Zooplankton community structure in the nearshore waters of central west coast of India

Abstract

Environmental conditions and zooplankton populations were studied in the nearshore waters of Colva and Karwar, along the central west coast of India to assess the spatial and temporal variations in zooplankton composition. Environmental variables (temperature, dissolved oxygen [DO], nitrates, phosphates, turbidity, total dissolved solids [TDS]) and zooplankton taxonomic abundances were studied on a monthly basis from August 2011 to May 2012. The physicochemical data was subjected to principal component analysis (PCA) to test which variables contributed significantly to changes in water conditions. The relationship between environmental variables and zooplankton density was tested using canonical correspondence analyses. Overall, zooplankton species diversity and richness were higher at Colva (35 taxa) than at Karwar (25 taxa). Variation in water quality was attributed to anthropogenic activities and freshwater input in Karwar and seasonal effects in Colva. For Karwar and Colva the primary determinants of zooplankton community structure were turbidity and salinity. Copepods dominated Colva waters throughout the study period, though their species composition exhibited seasonal variations. At Karwar, decapods were prominent during monsoon, while copepods were dominant for the rest of the year. The present study recorded the occurrence of larvae of commercially important Penaeus sp. very close to the shore in Karwar, suggesting that, the turbid waters of Karwar may serve as Penaeus breeding grounds.