The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Rebecca D Scheinberg - One of the best experts on this subject based on the ideXlab platform.
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copepod grazing in a subtropical bay species specific responses to a midsummer increase in Nanoplankton standing stock
Marine Ecology Progress Series, 2000Co-Authors: Albert Calbet, Michael R Landry, Rebecca D ScheinbergAbstract:Ingestion rates of 4 small copepod species (Oithona simplex, O. nana, Acrocalanus inermis and Parvocalanus crassirostris) were investigated in Kaneohe Bay, Hawaii, during a midsummer increase of the pico- and Nanoplankton communities. There was no evidence that adult female copepods fed significantly on picoplankton-sized cells. However, all the species responded behaviorally to variations in the concentration (10 to 110 pg C l -1 ) and size spectrum (relative increase of cells >5 μm) of Nanoplankton prey. The copepods generally behaved as opportunistic particle feeders, demonstrating higher consumption rates on the most abundant cells (2-5 pm Nanoplankton); however, autotrophs were usually selected over heterotrophs of similar size. Maximum ingestion rates were similar for the 2 calanoids and O. nana (around 120000 cells copepod -1 d -1 ) and lower for O. simplex (around 40000 cells copepod -1 d -1 ). but biomass-specific rates of O. simplex equaled those of the other species. At the highest Nanoplankton concentrations, the ingestion rates of copepods appeared saturated, daily rations ranging from 100% body C d -1 for A. inermis to 260% body C d -1 for P. crassirostris. The differences between ingestion rates measured as cells per copepod per day and those converted to carbon suggested that ingestion might be held below potential by the cumulative handling times of individual prey rather than the physiological constraints of food consumption and digestive processing.
Albert Calbet - One of the best experts on this subject based on the ideXlab platform.
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copepod grazing in a subtropical bay species specific responses to a midsummer increase in Nanoplankton standing stock
Marine Ecology Progress Series, 2000Co-Authors: Albert Calbet, Michael R Landry, Rebecca D ScheinbergAbstract:Ingestion rates of 4 small copepod species (Oithona simplex, O. nana, Acrocalanus inermis and Parvocalanus crassirostris) were investigated in Kaneohe Bay, Hawaii, during a midsummer increase of the pico- and Nanoplankton communities. There was no evidence that adult female copepods fed significantly on picoplankton-sized cells. However, all the species responded behaviorally to variations in the concentration (10 to 110 pg C l -1 ) and size spectrum (relative increase of cells >5 μm) of Nanoplankton prey. The copepods generally behaved as opportunistic particle feeders, demonstrating higher consumption rates on the most abundant cells (2-5 pm Nanoplankton); however, autotrophs were usually selected over heterotrophs of similar size. Maximum ingestion rates were similar for the 2 calanoids and O. nana (around 120000 cells copepod -1 d -1 ) and lower for O. simplex (around 40000 cells copepod -1 d -1 ). but biomass-specific rates of O. simplex equaled those of the other species. At the highest Nanoplankton concentrations, the ingestion rates of copepods appeared saturated, daily rations ranging from 100% body C d -1 for A. inermis to 260% body C d -1 for P. crassirostris. The differences between ingestion rates measured as cells per copepod per day and those converted to carbon suggested that ingestion might be held below potential by the cumulative handling times of individual prey rather than the physiological constraints of food consumption and digestive processing.
Timothy J. Bralower - One of the best experts on this subject based on the ideXlab platform.
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Evidence of surface water oligotrophy during the Paleocene‐Eocene thermal maximum: Nannofossil assemblage data from Ocean Drilling Program Site 690, Maud Rise, Weddell Sea
Paleoceanography, 2002Co-Authors: Timothy J. BralowerAbstract:[1] Nannoplankton assemblages at Ocean Drilling Program Site 690 (Maud Rise, Weddell Sea) experienced an abrupt and dramatic transformation at the onset of the Paleocene-Eocene Thermal Maximum (PETM) at ∼55 m.y. The major assemblage shift suggests a change from colder, more productive surface waters to warmer, more oligotrophic conditions. Significant restructuring of assemblages during the later part of the PETM indicates that nannoplankton communities were not stable and that surface water conditions changed, although they remained warm and oligotrophic. Combined with benthic foraminiferal assemblage data, nannoplankton assemblage results suggest increased sequestration of nutrients in shelf environments and starvation of the open ocean. Although the PETM was a short-lived event, it appears to have had long-term effects on nannoplankton, leading to the extinction of Fasciculithus, a dominant Paleocene genus.
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evidence of surface water oligotrophy during the paleocene eocene thermal maximum nannofossil assemblage data from ocean drilling program site 690 maud rise weddell sea
Paleoceanography, 2002Co-Authors: Timothy J. BralowerAbstract:[1] Nannoplankton assemblages at Ocean Drilling Program Site 690 (Maud Rise, Weddell Sea) experienced an abrupt and dramatic transformation at the onset of the Paleocene-Eocene Thermal Maximum (PETM) at ∼55 m.y. The major assemblage shift suggests a change from colder, more productive surface waters to warmer, more oligotrophic conditions. Significant restructuring of assemblages during the later part of the PETM indicates that nannoplankton communities were not stable and that surface water conditions changed, although they remained warm and oligotrophic. Combined with benthic foraminiferal assemblage data, nannoplankton assemblage results suggest increased sequestration of nutrients in shelf environments and starvation of the open ocean. Although the PETM was a short-lived event, it appears to have had long-term effects on nannoplankton, leading to the extinction of Fasciculithus, a dominant Paleocene genus.
David A. Caron - One of the best experts on this subject based on the ideXlab platform.
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Abundance and distribution of phototrophic and heterotrophic nano- and microplankton in the southern Ross Sea
Deep-sea Research Part Ii-topical Studies in Oceanography, 2001Co-Authors: Mark R. Dennett, David A. Caron, Sylvie Mathot, Walker O. Smith, Darcy J. LonsdaleAbstract:Phototrophic and heterotrophic Nanoplankton (PNAN, HNAN; 2–20mm protists) and microplankton (PMIC, HMIC; 20–200mm protists and micrometazoa) are major taxa involved in partitioning carbon and energy within the pelagic food web. In the Ross Sea, Antarctica, plankton biomass appears to be controlled by the seasonal recession ofthe sea ice and the f ofthe Ross Sea polynya during the short austral spring-summer period. During four cruises in 1996–1997 within the southern Ross Sea as part of the US JGOFS program, we determined the abundances and biomasses ofphototrophic and heterotrophic Nanoplankton and microplankton primarily along a transect at 76130 0 S. The colonial prymnesiophyte Phaeocystis antarctica (excluding mucus carbon) contributed significantly to community structure during both non-bloom and bloom periods (B25% and 90%, respectively, ofmicrobial biomass). However, shif ts occurred both seasonally and spatially between a diatom/heterotrophic dinoflagellate and a colonial P. antarctica-dominated assemblage. While Nanoplankton biomass varied o50% during any particular cruise, PNAN and HNAN biomass ranged more than three orders ofmagnitude among the f our cruises (0.1–359 and 1.5–268 mmol C m � 2 , respectively). Cruise averages ofPMIC biomass ranged f rom 2.5 to 530 mmol C m � 2 , and a maximum biomass of1530 mmol C m � 2 was observed during the bloom ofcolonial P. antarctica in summer. Average heterotrophic biomass was o30% ofthe total microbial biomass (excluding bacteria) from early austral spring through summer. This value rose to E87% in autumn following the decline and disappearance of P. antarctica. The contribution oftotal nano- and microplankton biomass to POC in the upper 60 m over the three sampled seasons varied from 7% to 52.4% with an overall average of 21.8% for all four cruises which is comparable to contributions of these assemblages in other oceans even with the strong seasonal dominance of P. antarctica. r 2001 Elsevier Science Ltd. All rights reserved.
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heterotrophic and mixotrophic Nanoplankton predation on picoplankton in the sargasso sea and on georges bank
Marine Ecology Progress Series, 2000Co-Authors: Robert W Sanders, Ulrikeg Berninger, Ee Lin Lim, Paul F Kemp, David A. CaronAbstract:Nanoplankton and picoplankton abundance and community grazing on picoplankton were deterrnined in surnmer and autumn at several stations in a productive coastal environment (Georges Bank. NW Atlantic Ocean) and in an oligotrophic oceanic ecosystem (Sargasso Sea). Ranges of heterotrophic Nanoplankton (HNAN) abundance were 1.2 to 3.6 X 103 ceils rnl-' on Georges Bank, and 2.2 to 6.8 X 10' ceiis ml-' in the Sargasso Sea. Ranges of phototrophic Nanoplankton (PNAN) abundance in these ecosystems were 1.9 to 6.0 X 103 and 1.3 to 4.7 X 102, respectively. Mixotrophic Nanoplankton (MNAN), operationaiiy defined here as chloroplast-bearing Nanoplankton that ingested fluorescent tracers, comprised an average of 12 to 17% of PNAN in surface waters in both environments during August and October. Mixotrophs at specific stations constituted as much as 38% of total PNAN abundance on Georges Bank and 30 % in the Sargasso Sea. Mixotrophs represented up to 39 % of the total phagotrophic Nanoplankton abundance (MNAN/[MNAN + HNAN]). Community grazing impact was estimated from the disappearance of fluorescent prey surrogates (fluorescently labeled bacteria, FLB; cyanobacteria, FLC; and <3 pm algae, FLA). Absolute grazing rates (total picoplankton cells removed d-') on Georges Bank exceeded those in the Sargasso Sea due to the greater abundances of predators and prey. However, there was overlap in the specific grazing losses at the 2 sites (ranges = 0.08 to 0.38 d-' in the coastal ocean and 0.05 to 0.24 d-' in the oligotrophic ocean). Rates of bactenvory were in approximate balance with rates of bactenal production (3H-thymidine uptake), but production exceeded bacterivory on Georges Bank during the surnmer cruise. These data are among the first documenting the impact of grazing on picoplankton in these environments, and they are consistent with the prediction that Nanoplanktonic protists are major predators of picoplankton. While the proportion of phototrophs that are phagotrophic was highly variable, our study indicates that algal mixotrophy is widespread in the marine environment, occurring in both coastal and oligotrophic sites, and should be considered quantitatively in microbial food web investigations.
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the ecology of paraphysomonas imperforata based on studies employing oligonucleotide probe identification in coastal water samples and enrichment cultures
Limnology and Oceanography, 1999Co-Authors: Mark R. Dennett, David A. CaronAbstract:The geographical distribution and seasonal abundance of the cosmopolitan heterotrophic flagellate Paraphysomonas imperforata in several coastal waters was examined using species-specific oligonucleotide hybridization probes which target small subunit ribosomal RNA. P. imperforata was found to occur in several coastal environments, but at very low abundances (typically ,50 cells ml 21 ). The seasonal abundance of P. imperforata examined at one sampling site remained consistently low and constituted no more than 1% of the total Nanoplankton at any time during a 17-month sampling period. In contrast to the low abundances observed in natural water samples, P. imperforata frequently dominated heterotrophic enrichment cultures prepared from these same samples, comprising up to 98% of the total Nanoplankton. Based on these findings, we conclude that P. imperforata is an opportunistic species capable of growing rapidly to high abundances when prey concentrations are high. Water and enrichment temperature as well as the temperature tolerance range of P. imperforata appear to have played a role in the seasonal differences observed in P. imperforata dominance. Experiments with enrichment cultures indicated that the absolute abundances of P. imperforata in the water samples and the activity of consumers of Nanoplankton also influenced the degree to which P. imperforata dominated the heterotrophic Nanoplankton assemblages of enrichment cultures. Seasonal changes in water temperature might also affect these latter factors, and, as a consequence, indirectly influence the ability of P. imperforata populations to dominate enrichments. Our results support the notion that enrichment cultivation of heterotrophic flagellates, and perhaps incubations in general, can select for species such as P. imperforata that may not be representative of Nanoplanktonic protists that numerically dominate natural assemblages.
Akira Taniguchi - One of the best experts on this subject based on the ideXlab platform.
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standing crops of planktonic ciliates and Nanoplankton in oceanic waters of the western pacific
Aquatic Microbial Ecology, 1998Co-Authors: Toshikazu Suzuki, Nobuyuki Yamada, Akira TaniguchiAbstract:The vertical distribution of planktonic ciliates and Nanoplankton was investigated in 3 types of oceanic waters in the western Pac~f~c . Ranges of their standing crops, in abundance and biomass, were 50 to 2540 cells 1-' and 4.89 X 104 to 6.32 X 106 pg C I-' for ciliates and 7.2 X 104 to 1.97 X 106 cells I-' and 2.45 X 10' to 4.92 X 10' pg C 1-' for Nanoplankton in the spring subarctic water,
Nanoplankton in the fall subarctic water, and c570 cells 1" and <1.59 X 106 pg C 1.' for ciliates and 1.45 X 105 to 3.18 X 106 cells I ' and 3.05 X 10' to 2.62 X 107 pg C 1-' for Nanoplankton in the subtropical water. The standing crop of ciliates, as a whole, was positively correlated to that of Nanoplankton especially in biomass: B, = 0.211 X B,,'"'"", r = 0.81, p < 0.001, where B, and B, are biomass of ciliates and Nanoplankton, respectively. This suggests that Nanoplankton and ciliate stocks are t~ghtly linked in oceanic waters.
