Ecophysiological capability of Marenzelleria populations inhabiting North Sea estuaries: An overview

Abstract

The metabolic responses of Marenzelleria cf. wireni, a newly established polychaete worm within North Sea estuaries, to various kinds of environmental stress are summarised. With respect to salinity, M. cf. wireni is able to deal with variations within a wide range. In the process of osmotic acclimation, free amino acids are involved. The major amino acid in terms of osmotic effector is glycine, followed by alanine. Under severe hypoxia, M. cf. wireni switches to an anaerobic metabolism, but at a very low oxygen partial pressure (<3 kPa), which indicates efficient utilisation of oxygen. Anaerobic energy production occurs predominantly via the succinate-propionate pathway. When exposed to hydrogen sulphide, M. cf. wireni is able to cope with high sulphide concentrations (up to 3 mmol l-1), but the pattern of end products of the anaerobic energy metabolism changes. In terms of sulphide tolerance, M. cf. wireni probably is even better adapted than other, indigenous polychaetes. However, in comparison with the sibling species Marenzelleria viridis, which appeared at the same time in European waters but mainly inhabits the coastal inlets of the Baltic Sea in high numbers, the metabolic capabilities of M. cf. wireni seem to be more limited at higher sulphide concentrations (>1 mmol l-1). This might have an influence on the distribution pattern of the two sibling species.