Effect of the burrowing crab Chasmagnathus granulata (Dana) on the benthic community of a SW Atlantic coastal lagoon

This study evaluated the effect of the burrowing crab Chasmagnathus granulata on the benthic community in mudflats of the Mar Chiquita coastal lagoon (Argentina, 37 degrees 45' S, 57 degrees 26' W). A significantly higher abundance of the polychaete Laeonereis acuta was found inside the C. granulata crab bed than outside. However, L. acuta abundance decreased in summer probably due to the greater activity of crabs. A series of exclusion and inclusion field experiments showed a combined effect of thr non-burrowing crabs Cyrtograpsus angulatus and C. granulata on the polychaete L. acuta inside crab beds, and also, an effect of C. granulata on the polychaetes L. acuta and Heteromastus similis when added outside the crab bed. C. granulata also affected nematodes, even when experiments were of short duration. The effect of crab burrows on the small scale distribution of nematodes may be related to passive transport of organisms. Adults of both crab species, Cy. angulatus and C. granulata, also affected the settlement of Cy. angulatus. The juveniles of C. granulata showed no effect for any meiofaunal species. The results of this work showed that C, granulata plays an important role in determining the benthic community in mudflats of the Mar Chiquita coastal lagoon. (C) 1999 Elsevier Science B.V. All rights reserved.