MEPS 154:175-183 (1997)  -  doi:10.3354/meps154175

The Baltic clam Macoma balthica, a predominant species of macrofauna in the Gulf of Gda´nsk (Poland), is exposed to high concentrations of hydrogen sulphide at many locations in this bay. When oxygen is available, the species is able to detoxify penetrating sulphide mainly by oxidizing it to non-toxic thiosulphate. Sulphide influx rate can be quantified by calculation of the diffusion coefficient for total sulphide. A relatively low apparent diffusion coefficient of about 2 x 10^-6 cm² s^-1 indicates that M. balthica is able to reduce sulphide diffusion by temporary valve closure. During oxic-sulphidic incubation, an equilibrium between sulphide diffusion and detoxification is established at a specific internal sulphide concentration, c_i, which can be calculated by the following equation: c_i = c₀ e^{-k r2e/3D} where c_i = internal sulphide equilibrium concentration, c₀ = external sulphide concentration, k = apparent detoxification constant, r_e = effective radius, and D = apparent diffusion coefficient. The amount of accumulated sulphide in the tissues is strongly dependent on individual size. This is confirmed by experiments as well as by field studies. After specific sulphide incubations, only low internal sulphide concentrations are found in large clams, whereas small clams accumulate much more sulphide in the tissues. Field studies show a distinct reduction in numbers of small clams in high sulphidic areas. We conclude that efficient sulphide detoxification seems possible only if the body size exceeds a certain minimal value.

Macoma balthica · Hydrogen sulphide · Apparent diffusion coefficient · Apparent detoxification constant · Macrofauna · Baltic Sea · Gulf of Gdansk