Seasonal variations and inherent variability of selenium in marine biota of a tropical wetland ecosystem: implications for bioindicator species

The present study was designed to study the seasonal variations of selenium in marine biota of different trophic levels collected from Sunderban deltaic complex, northeast India. The primary objective of this work is to provide baseline data for a future environmental quality programme. In general, the sequence of Se accumulation observed in biota is as follows: Bivalve>Zooplankton>Macroalgae>Pisces>Seagrass. An elevated level of Se was recorded during monsoon season. The Se level in zooplankton (∼4 μg/g) was three to four times higher than seagrass. The content of various soft tissues and shell in bivalves molluscs showed an organ-specific pattern in the following order: gill > visceral mass = mantle > adductor muscle > podium > shell. Fish contain less Se in comparison with macroalgae, zooplankton and bivalves revealing poor or insignificant trophic transfer of Se in the marine food chain. Pelecyora trigona (Bivalve) seems to be reliable indicator of Se contamination because of its high accumulation capacity. An in-depth monitoring program is recommended in order to clarify the present trend and to establish the studied biota as indicator species.