Zooplankton production, composition and diversity in the coastal waters of Goa

Abstract

Spatial and temporal variability in zooplankton production, composition and diversity in the coastal waters of Goa were studied. Zooplankton production was bimodal with primary peak during September-October and secondary peak during March-April. Secondary production computed from the zooplankton biomass values fluctuated between 24.7 and 87.2 mgC.m sup(-2) d sup(-1) . Herbiores dominated the zooplankton community and copepods were most abundant. Cladocerans, pteropods and decapod larvae, sergestids, siphonophores, chaetognaths and fish eggs were the other common taxa. Zooplankton population was never dominated by a single group. Swarms of copepods (Temora turbinata), cladocerans (Evadne tergestina), and pteropods (Creseis acicula) occurred in the nutrient enriched enriched environment during early postmonsoon months (October-November). Swarming of these zooplanktonic forms resulted in high biomass but low diversity community. Faunal and species diversity were enhanced with increase of carnivores in the ecosystem. An inverse relationship between zooplankton biomass and species diversity was the general trend. A total of 58 species of pelagic copepods belonging to calanoids(42), cyclopoids (12) and harpacticoids(4) were identified. The occurrence and abundance were influenced by seasons, depth of sampling station and prevailing hydrographic conditions. Niche partioning among congeners was evident.