Benthic assemblages of a temperate estuarine system in South America: transition from a freshwater to an estuarial zone.

CORTELEZZI A; RODRIGUES CAPÍTULO A; BOCCARDI L; AROCENA R

JOURNAL OF MARINE SYSTEMS

ElSEVIER

Lugar: Amsterdam; Año: 2007 p. 569 - 580

0924-7963

The objectives of the present study were to describe the species composition, diversity and distribution of the zoobenthic assemblages, to estimate the abundance and biomass of the dominant species, and to identify the main environmental factors determining the distribution patterns of the invertebrates from a freshwater to an estuarial zone in a temperate estuary of South America (Río de la Plata). It is a micro-tidal system characterized by a high concentration of suspended solids. Fifty-three taxa of meso- and macro-invertebrates were identified in the samples collected during November and December 2001. Molluscs, annelids, crustaceans and nematodes were found at 90% of the sampling sites. Molluscs reached about 90 % of the total zoobenthos biomass: the remaining percentage corresponded mainly to annelids and less to nematodes and crustaceans. An ecocline along the salinity gradient could be observed for the benthic assemblages from a freshwater to an estuarine zone in the Rio de la Plata. A Canonical Correspondence Analysis shows that results from sampling sites in the external zone were strongly related to salinity, depth and pH and less to oxygen and percentage clay. The results from stations of the internal zone, and part of the middle zone, were mainly related to the occurrence of sand and contents of NH4+-N, NO3--N, and PO4 3--P. The paper constitutes an effort to synthesize previous studies and take-on additional biological surveys that will serve as a good foundation for future work.