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Abstract:
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The Arabian Sea and the Bay of Bengal are both highly
dynamic ecosystems, due to the seasonally reversing monsoon winds,
but the processes affecting the mesozooplankton community remain
poorly understood. These are important basins exhibiting enhanced
biological production as a result of upwelling, winter cooling and
other episodic events such as eddies and gyres. Zooplankters are
primarily the prey for almost all fish larvae. Seasonal changes in the
biogeochemical processes can strongly affect zooplankton density
and distribution, which in turn, strongly affect the larval growth, and
consequently, the pelagic fish recruitment. It is clear that plankton
biomass and biogeochemical fluxes are not in steady state. Acoustic
data on mesozooplankton abundance suggests that they also exist in
the mesopelagic zone. Earlier studies were confined only to the upper
200 m and hence the structure of mesozooplankton community in the
deeper layers was not well known. Copepods are the dominant
mesoplankton group, and therefore the majority of the studies were
focused on them. The planktonic ostracods are the second major
crustacean group and at times, their swarms can outnumber all other
planktonic groups. The understanding of the community structure of
the ostracods is essential to establish their role in the marine food
web. Mesozooplankton is responsible for the vertical flux of organic
matter produced by phytoplankton and is assumed to be equivalent to
new production (Eppley & Peterson, 1979). Since the fate of newly
produced organic matter depends upon their consumers, the
zooplankton biomass must be estimated in size fractions or
taxonomic components to understand the vertical flux of organic
carbon. It is thus important to update our knowledge on different
groups of zooplankton on the basis of seasonal and temporal
distribution. The distribution in space and time is essential for
modeling the carbon cycling that structure the marine ecosystems |