Inter- and intra-annual variations in the population of Tripos from the Bay of Bengal

Tripos, a species-rich ubiquitous thecate dinoflagel-late, serves as an excellent biological indicator of the water mass in the oceans. The inter- and intra-annual variations in the surface-water distribution of Tripos along the shipping routes of Chennai (C)-Port Blair (P)-Kolkata (K) in the Bay of Bengal was evaluated from October 2006 to September 2011. The highest numbers were recorded during fall intermonsoon (October 2007) in the C-P transect, and southwest monsoon (July 2010) in the P-K transect. In the C-P transect high numbers of T. furca can be attributed to mesoscale eddies, whereas in the P-K transect, it can be attributed to riverine discharge. The results point that, Tripos persists throughout the year in the Bay of Bengal and tend to increase with the elevation of nutrients.