different degrees of stratification and exposure to upwelling dynamics. The time-series revealed multiple transitions in local HAB phytoplankton communities, involving diatoms (Pseudo-nitzschia spp.), dinoflagellates (Alexandrium catenella), and raphidophytes (Heterosigma akashiwo). Observational and model results showed that the biological transitions were closely related to environmental changes that resulted from a variety of boundary processes—responses of oceanic circulation to wind forcing, influxes of different water types that originated outside the bay, and emergence of strongly stratified nearshore water into the greater bay. Boundary processes were further implicated at patch scales. High-resolution mapping and sampling of a phytoplankton-enriched patch were conducted in a Lagrangian framework using autonomous underwater vehicles. These highly resolved measurements showed that small-scale spatial patterns in the toxicity of Pseudo-nitzschia populations were related to the coupling of resuspended sediments from the bottom boundary layer to the surface mixed layer.

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

    NASA Astrophysics Data System (ADS)

    Le Quéré, C.; Buitenhuis, E. T.; Moriarty, R.; Alvain, S.; Aumont, O.; Bopp, L.; Chollet, S.; Enright, C.; Franklin, D. J.; Geider, R. J.; Harrison, S. P.; Hirst, A.; Larsen, S.; Legendre, L.; Platt, T.; Prentice, I. C.; Rivkin, R. B.; Sathyendranath, S.; Stephens, N.; Vogt, M.; Sailley, S.; Vallina, S. M.

    2015-07-01

    Global ocean biogeochemistry models currently employed in climate change projections use highly simplified representations of pelagic food webs. These food webs do not necessarily include critical pathways by which ecosystems interact with ocean biogeochemistry and climate. Here we present a global biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types (PFTs); six types of phytoplankton, three types of zooplankton, and heterotrophic bacteria. We improved the representation of zooplankton dynamics in our model through (a) the explicit inclusion of large, slow-growing zooplankton, and (b) the introduction of trophic cascades among the three zooplankton types. We use the model to quantitatively assess the relative roles of iron vs. grazing in determining phytoplankton biomass in the Southern Ocean High Nutrient Low Chlorophyll (HNLC) region during summer. When model simulations do not represent crustacean macrozooplankton grazing, they systematically overestimate Southern Ocean chlorophyll biomass during the summer, even when there was no iron deposition from dust. When model simulations included the developments of the zooplankton component, the simulation of phytoplankton biomass improved and the high chlorophyll summer bias in the Southern Ocean HNLC region largely disappeared. Our model results suggest that the observed low phytoplankton biomass in the Southern Ocean during summer is primarily explained by the dynamics of the Southern Ocean zooplankton community rather than iron limitation. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean.

  18. Stable Carbon Isotope Constraints on the Timing and Magnitude of Phytoplankton Blooms in San Francisco Bay

    NASA Astrophysics Data System (ADS)

    Goodwin, D.; Roopnarine, P. D.

    2010-12-01

    Recent work on phytoplankton dynamics in San Francisco Bay (SFB) revealed new seasonal blooms. Historic observations (1978-1998) of chlorophyll a (Chl a) showed an annual pattern of short-lived spring blooms. In 1999, this pattern changed with the appearance of autumnal blooms in addition to the characteristic large vernal blooms. This change was attributed to decreases in bivalve mollusk populations concurrent with increases in macro invertebrate and vertebrate mollusk predators. Previous work, however, suggests that inter-annual variation in phytoplankton biomass is a function of river discharge. These observations suggest phytoplankton abundances in SFB reflect multiple forcing mechanisms and underscore the importance of understanding prehistoric variations in bloom dynamics. Here, we present stable isotope data from the exotic oyster Crassostrea gigas, which record the timing and magnitude of past phytoplankton blooms. These data may be useful for identifying patterns of phytoplankton bloom dynamics prior to instrumental observations. Stable oxygen (δ18O) and carbon (δ13C) isotope profiles from recent live-collected (2006) specimens of the oyster C. gigas collected in southern SFB were analyzed in conjunction with in situ records of environmental variability (water temperature and δ18Owater calculated from salinity). Their observed δ18Ocarb profiles are characterized by several unique features that correlate with predicted δ18Ocarb values calculated from water temperature and δ18Owater measurements indicating that these oysters were recruited at the end of 2001 or early in 2002. A prominent 1-2 ‰ spike characterizes the carbon isotope profile from each of these specimens. These positive excursions most likely reflect a large phytoplankton bloom, during which algae preferentially assimilated 12C, resulting in the enrichment of 13C in the dissolved inorganic carbon (DIC) of seawater. Furthermore, phytoplankton blooms may appear as positive spikes in a

  19. Temperature-sensitive mutations for live-attenuated Rift Valley fever vaccines: implications from other RNA viruses

    PubMed Central

    Nishiyama, Shoko; Ikegami, Tetsuro

    2015-01-01

    Rift Valley fever (RVF) is a mosquito-borne zoonotic disease endemic to the African continent. RVF is characterized by high rate of abortions in ruminants and hemorrhagic fever, encephalitis, or blindness in humans. RVF is caused by the Rift Valley fever virus (RVFV: genus Phlebovirus, family Bunyaviridae). Vaccination is the only known effective strategy to prevent the disease, but there are no licensed RVF vaccines available for humans. A live-attenuated vaccine candidate derived from the wild-type pathogenic Egyptian ZH548 strain, MP-12, has been conditionally licensed for veterinary use in the U.S. MP-12 displays a temperature-sensitive (ts) phenotype and does not replicate at 41°C. The ts mutation limits viral replication at a specific body temperature and may lead to an attenuation of the virus. Here we will review well-characterized ts mutations for RNA viruses, and further discuss the potential in designing novel live-attenuated vaccines for RVF. PMID:26322023

  20. Using phytoplankton`s fluorescence for remote detection of radioactive pollutions in the ocean

    SciTech Connect

    Tsipenyuk, D.Yu.

    1996-08-01

    One of important ecological problems of our world is unfortunately radioactive pollutions in the ocean from sources of different types. For successful solving this problem it is important to locate precisely pollution areas using remote sensing methods. In the experiments performed we investigated the changes in fluorescence spectra of phytoplankton under an action of radiation. For this purpose we compared fluorescence spectra of samples of phytoplankton`s that were grown and maintained under the same conditions (light temperature, etc.) and the only difference between these samples was different radioactive doze obtained. Gamma irradiations of the samples was performed by bremsstrahlung of 30 Mev electrons or gamma-rays from (Ra-Be)- neutron source. To obtain reliable quantitative results the samples were simultaneously irradiated at different distances from the bremsstrahlung target or radioactive source. In such a way we could avoid possible errors due to different state of phytoplankton and temporal changes of gamma-radiation. The fluorescence spectra of phytoplankton were exited with a nitrogen laser emitting at 337 nm. An optical system focused fluorescence onto the entry slit of the polychromator of optical multichannel spectrum analyzer. A diffraction grating with a relatively weak dispersion (150 lines/mm) was used to record simultaneously spectra in a rather wide range of wavelengths (370-720 nm). We found in our experiments that very characteristic changes were relevant in fluorescence spectra of phytoplankton under radioactive influence in registered range of wavelength. Thus it is possible to use active and passive remote sensing methods of registration of phytoplankton`s fluorescence for express remote location areas of radioactive pollutions in the ocean from satellites or aircrafts.

  1. Remote sensing of phytoplankton using laser-induced fluorescence

    SciTech Connect

    Babichenko, S.; Poryvkina, L.; Arikese, V. ); Kaitala, S. ); Kuosa, H. )

    1993-06-01

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

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

    ERIC Educational Resources Information Center

    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…

  3. DISTRIBUTION OF PHYTOPLANKTON IN TEXAS LAKES

    EPA Science Inventory

    This is a data report presenting the species and abundance of phytoplankton in the 38 lakes sampled by the National Eutrophication Survey in the State of Texas. Results from the calculation of several water quality indices are also included (Nygaard's Trophic State Index, Palmer'...

  4. Revisiting subsurface chlorophyll and phytoplankton distributions

    NASA Astrophysics Data System (ADS)

    Hense, I.; Beckmann, A.

    2008-09-01

    Vertical profiles of chlorophyll concentration and phytoplankton biomass at ALOHA (HOT) are analyzed for the time period 1988 to 2004. Two different methods are applied: in the standard approach the data are averaged over depth horizons and in the alternative approach the profiles are shifted to the depth of the deepest subsurface maximum before averaging. The results show that the latter is the only meaningful way to look at vertical distribution patterns of both chlorophyll and phytoplankton in the oligotrophic ocean. In particular, a pronounced subsurface maximum of phytoplankton biomass appears only if this depth-adjustment method is used. Otherwise the vertical displacement of the subsurface biomass due to changes in the subsurface light field masks the actual signal: the thickness of the subsurface maximum is overestimated and the maximum is reduced. The results of this study have far-reaching consequences for the interpretation of the large number of profiles of chlorophyll and phytoplankton in the oligotrophic ocean. The absence of a subsurface biomass maximum might not be necessarily a result of photoacclimation but of inadequate analyses combined with coarse vertical resolution.

  5. Phytoplankton off the West Coast of Africa

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Just off the coast of West Africa, persistent northeasterly trade winds often churn up deep ocean water. When the nutrients in these deep waters reach the ocean's surface, they often give rise to large blooms of phytoplankton. This image of the Mauritanian coast shows swirls of phytoplankton fed by the upwelling of nutrient-rich water. The scene was acquired by the Medium Resolution Imaging Spectrometer (MERIS) aboard the European Space Agency's ENVISAT. MERIS will monitor changes in phytoplankton across Earth's oceans and seas, both for the purpose of managing fisheries and conducting global change research. NASA scientists will use data from this European instrument in the Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) program. The mission of SIMBIOS is to construct a consistent long-term dataset of ocean color (phytoplankton abundance) measurements made by multiple satellite instruments, including the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and the Moderate-Resolution Imaging Spectroradiometer (MODIS). For more information about MERIS and ENVISAT, visit the ENVISAT home page. Image copyright European Space Agency

  6. Phytoplankton and sediments in Gulf of Mexico

    NASA Technical Reports Server (NTRS)

    2002-01-01

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

  7. The dynamical landscape of marine phytoplankton diversity.

    PubMed

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

    2015-10-01

    Observations suggest that the landscape of marine phytoplankton assemblage might be strongly heterogeneous at the dynamical mesoscale and submesoscale (10-100 km, days to months), with potential consequences in terms of global diversity and carbon export. But these variations are not well documented as synoptic taxonomic data are difficult to acquire. Here, we examine how phytoplankton assemblage and diversity vary between mesoscale eddies and submesoscale fronts. We use a multi-phytoplankton numerical model embedded in a mesoscale flow representative of the North Atlantic. Our model results suggest that the mesoscale flow dynamically distorts the niches predefined by environmental contrasts at the basin scale and that the phytoplankton diversity landscape varies over temporal and spatial scales that are one order of magnitude smaller than those of the basin-scale environmental conditions. We find that any assemblage and any level of diversity can occur in eddies and fronts. However, on a statistical level, the results suggest a tendency for larger diversity and more fast-growing types at fronts, where nutrient supplies are larger and where populations of adjacent water masses are constantly brought into contact; and lower diversity in the core of eddies, where water masses are kept isolated long enough to enable competitive exclusion. PMID:26400196

  8. Programmed Cell Death in Unicellular Phytoplankton.

    PubMed

    Bidle, Kay D

    2016-07-11

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

  9. Color Difference in Bering Sea Phytoplankton Blooms

    NASA Technical Reports Server (NTRS)

    2002-01-01

    There is considerable color variation in the phytoplankton blooms in the Bering Sea -- from the aquamarine west of Nunivak Island to the almost reddish patch west of St. Matthew Island to the green eddy astride the International dateline at 60 North latitude and 178 East longitude. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  10. Phytoplankton in the northwestern Kara Sea

    NASA Astrophysics Data System (ADS)

    Sukhanova, I. N.; Flint, M. V.; Druzhkova, E. I.; Sazhin, A. F.; Sergeeva, V. M.

    2015-07-01

    Studies were conducted in the northwestern Kara Sea in late September of 2007 and 2011. The assessment of species, size, structure, abundance, and biomass of phytoplankton and the role of autotrophic and heterotrophic components in phytocenoses was conducted. The abundance of autotrophic micro-, nanoand picoplankton increased by more than an order of magnitude in each of the following smaller-sized groups of algae. Microphytoplankton dominated in the total biomass of autotrophic phytoplankton. The wet biomass of microphytoplankton was 2.5 times higher than the wet biomass of nanophytoplankton and 5 times higher than that of picoplankton. Nanophytoplankton dominated in abundance and biomass in the heterotrophic component of phytoplankton. The ratio of the total abundance of autotrophic and heterotrophic phytotoplankton was 7: 1, the ratio of the wet biomass of the both groups was 2.5: 1, and the proportion of the carbon biomass was 2: 1. Three biotopes were distinguished in the area of the outer shelf, the continental slope, and the deepwater area adjacent to the St. Anna Trough, which differed in composition and quantitative characteristics of phytocenoses. Frontal zones dividing the biotopes are characterized by high phytoplankton biomass and the dominance of diatoms in the community (more than 40% of the total biomass), which indicates the local availability of "new" nutrients for planktonic algae.

  11. Production of isoprene by marine phytoplankton cultures

    SciTech Connect

    Moore, R.M.; Oram, D.E.; Penkett, S.A.

    1994-11-15

    The authors report experiments which demonstrate the production of light volatile hydrocarbons, including isoprene, by different marine phytoplankton cultures. This indicates that the ocean is a potential source of natural releases of isoprene to the atmosphere. Laboratory results do not allow extrapolation to atmospheric release rates.

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

    PubMed Central

    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. PMID:27196376

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

    PubMed

    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. PMID:27196376

  14. Temperature influence on phytoplankton community growth rates

    NASA Astrophysics Data System (ADS)

    Sherman, Elliot; Moore, J. Keith; Primeau, Francois; Tanouye, David

    2016-04-01

    A large database of field estimates of phytoplankton community growth rates in natural populations was compiled and analyzed to determine the apparent temperature effect on phytoplankton community growth rate. We conducted an ordinary least squares regression to optimize the parameters in two commonly used growth-temperature relations (Arrhenius and Q10 models). Both equations fit the observational data equally with the optimized parameter values. The optimum apparent Q10 value was 1.47 ± 0.08 (95% confidence interval, CI). Microzooplankton grazing rates closely matched the temperature trends for phytoplankton growth. This likely reflects a dynamic adjustment of biomass and grazing rates by the microzooplankton to match their available food source, illustrating tight coupling of phytoplankton growth and microzooplankton grazing rates. The field-measured temperature effect and growth rates were compared with estimates from the satellite Carbon-based Productivity Model (CbPM) and three Earth System Models (ESMs), with model output extracted at the same month and sampling locations as the observations. The optimized, apparent Q10 value calculated for the CbPM was 1.51, with overestimation of growth rates. The apparent Q10 value in the Community Earth System Model (V1.0) was 1.65, with modest underestimation of growth rates. The GFDL-ESM2M and GFDL-ESM2G models produced apparent Q10 values of 1.52 and 1.39, respectively. Models with an apparent Q10 that is significantly greater than ~1.5 will overestimate the phytoplankton community growth response to the ongoing climate warming and will have spatial biases in estimated growth rates for the current era.

  15. Genetic characteristics of Neisseria meningitidis serogroup B strains carried by adolescents living in Milan, Italy: implications for vaccine efficacy.

    PubMed

    Esposito, Susanna; Zampiero, Alberto; Terranova, Leonardo; Montinaro, Valentina; Scala, Alessia; Ansuini, Valentina; Principi, Nicola

    2013-11-01

    Before a protein vaccine is introduced into a country, it is essential to evaluate its potential impact and estimate its benefits and costs. The aim of this study was to determine the genetic characteristics of Neisseria meningitidis B (NmB) in the pharyngeal secretions of 1375 healthy adolescents aged 13-19 y living in Milan, Italy, in September 2012, and the possible protection offered by the two currently available NmB protein vaccines. Ninety-one subjects were Nm carriers (6.6%), 29 (31.9%) of whom carried the NmB capsular gene. The 29 identified strains belonged to eight clonal complexes (CCs), the majority of which were in the ST-41/44/Lin.3 CC (n = 11; 37.9%). All of the identified strains harboured ƒHbp alleles representing a total of 15 sub-variants: the gene for NHBA protein was found in all but three of the studied strains (10.3%) with 13 identified sub-variants. There were 15 porA sub-types, seven of which were identified in just one CC. The findings of this study seem to suggest that both of the protein vaccines proposed for the prevention of invasive disease due to NmB (the 4-protein and the 2-protein products) have a composition that can evoke a theoretically effective antibody response against the meningococcal strains currently carried by adolescents living in Northern Italy. The genetic characteristics of NmB strains can be easily evaluated by means of molecular methods, the results of which can provide an albeit approximate estimate of the degree of protection theoretically provided by the available vaccines, and the possible future need to change their composition. PMID:23880917

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

  17. A sociocultural historical examination of youth argumentation across the settings of their lives: Implications for science education

    NASA Astrophysics Data System (ADS)

    Bricker, Leah A.

    In this dissertation, I examine youth argumentative practices as employed over time and across settings. Specifically, I examine youth perspective on argumentation and their own argumentative practices, the relationship between argumentation and learning, and the relationship between argumentation and youth, family, and community cultures. The theoretical framework I employ enables me to analyze argumentation as a set of practices employed in situated activity systems and framed by culturally-influenced ways of understanding activity associated with argumentative practice. I utilize data from a long-term team ethnography of youth science and technology learning across settings and time. Research fieldwork was conducted across dozens of social settings over the course of three years. Data includes approximately 700 hours of participant observations and interviews with thirteen upper elementary and middle school young people, as well as 128 of their parents, extended family members, peers, and teachers. Findings highlight the multitude of meanings youth associate with argumentation as it occurs in their lives (e.g., at home, in classrooms, in neighborhoods), as well as the detailed accounts of their argumentative practices and how these practices are differentially used across the social settings youth frequent. Additionally, findings highlight how historically rooted cultural practices help to frame youth perspectives on argumentation and their argumentative practices. Findings also include details about the specific communicative features of youth argumentation (e.g., linguistic elements such as discourse markers, evidentials, and indexicals, as well as non-verbal gestures) and how communicative features relate to youth learning across settings and over time. I use this dissertation in part to dialogue with the science education community, which currently argues that youth in science classrooms should learn how to argue scientifically. Designs of learning

  18. Apparent diffusive motion of centrin foci in living cells: implications for diffusion-based motion in centriole duplication

    NASA Astrophysics Data System (ADS)

    Rafelski, Susanne M.; Keller, Lani C.; Alberts, Jonathan B.; Marshall, Wallace F.

    2011-04-01

    The degree to which diffusion contributes to positioning cellular structures is an open question. Here we investigate the question of whether diffusive motion of centrin granules would allow them to interact with the mother centriole. The role of centrin granules in centriole duplication remains unclear, but some proposed functions of these granules, for example, in providing pre-assembled centriole subunits, or by acting as unstable 'pre-centrioles' that need to be captured by the mother centriole (La Terra et al 2005 J. Cell Biol. 168 713-22), require the centrin foci to reach the mother. To test whether diffusive motion could permit such interactions in the necessary time scale, we measured the motion of centrin-containing foci in living human U2OS cells. We found that these centrin foci display apparently diffusive undirected motion. Using the apparent diffusion constant obtained from these measurements, we calculated the time scale required for diffusion to capture by the mother centrioles and found that it would greatly exceed the time available in the cell cycle. We conclude that mechanisms invoking centrin foci capture by the mother, whether as a pre-centriole or as a source of components to support later assembly, would require a form of directed motility of centrin foci that has not yet been observed.

  19. Impact of Amorphous SiO2 Nanoparticles on a Living Organism: Morphological, Behavioral, and Molecular Biology Implications

    PubMed Central

    Ambrosone, Alfredo; Scotto di Vettimo, Maria Rosaria; Malvindi, Maria Ada; Roopin, Modi; Levy, Oren; Marchesano, Valentina; Pompa, Pier Paolo; Tortiglione, Claudia; Tino, Angela

    2014-01-01

    It is generally accepted that silica (SiO2) is not toxic. But the increasing use of silica nanoparticles (SiO2NPs) in many different industrial fields has prompted the careful investigation of their toxicity in biological systems. In this report, we describe the effects elicited by SiO2NPs on animal and cell physiology. Stable and monodisperse amorphous silica nanoparticles, 25 nM in diameter, were administered to living Hydra vulgaris (Cnidaria). The dose-related effects were defined by morphological and behavioral assays. The results revealed an all-or-nothing lethal toxicity with a rather high threshold (35 nM NPs) and a LT50 of 38 h. At sub lethal doses, the morphophysiological effects included: animal morphology alterations, paralysis of the gastric region, disorganization and depletion of tentacle specialized cells, increase of apoptotic and collapsed cells, and reduction of the epithelial cell proliferation rate. Transcriptome analysis (RNAseq) revealed 45 differentially expressed genes, mostly involved in stress response and cuticle renovation. Our results show that Hydra reacts to SiO2NPs, is able to rebalance the animal homeostasis up to a relatively high doses of SiO2NPs, and that the physiological modifications are transduced to gene expression modulation. PMID:25325055

  20. Spatial variability in growth-increment chronologies of long-lived freshwater mussels: Implications for climate impacts and reconstructions

    USGS Publications Warehouse

    Black, Bryan A.; Dunham, Jason B.; Blundon, Brett W.; Raggon, Mark F.; Zima, Daniela

    2010-01-01

    Estimates of historical variability in river ecosystems are often lacking, but long-lived freshwater mussels could provide unique opportunities to understand past conditions in these environments. We applied dendrochronology techniques to quantify historical variability in growth-increment widths in valves (shells) of western pearlshell freshwater mussels (Margaritifera falcata). A total of 3 growth-increment chronologies, spanning 19 to 26 y in length, were developed. Growth was highly synchronous among individuals within each site, and to a lesser extent, chronologies were synchronous among sites. All 3 chronologies negatively related to instrumental records of stream discharge, while correlations with measures of water temperature were consistently positive but weaker. A reconstruction of stream discharge was performed using linear regressions based on a mussel growth chronology and the regional Palmer Drought Severity Index (PDSI). Models based on mussel growth and PDSI yielded similar coefficients of prediction (R2Pred) of 0.73 and 0.77, respectively, for predicting out-ofsample observations. From an ecological perspective, we found that mussel chronologies provided a rich source of information for understanding climate impacts. Responses of mussels to changes in climate and stream ecosystems can be very site- and process-specific, underscoring the complex nature of biotic responses to climate change and the need to understand both regional and local processes in projecting climate impacts on freshwater species.

  1. Age changes of facial measurements in European young adult males: implications for the identification of the living.

    PubMed

    Gibelli, D; Mapelli, A; Obertovà, Z; Poppa, P; Gabriel, P; Ratnayake, M; Tutkuviene, J; Sforza, C; Ritz-Timme, S; Cattaneo, C

    2012-12-01

    Metric and morphological analyses of facial features are currently applied in cases of personal identification of the living on images acquired from video surveillance systems. However, facial assessment in the forensic context needs to be based on reliable comparative data for facial measurements. Facial changes in the age range of early adulthood (20-30 years) have been rarely described so far, although such knowledge would be beneficial for comparative personal identification on images. This study investigates changes in facial measurements in European males aged between 20 and 30 years in order to identify metric characters that can be used for personal identification in young adults. A sample of 404 males of European ancestry, aged between 20 and 30 years from Germany, Italy and Lithuania were recruited for this project. Fourteen facial measurements were taken and correlation coefficients were calculated for each cranial measurement with age. Only two measurements - labial width and physiognomic ear length - seem to change between 20 and 30 years with a positive statistically significant correlation (p<0.05). These results suggest caution for what may concern personal identification by assessment of ear and mouth morphology. PMID:22990009

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

    NASA Technical Reports Server (NTRS)

    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.

  3. Recent decadal trends in global phytoplankton composition

    NASA Astrophysics Data System (ADS)

    Rousseaux, Cecile S.; Gregg, Watson W.

    2015-10-01

    Identifying major trends in biogeochemical composition of the oceans is essential to improve our understanding of biological responses to climate forcing. Using the NASA Ocean Biogeochemical Model combined with ocean color remote sensing data assimilation, we assessed the trends in phytoplankton composition (diatoms, cyanobacteria, coccolithophores, and chlorophytes) at a global scale for the period 1998-2012. We related these trends in phytoplankton to physical conditions (surface temperature, surface photosynthetically available radiation (PAR), and mixed layer depth (MLD)) and nutrients (iron, silicate, and nitrate). We found a significant global decline in diatoms (-1.22% yr-1, p < 0.05). This trend was associated with a significant (p < 0.05) shallowing of the MLD (-0.20% yr-1), a significant increase in PAR (0.09% yr-1), and a significant decline in nitrate (-0.38% yr-1). The global decline in diatoms was mostly attributed to their decline in the North Pacific (-1.00% yr-1, p < 0.05), where the MLD shallowed significantly and resulted in a decline in all three nutrients (p < 0.05). None of the other phytoplankton groups exhibited a significant change globally, but regionally there were considerable significant trends. A decline in nutrients in the northernmost latitudes coincided with a significant decline in diatoms (North Pacific, -1.00% yr-1) and chlorophytes (North Atlantic, -9.70% yr-1). In the northern midlatitudes (North Central Pacific and Atlantic) where nutrients were more scarce, a decline in nutrients was associated with a decline in smaller phytoplankton: cyanobacteria declined significantly in the North Central Pacific (-0.72% yr-1) and Atlantic (-1.56% yr-1), and coccolithophores declined significantly in the North Central Atlantic (-2.06% yr-1). These trends represent the diversity and complexity of mechanisms that drives phytoplankton communities to adapt to variable conditions of nutrients, light, and mixed layer depth. These results provide

  4. Postoperative coagulopathy after live related donor hepatectomy: Incidence, predictors and implications for safety of thoracic epidural catheter

    PubMed Central

    Karna, ST; Pandey, CK; Sharma, S; Singh, A; Tandon, M; Pandey, VK

    2015-01-01

    Background: Coagulopathy after living donor hepatectomy (LDH) may endanger donor safety during removal of thoracic epidural catheter (TEC). The present study was conducted to evaluate the extent and duration of immediate postoperative coagulopathy after LDH. Materials and Methods: A retrospective analysis of perioperative record of LDH over three years was conducted after IRB approval. Variables such as age, gender, BMI, ASA classification, liver volume on CT scan, preoperative and postoperative INR, platelet count (PC) and ALT of each donor for five days was noted. In addition, duration of surgery, remnant as percentage total liver volume (Remnant%), blood loss, day of peak in PC and INR were also noted. Coagulopathy was defined as being present if INR exceeded 1.5 or platelet count fell below 1 × 105/mm3 on any day. Data was analyzed using SPSS 20 for Windows. Between group comparison was made using the Student ‘t’ test for continuous variables and chi square test for categorical variables. Univariate analysis was done. Multiple logistic regression analysis was used to find independent factor associated with coagulopathy. Results: Eighty four (84) donors had coagulopathy on second day (mean INR 1.9 ± 0.42). Low BMI, % of remnant liver and duration of surgery were independent predictors of coagulopathy. Right lobe hepatectomy had more coagulopathy than left lobe and low BMI was the only independent predictor. There was no correlation of coagulopathy with age, gender, blood loss, presence of epidural catheter, postoperative ALT or duration of hospital stay. High INR was the main contributor for coagulopathy. Conclusions: Coagulopathy is seen after donor hepatectomy. We recommend removal of the epidural catheter after the fifth postoperative day when INR falls below 1.5. PMID:26119437

  5. Prevalence and Contexts of Inconsistent Condom Use Among Heterosexual Men and Women Living with HIV in India: Implications for Prevention

    PubMed Central

    Chakrapani, Venkatesan; Newman, Peter A.; Shunmugam, Murali

    2010-01-01

    Abstract This investigation examined sexual behaviors among heterosexual persons living with HIV (PLHIV) in India. Study participants (mostly married) were interviewed during August to November 2006 in five Indian states using a quantitative survey (n = 100 men and 100 women), eight focus groups (n = 58 participants), and in-depth interviews (n = 31). One third of men and one fourth of women reported inconsistent condom use with regular sexual partners. Facilitators of condom use with regular partners included a feeling of personal responsibility to protect the health of the partner, desire to prevent acquisition and/or transmission of sexually transmitted infections, and the belief that condoms are needed for antiretroviral therapy to be effective. Barriers to consistent condom use with regular partners included the belief that condoms are unnecessary in HIV-positive seroconcordant relationships; lack of sexual satisfaction with condoms; the desire to have a child; husband's alcohol use, depression, and anxiety; fear that disclosure of HIV status will bring marital discord and family shame; and inadequate counseling by health care providers. Positive prevention programs should include counseling about benefits of safer sex in HIV-positive seroconcordant relationships, counseling about integrating condom use with sexual satisfaction and intimacy, condom use self-efficacy and negotiation skills-building, family planning counseling, mental health and alcohol dependence treatment, and counseling and skills-building about disclosure. Health care providers must be trained to provide these services. Furthermore, efforts are needed to promote tolerance for family planning choices made by couples and to counter the stigma associated with HIV/AIDS and condoms in the broader society. PMID:20095889

  6. High-pressure metamorphism in the southern New England Orogen: Implications for long-lived accretionary orogenesis in eastern Australia

    NASA Astrophysics Data System (ADS)

    Phillips, G.; Offler, R.; Rubatto, D.; Phillips, D.

    2015-09-01

    New geochemical, metamorphic, and isotopic data are presented from high-pressure metamorphic rocks in the southern New England Orogen (eastern Australia). Conventional and optimal thermobarometry are augmented by U-Pb zircon and 40Ar/39Ar phengite dating to define pressure-temperature-time (P-T-t) histories for the rocks. The P-T-t histories are compared with competing geodynamic models for the Tasmanides, which can be summarized as (i) a retreating orogen model, the Tasmanides formed above a continuous, west dipping, and eastward retreating subduction zone, and (ii) a punctuated orogen model, the Tasmanides formed by several arc accretion, subduction flip, and/or transference events. Whereas both scenarios are potentially supported by the new data, an overlap between the timing of metamorphic recrystallization and key stages of Tasmanides evolution favors a relationship between a single, long-lived subduction zone and the formation, exhumation, and exposure of the high-pressure rocks. By comparison with the retreating orogen model, the following links with the P-T-t histories emerge: (i) exhumation and underplating of oceanic eclogite during the Delamerian Orogeny, (ii) recrystallization of underplated and exhuming high-pressure rocks at amphibolite facies conditions coeval with a period of rollback, and (iii) selective recrystallization of high-pressure rocks at blueschist facies conditions, reflecting metamorphism in a cooled subduction zone. The retreating orogen model can also account for the anomalous location of the Cambrian-Ordovician high-pressure rocks in the Devonian-Carboniferous New England Orogen, where sequential rollback cycles detached and translated parts of the leading edge of the overriding plate to the next, younger orogenic cycle.

  7. Interactions between mercury and phytoplankton: speciation, bioavailability, and internal handling.

    PubMed

    Le Faucheur, Séverine; Campbell, Peter G C; Fortin, Claude; Slaveykova, Vera I

    2014-06-01

    The present review describes and discusses key interactions between mercury (Hg) and phytoplankton to highlight the role of phytoplankton in the biogeochemical cycle of Hg and to understand direct or indirect Hg effects on phytoplankton. Phytoplankton are exposed to various Hg species in surface waters. Through Hg uptake, phytoplankton affect the concentration, speciation, and fate of Hg in aquatic systems. The mechanisms by which phytoplankton take up Hg are still not well known, but several studies have suggested that both facilitated transport and passive diffusion could be involved. Once internalized, Hg will impact several physiological processes, including photosynthesis. To counteract these negative effects, phytoplankton have developed several detoxification strategies, such as the reduction of Hg to elemental Hg or its sequestration by intracellular ligands. Based on the toxicological studies performed so far in the laboratory, Hg is unlikely to be toxic to phytoplankton when they are exposed to environmentally relevant Hg concentrations. However, this statement should be taken with caution because questions remain as to which Hg species control Hg bioavailability and about Hg uptake mechanisms. Finally, phytoplankton are primary producers, and accumulated Hg will be transferred to higher consumers. Phytoplankton are a key component in aquatic systems, and their interactions with Hg need to be further studied to fully comprehend the biogeochemical cycle of Hg and the impact of this ubiquitous metal on ecosystems. PMID:24127330

  8. Spatial interaction among nontoxic phytoplankton, toxic phytoplankton, and zooplankton: emergence in space and time.

    PubMed

    Roy, Shovonlal

    2008-10-01

    In homogeneous environments, by overturning the possibility of competitive exclusion among phytoplankton species, and by regulating the dynamics of overall plankton population, toxin-producing phytoplankton (TPP) potentially help in maintaining plankton diversity-a result shown recently. Here, I explore the competitive effects of TPP on phytoplankton and zooplankton species undergoing spatial movements in the subsurface water. The spatial interactions among the species are represented in the form of reaction-diffusion equations. Suitable parametric conditions under which Turing patterns may or may not evolve are investigated. Spatiotemporal distributions of species biomass are simulated using the diffusivity assumptions realistic for natural planktonic systems. The study demonstrates that spatial movements of planktonic systems in the presence of TPP generate and maintain inhomogeneous biomass distribution of competing phytoplankton, as well as grazer zooplankton, thereby ensuring the persistence of multiple species in space and time. The overall results may potentially explain the sustainability of biodiversity and the spatiotemporal emergence of phytoplankton and zooplankton species under the influence of TPP combined with their physical movement in the subsurface water. PMID:19669506

  9. Systematic Review of TST Responses in People Living with HIV in Under-Resourced Settings: Implications for Isoniazid Preventive Therapy

    PubMed Central

    Kerkhoff, Andrew D.; Kranzer, Katharina; Samandari, Taraz; Nakiyingi-Miiro, Jessica; Whalen, Christopher C.; Harries, Anthony D.; Lawn, Stephen D.

    2012-01-01

    Background People living with HIV (PLWH) who have positive tuberculin skin tests (TST) benefit from isoniazid preventive therapy (IPT) whereas those testing TST-negative do not. Revised World Health Organization guidelines explicitly state that assessment of TST is not a requirement for initiation of IPT. However, it is not known what proportions of patients will benefit from IPT if implemented without targeting according to TST status. We therefore determined the proportions of PLWH who test TST-positive. Methodology/Principal Findings We systematically reviewed the literature published between January 1990 and February 2012 to determine the proportions of patients without active tuberculosis attending HIV care services in low and middle-income countries who tested TST-positive (≥5 mm induration). Proportions were also determined for different CD4 count strata. Data from 19 studies with 9,478 PLWH from sub-Saharan Africa, Asia and Central and South America were summarized. The vast majority were not receiving antiretroviral therapy (ART). A sub-analysis was conducted of 5 studies (5,567 subjects) from high TB prevalence countries of PLWH with negative TB screens attending HIV care and treatment settings for whom CD4 stratified data were available. The median proportion of PLWH testing TST-positive overall was 22.8% (range, 19.5–32.6%). The median (range) proportions with CD4 cell counts of <200, 200–499 or ≥500 cells/µL who tested positive were 12.4% (8.2–15.3%), 28.4% (20.1–36.9%) and 37.4% (31.3–56.3%), respectively. Heterogeneity in the data precluded calculation of pooled summary estimates. Conclusions/Significance In most settings, if IPT is administered to PLWH pre-ART without assessment of TST status, only a minority of those treated are likely to benefit, especially among those with the lowest CD4 cell counts. This may be inefficient use of resources and cost-effectiveness analyses should take this into account. Local knowledge of TST

  10. Implications of variability on many time scales for scientific advice on sustainable management of living marine resources

    NASA Astrophysics Data System (ADS)

    Rice, Jake

    The conceptual basis for understanding and management of living marine resources is built on three basic ecological principles developed in the first half of the past century: the law of the minimum, competitive exclusion, and succession. This paper highlights aspects of these principles that make them insufficient as a sound foundation for understanding and managing marine ecosystems, points out dangers of continuing to use approaches built on them, and presents alternatives which might be more appropriate and of lower risk. To do this, the paper considers variability of marine ecosystems on annual, medium and long-term time scales, highlighting that these scales correspond to less than, approximately equal to, and much greater than, the generation times of dominant predators in the systems. It also considers how each interval of variability may affect directly ecosystems which are controlled from the bottom up, top down, and middle outward, and how position and duration of forcing affect five types of responses: growth, maturation, recruitment, predation, and competition. Generally these five processes have manifestations at the scale of individuals, populations, and ecosystems, attention is drawn to which manifestations are the most significant for each duration and position of forcing. Effects of some combinations of duration of forcing and position of forcing can be explained reasonably well by conventional ecological theory. For other combinations, particularly forcing at time scales of predator generations on top-down or middle-out ecosystems, theory based on contest competition and equilibria are likely to be misleading. In these systems the major dynamics are transients, when many ecosystems are far from their carrying capacities, so scramble competition dominates, and the carrying capacity is not helpful in explaining the system dynamics. This review clarifies the sorts of questions that we should be asking, in order to begin to understand the transient

  11. Phytoplankton bloom off the coast of Ireland

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Irish Sea (right) is full of phytoplankton in this true-color image from January 15, 2002. The Irish Sea separates Ireland (center) from the United Kingdom (right). In this image the water of both the Irish and Celtic (lower right) Seas appears quite turbid, being a milky blue-green compared to the clearer waters of the open Atlantic (left). This milky appearance is likely due to the growth of marine plants called phytoplankton. Despite the fact that Ireland is at the same latitude as southern Hudson Bay, Canada, it remains green year round, thanks to the moderating effect on temperatures of the Atlantic Ocean. The Gulf Stream bring warmer waters up from the tropics, and southwesterly winds bring warmer air to the country, thus moderating seasonal temperature extremes.

  12. Optical determination of phytoplankton floristic composition

    NASA Astrophysics Data System (ADS)

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

    1997-02-01

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

  13. Revaluating ocean warming impacts on global phytoplankton

    NASA Astrophysics Data System (ADS)

    Behrenfeld, Michael J.; O'Malley, Robert T.; Boss, Emmanuel S.; Westberry, Toby K.; Graff, Jason R.; Halsey, Kimberly H.; Milligan, Allen J.; Siegel, David A.; Brown, Matthew B.

    2016-03-01

    Global satellite observations document expansions of the low-chlorophyll central ocean gyres and an overall inverse relationship between anomalies in sea surface temperature and phytoplankton chlorophyll concentrations. These findings can provide an invaluable glimpse into potential future ocean changes, but only if the story they tell is accurately interpreted. Chlorophyll is not simply a measure of phytoplankton biomass, but also registers changes in intracellular pigmentation arising from light-driven (photoacclimation) and nutrient-driven physiological responses. Here, we show that the photoacclimation response is an important component of temporal chlorophyll variability across the global ocean. This attribution implies that contemporary relationships between chlorophyll changes and ocean warming are not indicative of proportional changes in productivity, as light-driven decreases in chlorophyll can be associated with constant or even increased photosynthesis. Extension of these results to future change, however, requires further evaluation of how the multifaceted stressors of a warmer, higher-CO2 world will impact plankton communities.

  14. Phytoplankton off the Coast of Portugal

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A large phytoplankton bloom off of the coast of Portugal can be seen in this true-color image taken on April 23, 2002, by the Moderate-resolution Imaging Spectroradiometer (MODIS) aboard NASA's Terra satellite. The bloom is roughly half the size of Portugal and forms a bluish-green cloud in the water. The red spots in northwest Spain denote what are likely small agricultural fires. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

  15. Phytoplankton as bioindicator for waste stabilization ponds.

    PubMed

    Amengual-Morro, Caterina; Moyà Niell, Gabriel; Martínez-Taberner, Antoni

    2012-03-01

    Waste stabilization ponds are an appropriate technology for domestic onsite wastewater treatment. It is a low-cost technology, requires low maintenance, is highly efficient, mostly natural and remarkably sustainable. In facultative ponds, the existence of an algal population is very important for the stability of the symbiotic relation with aerobic bacteria. The aim of this work is to determine the pattern of microalgae in the facultative and maturation ponds to obtain information for the operation and maintenance work. The important parameters for phytoplankton measured in this study are the organic load, temperature, light penetration, dissolved oxygen and nutrients. Methodology consists in: analysis of main water quality parameters, plankton taxonomic determination and abundance calculation related with the maintenance operations. Results show that cyanobacteria are present in under-loaded conditions and chlorophyceae are present when the pond is overloaded. Using this methodology over time we can obtain a year round pattern to use the phytoplankton as a bioindicator of the pond's conditions. Our conclusion is that the phytoplankton determination and density can be used to know the pond's performance and help the operation and maintenance tasks. PMID:21820796

  16. Fluid dynamical niches of phytoplankton types.

    PubMed

    d'Ovidio, Francesco; De Monte, Silvia; Alvain, Séverine; Dandonneau, Yves; Lévy, Marina

    2010-10-26

    The biogeochemical role of phytoplanktonic organisms strongly varies from one plankton type to another, and their relative abundance and distribution have fundamental consequences at the global and climatological scales. In situ observations find dominant types often associated to specific physical and chemical water properties. However, the mechanisms and spatiotemporal scales by which marine ecosystems are organized are largely not known. Here we investigate the spatiotemporal organization of phytoplankton communities by combining multisatellite data, notably high-resolution ocean-color maps of dominant types and altimetry-derived Lagrangian diagnostics of the surface transport. We find that the phytoplanktonic landscape is organized in (sub-)mesoscale patches (10-100 km) of dominant types separated by physical fronts induced by horizontal stirring. These physical fronts delimit niches supported by water masses of similar history and whose lifetimes are comparable with the timescale of the bloom onset (few weeks). The resonance between biological activity and physical processes suggest that the spatiotemporal (sub-)mesoscales associated to stirring are determinant in the observation and modeling of marine ecosystems. PMID:20974927

  17. Cross-species transfer of viruses: implications for the use of viral vectors in biomedical research, gene therapy and as live-virus vaccines.

    PubMed

    Louz, Derrick; Bergmans, Hans E; Loos, Birgit P; Hoeben, Rob C

    2005-10-01

    All living organisms are continuously exposed to a plethora of viruses. In general, viruses tend to be restricted to the natural host species which they infect. From time to time viruses cross the host-range barrier expanding their host range. However, in very rare cases cross-species transfer is followed by the establishment and persistence of a virus in the new host species, which may result in disease. Recent examples of viruses that have crossed the species barrier from animal reservoirs to humans are hantavirus, haemorrhagic fever viruses, arboviruses, Nipah and Hendra viruses, avian influenza virus (AI), monkeypox virus, and the SARS-associated coronavirus (SARS-CoV). The opportunities for cross-species transfer of mammalian viruses have increased in recent years due to increased contact between humans and animal reservoirs. However, it is difficult to predict when such events will take place since the viral adaptation that is needed to accomplish this is multifactorial and stochastic. Against this background the intensified use of viruses and their genetically modified variants as viral gene transfer vectors for biomedical research, experimental gene therapy and for live-vector vaccines is a cause for concern. This review addresses a number of potential risk factors and their implications for activities with viral vectors from the perspective of cross-species transfer of viruses in nature, with emphasis on the occurrence of host-range mutants resulting from either cell culture or tropism engineering. The issues are raised with the intention to assist in risk assessments for activities with vector viruses. PMID:15986492

  18. Coupling of heterotrophic bacteria to phytoplankton bloom development at different pCO2 levels: a mesocosm study

    NASA Astrophysics Data System (ADS)

    Allgaier, M.; Riebesell, U.; Vogt, M.; Thyrhaug, R.; Grossart, H.-P.

    2008-07-01

    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. Coupling of heterotrophic bacteria to phytoplankton bloom development at different pCO2 levels: a mesocosm study

    NASA Astrophysics Data System (ADS)

    Allgaier, M.; Riebesell, U.; Vogt, M.; Thyrhaug, R.; Grossart, H.-P.

    2008-01-01

    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 linked to phytoplankton development and, hence, may also potentially depend on changes in pCO2.

  20. Temperature effects on phytoplankton diversity - The zooplankton link

    NASA Astrophysics Data System (ADS)

    Lewandowska, Aleksandra M.; Hillebrand, Helmut; Lengfellner, Kathrin; Sommer, Ulrich

    2014-01-01

    Recent climate warming is expected to affect phytoplankton biomass and diversity in marine ecosystems. Temperature can act directly on phytoplankton (e.g. rendering physiological processes) or indirectly due to changes in zooplankton grazing activity. We tested experimentally the impact of increased temperature on natural phytoplankton and zooplankton communities using indoor mesocosms and combined the results from different experimental years applying a meta-analytic approach. We divided our analysis into three bloom phases to define the strength of temperature and zooplankton impacts on phytoplankton in different stages of bloom development. Within the constraints of an experiment, our results suggest that increased temperature and zooplankton grazing have similar effects on phytoplankton diversity, which are most apparent in the post-bloom phase, when zooplankton abundances reach the highest values. Moreover, we observed changes in zooplankton composition in response to warming and initial conditions, which can additionally affect phytoplankton diversity, because changing feeding preferences of zooplankton can affect phytoplankton community structure. We conclude that phytoplankton diversity is indirectly affected by temperature in the post-bloom phase through changing zooplankton composition and grazing activities. Before and during the bloom, however, these effects seem to be overruled by temperature enhanced bottom-up processes such as phytoplankton nutrient uptake.

  1. Calcareous phytoplankton perturbations through the Eocene/Oligocene Transition

    NASA Astrophysics Data System (ADS)

    Bown, P. R.; Dunkley Jones, T.; Expedition 320/321 Shipboard Party

    2010-12-01

    The Eocene-Oligocene transition (E/OT) witnessed the most significant climatic change in the Cenozoic with a fundamental reordering of the planet’s oceanic and atmospheric circulation, the cooling of deep and high-latitude waters and the formation of continental scale ice sheets on Antarctica. Records from the equatorial Pacific show rapid and highly correlated increases in deep-ocean oxygen and carbon isotopes and a drop in the Calcium Carbonate Compensation Depth (CCD) of over a kilometre (Coxall et al. 2005). The role of surface ocean productivity changes, especially at low latitudes, within this carbon cycle perturbation remains open to question. Detailed micropalaeontological analyses from shelf-slope sections of Tanzania, which host exceptionally well preserved calcareous microfossils, indicate a significant reorganization of planktonic niches coincident with the E/OT (Pearson et al. 2008). These include major assemblage shifts within the calcareous phytoplankton closely coupled to the isotopic excursions (Dunkley Jones et al. 2008). Here, we integrate the Tanzanian records with patterns of calcareous nannofossil turnover observed in historic DSDP Site 242 (Davie Ridge, Indian Ocean), the US Gulf Coast and preliminary data from new E/OT successions recovered during the recent IODP Expedition 320 in the eastern equatorial Pacific and discuss their implications for nutrient cycling and surface ocean productivity across the E/OT. Coxall, H. K., Wilson, P. A., Palike, H., Lear, C. H. & Backman, J. 2005. Rapid stepwise onset of Antarctic glaciation and deeper calcite compensation in the Pacific Ocean. Nature 433: 53-57. Dunkley Jones, T., Bown, P. R., Pearson, P. N., Wade, B. S., Coxall, H. K. & Lear, C. H. 2008. Major shifts in calcareous phytoplankton assemblages through the Eocene-Oligocene transition of Tanzania and their implications for low-latitude primary production, Paleoceanography, 23, PA4204, doi:10.1029/2008PA001640. Pearson, P.N, McMillan, I. K

  2. Seasonality, phytoplankton succession and the biogeochemical impacts of an autumn storm in the northeast Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Painter, Stuart C.; Finlay, Madelaine; Hemsley, Victoria S.; Martin, Adrian P.

    2016-03-01

    phytoplankton growth in surface waters should be tempered with greater understanding of the role of storm driven vertical reorganization of the water column and of resident phytoplankton communities. Crucially, in this case we observed no change in integrated chlorophyll, particulate organic carbon or biogenic silica concentrations despite also observing a ∼50% increase in surface chlorophyll concentrations which indicated that the surface enhancement in chlorophyll concentrations was most likely fed from below rather than resulting from in situ growth. Though not measured directly there was no evidence of enhanced export fluxes associated with this storm. These observations have implications for the growing practice of using chlorophyll fluorescence from remote platforms to determine ocean productivity late in the annual productivity period and in response to storm mixing.

  3. The spatial and temporal development of the spring phytoplankton bloom in the Celtic Sea, April 1979

    NASA Astrophysics Data System (ADS)

    Fasham, M. J. R.; Holligan, P. M.; Pugh, P. R.

    The results are presented from three hydrogrpahic surveys in April 1979 of a 40 × 50 km region of the Celtic Sea, centred at 7°W and 51°N, using a towed undulating sensor system. In the 5 {1}/{2} days between Surveys 1 and 2, the seasonal thermocline was established, with surface to bottom temperature differences reaching 1.5°C, the average surface chlorophyll a level increased from ∼ 1 to ∼ 5.5 mg m -3 due mainly to the growth of diatoms, and the surface nitrate concentration decreased from 6 to 1 μM. The third survey was carried out after a further two days and, although surface properties changed little, there was a general deepening of the mixed layer due to stronger winds, and a further increase in the standing stock of phytoplankton. By applying appropriate techniques of horizontal spatial averaging, which took into account possible advective effects, a quantitative comparison was made of the changes at two positions in the survey area which showed significant differences in the rate of development of the phytoplankton population. A simple model of phytoplankton growth was then developed, based on calculations of eddy diffusivity, on measurements of rates of photosynthetic carbon assimilation, and on observations of carbon to chlorophyll ratios, subsurface light attenuation and inorganic nutrient levels. In the absence of any data on zooplankton populations, the loss of phytoplankton by grazing was left as a free parameter. The model was only partly successful in reproducing the observed changes in chlorophyll concentrations during the first 5 {1}/{2} days and showed serious limitations for the subsequent 2 days. However, it emphasised several features of the dynamics of spring phytoplankton populations which require further experimental or observational investigation. These include more precise measurements of carbon to chlorophyll ratios and grazing pressure to which the model is sensitive over a rather narrow range (this has important implications

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

    NASA Astrophysics Data System (ADS)

    Lin, Cai; Li, Hui; He, Qing; Xu, Kuncan; Wu, Shengsan; Zhang, Yuanbiao; Chen, Jinmin; Chen, Baohong; Lin, Libin; Lu, Meiluan; Chen, Weifen; Tang, Rongkun; Ji, Weidong

    2010-01-01

    This paper describes a time series experiment examining the nitrogen and phosphorus intake of natural phytoplankton communities by a microcosms approach. Seawater samples containing natural phytoplankton communities were collected from waters around Baozhu Islet in inner Xiamen Bay and around Qingyu Islet in the outer bay. The goal was to elucidate the relationship between phytoplankton population enhancement, the biological removal of nitrogen and phosphorus from the seawater, and the phytoplankton nitrogen and phosphorus intake ratio based on nitrogen and phosphorus removal from seawater by phytoplankton, to provide a basis for detecting prewarning conditions for red tide and the assessment of red tide events. Two key results were obtained: 1. During the experiment, the nitrogen and phosphorus seawater concentrations in samples from these two sites were negatively and closely correlated to the logarithm of the phytoplankton cell concentration and to the value of the apparent oxygen increment. The ratio of the intake coefficients was 3.5:1 for phosphorus and 1.1:1 for nitrogen for the phytoplankton between these samples from around Baozhu Islet and Qingyu Islet, respectively. This indicates that the intake capabilities of phytoplankton for nitrogen in the two waters are essentially identical. However, for phosphorus, the capability was much higher in the Baozhu Islet waters than the Qingyu Islet waters. In other words, the phytoplankton in Qingyu Islet waters produced more biomass while consuming the same amount of phosphorus as the other waters; 2. The phytoplankton nitrogen and phosphorus intake ratio from the Baozhu Islet and Qingyu Islet waters was 20:1 and 36:1, respectively. The latter waters had a significantly higher ratio than the former and both were higher than the Redfield Ratio. These results indicate that nitrogen and phosphorus intake ratios by phytoplankton can vary significantly from region to region.

  5. Thin layers and species-specific characterization of the phytoplankton community in Monterey Bay, California, USA

    NASA Astrophysics Data System (ADS)

    Rines, J. E. B.; McFarland, M. N.; Donaghay, P. L.; Sullivan, J. M.

    2010-01-01

    During the summers of 2005 and 2006, experiments designed to understand the properties of densely concentrated, thin layers of plankton and the processes governing their dynamics were conducted in Monterey Bay, California, USA. Our goal was to elucidate the role that species-specific properties of phytoplankton play in thin layer dynamics. Using adaptive sampling, we collected water samples from inside and outside bio-optical features of the water column. Characterization of the phytoplankton was compiled from live and preserved samples, and analyzed within a framework of physical, optical, chemical and acoustical data. In both years, Monterey Bay was home to an extraordinarily diverse assemblage of phytoplankton and other protists. Bioluminescent dinoflagellates, and Harmful Algal Bloom (HAB) taxa were common. In 2005, community assemblages were widespread, thus advection of water through the experimental mooring array did not result in floristic changes. In 2006 phytoplankton were very patchy in horizontal distribution, and advection of water through the array was at times accompanied by dramatic shifts in community composition. Individual taxa often exhibited disparate patterns of vertical distribution, with some found throughout the water column, whereas others were restricted to narrow depth intervals. Thin layers were observed in both years. In 2005, the dinoflagellate Akashiwo sanguinea formed intense thin layers near the pycnocline at night, and migrated to near surface waters at dawn. In 2006, layer composition was more complex, and related to the water mass present at the time of sampling. Optically detected thin layers of phytoplankton can be studied from the perspective of the impact their high biomass has on both ecological processes, and ocean optics. But thin layers can also be studied from the species-specific perspective of each organism, its role within the thin layer habitat, and the impact that life within a thin layer has on its life history

  6. Responding to flow: How phytoplankton adapt migration strategies to tackle turbulence

    NASA Astrophysics Data System (ADS)

    Sengupta, Anupam; Carrara, Francesco; Stocker, Roman

    2014-11-01

    Phytoplankton are among the ocean's most important organisms and it has long been recognized that turbulence is a primary determinant of their fitness. Yet, mechanisms by which phytoplankton may adapt to turbulence have remained unknown. We present experiments that demonstrate how phytoplankton are capable of rapid adaptive behavior in response to fluid flow disturbances that mimic turbulence. Our study organism was the toxic marine alga Heterosigma akashiwo, known to exhibit ``negative gravitaxis,'' i . e . , to frequently migrate upwards against gravity. To mimic the effect of Kolmogorov-scale turbulent eddies, which expose cells to repeated reorientations, we observed H. akashiwo in a ``flip chamber,'' whose orientation was periodically flipped. Tracking of single cells revealed a striking, robust behavioral adaptation, whereby within tens of minutes half of the population reversed its direction of migration to swim downwards, demonstrating an active response to fluid flow. Using confocal microscopy, we provide a physiological rationalization of this behavior in terms of the redistribution of internal organelles, and speculate on the motives for this bet-hedging-type strategy. This work suggests that the effects of fluid flow - not just passive but also active - on plankton represents a rich area of investigation with considerable implications for some of earth's most important organisms.

  7. Effects of phytoplankton cell size and chloride concentration on the bioaccumulation of methylmercury in marine phytoplankton.

    PubMed

    Kim, Hyunji; Van Duong, Hieu; Kim, Eunhee; Lee, Byeong-Gweon; Han, Seunghee

    2014-08-01

    In the current study, the effects of phytoplankton cell size and methylmercury (MeHg) speciation on the bioaccumulation of MeHg by marine phytoplankton were investigated. Volume concentration factors (VCFs) of MeHg were determined in relation to the surface area to volume ratio of the cells for four species of diatom and a cyanobacteria species cultured in unenriched seawater. The VCFs of MeHg, ranging from 7.3 × 10(4) to 1.6 × 10(6) , increased linearly as the cell surface area-to-volume ratio increased. It suggests that pico- and nano-dominated phytoplankton communities may lead to larger MeHg accumulation than the one dominated by microphytoplankton. MeHg VCFs increased with increasing chloride concentration from 0.47 to 470 mM, indicating that MeHg bioaccumulation is enhanced under conditions that facilitate membrane permeability by the formation of neutral MeHgCl species. Overall results suggest that the size distributions of the planktonic community as well as the seawater chemistry affect MeHg bioaccumulation by marine phytoplankton. PMID:23065924

  8. Acclimation of marine phytoplankton to ultraviolet radiation

    SciTech Connect

    Hazzard, C.E.

    1993-01-01

    The ability of marine phytoplankton to acclimate to ultraviolet radiation (UVR) was examined. Monocultures of a subtropical diatom, Chaetoceros gracilis, were maintained under photosynthetically available radiation (PAR-only) and PAR plus UVR (PAR + UVR) for a 48 h exposure period. By 24 h, and for the remainder of the 48 h exposure period, growth rate, pigment concentrations, Rubisco activity and carbon fixation capability were not affected by PAR + UVR. After 48 h of UVR exposure turnover rates of the putative D1 protein of photosystem II (PSII) and Chlorophyll (Chl) a were higher than controls, suggesting continual damage by UVR. Maximum rate of oxygen evolution and the efficiency of PSII increased following acclimation to UVR. The maximum rate of carbon fixation was not affected on a per cell basis and decreased on a per Chl a basis following UVR acclimation. Chlorophyll a specific photosynthesis over a 5 h exposure period was equal between the two acclimation treatments (PAR-only and PAR + UV). Transfer of PAR-only acclimated cells to PAR + UVR for the same 5 h period lead to a reduction in Chl a specific photosynthesis, indicating acute inhibition of photosynthesis by UVR. Chlorophyll a specific photosynthesis of cells acclimated to PAR + UVR and transferred to PAR-only was 24% higher than cells maintained in PAR + UVR during the determination of photosynthesis, indicating enhancement of productivity following the removal of UVR. Effect of ambient subtropical UVR on natural phytoplankton populations was examined. Rates of primary production by assemblages Natural phytoplankton assemblages from Hawaii, exposed to PAR-only and PAR + UVR were equal. Assemblages acclimated to PAR + UVR and then transferred to PAR-only fixed 67% more carbon per Chl a than assemblages acclimated to PAR + UVR and maintained in PAR + UVR. Acclimation to ambient PAR + UVR resulted in a 171% increase in Chl a concentration compared to assemblages maintained under PAR-only conditions.

  9. Phytoplankton-Fluorescence-Lifetime Vertical Profiler

    NASA Technical Reports Server (NTRS)

    Fernandez, Salvador M.; Guignon, Ernest F.; St. Louis, Ernest

    2004-01-01

    A battery-operated optoelectronic instrument is designed to be lowered into the ocean to measure the intensity and lifetime of fluorescence of chlorophyll A in marine phytoplankton as a function of depth from 0 to 300 m. Fluorescence lifetimes are especially useful as robust measures of photosynthetic productivity of phytoplankton and of physical and chemical mechanisms that affect photosynthesis. The knowledge of photosynthesis in phytoplankton gained by use of this and related instruments is expected to contribute to understanding of global processes that control the time-varying fluxes of carbon and associated biogenic elements in the ocean. The concentration of chlorophyll in the ocean presents a major detection challenge because in order to obtain accurate values of photosynthetic parameters, the intensity of light used to excite fluorescence must be kept very low so as not to disturb the photosynthetic system. Several innovations in fluorometric instrumentation were made in order to make it possible to reach the required low detection limit. These innovations include a highly efficient optical assembly with an integrated flow-through sample interface, and a high-gain, low-noise electronic detection subsystem. The instrument also incorporates means for self-calibration during operation, and electronic hardware and software for control, acquisition and analysis of data, and communications. The electronic circuitry is highly miniaturized and designed to minimize power demand. The instrument is housed in a package that can withstand the water pressure at the maximum depth of 300 m. A light-emitting diode excites fluorescence in the sample flow cell, which is placed at one focal point of an ellipsoidal reflector. A photomultiplier tube is placed at the other focal point. This optical arrangement enables highly efficient collection of fluorescence emitted over all polar directions. Fluorescence lifetime is measured indirectly, by use of a technique based on the

  10. Phytoplankton off the Coast of Washington State

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Clear weather over the Pacific Northwest yesterday gave the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) a good view of this mountain region of the United States. Also, there are several phytoplankton blooms visible offshore. The white areas hugging the California coastline toward the bottom of the image are low-level stratus clouds. SeaWiFS acquired this true-color scene on October 3, 2001. Image courtesy the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  11. Bicarbonate uptake by Southern Ocean phytoplankton

    NASA Astrophysics Data System (ADS)

    Cassar, Nicolas; Laws, Edward A.; Bidigare, Robert R.; Popp, Brian N.

    2004-06-01

    Marine phytoplankton have the potential to significantly buffer future increases in atmospheric carbon dioxide levels. However, in order for CO2 fertilization to have an effect on carbon sequestration to the deep ocean, the increase in dissolved CO2 must stimulate primary productivity; that is, marine phototrophs must be CO2 limited [, 1993]. Estimation of the extent of bicarbonate (HCO3-) uptake in the oceans is therefore required to determine whether the anthropogenic carbon sources will enhance carbon flux to the deep ocean. Using short-term 14CO2-disequilibrium experiments during the Southern Ocean Iron Experiment (SOFeX), we show that HCO3- uptake by Southern Ocean phytoplankton is significant. Since the majority of dissolved inorganic carbon (DIC) in the ocean is in the form of bicarbonate, the biological pump may therefore be insensitive to anthropogenic CO2. Approximately half of the DIC uptake observed was attributable to direct HCO3- uptake, the other half being direct CO2 uptake mediated either by passive diffusion or active uptake mechanisms. The increase in growth rates and decrease in CO2 concentration associated with the iron fertilization did not trigger any noticeable changes in the mode of DIC acquisition, indicating that under most environmental conditions the carbon concentrating mechanism (CCM) is constitutive. A low-CO2 treatment induced an increase in uptake of CO2, which we attributed to increased extracellular carbonic anhydrase activity, at the expense of direct HCO3- transport across the plasmalemma. Isotopic disequilibrium experimental results are consistent with Southern Ocean carbon stable isotope fractionation data from this and other studies. Although iron fertilization has been shown to significantly enhance phytoplankton growth and may potentially increase carbon flux to the deep ocean, an important source of the inorganic carbon taken up by phytoplankton in this study was HCO3-, whose concentration is negligibly affected by the

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

    NASA Astrophysics Data System (ADS)

    Le Quéré, Corinne; Buitenhuis, Erik T.; Moriarty, Róisín; Alvain, Séverine; Aumont, Olivier; Bopp, Laurent; Chollet, Sophie; Enright, Clare; Franklin, Daniel J.; Geider, Richard J.; Harrison, Sandy P.; Hirst, Andrew G.; Larsen, Stuart; Legendre, Louis; Platt, Trevor; Prentice, I. Colin; Rivkin, Richard B.; Sailley, Sévrine; Sathyendranath, Shubha; Stephens, Nick; Vogt, Meike; Vallina, Sergio M.

    2016-07-01

    Global ocean biogeochemistry models currently employed in climate change projections use highly simplified representations of pelagic food webs. These food webs do not necessarily include critical pathways by which ecosystems interact with ocean biogeochemistry and climate. Here we present a global biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types (PFTs): six types of phytoplankton, three types of zooplankton, and heterotrophic procaryotes. We improved the representation of zooplankton dynamics in our model through (a) the explicit inclusion of large, slow-growing macrozooplankton (e.g. krill), and (b) the introduction of trophic cascades among the three zooplankton types. We use the model to quantitatively assess the relative roles of iron vs. grazing in determining phytoplankton biomass in the Southern Ocean high-nutrient low-chlorophyll (HNLC) region during summer. When model simulations do not include macrozooplankton grazing explicitly, they systematically overestimate Southern Ocean chlorophyll biomass during the summer, even when there is no iron deposition from dust. When model simulations include a slow-growing macrozooplankton and trophic cascades among three zooplankton types, the high-chlorophyll summer bias in the Southern Ocean HNLC region largely disappears. Our model results suggest that the observed low phytoplankton biomass in the Southern Ocean during summer is primarily explained by the dynamics of the Southern Ocean zooplankton community, despite iron limitation of phytoplankton community growth rates. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean.

  13. DIFFERENTIAL PHYTOPLANKTON SINKING- AND GROWTH-RATES: AN EIGENVALUE ANALYSIS

    EPA Science Inventory

    An eigenvalue analysis of the vertical phytoplankton biomass equation is applied to calculate the differential sinking- and loss-rates of phytoplankton for different taxonomic groups in Lake Lyndon B. Johnson (Texas) and in Lake Erie. The analysis includes factors determining the...

  14. The phytoplankton component of seston in San Francisco Bay

    USGS Publications Warehouse

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

    1987-01-01

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

  15. PHYTOPLANKTON DEPOSITION TO CHESAPEAKE BAY SEDIMENTS DURING WINTER-SPRING

    EPA Science Inventory

    The often rapid deposition of phytoplankton to sediments at the conclusion of the spring phytoplankton bloom is an important component of benthic-pelagic coupling in temperate and high latitude estuaries and other aquatic systems. However, quantifying the flux is difficult, parti...

  16. Heterotrophic bacterial responses to the winter-spring phytoplankton bloom in open waters of the NW Mediterranean

    NASA Astrophysics Data System (ADS)

    Gomes, Ana; Gasol, Josep M.; Estrada, Marta; Franco-Vidal, Leticia; Díaz-Pérez, Laura; Ferrera, Isabel; Morán, Xosé Anxelu G.

    2015-02-01

    The response of planktonic heterotrophic prokaryotes to the NW Mediterranean winter-spring offshore phytoplankton bloom was assessed in 3 cruises conducted in March, April-May and September 2009. Bulk measurements of phytoplankton and bacterioplankton biomass and production were complemented with an insight into bacterial physiological structure by single-cell analysis of nucleic acid content [low (LNA) vs. high (HNA)] and membrane integrity ("Live" vs. "Dead" cells). Bacterial production empirical conversion factors (0.82±0.25 SE kg C mol leucine-1) were almost always well below the theoretical value. Major differences in most microbial variables were found among the 3 periods, which varied from extremely high phytoplankton biomass and production during the bloom in March (>1 g C m-2 d-1 primary production) to typically oligotrophic conditions during September stratification (<200 mg C m-2 d-1). In both these periods bacterial production was ~30 mg C m-2 d-1 while very large bacterial production (mean 228, with some stations exceeding 500 mg C m-2 d-1) but low biomass was observed during the April-May post-bloom phase. The contribution of HNA (30-67%) and "Live" cells (47-97%) were temporally opposite in the study periods, with maxima in March and September, respectively. Different relationships were found between physiological structure and bottom-up variables, with HNA bacteria apparently more responsive to phytoplankton only during the bloom, coinciding with larger average cell sizes of LNA bacteria. Moderate phytoplankton-bacterioplankton coupling of biomass and activity was only observed in the bloom and post-bloom phases, while relationships between both compartments were not significant under stratification. With all data pooled, bacteria were only weakly bottom-up controlled. Our analyses show that the biomass and production of planktonic algae and bacteria followed opposite paths in the transition from bloom to oligotrophic conditions.

  17. A Fluorescent Live Imaging Screening Assay Based on Translocation Criteria Identifies Novel Cytoplasmic Proteins Implicated in G Protein-coupled Receptor Signaling Pathways.

    PubMed

    Lecat, Sandra; Matthes, Hans W D; Pepperkok, Rainer; Simpson, Jeremy C; Galzi, Jean-Luc

    2015-05-01

    Several cytoplasmic proteins that are involved in G protein-coupled receptor signaling cascades are known to translocate to the plasma membrane upon receptor activation, such as beta-arrestin2. Based on this example and in order to identify new cytoplasmic proteins implicated in the ON-and-OFF cycle of G protein-coupled receptor, a live-imaging screen of fluorescently labeled cytoplasmic proteins was performed using translocation criteria. The screening of 193 fluorescently tagged human proteins identified eight proteins that responded to activation of the tachykinin NK2 receptor by a change in their intracellular localization. Previously we have presented the functional characterization of one of these proteins, REDD1, that translocates to the plasma membrane. Here we report the results of the entire screening. The process of cell activation was recorded on videos at different time points and all the videos can be visualized on a dedicated website. The proteins BAIAP3 and BIN1, partially translocated to the plasma membrane upon activation of NK2 receptors. Proteins ARHGAP12 and PKM2 translocated toward membrane blebs. Three proteins that associate with the cytoskeleton were of particular interest : PLEKHH2 rearranged from individual dots located near the cell-substrate adhesion surface into lines of dots. The speriolin-like protein, SPATC1L, redistributed to cell-cell junctions. The Chloride intracellular Channel protein, CLIC2, translocated from actin-enriched plasma membrane bundles to cell-cell junctions upon activation of NK2 receptors. CLIC2, and one of its close paralogs, CLIC4, were further shown to respond with the same translocation pattern to muscarinic M3 and lysophosphatidic LPA receptors. This screen allowed us to identify potential actors in signaling pathways downstream of G protein-coupled receptors and could be scaled-up for high-content screening. PMID:25759509

  18. The interaction of light with phytoplankton in the marine environment

    NASA Technical Reports Server (NTRS)

    Carder, Kendall L.; Collins, Donald J.; Perry, Mary Jane; Clark, H. Lawrence; Mesias, Jorge M.

    1986-01-01

    In many regions of the ocean, the phytoplankton population dominates both the attenuation and scattering of light. In other regions, non-phytoplankton contributions to the absorption and scattering may change the remote sensing reflectance and thus affect the ability to interpret remotely sensed ocean color. Hence, variations in the composition of both the phytoplankton population and of the non-phytoplankton material in the water can affect the optical properties of the sea. The effects of these contributions to the remote sensing reflectance and the submarine light field are modeled using scattering and absorption measurements of phytoplankton cultures obtained at the Friday Harbor Laboratory of the University of Washington. These measurements are used to develop regional chlorophyll algorithms specific to the summer waters of Puget Sound for the Coastal Zone Color Scanner, Thematic Mapper and future Ocean Color Imager, and their accuracies are compared for high chlorophyll waters with little or no Gelbstoff, but with variable detrital and suspended material.

  19. Toxicity of atmospheric aerosols on marine phytoplankton

    PubMed Central

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

    2009-01-01

    Atmospheric aerosol deposition is an important source of nutrients and trace metals to the open ocean that can enhance ocean productivity and carbon sequestration and thus influence atmospheric carbon dioxide concentrations and climate. Using aerosol samples from different back trajectories in incubation experiments with natural communities, we demonstrate that the response of phytoplankton growth to aerosol additions depends on specific components in aerosols and differs across phytoplankton species. Aerosol additions enhanced growth by releasing nitrogen and phosphorus, but not all aerosols stimulated growth. Toxic effects were observed with some aerosols, where the toxicity affected picoeukaryotes and Synechococcus but not Prochlorococcus. We suggest that the toxicity could be due to high copper concentrations in these aerosols and support this by laboratory copper toxicity tests preformed with Synechococcus cultures. However, it is possible that other elements present in the aerosols or unknown synergistic effects between these elements could have also contributed to the toxic effect. Anthropogenic emissions are increasing atmospheric copper deposition sharply, and based on coupled atmosphere–ocean calculations, we show that this deposition can potentially alter patterns of marine primary production and community structure in high aerosol, low chlorophyll areas, particularly in the Bay of Bengal and downwind of South and East Asia. PMID:19273845

  20. Toxicity of atmospheric aerosols on marine phytoplankton

    USGS Publications Warehouse

    Paytan, A.; Mackey, K.R.M.; Chen, Y.; Lima, I.D.; Doney, S.C.; Mahowald, N.; Labiosa, R.; Post, A.F.

    2009-01-01

    Atmospheric aerosol deposition is an important source of nutrients and trace metals to the open ocean that can enhance ocean productivity and carbon sequestration and thus influence atmospheric carbon dioxide concentrations and climate. Using aerosol samples from different back trajectories in incubation experiments with natural communities, we demonstrate that the response of phytoplankton growth to aerosol additions depends on specific components in aerosols and differs across phytoplankton species. Aerosol additions enhanced growth by releasing nitrogen and phosphorus, but not all aerosols stimulated growth. Toxic effects were observed with some aerosols, where the toxicity affected picoeukaryotes and Synechococcus but not Prochlorococcus.We suggest that the toxicity could be due to high copper concentrations in these aerosols and support this by laboratory copper toxicity tests preformed with Synechococcus cultures. However, it is possible that other elements present in the aerosols or unknown synergistic effects between these elements could have also contributed to the toxic effect. Anthropogenic emissions are increasing atmospheric copper deposition sharply, and based on coupled atmosphere-ocean calculations, we show that this deposition can potentially alter patterns of marine primary production and community structure in high aerosol, low chlorophyll areas, particularly in the Bay of Bengal and downwind of South and East Asia.

  1. Toxicity of atmospheric aerosols on marine phytoplankton.

    PubMed

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

    2009-03-24

    Atmospheric aerosol deposition is an important source of nutrients and trace metals to the open ocean that can enhance ocean productivity and carbon sequestration and thus influence atmospheric carbon dioxide concentrations and climate. Using aerosol samples from different back trajectories in incubation experiments with natural communities, we demonstrate that the response of phytoplankton growth to aerosol additions depends on specific components in aerosols and differs across phytoplankton species. Aerosol additions enhanced growth by releasing nitrogen and phosphorus, but not all aerosols stimulated growth. Toxic effects were observed with some aerosols, where the toxicity affected picoeukaryotes and Synechococcus but not Prochlorococcus. We suggest that the toxicity could be due to high copper concentrations in these aerosols and support this by laboratory copper toxicity tests preformed with Synechococcus cultures. However, it is possible that other elements present in the aerosols or unknown synergistic effects between these elements could have also contributed to the toxic effect. Anthropogenic emissions are increasing atmospheric copper deposition sharply, and based on coupled atmosphere-ocean calculations, we show that this deposition can potentially alter patterns of marine primary production and community structure in high aerosol, low chlorophyll areas, particularly in the Bay of Bengal and downwind of South and East Asia. PMID:19273845

  2. Toxic phytoplankton in San Francisco Bay

    USGS Publications Warehouse

    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.

  3. A simple optical index shows spatial and temporal heterogeneity in phytoplankton community composition during the 2008 North Atlantic Bloom Experiment

    NASA Astrophysics Data System (ADS)

    Cetinić, I.; Perry, M. J.; D'Asaro, E.; Briggs, N.; Poulton, N.; Sieracki, M. E.; Lee, C. M.

    2015-04-01

    The ratio of two in situ optical measurements - chlorophyll fluorescence (Chl F) and optical particulate backscattering (bbp) - varied with changes in phytoplankton community composition during the North Atlantic Bloom Experiment in the Iceland Basin in 2008. Using ship-based measurements of Chl F, bbp, chlorophyll a (Chl), high-performance liquid chromatography (HPLC) pigments, phytoplankton composition and carbon biomass, we found that oscillations in the ratio varied with changes in plankton community composition; hence we refer to Chl F/bbp as an "optical community index". The index varied by more than a factor of 2, with low values associated with pico- and nanophytoplankton and high values associated with diatom-dominated phytoplankton communities. Observed changes in the optical index were driven by taxa-specific chlorophyll-to-autotrophic carbon ratios and by physiological changes in Chl F associated with the silica limitation. A Lagrangian mixed-layer float and four Seagliders, operating continuously for 2 months, made similar measurements of the optical community index and followed the evolution and later demise of the diatom spring bloom. Temporal changes in optical community index and, by implication, the transition in community composition from diatom to post-diatom bloom communities were not simultaneous over the spatial domain surveyed by the ship, float and gliders. The ratio of simple optical properties measured from autonomous platforms, when carefully validated, provides a unique tool for studying phytoplankton patchiness on extended temporal scales and ecologically relevant spatial scales and should offer new insights into the processes regulating patchiness.

  4. Phytoplankton succession in the Ob-Yenisei Shallow zone of the Kara Sea based on Russian databases

    NASA Astrophysics Data System (ADS)

    Makarevich, P. R.; Larionov, V. V.; Moiseev, D. V.

    2015-07-01

    Here, data about the taxonomic composition and spatial distribution of planktonic microalgae in the Ob Bay and the southern Kara Sea in north Russia were analyzed during all hydrological seasons over 11 years (1996-2006). Data were obtained through detailed in situ observations. These data are part of our arctic phytoplankton database. Phytoplankton inhabiting the near shore continental area of the Kara Sea exhibited four phases in the annual succession cycle: a prevernal phase (cryoflora bloom), a vernal phase (ice-edge bloom), a summer-fall phase (mixed synthesis phase), and a winter phase (dormant phase). These phases were clearly differentiated based on the composition of dominant phytoplankton species complexes and quantitative characteristics (i.e., microalgal number and biomass). In the study region, which is completely covered by ice for most of the year (from October to June), the process of primary production begins at the same time as in ice-free coastal areas. Sub-ice blooming and growth of cryoflora initiate beneath the ice cover, long before it breaks down. In addition, from July to October, high phytoplankton biomass was recorded in Ob Bay and in areas adjacent to the Ob-Yenisei shallows. This information provides quantitative evidence for the higher productivity of waters off the Obestuary, compared to other coastal areas in the Kara Sea. The main factor responsible for this phenomenon is the permanent (during the warm season) transport of living and dead organic matter by river runoff to shelf waters.

  5. Phytoplankton and the Macondo oil spill: A comparison of the 2010 phytoplankton assemblage to baseline conditions on the Louisiana shelf.

    PubMed

    Parsons, M L; Morrison, W; Rabalais, N N; Turner, R E; Tyre, K N

    2015-12-01

    The Macondo oil spill was likely the largest oil spill to ever occur in United States territorial waters. We report herein our findings comparing the available baseline phytoplankton data from coastal waters west of the Mississippi River, and samples collected monthly from the same sampling stations, during and after the oil spill (May-October, 2010). Our results indicate that overall, the phytoplankton abundance was 85% lower in 2010 versus the baseline, and that the species composition of the phytoplankton community moved towards diatoms and cyanobacteria and away from ciliates and phytoflagellates. The results of this study reaffirm the view that phytoplankton responses will vary by the seasonal timing of the oil spill and the specific composition of the spilled oil. The trophic impacts of the purported lower abundance of phytoplankton in 2010 coupled with the observed assemblage shift remain unknown. PMID:26378966

  6. Phytoplankton. The fate of photons absorbed by phytoplankton in the global ocean.

    PubMed

    Lin, Hanzhi; Kuzminov, Fedor I; Park, Jisoo; Lee, SangHoon; Falkowski, Paul G; Gorbunov, Maxim Y

    2016-01-15

    Solar radiation absorbed by marine phytoplankton can follow three possible paths. By simultaneously measuring the quantum yields of photochemistry and chlorophyll fluorescence in situ, we calculate that, on average, ~60% of absorbed photons are converted to heat, only 35% are directed toward photochemical water splitting, and the rest are reemitted as fluorescence. The spatial pattern of fluorescence yields and lifetimes strongly suggests that photochemical energy conversion is physiologically limited by nutrients. Comparison of in situ fluorescence lifetimes with satellite retrievals of solar-induced fluorescence yields suggests that the mean values of the latter are generally representative of the photophysiological state of phytoplankton; however, the signal-to-noise ratio is unacceptably low in extremely oligotrophic regions, which constitute 30% of the open ocean. PMID:26743625

  7. Influences of sea ice on eastern Bering Sea phytoplankton

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    PubMed

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

    2015-03-01

    To study the distribution of phytoplankton and water quality of Beijiang River, the community structure of phytoplankton was investigated and analyzed in wet and dry seasons. The results showed that a total of 74 species belonging to six phyla, 29 family and 48 genera of phytoplankton were identified, including 58 species of five phyla, 23 family and 41 genera in wet season and 59 species of six phyla, 26 family and 40 genera in dry season. Phytoplankton community structure in Beijiang River was represented by Bacillariophyta, Chlorophyta and Cyanophyta. Bacillariophyta dominanted the phytoplankton, and the dominant species were Aulacoseira granulate, Fragilaria virescens, Surirella biseriata, Nitzschia amphibia, Navicula simplex, Cyclotella meneghiniana, Synedra ulna, Gomphonema angustatum and Cymbella tumida. There was little difference in phytoplankton density between both seasons with the mean values being 3.54 x 10(5) and 4.87 x 10(5) cells L(-1) in dry and wet seasons, respectively. Based on the RDA results, DO, permanganate index, nitrogen and phosphorus were the important environmental factors affecting the distribution of phytoplankton in Beijiang River. The water quality of Beijiang River was classified as oligo-mesotrophic level even if this river was subjected to nitrogen and phosphorus pollution mainly from agricultural non-point source. PMID:25929062

  9. Pigment signatures of phytoplankton communities in the Beaufort Sea

    NASA Astrophysics Data System (ADS)

    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.

  10. Pigment signatures of phytoplankton communities in the Beaufort Sea

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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 change 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 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 count 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. The inclusion in heterotrophic dinoflagellates 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 phytoplankton populations.

  11. Climate Variability and Phytoplankton in the Pacific Ocean

    NASA Technical Reports Server (NTRS)

    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 (p<0.01) with the Multivariate El Nino Southern Oscillation Index (MEI). In the North Central Pacific, MEI and chlorophyll were significantly (p<0.01) correlated along with two of the phytoplankton 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.

  12. Do high concentrations of microcystin prevent Daphnia control of phytoplankton?

    PubMed

    Chislock, Michael F; Sarnelle, Orlando; Jernigan, Lauren M; Wilson, Alan E

    2013-04-15

    Toxin-producing cyanobacteria have frequently been hypothesized to limit the ability of herbivorous zooplankton (such as Daphnia) to control phytoplankton biomass by inhibiting feeding, and in extreme cases, causing zooplankton mortality. Using limnocorral experiments in hyper-eutrophic ponds located in Alabama and Michigan (U.S.A.), we tested the hypothesis that high levels of cyanobacteria and microcystin, a class of hepatotoxins produced by several cyanobacterial genera, prevent Daphnia from strongly reducing phytoplankton abundance. At the start of the first experiment (Michigan), phytoplankton communities were dominated by toxic Microcystis and Anabaena (∼96% of total phytoplankton biomass), and concentrations of microcystin were ∼3 μg L⁻¹. Two weeks after adding Daphnia pulicaria from a nearby eutrophic lake, microcystin levels increased to ∼6.5 μg L⁻¹, yet Daphnia populations increased exponentially (r = 0.24 day⁻¹). By the third week, Daphnia had suppressed phytoplankton biomass by ∼74% relative to the no Daphnia controls and maintained reduced phytoplankton biomass until the conclusion of the five-week experiment. In the second experiment (Alabama), microcystin concentrations were greater than 100 μg L⁻¹, yet a mixture of three D. pulicaria clones from eutrophic lakes in southern MI increased and again reduced phytoplankton biomass, in this case by over 80%. The ability of Daphnia to increase in abundance and suppress phytoplankton biomass, despite high initial levels of cyanobacteria and microcystin, indicates that the latter does not prevent strong control of phytoplankton biomass by Daphnia genotypes that are adapted to environments with abundant cyanobacteria and associated cyanotoxins. PMID:23395484

  13. Free-living and particle-associated prokaryote metabolism in giant kelp forests: Implications for carbon flux in a sub-Antarctic coastal area

    NASA Astrophysics Data System (ADS)

    Schapira, Mathilde; McQuaid, Christopher D.; Froneman, Pierre W.

    2012-06-01

    Extensive beds of large subtidal kelps are characteristic of many temperate and subpolar coastlines. They provide habitats for a wide range of other species and are sites of high primary production that generate large quantities of water-borne particles and dissolved organic compounds that support distinctive communities of prokaryotes. We measured prokaryotic metabolism along transects from the shore to the outside of three giant kelp forests (Macrocystis pyrifera) located in the shelf waters of the Prince Edward Islands (Southern Ocean). Abundance, heterotrophic production (PHP), respiration rates (R-ETS) and growth efficiencies (PGE) were investigated within the particle-associated (PA) and the free-living (FL) communities. Temperature, salinity and inorganic nutrient concentrations indicated distinct hydrological differences among the kelp forests that were related to different levels of freshwater input through island run-off. In contrast, detritus and particulate organic matter concentrations showed a common pattern, decreasing from the near-shore to offshore at all sampling sites, suggesting the retention of organically enriched water masses inshore of the kelp forests. While FL and PA abundances did not differ significantly along transects, FL and PA-PHP and PGE all varied significantly across the kelp forests, following the same pattern across each forest. PA-PGE was significantly higher than FL-PGE in the near-shore waters and farther offshore, while FL-PGE was higher or equal to PA-PGE inside the kelp. This shift can be interpreted in terms of gradients in both the age and origins of organic material across the kelp forests. Higher PA-PGE implies that a larger fraction of organic carbon on colonized particles is converted into prokaryotic biomass and so becomes available to higher trophic levels inshore and offshore of M. pyrifera forests than inside the kelp bed. In contrast, low PA-PGE suggests that a large quantity of carbon passes through the PA

  14. The uptake and bioaccumulation of PCBs by phytoplankton

    SciTech Connect

    Swackhamer, D.L.; Skoglund, R.S.; Stange, K. )

    1990-01-01

    Phytoplankton play a major role in the fate and transport of hydrophobic organic compounds such as polychlorinated biphenyls (PCBs) due to their large biomass, their high lipid content, and their place as the primary step in the aquatic food web. Phytoplankton accumulate PCBs in the water column most likely as a result of water-lipid partitioning, and can pass the contaminants up through the food web by consumers or transport them to bottom waters by sedimentation. The process of PCB uptake and bioaccumulation by phytoplankton has been the focus of our study.

  15. Growth-irradiance relationships in phytoplankton

    SciTech Connect

    Falkowski, P.G.; Dubinsky, Z.; Wyman, K.

    1985-03-01

    The steady state growth rates of three species of marine phytoplankton, Thalassiosira weisflogii, Isochrysis galbana, and Prorocentrum micans, were followed in turbidostat culture. At each growth irradiance, photosynthesis and respiration were measured by following changes in oxygen. Together with measurements of optical absorption cross sections, cellular chlorophyll, carbon and nitrogen, and excretion rates as well as knowledge of the quantum flux, the quantum requirement for growth and photosynthesis were calculated. Our results suggest that variations in growth rate caused by changes in irradiance may be related to changes in respiration rates relative to growth as well as changes in optical absorption cross sections for a given species. Interspecific differences in growth rate at a given irradiance are not related to changes in respiration however, but are primarily attributable to differences in optical absorption cross sections normalized to chlorophyll and differences in chlorophyll:carbon ratios.

  16. Phytoplankton bloom in the Black Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Brightly colored waters in the Black Sea give evidence of the growth of tiny marine plants called phytoplankton, which contain chlorophyll and other pigments that reflect light different ways, producing the colorful displays. The very bright blue waters could be an organism called a coccolithophores, which has a highly reflective calcium carbonate coating that appears bright blue (or sometimes white) in true-color (visible) imagery. However, other organisms, such as cyanobacteria can also appear that color, and so often scientists will compare the ratios of reflectance at one wavelength of light to another to decide what organisms might be present. This series of images shows a bloom occurring in the Black Sea from May 11, 2002, to May 18.

  17. Phytoplankton community responses in a shallow lake following lanthanum-bentonite application.

    PubMed

    Lang, P; Meis, S; Procházková, L; Carvalho, L; Mackay, E B; Woods, H J; Pottie, J; Milne, I; Taylor, C; Maberly, S C; Spears, B M

    2016-06-15

    The release of phosphorus (P) from bed sediments to the overlying water can delay the recovery of lakes for decades following reductions in catchment contributions, preventing water quality targets being met within timeframes set out by environmental legislation (e.g. EU Water Framework Directive: WFD). Therefore supplementary solutions for restoring lakes have been explored, including the capping of sediment P sources using a lanthanum (La)-modified bentonite clay to reduce internal P loading and enhance the recovery process. Here we present results from Loch Flemington where the first long-term field trial documenting responses of phytoplankton community structure and abundance, and the UK WFD phytoplankton metric to a La-bentonite application was performed. A Before-After-Control-Impact (BACI) analysis was used to distinguish natural variability from treatment effect and confirmed significant reductions in the magnitude of summer cyanobacterial blooms in Loch Flemington, relative to the control site, following La-bentonite application. However this initial cyanobacterial response was not sustained beyond two years after application, which implied that the reduction in internal P loading was short-lived; several possible explanations for this are discussed. One reason is that this ecological quality indicator is sensitive to inter-annual variability in weather patterns, particularly summer rainfall and water temperature. Over the monitoring period, the phytoplankton community structure of Loch Flemington became less dominated by cyanobacteria and more functionally diverse. This resulted in continual improvements in the phytoplankton compositional and abundance metrics, which were not observed at the control site, and may suggest an ecological response to the sustained reduction in filterable reactive phosphorus (FRP) concentration following La-bentonite application. Overall, phytoplankton classification indicated that the lake moved from poor to moderate

  18. Synergistic effects of UVR and simulated stratification on commensalistic phytoplankton-bacteria relationship in two optically contrasting oligotrophic Mediterranean lakes

    NASA Astrophysics Data System (ADS)

    Carrillo, P.; Medina-Sánchez, J. M.; Durán, C.; Herrera, G.; Villafañe, V. E.; Helbling, E. W.

    2015-02-01

    An indirect effect of global warming is a reduction in the depth of the upper mixed layer (UML) causing organisms to be exposed to higher levels of ultraviolet (UVR, 280-400 nm) and photosynthetically active radiation (PAR, 400-700 nm). This can affect primary and bacterial production as well as the commensalistic phytoplankton-bacteria relationship. The combined effects of UVR and reduction in the depth of the UML were assessed on variables related to the metabolism of phytoplankton and bacteria, during in situ experiments performed with natural pico- and nanoplankton communities from two oligotrophic lakes with contrasting UVR transparency (high-UVR versus low-UVR waters) of southern Spain. The negative UVR effects on epilimnetic primary production (PP) and on heterotrophic bacterial production (HBP), intensified under increased stratification, were higher in the low-UVR than in the high-UVR lake, and stronger on the phytoplanktonic than on the heterotrophic bacterial communities. Under UVR and increased stratification, the commensalistic phytoplankton-bacteria relationship was strengthened in the high-UVR lake where excretion of organic carbon (EOC) rates exceeded the bacterial carbon demand (BCD; i.e., BCD : EOC(%) ratio < 100). This did not occur in the low-UVR lake (i.e., BCD : EOC(%) ratio > 100). The greater UVR damage to phytoplankton and bacteria and the weakening of their commensalistic interaction found in the low-UVR lake indicates that these ecosystems would be especially vulnerable to UVR and increased stratification as stressors related to global climate change. Thus, our findings may have important implications for the carbon cycle in oligotrophic lakes of the Mediterranean region.

  19. PHYTOPLANKTON COMPOSITION AND ABUNDANCE IN SOUTHERN LAKE HURON

    EPA Science Inventory

    Southern Lake Huron contains a diversity of phytoplankton assemblage types ranging from assemblages characteristic of oligotrophic waters to those which usually occur under highly eutrophic conditions. The offshore waters are generally characterized by oligotrophic associations a...

  20. Turbulent mixing, restratification, and phytoplankton growth at a submesoscale eddy

    NASA Astrophysics Data System (ADS)

    Taylor, J. R.

    2016-06-01

    High-resolution large-eddy simulations are used to study the influence of submesoscale mixed layer instability and small-scale turbulence on phytoplankton growth in light-limited conditions. Four simulations are considered with small-scale turbulence driven by varying levels of surface cooling. Significant small-scale turbulence is seen even without surface forcing, and the downward mixing of phytoplankton is sufficient to briefly delay the developing bloom. Moderate and strong values of the constant surface heat flux (Q =- 10,-100 W/m2) are sufficient to prevent a bloom. In contrast to the critical depth hypothesis, the growth rate for phytoplankton does not appear to be controlled by the mixed layer depth. Instead, a comparison between the turbulent diffusivity above the compensation depth and a critical value predicted by the critical turbulence hypothesis closely matches the timing and magnitude of phytoplankton growth.

  1. Strong responses of Southern Ocean phytoplankton communities to volcanic ash

    NASA Astrophysics Data System (ADS)

    Browning, T. J.; Bouman, H. A.; Henderson, G. M.; Mather, T. A.; Pyle, D. M.; Schlosser, C.; Woodward, E. M. S.; Moore, C. M.

    2014-04-01

    Volcanic eruptions have been hypothesized as an iron supply mechanism for phytoplankton blooms; however, little direct evidence of stimulatory responses has been obtained in the field. Here we present the results of twenty-one 1-2 day bottle enrichment experiments from cruises in the South Atlantic and Southern Ocean which conclusively demonstrated a photophysiological and biomass stimulation of phytoplankton communities following supply of basaltic or rhyolitic volcanic ash. Furthermore, experiments in the Southern Ocean demonstrated significant phytoplankton community responses to volcanic ash supply in the absence of responses to addition of dissolved iron alone. At these sites, dissolved manganese concentrations were among the lowest ever measured in seawater, and we therefore suggest that the enhanced response to ash may have been a result of the relief of manganese (co)limitation. Our results imply that volcanic ash deposition events could trigger extensive phytoplankton blooms, potentially capable of significant impacts on regional carbon cycling.

  2. Satellite Observations: Oil Spills Impact on Phytoplankton in Bohai Sea

    NASA Astrophysics Data System (ADS)

    Zhou, Li; Tang, Danling; Wang, Sufen; Pan, Gang

    2014-11-01

    This study discussed ecological responses to the Penglai oil spills in the Bohai Sea, occurring on June 4, 2011, using MODIS Chlorophyll-a data. After time intervals of 20 days, 12 months and 14 months, phytoplankton blooms appeared at three locations in the surrounding and distant regions of the oil spills in the Bohai Sea. A bloom with high Chlorophyll-a (13.66 mg m-3) spread over an area of 800 km2 on June 18-25, 2011, about 56 km northeast from the location of the oil spills. A pronounced increase in the monthly Chlorophyll-a concentration (6.40 mg m-3) indicating phytoplankton bloom was observed in the Bohai Sea in June 2012. Phytoplankton blooms depend on the amount and composition of oil, toxicity of petroleum hydrocarbons, micro-organisms, and sea ice. The oil spills impact phytoplankton for a long duration, which impacts the marine ecosystem.

  3. Tidal stirring and phytoplankton bloom dynamics in an estuary

    USGS Publications Warehouse

    Cloern, J.E.

    1991-01-01

    In South San Francisco Bay, estuarine phytoplankton biomass fluctuates at the time scale of days to weeks; much of this variability is associated with fluctuations in tidal energy. During the spring seasons of every year from 1980-1990, episodic blooms occurred in which phytoplankton biomass rose from a baseline of 2-4mg chlorophyll a m-3, peaked at 20-40 chlorophyll a m-3, then returned to baseline values, all within several weeks. Each episode of biomass increase occurred during neap tides, and each bloom decline coincided with spring tides. This suggests that daily variations in the rate of vertical mixing by tidal stirring might control phytoplankton bloom dynamics in some estuaries. Simulation experiments with a numerical model of phytoplankton population dynamics support this hypothesis. -from Author

  4. Nutrient limitation of phytoplankton growth in Georgia nearshore waters

    SciTech Connect

    Bishop, S.S.; Emmanuele, K.A.; Yoder, J.A.

    1984-12-01

    Nutrient enrichment experiments were conducted to investigate the utilization of dissolved organic (DON) and inorganic nitrogen (DIN) by marine phytoplankton in Georgia coastal waters. Natural populations of marine phytoplankton, enriched with different concentrations of ammonium chloride and other plant nutrients, were grown under controlled temperature and irradiance conditions until the populations reached ''stationary phase.'' Results showed that (1) phytoplankton are limited by DIN up to ca. 20 ..mu..M, when another nutrient (phosphate or silicate) becomes limiting, (2) very little naturally-occuring DON is directly utilized for growth, (3) very little DON is indirectly made available for growth over time periods of days to ca. 1 week, and (4) trace metals and vitamins do not significantly limit phytoplankton growth.

  5. Ultrafast quantitative time-stretch imaging flow cytometry of phytoplankton

    NASA Astrophysics Data System (ADS)

    Lai, Queenie T. K.; Lau, Andy K. S.; Tang, Anson H. L.; Wong, Kenneth K. Y.; Tsia, Kevin K.

    2016-03-01

    Comprehensive quantification of phytoplankton abundance, sizes and other parameters, e.g. biomasses, has been an important, yet daunting task in aquatic sciences and biofuel research. It is primarily because of the lack of effective tool to image and thus accurately profile individual microalgae in a large population. The phytoplankton species are highly diversified and heterogeneous in terms of their sizes and the richness in morphological complexity. This fact makes time-stretch imaging, a new ultrafast real-time optical imaging technology, particularly suitable for ultralarge-scale taxonomic classification of phytoplankton together with quantitative image recognition and analysis. We here demonstrate quantitative imaging flow cytometry of single phytoplankton based on quantitative asymmetric-detection time-stretch optical microscopy (Q-ATOM) - a new time-stretch imaging modality for label-free quantitative phase imaging without interferometric implementations. Sharing the similar concept of Schlieren imaging, Q-ATOM accesses multiple phase-gradient contrasts of each single phytoplankton, from which the quantitative phase profile is computed. We employ such system to capture, at an imaging line-scan rate of 11.6 MHz, high-resolution images of two phytoplankton populations (scenedesmus and chlamydomonas) in ultrafast microfluidic flow (3 m/s). We further perform quantitative taxonomic screening analysis enabled by this technique. More importantly, the system can also generate quantitative phase images of single phytoplankton. This is especially useful for label-free quantification of biomasses (e.g. lipid droplets) of the particular species of interest - an important task adopted in biofuel applications. Combining machine learning for automated classification, Q-ATOM could be an attractive platform for continuous and real-time ultralarge-scale single-phytoplankton analysis.

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

    PubMed Central

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

    2011-01-01

    Although the consequences of global warming in aquatic ecosystems are only beginning to be revealed, a key to forecasting the impact on aquatic communities is an understanding of individual species' vulnerability to increased temperature. Despite their microscopic size, phytoplankton support about half of the global primary production, drive essential biogeochemical cycles and represent the basis of the aquatic food web. At present, it is known that phytoplankton are important targets and, consequently, harbingers of climate change in aquatic systems. Therefore, investigating the capacity of phytoplankton to adapt to the predicted warming has become a relevant issue. However, considering the polyphyletic complexity of the phytoplankton community, different responses to increased temperature are expected. We experimentally tested the effects of warming on 12 species of phytoplankton isolated from a variety of environments by using a mechanistic approach able to assess evolutionary adaptation (the so-called ratchet technique). We found different degrees of tolerance to temperature rises and an interspecific capacity for genetic adaptation. The thermal resistance level reached by each species is discussed in relation to their respective original habitats. Our study additionally provides evidence on the most resistant phytoplankton groups in a future warming scenario. PMID:21508031

  7. Amplified Arctic warming by phytoplankton under greenhouse warming.

    PubMed

    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. PMID:25902494

  8. Numerical Simulation of phytoplankton productivity in partially mixed estuaries

    USGS Publications Warehouse

    Peterson, D.H.; Festa, J.F.

    1984-01-01

    A two-dimensional steady-state model of light-driven phytoplankton productivity and biomass in partially mixed estuaries has been developed. Effects of variations in river flow, suspended sediment concentration, phytoplankton sinking, self-shading and growth rates on distributions of phytoplankton biomass and productivity are investigated. Numerical simulation experiments show that biomass and productivity are particularly sensitive to variations in suspended sediment concentrations typical of natural river sources and to variations in loss rates assumed to be realistic but poorly known for real systems. Changes in the loss rate term within the range of empirical error (such as from dark bottle incubation experiments) cause phytoplankton biomass to change by a factor of two. In estuaries with adequate light penetration in the water column, it could be an advantage for phytoplankton to sink. Species that sink increase their concentration and form a phytoplankton maximum in a way similar to the formation of the estuarine turbidity maximum. When attenuation is severe, however, sinking species have more difficulty in maintaining their population. ?? 1984.

  9. Winter-spring phytoplankton blooms in Dabob Bay, Washington

    NASA Astrophysics Data System (ADS)

    Horner, Rita A.; Postel, James R.; Halsband-Lenk, Claudia; Pierson, James J.; Pohnert, Georg; Wichard, Thomas

    2005-11-01

    Scientific investigations in Dabob Bay, Washington State, USA, have been extensive since the early 1960s, but phytoplankton blooms have been studied mostly with regard to chlorophyll concentrations and little is known about the phytoplankton species themselves. Here we provide information on the species present, their abundances during blooms, their contribution to organic carbon concentrations and the ability of some phytoplankton species to produce toxic aldehydes that may impact metazoan grazers. Multiple blooms of phytoplankton, dominated by diatoms, occurred in the late winter-early spring period, with depth-integrated chlorophyll levels ranging from <20 to 230 mg m -2 and peaks in February and April. The major bloom species included Skeletonema costatum, Thalassiosira spp. and Chaetoceros spp; Phaeocystis cf. pouchetii occurred in 2002 and 2004. Other taxa or groups of organisms that were sometimes abundant included unidentified small flagellates <10 μm in size and unidentified heterotrophic dinoflagellates. Large diatoms usually comprised most of the cell carbon, but a large, heterotrophic dinoflagellate, identified only as Gyrodinium “tear” because of its shape, was a major contributor to the microplankton carbon when present even in small numbers. Five Thalassiosira species and S. costatum were found to produce polyunsaturated aldehydes (PUA) that are known to affect copepod reproduction and hatching success. Our findings are similar to the few previous studies in the last four decades that included phytoplankton species and suggest long-term similarities and relative stability in the phytoplankton species present and their timing in Dabob Bay.

  10. Amplified Arctic warming by phytoplankton under greenhouse warming

    PubMed Central

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

    2015-01-01

    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. PMID:25902494

  11. Links between phytoplankton, CO2 emissions and water properties

    NASA Astrophysics Data System (ADS)

    Oliveira, A. P.; Cabeçadas, L.

    2009-04-01

    Changes in seawater chemistry already emerging in Portuguese coastal waters and trends predicted by the end of the century, might cause shifts in current algal communities and alter the structure and biodiversity of coastal ecosystems. May 2002 sampling in Tagus and Sado estuaries adjacent coastal shelf (SW Portugal) was an example of that. This period was characterized by a moderate but persistent upwelling and low Tagus river discharge (46 m3 s-1) favouring a weak plume and elevatedpCO2 values. These conditions strongly influenced the phytoplankton community. The spring bloom occurred at Tagus plume and close to Lisbon Canyon, where large sized phytoplankton, dominated by chain-forming diatoms, reached values up to 1000cells ml-1, while dinoflagellates reached a local peak over the canyon (>20 cells ml-1). Spatially differentiated from the main phytoplankton bloom, a development of the intermediate sized species Coccolithus braarudii (up to 60 cells ml-1) occurred, associated with the thermally stratified water-mass localised in Tagus Bay. While diatoms proliferated throughout turbulent waters, coccolithophores developed under more stable conditions, being not directly affected by anthropogenic inputs and associated with relatively low nutrient levels. The same trend was also observed for the small sized phytoplankton, which abundance (>106 cells ml-1) increased from inshore to the deeper surface mixed layer offshore where light was dimmer and nutrient concentrations lower. The small sized phytoplankton was made up of cyanobacteria Synechococcus-like and eukaryotes reaching, respectively, 721 and 466 cells ml-1. Regarding the relative importance of each phytoplankton size group in terms of carbon, cocolithophores and small sized phytoplankton represented, respectively, 2% and 0.2% of the total phytoplankton biomass. Despite the low percentage in terms of particulate organic carbon, cocolithophores played an important role in terms of CaCO3 and CO2. It was

  12. Changing restoration rules: exotic bivalves interact with residence time and depth to control phytoplankton productivity

    USGS Publications Warehouse

    Lucas, Lisa V.; Thompson, Janet K.

    2012-01-01

    Non-native species are a prevalent ecosystem stressor that can interact with other stressors to confound resource management and restoration. We examine how interactions between physical habitat attributes and a particular category of non-native species (invasive bivalves) influence primary production in aquatic ecosystems. Using mathematical models, we show how intuitive relationships between phytoplankton productivity and controllable physical factors (water depth, hydraulic transport time) that hold in the absence of bivalves can be complicated—and even reversed—by rapid bivalve grazing. In light-limited environments without bivalves, shallow, hydrodynamically “slow” habitats should generally have greater phytoplankton biomass and productivity than deeper, “faster” habitats. But shallower, slower environments can be less productive than deeper, faster ones if benthic grazing is strong. Moreover, shallower and slower waters exhibit a particularly broad range of possible productivity outcomes that can depend on whether bivalves are present. Since it is difficult to predict the response of non-native bivalves to habitat restoration, outcomes for new shallow, slow environments can be highly uncertain. Habitat depth and transport time should therefore not be used as indicators of phytoplankton biomass and production where bivalve colonization is possible. This study provides for ecosystem management a particular example of a broad lesson: abiotic ecosystem stressors should be managed with explicit consideration of interactions with other major (including biotic) stressors. We discuss the applicability and management implications of our models and results for a range of aquatic system types, with a case study focused on the Sacramento-San Joaquin Delta (California, USA). Simple mathematical models like those used here can illuminate interactions between ecosystem stressors and provide process-based guidance for resource managers as they develop strategies

  13. Infection of phytoplankton by aerosolized marine viruses.

    PubMed

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

    2015-05-26

    Marine viruses constitute a major ecological and evolutionary driving force in the marine ecosystems. However, their dispersal mechanisms remain underexplored. Here we follow the dynamics of Emiliania huxleyi viruses (EhV) that infect the ubiquitous, bloom-forming phytoplankton E. huxleyi and show that EhV are emitted to the atmosphere as primary marine aerosols. Using a laboratory-based setup, we showed that the dynamic of EhV aerial emission is strongly coupled to the host-virus dynamic in the culture media. In addition, we recovered EhV DNA from atmospheric samples collected over an E. huxleyi bloom in the North Atlantic, providing evidence for aerosolization of marine viruses in their natural environment. Decay rate analysis in the laboratory revealed that aerosolized viruses can remain infective under meteorological conditions prevailing during E. huxleyi blooms in the ocean, allowing potential dispersal and infectivity over hundreds of kilometers. Based on the combined laboratory and in situ findings, we propose that atmospheric transport of EhV is an effective transmission mechanism for spreading viral infection over large areas in the ocean. This transmission mechanism may also have an important ecological impact on the large-scale host-virus "arms race" during bloom succession and consequently the turnover of carbon in the ocean. PMID:25964340

  14. Phytoplankton bloom in Spencer Gulf, South Australia

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Summer in southern Australia is the dry season, and in this true-color MODIS image of South Australia and the Spencer Gulf from October 20,2001, the area's vegetation is losing much of the lushness it possessed in the winter rainy season (See image from September 19, 2001). In southern hemisphere summer, the high pressure systems that dominate the continent's weather move south, and block the rain-bearing westerly winds. The resulting changes in seasonal rainfall are extreme. Many of the rivers are impermanent, and flow into dry or impermanent salt lakes, such as Lake Torrens (long, thin lake bed, roughly in the center of the image), and Lake Eyre (pink and white lake bed to the northwest of Torrens). Between the Eyre Peninsula (lower left) and the Yorke Peninsula further east lies the Spencer Gulf, showing the blue-green swirls that indicate a phytoplankton bloom. Australia gets less rainfall than any continent except Antarctica, and the low and seasonal flows contribute to problems with salinity and algal blooms in the continent's surface waters.

  15. Phytoplankton bloom in Spencer Gulf, Southern Australia

    NASA Technical Reports Server (NTRS)

    2002-01-01

    South Australia occupies the center of the Australian continent. The deserts of the interior give way to more fertile land along the coast of the Southern Ocean. This true-color MODIS image from September 17, 2001, shows the marked contrast between the country's arid interior--where seasonal salt lakes stand out in white against the deserts' vast, red expanse--and the coastal regions, including Spencer Gulf, to the lower left of the image's center. The characteristic blue-green swirls of a phytoplankton bloom can be seen in the Gulf and southeastward along the coast. To Spencer Gulf's east, the brownish-gray pixels on the eastern coast of the Gulf of St. Vincent indicate the location of the city of Adelaide, the region's capital. The large dark areas that stand out amid the green vegetation do not indicate areas where vegetation had been damaged or burned. In fact, the opposite is actually true. In many cases, those areas are land protected by national and state parks and preserves, where the natural vegetation of the semi-arid landscape is allowed to exist undisturbed. For example, due east of Adelaide are Billiat Conservation Park and the semi-rectangular Murray Sunset National Park, which is across the border from South Australia in Victoria. South of those parks are the parks of the Big Desert (top) and Little Desert (bottom).

  16. Infection of phytoplankton by aerosolized marine viruses

    PubMed Central

    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

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

    PubMed

    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). PMID:26987085

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

    NASA Technical Reports Server (NTRS)

    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.

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

    USGS Publications Warehouse

    Cloern, J.E.; Dufford, R.

    2005-01-01

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

  20. Phytoplankton Diversity and Geologically Relevant Carbon: Using metagenomics to determine phytoplankton biomarker production

    NASA Astrophysics Data System (ADS)

    Kodner, R. B.; Armbrust, E.

    2008-12-01

    Phytoplankton play an important role in the global carbon cycle, on short and long time scales. On long time scales, organic carbon, especially recalcitrant forms of biomass such as lipids, can be preserved and thus sequestered in sediments and rocks on geologic time scales. If the preserved lipids have some taxonomic specificity, they can be used as fossil biomarkers to characterize the community of organisms that contributed to ancient carbon sinks. Currently, it is not well understood how well the complex mixture of organic compounds preserved in geological carbon sinks represents the original community that produced those molecules or how the diversity of organism in a community is reflected in the lipid biomarkers they collectively synthesize. We have begun to investigate these questions by characterizing lipid biomarker production in modern phytoplankton communities with metagenomic data sets. Here we evaluate the information on community biomarker biosynthesis gathered from this type of data set using sterols as a case study. We have identified genes involved in sterol biosynthesis in a number of metagenomes and placed these genes in a phylogenetic context using a method designed to deal with short metagenomic sequences. The degree of taxonomic diversity of biomarker production measured with gene sequences can be more specific than lipid analysis alone.

  1. Assisted Living

    MedlinePlus

    ... but they don't need full-time nursing care. Some assisted living facilities are part of retirement ... change. Assisted living costs less than nursing home care. It is still fairly expensive. Older people or ...

  2. Phytoplankton productivity in a turbid buoyant coastal plume

    NASA Astrophysics Data System (ADS)

    Schofield, Oscar; Moline, Mark; Cahill, Brownyn; Frazer, Thomas; Kahl, Alex; Oliver, Matthew; Reinfelder, John; Glenn, Scott; Chant, Robert

    2013-07-01

    The complex dynamics associated with coastal buoyant plumes make it difficult to document the interactions between light availability, phytoplankton carbon fixation, and biomass accumulation. Using real-time data, provided by satellites and high frequency radar, we adaptively sampled a low salinity parcel of water that was exported from the Hudson river estuary in April 2005. The water was characterized by high nutrients and high chlorophyll concentrations. The majority of the low salinity water was re-circulated within a nearshore surface feature for 5 days during which nitrate concentrations dropped 7-fold, the maximum quantum yield for photosynthesis dropped 10-fold, and primary productivity rates decreased 5-fold. Associated with the decline in nitrate was an increase in phytoplankton biomass. The phytoplankton combined with the Colored Dissolved Organic Matter (CDOM) and non-algal particles attenuated the light so the 1% light level ranged between 3 and 10m depending on the age of the plume water. As the plume was 10-15m thick, the majority of the phytoplankton were light-limited. Vertical mixing within the plume was high as indicated by the dispersion of injected of rhodamine dye. The mixing within the buoyant plume was more rapid than phytoplankton photoacclimation processes. Mixing rates within the plume was the critical factor determining overall productivity rates within the turbid plume.

  3. Application of a laser fluorometer for discriminating phytoplankton species

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

    Mincer, Tracy J.; Aicher, Athena C.

    2016-01-01

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

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

    PubMed

    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

  6. Discrimination and analysis of phytoplankton using a microfluidic cytometer.

    PubMed

    Benazzi, G; Holmes, D; Sun, T; Mowlem, M C; Morgan, H

    2007-12-01

    Identification and analysis of phytoplankton is important for understanding the environmental parameters that are influenced by the oceans, including pollution and climate change. Phytoplanktons are studied at the single cell level using conventional light-field and fluorescence microscopy, but the technique is labour intensive. Flow cytometry enables rapid and quantitative measurements of single cells and is now used as an analytical tool in phytoplankton analysis. However, it has a number of drawbacks, including high cost and portability. We describe the fabrication of a microfluidic (lab-on-a-chip) device for high-speed analysis of single phytoplankton. The device measures fluorescence (at three wavelength ranges) and the electrical impedance of single particles. The system was tested using a mixture of three algae (Isochrysis Galbana, Rhodosorus m., Synechococcus sp.) and the results compared with predictions from theory and measurements using a commercial flow cytometer (BD FACSAria). It is shown that the microfluidic flow cytometer is able to distinguish and characterise these different taxa and that impedance spectroscopy enables measurement of phytoplankton biophysical properties. PMID:18035910

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

    PubMed Central

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

    2013-01-01

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

  8. Effects of simulated increased gravity on the rate of aging of rats - Implications for the rate of living theory of aging

    NASA Technical Reports Server (NTRS)

    Economos, A. C.; Ballard, R. C.; Blunden, M.; Miquel, J.; Lindseth, K. A.; Fleming, J.; Philpott, D. E.; Oyama, J.

    1982-01-01

    It was found that the rate of aging of 17 month old rats which had been exposed to 3.14 times normal gravity in an animal centrifuge for 8 months was larger than that of the controls as determined by the apparently elevated lipofuscin content in heart and kidney, reduced numbers and increased size of mitochondria of heart tissue, and inferior liver mitochondria respiration. Steady-state food intake per day per kg body weight, which is presumably proportional to rate of living or specific basal metabolic expenditure, was found to be about 18 percent higher than in the controls after an initial 2 month adaptation period. Although half of the centrifuged animals lived only a little shorter than the controls (average about 343 vs. 364 days on the average, statistically nonsignificant), the remaining half (longest survivors) lived on the centrifuge an average of 520 days (range 483-572) compared to an average of 574 days (range 502-615) for the controls, computed from the onset of centrifugation, or 11 percent shorter. These findings indicate that a moderate increase of the level of basal metabolism of young adult rats adapted to hypergravity compared to controls in normal gravity is accompanied by a roughly similar increase in the rate of organ aging and reduction of survival, in agreement with Pearl's (1928) rate of living theory of aging, previously experimentally demonstrated only in poikilotherms.

  9. Stigmatizing Attitudes towards People Living with HIV/AIDS among College Students in China: Implications for HIV/AIDS Education and Prevention

    ERIC Educational Resources Information Center

    Zhang, Liying; Li, Xiaoming; Mao, Rong; Stanton, Bonita; Zhao, Qun; Wang, Bo; Mathur, Ambika

    2008-01-01

    Purpose: The purpose of this paper is to show that HIV/AIDS-related stigma has persisted world-wide for decades. However, studies on the linkage between stigmatizing attitudes towards people living with HIV/AIDS (PLWHA) and misconceptions about HIV transmission routes in the general population, especially among youth in China, are sparse--a gap…

  10. Estimating phytoplankton photosynthesis by active fluorescence

    SciTech Connect

    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.

  11. Estimating phytoplankton photosynthesis by active fluorescence

    SciTech Connect

    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.

  12. Microbial biomarkers from the East China Sea and implications for paleoenvironmental reconstructions

    NASA Astrophysics Data System (ADS)

    Zhao, M.; Hu, W. J.; Duan, S. S.; Cao, L. Y.; Wang, Y. Y.; Zhao, S. Z.; Xing, L.

    2015-12-01

    We report the vertical and spatial distributions of isoprenoid glycerol dibiphytanyl glycerol tetraethers (GDGTs), ladderanes and phytoplankton biomarkers in suspended particulates from the East China Sea (ECS) to evaluate the living habitat and environments of the planktonic archaea Thaumarchaeota and anaerobic ammonium oxidation (anammox) bacteria, respectively. Maximum GDGT concentration mostly occurred in bottom waters while maximum phytoplankton biomarker concentration occurred in the surface layers; and these results from the ECS provides further evidence for the use of the TEX86 index as a proxy for bottom water temperature in shallow shelf sea environments. Ladderanes were detected in both surface and subsurface particulates, suggesting that anammox activity was widespread in both the hypoxia zone near the Changjiang Estuary and in the mid-shelf of the ECS. Thus, anaerobic condition is not a requirement for anammox bacteria; however, ladderane-derived anammox activity was higher in lower oxygen environments, confirming ladderanes as useful proxies for reconstructing hypoxia changes. Statistical analysis will be presented to assess the link between archaea (Thaumarchaeota) performing aerobic ammonia oxidation and bacteria (anammox) performing anaerobic ammonium oxidation in the ECS, the implications for both carbon and nitrogen cycles.

  13. 'Faking til you make it': social capital accumulation of individuals on low incomes living in contrasting socio-economic neighbourhoods and its implications for health and wellbeing.

    PubMed

    Browne-Yung, Kathryn; Ziersch, Anna; Baum, Fran

    2013-05-01

    People on low-income living in low socio-economic neighbourhoods have poorer health in comparison with those living in advantaged neighbourhoods. To explore neighbourhood effects on health and social capital creation, the experiences of low-income people living in contrasting socio-economic neighbourhoods were compared, in order to examine how low-income status and differing levels of neighbourhood resources contributed to perceived health and wellbeing. Quantitative and qualitative data were analysed: survey data from 601 individuals living in contrasting socio-economic areas and in-depth interviews with a new sample of 24 individuals on low-incomes. The study was guided by Bourdieu's theory of practice, which examines how social inequalities are created and reproduced through the relationship between individuals' varying resources of economic, social and cultural capital. This included an examination of individual life histories, cultural distinction and how social positions are reproduced. Participants' accounts of their early life experience showed how parental socio-economic position and socially patterned events taking place across the life course, created different opportunities for social network creation, choice of neighbourhood and levels of resources available throughout life, all of which can influence health and wellbeing. A definition of poverty by whether an individual or household has sufficient income at a particular point in time was an inadequate measure of disadvantage. This static measure of 'low income' as a category disguised a number of different ways in which disadvantage was experienced or, conversely, how life course events could mitigate the impact of low-income. This study found that the resources necessary to create social capital such as cultural capital and the ability to socially network, differed according to the socio-economic status of the neighbourhood, and that living in an advantaged area does not automatically guarantee

  14. REMOTE MEASUREMENT OF PHYTOPLANKTON PIGMENTS IN THE PAMLICO SOUND, NC USING HYPERSPECTRAL IMAGERY

    EPA Science Inventory

    Monitoring of phytoplankton concentrations in estuarine environments is important for managing both recreational and commercial fishery resources. Impacts on estuarine areas from phytoplankton blooms include neurotoxic shellfish poisoning; fish, bird, and vegetation kills; and p...

  15. MARYLAND/VIRGINIA CHESAPEAKE BAY AND TRIBUTARIES PHYTOPLANKTON TAXONOMIC COUNT FILES (AND RELATED EVENT FILES)

    EPA Science Inventory

    As part of the Chesapeake Bay program Phytoplankton data has been collected by the Maryland Department of the Environment /Maryland Department of Natural Resources and the Virginia Department of Environmental Quality. Available datasets include: 1) Maryland Phytoplankton Taxonom...

  16. Phytoplankton Community Structure, Biomass and Diversity on the Louisiana Continental Shelf

    EPA Science Inventory

    Phytoplankton communities on the Louisiana continental shelf (LCS) respond to nutrient loading from the Mississippi and Atchafalaya River Basin (MARB). Enhanced phytoplankton biomass is a source of organic matter contributing to the development of seasonal hypoxia. Samples were ...

  17. Metal contents of phytoplankton and labile particulate material in the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Twining, Benjamin S.; Rauschenberg, Sara; Morton, Peter L.; Vogt, Stefan

    2015-09-01

    quotas are in-line with those measured in laboratory cultures at comparable Fe concentrations. Particulate Zn, Cu, Ni, and Co are primarily associated with cellular material, but less than 30% of labile particulate Fe and Mn are biogenic. Particulate Al was primarily associated with lithogenic material, but the labile fraction was highly correlated with P, as well as with biogenic silica, suggesting that some particulate Al (perhaps around 20%) may occur adsorbed to biogenic material. Cellular element maps indicate that externally scavenged Fe was not a significant fraction of the metal associated with live phytoplankton, but adsorbed or precipitated phases are likely to be important in particulate detrital material. Such abiotic scavenging, along with differential remineralization of cellular nutrients in the water column, results in estimates of cellular metal/nutrient ratios from dissolved concentrations that significantly underestimate the ratios in phytoplankton. These data demonstrate the response of phytoplankton to the unique metal inputs to the North Atlantic Ocean.

  18. β-Decay Half-Lives of 110 Neutron-Rich Nuclei across the N=82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process.

    PubMed

    Lorusso, G; Nishimura, S; Xu, Z Y; Jungclaus, A; Shimizu, Y; Simpson, G S; Söderström, P-A; Watanabe, H; Browne, F; Doornenbal, P; Gey, G; Jung, H S; Meyer, B; Sumikama, T; Taprogge, J; Vajta, Zs; Wu, J; Baba, H; Benzoni, G; Chae, K Y; Crespi, F C L; Fukuda, N; Gernhäuser, R; Inabe, N; Isobe, T; Kajino, T; Kameda, D; Kim, G D; Kim, Y-K; Kojouharov, I; Kondev, F G; Kubo, T; Kurz, N; Kwon, Y K; Lane, G J; Li, Z; Montaner-Pizá, A; Moschner, K; Naqvi, F; Niikura, M; Nishibata, H; Odahara, A; Orlandi, R; Patel, Z; Podolyák, Zs; Sakurai, H; Schaffner, H; Schury, P; Shibagaki, S; Steiger, K; Suzuki, H; Takeda, H; Wendt, A; Yagi, A; Yoshinaga, K

    2015-05-15

    The β-decay half-lives of 110 neutron-rich isotopes of the elements from _{37}Rb to _{50}Sn were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for r-process calculations and reinforce the notion that the second (A≈130) and the rare-earth-element (A≈160) abundance peaks may result from the freeze-out of an (n,γ)⇄(γ,n) equilibrium. In such an equilibrium, the new half-lives are important factors determining the abundance of rare-earth elements, and allow for a more reliable discussion of the r process universality. It is anticipated that universality may not extend to the elements Sn, Sb, I, and Cs, making the detection of these elements in metal-poor stars of the utmost importance to determine the exact conditions of individual r-process events. PMID:26024165

  19. Phytoplankton photocompensation from space-based fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Morrison, J. Ruairidh; Goodwin, Deborah S.

    2010-03-01

    Recent satellite-derived observations linked global scale phytoplankton fluorescence variability with iron stress and hinted at photophysiological responses associated with changing light levels. These photocompensation reactions, the sum of photoacclimation and photoadaptation, were examined with climatological data for the Gulf of Maine. Significant seasonal variability was observed in the fluorescence quantum yield that was unrelated to patterns of biomass. Up to 89% of the variability in the fluorescence quantum yield was explained by a physiology-based photocompensation model. Spatial variability in seasonal patterns was associated with differing hydrodynamic regimes. This variability in the quantum yield demonstrates that satellite-based fluorescence is inappropriate for phytoplankton biomass determinations. More importantly, the work presented here provides the modeling foundation for fluorescence-based investigations of temporal and spatial variability in phytoplankton physiology associated with growth irradiance. These space-based physiological observations have the potential to decrease uncertainties in future ocean color derived primary productivity estimates.

  20. The paradox of enrichment in phytoplankton by induced competitive interactions.

    PubMed

    Tubay, Jerrold M; Ito, Hiromu; Uehara, Takashi; Kakishima, Satoshi; Morita, Satoru; Togashi, Tatsuya; Tainaka, Kei-ichi; Niraula, Mohan P; Casareto, Beatriz E; Suzuki, Yoshimi; Yoshimura, Jin

    2013-01-01

    The biodiversity loss of phytoplankton with eutrophication has been reported in many aquatic ecosystems, e.g., water pollution and red tides. This phenomenon seems similar, but different from the paradox of enrichment via trophic interactions, e.g., predator-prey systems. We here propose the paradox of enrichment by induced competitive interactions using multiple contact process (a lattice Lotka-Volterra competition model). Simulation results demonstrate how eutrophication invokes more competitions in a competitive ecosystem resulting in the loss of phytoplankton diversity in ecological time. The paradox is enhanced under local interactions, indicating that the limited dispersal of phytoplankton reduces interspecific competition greatly. Thus, the paradox of enrichment appears when eutrophication destroys an ecosystem either by elevated interspecific competition within a trophic level and/or destabilization by trophic interactions. Unless eutrophication due to human activities is ceased, the world's aquatic ecosystems will be at risk. PMID:24089056

  1. Laboratory studies of in vivo fluorescence of phytoplankton

    NASA Technical Reports Server (NTRS)

    Brown, C. A., Jr.; Farmer, F. H.; Jarrett, O., Jr.; Staton, W. L.

    1978-01-01

    A lidar system is developed that uses four selected excitation wavelengths to induce chlorophyll 'a' fluorescence which is indicative of both the concentration and diversity of phytoplankton. The operating principles of the system and the results of measurements of phytoplankton fluorescence in a controlled laboratory environment are presented. A comparative study of results from lidar fluorosensor laboratory tank tests using representative species of phytoplankton in single and multispecies cultures from each of four color groups reveals that (1) there is good correlation between the fluorescence of chlorophyll 'a' remotely simulated and detected by the lidar system and in-situ measurements using four similar excitation wavelengths in a flow-through fluorometer; (2) good correlation exists between the total chlorophyll 'a' calculated from lidar-fluorosensor data and measurements obtained by the Strickland-Parsons method; and (3) the lidar fluorosensor can provide an index of population diversity.

  2. Bioassay studies to determine OTEC's effect on phytoplankton activity

    SciTech Connect

    Carmiggelt, C.J.W.; Hartwig, E.O.; Commins, M.L.; Horne, A.J.

    1982-09-01

    The effect of artificially upwelled water (800m) on phytoplankton from 25m and 100m was simulated using five day bioassays. The results show that some enhancement of the phytoplankton populations in the receiving waters due to upwelling is likely to occur. The very small phytoplankton (< 5 um) are most important in this response. The magnitude of the biostimulation cannot be predicted from this study. Ammonia leaks, spills, and venting are probable in an operating OTEC plant. The bioassays show that additions of ammonia will produce biostimulaton only when the P/N ratio indicates nitrogen limitation. In the Hawaiian waters sampled N-limitation was not always present and varied with depth. No nitrogen fixation was detected. The magnitude of stimulation due to ammonia alone was generally less than the addition of upwelled water which is a more complete nutrient mixture.

  3. Phytoplankton pigment patterns and wind forcing off central California

    NASA Technical Reports Server (NTRS)

    Abbott, Mark R.; Barksdale, Brett

    1991-01-01

    Mesoscale variability in phytoplankton pigment distributions of central California during the spring-summer upwelling season are studied via a 4-yr time series of high-resolution coastal zone color scanner imagery. Empirical orthogonal functions are used to decompose the time series of spatial images into its dominant modes of variability. The coupling between wind forcing of the upper ocean and phytoplankton distribution on mesoscales is investigated. Wind forcing, in particular the curl of the wind stress, was found to play an important role in the distribution of phytoplankton pigment in the California Current. The spring transition varies in timing and intensity from year to year but appears to be a recurrent feature associated with the rapid onset of the upwelling-favorable winds. Although the underlying dynamics may be dominated by processes other than forcing by wind stress curl, it appears that curl may force the variability of the filaments and hence the pigment patterns.

  4. Global patterns of phytoplankton dynamics in coastal ecosystems

    USGS Publications Warehouse

    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.".

  5. Distributional shifts in size structure of phytoplankton community

    NASA Astrophysics Data System (ADS)

    Waga, H.; Hirawake, T.; Fujiwara, A.; Nishino, S.; Kikuchi, T.; Suzuki, K.; Takao, S.

    2015-12-01

    Increased understanding on how marine species shift their distribution is required for effective conservation of fishery resources under climate change. Previous studies have often predicted distributional shifts of fish using satellite derived sea surface temperature (SST). However, SST may not fully represent the changes in species distribution through food web structure and as such this remains an open issue due to lack of ecological perspective on energy transfer process in the earlier studies. One of the most important factors in ecosystem is composition of phytoplankton community, and its size structure determines energy flow efficiency from base to higher trophic levels. To elucidate spatiotemporal variation in phytoplankton size structure, chlorophyll-a size distribution (CSD) algorithm was developed using spectral variance of phytoplankton absorption coefficient through principal component analysis. Slope of CSD (CSD slope) indicates size structure of phytoplankton community where, strong and weak magnitudes of CSD slope indicate smaller and larger phytoplankton structure, respectively. Shifts in CSD slope and SST were derived as the ratio of temporal trend over the 12-year period (2003-2014) to 2-dimensional spatial gradient and the resulting global median velocity of CSD slope and SST were 0.361 and 0.733 km year-1, respectively. In addition, the velocity of CSD slope monotonically increases with increasing latitude, while relatively complex latitudinal pattern for SST emerged. Moreover, angle of shifts suggest that species are required to shift their distribution toward not limited to simple pole-ward migration, and some regions exhibit opposite direction between the velocity of CSD slope and SST. These findings further imply that combined phytoplankton size structure and SST may contribute for more accurate prediction of species distribution shifts relative to existing studies which only considering variations in thermal niches.

  6. Ammonium Uptake by Phytoplankton Regulates Nitrification in the Sunlit Ocean

    PubMed Central

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

    2014-01-01

    Nitrification, the microbial oxidation of ammonium to nitrate, is a central part of the nitrogen cycle. In the ocean’s surface layer, the process alters the distribution of inorganic nitrogen species available to phytoplankton and produces nitrous oxide. A widely held idea among oceanographers is that nitrification is inhibited by light in the ocean. However, recent evidence that the primary organisms involved in nitrification, the ammonia-oxidizing archaea (AOA), are present and active throughout the surface ocean has challenged this idea. Here we show, through field experiments coupling molecular genetic and biogeochemical approaches, that competition for ammonium with phytoplankton is the strongest regulator of nitrification in the photic zone. During multiday experiments at high irradiance a single ecotype of AOA remained active in the presence of rapidly growing phytoplankton. Over the course of this three day experiment, variability in the intensity of competition with phytoplankton caused nitrification rates to decline from those typical of the lower photic zone (60 nmol L−1 d−1) to those in well-lit layers (<1 nmol L−1 d−1). During another set of experiments, nitrification rates exhibited a diel periodicity throughout much of the photic zone, with the highest rates occurring at night when competition with phytoplankton is lowest. Together, the results of our experiments indicate that nitrification rates in the photic zone are more strongly regulated by competition with phytoplankton for ammonium than they are by light itself. This finding advances our ability to model the impact of nitrification on estimates of new primary production, and emphasizes the need to more strongly consider the effects of organismal interactions on nutrient standing stocks and biogeochemical cycling in the surface of the ocean. PMID:25251022

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

    PubMed

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

    2014-01-01

    Nitrification, the microbial oxidation of ammonium to nitrate, is a central part of the nitrogen cycle. In the ocean's surface layer, the process alters the distribution of inorganic nitrogen species available to phytoplankton and produces nitrous oxide. A widely held idea among oceanographers is that nitrification is inhibited by light in the ocean. However, recent evidence that the primary organisms involved in nitrification, the ammonia-oxidizing archaea (AOA), are present and active throughout the surface ocean has challenged this idea. Here we show, through field experiments coupling molecular genetic and biogeochemical approaches, that competition for ammonium with phytoplankton is the strongest regulator of nitrification in the photic zone. During multiday experiments at high irradiance a single ecotype of AOA remained active in the presence of rapidly growing phytoplankton. Over the course of this three day experiment, variability in the intensity of competition with phytoplankton caused nitrification rates to decline from those typical of the lower photic zone (60 nmol L-1 d-1) to those in well-lit layers (<1 nmol L-1 d-1). During another set of experiments, nitrification rates exhibited a diel periodicity throughout much of the photic zone, with the highest rates occurring at night when competition with phytoplankton is lowest. Together, the results of our experiments indicate that nitrification rates in the photic zone are more strongly regulated by competition with phytoplankton for ammonium than they are by light itself. This finding advances our ability to model the impact of nitrification on estimates of new primary production, and emphasizes the need to more strongly consider the effects of organismal interactions on nutrient standing stocks and biogeochemical cycling in the surface of the ocean. PMID:25251022

  8. Macromolecular compositions of phytoplankton in the Amundsen Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Kim, Bo Kyung; Lee, Jang Han; Joo, HuiTae; Song, Ho Jung; Yang, Eun Jin; Lee, Sang Hoon; Lee, Sang H.

    2016-01-01

    The biochemical compositions (proteins, carbohydrates, and lipids) of phytoplankton provide useful information for their environmental growth conditions and nutritional status as a basic food source for upper trophic consumers. Concentrations of these compositions were assessed at 100, 30, and 1% light penetration depths within the euphotic zone in the Amundsen Sea, Antarctica, using colorimetric techniques. The major inorganic nutrients were generally abundant throughout the study area. The average chlorophyll a (chl-a) concentration was 49.2 mg m-2 (S.D.=±27.6 mg m-2) and large phytoplankton (>20 μm) accounted for 64.1% of the total chl-a concentration. The biochemical compositions of the phytoplankton were not significantly different among different light depths or productivity stations. The overall compositions of proteins, carbohydrates, and lipids from all stations averaged 65.9% (S.D.=±12.5%), 22.4% (S.D.=±10.9%), and 11.7% (S.D.=±6.5%), respectively. Regardless of dominant phytoplankton species, nitrogen-abundant conditions sustained high protein compositions of phytoplankton in the Amundsen Sea during the cruise period. Based on the macromolecular compositions, the average food material (FM) concentration was 219.4 μg L-1 (S.D.=±151.1 μg L-1) and correlated positively with the primary productivity in the Amundsen Sea. High protein/carbohydrate ratios (>1) and large proportions of proteins suggest that phytoplankton provide nitrogen-sufficient foods to higher trophic consumers through a higher efficiency of protein carbon incorporated into herbivores.

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

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

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

  10. Shelters of leaf-tying herbivores decompose faster than leaves damaged by free-living insects: Implications for nutrient turnover in polluted habitats.

    PubMed

    Kozlov, Mikhail V; Zverev, Vitali; Zvereva, Elena L

    2016-10-15

    Leaf-eating insects can influence decomposition processes by modifying quality of leaf litter, and this impact can be especially pronounced in habitats where leaf-eating insects reach high densities, for example in heavily polluted areas. We hypothesized that the decomposition rate is faster for shelters of leaf-tying larvae than for leaves damaged by free-living insects, in particular due to the accumulation of larval frass within shelters. We exposed litter bags containing samples of three different compositions (shelters built by moth larvae, leaves damaged by free-living insects and intact leaves of mountain birch, Betula pubescens ssp. czerepanovii) for one year at two heavily polluted sites near the nickel-copper smelter at Monchegorsk in north-western Russia and at two unpolluted sites. The decomposition rate of leaves damaged by free-living insects was 91% of that of undamaged leaves, whereas the mass loss of leaves composing shelters did not differ of that of undamaged leaves. These differences between leaves damaged by different guilds of herbivorous insects were uniform across the study sites, although the decomposition rate in polluted sites was reduced to 77% of that in unpolluted sites. Addition of larval frass to undamaged leaves had no effect on the subsequent decomposition rate. Therefore we suggest that damaged leaves tied by shelter-building larvae decompose faster than untied damaged leaves due to a looser physical structure of the litter, which creates favourable conditions for detritivores and soil decomposers. Thus, while leaf damage by insects per se reduces litter quality and its decomposition rate, structuring of litter by leaf-tying insects counterbalances these negative effects. We conclude that leaf-tying larvae, in contrast to free-living defoliators, do not impose negative effects on nutrient turnover rate even at their high densities, which are frequently observed in heavily polluted sites. PMID:27288287

  11. Temporal patterns of phytoplankton abundance in the North Atlantic

    NASA Technical Reports Server (NTRS)

    Campbell, Janet W.

    1989-01-01

    A time series of CZCS images is being developed to study phytoplankton distribution patterns in the North Atlantic. The goal of this study is to observe temporal variability in phytoplankton pigments and other organic particulates, and to infer from these patterns the potential flux of biogenic materials from the euphotic layer to the deep ocean. Early results of this project are presented in this paper. Specifically, the satellite data used were 13 monthly composited images of CZCS data for the North Atlantic from January 1979 to January 1980. Results are presented for seasonal patterns along the 20 deg W meridian.

  12. Physiological Ecology of Dimethylsulfoniopropionate (DMSP) and Dimethylsulfide (DMS) Production by Phytoplankton

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The main objectives of the previously funded work were: (1) to determine the rates of DMSP and DMS production as a function of phytoplankton growth rate; (2) to determine the light dependence (quantity and quality) of DiMethylSulfonioPropionate (DMSP) and DiMethylSulfide (DMS) production by phytoplankton; and (3) to study intraspecific differences in DMSP and DMS production by phytoplankton.

  13. ESTIMATION OF PHYTOPLANKTON DECOMPOSITION RATES USING TWO-STAGE CONTINUOUS FLOW STUDIES

    EPA Science Inventory

    A two-stage continuous flow (TSCF) system was used to quantify phytoplankton decomposition rates and to characterize the decay process as a function of phytoplankton species, phytoplankton physiological state, and the presence and character of a decomposer community. A TSCF syste...

  14. Multiwavelength LIDAR for remote sensing of chlorophyll A in algae and phytoplankton

    NASA Technical Reports Server (NTRS)

    Mumola, P. B.; Jarrett, O., Jr.; Brown, C. A., Jr.

    1975-01-01

    A theoretical and experimental analysis of laser induced fluorescence for remote detection of chlorophyll A in living algae and phytoplankton is presented. The fluorescent properties of various species of algae representative of the different color groups are described. Laboratory measurements of fluorescent scattering cross sections is discussed and quantitive data presented. A scattering matrix model is developed to demonstrate the essential requirement of multiwavelength laser excitation in order to make accurate quantitative measurements of chlorophyll A concentration when more than one color group of algae is present in the water. A practical airborne laser fluorosensor design is considered and analysis of field data discussed. Successful operation of the Langley ALOPE (airborne LIDAR oceanographic probing experiment) system is described and field measurements presented. Accurate knowledge of alpha, the optical attenuation coefficient of the water, is shown to be essential for quantitative analysis of chlorophyll A concentration. The feasibility of remotely measuring alpha by laser radar is discussed.

  15. Remote-sensing-based measurement of phytoplankton size spectrum and cell diameter in the global oceans

    NASA Astrophysics Data System (ADS)

    Roy, S.; Sathyendranath, S.; Bouman, H. A.; Platt, T.

    2012-12-01

    Oceanic phytoplankton regulate the spectral quality of the submarine light field because light absorption by phytoplankton is spectrally structured, with a maximum in the blue and a secondary maximum in the red. The spectral characteristics of absorption are variable with phytoplankton taxa, and also with cell size and growth conditions. The intra-cellular concentration of light-absorbing pigments varies with phytoplankton size, which in turn modulates its specific absorption. The changes in phytoplankton cell size alter not only the bio-optical properties of the water column, but also the trophic interactions within the ecosystem. It is thus important to study the time evolution of phytoplankton size structure over the global ocean. We have developed a novel model that uses the light absorption coefficient of phytoplankton to retrieve quantitative information about phytoplankton size structure from satellite-derived ocean-colour data. The application of the method to satellite remote sensing at any given spatial location depends on the estimates of the concentration of chlorophyll-a, which is an operational index of phytoplankton biomass, and the remote sensing reflectance at different wavelengths in the visible domain. Using our method we have computed the equivalent spherical diameter of phytoplankton cells and the exponent of particle-size spectrum of phytoplankton, and thereby estimated the chlorophyll distribution in different phytoplankton size classes on a global scale. The spatial distribution of the size-spectrum exponent and the biomass fractions of pico-, nano- and micro-phytoplankton estimated are consistent with our current understanding of phytoplankton functional types in the global oceans. The study will enhance our understanding of the distribution and time evolution of phytoplankton size structure in the global oceans.

  16. 182Hf–182W age dating of a 26Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System

    PubMed Central

    Holst, Jesper C.; Olsen, Mia B.; Paton, Chad; Nagashima, Kazuhide; Schiller, Martin; Wielandt, Daniel; Larsen, Kirsten K.; Connelly, James N.; Jørgensen, Jes K.; Krot, Alexander N.; Nordlund, Åke; Bizzarro, Martin

    2013-01-01

    Refractory inclusions [calcium–aluminum-rich inclusions, (CAIs)] represent the oldest Solar System solids and provide information regarding the formation of the Sun and its protoplanetary disk. CAIs contain evidence of now extinct short-lived radioisotopes (e.g., 26Al, 41Ca, and 182Hf) synthesized in one or multiple stars and added to the protosolar molecular cloud before or during its collapse. Understanding how and when short-lived radioisotopes were added to the Solar System is necessary to assess their validity as chronometers and constrain the birthplace of the Sun. Whereas most CAIs formed with the canonical abundance of 26Al corresponding to 26Al/27Al of ∼5 × 10−5, rare CAIs with fractionation and unidentified nuclear isotope effects (FUN CAIs) record nucleosynthetic isotopic heterogeneity and 26Al/27Al of <5 × 10−6, possibly reflecting their formation before canonical CAIs. Thus, FUN CAIs may provide a unique window into the earliest Solar System, including the origin of short-lived radioisotopes. However, their chronology is unknown. Using the 182Hf–182W chronometer, we show that a FUN CAI recording a condensation origin from a solar gas formed coevally with canonical CAIs, but with 26Al/27Al of ∼3 × 10−6. The decoupling between 182Hf and 26Al requires distinct stellar origins: steady-state galactic stellar nucleosynthesis for 182Hf and late-stage contamination of the protosolar molecular cloud by a massive star(s) for 26Al. Admixing of stellar-derived 26Al to the protoplanetary disk occurred during the epoch of CAI formation and, therefore, the 26Al–26Mg systematics of CAIs cannot be used to define their formation interval. In contrast, our results support 182Hf homogeneity and chronological significance of the 182Hf–182W clock. PMID:23671077

  17. 182Hf-182W age dating of a 26Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System.

    PubMed

    Holst, Jesper C; Olsen, Mia B; Paton, Chad; Nagashima, Kazuhide; Schiller, Martin; Wielandt, Daniel; Larsen, Kirsten K; Connelly, James N; Jørgensen, Jes K; Krot, Alexander N; Nordlund, Ake; Bizzarro, Martin

    2013-05-28

    Refractory inclusions [calcium-aluminum-rich inclusions, (CAIs)] represent the oldest Solar System solids and provide information regarding the formation of the Sun and its protoplanetary disk. CAIs contain evidence of now extinct short-lived radioisotopes (e.g., (26)Al, (41)Ca, and (182)Hf) synthesized in one or multiple stars and added to the protosolar molecular cloud before or during its collapse. Understanding how and when short-lived radioisotopes were added to the Solar System is necessary to assess their validity as chronometers and constrain the birthplace of the Sun. Whereas most CAIs formed with the canonical abundance of (26)Al corresponding to (26)Al/(27)Al of ∼5 × 10(-5), rare CAIs with fractionation and unidentified nuclear isotope effects (FUN CAIs) record nucleosynthetic isotopic heterogeneity and (26)Al/(27)Al of <5 × 10(-6), possibly reflecting their formation before canonical CAIs. Thus, FUN CAIs may provide a unique window into the earliest Solar System, including the origin of short-lived radioisotopes. However, their chronology is unknown. Using the (182)Hf-(182)W chronometer, we show that a FUN CAI recording a condensation origin from a solar gas formed coevally with canonical CAIs, but with (26)Al/(27)Al of ∼3 × 10(-6). The decoupling between (182)Hf and (26)Al requires distinct stellar origins: steady-state galactic stellar nucleosynthesis for (182)Hf and late-stage contamination of the protosolar molecular cloud by a massive star(s) for (26)Al. Admixing of stellar-derived (26)Al to the protoplanetary disk occurred during the epoch of CAI formation and, therefore, the (26)Al-(26)Mg systematics of CAIs cannot be used to define their formation interval. In contrast, our results support (182)Hf homogeneity and chronological significance of the (182)Hf-(182)W clock. PMID:23671077

  18. Sexual risk behaviour among migrant tribals living in urban slums of an eastern Indian city: implications on the spread of HIV.

    PubMed

    Mishra, Suchismita; Swain, Basanta Kumar; Babu, Bontha Veerraju

    2008-03-01

    This paper reports the sexual risk behaviour among migrant tribal community living in an eastern Indian city. The age at marriage is very low in this community and 54% of women had first intercourse before the age of 15 years with the mean of 15.8 years and it is 19.5 years for men. Pre and extramarital relations, including multi-partnered sex is prevalent. Safe sexual practices are not reported and the risk perception is very low. High prevalence of behavioral risk factors leaves a potential risk for rapid spread of human immunodeficiency virus (HIV) both in slums as well as in remote tribal areas. PMID:18494181

  19. Climatic influences on development and survival of free-living stages of equine strongyles: implications for worm control strategies and managing anthelmintic resistance.

    PubMed

    Nielsen, Martin K; Kaplan, Ray M; Thamsborg, Stig M; Monrad, Jesper; Olsen, Susanne N

    2007-07-01

    Development of resistance to anthelmintic drugs by horse strongyles constitutes a growing threat to equine health because it is unknown when new drug classes can be expected on the market. Consequently, parasite control strategies should attempt to maintain drug efficacy for as long as possible. The proportion of a parasite population that is not exposed to anthelmintic treatment is described as being "in refugia" and although many factors affect the rate at which resistance develops, levels of refugia are considered the most important as these parasites are not selected by treatment and so provide a pool of sensitive genes in the population. Accordingly, treatment should be avoided when pasture refugia are small because such treatments will place significant selection pressure for resistance on worm populations. Given this new paradigm for parasite control, it has become important to identify seasons and circumstances wherein refugia are diminished. Free-living stages of equine strongyles are highly dependent on climatic influences, and this review summarises studies of strongyle development and survival under laboratory and field conditions in Northern (cool) temperate, Southern (warm) temperate and subtropical/tropical climates. In Northern temperate climates, refugia are smallest during the winter. In contrast, refugia are lowest during the summer in warm temperate and subtropical/tropical climates. Although adverse seasonal changes clearly have significant effects on the ability of free living stages of strongyle nematode parasites to survive and develop, available data suggest that climatic influences cannot effectively "clean" pastures from one grazing season to the next. PMID:16815051

  20. A systematic review of factors influencing fertility desires and intentions among people living with HIV/AIDS: implications for policy and service delivery.

    PubMed

    Nattabi, Barbara; Li, Jianghong; Thompson, Sandra C; Orach, Christopher Garimoi; Earnest, Jaya

    2009-10-01

    With availability of antiretroviral treatments, HIV is increasingly recognised as a chronic disease people live with for many years. This paper critically reviews the current literature on fertility desires and reproductive intentions among people living with HIV/AIDS (PLHIV) and critiques the theoretical frameworks and methodologies used. A systematic review was conducted using electronic databases: ISI Web of Knowledge, Science Direct, Proquest, Jstor and CINAHL for articles published between 1990 and 2008. The search terms used were fertility desire, pregnancy, HIV, reproductive decision making, reproductive intentions, motherhood, fatherhood and parenthood. Twenty-nine studies were reviewed. Fertility desires were influenced by a myriad of demographic, health, stigma-associated and psychosocial factors. Cultural factors were also important, particularly in Sub-Saharan Africa and Asia. Future research that examines fertility desires among PLHIV should include cultural beliefs and practices in the theoretical framework in order to provide a holistic understanding and to enable development of services that meet the reproductive needs of PLHIV. PMID:19330443

  1. Physical supply of nitrogen to phytoplankton in the Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Mahaffey, Claire; Williams, Richard G.; Wolff, George A.; Anderson, William T.

    2004-03-01

    Mechanisms supplying nitrogen (N) to phytoplankton, and thus constraining the levels of export production, over the oligotrophic subtropical Atlantic are assessed along a meridional transect. Stable nitrogen isotope signals reveal a localized region of N2 fixation over the northern subtropical gyre. Elsewhere, particulate organic nitrogen was isotopically enriched and there was no widespread evidence of a trophic bias. Thus phytoplankton are utilizing an enriched source of N along the transect through much of the oligotrophic Atlantic, which may reflect utilization of nitrate from the deep ocean or, possibly, a supply of dissolved organic nitrogen (DON) from a non-N2 fixing source. While there is a significant supply of DON over the subtropical gyres, reaching 0.15 mol Nm-2 yr-1, less than 10% of the DON is semilabile and thus only implies a relatively small contribution to the nitrogen supply required for export production. Over the central part of the subtropical gyres, the supply of N to phytoplankton is probably from nitrate in the underlying thermocline, possibly from convection and diapycnic transfer, or more likely, from finescale upwelling by mesoscale eddies and frontal circulations. The lateral supply of dissolved organic phosphorus (DOP) appears to be a factor of 2-3 times more important than the lateral supply of semilabile DON, and thus might play a role in contributing to the phosphorus (P) supply for phytoplankton. The lateral supply of DON and DOP might also be important in closing the N and P budgets over the North Atlantic.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    We developed an approach to assess environmental flows in estuaries related to preference of phytoplankton considering the complex relationship between hydrological modification and biomass in ecosystems. As a first step, a relationship was established between biomass requirements for organisms of primary and higher nutritional levels based on the principle of nutritional energy flow of ecosystem. Then, diagnostic pigments were employed to represent phytoplankton community biomass, which indicated competition between two groups of phytoplankton in the biochemistry process. Considering empirical relationships between diagnostic pigments and critical environmental factors, responses of biomass to river discharges were established based on a convection-diffusion model by simulating distributions of critical environmental factors under action of river discharges and tide currents. Consequently, environmental flows could be recommended for different requirements of fish biomass. In the case study in the Yellow River estuary, May and October were identified as critical months for fish reproduction and growth during dry years. Artificial hydrological regulation strategies should carefully consider the temporal variations of natural flow regime, especially for a high-amplitude flood pulse, which may cause negative effects on phytoplankton groups and higher organism biomass.

  4. The evolutionary inheritance of elemental stoichiometry in marine phytoplankton

    NASA Astrophysics Data System (ADS)

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

    2003-09-01

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

  5. Light utilization and photoinhibition of photosynthesis in marine phytoplankton

    SciTech Connect

    Falkowski, P.G., Greene, R., Kolber, Z.

    1993-12-31

    Introduction to Phytoplankton. Based on the record of the oldest identifiable fossils, the first oxygenic photosynthetic organisms appeared about 2 {times} l0{sup 9} years ago in the form of marine single celled, planktonic procaryotes (Riding, 1992; Sarmiento and Bender, 1993). In the intervening eons, phytoplankton have evolved and diversified; presently they represent at least 11 classes of procaryotic and euacaryotic photoautotrophs. While the carbon of these organisms cumulatively amounts to only 1 to 2% of the global plant biomass, they fix between 35 and 50 gigatonnes ({times} 10{sup 9} metric tons) of carbon annually, about 40% of the global total (Falkowski and Woodhead, 1992). On average, each gram of phytoplankton chlorophyll converts about 6% of the photosynthetically active radiation (440 to 700 nm) incident on the sea surface to photochemical energy (Morel, 1978). Despite a great deal of variability in ocean environments, this photosynthetic conversion efficiency is relatively constant for integrated water column production (Morel, 1978; Falkowski, 1981; Platt, 1986; Morel, 1991). Here we review the factors determining light utilization efficiency of phytoplankton in the oceans, and the physiological acclimations which have evolved to optimize light utilization efficiency.

  6. Phytoplankton community composition in nearshore coastal waters of Louisiana

    EPA Science Inventory

    Phytoplankton community compositions within near-shore coastal and estuarine waters of Louisiana were characterized by relative abundance, biovolume, and taxonomic identification to genus and species when possible. The range of total nitrogen was 0.5 to 1.3 mg L-1 and total phos...

  7. PHYSIOLOGICAL LIMITATIONS ON PHYTOPLANKTON PRODUCTIVITY IN THE OCEAN

    EPA Science Inventory

    The question of what limits Primary Productivity and phytoplankton biomass in natural waters has occupied oceanographers and limnologists for more than a century. he earliest oceanographers recognized that this issue is key to understanding the regulation of both aquatic food cha...

  8. RESPONSE OF PHYTOPLANKTON TO ACIDIFICATION IN EXPERIMENTAL STREAMS

    EPA Science Inventory

    In order to examine the response of stream phytoplankton communities to acidification, three artificial streams along the Mississippi River were sampled at biweekly intervals. This study took place at Monticello, Minnesota, during late spring-early summer, 1979. One stream served...

  9. High protein production of phytoplankton in the Amundsen Sea

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

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

    PubMed Central

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

    2008-01-01

    Biotic interactions in the plankton can be both complex and dynamic. Competition among phytoplankton is often chemically mediated, but no studies have considered whether allelopathic compounds are modified by biotic interactions. Here, we show that compounds exuded during Karenia brevis blooms were allelopathic to the cosmopolitan diatom Skeletonema costatum, but that bloom allelopathy varied dramatically among collections and years. We investigated several possible causes of this variability and found that neither bloom density nor concentrations of water-borne brevetoxins correlated with allelopathic potency. However, when we directly tested whether the presence of competing phytoplankton influenced bloom allelopathy, we found that S. costatum reduced the growth-inhibiting effects of bloom exudates, suggesting that S. costatum has a mechanism for undermining K. brevis allelopathy. Additional laboratory experiments indicated that inducible changes to K. brevis allelopathy were restricted to two diatoms among five sensitive phytoplankton species, whereas five other species were constitutively resistant to K. brevis allelopathy. Our results suggest that competitors differ in their responses to phytoplankton allelopathy, with S. costatum exhibiting a previously undescribed method of resistance that may influence community structure and alter bloom dynamics. PMID:18713720

  11. A turbulence-induced switch in phytoplankton swimming behavior

    NASA Astrophysics Data System (ADS)

    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. The Molecular Ecophysiology of Programmed Cell Death in Marine Phytoplankton

    NASA Astrophysics Data System (ADS)

    Bidle, Kay D.

    2015-01-01

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

  13. High-Resolution Fluorometer for Mapping Microscale Phytoplankton Distributions

    PubMed Central

    Doubell, Mark J.; Seuront, Laurent; Seymour, Justin R.; Patten, Nicole L.; Mitchell, James G.

    2006-01-01

    A new high-resolution, in situ profiling fluorometer maps fluorescence distributions with a spatial resolution of 0.5 to 1.5 mm to a depth of 70 m in the open ocean. We report centimeter-scale patterns for phytoplankton distributions associated with gradients exhibiting 10- to 30-fold changes in fluorescence in contrasting marine ecosystems. PMID:16751572

  14. High-resolution fluorometer for mapping microscale phytoplankton distributions.

    PubMed

    Doubell, Mark J; Seuront, Laurent; Seymour, Justin R; Patten, Nicole L; Mitchell, James G

    2006-06-01

    A new high-resolution, in situ profiling fluorometer maps fluorescence distributions with a spatial resolution of 0.5 to 1.5 mm to a depth of 70 m in the open ocean. We report centimeter-scale patterns for phytoplankton distributions associated with gradients exhibiting 10- to 30-fold changes in fluorescence in contrasting marine ecosystems. PMID:16751572

  15. IRON LIMITATION OF PHYTOPLANKTON PHOTOSYNTHESIS IN THE EQUATORIAL PACIFIC OCEAN

    EPA Science Inventory

    The surface waters of the equatorial Pacific have unusually high nitrate and phosphate concentrations, but relatively low phytoplankton biomass. his high nitrate, low chlorophyll' (HNLC) phenomenon has been ascribed to 'top-down' grazing pressure by herbivores which prevent the p...

  16. Responses of primary productivity to increased temperature and phytoplankton diversity

    NASA Astrophysics Data System (ADS)

    Lewandowska, Aleksandra M.; Breithaupt, Petra; Hillebrand, Helmut; Hoppe, Hans-Georg; Jürgens, Klaus; Sommer, Ulrich

    2012-08-01

    In order to examine the effects of warming and diversity changes on primary productivity, we conducted a meta-analysis on six independent indoor mesocosm experiments with a natural plankton community from the Baltic Sea. Temperature effects on primary productivity changed with light intensity and zooplankton density and analysed pathways between temperature, diversity and productivity, elucidating direct and indirect effects of warming on primary productivity during the spring phytoplankton bloom. Our findings indicate that warming directly increased carbon specific primary productivity, which was more pronounced under low grazing pressure. On the other hand, primary productivity per unit water volume did not respond to increased temperature, because of a negative temperature effect on phytoplankton biomass. Moreover, primary productivity response to temperature changes depended on light limitation. Using path analysis, we tested whether temperature effects were direct or mediated by warming effects on phytoplankton diversity. Although phytoplankton species richness had a positive impact on both net primary productivity and carbon specific primary productivity - and evenness had a negative effect on net primary productivity - both richness and evenness were not affected by temperature. Thus, we suggest that diversity effects on primary productivity depended mainly on other factors than temperature like grazing, sinking or nutrient limitation, which themselves are temperature dependent.

  17. DNA Analyses of Phytoplankton in the Southern Ocean

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  18. Hydrologic controls of phytoplankton blooms in the Gulf of Maine

    NASA Astrophysics Data System (ADS)

    Roesler, C. S.; Barnard, A. H.; Pettigrew, N. R.

    2014-12-01

    The Gulf of Maine is a marginal sea adjacent to the subpolar North Atlantic gyre. It similarly exhibits canonical seasonal phytoplankton blooms. An array of moorings was deployed on the shelf and deep basins in the Gulf of Maine in 2001 with real-time hydrographic and optical sensor packages. Daily climatologies of calibrated chlorophyll fluorescence (a proxy for phytoplankton biomass), temperature and salinity provide quantitative models for the spatial progression of seasonal patterns in stratification and bloom development. Anomaly time series indicate an abrupt change in the seasonal patterns beginning in 2005. Prior to 2005, seasonal blooms were triggered by the onset of thermally-driven stratification, the timing of which was primarily determined by latitude without influence of location on the shelf or deep basins. Spring blooms propagated from southwest to northeast, while fall blooms propagated from northeast to southwest following autumnal cooling and destratification. Beginning in 2005, an increase in the amount and intensity of precipitation yielded significant changes in river discharge patterns, particularly associated with the spring freshet. Springtime stratification patterns , and hence spring phytoplankton blooms, appeared much earlier and synoptically across the Gulf, in some locations up to 2 months earlier than observed prior to 2005. The consequences of such large variations in the timing and spatial patterns of spring phytoplankton blooms include large variations in specific growth rates, mismatch with grazing populations, and cascading changes in ecosystem structure throughout the Gulf of Maine.

  19. Lake Superior Phytoplankton Characterization from the 2006 Probability Based Survey

    EPA Science Inventory

    We conducted a late summer probability based survey of Lake Superior in 2006 which consisted of 52 sites stratified across 3 depth zones. As part of this effort, we collected composite phytoplankton samples from the epilimnion and the fluorescence maxima (Fmax) at 29 of the site...

  20. Assisted Living

    MedlinePlus

    ... it, too. Back to top What is the Cost for Assisted Living? Although assisted living costs less than nursing home care, it is still ... of services an older person chooses, the price costs can range from less than $25,000 a ...

  1. Effects of UV radiation on phytoplankton

    NASA Astrophysics Data System (ADS)

    Smith, Raymond C.; Cullen, John J.

    1995-07-01

    et al., 1986; Worrest, 1986; NOAA, 1987; Smith, 1989; Smith and Baker, 1989; Voytek, 1990; Häder, 1993; Acevedo and Nolan, 1993; Holm-Hansen et al., 1993; Vincent and Roy, 1993; Biggs and Joyner, 1994; Williamson and Zagarese, 1994; Karentz, 1994; Cullen and Neale, 1993; Cullen and Neale, 1994]. As Hader et al. have summarized [UNEP, 1989; UNEP, 1991], "UV-B radiation in aquatic systems: 1) affects adaptive strategies (e.g., motility, orientation); 2) impairs important physiological functions (e.g., photosynthesis and enzymatic reactions); and 3) threatens marine organisms during their developmental stages (e.g., the young of finfish, shrimp larvae, crab larvae)". Possible consequences to aquatic systems include: reduced biomass production; changes in species composition and biodiversity; and alterations of aquatic ecosystems and biogeochemical cycles associated with the above changes. Within the past four years, our knowledge with respect to the environmental effects of ozone-related increased levels of UV-B has increased significantly, and numerous efforts have been directed toward process-oriented studies of UV responses in plants and animals. Consensus is building toward the view that current levels of UV play a major role as an ecological determinant, influencing both survival and distribution, and are thus deserving of increased study independent of ozone-related UV-B increases. This review outlines U.S. research subsequent to 1991 and emphasizes studies concerned with phytoplankton.

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

    PubMed

    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. PMID:26301719

  3. Phytoplankton community structure defined by key environmental variables in Tagus estuary, Portugal.

    PubMed

    Brogueira, Maria José; Oliveira, Maria do Rosário; Cabeçadas, Graça

    2007-12-01

    In this work, we analyze environmental (physical and chemical) and biological (phytoplankton) data obtained along Tagus estuary during three surveys, carried out in productive period (May/June/July) at ebb tide. The main objective of this study was to identify the key environmental factors affecting phytoplankton structure in the estuary. BIOENV analysis revealed that, in study period, temperature, salinity, silicate and total phosphorus were the variables that best explained the phytoplankton spatial pattern in the estuary (Spearman correlation, rho=0.803). A generalized linear model (GLM) also identified salinity, silicate and phosphate as having a high explanatory power (63%) of phytoplankton abundance. These selected nutrients appear to be consistent with the requirements of the dominant phytoplankton group, Baccilariophyceae. Apparently, phytoplankton community is adapted to fluctuations in light intensity, as suspended particulate matter did not come out as a key factor in shaping phytoplankton structure along Tagus estuary. PMID:17884159

  4. Differential Growth Responses of Marine Phytoplankton to Herbicide Glyphosate.

    PubMed

    Wang, Cong; Lin, Xin; Li, Ling; Lin, Senjie

    2016-01-01

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

  5. Differential Growth Responses of Marine Phytoplankton to Herbicide Glyphosate

    PubMed Central

    Wang, Cong; Lin, Xin; Li, Ling; Lin, Senjie

    2016-01-01

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

  6. Controls on phytoplankton cell size distributions in contrasting physical environments

    NASA Astrophysics Data System (ADS)

    Clark, J. R.; Daines, S. J.; Lenton, T. M.

    2012-04-01

    A key challenge for marine ecosystem and biogeochemical models is to capture the multiple ecological and evolutionary processes driving the adaptation of diverse communities to changed environmental conditions over different spatial and temporal scales. These range from short-term acclimation in individuals, to population-level selection, immigration and ecological succession on intermediate scales, to shifts in the global biogeochemical cycling of key elements. As part of the "EVE" project, we have been working toward improving the representation of ecological and evolutionary processes in models, with a focus on understanding the role of marine ecosystems in the past, present, and future Earth system. Our approach is to develop a mechanistic understanding of trade-offs between different functional traits through the explicit representation of resource investment in sub-cellular components controlled by a synthetic genome. Trait expression (including size, metabolic strategies on a continuum from autotrophy to heterotrophy, and predation strategies) and adaptation to the environment are then emergent properties of the model, following from natural selection operating in the model environment. Here we show results relating to controls on phytoplankton cell size - a key phytoplankton trait which is inextricably linked to the structuring and functioning of marine ecosystems. Coupled to the MIT OGCM, we use the model to derive dynamic optimal size-class distributions at representative oligotrophic and high-latitude time series sites, which are then compared with in situ data. Particular attention is given to the relative importance of top-down vs bottom-up drivers for phytoplankton cell size, and their influence on global patterns in phytoplankton cell size, as well as changes in the cell size distribution during phytoplankton bloom periods.

  7. Review on the experience with live attenuated vaccines against tropical theileriosis in Tunisia: considerations for the present and implications for the future.

    PubMed

    Darghouth, Mohamed Aziz

    2008-12-19

    The choice of a vaccine candidate against tropical theileriosis was based on key epidemiological considerations inherent to the main target endemic situation in Tunisia. One of the attenuated cell lines was retained as a vaccine candidate on the basis of small-scale trials testing the intrinsic safety aspects of the vaccine for the targeted animal categories in the dominant endemic situation where it will be used. The vaccine efficacy was confirmed in pilot vaccination campaigns using fresh culture and thawed cryopreserved vaccine doses delivered to the field using a new delivery system not requiring a cold chain. The potential benefit of the live attenuated Tunisian vaccine was evaluated using simple economical models. PMID:19178892

  8. Subclinical Chlamydial Infection of the Female Mouse Genital Tract Generates a Potent Protective Immune Response: Implications for Development of Live Attenuated Chlamydial Vaccine Strains

    PubMed Central

    Su, Hua; Messer, Ronald; Whitmire, William; Hughes, Scott; Caldwell, Harlan D.

    2000-01-01

    Chlamydia trachomatis is a major cause of sexually transmitted disease (STD) for which a vaccine is needed. CD4+ T-helper type 1 (Th1) cell-mediated immunity is an important component of protective immunity against murine chlamydial genital infection. Conventional vaccine approaches have not proven effective in eliciting chlamydial-specific CD4 Th1 immunity at the genital mucosa. Thus, it is possible that the development of a highly efficacious vaccine against genital infection will depend on the generation of a live attenuated C. trachomatis vaccine. Attenuated strains of C. trachomatis do not exist, so their potential utility as vaccines cannot be tested in animal models of infection. We have developed a surrogate model to study the effect of chlamydial attenuation on infection and immunity of the female genital tract by treating mice with a subchlamydiacidal concentration of oxytetracycline following vaginal infection. Compared to untreated control mice, antibiotic-treated mice shed significantly fewer infectious organisms (3 log10) from the cervico-vagina, produced a minimal inflammatory response in urogenital tissue, and did not experience infection-related sequelae. Antibiotic-treated mice generated levels of chlamydia-specific antibody and cell-mediated immunity equivalent to those of control mice. Importantly, antibiotic-treated mice were found to be as immune as control untreated mice when rechallenged vaginally. These findings demonstrate that subclinical chlamydial infection of the murine female genital tract is sufficient to stimulate a potent protective immune response. They also present indirect evidence supporting the possible use of live attenuated chlamydial organisms in the development of vaccines against chlamydial STDs. PMID:10603387

  9. Nuttalliella namaqua: A Living Fossil and Closest Relative to the Ancestral Tick Lineage: Implications for the Evolution of Blood-Feeding in Ticks

    PubMed Central

    Mans, Ben J.; de Klerk, Daniel; Pienaar, Ronel; Latif, Abdalla A.

    2011-01-01

    Ticks are monophyletic and composed of the hard (Ixodidae) and soft (Argasidae) tick families, as well as the Nuttalliellidae, a family with a single species, Nuttalliella namaqua. Significant biological differences in lifestyle strategies for hard and soft ticks suggest that various blood-feeding adaptations occurred after their divergence. The phylogenetic relationships between the tick families have not yet been resolved due to the lack of molecular data for N. namaqua. This tick possesses a pseudo-scutum and apical gnathostoma as observed for ixodids, has a leathery cuticle similar to argasids and has been considered the evolutionary missing link between the two families. Little knowledge exists with regard to its feeding biology or host preferences. Data on its biology and systematic relationship to the other tick families could therefore be crucial in understanding the evolution of blood-feeding behaviour in ticks. Live specimens were collected and blood meal analysis showed the presence of DNA for girdled lizards from the Cordylid family. Feeding of ticks on lizards showed that engorgement occurred rapidly, similar to argasids, but that blood meal concentration occurs via malpighian excretion of water. Phylogenetic analysis of the 18S nuclear and 16S mitochondrial genes indicate that N. namaqua grouped basal to the main tick families. The data supports the monophyly of all tick families and suggests the evolution of argasid-like blood-feeding behaviour in the ancestral tick lineage. Based on the data and considerations from literature we propose an origin for ticks in the Karoo basin of Gondwanaland during the late Permian. The nuttalliellid family almost became extinct during the End Permian event, leaving N. namaqua as the closest living relative to the ancestral tick lineage and the evolutionary missing link between the tick families. PMID:21858204

  10. Live bird markets characterization and trading network analysis in Mali: Implications for the surveillance and control of avian influenza and Newcastle disease.

    PubMed

    Molia, Sophie; Boly, Ismaël Ardho; Duboz, Raphaël; Coulibaly, Boubacar; Guitian, Javier; Grosbois, Vladimir; Fournié, Guillaume; Pfeiffer, Dirk Udo

    2016-03-01

    Live bird markets (LBMs) play an important role in the transmission of avian influenza (AI) and Newcastle disease (ND) viruses in poultry. Our study had two objectives: (1) characterizing LBMs in Mali with a focus on practices influencing the risk of transmission of AI and ND, and (2) identifying which LBMs should be targeted for surveillance and control based on properties of the live poultry trade network. Two surveys were conducted in 2009-2010: a descriptive study in all 96 LBMs of an area encompassing approximately 98% of the Malian poultry population and a network analysis study in Sikasso county, the main poultry supplying county for the capital city Bamako. Regarding LBMs' characteristics, risk factors for the presence of AI and ND viruses (being open every day, more than 2 days before a bird is sold, absence of zoning to segregate poultry-related work flow areas, waste removal or cleaning and disinfecting less frequently than on a daily basis, trash disposal of dead birds and absence of manure processing) were present in 80-100% of the LBMs. Furthermore, LBMs tended to have wide catchment areas because of consumers' preference for village poultry meat, thereby involving a large number of villages in their supply chain. In the poultry trade network from/to Sikasso county, 182 traders were involved and 685 links were recorded among 159 locations. The network had a heterogeneous degree distribution and four hubs were identified based on measures of in-degrees, out-degrees and betweenness: the markets of Medine and Wayerma and the fairs of Farakala and Niena. These results can be used to design biosecurity-improvement interventions and to optimize the prevention, surveillance and control of transmissible poultry diseases in Malian LBMs. Further studies should investigate potential drivers (seasonality, prices) of the poultry trade network and the acceptability of biosecurity and behavior-change recommendations in the Malian socio-cultural context. PMID

  11. Demographic and genetic status of an isolated population of bog turtles (Glyptemys muhlenbergii): Implications for managing small populations of long-lived animals

    USGS Publications Warehouse

    Pittman, Shannon E.; King, T.L.; Faurby, S.; Dorcas, M.E.

    2011-01-01

    In this study, we sought to determine the population stability and genetic diversity of one isolated population of the federally-threatened bog turtle (Glyptemys muhlenbergii) in North Carolina. Using capture-recapture data, we estimated adult survival and population growth rate from 1992 to 2007. We found that the population decreased from an estimated 36 adult turtles in 1994 to approximately 11 adult turtles in 2007. We found a constant adult survival of 0. 893 (SE = 0. 018, 95% confidence interval, 0. 853-0. 924) between 1992 and 2007. Using 18 microsatellite markers, we compared the genetic status of this population with five other bog turtle populations. The target population displayed allelic richness (4. 8 ?? 0. 5) and observed heterozygosity (0. 619 ?? 0. 064) within the range of the other bog turtle populations. Coalescent analysis of population growth rate, effective population size, and timing of population structuring event also indicated the genetics of the target population were comparable to the other populations studied. Estimates of effective population size were a proportion of the census size in all populations except the target population, in which the effective population size was larger than the census size (30 turtles vs. 11 turtles). We attribute the high genetic diversity in the target population to the presence of multiple generations of old turtles. This study illustrates that the demographic status of populations of long-lived species may not be reflected genetically if a decline occurred recently. Consequently, the genetic integrity of populations of long-lived animals experiencing rapid demographic bottlenecks may be preserved through conservation efforts effective in addressing demographic problems. ?? 2011 Springer Science+Business Media B.V.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  13. Live-cell imaging to detect phosphatidylserine externalization in brain endothelial cells exposed to ionizing radiation: implications for the treatment of brain arteriovenous malformations.

    PubMed

    Zhao, Zhenjun; Johnson, Michael S; Chen, Biyi; Grace, Michael; Ukath, Jaysree; Lee, Vivienne S; McRobb, Lucinda S; Sedger, Lisa M; Stoodley, Marcus A

    2016-06-01

    OBJECT Stereotactic radiosurgery (SRS) is an established intervention for brain arteriovenous malformations (AVMs). The processes of AVM vessel occlusion after SRS are poorly understood. To improve SRS efficacy, it is important to understand the cellular response of blood vessels to radiation. The molecular changes on the surface of AVM endothelial cells after irradiation may also be used for vascular targeting. This study investigates radiation-induced externalization of phosphatidylserine (PS) on endothelial cells using live-cell imaging. METHODS An immortalized cell line generated from mouse brain endothelium, bEnd.3 cells, was cultured and irradiated at different radiation doses using a linear accelerator. PS externalization in the cells was subsequently visualized using polarity-sensitive indicator of viability and apoptosis (pSIVA)-IANBD, a polarity-sensitive probe. Live-cell imaging was used to monitor PS externalization in real time. The effects of radiation on the cell cycle of bEnd.3 cells were also examined by flow cytometry. RESULTS Ionizing radiation effects are dose dependent. Reduction in the cell proliferation rate was observed after exposure to 5 Gy radiation, whereas higher radiation doses (15 Gy and 25 Gy) totally inhibited proliferation. In comparison with cells treated with sham radiation, the irradiated cells showed distinct pseudopodial elongation with little or no spreading of the cell body. The percentages of pSIVA-positive cells were significantly higher (p = 0.04) 24 hours after treatment in the cultures that received 25- and 15-Gy doses of radiation. This effect was sustained until the end of the experiment (3 days). Radiation at 5 Gy did not induce significant PS externalization compared with the sham-radiation controls at any time points (p > 0.15). Flow cytometric analysis data indicate that irradiation induced growth arrest of bEnd.3 cells, with cells accumulating in the G2 phase of the cell cycle. CONCLUSIONS Ionizing radiation

  14. Assisted Living

    MedlinePlus

    ... a resident's needs depends as much on the philosophy and services of the assisted living facility as ... the facility provide a written statement of its philosophy of care? Visit each facility more than once, ...

  15. Assisted Living

    MedlinePlus

    ... premises. Adult foster care has the advantages of maintaining frail older adults in a more home-like ... pay to live in these communities, though some facilities have beds for skilled care that are funded ...

  16. Living Laboratories

    ERIC Educational Resources Information Center

    Mules, B. R.

    1976-01-01

    Presented is a review of various methods of keeping live animals, including scorpions, spiders, crabs, crayfish, shrimp, ants, fish, mice, and birds, as well as plants as a school science project/display. (SL)

  17. Healthy Living

    MedlinePlus

    ... Environment Kids Health Kids Environment Kids Health Topics Environment & Health Healthy Living Pollution Reduce, Reuse, Recycle Science – How It Works The Natural World Games Brainteasers Puzzles Riddles Songs Activities Be ...

  18. Assisted Living

    MedlinePlus

    ... are part of retirement communities. Others are near nursing homes, so a person can move easily if needs change. Assisted living costs less than nursing home care. It is still fairly expensive. Older people ...

  19. Assisted Living

    MedlinePlus

    ... Recreational activities Security Transportation How to Choose a Facility A good match between a facility and a resident's needs depends as much on the philosophy and services of the assisted living facility as it does on the quality of care. ...

  20. Live cell imaging of interactions between replicase and capsid protein of Brome mosaic virus using Bimolecular Fluorescence Complementation: Implications for replication and genome packaging

    SciTech Connect

    Chaturvedi, Sonali; Rao, A.L.N.

    2014-09-15

    In Brome mosaic virus, it was hypothesized that a physical interaction between viral replicase and capsid protein (CP) is obligatory to confer genome packaging specificity. Here we tested this hypothesis by employing Bimolecular Fluorescent Complementation (BiFC) as a tool for evaluating protein–protein interactions in living cells. The efficacy of BiFC was validated by a known interaction between replicase protein 1a (p1a) and protein 2a (p2a) at the endoplasmic reticulum (ER) site of viral replication. Additionally, co-expression in planta of a bona fide pair of interacting protein partners of p1a and p2a had resulted in the assembly of a functional replicase. Subsequent BiFC assays in conjunction with mCherry labeled ER as a fluorescent cellular marker revealed that CP physically interacts with p2a, but not p1a, and this CP:p2a interaction occurs at the cytoplasmic phase of the ER. The significance of the CP:p2a interaction in BMV replication and genome packaging is discussed. - Highlights: • YFP fusion proteins of BMV p1a and p2a are biologically active. • Self-interaction was observed for p1a, p2a and CP. • CP interacts with p2a but not p1a. • Majority of reconstituted YFP resulting from bona fide fusion protein partners localized on ER.

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

    NASA Astrophysics Data System (ADS)

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

    The seasonal patterns of phytoplankton biomass and production were determined in the North Water, located between Greenland and Ellesmere Island (Canadian Arctic), in August 1997, April-July 1998, and August-September 1999. The patterns differed among the four defined regions of this large polynya, i.e. North (>77.5°N), East (>75°W), West (<75°W), and South (<76°N). Phytoplankton biomass and production were low during April throughout the North Water. Biomass first increased in the East during April. From there, the biomass spread north- and westwards during May-June, when the bloom culminated (chlorophyll a concentrations up to 19.8 mg m -3). The large-sized (>5 μm) fraction dominated the biomass and production during the bloom. During July, August, and September, biomass and production decreased over the whole region, with the highest biomass, dominated by large cells, occurring in the North. The annual particulate and dissolved phytoplankton production were the highest ever reported for the high Arctic, reaching maximum values of 254 and 123 g C m -2 yr -1, respectively, in the East. Rates in the North and West were considerably lower than in the East (ca. two- and three-fold, respectively). The f-ratios (i.e. ratio of new to total production), derived from the size structure of phytoplankton, were high north of 76°N (0.4-0.7). Regionally, this indicated a high potential export of particulate organic carbon ( EPOC) from the phytoplankton community to other trophic compartments and/or downwards in the East (155 g C m -2 yr -1), with lower values in the North and West (i.e. 77 and 42 g C m -2 yr -1, respectively). The seasonal and spatial patterns of EPOC were consistent with independent estimates of potential carbon export. Phytoplankton biomass and production were generally dominated by the large size fraction, whereas EPOC seemed to be dominated by the large size fraction early in the season and by the small size fraction (<5 μm) from June until the end

  2. Growth inhibition of cultured marine phytoplankton by toxic algal-derived polyunsaturated aldehydes.

    PubMed

    Ribalet, François; Berges, John A; Ianora, Adrianna; Casotti, Raffaella

    2007-12-15

    . Concentrations used are in a significant range for affecting growth and performance of phytoplankton living in close vicinity of PUA-producing algae. Thus, PUAs may act as allelochemicals by mediating interactions among planktonic organisms. PMID:17942163

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  4. Identifying the factors affecting phytoplankton abundance dynamics in Shihmen Reservoir, Taiwan

    NASA Astrophysics Data System (ADS)

    Kuo, Yi-Ming; Chuang, Illy; Chu, Hone-Jay; Wu, Jiunn-Tzong; Jang, Cheng-Shin

    2013-04-01

    Investigations of multiple temporal distributions of phytoplankton dynamics through environmental variables in water bodies over extensive areas remain relatively scarce. This study focused on the determination of the key factors regulating temporal and spatial variations of phytoplankton abundance at three monitoring sites in Shihmen Reservoir within five years (2006-2010). Dynamic factor analysis (DFA), a dimension-reduction technique, was designed to identify the underlying latent effects in multiple time series and interactions between explanatory variables (i.e., environmental variables) and the response variable (phytoplankton abundance). The optimal DFA model successfully described the dynamics of phytoplankton abundance in the Shihmen Reservoir. The results demonstrated that water temperature, water level, COD, BOD, and DO considerably affected phytoplankton abundance at most of the monitoring sites. Among them, water temperature, water level, and COD significantly affected phytoplankton abundance at all three sites, indicating that these variables contributed more to the long-term dynamics of phytoplankton abundance than other variables at the surface water of Shihmen Reservoir. The influx and efflux of Reservoir altering hydrological conditions in Shihmen Reservoir may attenuate the nutrients effects on phytoplankton abundance. In this study, BOD and DO are the other crucial water quality factors that control variations of phytoplankton. The explanatory variables mainly explain the dynamics of phytoplankton abundance than common trends do. In the future, the water manager may consider these variables to propose strategies to manage water quality in Shihmen Reservoir.

  5. Standing stocks, production, and respiration of phytoplankton and heterotrophic bacteria in the western Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Kirchman, David L.; Hill, Victoria; Cottrell, Matthew T.; Gradinger, Rolf; Malmstrom, Rex R.; Parker, Alexander

    2009-08-01

    Standing stocks and production rates for phytoplankton and heterotrophic bacteria were examined during four expeditions in the western Arctic Ocean (Chukchi Sea and Canada Basin) in the spring and summer of 2002 and 2004. Rates of primary production (PP) and bacterial production (BP) were higher in the summer than in spring and in shelf waters than in the basin. Most surprisingly, PP was 3-fold higher in 2004 than in 2002; ice-corrected rates were 1581 and 458 mg C m -2 d -1, respectively, for the entire region. The difference between years was mainly due to low ice coverage in the summer of 2004. The spatial and temporal variation in PP led to comparable variation in BP. Although temperature explained as much variability in BP as did PP or phytoplankton biomass, there was no relationship between temperature and bacterial growth rates above about 0 °C. The average ratio of BP to PP was 0.06 and 0.79 when ice-corrected PP rates were greater than and less than 100 mg C m -2 d -1, respectively; the overall average was 0.34. Bacteria accounted for a highly variable fraction of total respiration, from 3% to over 60% with a mean of 25%. Likewise, the fraction of PP consumed by bacterial respiration, when calculated from growth efficiency (average of 6.9%) and BP estimates, varied greatly over time and space (7% to >500%). The apparent uncoupling between respiration and PP has several implications for carbon export and storage in the western Arctic Ocean.

  6. Temporal variation of phytoplankton growth and grazing loss in the west coast of Peninsular Malaysia.

    PubMed

    Lim, Joon Hai; Lee, Choon Weng; Kudo, Isao

    2015-05-01

    Phytoplankton growth (μ) and grazing loss (g) rates were measured monthly by the Landry-Hassett dilution method over a 2-year period at both estuarine (Klang) and coastal water (Port Dickson) systems along the Straits of Malacca. Chlorophyll a (Chl a) concentration ranged from 0.20 to 4.47 μg L(-1) at Klang except on two occasions when Chl a spiked above 10 μg L(-1). In contrast, Chl a concentrations were relatively stable at Port Dickson (0.14 to 2.76 μg L(-1)). From the rate measurements, μ was higher (t = 2.01, df = 43, p < 0.05) at Klang (0.30 to 2.26 day(-1)) than at Port Dickson (0.18 to 1.66 day(-1)), but g was not significantly different (p > 0.80). g ranged from 0.30 to 1.50 and 0.21 to 1.51 day(-1) at Klang and Port Dickson, respectively. In this study, grazing loss was coupled to phytoplankton growth, and the ratio of g/μ or grazing pressure which estimates the proportion of primary production grazed was 50% at Klang and lower than at Port Dickson (68%; t = 2.213, df = 36, p < 0.05). We found that the higher growth rates in a eutrophic system, i.e., Klang, were not matched by higher grazing loss, and this may have implications for the biogeochemical cycling in coastal waters. PMID:25864082

  7. The effects of isolation on the demography and genetic diversity of long-lived species: Implications for conservation and management of the gopher tortoise (Gopherus polyphemus)

    USGS Publications Warehouse

    Ennen, J.R.; Birkhead, R.D.; Kreiser, B.R.; Gaillard, D.L.; Qualls, C.P.; Lovich, J.E.

    2011-01-01

    In the southeastern United States, habitat loss has fragmented the landscape and isolated many populations of this region's flora and fauna, which has presumably resulted in smaller population sizes and reduced levels of genetic diversity. For example, forestry practices and anthropogenic disturbances are both cited as factors fragmenting the once extensive range of Gopherus polyphemus. One localized, but extreme, source of fragmentation was the impoundment of the Chattahoochee River in 1963 to form Walter F. George Reservoir along the border of Georgia and Alabama. The formation of this reservoir isolated populations of G. polyphemus on two newly created islands providing a natural laboratory to explore the demographics and genetic effects of fragmentation on a long-lived species. These populations were first surveyed in 1984 and, 21 years later, we revisited them to collect demographic data and tissue samples for genetic analysis. We genotyped all individuals for 10 microsatellite loci, and we tested these data for bottlenecks and compared them to levels of genetic diversity for populations from other portions of the range. We found 45 and two individuals on the larger and smaller islands, respectively. On the large island, however, the population size was identical to the 1984 survey. Only the population structure based on estimated age differed between the 1984 and 2004 surveys, while population size structure based on carapace length, sex ratio, and sex-specific growth rates did not differ. The population of the large island showed genetic evidence of a past bottleneck. The genetic diversity indices from the population of the large island, however, were comparable to or greater than those found at mainland sites, in particular from western populations.

  8. Effects of nano-TiO2 on perfluorooctanesulfonate bioaccumulation in fishes living in different water layers: Implications for enhanced risk of perfluorooctanesulfonate.

    PubMed

    Qiang, Liwen; Pan, Xiaoyu; Zhu, Lingyan; Fang, Shuhong; Tian, Shengyan

    2016-01-01

    Nano-titanium dioxide (nano-TiO2) is one of the most universal engineered nano-materials while perfluorooctanesulfonate (PFOS) is a typical new persistent organic pollutant. They are widely used and present in aquatic environment. In this study, a novel semi-static multilayer microcosm was setup to investigate the impacts of nano-TiO2 on PFOS bioaccumulation in fish species [Danio rerio (D. rerio), Ctenopharyngodon idella (C. idella), Hypostomus plecostomus (H. plecostomus)] living in different vertical layers. As a result of aggregation and deposition, the concentration of TiO2 increased from upper to bottom layers in the water column. Concomitantly, due to adsorption of PFOS on the nano-TiO2 particles, PFOS also displayed an increasing trend from upper to bottom layer. Owing to ingestion of the TiO2-PFOS complexes, more PFOS was taken-up by fish. With the aid of intestinal fluid, PFOS was readily released from TiO2 particles and absorbed by fish. As a result, accumulation of PFOS in whole fish was facilitated and the bioaccumulation factors of PFOS in D. rerio, C. idella and H. plecostomus were 3.01, 2.42 and 1.11 times of that in the groups without TiO2. However, TiO2 aggregates were too large to penetrate biological membranes to participate body circulation, and no significant accumulation of TiO2 was observed in fish muscle. The results suggested that the ecological risk of PFOS could be enhanced due to the presence of nano-TiO2 in water. PMID:26554840

  9. A Lower Initial Abundance of Short-lived 41Ca in the Early Solar System and Its Implications for Solar System Formation

    NASA Astrophysics Data System (ADS)

    Liu, Ming-Chang; Chaussidon, Marc; Srinivasan, Gopalan; McKeegan, Kevin D.

    2012-12-01

    The short-lived radionuclide 41Ca plays an important role in constraining the immediate astrophysical environment and the formation timescale of the nascent solar system due to its extremely short half-life (0.1 Myr). Nearly 20 years ago, the initial ratio of 41Ca/40Ca in the solar system was determined to be (1.41 ± 0.14) × 10-8, primarily based on two Ca-Al-rich Inclusions (CAIs) from the CV chondrite Efremovka. With an advanced analytical technique for isotopic measurements, we reanalyzed the potassium isotopic compositions of the two Efremovka CAIs and inferred the initial ratios of 41Ca/40Ca to be (2.6 ± 0.9) × 10-9 and (1.4 ± 0.6) × 10-9 (2σ), a factor of 7-10 lower than the previously inferred value. Considering possible thermal processing that led to lower 26Al/27Al ratios in the two CAIs, we propose that the true solar system initial value of 41Ca/40Ca should have been ~4.2 × 10-9. Synchronicity could have existed between 26Al and 41Ca, indicating a uniform distribution of the two radionuclides at the time of CAI formation. The new initial 41Ca abundance is 4-16 times lower than the calculated value for steady-state galactic nucleosynthesis. Therefore, 41Ca could have originated as part of molecular cloud materials with a free decay time of 0.2-0.4 Myr. Alternative possibilities, such as a last-minute input from a stellar source and early solar system irradiation, could not be definitively ruled out. This underscores the need for more data from diverse CAIs to determine the true astrophysical origin of 41Ca.

  10. Bio-optical observations of the 2004 Labrador Sea phytoplankton bloom

    NASA Astrophysics Data System (ADS)

    Strutton, Peter G.; Martz, Todd R.; Degrandpre, Michael D.; McGillis, Wade R.; Drennan, William M.; Boss, Emmanuel

    2011-11-01

    A unique time series of moored bio-optical measurements documented the 2004 spring-summer bloom in the southern Labrador Sea. In situ and satellite chlorophyll data show that chlorophyll levels in the 2004 bloom were at the upper end of those typically observed in this region. Satellite chlorophyll and profiling float temperature/salinity data show that the main bloom, which typically peaks in June/July, is often preceded by ephemeral mixed layer shoaling and a lesser, short-lived bloom in May; this was the case in 2004. The particulate backscatter to beam attenuation ratio (bbp[470 nm]/Cp[660 nm]) showed peaks in the relative abundance of small particles at bloom initiation and during the decline of the bloom, while larger particles dominated during the bloom. Chlorophyll/Cp and bbp/chlorophyll were correlated with carbon export and dominated by changes in the pigment per cell associated with lower light levels due to enhanced attenuation of solar radiation during the bloom. An NPZ (nutrients, phytoplankton, zooplankton) model captured the phytoplankton bloom and an early July peak in zooplankton. Moored acoustic Doppler current profiler (ADCP) data showed an additional mid-June peak in zooplankton biomass which was attributed to egg-laying copepods. The data reported here represent one of the few moored time series of Cp, bbp and chlorophyll extending over several months in an open ocean region. Interpretation of data sets such as this will become increasingly important as these deployments become more commonplace via ocean observing systems. Moreover, these data contribute to the understanding of biological-physical coupling in a biogeochemically important, yet poorly studied region.

  11. Acid rain stimulation of Lake Michigan phytoplankton growth

    USGS Publications Warehouse

    Manny, Bruce A.; Fahnenstiel, G.L.; Gardner, W.S.

    1987-01-01

    Three laboratory experiments demonstrated that additions of rainwater to epilimnetic lake water collected in southeastern Lake Michigan stimulated chlorophyll a production more than did additions of reagent-grade water during incubations of 12 to 20 d. Chlorophyll a production did not begin until 3–5 d after the rain and lake water were mixed. The stimulation caused by additions of rain acidified to pH 3.0 was greater than that caused by additions of untreated rain (pH 4.0–4.5). Our results support the following hypotheses: (1) Acid rain stimulates the growth of phytoplankton in lake water; (2) phosphorus in rain appears to be the factor causing this stimulation. We conclude that acid rain may accelerate the growth of epilimnetic phytoplankton in Lake Michigan (and other similar lakes) during stratification when other sources of bioavailable phosphorus to the epilimnion are limited

  12. Phytoplankton dynamics in three Rocky Mountain Lakes, Colorado, USA

    USGS Publications Warehouse

    McKnight, Diane M.; Smith, R.L.; Bradbury, J.P.; Baron, J.S.; Spaulding, S.

    1990-01-01

    In 1984 and 1985 in Loch Vale, Rocky Mountain National Park, 3 periods were evident: 1) a spring bloom, during snowmelt, of the planktonic diatom Asterionella formosa, 2) a mid-summer period of minimal algal abundance, and 3) a fall bloom of the blue-green alga Oscillatoria limnetica. Seasonal phytoplankton dynamics are controlled partially by the rapid flushing rate during snowmelt and the transport of phytoplankton from the highest lake to the lower lakes by the stream, Icy Brook. During snowmelt, the A. formosa population in the most downstream lake has a net rate of increase of 0.34 d-1. The decline in A. formosa after snowmelt may be related to grazing by developing zooplankton populations. -from Authors

  13. Ocean fertilization experiments may initiate a large scale phytoplankton bloom

    NASA Astrophysics Data System (ADS)

    Neufeld, Zoltán; Haynes, Peter H.; Garçon, Véronique; Sudre, Joël

    2002-06-01

    Oceanic plankton plays an important role in the marine food chain and through its significant contribution to the global carbon cycle can also influence the climate. Plankton bloom is a sudden rapid increase of the population. It occurs naturally in the North Atlantic as a result of seasonal changes. Ocean fertilization experiments have shown that supply of iron, an important trace element, can trigger a phytoplankton bloom in oceanic regions with low natural phytoplankton density. Here we use a simple mathematical model of the combined effects of stirring by ocean eddies and plankton evolution to consider the impact of a transient local perturbation, e.g. in the form of iron enrichment as in recent `ocean fertilization' experiments. The model not only explains aspects of the bloom observed in such experiments but predicts the unexpected outcome of a large scale bloom that in its extent could be comparable to the spring bloom in the North Atlantic.

  14. Ocean color observations of phytoplankton distributions and primary productivity

    NASA Technical Reports Server (NTRS)

    Esaias, W.

    1988-01-01

    The primary goal of this activity is to develop the means to assess the mean and variability of phytoplankton biomass and primary productivity on global scales. There are three major approaches whose goals are to provide global scale observations. These are processing and analysis of the complete CZCS data set in a consistent manner; preparing science mission and project implementation plans for the SeaWiFS sensor to be launched on LANDSAT 6 in 1991; and providing guidance to EOS flight projects for ocean color observations using the MODIS sensor planned for the Polar Platform in the mid 1990's. This processing presents the first consistent view of phytoplankton pigments on global scales, and analysis of this temporally undersampled data set is proving very instructive in specifying mission requirements for SeaWiFS and future algorithm development.

  15. Assessment of phytoplankton diversity as an indicator of water quality

    SciTech Connect

    Yergeau, S.E.; Lang, A.; Teeters, R.

    1997-08-01

    For the measurement of water quality in freshwater systems, there are established indices using macroinvertebrate larvae. There is no such comparable measure for marine and estuarine environments. A phytoplankton diversity index (PDI), whose basic form was conceived by Dr. Ruth Gyure of Save the Sound, Inc., is being investigated as a possible candidate to rectify this situation. Phytoplankton were chosen as the indicators of water quality since algae have short generation times and respond quickly to changing water quality conditions. The methodologies involved in this initial assessment of the PDI are incorporated into the Adopt-a-Harbor water quality monitoring program and its associated laboratory. The virtues of the procedures are that they are simple and quick to use, suitable for trained volunteers to carry out, easily reproducible, and amenable to quality assurance checks.

  16. Lidar investigations of phytoplankton distribution on the north Norwegian shelf

    SciTech Connect

    Babichenko, S.; Wassmann, P.

    1997-08-01

    The results of field studies of the small-scale spatial variability and seasonal dynamics of phytoplankton on the north Norwegian shelf are presented. The remote sensing has been carried out on board of RV {open_quotes}Jan Mayen{close_quotes} in May, June and September 1995. The tuneable lidar FLS-S based on excimer and dye-lasers has been used to measure the horizontal and vertical profiles of phytoplankton abundance. The data were collected in underway sensing along the tracks of 20 - 30 n.m. with horizontal spatial resolution of 100 m. In stratification measurements the lidar consistently sensed the water layers shifted to the depth with the step of 3 m.

  17. Phytoplankton Blooms Near the Cape of Good Hope

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Different phytoplankton communities color the ocean different shades of blue and green off the southern coast of South Africa in the December 22, 2000, Sea-viewing Wide Field-of-View Sensor (SeaWiFS) pass over the area. The convergence of two currents-the cold Benguela flowing North along the west coast of Africa, and a branch of the warm Agulhas heading west along the southern tip of the continent-causes upwelling cold, nutrient-rich water which feeds. The phytoplankton. The mixing cam also generate huge waves, making these waters very treacherous to sail. To learn more about the Benguela and Algulhas Currents, read A Clear Day Over the Agulhas Retroflection Image courtesy SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  18. The complete mitochondrial sequence of the"living fossil" Tricholepidion gertschi: structure, phylogenetic implications, and the description of a novel A/T asymmetrical bias

    SciTech Connect

    Nardi, F.; Frati, F.; Carapelli, A.; Dallai, R.; Boore, J.

    2002-06-23

    Traditionally, the 'Apterygota' has been thought to consist of five orders of wingless hexapods (Protura, Collembola, Diplura, Microcoryphia and Zygentoma) believed to be collectively basal to insects (i.e., the Pterygota). However, some studies have questioned this affinity with insects (Dallai, Abele, Spears, Nardi). Further, within these groups are hotly debated issues, including the monophyly of Entognata (Koch, 1997; Kukalova Peck, 1987), the monophyly of Diplura (Bilinski, 1993; Stys and Bilinski, 1990), the affinity between Collembola and Protura (Dallai, 1994; Kristensen, 1981) and the position of Lepidotrichidae (below). In fact, these relationships constitute one of the most debated issues in hexapod phylogeny. The family Lepidotrichidae was first described by (Silvestri, 1912) (1912: 'Lepidothricinae') from a Baltic Amber fossil (Lepidothrix pilifera Menge). The only living representative of this family is Tricholepidion gertschi Wygodzinski. Since this species was first described (Wygodzinsky, 1961) its phylogenetic position has been difficult to establish, due to an 'array of unique characters' that are difficult to interpret in a phylogenetic framework. Tricholepidion (and therefore the whole family Lepidotrichidae) has been considered either as belonging to the order Zygentoma (Kristensen, 1997; Wygodzinsky, 1961), or basal to the rest of the Zygentoma plus the Pterygota (Beutel, 2001; Bitsch and Bitsch, 2000; Staniczek, 2000), although the significance of some of the morphological characters on which these analyses are based have been questioned (Dallai et al., 2001; Kristensen, 1997). If the latter hypothesis proved to be true, the family Lepidotrichidae, would better deserve the ordinal rank. Since studies based on morphological characters have failed to give a satisfactory answer, a broad scale molecular study is under way ((Nardi et al., 2001), Frati et al, submitted, il Gomphiocephalus) in order to use mitochondrial genome sequences to study

  19. Sources and human exposure implications of concentrations of organophosphate flame retardants in dust from UK cars, classrooms, living rooms, and offices.

    PubMed

    Brommer, Sandra; Harrad, Stuart

    2015-10-01

    Concentrations of a number of organophosphate flame retardants (PFRs) were measured in floor dust collected from UK living rooms (n = 32), cars (n = 21), school and child daycare centre classrooms (n = 28), and offices (n = 61). While concentrations were overall broadly within the range of those reported previously for North America, Japan, and other European countries, median concentrations of TCIPP in all UK microenvironments exceeded those reported elsewhere in the world. Moreover, concentrations of TCIPP and TDCIPP in 2 UK car dust samples were--at 370 μg g(-1) and 740 μg g(-1) respectively--amongst the highest reported globally in indoor dust to date. Consistent with this, concentrations of TDCIPP in dust from UK cars exceed significantly those detected in the other microenvironments studied. Concentrations of EHDPP were shown for the first time to be significantly higher in classroom dust than in samples from other microenvironments. When compared to concentrations of PBDEs determined previously in the classroom dust samples; concentrations of all target PFRs exceeded substantially those of those PBDEs that are the principal constituents of the Penta- and Octa-BDE formulations. Moreover, while mass-based concentrations of BDE-209 exceeded those of most of our target PFRs, they still fell below those of TCIPP and EHDPP. In line with a previous observation in Sweden that indoor air contamination with TNBP was significantly lower in newer buildings; concentrations of TNBP in classroom dust were significantly higher in older compared to more recently-constructed schools. Consistent with the reported extensive use of TCIPP and TDCIPP in polyurethane foam, the highest concentrations of both TCIPP and TDCIPP in the classrooms studied, were observed in rooms containing the highest numbers of foam chairs (n = 31 and 18 respectively). Exposure to PFRs of both adults and young children via ingestion of indoor dust was estimated. While even our high-end exposure

  20. Atmospheric effects in the remote sensing of phytoplankton pigments

    NASA Technical Reports Server (NTRS)

    Gordon, H. R.; Clark, D. K.

    1980-01-01

    The accuracy with which relevant atmospheric parameters must be estimated to derive photoplankton pigment concentrations of a given accuracy, from measurements of the ocean's apparent spectral radiance at satellite altitudes, is examined. A phytoplankton pigment algorithm is developed which relates the pigment concentration (c) to the three ratios of upwelling radiance just beneath the sea surface which can be formed from wavelengths (lambda) 440, 520 and 550 nm.

  1. The Use of HPLC for the Characterization of Phytoplankton Pigments.

    PubMed

    Garrido, José L; Roy, Suzanne

    2015-01-01

    HPLC is still the technique of choice for the analysis and characterization of phytoplankton pigments. In this chapter we describe procedures for sample preparation and pigment extraction, and the use of octyl silica columns and pyridine-containing mobile phases to separate chlorophylls and carotenoids. The identification of pigments on the basis of their retention times and visible spectra, the preparation of pigment standards, and the quantitative analysis by either external or internal standard procedures are also described. PMID:26108510

  2. Phytoplankton as a fluorescent bioindicator of ecotoxicants in natural waters

    NASA Astrophysics Data System (ADS)

    Gostev, T.; Kouzminov, F.; Gorbunov, M.; Fadeev, V.

    2010-04-01

    The newest approach in the saturation fluorimetry of photosynthetic organisms by the example of phytoplankton was developed. The theoretical model and the inverse problem of the saturation fluorimetry are discussed. The results of evaluation of molecular photophysical parameters of alga Chlorella pyrenoidosa under various stress factors, such as presence of DCMU and Cu2+ ions are presented. The correlation between theese parameters and the parameters obtained using Fluorescence Induction and Relaxation technique is discussed.

  3. Phytoplankton bloom all along the coast of Southeast United States

    NASA Technical Reports Server (NTRS)

    2002-01-01

    All along the eastern and southern coasts of the United States, marine plants seem impervious to the onslaught of winter weather further north. In this true-color image from January 9, 2002, phytoplankton can be seen growing in the nation's coastal waters; their characteristic blue-green swirls are especially visible off the west coast of Florida. Fire locations are marked with red dots. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  4. Carbon-based ocean productivity and phytoplankton physiology from space

    NASA Astrophysics Data System (ADS)

    Behrenfeld, Michael J.; Boss, Emmanuel; Siegel, David A.; Shea, Donald M.

    2005-03-01

    Ocean biogeochemical and ecosystem processes are linked by net primary production (NPP) in the ocean's surface layer, where inorganic carbon is fixed by photosynthetic processes. Determinations of NPP are necessarily a function of phytoplankton biomass and its physiological status, but the estimation of these two terms from space has remained an elusive target. Here we present new satellite ocean color observations of phytoplankton carbon (C) and chlorophyll (Chl) biomass and show that derived Chl:C ratios closely follow anticipated physiological dependencies on light, nutrients, and temperature. With this new information, global estimates of phytoplankton growth rates (μ) and carbon-based NPP are made for the first time. Compared to an earlier chlorophyll-based approach, our carbon-based values are considerably higher in tropical oceans, show greater seasonality at middle and high latitudes, and illustrate important differences in the formation and demise of regional algal blooms. This fusion of emerging concepts from the phycological and remote sensing disciplines has the potential to fundamentally change how we model and observe carbon cycling in the global oceans.

  5. Terrestrial carbohydrates support freshwater zooplankton during phytoplankton deficiency

    PubMed Central

    Taipale, Sami J.; Galloway, Aaron W. E.; Aalto, Sanni L.; Kahilainen, Kimmo K.; Strandberg, Ursula; Kankaala, Paula

    2016-01-01

    Freshwater food webs can be partly supported by terrestrial primary production, often deriving from plant litter of surrounding catchment vegetation. Although consisting mainly of poorly bioavailable lignin, with low protein and lipid content, the carbohydrates from fallen tree leaves and shoreline vegetation may be utilized by aquatic consumers. Here we show that during phytoplankton deficiency, zooplankton (Daphnia magna) can benefit from terrestrial particulate organic matter by using terrestrial-origin carbohydrates for energy and sparing essential fatty acids and amino acids for somatic growth and reproduction. Assimilated terrestrial-origin fatty acids from shoreline reed particles exceeded available diet, indicating that Daphnia may convert a part of their dietary carbohydrates to saturated fatty acids. This conversion was not observed with birch leaf diets, which had lower carbohydrate content. Subsequent analysis of 21 boreal and subarctic lakes showed that diet of herbivorous zooplankton is mainly based on high-quality phytoplankton rich in essential polyunsaturated fatty acids. The proportion of low-quality diets (bacteria and terrestrial particulate organic matter) was <28% of the assimilated carbon. Taken collectively, the incorporation of terrestrial carbon into zooplankton was not directly related to the concentration of terrestrial organic matter in experiments or lakes, but rather to the low availability of phytoplankton. PMID:27510848

  6. Terrestrial carbohydrates support freshwater zooplankton during phytoplankton deficiency.

    PubMed

    Taipale, Sami J; Galloway, Aaron W E; Aalto, Sanni L; Kahilainen, Kimmo K; Strandberg, Ursula; Kankaala, Paula

    2016-01-01

    Freshwater food webs can be partly supported by terrestrial primary production, often deriving from plant litter of surrounding catchment vegetation. Although consisting mainly of poorly bioavailable lignin, with low protein and lipid content, the carbohydrates from fallen tree leaves and shoreline vegetation may be utilized by aquatic consumers. Here we show that during phytoplankton deficiency, zooplankton (Daphnia magna) can benefit from terrestrial particulate organic matter by using terrestrial-origin carbohydrates for energy and sparing essential fatty acids and amino acids for somatic growth and reproduction. Assimilated terrestrial-origin fatty acids from shoreline reed particles exceeded available diet, indicating that Daphnia may convert a part of their dietary carbohydrates to saturated fatty acids. This conversion was not observed with birch leaf diets, which had lower carbohydrate content. Subsequent analysis of 21 boreal and subarctic lakes showed that diet of herbivorous zooplankton is mainly based on high-quality phytoplankton rich in essential polyunsaturated fatty acids. The proportion of low-quality diets (bacteria and terrestrial particulate organic matter) was <28% of the assimilated carbon. Taken collectively, the incorporation of terrestrial carbon into zooplankton was not directly related to the concentration of terrestrial organic matter in experiments or lakes, but rather to the low availability of phytoplankton. PMID:27510848

  7. Nutrients and phytoplankton in the Gulf of Lions, northwestern Mediterranean

    NASA Astrophysics Data System (ADS)

    Cruzado, Antonio; Velasquez, Zoila R.

    1990-09-01

    The mostly oligotrophic character of the Mediterranean Sea is altered drastically in areas receiving the outflow from large rivers. The Gulf of Lions, receiving discharges from the Rhoˆne River, has nutrient and phytoplankton concentration much higher than the adjacent open northwestern Mediterranean Sea. A surface layer of freshwater, with thickness that varies with the meteorological conditions between 2 and 40 m, overlies the deeper open seawater; this is advected onto the shelf and influences an area that covers the eastern half of the Gulf of Lions. Most of the waters affected by the river discharges show property relationships indicating conservative behaviour, with very little or no loss of nutrients through phytoplankton uptake, particularly in winter. Phytoplankton populations in winter are sparse, with maximum densities just above and below the boundary between the fresh- and seawater. Diatoms are the main group of organisms, although dinoflagellates, coceolithophorids and cyanobacteria are abundant. Small heterotrophs (cilliates, tintinnids, etc.) are also abundant and are positively correlated with the diatoms. A water balance model, linking the river discharge to the advective fluxes of water and nutrients, is proposed. The primary productivity supported by such fluxes is estimated.

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

    PubMed

    Rohrlack, Thomas; Haande, Sigrid; Molversmyr, Åge; Kyle, Marcia

    2015-01-01

    Chytrid fungi are highly potent parasites of phytoplankton. They are thought to force phytoplankton organisms into an evolutionary arms race with high population diversity as the outcome. The underlying selection regime is known as Red Queen dynamics. However, our study suggests a more complex picture for chytrid parasitism in the cyanobacterium Planktothrix. Laboratory experiments identified a "cold thermal refuge", inside which Planktothrix can grow without chytrid infection. A field study in two Norwegian lakes underlined the ecological significance of this finding. The study utilized sediment DNA as a biological archive in combination with existing monitoring data. In one lake, temperature and light conditions forced Planktothrix outside the thermal refuge for most of the growing season. This probably resulted in Red Queen dynamics as suggested by a high parasitic pressure exerted by chytrids, an increase in Planktothrix genotype diversity over time, and a correlation between Planktothrix genotype diversity and duration of bloom events. In the second lake, a colder climate allowed Planktothrix to largely stay inside the thermal refuge. The parasitic pressure exerted by chytrids and Planktothrix genotype diversity remained low, indicating that Planktothrix successfully evaded the Red Queen dynamics. Episodic Planktothrix blooms were observed during spring and autumn circulation, in the metalimnion or under the ice. Interestingly, both lakes were dominated by the same or related Planktothrix genotypes. Taken together, our data suggest that, depending on environmental conditions, chytrid parasitism can impose distinct selection regimes on conspecific phytoplankton populations with similar genotype composition, causing these populations to behave and perhaps to evolve differently. PMID:26714010

  9. Competition among marine phytoplankton for different chelated iron species

    NASA Astrophysics Data System (ADS)

    Hutchins, David A.; Witter, Amy E.; Butler, Alison; Luther, George W.

    1999-08-01

    Dissolved-iron availability plays a critical role in controlling phytoplankton growth in the oceans,. The dissolved iron is overwhelmingly (~99%) bound to organic ligands with a very high affinity for iron, but the origin, chemical identity and biological availability of this organically complexed Fe is largely unknown. The release into sea water of complexes that strongly chelate iron could result from the inducible iron-uptake systems of prokaryotes (siderophore complexes) or by processes such as zooplankton-mediated degradation and release of intracellular material (porphyrin complexes). Here we compare the uptake of siderophore- and porphyrin-complexed 55Fe by phytoplankton, using both cultured organisms and natural assemblages. Eukaryotic phytoplankton efficiently assimilate porphyrin-complexed iron, but this iron source is relatively unavailable to prokaryotic picoplankton (cyanobacteria). In contrast, iron bound to a variety of siderophores is relatively more available to cyanobacteria than to eukaryotes, suggesting that the two plankton groups exhibit fundamentally different iron-uptake strategies. Prokaryotes utilize iron complexed to either endogenous or exogenous siderophores, whereas eukaryotes may rely on a ferrireductase system, that preferentially accesses iron chelated by tetradentate porphyrins, rather than by hexadentate siderophores. Competition between prokaryotes and eukaryotes for organically-bound iron may therefore depend on the chemical nature of available iron complexes, with consequences for ecological niche separation, plankton community size-structure and carbon export in low-iron waters.

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

    PubMed Central

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

    2016-01-01

    Variable climatic conditions strongly influence phytoplankton dynamics in estuaries globally. Our study area is Chesapeake Bay, a highly productive ecosystem providing natural resources, transportation, and recreation for nearly 16 million people inhabiting a 165,000-km2 watershed. Since World War II, nutrient over-enrichment has led to multiple ecosystem impairments caused by increased phytoplankton biomass as chlorophyll-a (chl-a). Doubled nitrogen (N) loadings from 1945–1980 led to increased chl-a, reduced water clarity, and low dissolved oxygen (DO), while decreased N loadings from 1981–2012 suggest modest improvement. The recent 30+ years are characterized by high inter-annual variability of chl-a, coinciding with irregular dry and wet periods, complicating the detection of long-term trends. Here, we synthesize time-series data for historical and recent N loadings (TN, NO2 + NO3), chl-a, floral composition, and net primary productivity (NPP) to distinguish secular changes caused by nutrient over-enrichment from spatio-temporal variability imposed by climatic conditions. Wet years showed higher chl-a, higher diatom abundance, and increased NPP, while dry years showed lower chl-a, lower diatom abundance, and decreased NPP. Our findings support a conceptual model wherein variable climatic conditions dominate recent phytoplankton dynamics against a backdrop of nutrient over-enrichment, emphasizing the need to separate these effects to gauge progress toward improving water quality in estuaries. PMID:27026279

  11. Phytoplankton community composition in nearshore coastal waters of Louisiana.

    PubMed

    Schaeffer, Blake A; Kurtz, Janis C; Hein, Michael K

    2012-08-01

    Phytoplankton community compositions within near-shore coastal and estuarine waters of Louisiana were characterized by group diversity, evenness, relative abundance and biovolume. Sixty-six taxa were identified in addition to eight potentially harmful algal genera including Gymnodinium sp. Phytoplankton group diversity was lowest at Vermillion Bay in February 2008, but otherwise ranged between 2.16 and 3.40. Phytoplankton evenness was also lowest at Vermillion Bay in February 2008, but otherwise ranged between 0.54 and 0.77. Dissolved oxygen increased with increased biovolume (R² = 0.85, p < 0.001) and biovolume decreased with increased light attenuation (R² = 0.34, p = 0.007), which supported the importance of light in regulating oxygen dynamics. Diatoms were dominant in relative abundance and biovolume at almost all stations and all cruises. Brunt-Väisälä frequency was used as a measure of water column stratification and was negatively correlated (p = 0.02) to diatom relative percent total abundance. PMID:22498318

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

    PubMed

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

    2016-01-01

    Variable climatic conditions strongly influence phytoplankton dynamics in estuaries globally. Our study area is Chesapeake Bay, a highly productive ecosystem providing natural resources, transportation, and recreation for nearly 16 million people inhabiting a 165,000-km(2) watershed. Since World War II, nutrient over-enrichment has led to multiple ecosystem impairments caused by increased phytoplankton biomass as chlorophyll-a (chl-a). Doubled nitrogen (N) loadings from 1945-1980 led to increased chl-a, reduced water clarity, and low dissolved oxygen (DO), while decreased N loadings from 1981-2012 suggest modest improvement. The recent 30+ years are characterized by high inter-annual variability of chl-a, coinciding with irregular dry and wet periods, complicating the detection of long-term trends. Here, we synthesize time-series data for historical and recent N loadings (TN, NO2 + NO3), chl-a, floral composition, and net primary productivity (NPP) to distinguish secular changes caused by nutrient over-enrichment from spatio-temporal variability imposed by climatic conditions. Wet years showed higher chl-a, higher diatom abundance, and increased NPP, while dry years showed lower chl-a, lower diatom abundance, and decreased NPP. Our findings support a conceptual model wherein variable climatic conditions dominate recent phytoplankton dynamics against a backdrop of nutrient over-enrichment, emphasizing the need to separate these effects to gauge progress toward improving water quality in estuaries. PMID:27026279

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  14. Study on the phytoplankton · in a large reservoir

    NASA Astrophysics Data System (ADS)

    Xia, Yicheng; Kuang, Qijun

    1992-12-01

    A comprehensive study on the community structure and function of the phytoplankton in Taipinghu Reservoir, the largest reservoir (9400 ha) in Anhui Province, China, was carried out during 1985 1986. A total of 175 species of algae belonging to 8 phyla and 87 genera was noted. The composition of phytoplankton was dominated by species of Chlorophyta, Cyanophyta and Bacillariophyta. The species number, cell density and biomass of the three groups were respectively 88%, 86.5% and 78.9% of the total phytoplankton. The weighted annual average biomass was 1.52 mg/L and cell density was 1.43×106 ind/L. The growth maximum was observed in summer. Diatoms were abundant in the region adjoining a river. A large number of flagellated algae such as Euglena and Chromulina occurred in the artificial fish culture bay. It can be inferred from the algal composition and total nitrogen concentration (1.48 mg/L) that this reservoir is a mesotrophic water body that had undergone slight natural eutrophication. Presented are an equation for the relation between cell density and biomass of algae and a newly developed method based on the energy flow principle in ecology for theoretically estimating algal fishery potential. The algae volumes of 128 species were measured for calculating the biomass.

  15. The search for phytoplankton applied remote sensing to the Barataria basin

    SciTech Connect

    Massasati, A.S.; Marstall, T.W.

    1997-08-01

    Mapping phytoplankton has been and still is an important issue in determining the productivity of major water bodies in the United States and around the world. While traditional procedures require an immense amount of time and manpower, remote sensing/GIS technology shows promise for a more cost effective and comprehensive solution for the mapping problem. Satellite Thematic Mapper and airborne CAMS data are used to identify and delineate phytoplankton. The physical properties of phytoplankton represented per pixel are measured and characterized into classes so that objective and statistically significant statements are made at the most elementary level. On this qualitative foundation, pixels are aggregated into units of phytoplankton concentration. These pixels are characterized by class groups and compared to well known facts and field observations of phytoplankton to determine its concentration. The procedure has been applied to the Barataria Bay drainage basin in Southern Louisiana and showed strong possibilities in mapping phytoplankton concentrations.

  16. Freezing of living cells

    SciTech Connect

    Mazur, P.

    1985-01-01

    It can be calculated that a living cell will survive more than 5000 years at -196/sup 0/C. This ability to essentially stop biological time has important implications in medicine and agriculture, and in biological research. In medicine the chief implications are in the banking of transplantable tissues and organs and in in vitro fertilization. In agriculture the applications stem in part from the role of frozen embryos in amplifying the number of calves produced by high quanlity cows. The problem is how can cells survive both the cooling to such very low temperatures and the return to normal temperatures. The answers involve fundamental characteristics of cells such as the permeability of their surface membranes to water and solutes. These characteristics determine whether or not cells undergo lethal internal ice formation and other response during freezing and thawing. 27 refs., 12 figs.

  17. Controls on marine carbon fluxes via phytoplankton-mesoplankton interactions in continental shelf waters

    SciTech Connect

    Shapiro, L.; Sherr, B.F.; Sherr, E.B.

    1992-01-01

    The project is an in-depth evaluation of the phytoplankton [yields] phagotrophic protist trophic link. The principal goals of the first year are to develop methods for the second phase of the Ocean Margins Program: investigations in the field. Our project is focused on: impact of grazing by phagotrophic protists on phytoplankton; impact of grazing by phagotrophic protists on bacterioplankton; taxon-specific growth rates of phytoplankton in situ, as they are affected by phagotrophy rates.

  18. Living My Family's Story

    PubMed Central

    Underhill, Meghan L.; Lally, Robin M.; Kiviniemi, Marc T.; Murekeyisoni, Christine; Dickerson, Suzanne S.

    2013-01-01

    Background Based on known or suggested genetic risk factors, a growing number of women now live with knowledge of a potential cancer diagnosis that may never occur. Given this, it is important to understand the meaning of living with high risk for hereditary breast cancer. Objective The objective of the study was to explore how women at high risk for hereditary breast cancer (1) form self-identity, (2) apply self-care strategies toward risk, and (3) describe the meaning of care through a high-risk breast program. Methods Interpretive hermeneutic phenomenology guided the qualitative research method. Women at high risk for hereditary breast cancer were recruited from a high-risk breast program. Open-ended interview questions focused on experiences living as women managing high risk for breast cancer. Consistent with hermeneutic methodology, the principal investigator led a team to analyze the interview transcripts. Results Twenty women participated in in-depth interviews. Analysis revealed that women describe their own identity based on their family story and grieve over actual and potential familial loss. This experience influences self-care strategies, including seeking care from hereditary breast cancer risk experts for early detection and prevention, as well as maintaining a connection for early treatment “when” diagnosis occurs. Conclusions Healthy women living with high risk for hereditary breast cancer are living within the context of their family cancer story, which influences how they define themselves and engage in self-care. Implications for Practice Findings present important practical, research, and policy information regarding health promotion, psychosocial assessment, and support for women living with this risk. PMID:22544165

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

    NASA Technical Reports Server (NTRS)

    Rousseaux, Cecile Severine; Gregg, Watson W.

    2013-01-01

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

  20. Healthy Living

    MedlinePlus

    ... health. Some you cannot control, such as your genetic makeup or your age. But you can make changes to your lifestyle. By taking steps toward healthy living, you can help reduce your risk of heart disease, cancer, stroke and other serious diseases: Get ...

  1. Retiring Lives

    ERIC Educational Resources Information Center

    Carnell, Eileen, Ed.; Lodge, Caroline, Ed.

    2009-01-01

    "Retiring Lives" presents fourteen personal real life stories from people at various stages of retiring. Each author recounts their own story about retiring, bringing together many aspects of the experiences: the social, psychological and practical. These inspirational and illustrated stories will encourage the reader to hold up these experiences…

  2. Learn & Live.

    ERIC Educational Resources Information Center

    Burness, Patty, Ed.; Snider, William, Ed.

    Along with a companion documentary video, "Learn & Live," this resource manual focuses on innovative schools around the country that are integrating technology and involving parents, business, and the community. Ten chapters are divided into four sections. In Section 1, "Students," two chapters look at learning and assessment. The two chapters in…

  3. Outdoor Living.

    ERIC Educational Resources Information Center

    Cotter, Kathy

    Course objectives and learning activities are contained in this curriculum guide for a 16-week home economics course which teaches cooking and sewing skills applicable to outdoor living. The course goals include increasing male enrollment in the home economics program, developing students' self-confidence and ability to work in groups, and…

  4. Porticoccus hydrocarbonoclasticus sp. nov., an aromatic hydrocarbon-degrading bacterium identified in laboratory cultures of marine phytoplankton.

    PubMed

    Gutierrez, Tony; Nichols, Peter D; Whitman, William B; Aitken, Michael D

    2012-02-01

    A marine bacterium, designated strain MCTG13d, was isolated from a laboratory culture of the dinoflagellate Lingulodinium polyedrum CCAP1121/2 by enrichment with polycyclic aromatic hydrocarbons (PAHs) as the sole carbon source. Based on 16S rRNA gene sequence comparisons, the strain was most closely related to Porticoccus litoralis IMCC2115(T) (96.5%) and to members of the genera Microbulbifer (91.4 to 93.7%) and Marinimicrobium (90.4 to 92.0%). Phylogenetic trees showed that the strain clustered in a distinct phyletic line in the class Gammaproteobacteria for which P. litoralis is presently the sole cultured representative. The strain was strictly aerobic, rod shaped, Gram negative, and halophilic. Notably, it was able to utilize hydrocarbons as sole sources of carbon and energy, whereas sugars did not serve as growth substrates. The predominant isoprenoid quinone of strain MCTG13d was Q-8, and the dominant fatty acids were C(16:1ω7c), C(18:1ω7c), and C(16:0). DNA G+C content for the isolate was 54.9 ± 0.42 mol%. Quantitative PCR primers targeting the 16S rRNA gene of this strain showed that this organism was common in other laboratory cultures of marine phytoplankton. On the basis of phenotypic and genotypic characteristics, strain MCTG13d represents a novel species of Porticoccus, for which the name Porticoccus hydrocarbonoclasticus sp. nov. is proposed. The discovery of this highly specialized hydrocarbon-degrading bacterium living in association with marine phytoplankton suggests that phytoplankton represent a previously unrecognized biotope of novel bacterial taxa that degrade hydrocarbons in the ocean. PMID:22139001

  5. Porticoccus hydrocarbonoclasticus sp. nov., an Aromatic Hydrocarbon-Degrading Bacterium Identified in Laboratory Cultures of Marine Phytoplankton

    PubMed Central

    Nichols, Peter D.; Whitman, William B.; Aitken, Michael D.

    2012-01-01

    A marine bacterium, designated strain MCTG13d, was isolated from a laboratory culture of the dinoflagellate Lingulodinium polyedrum CCAP1121/2 by enrichment with polycyclic aromatic hydrocarbons (PAHs) as the sole carbon source. Based on 16S rRNA gene sequence comparisons, the strain was most closely related to Porticoccus litoralis IMCC2115T (96.5%) and to members of the genera Microbulbifer (91.4 to 93.7%) and Marinimicrobium (90.4 to 92.0%). Phylogenetic trees showed that the strain clustered in a distinct phyletic line in the class Gammaproteobacteria for which P. litoralis is presently the sole cultured representative. The strain was strictly aerobic, rod shaped, Gram negative, and halophilic. Notably, it was able to utilize hydrocarbons as sole sources of carbon and energy, whereas sugars did not serve as growth substrates. The predominant isoprenoid quinone of strain MCTG13d was Q-8, and the dominant fatty acids were C16:1ω7c, C18:1ω7c, and C16:0. DNA G+C content for the isolate was 54.9 ± 0.42 mol%. Quantitative PCR primers targeting the 16S rRNA gene of this strain showed that this organism was common in other laboratory cultures of marine phytoplankton. On the basis of phenotypic and genotypic characteristics, strain MCTG13d represents a novel species of Porticoccus, for which the name Porticoccus hydrocarbonoclasticus sp. nov. is proposed. The discovery of this highly specialized hydrocarbon-degrading bacterium living in association with marine phytoplankton suggests that phytoplankton represent a previously unrecognized biotope of novel bacterial taxa that degrade hydrocarbons in the ocean. PMID:22139001

  6. [Ecological characteristics of phytoplankton in Suining tributary under bio-remediation].

    PubMed

    Liu, Dongyan; Zhao, Jianfu; Zhang, Yalei; Ma, Limin

    2005-04-01

    Based on the analyses of phytoplankton community in the treated and untreated reaches of Suining tributary of Suzhou River, this paper studied the effects of bio-remediation on phytoplankton. As the result of the remediation, the density and Chl-a content of phytoplankton in treated reach were greatly declined, while the species number and Shannon-Wiener diversity index ascended obviously. The percentage of Chlorophyta and Baeillariophyta ascended, and some species indicating medium-and oligo-pollution were found. All of these illustrated that bio-remediation engineering might significantly benefit to the improvement of phytoplankton community structure and water quality. PMID:16011171

  7. Exploring the Link between Micronutrients and Phytoplankton in the Southern Ocean during the 2007 Austral Summer

    PubMed Central

    Hassler, Christel S.; Sinoir, Marie; Clementson, Lesley A.; Butler, Edward C. V.

    2012-01-01

    Bottle assays and large-scale fertilization 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 whether micronutrients other than iron (Zn, Co, Cu, Cd, Ni) need to be considered as parameters for controlling the phytoplankton growth from the Australian Subantarctic to the Polar Frontal Zones during the austral summer 2007. Analysis of nutrient disappearance ratios, suggested differential zones in phytoplankton growth control in the study region with a most intense phytoplankton growth limitation between 49 and 50°S. Comparison of micronutrient disappearance ratios, metal distribution, and biomarker pigments used to identify dominating phytoplankton groups, demonstrated that a complex interaction between Fe, Zn, and Co might exist in the study region. Although iron remains the pivotal micronutrient for phytoplankton growth and community structure, Zn and Co are also important for the nutrition and the growth of most of the dominating phytoplankton groups in the Subantarctic Zone region. 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. PMID:22787456

  8. PHYTOPLANKTON DYNAMICS IN A GULF OF MEXICO ESTUARY: THE POTENTIAL USE OF PHOTO-PHYSIOLOGY AND ALGAL PHOSPHATASE ACTIVITY TO PREDICT NUTRIENT STATUS.

    EPA Science Inventory

    Development of rapid techniques to determine in situ phytoplankton nutrient status could facilitate understanding of phytoplankton growth and species succession. Variable fluorescence parameters of phytoplankton communities can be easily and rapidly measured, and changes in param...

  9. Phytoplankton of the Swan-Canning Estuary: a comparison of nitrogen uptake by different bloom assemblages

    NASA Astrophysics Data System (ADS)

    Horner Rosser, S. M. J.; Thompson, Peter A.

    2001-09-01

    Spring chlorophyte-, summer dinophyte- and autumn cryptophyte-dominated phytoplankton blooms occurring in the upper reaches of the Swan-Canning Estuary have been studied to compare species composition and diurnal distribution and to determine preferential uptake rates for different nitrogen sources. Species distribution patterns over diurnal cycles showed dinophyte and cryptophyte species exhibiting diurnal vertical migration patterns which changed over a three-week bloom period. The dinophyte and cryptophyte behaviour appeared to be related to measured changes in ambient nitrogen profiles over the course of the bloom. Chlorophyte species were not shown to be strongly migratory over diurnal periods. Absolute uptake rates (, approximating Pmax) for nitrogen, in the form of 15NO3-, 15NH4+ or 15N-urea, were compared between seasonal bloom assemblages and ranged between 0·02 and 12 µg N l-1 h-1 (NO3 0·02-7; NH4 0·4-9; urea 0·1-12 µg N l-1implicated in supporting these blooms. Results indicated no physiological preference at any depth for NOphytoplankton growth.

  10. Survival of Nannochloropsis Phytoplankton in Hypervelocity Impact Events up to Velocities of 6.07 km/s

    NASA Astrophysics Data System (ADS)

    Pasini, D. L. S.; Price, M. C.; Burchell, M. J.; Cole, M. J.

    2013-09-01

    Studies have previously been conducted to verify the survivability of living cells during hypervelocity impact events to test the panspermia and lithopanspermia hypothesis [1], [2]. It has been demonstrated that bacteria survive impacts up to 5.4 km s-1 (approx. shock pressure 30 GPa) - albeit with a low probability of survival [1] whilst larger more complex objects (such as seeds) break up at ~1 km s-1 [2]. The survivability of yeast spores in impacts up to 7.4 km s-1 has also recently been shown [3]. We demonstrate here the survivability of Nannochloropsis Phytoplankton, a eukaryotic photosynthesizing autotroph found in the 'euphotic zone'(sunlit surface layers of oceans) [4] at impact velocities up to 6.07 km s-1. Phytoplankton from a culture sample was frozen and then fired into water (to simulate oceanic impacts, as described in [5]) using a light gas gun (LGG) [6]. The water was then retrieved and placed into a sealed culture vessel and left under a constant light source to check the viability of any remnant organisms.

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

    NASA Astrophysics Data System (ADS)

    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

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

    PubMed

    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

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

    PubMed Central

    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

  14. Biodiversity Increases the Productivity and Stability of Phytoplankton Communities

    PubMed Central

    Corcoran, Alina A.; Boeing, Wiebke J.

    2012-01-01

    Global biodiversity losses provide an immediate impetus to elucidate the relationships between biodiversity, productivity and stability. In this study, we quantified the effects of species richness and species combination on the productivity and stability of phytoplankton communities subject to predation by a single rotifer species. We also tested one mechanism of the insurance hypothesis: whether large, slow-growing, potentially-defended cells would compensate for the loss of small, fast-growing, poorly-defended cells after predation. There were significant effects of species richness and species combination on the productivity, relative yield, and stability of phytoplankton cultures, but the relative importance of species richness and combination varied with the response variables. Species combination drove patterns of productivity, whereas species richness was more important for stability. Polycultures containing the most productive single species, Dunaliella, were consistently the most productive. Yet, the most species rich cultures were the most stable, having low temporal variability in measures of biomass. Polycultures recovered from short-term negative grazing effects, but this recovery was not due to the compensation of large, slow-growing cells for the loss of small, fast-growing cells. Instead, polyculture recovery was the result of reduced rotifer grazing rates and persisting small species within the polycultures. Therefore, although an insurance effect in polycultures was found, this effect was indirect and unrelated to grazing tolerance. We hypothesize that diverse phytoplankton assemblages interfered with efficient rotifer grazing and that this “interference effect” facilitated the recovery of the most productive species, Dunaliella. In summary, we demonstrate that both species composition and species richness are important in driving patterns of productivity and stability, respectively, and that stability in biodiverse communities can result

  15. Structure and dynamics of phytoplankton in an Amazon lake, Brazil.

    PubMed

    Silva, Ise de Goreth; Moura, Ariadne do Nascimento; Dantas, Enio Wocyli; Bittencourt-Oliveira, Maria do Carmo

    2010-12-01

    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 30 cm 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, their biomass

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

    PubMed Central

    Haande, Sigrid; Molversmyr, Åge

    2015-01-01

    Chytrid fungi are highly potent parasites of phytoplankton. They are thought to force phytoplankton organisms into an evolutionary arms race with high population diversity as the outcome. The underlying selection regime is known as Red Queen dynamics. However, our study suggests a more complex picture for chytrid parasitism in the cyanobacterium Planktothrix. Laboratory experiments identified a “cold thermal refuge”, inside which Planktothrix can grow without chytrid infection. A field study in two Norwegian lakes underlined the ecological significance of this finding. The study utilized sediment DNA as a biological archive in combination with existing monitoring data. In one lake, temperature and light conditions forced Planktothrix outside the thermal refuge for most of the growing season. This probably resulted in Red Queen dynamics as suggested by a high parasitic pressure exerted by chytrids, an increase in Planktothrix genotype diversity over time, and a correlation between Planktothrix genotype diversity and duration of bloom events. In the second lake, a colder climate allowed Planktothrix to largely stay inside the thermal refuge. The parasitic pressure exerted by chytrids and Planktothrix genotype diversity remained low, indicating that Planktothrix successfully evaded the Red Queen dynamics. Episodic Planktothrix blooms were observed during spring and autumn circulation, in the metalimnion or under the ice. Interestingly, both lakes were dominated by the same or related Planktothrix genotypes. Taken together, our data suggest that, depending on environmental conditions, chytrid parasitism can impose distinct selection regimes on conspecific phytoplankton populations with similar genotype composition, causing these populations to behave and perhaps to evolve differently. PMID:26714010

  17. Nutrient and Phytoplankton Analysis of a Mediterranean Coastal Area

    NASA Astrophysics Data System (ADS)

    Sebastiá, M. T.; Rodilla, M.

    2013-01-01

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

  18. Hydrodynamics and light climate structure alongshore phytoplankton blooms in spring

    NASA Astrophysics Data System (ADS)

    Brandt, G.; Wirtz, K. W.

    2009-05-01

    Phytoplankton blooms are a recurring phenomenon that have significant impact on annual biogeochemistry and food-web dynamics in many aquatic ecosystems. The causes for their variability, which is high especially in coastal seas, remain poorly understood. We present an example for distinct differences in the spatio-temporal chlorophyll-a (CHL-a) distribution on an interannual scale, integrating high-frequency data from an autonomous measuring device (FerryBox), which operated on an alongshore route in the coastal North Sea. While in one year CHL-a was spatially homogeneous (2004), a bloom only developed in one part of the transect in the following spring period (2005). In this study, we use a one-dimensional Lagrangian particle tracking model, which operates along the mean current direction, combined with a NPZ-model to identify the mechanisms controlling interannual bloom variability on an alongshore transect. The model results clearly indicate that in 2004, the local light climate triggered phytoplankton growth, whereas in the following year, advective transport determined the spatial structure of the spring bloom. A pronounced eastward inflow event in 2005 imported a high CHL-a patch into the western half of the study area from the adjacent Southern Bight. It did, however, not last long enough to also spread the bloom into the eastern part, where high turbidity prevented local phytoplankton growth. The model identified two interacting mechanisms, light climate and hydrodynamics that control the alongshore dynamics. Especially the occurrence of a pronounced spring bloom despite unfavourable light conditions in 2005 underlines the need to carefully consider hydrodynamics to understand ecosystem functioning in coastal environments.

  19. Effects of ultraviolet-B radiation on marine phytoplankton

    SciTech Connect

    Behrenfeld, M.J.

    1993-01-01

    Losses in the ozone layer increase ultraviolet B radiation at the earth's surface. Effects of UVBR on phytoplankton carbon fixation were determined from open ocean exposure studies conducted off the coast of Washington state. Photoinhibition of carbon fixation was a linear function of cumulative UVBR dose weighted by an exponential action spectrum. Comparison of the dose-response for UVBR inhibition of carbon uptake with results of earlier research indicates that a common, short-term photoinhibition response to UVBR may occur. Short-term photoinhibition was also measured for nitrogen uptake by natural plankton assemblages from the North Pacific. Ammonium uptake was inhibited by UVBR exposure to a greater extent than nitrate uptake. The action spectrum for ammonium uptake inhibition had a lower slope and greater relative contribution from wavelengths >320 nm to total biologically effective dose than the action spectrum for total UVR (290-347 nm) inhibition of carbon fixation. Inhibition of ammonium uptake was a linear function of biologically effective UVR dose. Comparison between dose-responses and action spectra for ammonium and carbon uptake suggest deeper water-column penetration of UVR effects on ammonium uptake than carbon uptake. Influence of nutritional status on the photoinhibitory effects of UVBR on phytoplankton growth rates and biomass were investigated using monocultures of the marine diatom Phaeodactylum tricornutum. Specific growth rates and biomass were inhibited from 2% to 16% by UVBR during nutrient-replete growth. However, no effect of UVBR was detectable when inhibition of growth rate and biomass by nutrient limitation exceeded the potential for inhibition by UVBR. Results suggest that phytoplankton in nutrient-rich areas of the ocean may be most susceptible to UVBR inhibition of growth and biomass, while these parameters may not be appropriate for measuring UVBR stress in regions of nutrient limitation.

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

    NASA Astrophysics Data System (ADS)

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

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

  1. Variability of chromophytic phytoplankton in the North Pacific Subtropical Gyre

    NASA Astrophysics Data System (ADS)

    Li, Binglin; Karl, David M.; Letelier, Ricardo M.; Bidigare, Robert R.; Church, Matthew J.

    2013-09-01

    Eukaryotic phytoplankton play important roles in regulating productivity and material export in oligotrophic ocean ecosystems. In this study, we examined the vertical and temporal variability in planktonic Chromalveolate (hereafter chromophyte) assemblages over a 2-year period (2007-2009) at Station ALOHA (22°45'N, 158°W) in the North Pacific Subtropical Gyre (NPSG). Polymerase chain reaction (PCR) amplification, cloning, and sequencing of form ID rbcL genes from samples collected at nearly monthly intervals provided information on the diversity, abundances, and variability associated with chromophytic phytoplankton. Despite persistently oligotrophic conditions, the euphotic zone of this habitat supported a phylogenetically diverse assemblage of chromophytic algae, including representatives of various genera of diatoms, pelagophytes, prymnesiophytes, and dinoflagellates. Quantitative PCR (qPCR) amplification of diatom, prymnesiophyte, and pelagophyte rbcL phylotypes revealed that the population structure of these assemblages was highly variable in time, with gene abundances often varying more than an order of magnitude between successive months. Diatom rbcL genes were typically the most abundant in both the upper and lower regions of the euphotic zone, while rbcL gene abundances of the prymnesiophytes and pelagophytes were significantly greater (One-way ANOVA, P<0.05) in the lower regions of the euphotic zone (75-125 m) than in the upper euphotic zone (5-45 m). Similarly, we observed elevated concentrations of 19-hexanoxyfucoxanthin and 19-butanoxyfucoxanin (diagnostic pigments of prymnesiophytes and pelagophytes, respectively) in the lower euphotic zone, while concentrations of fucoxanthin (a diagnostic diatom pigment) demonstrated less vertical structure. Analyses of samples collected using sediment traps deployed at 150 m revealed that members of diatoms, prymnesiophytes, and pelagophytes all contributed to material export out of the upper ocean. None of the

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

    USGS Publications Warehouse

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

    1992-01-01

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

  3. Three color laser fluorometer for studies of phytoplankton fluorescence

    NASA Technical Reports Server (NTRS)

    Phinney, David A.; Yentsch, C. S.; Rohrer, J.

    1988-01-01

    A three-color laser fluorometer has been developed for field work operations. Using two tunable dye lasers (excitation wavelengths at 440 nm and 530 nm), broadband wavelength optical filters were selected to obtain maximum fluorescence sensitivity at wavelengths greater than 675 nm (chlorophyll) and 575 + or - 15 nm (phycoerythrin). The laser fluorometer permits the measurement of phytoplankton pigments under static or flowing conditions and more closely resembles the time scales (ns) and energy levels (mW) of other laser-induced fluorescence instruments.

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

    PubMed

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

    1984-09-14

    Production in the western Bering Strait is estimated at 324 grams of carbon per square meter per year over 2.12x 10(4) square kilometers. An ice-reduced growing season makes this large amount of primary production unexpected, but it is consistent with the area's large upper trophic level stocks. The productivity is fueled by a cross-shelf flow of nutrient-rich water from the Bering Sea continental slope. This phytoplankton production system from June through September is analogous to a laboratory continuous culture. PMID:17782420

  5. Experimental evidence of site specific preferential processing of either ice algae or phytoplankton by benthic macroinfauna in Lancaster Sound and North Water Polynyas, Canada

    NASA Astrophysics Data System (ADS)

    Mäkelä, Anni; Witte, Ursula; Archambault, Philippe

    2016-04-01

    Rapid warming is dramatically reducing the extent and thickness of summer sea ice of the Arctic Ocean, changing both the quantity and type of marine primary production as the longer open water period favours phytoplankton growth and reduces ice algal production. The benthic ecosystem is dependent on this sinking organic matter for source of energy, and ice algae is thought to be a superior quality food source due to higher essential fatty acid content. The resilience of the benthos to changing quality and quantity of food was investigated through sediment incubation experiments in the summer 2013 in two highly productive Arctic polynyas in the North Water and Lancaster Sound, Canada. The pathways of organic matter processing and contribution of different organisms to these processes was assessed through 13C and 15N isotope assimilation into macroinfaunal tissues. In North Water Polynya, the total and biomass specific uptake of ice algal derived C and N was higher than the uptake of phytoplankton, whereas an opposite trend was observed in Lancaster Sound. Polychaetes, especially individuals of families Sabellidae and Spionidae, unselectively ingested both algal types and were significant in the overall organic matter processing at both sites. Feeding preference was observed in crustaceans, which preferentially fed on ice algae at Lancaster Sound, but preferred phytoplankton in North Water Polynya. Bivalves also had a significant role in the organic matter processing overall, but only showed preferential feeding on phytoplankton at Lancaster Sound polynya. Overall the filter feeders and surface deposit feeders occupying lowest trophic levels were responsible for majority of the processing of both algal types. The results provide direct evidence of preferential resource utilisation by benthic macrofauna and highlight spatial differences in the processes. This helps to predict future patterns of nutrient cycling in Arctic sediments, with implications to benthic

  6. AUV Measured Variability in Phytoplankton Fluorescence within the ETM of the Columbia River during Summer 2013

    NASA Astrophysics Data System (ADS)

    McNeil, C. L.; Shcherbina, A.; Litchendorf, T. M.; Sanford, T. B.; Martin, D.; Baptista, A. M.; Lopez, J.; Crump, B. C.; Peterson, T. D.; Prahl, F. G.; Cravo, A.

    2014-12-01

    We present highly resolved observations of fluorescence and optical backscatter taken in the estuarine turbidity maxima (ETM) of the North Channel of the Columbia River estuary (USA) during summer 2013. Measurements were made using two REMUS-100 autonomous underwater vehicles (AUVs) equipped with ECO Puck triplets. Concentrations of three phytoplankton pigments were measured by fluorescence emission at wavelengths of 695 nm for chlorophyll, 570 nm for phycoerythrin, and 680 nm for phycocyanin. We use phycocyanin to indicate the presence of freshwater phytoplankton. Optical backscatter at wavelengths of 700 nm and 880 nm are used to characterize turbidity. During flood tide, high phycocyanin concentrations were associated with a strong ETM event which had relatively low salinity waters of approximately 6 psu. These data indicate that this low salinity ETM event contained large concentrations of freshwater phytoplankton. Since freshwater phytoplankton are known to lyse in saltwater, the brackish ETM event may have formed by the accumulation of lysed freshwater phytoplankton that settled out from the river as it mixed in the lower estuary. As the flood tide proceeded, it brought high concentrations of marine phytoplankton into the north channel at mid-depth as indicated by high chlorophyll levels with significantly lower phycoerythrin concentrations in high salinity waters of approximately 30 psu. The data set highlights the potential for large variability in phytoplankton species composition and concentrations within the ETM depending on mixing rates and phytoplankton bloom dynamics. Visualization of the 4-D data is aided by generating interpolated data movies.

  7. NUTRIENT LIMITATION OF PHYTOPLANKTON GROWTH AND PHYSIOLOGY IN A SUBTROPICAL ESTUARY (PENSACOLA BAY, FL)

    EPA Science Inventory

    Phytoplankton nutrient limitation was studied in a sub-estuary of lower Pensacola Bay using several techniques. Results for <5 um and . 5 um phytoplankton were similar. Nutrient-addition bioassays indicated year-round nutrient limitation, in contrast to seasonal patterns often ...

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

    EPA Science Inventory

    Murrell, Michael C. and Emile M. Lores. 2004. Phytoplankton and Zooplankton Seasonal Dynamics in a Subtropical Estuary: Importance of Cyanobacteria. J. Plankton Res. 26(3):371-382. (ERL,GB 1190).

    A seasonal study of phytoplankton and zooplankton was conducted from 1999-20...

  9. The method of multispectral image processing of phytoplankton processing for environmental control of water pollution

    NASA Astrophysics Data System (ADS)

    Petruk, Vasil; Kvaternyuk, Sergii; Yasynska, Victoria; Kozachuk, Anastasia; Kotyra, Andrzej; Romaniuk, Ryszard S.; Askarova, Nursanat

    2015-12-01

    The paper presents improvement of the method of environmental monitoring of water bodies based on bioindication by phytoplankton, which identify phytoplankton particles carried out on the basis of comparison array multispectral images using Bayesian classifier of solving function based on Mahalanobis distance. It allows to evaluate objectively complex anthropogenic and technological impacts on aquatic ecosystems.

  10. Controls on temporal patterns in phytoplankton community structure in the Santa Barbara Channel, California

    NASA Astrophysics Data System (ADS)

    Anderson, Clarissa R.; Siegel, David A.; Brzezinski, Mark A.; Guillocheau, Nathalie

    2008-04-01

    Characterizing phytoplankton succession in the context of physical and chemical processes is important for understanding the mechanisms driving phytoplankton species composition and succession. An understanding of these processes ultimately influences the ability to predict the contribution of phytoplankton to carbon cycling, the initiation and persistence of harmful algal blooms, and the ability to use satellites for the remote sensing of specific phytoplankton taxa important for biogeochemistry. A statistical analysis of 5 years (1998-2003) of phytoplankton pigment concentrations from the Santa Barbara Channel using empirical orthogonal functions reveals four dominant modes of variability that explain 80% of the variance in the pigment data set. The annual cycle is characterized by a switching from a mixed-phytoplankton assemblage mode to modes dominated by either diatoms, dinoflagellates, or a combination of nano- and pico-phytoplankton. The dominant two modes correspond to a prebloom condition that precedes upwelling conditions, with all identified phytoplankton groups present in low abundance and a diatom-dominated upwelling state that develops following spring upwelling. In 2001, the EOF analysis indicated a transition toward more intense diatom blooms in spring and summer and fewer, large dinoflagellate blooms. This trend was corroborated by analyses of diagnostic pigments and CHEMTAX analysis and may be linked to an increase in local upwelling intensity between 2001 and 2003. Both spring diatom blooms occurring after 2001 were dominated by toxic Pseudo-nitzschia species and led to significant marine mammal deaths in the channel in 2003.

  11. Annual and interannual variations of phytoplankton pigment concentration and upwelling along the Pacific equator

    NASA Technical Reports Server (NTRS)

    Halpern, David; Feldman, Gene C.

    1994-01-01

    The following variables along the Pacific equator from 145 deg E to 95 deg W were employed: surface layer phytoplankton pigment concentrations derived from Nimbus 7 coastal zone color scanner (CZCS) measurements of ocean color radiances; vertical velocities simulated at the 90-m bottom of the euphotic layer from a wind-driven ocean general circulation model; and nitrate concentrations estimated from model-simulated temperature. The upward flux of nitrate into the euphotic layer was calculated from the simulated vertical motion and nitrate concentration. The CZCS-derived phytoplankton pigment concentration was uniform from 175 deg to 95 deg W. Longitudinal profiles of upwelling, phytoplankton biomass, and 90-m nitrate flux were of different shapes. The small annual cycles of the phytoplankton pigment and nitrate flux were in phase: increased phytoplankton biomass was associated with increased upward nitrate flux, but the phase was not consistent with the annual cycles of the easterly wind or of the upwelling intensity. Variation of phytoplankton pigment concentration was greater during El Nino than during the annual cycle. The substantially reduced phytoplankton pigment concentration observed during El Nino was associated with smaller upward nitrate flux. Phytoplankton biomass during non-El Nino conditions was not related to nitrate flux into the euphotic layer.

  12. EFFECTS OF NUTRIENT ENRICHMENT, LIGHT INTENSITY AND TEMPERATURE ON GROWTH OF PHYTOPLANKTON FROM LAKE HURON

    EPA Science Inventory

    This report contains a seasonal study on effects of nutrient enrichment, light and temperature on the growth of natural phytoplankton and three species of cultured diatoms. Natural phytoplankton assemblages collected monthly from April to December 1975, in southern Lake Huron wer...

  13. Shallow water processes govern system-wide phytoplankton bloom dynamics: A field study

    USGS Publications Warehouse

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

    2008-01-01

    Prior studies of the phytoplankton dynamics in South San Francisco Bay, California, USA have hypothesized that bivalve filter-feeders are responsible for the limited phytoplankton blooms in the system. This study was designed to examine the effects of benthic grazing and light attenuation on this shallow, turbid, and nutrient replete system. We found that grazing by shallow water bivalves was important in determining phytoplankton bloom occurrence throughout the system and that above a shallow water bivalve grazing threshold, phytoplankton biomass did not exceed bloom levels. Wind speed, used as a proxy for light attenuation in the shallow water, was similarly important in determining bloom development in the shallow water. Environmental conditions and benthic grazing in the deep water channel had a less discernible effect on system-wide phytoplankton blooms although persistent water column stratification did increase bloom magnitude. The shallow water bivalves, believed to be preyed upon by birds and fish that migrate through the system in fall and winter, disappear each year prior to the spring phytoplankton bloom. Because growth of the phytoplankton depends so strongly on shallow water processes, any change in the shallow-water benthic filter-feeders or their predators has great potential to change the phytoplankton bloom dynamics in this system. ?? 2007 Elsevier B.V. All rights reserved.

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

    PubMed

    Needham, David M; Fuhrman, Jed A

    2016-01-01

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

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

    EPA Science Inventory

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

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

    EPA Science Inventory

    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 ...

  17. Combatting cyanobacteria with hydrogen peroxide: a laboratory study on the consequences for phytoplankton community and diversity

    PubMed Central

    Weenink, Erik F. J.; Luimstra, Veerle M.; Schuurmans, Jasper M.; Van Herk, Maria J.; Visser, Petra M.; Matthijs, Hans C. P.

    2015-01-01

    Experiments with different phytoplankton densities in lake samples showed that a high biomass increases the rate of hydrogen peroxide (HP) degradation and decreases the effectiveness of HP in the selective suppression of dominant cyanobacteria. However, selective application of HP requires usage of low doses only, accordingly this defines the limits for use in lake mitigation. To acquire insight into the impact of HP on other phytoplankton species, we have followed the succession of three phytoplankton groups in lake samples that were treated with different concentrations of HP using a taxa-specific fluorescence emission test. This fast assay reports relatively well on coarse changes in the phytoplankton community; the measured data and the counts from microscopical analysis of the phytoplankton matched quite well. The test was used to pursue HP application in a Planktothrix agardhii-dominated lake sample and displayed a promising shift in the phytoplankton community in only a few weeks. From a low-diversity community, a change to a status with a significantly higher diversity and increased abundance of eukaryotic phytoplankton species was established. Experiments in which treated samples were re-inoculated with original P. agardhii-rich lake water demonstrated prolonged suppression of cyanobacteria, and displayed a remarkable stability of the newly developed post-HP treatment state of the phytoplankton community. PMID:26257710

  18. Phylogenetic Diversity and Specificity of Bacteria Closely Associated with Alexandrium spp. and Other Phytoplankton

    PubMed Central

    Jasti, Suresh; Sieracki, Michael E.; Poulton, Nicole J.; Giewat, Michael W.; Rooney-Varga, Juliette N.

    2005-01-01

    While several studies have suggested that bacterium-phytoplankton interactions have the potential to dramatically influence harmful algal bloom dynamics, little is known about how bacteria and phytoplankton communities interact at the species composition level. The objective of the current study was to determine whether there are specific associations between diverse phytoplankton and the bacteria that co-occur with them. We determined the phylogenetic diversity of bacterial assemblages associated with 10 Alexandrium strains and representatives of the major taxonomic groups of phytoplankton in the Gulf of Maine. For this analysis we chose xenic phytoplankton cultures that (i) represented a broad taxonomic range, (ii) represented a broad geographic range for Alexandrium spp. isolates, (iii) grew under similar cultivation conditions, (iv) had a minimal length of time since the original isolation, and (v) had been isolated from a vegetative phytoplankton cell. 16S rRNA gene fragments of most Bacteria were amplified from DNA extracted from cultures and were analyzed by denaturing gradient gel electrophoresis and sequencing. A greater number of bacterial species were shared by different Alexandrium cultures, regardless of the geographic origin, than by Alexandrium species and nontoxic phytoplankton from the Gulf of Maine. In particular, members of the Roseobacter clade showed a higher degree of association with Alexandrium than with other bacterial groups, and many sequences matched sequences reported to be associated with other toxic dinoflagellates. These results provide evidence for specificity in bacterium-phytoplankton associations. PMID:16000752

  19. Phytoplankton Pigment Degradation Patterns in the Oxic and Hypoxic Regions of a Lake Water-Column

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Degradation of senescent phytoplankton occurs as cells sink through the water-column. Once below the photic zone or buried in the sediments, pigment degradation products may be used in paleolimnological studies to elucidate past phytoplankton community composition. Interpretation of the sediment pig...

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

    SciTech Connect

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

    1995-09-01

    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.

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

    EPA Science Inventory

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

  2. Freezing of living cells: mechanisms and implications

    SciTech Connect

    Mazur, P.

    1984-01-01

    Cells can endure storage at low temperatures such as -196/sup 0/C for centuries. The challenge is to determine how they can survive both the cooling to such temperatures and the subsequent return to physiological conditions. A major factor is whether they freeze intracellularly. They do so if cooling is too rapid, because with rapid cooling insufficient cell water is removed osmotically to eliminate supercooling. Equations have been developed that describe the kinetics of this water loss and permit one to predict the likelihood of intracellular freezing as a function of cooling rate. Such predictions agree well with observations. Although the avoidance of intracellular freezing is usually necessary for survival, it is not sufficient. Slow freezing itself can be injurious. As ice forms outside the cell, the residual unfrozen medium forms channels of decreasing size and increasing solute concentration. The cells lie in the channels and shrink in osmotic response to the rising solute concentration. Prior theories have ascribed slow freezing injury to the concentration of solutes or the cell shrinkage. Recent experiments, however, indicate that the damage is due more to the decrease in the size of the unfrozen channels. This new view of the mechanism of slow freezing injury ought to facilitate the development of procedures for the preservation of complex assemblages of cells of biological, medical, and agricultural significance. 126 references, 18 figures, 2 tables.

  3. Diversity of phytoplanktons in a waste stabilization pond at Shimoga Town, Karnataka State, India.

    PubMed

    Shanthala, M; Hosmani, Shankar P; Hosetti, Basaling B

    2009-04-01

    To understand the diversity of phytoplanktons in waste stabilization pond effluents the hitherto study is undertaken. Species diversity indices of Shannon-Wiener and Simpson were applied to phytoplanktons. The diversity indices are of mathematical function to explain the abundance of each species. The total numbers of algae identified were 71 species belonging to Cyanophyceae, Chlorophyceae, Euglenophyceae, Bacillariophyceace and Desmidaceae. Chlorella and Scenedesmus were the dominant forms among the algal genera throughout the study period. Phytoplanktons play a vital role in improving the water quality of wastewater in waste stabilization ponds. Diversity indices provide important information about rarity and commonness of species in a community. The diversity indices of all the species explained the water was moderately polluted with less diversity level and highest possible equal number of different species of phytoplanktons. Greater impact of pollution leads to the lesser diversity of phytoplanktons. PMID:18523855

  4. Insights into eukaryotic phytoplankton and CO2 uptake in the marine biosphere

    NASA Astrophysics Data System (ADS)

    Worden, A. Z.

    2014-12-01

    Approximately half of global photosynthetic fixation of CO2 occurs in the marine biosphere. Development of more predictive mechanistic carbon cycle models is currently limited by the lack of understanding of physiological growth controls and quantitative information on the forces of mortality that act on the phytoplankton responsible for this CO2 uptake. A complication for research in this area is the fact that phytoplankton are exceptionally diverse. Primary productivity is not only partitioned between cyanobacterial and eukaryotic phytoplankton, but groups within the latter also have very different evolutionary histories and only some are represented in culture. Here, we will explore the advances and challenges in studying eukaryotic phytoplankton and factors that limit their growth in nature. Specifically, we will discuss ecosystems biology approaches that involve iteration between the lab and field and are proving most successful for gaining insight to environmental parameters that structure phytoplankton communities and growth.

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

    PubMed

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

    2014-04-15

    The effects of a thermal discharge from a coastal power plant on phytoplankton were determined in Zhanjiang Bay. Monthly cruises were undertaken at four tide times during April-October 2011. There were significant differences for dominant species among seven sampling months and four sampling tides. Species diversity (H') and Evenness showed a distinct increasing gradient from the heated water source to the control zone and fluctuated during four tides with no visible patterns. Species richness, cell count and Chl a at mixed and control zones were significantly higher than heated zones, and showed tidal changes with no obvious patterns. The threshold temperature of phytoplankton species can be regarded as that of phytoplankton community at ebb slack. The average threshold temperature over phytoplankton species, cell count and Chl a, and the threshold temperature of cell count can be regarded as that of phytoplankton community at flood slack during spring and neap respectively. PMID:24635985

  6. Interannual and cyclone-driven variability in phytoplankton communities of a tropical coastal lagoon.

    PubMed

    Srichandan, Suchismita; Kim, Ji Yoon; Kumar, Abhishek; Mishra, Deepak R; Bhadury, Punyasloke; Muduli, Pradipta R; Pattnaik, Ajit K; Rastogi, Gurdeep

    2015-12-15

    One of the main challenges in phytoplankton ecology is to understand their variability at different spatiotemporal scales. We investigated the interannual and cyclone-derived variability in phytoplankton communities of Chilika, the largest tropical coastal lagoon in Asia and the underlying mechanisms in relation to environmental forcing. Between July 2012 and June 2013, Cyanophyta were most prolific in freshwater northern region of the lagoon. A category-5 very severe cyclonic storm (VSCS) Phailin struck the lagoon on 12th October 2013 and introduced additional variability into the hydrology and phytoplankton communities. Freshwater Cyanophyta further expanded their territory and occupied the northern as well as central region of the lagoon. Satellite remote sensing imagery revealed that the phytoplankton biomass did not change much due to high turbidity prevailing in the lagoon after Phailin. Modeling analysis of species-salinity relationship identified specific responses of phytoplankton taxa to the different salinity regime of lagoon. PMID:26611863

  7. High bacterivory by the smallest phytoplankton in the North Atlantic Ocean.

    PubMed

    Zubkov, Mikhail V; Tarran, Glen A

    2008-09-11

    Planktonic algae <5 m in size are major fixers of inorganic carbon in the ocean. They dominate phytoplankton biomass in post-bloom, stratified oceanic temperate waters. Traditionally, large and small algae are viewed as having a critical growth dependence on inorganic nutrients, which the latter can better acquire at lower ambient concentrations owing to their higher surface area to volume ratios. Nonetheless, recent phosphate tracer experiments in the oligotrophic ocean have suggested that small algae obtain inorganic phosphate indirectly, possibly through feeding on bacterioplankton. There have been numerous microscopy-based studies of algae feeding mixotrophically in the laboratory and field as well as mathematical modelling of the ecological importance of mixotrophy. However, because of methodological limitations there has not been a direct comparison of obligate heterotrophic and mixotrophic bacterivory. Here we present direct evidence that small algae carry out 40-95% of the bacterivory in the euphotic layer of the temperate North Atlantic Ocean in summer. A similar range of 37-70% was determined in the surface waters of the tropical North-East Atlantic Ocean, suggesting the global significance of mixotrophy. This finding reveals that even the smallest algae have less dependence on dissolved inorganic nutrients than previously thought, obtaining a quarter of their biomass from bacterivory. This has important implications for how we perceive nutrient acquisition and limitation of carbon-fixing protists as well as control of bacterioplankton in the ocean. PMID:18690208

  8. A 150-year record of phytoplankton community succession controlled by hydroclimatic variability in a tropical lake

    NASA Astrophysics Data System (ADS)

    Afrifa Yamoah, Kweku; Callac, Nolwenn; Fru, Ernest Chi; Wohlfarth, Barbara; Wiech, Alan; Chabangborn, Akkaneewut; Smittenberg, Rienk H.

    2016-07-01

    Climate and human-induced environmental change promote biological regime shifts between alternate stable states, with implications for ecosystem resilience, function, and services. While these effects have been shown for present-day ecosystems, the long-term response of microbial communities has not been investigated in detail. This study assessed the decadal variations in phytoplankton communities in a ca. 150 year long sedimentary archive of Lake Nong Thale Prong (NTP), southern Thailand using a combination of bulk geochemical analysis, quantitative polymerase chain reaction (qPCR) and lipid biomarkers techniques including compound-specific hydrogen isotope analysis as a proxy for precipitation. Relatively drier and by inference warmer conditions from ca. 1857 to 1916 Common Era (CE) coincided with a dominance of the green algae Botryococcus braunii, indicating lower nutrient levels in the oxic lake surface waters, possibly related to lake water stratification. A change to higher silica (Si) input around 1916 CE was linked to increased rainfall and concurs with an abrupt takeover by diatom blooms lasting for 50 years. These were increasingly outcompeted by cyanobacteria from the 1970s onwards, most likely because of increased levels of anthropogenic phosphate and a reduction in rainfall. Our results showcase that the multi-proxy approach applied here provides an efficient way to track centennial-scale limnological, geochemical and microbial change, as influenced by hydroclimatic and anthropogenic forcing.

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

    PubMed Central

    Raveh, Ofrat; David, Niv; Rilov, Gil; Rahav, Eyal

    2015-01-01

    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. PMID:26474399

  10. The decline and fate of an iron-induced subarctic phytoplankton bloom.

    PubMed

    Boyd, Philip W; Law, Cliff S; Wong, C S; Nojiri, Yukihiro; Tsuda, Atsushi; Levasseur, Maurice; Takeda, Shigenobu; Rivkin, Richard; Harrison, Paul J; Strzepek, Robert; Gower, Jim; McKay, Mike; Abraham, Edward; Arychuk, Mike; Barwell-Clarke, Janet; Crawford, William; Crawford, David; Hale, Michelle; Harada, Koh; Johnson, Keith; Kiyosawa, Hiroshi; Kudo, Isao; Marchetti, Adrian; Miller, William; Needoba, Joe; Nishioka, Jun; Ogawa, Hiroshi; Page, John; Robert, Marie; Saito, Hiroaki; Sastri, Akash; Sherry, Nelson; Soutar, Tim; Sutherland, Nes; Taira, Yosuke; Whitney, Frank; Wong, Shau-King Emmy; Yoshimura, Takeshi

    2004-04-01

    Iron supply has a key role in stimulating phytoplankton blooms in high-nitrate low-chlorophyll oceanic waters. However, the fate of the carbon fixed by these blooms, and how efficiently it is exported into the ocean's interior, remains largely unknown. Here we report on the decline and fate of an iron-stimulated diatom bloom in the Gulf of Alaska. The bloom terminated on day 18, following the depletion of iron and then silicic acid, after which mixed-layer particulate organic carbon (POC) concentrations declined over six days. Increased particulate silica export via sinking diatoms was recorded in sediment traps at depths between 50 and 125 m from day 21, yet increased POC export was not evident until day 24. Only a small proportion of the mixed-layer POC was intercepted by the traps, with more than half of the mixed-layer POC deficit attributable to bacterial remineralization and mesozooplankton grazing. The depletion of silicic acid and the inefficient transfer of iron-increased POC below the permanent thermocline have major implications both for the biogeochemical interpretation of times of greater iron supply in the geological past, and also for proposed geo-engineering schemes to increase oceanic carbon sequestration. PMID:15058302

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

    PubMed

    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

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

    PubMed Central

    Galloway, Aaron W. E.; Winder, Monika

    2015-01-01

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

  13. [Research on the 3D fluorescence spectra differentiation of phytoplankton by coiflet2 wavelet].

    PubMed

    Liu, Bao; Su, Rong-Guo; Song, Zhi-Jie; Zhang, Fang; Wang, Xiu-Lin

    2010-05-01

    In the present paper, the authors utilize the wavelet base function coiflet2 (coif2) to analyze the 3D fluorescence spectra of 37 phytoplankton species belonging to 30 genera of 7 divisions, and these phytoplankton species include common species frequently causing harmful algal blooms and most predominant algal species in the inshore area of China Sea. After the Rayleigh and Raman scattering peaks were removed by the Delaunay triangulation interpolation, the fluorescence spectra of those phytoplankton species were transformed with the coiflet2 wavelet, and the scale vectors and the wavelet vectors were candidate for the feature spectra. Based on the testing results by Bayesian analysis, the 3rd scale vectors were the best feature segments at the division level and picked out as the fluorescence division feature spectra of those phytoplankton species, and the group of the 3rd scale vectors, the 2nd and 3rd wavelet vectors were the best feature segments at the genus level and chosen as the fluorescent genus feature spectra of those phytoplankton species. The reference spectra of those phytoplankton species at the division level and that at the genus level were obtained from these feature spectra by cluster analysis, respectively. The reference spectra base for 37 phytoplankton species was composed of 107 reference spectra at the division level and 155 ones at the genus level. Based on this reference spectra base, a fluorometric discriminating method for phytoplankton populations was established by multiple linear regression resolved by the nonnegative least squares. For 1 776 samples of single phytoplankton species, a correct discriminating rate of 97.0% at genus level and 98.1% at division level can be obtained; The correct discriminating rates are more than 92.7% at the genus level and more than 94.8% at the division level for 384 mixed samples from two phytoplankton species. PMID:20672617

  14. Interaction and signalling between a cosmopolitan phytoplankton and associated bacteria

    NASA Astrophysics Data System (ADS)

    Amin, S. A.; Hmelo, L. R.; van Tol, H. M.; Durham, B. P.; Carlson, L. T.; Heal, K. R.; Morales, R. L.; Berthiaume, C. T.; Parker, M. S.; Djunaedi, B.; Ingalls, A. E.; Parsek, M. R.; Moran, M. A.; Armbrust, E. V.

    2015-06-01

    Interactions between primary producers and bacteria impact the physiology of both partners, alter the chemistry of their environment, and shape ecosystem diversity. In marine ecosystems, these interactions are difficult to study partly because the major photosynthetic organisms are microscopic, unicellular phytoplankton. Coastal phytoplankton communities are dominated by diatoms, which generate approximately 40% of marine primary production and form the base of many marine food webs. Diatoms co-occur with specific bacterial taxa, but the mechanisms of potential interactions are mostly unknown. Here we tease apart a bacterial consortium associated with a globally distributed diatom and find that a Sulfitobacter species promotes diatom cell division via secretion of the hormone indole-3-acetic acid, synthesized by the bacterium using both diatom-secreted and endogenous tryptophan. Indole-3-acetic acid and tryptophan serve as signalling molecules that are part of a complex exchange of nutrients, including diatom-excreted organosulfur molecules and bacterial-excreted ammonia. The potential prevalence of this mode of signalling in the oceans is corroborated by metabolite and metatranscriptome analyses that show widespread indole-3-acetic acid production by Sulfitobacter-related bacteria, particularly in coastal environments. Our study expands on the emerging recognition that marine microbial communities are part of tightly connected networks by providing evidence that these interactions are mediated through production and exchange of infochemicals.

  15. Phytoplankton community and hydrochemical characteristics of the Western Black Sea.

    PubMed

    Velikova, V; Cociasu, A; Popa, L; Boicenco, L; Petrova, D

    2005-01-01

    Since the early 1990s the persistent reports about the irreversibly degrading Black Sea have started to disappear. A large set of data, reflecting the temporal and spatial variability of microalgae and hydrochemical parameters in Western Black Sea waters (WBS), collected in 2001-2002 (EU 5th FP project "daNubs"), allows us to compare the present-day ecosystem functioning to previous ones and to certainly conclude on positive signs of relaxation. The years 2001 and 2002 were without ample, negative biological and hydrochemical events in the WBS. Nutrient general trend was a decreasing one since the late 1980s, and inorganic phosphorus and nitrogen concentrations were frequently below the method detection limits during summer autumn periods of 2001-2002. The shelf waters were properly oxygenated. The phytoplankton community was producing biomass in a decreasing tendency, especially obviously since 1995. Simultaneously, there was an increase in Si:P and Si:N molar ratios and concurrent increase in the diversity of mass algal species (mainly diatoms) but only a few of them generated exceptional blooms. Reduction of the ratios between phytoplankton and zooplankton biomasses became evident. The observed ecological status in 2001-2002 confirms that the Black Sea is no longer a reference point for progressive water quality deterioration. PMID:16114612

  16. Plastids of Marine Phytoplankton Produce Bioactive Pigments and Lipids

    PubMed Central

    Heydarizadeh, Parisa; Poirier, Isabelle; Loizeau, Damien; Ulmann, Lionel; Mimouni, Virginie; Schoefs, Benoît; Bertrand, Martine

    2013-01-01

    Phytoplankton is acknowledged to be a very diverse source of bioactive molecules. These compounds play physiological roles that allow cells to deal with changes of the environmental constrains. For example, the diversity of light harvesting pigments allows efficient photosynthesis at different depths in the seawater column. Identically, lipid composition of cell membranes can vary according to environmental factors. This, together with the heterogenous evolutionary origin of taxa, makes the chemical diversity of phytoplankton compounds much larger than in terrestrial plants. This contribution is dedicated to pigments and lipids synthesized within or from plastids/photosynthetic membranes. It starts with a short review of cyanobacteria and microalgae phylogeny. Then the bioactivity of pigments and lipids (anti-oxidant, anti-inflammatory, anti-mutagenic, anti-cancer, anti-obesity, anti-allergic activities, and cardio- neuro-, hepato- and photoprotective effects), alone or in combination, is detailed. To increase the cellular production of bioactive compounds, specific culture conditions may be applied (e.g., high light intensity, nitrogen starvation). Regardless of the progress made in blue biotechnologies, the production of bioactive compounds is still limited. However, some examples of large scale production are given, and perspectives are suggested in the final section. PMID:24022731

  17. Impact of ocean phytoplankton diversity on phosphate uptake.

    PubMed

    Lomas, Michael W; Bonachela, Juan A; Levin, Simon A; Martiny, Adam C

    2014-12-01

    We have a limited understanding of the consequences of variations in microbial biodiversity on ocean ecosystem functioning and global biogeochemical cycles. A core process is macronutrient uptake by microorganisms, as the uptake of nutrients controls ocean CO2 fixation rates in many regions. Here, we ask whether variations in ocean phytoplankton biodiversity lead to novel functional relationships between environmental variability and phosphate (Pi) uptake. We analyzed Pi uptake capabilities and cellular allocations among phytoplankton groups and the whole community throughout the extremely Pi-depleted western North Atlantic Ocean. Pi uptake capabilities of individual populations were well described by a classic uptake function but displayed adaptive differences in uptake capabilities that depend on cell size and nutrient availability. Using an eco-evolutionary model as well as observations of in situ uptake across the region, we confirmed that differences among populations lead to previously uncharacterized relationships between ambient Pi concentrations and uptake. Supported by novel theory, this work provides a robust empirical basis for describing and understanding assimilation of limiting nutrients in the oceans. Thus, it demonstrates that microbial biodiversity, beyond cell size, is important for understanding the global cycling of nutrients. PMID:25422472

  18. Impact of ocean phytoplankton diversity on phosphate uptake

    PubMed Central

    Lomas, Michael W.; Bonachela, Juan A.; Levin, Simon A.; Martiny, Adam C.

    2014-01-01

    We have a limited understanding of the consequences of variations in microbial biodiversity on ocean ecosystem functioning and global biogeochemical cycles. A core process is macronutrient uptake by microorganisms, as the uptake of nutrients controls ocean CO2 fixation rates in many regions. Here, we ask whether variations in ocean phytoplankton biodiversity lead to novel functional relationships between environmental variability and phosphate (Pi) uptake. We analyzed Pi uptake capabilities and cellular allocations among phytoplankton groups and the whole community throughout the extremely Pi-depleted western North Atlantic Ocean. Pi uptake capabilities of individual populations were well described by a classic uptake function but displayed adaptive differences in uptake capabilities that depend on cell size and nutrient availability. Using an eco-evolutionary model as well as observations of in situ uptake across the region, we confirmed that differences among populations lead to previously uncharacterized relationships between ambient Pi concentrations and uptake. Supported by novel theory, this work provides a robust empirical basis for describing and understanding assimilation of limiting nutrients in the oceans. Thus, it demonstrates that microbial biodiversity, beyond cell size, is important for understanding the global cycling of nutrients. PMID:25422472

  19. Paleolatitudinal Gradients in Marine Phytoplankton Composition and Cell Size

    NASA Astrophysics Data System (ADS)

    Henderiks, J.; Bordiga, M.; Bartol, M.; Šupraha, L.

    2014-12-01

    Coccolithophores, a prominent group of marine calcifying unicellular algae, are widely studied in context of current and past climate change. We know that marine phytoplankton are sensitive to climatic changes, but the complex interplay of several processes such as warming, changes in nutrient content, and ocean acidification, makes future scenarios difficult to predict. Some taxa may be more susceptible to environmental perturbations than others, as evidenced by significantly different species-specific sensitivities observed in laboratory experiments. However, short-term plastic responses may not translate into longer-term climatic adaptation, nor should we readily extrapolate the behavior of single strains in the laboratory to natural, multi-species assemblages and their interactions in the ocean. The extensive fossil record of coccolithophores (in the form of coccoliths) reveals high morphological and taxonomic diversity and allows reconstructing the cell size of individual taxonomic groups. In a suite of deep-sea drilling sites from the Atlantic Ocean, we document distinct latitudinal gradients in phytoplankton composition and cell size across major climate transitions of the late Eocene - earliest Oligocene, and the middle - late Miocene. With these data we test hypotheses of species migration, phenotypic evolution, as well as the rates of species extinction and speciation in relation to concurrent paleoenvironmental changes during the Cenozoic.

  20. In situ Measurements of Phytoplankton Fluorescence Using Low Cost Electronics

    PubMed Central

    Leeuw, Thomas; Boss, Emmanuel S.; Wright, Dana L.

    2013-01-01

    Chlorophyll a fluorometry has long been used as a method to study phytoplankton in the ocean. In situ fluorometry is used frequently in oceanography to provide depth-resolved estimates of phytoplankton biomass. However, the high price of commercially manufactured in situ fluorometers has made them unavailable to some individuals and institutions. Presented here is an investigation into building an in situ fluorometer using low cost electronics. The goal was to construct an easily reproducible in situ fluorometer from simple and widely available electronic components. The simplicity and modest cost of the sensor makes it valuable to students and professionals alike. Open source sharing of architecture and software will allow students to reconstruct and customize the sensor on a small budget. Research applications that require numerous in situ fluorometers or expendable fluorometers can also benefit from this study. The sensor costs US$150.00 and can be constructed with little to no previous experience. The sensor uses a blue LED to excite chlorophyll a and measures fluorescence using a silicon photodiode. The sensor is controlled by an Arduino microcontroller that also serves as a data logger. PMID:23783738

  1. Network of Interactions Between Ciliates and Phytoplankton During Spring.

    PubMed

    Posch, Thomas; Eugster, Bettina; Pomati, Francesco; Pernthaler, Jakob; Pitsch, Gianna; Eckert, Ester M

    2015-01-01

    The annually recurrent spring phytoplankton blooms in freshwater lakes initiate pronounced successions of planktonic ciliate species. Although there is considerable knowledge on the taxonomic diversity of these ciliates, their species-specific interactions with other microorganisms are still not well understood. Here we present the succession patterns of 20 morphotypes of ciliates during spring in Lake Zurich, Switzerland, and we relate their abundances to phytoplankton genera, flagellates, heterotrophic bacteria, and abiotic parameters. Interspecific relationships were analyzed by contemporaneous correlations and time-lagged co-occurrence and visualized as association networks. The contemporaneous network pointed to the pivotal role of distinct ciliate species (e.g., Balanion planctonicum, Rimostrombidium humile) as primary consumers of cryptomonads, revealed a clear overclustering of mixotrophic/omnivorous species, and highlighted the role of Halteria/Pelagohalteria as important bacterivores. By contrast, time-lagged statistical approaches (like local similarity analyses, LSA) proved to be inadequate for the evaluation of high-frequency sampling data. LSA led to a conspicuous inflation of significant associations, making it difficult to establish ecologically plausible interactions between ciliates and other microorganisms. Nevertheless, if adequate statistical procedures are selected, association networks can be powerful tools to formulate testable hypotheses about the autecology of only recently described ciliate species. PMID:26635757

  2. Macroecological patterns of phytoplankton in the northwestern North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Li, W. K. W.

    2002-09-01

    Many issues in biological oceanography are regional or global in scope; however, there are not many data sets of extensive areal coverage for marine plankton. In microbial ecology, a fruitful approach to large-scale questions is comparative analysis wherein statistical data patterns are sought from different ecosystems, frequently assembled from unrelated studies. A more recent approach termed macroecology characterizes phenomena emerging from large numbers of biological units by emphasizing the shapes and boundaries of statistical distributions, because these reflect the constraints on variation. Here, I use a set of flow cytometric measurements to provide macroecological perspectives on North Atlantic phytoplankton communities. Distinct trends of abundance in picophytoplankton and both small and large nanophytoplankton underlaid two patterns. First, total abundance of the three groups was related to assemblage mean-cell size according to the 3/4 power law of allometric scaling in biology. Second, cytometric diversity (an ataxonomic measure of assemblage entropy) was maximal at intermediate levels of water column stratification. Here, intermediate disturbance shapes diversity through an equitable distribution of cells in size classes, from which arises a high overall biomass. By subsuming local fluctuations, macroecology reveals meaningful patterns of phytoplankton at large scales.

  3. Network of Interactions Between Ciliates and Phytoplankton During Spring

    PubMed Central

    Posch, Thomas; Eugster, Bettina; Pomati, Francesco; Pernthaler, Jakob; Pitsch, Gianna; Eckert, Ester M.

    2015-01-01

    The annually recurrent spring phytoplankton blooms in freshwater lakes initiate pronounced successions of planktonic ciliate species. Although there is considerable knowledge on the taxonomic diversity of these ciliates, their species-specific interactions with other microorganisms are still not well understood. Here we present the succession patterns of 20 morphotypes of ciliates during spring in Lake Zurich, Switzerland, and we relate their abundances to phytoplankton genera, flagellates, heterotrophic bacteria, and abiotic parameters. Interspecific relationships were analyzed by contemporaneous correlations and time-lagged co-occurrence and visualized as association networks. The contemporaneous network pointed to the pivotal role of distinct ciliate species (e.g., Balanion planctonicum, Rimostrombidium humile) as primary consumers of cryptomonads, revealed a clear overclustering of mixotrophic/omnivorous species, and highlighted the role of Halteria/Pelagohalteria as important bacterivores. By contrast, time-lagged statistical approaches (like local similarity analyses, LSA) proved to be inadequate for the evaluation of high-frequency sampling data. LSA led to a conspicuous inflation of significant associations, making it difficult to establish ecologically plausible interactions between ciliates and other microorganisms. Nevertheless, if adequate statistical procedures are selected, association networks can be powerful tools to formulate testable hypotheses about the autecology of only recently described ciliate species. PMID:26635757

  4. Seasonal Phytoplankton Dynamics in the Eastern Tropical Atlantic

    NASA Technical Reports Server (NTRS)

    Monger, Bruce; McClain, Charles; Murtugudde, Ragu

    1997-01-01

    The coastal zone color scanner (CZCS) that operated aboard the Nimbus 7 satellite provided extensive coverage of phytoplankton pigment concentrations in the surface waters of the eastern tropical Atlantic (ETA) from March 1979 to February 1980 and coincided with four major research cruises to this region. Total primary production within the ETA (5 deg N-10 deg S, 25 deg W-10 deg E) was determined from CZCS pigment estimates and an empirical algorithm derived from concurrent in situ data taken along 4 deg W that relates near-surface chlorophyll concentration and integrated primary production. We estimated an average annual production for the ETA of 2.3 Gt C/yr with an associated 3.5-fold seasonal variation in the magnitude of this production. We describe the principal physical mechanisms controlling seasonal phytoplankton dynamics within the ETA and propose that in addition to seasonal change in the thermocline depth, one must also consider changes in the depth of the equatorial under current. An extensive validation effort indicates that the standard CZCS global products are a conservative estimate of pigment concentrations in ETA surface waters. Significant underestimates by the CZCS global products were observed in June and July which we attributed, in part, to aerosol correction errors and, more importantly, to errors caused by a significant reduction in the concentration of near-surface dissolved organic matter that resulted from strong equatorial upwelling.

  5. Cell-associated proteolytic enzymes from marine phytoplankton

    SciTech Connect

    Berges, J.A.; Falkowski, P.G.

    1996-08-01

    Despite their central importance in cell metabolism, little is known about proteases in marine phytoplankton. Caseinolytic and leucine aminopeptidase (LAP) activities was surveyed in log-phase cultures of the chlorophyte Dunaliella tertiolecta Butcher, the diatom Thalassiosira weissflogii Fryxell et Hasle, the chrysophyte Isochrysis galbana Parke, the coccolithophorid Emiliania huxleyi Hay et Mohler, and the cyanobacterium Synechococcus sp. LAP activity was very low at pH < 6 and peaked between pH 7.5 and 8.5 in all species, whereas caseinolytic activity in most species showed only minor peaks in the pH 4-5 range and broad maxima above pH 8. Acidic vacuolar proteases apparently represented only a small fraction of total protease activity. Attempts to classify protease using selective inhibitors were inconclusive. Caserinolytic activities were remarkably stable. Casein zymograms were used to identify >200-and <20-kDa proteases in homogenates of log-phase T. weissflogii; only the smaller protease was found in D. tertiolecta. Antibodies in the ATPase subunit (C) of the conserved, chloroplastic Clp protease from Pisum cross-reacted with proteins in Synechococcus, D. tertiolecta, and I. galbana, but no cross-reactions were found for any species with antibodies against the ClpP subunit from either E. coli or Nicotiana. Our results show that phytoplankton contain a diverse complement of proteases with novel characteristics. 46 refs., 6 figs., 1 tab.

  6. Phytoplankton photosynthetic characteristics from fluorescence induction assays of individual cells

    SciTech Connect

    Olson, R.J.; Chekalyuk, A.M.; Sosik, H.M.

    1996-09-01

    Saturating-flash fluorescence techniques, which can provide information about the physiological state of phytoplankton, at present measure bulk water samples and so provide {open_quotes}averaged{close_quotes} values for all the fluorescent particles present. In analyzing natural samples, however, more detailed information about the distribution of photosynthetic characteristics among different cell types and(or) individual cells is desirable. Therefore we developed two methods for applying a {open_quotes}pump-during-probe{close_quotes} technique on a cell-by-cell basis. We used either an epifluorescence microscope or a flow cytometer to make time-resolved measurements of the increase in chlorophyll fluorescence induced by a rectangular excitation pulse of 100-{mu}s duration. We used a biophysical model of fluorescence induction to obtain information about the quantum yield of photochemistry in photosystem 2 (PS2) and the functional absorption cross-section for PS2. For several species (including the smallest phytoplankton, Prochlorococcus, which are 0.7 {mu}m in diameter), the maximum quantum yield of photochemistry in PS2 obtained by averaging data from many individual cells agreed well with estimates derived from bulk measurements of DCMU enhancement of Chl fluorescence. 40 refs., 9 figs.

  7. Global relationship between phytoplankton diversity and productivity in the ocean.

    PubMed

    Vallina, S M; Follows, M J; Dutkiewicz, S; Montoya, J M; Cermeno, P; Loreau, M

    2014-01-01

    The shape of the productivity-diversity relationship (PDR) for marine phytoplankton has been suggested to be unimodal, that is, diversity peaking at intermediate levels of productivity. However, there are few observations and there has been little attempt to understand the mechanisms that would lead to such a shape for planktonic organisms. Here we use a marine ecosystem model together with the community assembly theory to explain the shape of the unimodal PDR we obtain at the global scale. The positive slope from low to intermediate productivity is due to grazer control with selective feeding, which leads to the predator-mediated coexistence of prey. The negative slope at high productivity is due to seasonal blooms of opportunist species that occur before they are regulated by grazers. The negative side is only unveiled when the temporal scale of the observation captures the transient dynamics, which are especially relevant at highly seasonal latitudes. Thus selective predation explains the positive side while transient competitive exclusion explains the negative side of the unimodal PDR curve. The phytoplankton community composition of the positive and negative sides is mostly dominated by slow-growing nutrient specialists and fast-growing nutrient opportunist species, respectively. PMID:24980772

  8. Effect of amino acids on the toxicity of heavy metals to phytoplankton

    SciTech Connect

    Kosakowska, A.; Falkowski, L.; Lewandowska, J.

    1988-04-01

    Sea water contains free amino acids in concentrations ranging from 20 to 100 ..mu..g dm/sup -3/. The most abundant representatives of this group of compounds in the surface water were found to be glycine, serine and ornithine. The amino acids are utilized in the phytoplankton cells as the source of nitrogen as well as carbon in the case of slow rate of photosynthesis. Heavy metals distribution in the sea water can be indispensable or delitorious for the organisms living in that environment depending on their concentration and speciation. The bioavailability as well as toxicity of the elements are strongly influenced by the organic matter dissolved in water. The effect of a number of organic compounds, including amino acids, on the toxicity of heavy metals was tested, but there were no reports elucidating compounds representing various types of structure. This paper deals with the effect of amino acids representing various structure groups on the toxicity of copper, cadmium and mercury against to Chlorella vulgaris and Anabeana variabilis.

  9. The Living Ocean.

    ERIC Educational Resources Information Center

    National Aeronautics and Space Administration, Washington, DC.

    This teaching guide contains information, activities, and discussion questions and answers about oceans for grades nine and ten. The information section covers the following topics: studying global ocean color from space, what can be seen from space, phytoplankton, carbon dioxide, and the greenhouse effect of the earth. (MKR)

  10. In situ study on photosynthetic characteristics of phytoplankton in the Yellow Sea and East China Sea in summer 2013

    NASA Astrophysics Data System (ADS)

    Li, Junlei; Sun, Xiaoxia; Zheng, Shan

    2016-08-01

    In situ studies on photosynthetic characteristics of phytoplankton were important for the analysis of changes in community structure and for the prediction and control of algal blooms, but such studies of phytoplankton in offshore China were few. In this study, the detailed distribution of photosynthetic characteristics of phytoplankton in the summer of 2013 in the Yellow Sea and East China Sea was measured using Phyto-PAM (Pulse Amplitude Modulation). The phytoplankton community structure and the environmental parameters were also investigated to estimate the relationship between the distribution of the photochemical competence of phytoplankton and ecological factors. The total average Fv/Fm (the potential maximum quantum yield) value of phytoplankton in the Yellow Sea and East China Sea in summer 2013 was less than 0.5, reflecting that the photosynthetic activity of phytoplankton was relatively low. Fv/Fm of phytoplankton in summer was significantly positively associated with nitrate content (NO2-), which reflects relationship between metabolism and photosynthesis of phytoplankton: accompanied by NO2- metabolism, photosynthesis and photosynthetic capacity may be enhanced simultaneously, so the Fv/Fm value would increase with the NO2- released by phytoplankton. Through the in situ study on photosynthetic characteristics of phytoplankton in the Yellow Sea and East China Sea, we come to the conclusion that photosynthetic characteristics and activity of phytoplankton are influenced by its biological characteristics and surrounding ecological factors, such as irradiance, nutrients and phytoplankton community. Meanwhile, the thermally stratified structure and the movement of water masses, such as the Yangtze River diluted water, the Yellow Sea cold water mass and other different water system, also have an important impact on phytoplankton photosynthetic activity and characteristics. Greater understanding of the detailed photosynthetic characteristics of phytoplankton

  11. Remote estimation of phytoplankton size fractions using the spectral shape of light absorption.

    PubMed

    Wang, Shengqiang; Ishizaka, Joji; Hirawake, Toru; Watanabe, Yuji; Zhu, Yuanli; Hayashi, Masataka; Yoo, Sinjae

    2015-04-20

    Phytoplankton size structure plays an important role in ocean biogeochemical processes. The light absorption spectra of phytoplankton provide a great potential for retrieving phytoplankton size structure because of the strong dependence on the packaging effect caused by phytoplankton cell size and on different pigment compositions related to phytoplankton taxonomy. In this study, we investigated the variability in light absorption spectra of phytoplankton in relation to the size structure. Based on this, a new approach was proposed for estimating phytoplankton size fractions. Our approach use the spectral shape of the normalized phytoplankton absorption coefficient (a(ph)(λ)) through principal component analysis (PCA). Values of a(ph)(λ) were normalized to remove biomass effects, and PCA was conducted to separate the spectral variance of normalized a(ph)(λ) into uncorrelated principal components (PCs). Spectral variations captured by the first four PC modes were used to build relationships with phytoplankton size fractions. The results showed that PCA had powerful ability to capture spectral variations in normalized a(ph)(λ), which were significantly related to phytoplankton size fractions. For both hyperspectral a(ph)(λ) and multiband a(ph)(λ), our approach is applicable. We evaluated our approach using wide in situ data collected from coastal waters and the global ocean, and the results demonstrated a good and robust performance in estimating phytoplankton size fractions in various regions. The model performance was further evaluated by a(ph)(λ) derived from in situ remote sensing reflectance (R(rs)(λ)) with a quasi-analytical algorithm. Using R(rs)(λ) only at six bands, accurate estimations of phytoplankton size fractions were obtained, with R(2) values of 0.85, 0.61, and 0.76, and root mean-square errors of 0.130, 0.126, and 0.112 for micro-, nano-, and picophytoplankton, respectively. Our approach provides practical basis for remote estimation of

  12. Seasonal variations in phytoplankton community structure in the Sanggou, Ailian, and Lidao Bays

    NASA Astrophysics Data System (ADS)

    Yuan, Mingli; Zhang, Cuixia; Jiang, Zengjie; Guo, Shujin; Sun, Jun

    2014-12-01

    The seasonal variations in phytoplankton community structure were investigated for the Sanggou Bay (SGB) and the adjacent Ailian Bay (ALB) and Lidao Bay (LDB) in Shandong Peninsula, eastern China. The species composition and cell abundance of phytoplankton in the bay waters in spring (April 2011), summer (August 2011), autumn (October 2011), and winter (January 2012) were examined using the Utermöhl method. A total of 80 taxa of phytoplankton that belong to 39 genera of 3 phyla were identified. These included 64 species of 30 genera in the Phylum Bacillariophyta, 13 species of 8 genera in the Phylum Dinophyta, and 3 species of 1 genus in the Phylum Chrysophyta. During the four seasons, the number of phytoplankton species (43) was the highest in spring, followed by summer and autumn (40), and the lowest number of phytoplankton species (35) was found in winter. Diatoms, especially Paralia sulcata (Ehrenberg) Cleve and Coscinodiscus oculus-iridis Ehrenberg, were predominant in the phytoplankton community throughout the study period, whereas the dominance of dinoflagellate appeared in summer only. The maximum cell abundance of phytoplankton was detected in summer (average 8.08 × 103 cells L-1) whereas their minimum abundance was found in autumn (average 2.60 × 103 cells L-1). The phytoplankton abundance was generally higher in the outer bay than in the inner bay in spring and autumn. In summer, the phytoplankton cells were mainly concentrated in the south of inner SGB, with peak abundance observed along the western coast. In winter, the distribution of phytoplankton cells showed 3 patches, with peak abundance along the western coast as well. On seasonal average, the Shannon-Wiener diversity indices of phytoplankton community ranged from 1.17 to 1.78 (autumn > summer > spring > winter), and the Pielou's evenness indices of phytoplankton ranged from 0.45 to 0.65 (autumn > spring > summer > winter). According to the results of canonical correspondence analysis

  13. β -Decay Half-Lives of 110 Neutron-Rich Nuclei across the N=82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process

    SciTech Connect

    Lorusso, G.; Nishimura, S.; Xu, Z. Y.; Jungclaus, A.; Shimizu, Y.; Simpson, G. S.; Söderström, P. -A.; Watanabe, H.; Browne, F.; Doornenbal, P.; Gey, G.; Jung, H. S.; Meyer, B.; Sumikama, T.; Taprogge, J.; Vajta, Zs.; Wu, J.; Baba, H.; Benzoni, G.; Chae, K. Y.; Crespi, F. C. L.; Fukuda, N.; Gernhäuser, R.; Inabe, N.; Isobe, T.; Kajino, T.; Kameda, D.; Kim, G. D.; Kim, Y. -K.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Lane, G. J.; Li, Z.; Montaner-Pizá, A.; Moschner, K.; Naqvi, F.; Niikura, M.; Nishibata, H.; Odahara, A.; Orlandi, R.; Patel, Z.; Podolyák, Zs.; Sakurai, H.; Schaffner, H.; Schury, P.; Shibagaki, S.; Steiger, K.; Suzuki, H.; Takeda, H.; Wendt, A.; Yagi, A.; Yoshinaga, K.

    2015-05-01

    The β -decay half-lives of 110 neutron-rich isotopes of the elements from Rb 37 to Sn 50 were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for r -process calculations and reinforce the notion that the second (A≈130 ) and the rare-earth-element (A≈160 ) abundance peaks may result from the freeze-out of an (n,γ)⇌(γ,n) equilibrium. In such an equilibrium, the new half-lives are important factors determining the abundance of rare-earth elements, and allow for a more reliable discussion of the r process universality. It is anticipated that universality may not extend to the elements Sn, Sb, I, and Cs, making the detection of these elements in metal-poor stars of the utmost importance to determine the exact conditions of individual r -process events.

  14. Changes in phytoplankton communities along nutrient gradients in Lake Taihu: evidence for nutrient reduction strategies

    NASA Astrophysics Data System (ADS)

    Ai, Ying; Bi, Yonghong; Hu, Zhengyu

    2015-03-01

    An annual investigation on phytoplankton communities was conducted to reveal the effects of nutrients on phytoplankton assemblages in Lake Taihu, East China. A total of 78 phytoplankton taxa were identified. Phytoplankton biomass was higher in the northern part of the lake than in the southern part. Cyanobacteria and Bacillariophyta alternated dominance in the northern area, where algal blooms often appear, and co-dominated in the southern area. In the northern part, the proportions of cyanobacteria and Bacillariophyta varied significantly in total biovolume, both along the phosphorus (P) gradient, and between total nitrogen levels (≤3 mg/L and >3 mg/L TN). The proportions of cyanobacteria and Bacillariophyta had no significant variations in total biovolume along P and N (nitrogen) gradients in the southern part. Correlation analysis and CCA results revealed that P was the key factor regulating phytoplankton community structure. Nitrogen was also important for the phytoplankton distribution pattern. It was concluded that nutrient structure was heterogeneous in space and shaped the distribution pattern of phytoplankton in the lake. Both exogenous P and internally sourced P release needs to be considered. N reduction should be considered simultaneously with P control to efficiently reduce eutrophication and algal blooms.

  15. Resource supply overrides temperature as a controlling factor of marine phytoplankton growth.

    PubMed

    Marañón, Emilio; Cermeño, Pedro; Huete-Ortega, María; López-Sandoval, Daffne C; Mouriño-Carballido, Beatriz; Rodríguez-Ramos, Tamara

    2014-01-01

    The universal temperature dependence of metabolic rates has been used to predict how ocean biology will respond to ocean warming. Determining the temperature sensitivity of phytoplankton metabolism and growth is of special importance because this group of organisms is responsible for nearly half of global primary production, sustains most marine food webs, and contributes to regulate the exchange of CO2 between the ocean and the atmosphere. Phytoplankton growth rates increase with temperature under optimal growth conditions in the laboratory, but it is unclear whether the same degree of temperature dependence exists in nature, where resources are often limiting. Here we use concurrent measurements of phytoplankton biomass and carbon fixation rates in polar, temperate and tropical regions to determine the role of temperature and resource supply in controlling the large-scale variability of in situ metabolic rates. We identify a biogeographic pattern in phytoplankton metabolic rates, which increase from the oligotrophic subtropical gyres to temperate regions and then coastal waters. Variability in phytoplankton growth is driven by changes in resource supply and appears to be independent of seawater temperature. The lack of temperature sensitivity of realized phytoplankton growth is consistent with the limited applicability of Arrhenius enzymatic kinetics when substrate concentrations are low. Our results suggest that, due to widespread resource limitation in the ocean, the direct effect of sea surface warming upon phytoplankton growth and productivity may be smaller than anticipated. PMID:24921945

  16. The Effect of ENSO on Phytoplankton Composition in the Pacific Ocean

    NASA Technical Reports Server (NTRS)

    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 (p less than 0.01) with the Multivariate El Nino Southern Oscillation Index (MEI). In the North Central Pacific, MEI and chlorophyll were significantly (p<0.01) correlated along with two of the phytoplankton groups (chlorophytes and coccolithophores). Ocean biology in the South Pacific was not significantly correlated with MEI. During La Ni a 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. [Yearly Changes of Phytoplankton Community in the Ecology-monitoring Area of Changli, Hebei in Summer].

    PubMed

    Liang, Xiao-lin; Yang, Yang; Wang, Yu-liang; Zhang, Yue-ming; Zhao, Zhi-nan; Han, Xiao-qing; Zhang, Jian-da; Gao, Wei-ming

    2015-04-01

    Based on the investigation of phytoplankton and water body nutrient concentration in the ecology-monitoring area of Changli in summer from 2005 to 2013, the phytoplankton community structure was analyzed. The result showed that in recent 9 years, 3 phyla including 23 families, 39 genera and 105 species of phytoplankton were identified, in which 85.7% were diatoms and 13.3% were dinoflagellate. Only one species was found belonging to golden algae. There was great difference in dominant species among different years. According to the value of dominance, there were Coscinodiscus radiatus, Coscinodiscus debilis, Rhizosolenia styliformis, Cerataulina bergoni, Coscinodiscus wailesii, Thalassiosira sp., Ceratium tripos, Chaetoceros lorenzianus, Skeletonema costatum. The cell abundance was decreased yearly. The Shannon-Wiener index of phytoplankton community ranged from 0.015 to 3.889, and the evenness index ranged from 0.009 to 1, which showed little yearly change. And phytoplankton species were unevenly distributed among the 19 sites, there were relatively low amount of dominant species, but the dominance was relatively high. Canonical Correspondence Analysis (CCA) results of the phytoplankton community and its environmental factors showed that the environmental factors influencing the change of phytoplankton community structure in summer included water temperature, nutrients (TP, TN and NO3(-) -N, NH4(+)-N) and salinity, and the structural change was the result of the interactions of different environmental factors. PMID:26164906

  18. Linking phytoplankton community composition to seasonal changes in f-ratio

    PubMed Central

    Ward, Bess B; Rees, Andrew P; Somerfield, Paul J; Joint, Ian

    2011-01-01

    Seasonal changes in nitrogen assimilation have been studied in the western English Channel by sampling at approximately weekly intervals for 12 months. Nitrate concentrations showed strong seasonal variations. Available nitrogen in the winter was dominated by nitrate but this was close to limit of detection from May to September, after the spring phytoplankton bloom. The 15N uptake experiments showed that nitrate was the nitrogen source for the spring phytoplankton bloom but regenerated nitrogen supported phytoplankton productivity throughout the summer. The average annual f-ratio was 0.35, which demonstrated the importance of ammonia regeneration in this dynamic temperate region. Nitrogen uptake rate measurements were related to the phytoplankton responsible by assessing the relative abundance of nitrate reductase (NR) genes and the expression of NR among eukaryotic phytoplankton. Strong signals were detected from NR sequences that are not associated with known phylotypes or cultures. NR sequences from the diatom Phaeodactylum tricornutum were highly represented in gene abundance and expression, and were significantly correlated with f-ratio. The results demonstrate that analysis of functional genes provides additional information, and may be able to give better indications of which phytoplankton species are responsible for the observed seasonal changes in f-ratio than microscopic phytoplankton identification. PMID:21544101

  19. Linking phytoplankton community composition to seasonal changes in f-ratio.

    PubMed

    Ward, Bess B; Rees, Andrew P; Somerfield, Paul J; Joint, Ian

    2011-11-01

    Seasonal changes in nitrogen assimilation have been studied in the western English Channel by sampling at approximately weekly intervals for 12 months. Nitrate concentrations showed strong seasonal variations. Available nitrogen in the winter was dominated by nitrate but this was close to limit of detection from May to September, after the spring phytoplankton bloom. The (15)N uptake experiments showed that nitrate was the nitrogen source for the spring phytoplankton bloom but regenerated nitrogen supported phytoplankton productivity throughout the summer. The average annual f-ratio was 0.35, which demonstrated the importance of ammonia regeneration in this dynamic temperate region. Nitrogen uptake rate measurements were related to the phytoplankton responsible by assessing the relative abundance of nitrate reductase (NR) genes and the expression of NR among eukaryotic phytoplankton. Strong signals were detected from NR sequences that are not associated with known phylotypes or cultures. NR sequences from the diatom Phaeodactylum tricornutum were highly represented in gene abundance and expression, and were significantly correlated with f-ratio. The results demonstrate that analysis of functional genes provides additional information, and may be able to give better indications of which phytoplankton species are responsible for the observed seasonal changes in f-ratio than microscopic phytoplankton identification. PMID:21544101

  20. Effects of Nutrients, Temperature and Their Interactions on Spring Phytoplankton Community Succession in Lake Taihu, China

    PubMed Central

    Deng, Jianming; Qin, Boqiang; Paerl, Hans W.; Zhang, Yunlin; Wu, Pan; Ma, Jianrong; Chen, Yuwei

    2014-01-01

    We examined the potential effects of environmental variables, and their interaction, on phytoplankton community succession in spring using long-term data from 1992 to 2012 in Lake Taihu, China. Laboratory experiments were additionally performed to test the sensitivity of the phytoplankton community to nutrient concentrations and temperature. A phytoplankton community structure analysis from 1992 to 2012 showed that Cryptomonas (Cryptophyta) was the dominant genus in spring during the early 1990s. Dominance then shifted to Ulothrix (Chlorophyta) in 1996 and 1997. However, Cryptomonas again dominated in 1999, 2000, and 2002, with Ulothrix regaining dominance from 2003 to 2006. The bloom-forming cyanobacterial genus Microcystis dominated in 1995, 2001 and 2007–2012. The results of ordinations indicated that the nutrient concentration (as indicated by the trophic state index) was the most important factor affecting phytoplankton community succession during the past two decades. In the laboratory experiments, shifts in dominance among phytoplankton taxa occurred in all nutrient addition treatments. Results of both long term monitoring and experiment indicated that nutrients exert a stronger control than water temperature on phytoplankton communities during spring. Interactive effect of nutrients and water temperature was the next principal factor. Overall, phytoplankton community composition was mediated by nutrients concentrations, but this effect was strongly enhanced by elevated water temperatures. PMID:25464517

  1. Nitrogen deposition and warming - effects on phytoplankton nutrient limitation in subarctic lakes.

    PubMed

    Bergström, Ann-Kristin; Faithfull, Carolyn; Karlsson, Daniel; Karlsson, Jan

    2013-08-01

    The aim of this study was to predict the combined effects of enhanced nitrogen (N) deposition and warming on phytoplankton development in high latitude and mountain lakes. Consequently, we assessed, in a series of enclosure experiments, how lake water nutrient stoichiometry and phytoplankton nutrient limitation varied over the growing season in 11 lakes situated along an altitudinal/climate gradient with low N-deposition (<1 kg N ha(-1)  yr(-1) ) in northern subarctic Sweden. Short-term bioassay experiments with N- and P-additions revealed that phytoplankton in high-alpine lakes were more prone to P-limitation, and with decreasing altitude became increasingly N- and NP-colimited. Nutrient limitation was additionally most obvious in midsummer. There was also a strong positive correlation between phytoplankton growth and water temperature in the bioassays. Although excess nutrients were available in spring and autumn, on these occasions growth was likely constrained by low water temperatures. These results imply that enhanced N-deposition over the Swedish mountain areas will, with the exception of high-alpine lakes, enhance biomass and drive phytoplankton from N- to P-limitation. However, if not accompanied by warming, N-input from deposition will stimulate limited phytoplankton growth due to low water temperatures during large parts of the growing season. Direct effects of warming, allowing increased metabolic rates and an extension of the growing season, seem equally crucial to synergistically enhance phytoplankton development in these lakes. PMID:23629960

  2. [Community structure characteristics of phytoplankton and related affecting factors in Hengshan Reservoir, Zhejiang, China].

    PubMed

    Yang, Liang-Jie; Yu, Peng-Fei; Zhu, Jun-Quan; Xu, Zhen; Lü, Guang-Han; Jin, Chun-Hua

    2014-02-01

    In order to reveal the community structure characteristics of phytoplankton and the relationships with environmental factors in Hengshan Reservoir, the phytoplankton species composition, abundance, biomass and 12 environmental factors at 4 sampling sites were analyzed from March 2011 to February 2012. A total of 246 phytoplankton species were identified, which belong to 78 genera and 7 phyla. The dominant species were Melosira varians, M. granulate, Cyclotella meneghiniana, Asterianella formosa, Synedra acus, Achnanthes exigua, Ankistrodesmus falcatus, Oscillatoria lacustris, Cryptomonas erosa, Chroomonas acuta, Phormidium tenue and Microcystis aeruginosa, etc. Seasonal variations of species were obvious. The annual abundance and biomass of the phytoplankton were 0.51 x 10(5)-14.22 x 10(5) ind x L(-1) and 0.07-1.27 mg x L(-1), respectively. The values of the Margelef index, Pielou index and Shannon index of the phytoplankton community were 1.10-3.33, 0.26-0.81 and 0.51-2.38, respectively. The phytoplankton community structure was of Bacillariophyta-Cryptophyta type in spring and winter, of Chlorophyta-Cyanophyta type in summer, and of Bacillariophyta type in autumn. Canonical correlation analysis (CCA) showed that temperature, transparency, chemical oxygen demand and pH had the closest relationships with the phytoplankton community structure in the reservoir. Water quality evaluation showed that Hengshan Reservoir was in a secondary pollution with a meso-trophic level. PMID:24830259

  3. Carbon budget of a marine phytoplankton-herbivore system with carbon-14 as a tracer

    SciTech Connect

    Copping, A.E.; Lorenzen, C.J.

    1980-09-01

    Adult female and stage V Calanus pacificus were fed /sup 14/C-labeled phytoplankton in the laboratory in the form of monospecific cultures and natural populations. A carbon budget was constructed by following the /sup 14/C activity and the specific activity, over 48 h, in the phytoplankton, copepod, dissolved organic, dissolved inorganic, and fecal carbon compartments. The average incorporation of carbon into the copepod's body was 45% of the phytoplankton carbon available. Of the phytoplankton carbon, 27% appeared as dissolved organic carbon, 24% as dissolved inorganic carbon, and 3 to 4% in the form of fecal pellets. All of the tracer was recovered at the end of the experiments. The specific activity of the phytoplankton compartment was constant throughout each experiment. The other compartments had initial specific activities of zero, or close to zero, and increased throughout the experiment. In most experiments, the copepod specific activity equalled that of the phytoplankton at the end of 48 h, while the dissolved organic carbon, dissolved inorganic carbon, and fecal specific activities remained well below that of the phytoplankton.

  4. Using photopigment biomarkers to quantify sub-lethal effects of petroleum pollution on natural phytoplankton assemblages

    SciTech Connect

    Swistak, J.; Pinckney, J.; Piehler, M.; Paerl, H.

    1995-12-31

    Although much work has been undertaken to determine the toxicity of petroleum pollutants to phytoplankton, most studies have used pure cultures to monitor growth of selected phytoplankton species. Fewer have considered the net effect on entire microalgal communities. Using high performance liquid chromatography (HPLC) to characterize diagnostic microalgal pigments, the authors were able to simultaneously assess sub-lethal pollutant effects on entire communities as well as on individual phytoplankton functional groups. Incubations of natural water samples with diesel fuel, an important contributor to coastal petroleum pollution, revealed significant changes in photopigments and relative abundance of taxonomic groups at sub-lethal concentrations. Differential rates of change of indicator pigment concentrations suggest a range of sensitivity among phytoplankton groups. In preliminary experiments, cyanobacteria exhibited the greatest overall tolerance to the diesel fuel concentrations tested, while cryptomonads displayed the most sensitivity. The authors are currently evaluating the responses of seasonal phytoplankton populations from 3 sites exposed to varied levels of petroleum pollution. HPLC will be used to characterize phytoplankton populations and to determine if the most abundant groups are also the most tolerant of diesel fuel. Preliminary experiments indicate that diesel fuel pollution may modify the structure and function of phytoplankton communities and subsequently alter the trophodynamics of impacted systems.

  5. Phytoplankton dynamics of the fresh, tidal Potomac River, Maryland, for the summers of 1979 to 1981

    USGS Publications Warehouse

    Cohen, Ronald R.H.

    1988-01-01

    The distribution and abundance of phytoplankton in the fresh, tidal Potomac River, Md., was different during 1979-81 from that observed in the 1960's and 1970's. Concentrations of phytoplankton in the 1960's and 1970's reached maximum attainable levels that were limited only by self-shading. A sag in phytoplankton abundance, apparent during the summers of 1980 and 1981 between Rosier Bluff and Marshall Hall, appears to have been caused by the Asiatic clam, Corbicula fluminea. Reduced abundance of phytoplankton throughout the entire fresh, tidal river during the summers of 1980 and 1981 may have been due to grazing by Corbicula, high discharge, and perhaps phosphorus limitation in late August at and downstream of Hallowing Point. Phytoplankton growth rates and chlorophyll-to-cell ratios were highest at Hatton Point and Marshall Hall (the sag reach). A model was constructed that predicted phytoplankton growth rates by varying only chlorophyll a concentration and light penetration. Nutrient concentrations were not required to make the model fit the data. Primary productivity was highest for the year during August 1980 and August 1981. Productivity-per-unit chlorophyll was highest at Hatton Point, where reduced concentrations of phytoplankton permitted the deepest light penetration in the fresh, tidal river.

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

    USGS Publications Warehouse

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

    2002-01-01

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

  7. Impact of contaminated-sediment resuspension on phytoplankton in the Biguglia lagoon (Corsica, Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Lafabrie, Céline; Garrido, Marie; Leboulanger, Christophe; Cecchi, Philippe; Grégori, Gérald; Pasqualini, Vanina; Pringault, Olivier

    2013-09-01

    In shallow human-impacted systems, sediment resuspension events can result in pulsed exposures of pelagic organisms to multiple contaminants. Here, we examined the impact of the resuspension of contaminated sediment on phytoplankton in the Biguglia lagoon (Corsica, Mediterranean Sea), by conducting an in situ microcosm experiment over a 96-h period. Natural phytoplankton was exposed to elutriates prepared from a contaminated-sediment resuspension simulating process, and its functional and structural responses were compared with those of non-exposed phytoplankton. The elutriates displayed moderate multiple contamination by trace metals and PAHs. Our results show that elutriate exposure induced both functional and structural phytoplankton changes. Elutriates strongly stimulated phytoplankton growth after 24 h of exposure. They also enhanced phytoplankton photosynthetic performance during the first hours of exposure (up to 48 h), before reducing it toward the end of the experiment. Elutriates were also found to slightly stimulate Bacillariophyceae and conversely to slightly inhibit Dinophyceae in the short term. Additionally, they were found to stimulate phycocyanin-rich picocyanobacteria in the short term (8-48 h) before inhibiting it in the longer term (72-96 h), and to inhibit eukaryotic nanophytoplankton in the short term (8-48 h) before stimulating it in the longer term (72-96 h). Sediment resuspensions are thus likely to have significant effects on the global dynamics and functions of phytoplankton in contaminated coastal environments.

  8. Living With Semantic Dementia

    PubMed Central

    Sage, Karen; Wilkinson, Ray; Keady, John

    2014-01-01

    Semantic dementia is a variant of frontotemporal dementia and is a recently recognized diagnostic condition. There has been some research quantitatively examining care partner stress and burden in frontotemporal dementia. There are, however, few studies exploring the subjective experiences of family members caring for those with frontotemporal dementia. Increased knowledge of such experiences would allow service providers to tailor intervention, support, and information better. We used a case study design, with thematic narrative analysis applied to interview data, to describe the experiences of a wife and son caring for a husband/father with semantic dementia. Using this approach, we identified four themes: (a) living with routines, (b) policing and protecting, (c) making connections, and (d) being adaptive and flexible. Each of these themes were shared and extended, with the importance of routines in everyday life highlighted. The implications for policy, practice, and research are discussed. PMID:24532121

  9. Estuarine Phytoplankton Monitoring to Meet Undergraduate and Faculty Research Objectives

    NASA Astrophysics Data System (ADS)

    Pride, C. J.; Wilson, J. J.; Butterbaugh, T.

    2004-12-01

    Phytoplankton monitoring is being used at Savannah State University to provide research experience for all upper-level marine science majors, to provide in-depth senior research projects, to engage lower-level students in marine science activities beyond the classroom, and to collect baseline data for faculty research proposals. The framework is built around a commitment to maintain a tidal creek monitoring site for larger phytoplankton (diatoms and dinoflagellates >20 microns) as part of the Southeast Phytoplankton Monitoring Network (SEPMN). Field supplies and on-going training are supported by SEPMN. Marine science majors monitor a series of Wilmington River estuary sites as part of a group research project in an upper-level course offered each spring. The group research assignment includes the writing of a full research report with citations from the primary literature and peer review of drafts. A few students are encouraged to pursue their senior research project in this field and maintain sampling over the remainder of the year. They have freedom to design their own project in the broader context of eutrophication, high frequency temporal variability, seasonality, drought/flood cycles, comparisons between estuaries of differing river discharge or extension of sampling offshore. Senior researchers help to train freshmen/sophomore field assistants to insure consistency in the monitoring from one year to the next. Student data from the Wilmington River estuary cover the greatest portion of an annual cycle. Diatoms far outnumbered dinoflagellates at all estuarine sampling locations under both winter and summer conditions. There is a seasonal transition in this estuary from dominance of Asterionella sp. in February to Chaetoceros sp. in June. Chaetoceros sp. were also dominant in the lower Savannah River estuary in June. Dominance of diatoms in these estuaries rather than dinoflagellates is a sign of a relatively healthy ecosystem. These diatoms, however, did

  10. ISS Live!

    NASA Technical Reports Server (NTRS)

    Price, Jennifer; Harris, Philip; Hochstetler, Bruce; Guerra, Mark; Mendez, Israel; Healy, Matthew; Khan, Ahmed

    2013-01-01

    International Space Station Live! (ISSLive!) is a Web application that uses a proprietary commercial technology called Lightstreamer to push data across the Internet using the standard http port (port 80). ISSLive! uses the push technology to display real-time telemetry and mission timeline data from the space station in any common Web browser or Internet- enabled mobile device. ISSLive! is designed to fill a unique niche in the education and outreach areas by providing access to real-time space station data without a physical presence in the mission control center. The technology conforms to Internet standards, supports the throughput needed for real-time space station data, and is flexible enough to work on a large number of Internet-enabled devices. ISSLive! consists of two custom components: (1) a series of data adapters that resides server-side in the mission control center at Johnson Space Center, and (2) a set of public html that renders the data pushed from the data adapters. A third component, the Lightstreamer server, is commercially available from a third party and acts as an intermediary between custom components (1) and (2). Lightstreamer also provides proprietary software libraries that are required to use the custom components. At the time of this reporting, this is the first usage of Web-based, push streaming technology in the aerospace industry.

  11. Effects of spatial and temporal variability of turbidity on phytoplankton blooms

    USGS Publications Warehouse

    May, Christine L.; Koseff, Jeffrey R.; Lucas, Lisa; Cloern, James E.; Schoellhamer, David H.

    2003-01-01

    A central challenge of coastal ecology is sorting out the interacting spatial and temporal components of environmental variability that combine to drive changes in phytoplankton biomass. For 2 decades, we have combined sustained observation and experimentation in South San Francisco Bay (SSFB) with numerical modeling analyses to search for general principles that define phytoplankton population responses to physical dynamics characteristic of shallow, nutrient-rich coastal waters having complex bathymetry and influenced by tides, wind and river flow. This study is the latest contribution where we investigate light-limited phytoplankton growth using a numerical model, by modeling turbidity as a function of suspended sediment concentrations (SSC). The goal was to explore the sensitivity of estuarine phytoplankton dynamics to spatial and temporal variations in turbidity, and to synthesize outcomes of simulation experiments into a new conceptual framework for defining the combinations of physical-biological forcings that promote or preclude development of phytoplankton blooms in coastal ecosystems. The 3 main conclusions of this study are: (1) The timing of the wind with semidiurnal tides and the spring-neap cycle can significantly enhance spring-neap variability in turbidity and phytoplankton biomass; (2) Fetch is a significant factor potentially affecting phytoplankton dynamics by enhancing and/or creating spatial variability in turbidity; and (3) It is possible to parameterize the combined effect of the processes influencing turbidity‹and thus affecting potential phytoplankton bloom development‹with 2 indices for vertical and horizontal clearing of the water column. Our conceptual framework is built around these 2 indices, providing a means to determine under what conditions a phytoplankton bloom can occur, and whether a potential bloom is only locally supported or system-wide in scale. This conceptual framework provides a tool for exploring the inherent light

  12. Recognition of key regions for restoration of phytoplankton communities in the Huai River basin, China

    NASA Astrophysics Data System (ADS)

    Zhao, Changsen; Liu, Changming; Xia, Jun; Zhang, Yongyong; Yu, Qiang; Eamus, Derek

    2012-02-01

    SummaryHealthy phytoplankton communities are the basis of healthy water ecosystems, and form the foundation of many freshwater food webs. Globally many freshwater ecosystems are degraded because of intensive human activities, so water ecosystem restoration is a burning issue worldwide. Selection of key regions for phytoplankton-related restoration is crucial for an effective aquatic eco-restoration. This paper presents a practical method for identification of key regions for phytoplankton-related restoration, using random forests (RFs) method to cluster sites based on dominance, biodiversity, water chemistry and ecological niche. We sampled phytoplankton for species richness and relative abundance and water quality in the Huai River basin (HRB), China to determine the phytoplankton communities' composition and structure and characterize of their ecological niches. A wider mean niche breadth of a species usually leads to a greater overlap with the niche of other species. Using these data and water quality indices, we identified the key regions for phytoplankton-related river restoration activities. Results indicate that our method for recognition of key regions is effective and practical and its application to the HRB identified the Northern Plain area as the key region for restoration. This area is severely polluted and contributes significantly to the HRB phytoplankton communities. Phytoplankton in this region is highly adaptable to environmental change and therefore will be relatively unharmed by environmental instability induced by restoration measures. During restoration, indices of water temperature, total phosphorus and chemical oxygen demand can be altered with little negative influence on phytoplankton communities, but measures that increase ammonia-nitrogen concentration would be highly detrimental. These results will provide valuable information for policy makers and stakeholders in water ecosystem restoration and sustainable basin management in the HRB.

  13. Impact of phytoplankton community structure and function on marine particulate optical properties

    NASA Astrophysics Data System (ADS)

    McFarland, Malcolm Neil

    Phytoplankton are an ecologically important and diverse group of organisms whose distribution, abundance, and population dynamics vary significantly over small spatial (cm) and temporal (minutes) scales in the coastal ocean. Our inability to observe phytoplankton community structure and function at these small scales has severely limited our understanding of the fundamental ecological and evolutionary mechanisms that drive phytoplankton growth, mortality, adaptation and speciation. The goal of this dissertation was to enhance our understanding of phytoplankton ecology by improving in situ observational techniques based on the optical properties of cells, colonies, populations, and communities. Field and laboratory studies were used to determine the effects of phytoplankton species composition, morphology, and physiology on the inherent optical properties of communities and to explore the adaptive significance of bio-optically important cellular characteristics. Initial field studies found a strong association between species composition and the relative magnitude and shape of particulate absorption, scattering, and attenuation coefficient spectra. Subsequent field studies using scanning flow cytometry to directly measure optically important phytoplankton and non-algal particle characteristics demonstrated that the size and pigment content of large (>20 microm) phytoplankton cells and colonies vary significantly with the slope of particulate attenuation and absorption spectra, and with the ratio of particulate scattering to absorption. These relationships enabled visualization of phytoplankton community composition and mortality over small spatial and temporal scales derived from high resolution optical measurements acquired with an autonomous profiling system. Laboratory studies with diverse uni-algal cultures showed that morphological and physiological characteristics of cells and colonies can account for ˜30% of the optical variation observed in natural

  14. Phytoplankton community structure and environmental parameters in aquaculture areas of Daya Bay, South China Sea.

    PubMed

    Wang, Zhaohui; Zhao, Jiangang; Zhang, Yujuan; Cao, Yu

    2009-01-01

    Environmental characteristics and phytoplankton community structure were investigated in two aquaculture areas in Dapeng Cove of Daya Bay, South China Sea, between April 2005 and June 2006. Phytoplankton abundance ranged between 5.0 and 8877.5 cells/mL, with an average of 751.8 cells/mL. The seasonal cycle of phytoplankton were demonstrated by frequent oscillations, with recurrent high abundances from late spring to autumn and a peak stage in late winter. Diatoms were the predominant phytoplankton group, accounting for 93.21% of the total abundance. The next most abundant group was the dinoflagellates, which made up only 1.24% of total abundance. High concentrations of Alexandrium tamarense (Lebour) Balech with a maximum of 603.0 cells/mL were firstly recorded in this area known for high rates of paralytic shellfish poisoning (PSP) contamination. Temperatures and salinities were within the suitable values for the growth of phytoplankton, and were important in phytoplankton seasonal fluctuations. The operation of the Daya Bay Nuclear Power Station (DNPS) exerts influences on the phytoplankton community and resulted in the high abundances of toxic dinoflagellate species during the winter months. Dissolved inorganic nitrogen (DIN) and dissolved silicate (DSi) were sufficient, and rarely limited for the growth of phytoplankton. Dissolved inorganic phosphorus (DIP) was the most necessary element for phytoplankton growth. The enriched environments accelerated the growth of small diatoms, and made for the shift in predominant species from large diatom Rhizosolenia spp. to chain-forming diatoms such as Skeletonema costatum, Pseudo-nitzschia spp. and Thalassiosira subtilis. PMID:19999976

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

    PubMed

    Umaña-Villalobos, Gerardo

    2014-06-01

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

  16. Live Virus Smallpox Vaccine

    MedlinePlus

    ... Index SMALLPOX FACT SHEET The Live Virus Smallpox Vaccine The vaccinia virus is the "live virus" used ... cannot cause smallpox. What is a "live virus" vaccine? A "live virus" vaccine is a vaccine that ...

  17. Cell contact-dependent lethal effect of the dinoflagellate Heterocapsa circularisquama on phytoplankton-phytoplankton interactions

    NASA Astrophysics Data System (ADS)

    Yamasaki, Yasuhiro; Zou, Yanan; Go, Jyoji; Shikata, Tomoyuki; Matsuyama, Yukihiko; Nagai, Kiyohito; Shimasaki, Yohei; Yamaguchi, Kenichi; Oshima, Yuji; Oda, Tatsuya; Honjo, Tsuneo

    2011-01-01

    We used bi-algal culture experiments to investigate and verify the roles of growth interaction between Heterocapsa circularisquama and Prorocentrum dentatum in monospecific bloom formation. Growth of H. circularisquama was slightly inhibited when inoculated at 10 2 cells mL -1 along with P. dentatum at 10 4 cells mL -1. In other combinations of inoculation densities, P. dentatum density rapidly decreased to extremely low levels in the presence of H. circularisquama. We used a mathematical model to simulate growth and interactions of H. circularisquama and P. dentatum in bi-algal cultures. The model indicates that one species will always inhibit the growth of the other and that the relative initial cell densities of the species are critical in determining the outcome. When cultured together under conditions without cell contact, growth of H. circularisquama and P. dentatum was not inhibited. As with P. dentatum, the growth of Heterosigma akashiwo and Skeletonema costatum was inhibited in intact cell suspensions with H. circularisquama, but a nontoxic species, Heterocapsa triquetra, did not affect the growth of P. dentatum or the other species. Similarly, cell suspensions of H. circularisquama showed hemolytic activity toward rabbit erythrocytes, but those of H. triquetra did not. In addition, the cell-free supernatant of H. circularisquama cultures showed no significant hemolytic activity. These results suggest that H. circularisquama causes lethality in P. dentatum by direct cell contact in which live-cell-mediated hemolytic activity might be a contributing factor.

  18. Plankton studies in San Francisco Bay; II, Phytoplankton abundance and species composition, July 1977-December 1979

    USGS Publications Warehouse

    Wong, Raymond L. J.; Cloern, James E.

    1981-01-01

    Data are presented on the phytoplankton species composition and abundance in San Francisco Bay from July 1977 through December 1979. Phytoplankton identification and enumerations were made at selected stations. Sample collections were made at selected stations in the main channel of the Bay from Rio Vista on the Sacramento River to Calaveras Point in South San Francisco Bay, and at shoal stations in the central portion of South San Francisco Bay, San Pablo Bay, and Suisun Bay. Also reported, from October 1978 through December 1979, are the calculated phytoplankton carbon and percent nondiatom carbon, and the species list. This study is one component of an ongoing interdisciplinary study of San Francisco Bay. (USGS)

  19. Mid Pleistocene foraminiferal mass extinction coupled with phytoplankton evolution

    NASA Astrophysics Data System (ADS)

    Kender, Sev; McClymont, Erin L.; Elmore, Aurora C.; Emanuele, Dario; Leng, Melanie J.; Elderfield, Henry

    2016-06-01

    Understanding the interaction between climate and biotic evolution is crucial for deciphering the sensitivity of life. An enigmatic mass extinction occurred in the deep oceans during the Mid Pleistocene, with a loss of over 100 species (20%) of sea floor calcareous foraminifera. An evolutionarily conservative group, benthic foraminifera often comprise >50% of eukaryote biomass on the deep-ocean floor. Here we test extinction hypotheses (temperature, corrosiveness and productivity) in the Tasman Sea, using geochemistry and micropalaeontology, and find evidence from several globally distributed sites that the extinction was caused by a change in phytoplankton food source. Coccolithophore evolution may have enhanced the seasonal `bloom' nature of primary productivity and fundamentally shifted it towards a more intra-annually variable state at ~0.8 Ma. Our results highlight intra-annual variability as a potential new consideration for Mid Pleistocene global biogeochemical climate models, and imply that deep-sea biota may be sensitive to future changes in productivity.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  1. Nutrient control of phytoplankton photosynthesis in the western North Atlantic

    NASA Technical Reports Server (NTRS)

    Platt, Trevor; Sathyendranath, Shubha; Ulloa, Osvaldo; Harrison, William G.; Hoepffner, Nicolas; Goes, Joaquim

    1992-01-01

    Results from several years of oceanographic cruises are reported which show that the parameters of the photosynthesis-light curve of the flora of the North Sargasso Sea are remarkably constant in magnitude, except during the spring phytoplankton bloom when their magnitudes are noticeably higher. These results are interpreted as providing direct evidence for nutrient control of photosynthesis in the open ocean. The findings also reinforce the plausibility of using biogeochemical provinces to partition the ocean into manageable units for basin- or global-scale analysis. They show that seasonal changes in critical parameter should not be overlooked if robust carbon budgets are to be constructed, and illustrate the value of attacking the parameters that control the key fluxes, rather than the fluxes themselves, when investigating the ocean carbon cycle.

  2. Diatom aggregation and dimethylsulfide production in phytoplankton blooms

    SciTech Connect

    Crocker, K.M.

    1994-01-01

    Phytoplankton blooms are crucial links in many of the earth's biogeochemical cycles. Blooms take up atmospheric carbon through photosynthesis, and sequester it on the ocean floo