The abundance of phytoplankton was lowest during monsoon
months, when the water column was remarkably stratified to a large
extent because of heavy rainfall, high turbidity caused by run-off,
reduced salinity, decreased temperature and pH, overcast sky and
cool conditions. However, during this season, freshwater algal forms
like Anabaena sp., Oscillatoria sp., Chlorella sp., Nostoc sp., Lynbya
sp., Spirogyra sp. Volvox sp. and Spirulina sp. were noticed. The
phytoplankton counts were high during southwest monsoon season
as reported in some of the studies in Bay of Bengal [38]. Similar
observations were made earlier [41-43]. This is being supported by
who stated that phytoplankton and their growth depend on several
environmental factors, which are variable in different seasons and
regions [44]. This kind of cyclic change in the species composition of
phytoplankton was a characteristic feature of the Pichavaram coastal
mangroves [45].