Biochemical composition of zooplankton from Visakhapatnam harbour waters, east coast of India

Proximate composition, zooplankton biomass, protein, lipid, carbohydrate, organic carbon and calorific content of mixed zooplankton in the Visakhapatnam harbour waters were estimated. Biomass varied from 15.2 to 74.0 ml.100 m super(-3) (a.m. = 31.05 plus or minus 17.7) in the outer harbour and 10 to 64.0 ml.100 m super(-3) (a.m.=26.30 plus or minus 14.8) in the inner harbour. Copepods, tintinnids, decapods and chaetognaths formed dominant groups of total zooplankton (> 90%) in the harbour waters throughout the year. Of the biochemical fractions of zooplankton, protein formed the major component, varied from 233.6 to 563 mg.g super(-1) (a.m. = 379.62 plus or minus 107), lipid varied from 61.2 to 181 mg.g super(-1) (a.m. = 103 plus or minus 32.7). Carbohydrate ranged from 65.5 to 127.4 mg.g super(-1) (a.m. = 85.78 plus or minus 16.92), organic carbon varied from 334.9 to 461.2 mg.g super(-1) (a.m. = 380.44 plus or minus 33.6) and calorific values varied from 2.2 to 5.4 (a.m. = 3.5 plus or minus 94) k.cal.g super(-1). Higher values of these constituents were observed during high saline premonsoon and postmonsoon periods when the population densities of copepods, tintinnids, decapods, chaetognaths were high. Significant positive correlations (P < 0.01) observed between calorific values, protein, lipid indicates to certain extent, that latter act as metabolic reserve of the zooplankton. Based on the results zooplankton do not have extensive lipid storage suggesting that protein in addition to the lipid may serve as metabolic reserve. Relatively higher calorific values were attributed to the dominance of copepods in the zooplankton population throughout the year.