An Assessment of the Implications of Seasonal Precipitation and Anthropogenic Influences on a Mangrove Ecosystem Using Phytoplankton as Proxies

The present study aims at finding out the implications of seasonal precipitation in bringing about habitat variability in Sundarbans, the world's largest mangrove ecoregion. This work takes into consideration datasets of 2010 and 2013 from a long-term dataset that is presently being collected for Sundarbans mangrove ecoregion (SBOTS-Sundarbans Biological Observatory Time Series). The purpose of selecting these two datasets was mainly because of the differences in seasonal precipitation which was significantly higher in 2013 as compared to 2010. The study area was selected at the confluence of a creek and estuary where tidal variations were pronounced due to the proximity of the Bay of Bengal. The two stations were specifically selected to spatially segregate the effects of seasonal precipitation and tidal influences especially with regard to habitat variability. Analysis of abiotic variables and nutrient status by a combination of quantitative estimation and statistical methods clearly suggested that habitat variability of the study area was brought about by seasonal precipitation mainly with regard to nitrate concentrations and pH. However, salinity variations remained independent of seasonal precipitation, underlying the importance of tidal fluctuations in this area. The biotic community (phytoplankton) was dominated by diatoms with intermittent availability of chlorophytes and dinoflagellates showing both spatial and temporal changes. Thus, seasonal precipitation along with anthropogenic activities played important role in bringing about habitat variability of the study area with a concomitant effect on spatial and temporal patterns in phytoplankton population in Sundarbans.