Seasonal variations in carbon biomass of bacteria, thraustochytrids and microzooplankton in the northern Arabian Sea

Show simple item record Ramaiah, N. Raghukumar, S. Gauns, M. Madhupratap, M. 2008-02-22T04:26:34Z 2008-02-22T04:26:34Z 2005
dc.identifier.citation Deep-sea research. Part II. Topical studies in oceanography, Vol.52; 1910-1921p.
dc.description.abstract As a part of the JGOFS-India Programme, abundance of heterotrophic bacteria (Hbac; 0-2000 m), thraustochytrids (0-2000 m), microzooplankton (0-200m occasionally up to 300 m) as well as bacterial growth rates (0-500 m) were studied in the Northern Arabian Sea (NAS) during Spring (SpIM) and Fall intermonsoon (FIM), Northeast Winter (Win) and Summer (SuM) monsoon seasons. Hbac abundance was mostly in the range of 10 sup(8)-10 sup(9) cells l sup(-1) in the surface (0-100 m) and intermediate (150-400 m) depths. Thraustochytrids (heterotrophic protists rich in polyunsaturated fatty acids) were roughly in the range of 10 sup(3) l sup(-1) (nil to approx. 2.7 x 10 sup(5)). Below 200 m, theydecreased drastically to values between nil and 10 l sup(-1). Seasonal differences in carbon biomass of Hbac, thraustochytrids and microzooplankton were more pronounced than those seen in the mesozooplankton. The highest Hbac C biomass was observed during FIM. Bacterial carbon demand (BCD, mg C m sup(-3) d sup(-1); at an assumed 33% conversion efficiency) varied from 0.45 to 40.6 in FIM, 23.43 to 100 in SpIM, 2.31 to 17.5 in Win and from 6.6 to 25.4 in SuM in the top 100 m. In general, with increasing depth the BCD decreased quite rapidly ranging from 0.007 to 1.65 mg C m sup(-1) d sup(-1) below 100 m. In the NAS, heterotrophic bacteria appear to playa significant role in sustaining microzooplankton and the so-called 'Arabian Sea mesozooplankton stable-biomass paradox' through microbial loop. Sizable quantities of Hbac, thraustochytrids and microzooplankton C might be suggestive that Hbac support these microheterotrophs, in mesopelagic zone in particular. Their role in sustaining a variety of deep-water micro- and mesozooplanktonic communities as well as in some ways, the myctophids ingesting marine snow (enriched with bacteria, thraustocytrids and dead organic matter besides zooplankters) is brought to attention.
dc.language.iso en
dc.publisher Elsevier
dc.rights Copyright [2005]. It is tried to respect the rights of the copyright holders to the best of the knowledge. If it is brought to our notice by copyright holder that the rights are voilated then the item would be withdrawn.
dc.subject biogeochemical cycle
dc.subject biomass
dc.subject carbon
dc.subject zooplankton
dc.subject heterotrophic organisms
dc.subject monsoons
dc.subject organic matter
dc.subject saesonal variations
dc.title Seasonal variations in carbon biomass of bacteria, thraustochytrids and microzooplankton in the northern Arabian Sea
dc.type Journal Article

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