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SEPG 2094 - Date Awarded 2002
Ecological Role of Two Species of Estuarine Crabs: a case of Functional Redundancy?
Gabriela Palomo
Abstract
Several models of ecological organization propose that function of different species overlap, and if one species is removed, ecological function may persist through the replacement of other species with similar function. In this study, we investigated if Cyrtograpsus angulatus is a functional redundant species comparing the effect of C. angulatus and Chasmagnathus granulata on sediment characteristics. Density of C. angulatus burrows, burrows diameter, crabs size, crab sex proportion, sediment water content, organic matter content, grain size proportion and infauna were evaluated with an spatial analysis. Feeding mode of crabs was determined analyzing the stomach content of 160 individuals. Manipulative experiments were performed in Mar Chiquita coastal lagoon to distinguish between the effect of C. granulata, C. angulatus or both species on sediment water content, organic matter content and grain size. Our results showed that Cyrtograpsus angulatus inhabit in dense crab beds in Caleta Valdés. The spatial distribution of burrows was correlated with the sediment grain size (silt proportion) and the organic matter content. The crabs fed mainly on sediment and only in several individuals, polychaetes or nematodes were found. Results from the experiments suggest that both crabs decreased the water content, organic matter content and the silt proportion of the muddy sediments. Interactions such as competence are strongest among species with similar functions and this enhances the functional diversity through and across an ecosystem. This diversity is necessary to maintain the possibility of recover of an ecosystem.
Full report: SEPG2094
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