Recent Salt Marsh Development and Natural Regeneration of Reclaimed Areas in the Plentzia Estuary, N. Spain

The distribution of benthic foraminifera, a range of elements, and 137Cs and 210Pb were studied in surface sediments and 0·5 m cores from the Plentzia estuarine marshes (northern Spain) to determine the recent development of these previously reclaimed coastal areas. These marshes receive abundant calcium carbonate from regional rocks and this allows calcareous foraminifera to colonize all marsh subenvironments. Good preservation of the original foraminiferal assemblages in the buried sediments is also favoured by high regional background carbonate. Benthic foraminifera are shown to be sensitive to both elevation above mean sea level (exposure) and salinity. Results from the chemical analyses indicate moderate anthropogenic pollution in the estuary, and maximum input seems to have occurred in the 1960s. Recent marsh foraminiferal assemblages are good analogues for the palaeoenvironmental interpretation of historical and Holocene cores, and the combined micropalaeontological/geochemical approach is demonstrated to be successful for the identification of short-term anthropogenic impacts on this coastal region.