Temporal Variability of Size-fractionated Chlorophyll a Concentration and Influence of Chemical Parameters in Coastal waters of South-eastern Arabian Sea

Abstract

Phytoplankton size structure influences the underwater light field and determines the fate of carbon in a pelagic food chain. Temporal and vertical variations of size fractionated chlorophyll a concentration (Chl-a) were investigated along coastal region off Kochi from May 2013 to April 2014 in order to understand the influence of environmental parameters on phytoplankton size distribution in coastal waters of South-eastern Arabian Sea. The study identified abundance of microphytoplankton around 10m depth, nanophytoplankton from surface to 5m depth and picophytoplankton in 10-20m water column. The results also showed that increased nitrate and phosphate concentration favoured nanophytoplankton growth and increased silicate concentration favoured the growth of microphytoplankton. Pre-showers and extended southwest monsoon along with variation in nutrient concentrations in the area during the study period significantly influenced the variation in size fractionated chlorophyll, absorption by phytoplankton and its numerical density. The results will provide an insight into the chemical factors that control the production cycle in this neritic system and can be used to improve the size fraction algorithms for various societal applications of remote sensing