Different degrees of tolerance to hydrogen sulphide in populations of Macoma balthica (Bivalvia, Tellinidae)

Populations of the Baltic clam Macoma balthica show different degrees of sulphide tolerance in relation to s u l p h ~d e contamination of their habitats. Specimens from sulphidic habitats such a s the Gulf of G d k k (Baltic Proper) and shallo~v waters near the island of Hiddensee (Southern Baltic Sea) have higher survival capaclt~es during sulphide exposure than those from low sulphide contaminated environments such as K ~e l Bight (Western Baltic Sea) and the Wadden Sea near Dorum-Neufeld (Weser estuary, North Sea). The tolerant clams are better able to protect cytochrome c oxidase against sulphide toxification. It can b e assumed that this protection is due to slower sulphide diffus~on Into the tissues Sulphide-tolerant specimens from h ~g h l y sulphidic habitats have apparent sulphide d~ffusion coefflc~ents which al-e roughly half those of sulphide-sensitive specimens from low sulphidic stations.