Po bioaccumulation and trophic transfer in marine food chains in the northern Arabian Gulf.

The tendency of Po to concentrate in body tissue poses a serious concern of radiological safety. This study compiles available information and presents recent Po data for the marine food web in the northern Gulf waters. Since Po is concentrated in marine biota, a large number of samples of various marine organisms covering several trophic levels, from microalgae to sharks, were analyzed. Po was found to be highly concentrated in several marine species with the highest Po concentrations found in yellowfin tuna, i.e. 37.3-44.9, 451-548, and 1511-1693 Bq kg wwt in muscle, digestive system and liver, respectively. In most dissected fish samples, Po showed increasing concentrations in the following order: edible tissue, gills, digestive system, liver and fecal matter. Fish feces had Po concentrations several orders of magnitude higher than that in seawater, fish muscle, and the fishes' ingested food. The high Po concentration in fish fecal matter suggests that the bulk of Po content in fish is eventually excreted back into the environment as fecal pellets. In most fish high concentrations were noted in liver, with the highest Po concentration recorded in yellowfin tuna liver. Moreover, Po concentration in the soft tissue of tunicate and bryozoan samples were 872-1012 and 402-527 Bq kg wwt, respectively, far higher than that in fish muscle (0.04-44.9 Bq kg wwt). It was observed that the maximum Po concentration in edible fish tissue among the fish in trophic level 2 was an order of magnitude lower than those in trophic level 3 and two orders of magnitude lower compared to fish in trophic level 4. The highest concentrations in the muscle tissue were observed in the following order: tunicate > bryozoan > mollusc > crustacean > algae > fish. Among all the biota analyzed, the highest overall concentration of Po was noted in yellowfin tuna (Thunnus albacores) indicating a potential biomagnification of Po in this particular top predator species. In general, Po concentrations found in the commercially important fish from Kuwaiti waters were comparable to levels that have been reported for similar fish species from several other marine areas worldwide.