Labile and stable mercury in Harris mud crab (Rhithropanopeus harrisii) from the southern Baltic Sea - Considerations for a role of non-native species in the food web.

Mercury is a potent neurotoxin. Its main source of entry into the human body is the consumption of fish and seafood. Within the past few decades a new species of crab has appeared in the food web of the southern Baltic: Rhithropanopeus harrisii. The aim of the present study was to estimate the level of total and labile mercury concentrations in this species collected from the southern Baltic Sea. Analyses were performed using the thermodesorption method. The share of organic mercury fraction, as well as the Hgtot, increased with the size class of the crabs. Due to the increasingly common occurrence of R. harrisii and the low Hg concentration in its body, and assuming that it is bound to become a more and more common component of the diet of fish, it can be supposed that the load of toxic mercury entering the food web is likely to decrease.