Lack of seasonal and geographic variation in mesozooplankton biomass in the Arabian Sea and its structure in the mixed layer

Abstract

Mesozooplankton standing stock, abundance and composition were studied during three seasons (summer, winter and inter-monsoon) from coastal and open ocean waters of the central and eastern Arabian Sea in 1994-95. Concentrations were generally higher in the mixed layer compared to deeper strata. A noteworthy feature was that the standing stocks and abundances did not vary significantly between seasons and areas. Vertical migrations appeared to be in a low key. In all seasons herbivores dominated, followed by carnivores. A few species, common in all seasons, accounted the majority of the population. The 'paradox' of the Arabian Sea, that zooplankton biomass remains more or less invariant, despite seasonally varying primary production regimes, could be explained by a microbial loop.