Caracterização da fauna bentônica da plataforma continental do Rio Doce - ES

Abstract

The organisms occurring associated to the bottom of the sea, in sandy, mud or rock substrate, since intertidal zone until high depths are called Benthos. Benthic macroinvertebrates refer to aquatic organisms over 0,5 mm in length and comprises most of invertebrate’s taxa. The continental shelf from Espírito Santo State is characterized by the occurrence of rodoliths beds and coral reefs, including the Abrolhos Bank at its northern portion with the purpose of describing the mosaic of sedimentological and biotic composition of the marine benthic habitats from the study area. Samples were collected with 2 liters van Veen dredges. Sample sediment were submitted to 0,5mm sieves and macrofauna was isolated. The organisms were maintained in 10% formalin, sorted and identified at possible taxonomical categories by using optical microscopes equipment. It was sorted 5.726 specimens from 59 samples, and the most abundant were shell of Class Gastropoda, Phylum Bryozoa, isolated valve of Class Bivalvia, Class Scaphopoda. The organism’s occurrences were associated to grain size of the bottom, and Class Gastropoda was registered in coarse and medium sand, while Phylum Bryozoa occurred in medium and fine sand. The valve of Bivalvia, Class Scaphopoda and Class Bivalvia were registered in very coarse, coarse and medium sand. The highest values of Shannon Diversity were detected in samples localized at eastern and south from river mouth SCRD 499, 507,513, 539, with mud and very fine sand and occurrence of Phylum Bryozoa and Phylum Mollusca, represented by valve of Class Bivalvia and Class Scaphopoda. The highest values of Dominance were registered on samples SCRD 479, 481, 517, localized in front of the river mouth, with bottom composed by coarse and fine sand. The dominant taxonomical groups were the Phylum Bryozoa, Phylum Mollusca, represented by the shell of Class Gastropoda. The results evidenced the importance of the kind of bottom on determining the occurrence of taxonomical groups in marine benthic communities.