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.