THE EFFECTS OF SEDIMENTATION ON ROCKY COAST ASSEMBLAGES

Abstract

Context and aim of the study Over the past few decades, there have been increases in water turbidity and sediment deposition in coastal areas. Sedimentation has occurred at unprecedented rates all over the world as a consequence of anthropogenic activities, such as deforestation, dredging, industrial and domestic discharges, construction activities and land reclamation. Such increase of sediment loads has been recognised as a major threat to marine biodiversity at a global scale (United Nations Environmental Programme 1995). Changes in sedimentation have been dramatic for some coral reefs, where accelerated deposition caused by unsustainable land practices and dredging resulted in rapid shifts in species composition and abundance, and eventually in irreversible deterioration and loss of coral reefs and associated fishery resources (e.g. Johannes 1975, Amesbury 1982, Cortés & Risk 1985, van Katwijk et al. 1993, Hunter & Evans 1995, Chou 1996, McClanahan & Obura 1997, White et al. 2000; but see Larcombe & Woolfe 1999). The increasing concern about degradation of coastal habitats as a result of anthropogenic increase of sediment loads is reflected in the amount of research that has been directed in recent years towards these problems in both temperate and tropical regions. Several reviews have appeared that discuss the effects of sedimentation in different habitats, including coral reefs (Dodge & Szmant-Froelich 1985, Rogers 1990, Richmond 1993), mangroves (Ellison 1998), seagrasses (Vermaat et al. 1997), freshwater systems (Barko et al. 1991, Henley et al. 2000), and estuaries (Ryan 1991). As the development of many human activities is likely to result in the release of suspended sediments in coastal areas and/or in changes to the regime of sedimentation, understanding the effects of sediments on coastal assemblages and predicting threshold levels of impact for different habitats are fundamental to identifying sustainable management strategies.