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

This study evaluated the effect of the burrowing crab Chasmagnathus granula ta on the benthic community in mudflats of the Mar Chiquita coastal lagoon (Argentina, 37 degrees 45' S, 57 degrees 26' W). A significantly higher abu ndance of the polychaete Laeonereis acuta was found inside the C. granulata crab bed than outside. However, L. acuta abundance decreased in summer pro bably due to the greater activity of crabs. A series of exclusion and inclu sion field experiments showed a combined effect of thr non-burrowing crabs Cyrtograpsus angulatus and C. granulata on the polychaete L. acuta inside c rab beds, and also, an effect of C. granulata on the polychaetes L. acuta a nd Heteromastus similis when added outside the crab bed. C. granulata also affected nematodes, even when experiments were of short duration. The effec t of crab burrows on the small scale distribution of nematodes may be relat ed to passive transport of organisms. Adults of both crab species, Cy. angu latus 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 de termining the benthic community in mudflats of the Mar Chiquita coastal lag oon. (C) 1999 Elsevier Science B.V. All rights reserved.