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  • Mixotrophy  (3)
  • Phytoplankton  (3)
  • Cell & Developmental Biology
  • General Chemistry
  • Limnology
  • Inter-Research  (7)
  • 2010-2014  (7)
  • 1990-1994
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  • 1
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    Linking bacterivory and phyletic diversity of protists with a marker gene survey and experimental feeding with BrdU-labeled bacteria (2014)
    Inter-Research
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Inter-Research, 2013. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Aquatic Microbial Ecology 71 (2013):141-153, doi:10.3354/ame01674.
    Description: Over the last few decades, molecular methods have vastly improved our ability to study the diversity of microbial communities. In molecular diversity surveys, the function of protists is often inferred from phylogeny. Yet these surveys are unable to distinguish between different trophic modes among closely related taxa. Here we present results from a culture-independent study linking bacterivory to the diversity of pelagic protists from 3 depths of a stratified mesotrophic lake. Bacteria were labeled with bromodeoxyuridine (BrdU) and added to lakewater samples; after incubation, total DNA was extracted from filtered samples. Part of the DNA extract was subjected to immunoprecipitation with anti-BrdU antibodies, and then both whole DNA and BrdU-labeled samples were analyzed using 454-pyrosequencing of the v9 region of 18S small subunit rRNA gene amplicons. The results show that a different community of protists exists at each depth, with limited overlap of taxonomic composition between depths. The community of BrdU-labeled protists, deemed putative bacterivores, is largely a subset of the community found in the whole DNA samples. Many of these BrdU-labeled taxa are poorly represented in GenBank and thus are probably rarely isolated and/or uncultured species. Several of the taxa identified as bacterivores are also phototrophs, highlighting the important role of mixotrophy among eukaryotic microbes. Definitive identity of functional traits among taxa requires careful experimentation, yet this method allows a first-pass assay of the trophic role of microbial eukaryotes from environmental samples.
    Description: This work was funded in part by NSF grants OPP-0838847 and OPP-0838955.
    Keywords: Molecular methods ; Microbial community ; Mixotrophy ; Bromodeoxyuridine ; Culture-independent ; Eukaryotic microbes ; Pyrosequencing ; Lake microbes
    Repository Name: Woods Hole Open Access Server
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  • 2
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    Parasitic infection of the diatom Guinardia delicatula, a recurrent and ecologically important phenomenon on the New England Shelf (2014)
    Inter-Research
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    Publication Date: 2022-05-26
    Description: Author Posting. © Inter-Research, 2014. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 503 (2014): 1-10, doi:10.3354/meps10784.
    Description: Plankton images collected by Imaging FlowCytobot from 2006 to 2013 at the Martha’s Vineyard Coastal Observatory (Massachusetts, USA) were used to identify and quantify the occurrence of the diatom Guinardia delicatula and of a parasite that seems specific to this host. We observed infection with morphological stages that appear similar to the parasite Cryothecomonas aestivalis. Our results show that events during which infection rates exceed 10% are recurrent on the New England Shelf and suggest that the parasites are an important source of host mortality. We document a significant negative relationship between bloom magnitude and parasite infection rate, supporting the hypothesis that the parasites play a major role in controlling blooms. While G. delicatula is observed during all seasons, the infecting stages of the parasite are abundant only when water temperature is above 4°C. The anomalously warm water and small G. delicatula bloom during the winter of 2012 provided evidence that parasites can be active through winter if temperatures remain relatively high. As climate change continues, winter periods of water below 4°C may shorten or disappear in this region, suggesting that parasite effects on species such as G. delicatula may increase, with immediate impacts on their population dynamics.
    Description: This work was supported by grants from NSF’s Ocean Technology and Interdisciplinary Coordination program, NASA’s Ocean Biology and Biogeochemistry program and Biodiversity and Ecological Forecasting program, the Gordon and Betty Moore Foundation, and the National Ocean Partnership Program.
    Keywords: Phytoplankton ; Diatom ; Parasite ; Imaging flow cytometry ; MVCO ; Guinardia delicatula ; Cryothecomonas aestivalis
    Repository Name: Woods Hole Open Access Server
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  • 3
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    A simplified age-stage model for copepod population dynamics (2012)
    Inter-Research
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    Publication Date: 2022-05-25
    Description: Author Posting. © Inter-Research, 2008. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 360 (2008): 179-187, doi:10.3354/meps07314.
    Description: Complex 3D biological-physical models are becoming widely used in marine and freshwater ecology. These models are highly valued synthesizing tools because they provide insights into complex dynamics that are difficult to understand using purely empirical methods or theoretical analytical models. Of particular interest has been the incorporation of concentration-based copepod population dynamics into 3D physical transport models. These physical models typically have large numbers of grid points and therefore require a simplified biological model. However, concentration-based copepod models have used a fine resolution age-stage structure to prevent artificially short generation times, known as numerical ‘diffusion.’ This increased resolution has precluded use of age-stage structured copepod models in 3D physical models due to computational constraints. In this paper, we describe a new method, which tracks the mean age of each life stage instead of using age classes within each stage. We then compare this model to previous age-stage structured models. A probability model is developed with the molting rate derived from the mean age of the population and the probability density function (PDF) of molting. The effects of temperature and mortality on copepod population dynamics are also discussed. The mean-age method effectively removes the numerical diffusion problem and reproduces observed median development times (MDTs) without the need for a high-resolution age-stage structure. Thus, it is well-suited for finding solutions of concentration-based zooplankton models in complex biological-physical models.
    Description: This work was supported by US GLOBEC NOAA grant NA17RJ1223.
    Description: 2013-05-22
    Keywords: Plankton ; Copepods ; Modeling ; Marine ecology ; Oceanography ; Limnology ; Methodology ; Mean age
    Repository Name: Woods Hole Open Access Server
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  • 4
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    Benthic community response to ice algae and phytoplankton in Ny Ålesund, Svalbard (2011)
    Inter-Research
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Inter-Research, 2006. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 310 (2006): 1-14, doi:10.3354/meps310001.
    Description: We assessed the digestibility and utilization of ice algae and phytoplankton by the shallow, subtidal benthos in Ny Ålesund (Kongsfjord) on Svalbard (79°N, 12°E) using chlorophyll a (chl a), essential fatty acids (EFAs) and stable isotopes as tracers of food consumption and assimilation. Intact benthic communities in sediment cores and individuals of dominant benthic taxa were given ice algae, phytoplankton, 13C-enriched ice algae or a no food addition control for 19 to 32 d. Ice algae and phytoplankton had significantly different isotopic signatures and relative concentrations of fatty acids. In the food addition cores, sediment concentrations of chl a and the EFA C20:5(n-3) were elevated by 80 and 93%, respectively, compared to the control after 12 h, but decreased to background levels by 19 d, suggesting that both ice algae and phytoplankton were rapidly consumed. Whole core respiration rates in the ice algae treatments were 1.4 times greater than in the other treatments within 12 h of food addition. In the ice algae treatment, both suspension and deposit feeding taxa from 3 different phyla (Mollusca, Annelida and Sipuncula) exhibited significant enrichment in δ13C values compared to the control. Deposit feeders (15% uptake), however, exhibited significantly greater uptake of the 13C-enriched ice algae tracer than suspension feeders (3% uptake). Our study demonstrates that ice algae are readily consumed and assimilated by the Arctic benthos, and may be preferentially selected by some benthic species (i.e. deposit feeders) due to their elevated EFA content, thus serving as an important component of the Arctic benthic food web.
    Description: Funding for this study came from the National Science Foundation (Grant numbers OPP- 0514115 to W.G.A.; OPP-0222410 to L.M.C.; OPP-0222408 to M.-Y.S.; OPP0222500 to G.R.L.), the Norwegian Research Council (Grant number 151815-720 to M.L.C.), the Howard Hughes Medical Institute through Bates College and the Maine Marine Research Fund.
    Keywords: Ice algae ; Phytoplankton ; Food quality ; Arctic benthos ; Climate change ; Stable isotopes ; Essential fatty acids ; Svalbard
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Mixotrophy : a widespread and important ecological strategy for planktonic and sea-ice nanoflagellates in the Ross Sea, Antarctica (2011)
    Inter-Research
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Inter-Research, 2009. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Aquatic Microbial Ecology 54 (2009): 269-277, doi:10.3354/ame01276.
    Description: Mixotrophic nanoflagellates (MNF) were quantified in plankton and sea ice of the Ross Sea, Antarctica, during austral spring. Tracer experiments using fluorescently labeled bacteria (FLB) were conducted to enumerate MNF and determine their contribution to total chloroplastidic and total bacterivorous nanoflagellates. Absolute abundances of MNF were typically 〈200 ml–1 in plankton assemblages south of the Polar Front, but they comprised 8 to 42% and 3 to 25% of bacterivorous nanoflagellates in the water column and ice cores, respectively. Moreover, they represented up to 10% of all chloroplastidic nanoflagellates in the water column when the prymnesiophyte Phaeocystis antarctica was blooming (up to 23% if P. antarctica, which did not ingest FLB, was excluded from calculations). In ice cores, MNF comprised 5 to 10% of chloroplastidic nanoflagellates. The highest proportions of MNF were found in some surface water samples and in plankton assemblages beneath ice, suggesting a potentially large effect as bacterial grazers in those locations. This study is the first to report abundances and distributions of mixotrophic flagellates in the Southern Ocean. The presence of MNF in every ice and water sample examined suggests that mixotrophy is an important alternative dietary strategy in this region.
    Description: This work was supported by NSF grant OPP-0125833 to D.A.C. and R.J.G.
    Keywords: Ross Sea ; Antarctica ; Mixotrophy ; Mixotrophic nanoflagellates ; Bacterivory ; Plankton ; Sea ice ; Fluorescently labeled bacteria
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Acquired phototrophy in aquatic protists (2011)
    Inter-Research
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    Publication Date: 2022-05-26
    Description: Author Posting. © Inter-Research, 2009. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Aquatic Microbial Ecology 57 (2009): 279-310, doi:10.3354/ame01340.
    Description: Acquisition of phototrophy is widely distributed in the eukaryotic tree of life and can involve algal endosymbiosis or plastid retention from green or red origins. Species with acquired phototrophy are important components of diversity in aquatic ecosystems, but there are major differences in host and algal taxa involved and in niches of protists with acquired phototrophy in marine and freshwater ecosystems. Organisms that carry out acquired phototrophy are usually mixotrophs, but the degree to which they depend on phototrophy is variable. Evidence suggests that ‘excess carbon’ provided by acquired phototrophy has been important in supporting major evolutionary innovations that are crucial to the current ecological roles of these protists in aquatic ecosystems. Acquired phototrophy occurs primarily among radiolaria, foraminifera, ciliates and dinoflagellates, but is most ecologically important among the first three. Acquired phototrophy in foraminifera and radiolaria is crucial to their contributions to carbonate, silicate, strontium, and carbon flux in subtropical and tropical oceans. Planktonic ciliates with algal kleptoplastids are important in marine and fresh waters, whereas ciliates with green algal endosymbionts are mostly important in freshwaters. The phototrophic ciliate Myrionecta rubra can be a major primary producer in coastal ecosystems. Our knowledge of how acquired phototrophy influences trophic dynamics and biogeochemical cycles is rudimentary; we need to go beyond traditional concepts of ‘plant’ and ‘animal’ functions to progress in our understanding of aquatic microbial ecology. This is a rich area for exploration using a combination of classical and molecular techniques, laboratory and field research, and physiological and ecosystem modeling.
    Description: F.N. and C.dV were supported by a SAD grant SYMFORAD from the Région Bretagne (France) and the BioMarKs project funded by the European ERA-net program BiodivERsA.
    Keywords: Mixotrophy ; Radiolaria ; Foraminifera ; Ciliates ; Dinoflagellates ; Kleptoplastidy ; Karyoklepty ; Endosymbiosis ; Myrionecta rubra
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  • 7
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    Total and phytoplankton mediated bottom-up control of bacterioplankton change with temperature in NE Atlantic shelf waters (2011)
    Inter-Research
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © Inter-Research, 2010. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Aquatic Microbial Ecology 58 (2010): 229-239, doi:10.3354/ame01374.
    Description: The regulation of heterotrophic bacterial growth by resource supply (bottom-up control) was temperature-dependent in our analysis of data obtained during 2006 in the euphotic layer of the southern Bay of Biscay (NE Atlantic) continental shelf. The dataset was split into 2 subgroups using 16°C as the boundary between warm and cool waters based on differences in associated physico-chemical conditions, e.g. inorganic nutrient limitation at higher temperatures. The linear regressions between bacterial biomass (BB) and leucine incorporation rates (LIR) were significantly positive in both temperature regimes, thus indicating similar total bottom-up control, albeit with a slightly higher slope in warm waters (0.33 vs. 0.22). However, the relationship of LIR with phytoplankton biomass (chl a), which is an indicator of bottom-up control that is mediated by phytoplankton, was only significant in waters below 16°C. The analysis of bimonthly variations in the BB-LIR and LIR-chl a correlations indicated that the strength of total bottom-up control significantly increased while the role of phytoplankton in supplying DOM to bacteria diminished with mean temperatures over the 12 to 19°C range, suggesting a seasonal switch in the major source of substrates used by bacteria. We show that the abundance of cells with relatively high nucleic acid content (HNA), which are hypothesized to be the most active ones, was positively associated with bacterial production and specific growth rates in cool but not in warm conditions. These results suggest that HNA bacteria are good predictors of bulk activity and production in temperate ecosystems only when the community relies principally on phytoplankton substrates for growth and metabolism.
    Description: X.A.G.M. was partially supported by a sabbatical grant at the MBL from the Spanish Ministry of Education and Science (MEC) and A.C.-D. received an FPI research training predoctoral fellowhip. This work was supported by the time-series project RADIALES from the Instituto Espanol de Oceanografia (IEO).
    Keywords: Bacterioplankton ; Bottom-up control ; Temperature ; Bacterial biomass ; Bacterial activity ; Phytoplankton ; Coastal waters
    Repository Name: Woods Hole Open Access Server
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