Seasonal variability in plankton food web composition in Tuticorin coastal waters, south east coast of India

To understand the impact of seasonal variability on plankton food web composition in tropical coastal waters, samples were collected from three locations along Tuticorin coastal waters during postmonsoon, summer, and northeast (NE) monsoon seasons. During the NE monsoon, the total suspended matter (TSM) and nutrient concentrations were relatively higher, whereas salinity and plankton (phytoplankton and zooplankton) abundances were lower. Cluster analysis also revealed that the NE monsoon formed into a separate cluster because of the lower phytoplankton abundance caused by higher loads of TSM; this arrests light penetration, thereby resulting in a decrease in plankton abundance. The increase in zooplankton biomass coincided with the decrease in diatoms (p < 0.05), and the increase in cyanobacteria may reflect that grazers food choice has a significant impact on the base of the food web composition. The present study states that the phytoplankton biomass was greatly influenced by seasonality and associated changes rather than the huge supply of nutrient loads.