Abstract: Temporal and organ-specific variations of selenium concentration in selected coastal organisms (seagrass, bivalves and fish) were investigated in different biotopes of the deltaic Sundarbans, in the eastern coastal region of India. The bivalves and fish were obtained from local fishermen and were destined for human consumption. The samples were digested with HNO3-H2O2 and selenium was extracted from the aqueous solution with triisooctylamine and stripped with dilute hydrochloric acid. The concentration of selenium was measured by hydride generation-atomic absorption spectrometry. The results obtained were verified using inductively coupled plasma-mass spectrometric and fluorometric methods. The mean selenium concentration found in the various species ranged from 0.05 to 3.94 µg g-1 (dry wt.). It was observed that bivalves accumulated more selenium compared to fish and seagrass. The sequence of selenium levels found was, bivalves > fish > seagrass. In seagrass, the selenium concentration was higher in the roots (0.21±0.03 µg g-1; dry wt.) than the stems (0.17±0.02 µg g-1; dry wt.) and the leaves (0.11±0.01 µg g-1; dry wt.). But, in bivalves, the maximum concentration of selenium was found in the gill (3.94±0.11 µg g-1; dry wt.). The results of the analysis of variance indicated that significant differences in Se concentration were evident between seasons and organs in these species. The variations in uptake of selenium may be due to different metabolic requirements for selenium among the three species, variations in food and differences in interspecies retention and elimination mechanisms.