Monitoring the effect of seasonal variation on the ocean productivity: a case study in the bay of Bengal

Abstract

The productivity of the ocean is crucial and can be represented by several oceanic parameters. However, the major indicator for ocean productivity monitoring is phytoplankton (Chlorophyll-a) concentration. The productivity of the ocean is now decreasing due to several factors and the rate of declination is even higher in some part of the ocean such as in the Bay of Bengal. Therefore, long-term monitoring of ocean productivity is important, thus the primary goal of this study is to monitor the changes in ocean productivity in the Bay of Bengal due to the seasonal variation. The observation was made based on two seasons i.e. northeast monsoon (November to February) and southwest monsoon (May to September) over a long-term period. The ten-year (from 2001 to 2010) products of Chlorophyll-a concentration from SeaWiFS were used to analyze the spatial and temporal analysis of ocean productivity at the Bay of Bengal. The finding of this study indicates a long-term variation of ocean productivity at the Bay of Bengal for different seasons. It is found that Chlorophyll-a concentration started to increase in the month of October/November and decreased after January, and this trend of Chlorophyll-a concentration change remains the same for over the past ten years. However, no constant rate of change of Chlorophyll-a concentration from year to year has been observed in this study. This study also observed that ocean productivity is highly varied in the Northwestern region of the Bay of Bengal during the northeast monsoon as compared to other regions. In contrary, ocean productivity was found high at Northeastern part of the Bay during the southwest monsoon period. The probable reason for this variation is the monsoon wind that blows in certain directions (e.g. from Southwestern part to Northeastern during southwest) which reduces the water surface temperature, resulting in an increased productivity.