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456 results on '"Zubkov, Mikhail V."'

20. Reconciliation of the carbon budget in the ocean's twilight zone

Author

Giering, Sarah L.C., Sanders, Richard, Lampitt, Richard S., Anderson, Thomas R., Tamburini, Christian, Boutrif, Mehdi, Zubkov, Mikhail V., Marsay, Chris M., Henson, Stephanie A., Saw, Kevin, Cook, Kathryn, and Mayor, Daniel J.

Subjects
Dissolved organic carbon -- Research -- Environmental aspects, Twilight zone (Oceanography) -- Research -- Environmental aspects, Marine zooplankton -- Research -- Behavior, Prokaryotes -- Research, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Photosynthesis in the surface ocean produces approximately 100 gigatonnes of organic carbon per year, of which 5 to 15 per cent is exported to the deep ocean (1,2). The rate at which the sinking carbon is converted into carbon dioxide by heterotrophic organisms at depth is important in controlling oceanic carbon storage (3). It remains uncertain, however, to what extent surface ocean carbon supply meets the demand of water-column biota; the discrepancy between known carbon sources and sinks is as much as two orders of magnitude (4-8). Here we present field measurements, respiration rate estimates and a steady-state model that allow us to balance carbon sources and sinks to within observational uncertainties at the Porcupine Abyssal Plain site in the eastern North Atlantic Ocean. We find that prokaryotes are responsible for 70 to 92 per cent of the estimated remineralization in the twilight zone (depths of 50 to 1,000 metres) despite the fact that much of the organic carbon is exported in the form of large, fast-sinking particles accessible to larger zooplankton. We suggest that this occurs because zooplankton fragment and ingest half of the fast-sinking particles, of which more than 30 per cent may be released as suspended and slowly sinking matter, stimulating the deep-ocean microbial loop. The synergy between microbes and zooplankton in the twilight zone is important to our understanding of the processes controlling the oceanic carbon sink., The global carbon cycle is affected by biological processes in the oceans, which export carbon from surface waters in the form of organic matter and store it at depth, in [...]

Published
2014
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29. High bacterivory by the smallest phytoplankton in the North Atlantic Ocean

Author

Zubkov, Mikhail V. and Tarran, Glen A.

Subjects
Phytoplankton -- Physiological aspects -- Research, Primary productivity (Biology) -- Research -- Physiological aspects, Marine algae -- Physiological aspects -- Research, Environmental issues, Science and technology, Zoology and wildlife conservation, Physiological aspects, Research
Abstract

Planktonic algae < 5 Inn in size are major fixers of inorganic carbon in the ocean (1). They dominate phytoplankton biomass in postbloom, stratified oceanic temperate waters (2). Traditionally, large [...]

Published
2008

30. Loricate choanoflagellates (Acanthoecida) from warm water seas. VI. Pleurasiga Schiller and Parvicorbicula Deflandre

Author

Thomsen, Helge Abildhauge, Kamennaya, Nina A., Zubkov, Mikhail V., Østergaard, Jette Buch, Thomsen, Helge Abildhauge, Kamennaya, Nina A., Zubkov, Mikhail V., and Østergaard, Jette Buch

Abstract

The loricate choanoflagellate genera Pleurasiga and Parvicorbicula are taxonomically ambiguous. Pleurasiga because of the uncertainty that relates to the true identity of the type species, and Parvicorbicula because too many newly described species over time have been dumped here in lack of better options. While all species currently allocated to the genus Pleurasiga (with the exception of the type species) are observed in our samples from the global warm water belt, the genus Parvicorbicula is represented by just a few and mostly infrequently recorded taxa. Two new species, viz. Pl. quadrangiella sp. nov. and Pl. minutissima sp. nov., are described here. While the former is closely related to Pl. echinocostata, the latter is reminiscent of Pl. minima. Core species of Pleurasiga and Parvicorbicula deviate from the vast majority of loricate choanoflagellates in having both the anterior and the mid-lorica transverse costae located exterior to the longitudinal costae. In Pl. quadrangiella there is no mid-lorica transverse costa but rather a small posterior transverse costa located inside the longitudinal costae. In Pl. minutissima the mid-lorica transverse costa has extensive costal strip overlaps which reveal patterns of costal strip junctions that deviate from the norm.

Published
2020

31. Loricate choanoflagellates (Acanthoecida) from warm water seas. VII. Calotheca Thomsen and Moestrup, Stephanacantha Thomsen and Syndetophyllum Thomsen and Moestrup

Author

Thomsen, Helge Abildhauge, Kamennaya, Nina, Zubkov, Mikhail V., Østergaard, Jette Buch, Thomsen, Helge Abildhauge, Kamennaya, Nina, Zubkov, Mikhail V., and Østergaard, Jette Buch

Abstract

The tectiform loricate choanoflagellate genera Calotheca, Stephanacantha and Syndetophyllum have all been first described from warm water habitats and share the presence of flattened and often elaborate costal strips in the lorica. The current reinvestigation does confirm both the widespread occurrence of these taxa within the global warm water belt, and largely corroborates the established genus and species matrix. We describe here Stephanacantha oceanica sp. nov. which closely resembles S. campaniformis, and transfer Parvicorbicula zigzag to the genus Stephanacantha, despite differences in costal strip morphology, but based on a complete agreement in lorica constructional details.

Published
2020

32. Plankton respiration in the Eastern Atlantic Ocean

Author

Robinson, Carol, Serret, Pablo, Tilstone, Gavin, Teira, Eva, Zubkov, Mikhail V., Rees, Andrew P., and Woodward, E. Malcolm S.

Subjects
Atlantic Ocean -- Environmental aspects, Marine plankton -- Environmental aspects, Marine productivity -- Research, Earth sciences
Abstract

Studies of the picoautotroph-dominated oligotrophic areas of the Eastern Atlantic Ocean show that plankton community respiration in these regions exceeds gross production. These areas also exhibit greater phytoplankton turnover rates than bacteria turnover rates, and high ratios between heterotrophic and autotrophic biomass.

Published
2002

33. Comparison of cellular and biomass specific activities of dominant bacterioplankton groups in stratified waters of the Celtic Sea

Author

Zubkov, Mikhail V., Fuchs, Bernhard M., Burkill, Peter H., and Amann, Rudolf

Subjects
Marine plankton -- Research, Microbial metabolism -- Research, Biological sciences
Abstract

A clade of alpha-proteobacteria related to Roseobacter spp., a Cytophaga-Flavobacterium cluster, and a cluster of gamma-proteobacteria produce most of the total bacterioplankton metabolic activity in the Celtic Sea. The smallest cells of the gamma-proteobacteria had the highest growth-specific rates, accounting for their dominance in nutrient-limited waters.

Published
2001

37. Radiometric approach for the detection of picophytoplankton assemblages across oceanic fronts

Author

Lange, Priscila Kienteca, primary, Jeremy Werdell, P., additional, Erickson, Zachary K., additional, Dall’Olmo, Giorgio, additional, Brewin, Robert J. W., additional, Zubkov, Mikhail V., additional, Tarran, Glen A., additional, Bouman, Heather A., additional, Slade, Wayne H., additional, Craig, Susanne E., additional, Poulton, Nicole J., additional, Bracher, Astrid, additional, Lomas, Michael W., additional, and Cetinić, Ivona, additional

Published
2020
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39. Determination of total protein content of bacterial cells by SYPRO staining and flow cytometry

Author

Zubkov, Mikhail V., Fuchs, Bernhard M., Eilers, Heike, Burkill, Peter H., and Amann, Rudolf

Subjects
Bacteria -- Analysis, Plankton -- Analysis, Flow cytometry -- Usage, Proteins -- Analysis, Planktonic bacteria, Biological sciences
Abstract

An assay was designed to measure protein biomass of marine planktonic bacteria by flow cytometry. The procedure was calibrated by employing five species of Bacteria isolated from seawater samples and grown in culture at various temperatures. The intensity of SYPRO-protein fluorescence of these bacteria strongly correlated with their total protein content, measured by the bicinchoninic acid method to be in the range of 60 to 330 fg of protein/cell.

Published
1999

50. Picoplanktonic community structure on an Atlantic transect from 50 degrees N to 50 degrees S

Author

Zubkov, Mikhail V., Sleigh, Michael A., Tarran, Glen A., Burkill, Peter H., and Leakey, Raymond J.G.

Subjects
Plankton research -- Observations, Earth sciences
Abstract

Four categories of picoplankton were discriminated from plankton samples collected from 10 depths at 25 stations along a transect from the British Isles to the Falkland Islands. Each category was counted by flow cytometry and the mean size of bacterial cells was determined. Prochlorococcus occurred at all stations between 47 degrees N and 38 degrees S. There were contrasting compositions of picoplankton communities in the North and South Atlantic between mesotrophic waters.

Published
1998

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