Impact of Eutrophication on the Seagrass Assemblages of the Mondego Estuary (Portugal)

Abstract

Human population has for long been attracted to live on the shores, imposing major pressures on transitional waters (including estuaries, lagoons) and adjacent coastal areas. A wide array of human impacts may be expected, colliding with the ecological function of these ecosystems and threatening their long-term integrity. Among major threats, eutrophication may be considered as a global ecological problem, affecting several worldwide coastal areas. The Mondego estuary (Portugal) is a coastal system, which has suffered eutrophication over the last three decades leading to major changes in environmental quality. Accordingly, this study addresses the responses of macrobenthic community and different key species to eutrophication, providing an insight on potential impacts for the whole ecosystem integrity. In the late 1990s a restoration plan was implemented in the system to control the eutrophication process and its main effects. A review on these major changes, occurring from 1993 to 2002, will be presented focusing on (1) nutrient dynamics; (2) seagrass and macroalgal dynamics; and (3) macrobenthic community biodiversity, density, biomass, production and feeding guilds composition, evaluating both the type and time of the response to the eutrophication effects. Additionally, six species will also be studied in more detail, which are representative of taxa commonly found at estuaries and other transitional waters, and important for the estuarine foodwebs: Hydrobia ulvae (Gastropoda), Cyathura carinata (Isopoda), Scrobicularia plana (Bivalvia), Hediste diversicolor, Alkmaria romijni and Capitella capitata (Polychaeta).