Characterization of the macrozoobenthos in areas under the influence of shrimp farming at the Camurupim River estuary, Piauí State, Brazil

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.