Caracterização do macrozoobentos nas áreas sob a influência da carcinicultura no entorno do estuário do Rio Camurupim, Piauí, Brasil

Abstract

The benthic macrofauna at the Camurupim River estuary was analyzed every three months, from November, 2005 to August, 2006. Sampling was carried out along three sampling-point transects, one at each river bank and one on the river bottom, with five replications at each site. Sampling at the river banks was made with 15-cm diameter PVC collector, introduced 10 cm deep. Sampling on the river boom was done with a Van Veen dredge. The environment was appraised through estimation of salinity, pH, density, phosphorus, calcium carbonate, organic matter content and grain size. A number of 3,848 organisms were identified, making up 83 taxa. Polychaetes, crustaceans, and molluscs were found to be the most abundant with 47.0%, 33.5%, and 11.4%, respectively. Capitellid polychaetes were the only ones found were present in all sampling months. Amongst all identified benthos organisms, Tanaidaceae were predominant over the others, especially in August, but as to mollusks alone, Anomalocardia brasiliana proved to be the most abundant. The between samples comparison of the taxa numbers was made the Kruskal-Wallis test. There was significant difference for density (P=0.0001), for taxa (P=0.0065), for the evenness (P=0.0049) between months, but not for any biotic descriptor comparing the sampling sites. The abundance was found to be higher at the water pumping area of the shrimp farm, with 72.7% of the identified organisms, than on its downstream draining sector.