Structure and Productivity of Microtidal Mediterranean Coastal Marshes

Abstract

This paper reviews the literature on structure and production of Mediterranean microtidal marshes. Literature on structure and zonation is relatively abundant but there are relatively few studies of coastal wetland primary productivity in the Mediterranean. These tidal marshes are poorly flushed because of the low tidal range and freshwater tidal marshes are rare. Most marshes are found in deltas and fringing coastal lagoons. Recent studies carried out in the Ebre, Po and Rhone deltas show that net primary production (NPP) of marshes is strongly influenced by soil salinity and flooding. The productivity of these marshes is generally low, but there are significant exceptions. Minimum values of NPP of emergent vegetation (below-plus above-ground) were obtained in salt marshes dominated by Arthrocnemum macrostachyum 237 g m−2 y−1), characterized by low flooding frequency and high salt stress. Maximum values (up to 9685 g m−2 y−1) were obtained in fresh marshes dominated by Cladium mariscus, with high flooding frequency. In general terms, Mediterranean microtidal marsheshave low production due to salt stress and weak tidal flushing. This suggests that there is low export of marsh production to coastal lagoons, bays and open coastal waters.