Relationships between macroinfaunal invertebrates and physicochemical factors in two sandy beaches of Patagonia

Grupo de Ecologi ´a en Ambientes Costeros, Centro Nacional Patagonico (CENPAT–CONICET), Boulevard Brown 2915(U9120ACD) Puerto Madryn, ArgentinaThe interest in the knowledge of the ecology of soft-sediment communities is increasing due to the importance that theseenvironments pose to ecologists and environmentalists. However, the ecology of Argentinean sandy beaches is almostunknown, in spite of being relatively common landscapes. In this work we describe and compare the macroinfaunal assem-blages in the two largest sandy beaches within the Monte Leo´n National Park, the first marine-coastal park of Argentina.Macrobenthic samples were collected and environmental descriptions were performed by quantifying and comparing theorganic matter content, grain size distribution and depth of the substratum available for macroinfaunal colonization.Results show that polychaetes and crustaceans are the dominant taxa and that the two beaches differ in the physicochemicalcharacteristics, suggesting that a relation between the benthic fauna and physicochemical factors exists. Although theyappeared similar at the landscape scale in preliminary visual surveys, the geomorphological differences between habitatsare likely to drive strong differences in the structure of the macroinfaunal assemblages. The monitoring of visible landscapefeatures is likely to undermine the efficiency of protection and managing strategies if not complemented by geomorphologicaland ecological surveys of less visible ecosystem variables.Keywords: sandy shores, conservation, macroinfauna, organic matter content, grain size distribution