Bathymetric distribution and diversity variation of macrobenthic invertebrates on the continental shelf and upper slope of southern Brazil

Abstract

This study analyzed the bathymetric distribution and diversity variation of macrobenthic invertebrates on the continental shelf and upper slope of southern Brazil (32º 10’S o 33º 45’S) as well as their relationship with environmental conditions. three hundred twenty species were collected with a 1m width rectangular dredge in 90 stations between depth of 11 and 500m. Low species numbers at 11-20m and 83-105m depths coincided with homogeneous substrates, while areas of high richness (33-45m and 150-500m) were related to heterogeneous substrate. The limit between inner and middle shelf, nearly 50m depth, and the outer shelf (100-200m) were characterized as zones of faunistic changes. Low species number in the middle shelf was probably related to substrate homogeneity and low temperatures, due to austral winter ingression of Sub Antartic Shelf Water, over thermophylic species. The species equitativity increased from the outer shelf (100-200m) to maximum values on the upper slope (500m).