Distribuição e diversidade de Euphausiacea (Crustacea) na Bacia do Espírito Santo e na Bacia de Campos (Brasil)

Abstract

Euphausiids are part of a taxonomic group of great importance for the marine food chain and are among the numerically important zooplanktonic groups. In order to analyze their distribution and abundance in four water masses (TW, SACW, IAW and NADW) present in the Espírito Santo Basin (BES) and in the northern portion of the Campos Basin (PNBC), two oceanographic cruises were carried out, one in 2013 during the dry season and another in 2014 in the rainy season. A total of 80 samples were collected by horizontal hauls in each water mass, using a MOCNESS net system with a 200 µm mesh size of coupled with a flowmeter. After each haul, organisms were fixed in a 4% formaldehyde solution buffered with sodium tetraborate. A total of 5,658 adult individuals and 15,412 larval stage individuals were identified. For the adults, the highest abundances were found in the TW, with a maximum value of 672.15 ind.100 m-3 at station A6, in the dry season. The SACW was the water mass with a greater richness, being the maximum value of 10 species observed at station C6, in the rainy season. The most abundant and frequent species in the BES and PNBC were Euphausia americana and Stylocheiron carinatum. The SIMPROF cluster analysis identified six groups with distinct communities, which are formed mainly by sampling stations of the TW and of the SACW, thus showing that the two water masses with higher euphausiid densities have, each, a community of its own. Euphausia was the most abundant genus regarding to euphausiid larvae and the TW was the water mass with the highest densities, being the maximum value found at station A3 in the rainy season, with 705.18 ind.100 m3 . No changes were observed in euphausiid abundances between the dry and rainy seasons, showing that the BES and PNBC communities do not respond to small temperature, salinity and dissolved oxygen variations.