Studies on the resistance of marine bottom invertebrates to oxygen-deficiency and hydrogen sulphide

Oxygen-deficient and H₂S-containing marine areas are characterized by a decline in the number of species. In laboratory experiments with bottom invertebrates from various biotopes of the North Sea and the Baltic, comparative measurements of the resistance to oxygen-deficiency alone, and to the simultaneous presence of H₂S, were carried out. The resistance values obtained show relations to the substratum on which the species naturally occur. The resistance to H₂S is greater in those macrofauna species which show higher survival rates under oxygen-deficiency. Further experiments with isolated tissues demonstrate that the species specific differences in resistance occurring in whole animals are already based on the cell metabolism. In general, oxygen-deficiency and simultaneous presence of H₂S were endured better in cold than in warmth, and at somewhat reduced pH-values (around 7). The dependence of this resistance on the salinity was only minimal in euryhaline species.