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Mesozooplankton production, grazing and respiration in the Bay of Bengal: Implications for net heterotrophy

DRS at CSIR-National Institute of Oceanography

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Title Mesozooplankton production, grazing and respiration in the Bay of Bengal: Implications for net heterotrophy
 
Creator Fernandes, V.
Ramaiah, N.
 
Subject AQUATIC COMMUNITIES::Zooplankton
AQUATIC ECOLOGY, PRODUCTIVITY::Biological productivity
POPULATION STUDIES::Nutrition and feeding habits
 
Description Mesozooplankton samples were collected from the mixed layer along a central (along 88?E) and a western transect in the Bay of Bengal during four seasons covered between 2001 and 2006 in order to investigate spatio-temporal variability in their biomass. At these stations, grazing and respiration rates were measured from live zooplankton hauled in from the surface during December 2005. Akin to the mesozooplankton ?paradox? in the central and eastern Arabian Sea, biomass in the mixed layer was more or less invariant in the central and western Bay of Bengal, even as the chl a showed marginal temporal variation. By empirical equation, the mesozooplankton production rate calculated to be 70?246 mg C mg C -2 d-1 is on par with the Arabian Sea. Contrary to the conventional belief, mesozooplankton grazing impact was up to 83% on primary production (PP). Low PP coupled with very high zooplankton production (70% of PP) along with abundant bacterial production (50% of the PP; Ramaiah et al., 2009) is likely to render the Bay of Bengal net heterotrophic, especially during the spring intermonsoon. Greater estimates of fecal pellet-carbon egestion by mesozooplankton compared to the average particulate organic carbon flux in sediment traps, implies that much of the matter is recycled by heterotrophic communities in the mixed layer facilitating nutrient regeneration for phytoplankton growth. We also calculated that over a third of the primary production is channelized for basin-wide zooplankton respiration that accounts for ~52 Mt C annually. In the current scenario of global warming, if low (primary) productive warm pools like the Bay of Bengal continue to be net heterotrophic, negative implications like enhanced emission of CO2 to the atmosphere, increased particulate flux to the deeper waters and greater utilization of dissolved oxygen resulting in expansion of the existing oxygen minimum zone are imminent.
 
Date 2016-02-04T04:46:36Z
2016-02-04T04:46:36Z
2016
 
Type Journal Article
 
Identifier Journal of Sea Research, vol.109; 2016; 1-12
http://drs.nio.org/drs/handle/2264/4901
 
Language en
 
Rights An edited version of this paper was published by Elsevier. Copyright [2015] Elsevier
 
Publisher Elsevier