Marenzelleria cf. viridis and the sulphide regime

To find out how the polychaete Marenzelleria cf. viridis could spread successfully into the habitat of the Darss-Zingst Bodden Chain, one important environmental factor for sediment dwelling animals was examined: hydrogen sulphide. To investigate the stress of this environmental factor, hydrogen sulphide was continuously examined in the pore water of the sediment and burrows of M. cf. viridis. Metabolic activity was recorded by direct and indirect calorimetry. Depending on water temperature, organic matter content of the sediment and salinity, the sulphide concentration in the pore water varied between 1.5 and 4.2 mmol l^-1 being high during summer and in winter when the sediment and overlying water was ice covered. In microcosm experiments water of M. cf. viridis-burrows showed variations in sulphide between 145 and 210 µmol l^-1 but pore water concentration was much higher (6.5 mmol l^-1). In the presence of oxygen animals exhibited an accelerated metabolic rate which was met by a fully aerobic metabolism at Po₂ of 20 to 7.5 kPa and sulphide concentration of 215–245 µmol l^-1. When oxygen is absent the heat production was only slightly elevated (103%) when compared to the anoxic control. The elevated heat production of the animals during sulphide exposure and oxygen may be due to detoxification processes. In this case thiosulphate is formed probably via mitochondrial oxidation and therefore may account for additional ATP-gain.