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Strong variability in bacterioplankton abundance and production in central and western Bay of Bengal

DRS at CSIR-National Institute of Oceanography

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Title Strong variability in bacterioplankton abundance and production in central and western Bay of Bengal
 
Creator Fernandes, V.
Ramaiah, N.
Paul, J.T.
Sardessai, S.
Jyothibabu, R.
Gauns, M.
 
Subject Bay of Bengal
bacterioplankton
sea-surface salinities
biological productivity
 
Description With large influx of freshwater that decreases sea-surface salinities, weak wind forcing of less than 10 m s sup (-1) and almost always warm (greater than 28 degrees C) sea-surface temperature that stratifies and shallows the mixed layer leading to low or no nutrient injections into the surface, primary production in Bay of Bengal is reportedly low. As a consequence, the Bay of Bengal is considered as a region of low biological productivity. Along with many biological parameters, bacterioplankton abundance and production were measured in the Bay of Bengal during post monsoon (September? October 2002) along an open ocean transect, in the central Bay (CB, 88 degrees E) and the other transect in the western Bay (WB). The latter representing the coastal influenced shelf/slope waters. Bacterioplankton abundances (less than 2 x 10 sup (-9) cells l sup(-1)) were similar to those reported from the HNLC equatorial Pacific and the highly productive northern Arabian Sea. Yet, the thymidine uptake rates along CB (average of 1.46 pM h sup (-1)) and WB (average of 1.40 pM h sup (-1)) were less than those from the northwestern Indian Ocean. These abundances and uptake rates were higher than those in the oligotrophic northwestern Sargasso Sea (less than 7 x 10 sup (8) cells l sup (-1)); av 1.0 pM h sup (-1)). Concentrations of chlorophyll a (chl a), primary production rates and total organic carbon (TOC) were also measured for a comparison of heterotrophic and autotrophic production. In the WB, bacterioplankton carbon biomass equaled approx 95% of chl a carbon than just 31% in the CB. Average bacterial: primary production (BP:PP) ratios accounted for 29% in the CB and 31% in the WB. This is mainly due to lower primary productivity (PP) in the WB (281 mg C m sup (-2) d sup (-1)) than in the CB (306 mg C m sup (-2) day sup (-1)). This study indicates that bacteria?phytoplankton relationship differs in the open (CB) and coastal waters (WB). Higher abundance and contrastingly low bacterial production (BP) in WB may be because of the riverine bacteria, brought in through discharges, becoming dormant and unable to reproduce in salinities of 28 or more psu. Heterotrophic bacteria appear to utilize in situ DOC rather rapidly and their carbon demand is approx. 50% of daily primary production. It is also apparent that allochthonous organic matter, in particular in the western Bay, is important for meeting their carbon demand.
 
Date 2008-03-28T07:05:12Z
2008-03-28T07:05:12Z
2008
 
Type Journal Article
 
Identifier Marine biology, vol.153(5); 975-985p.
http://drs.nio.org/drs/handle/2264/1038
 
Language en
 
Rights Copyright [2008] Springer
 
Publisher Springer-Verlag