Anelídeos poliquetas da plataforma continental da costa nordeste semiárida: estados do Ceará, Piauí e Maranhão, na região entre o Rio Coreaú e o Delta do Parnaíba

Abstract

The polychaetes constitute one of the invertebrate groups more abundant and diversified in any marine and estuarine environment, occurring from the intertidal zone to abyssal plain. They are extremely important in terms of biomass, productivity, and number of species; participate significantly of the trophic chain in marine ecosystems; and contribute with a significant parcel of the total diversity of the benthic macrofauna. Despite of their ecological importance, this group is little studied in most of the Brazilian coast, mainly in the North and Northeastern Regions. The semiarid coast of the Northeast Region is characterized by little fluvial input, and is relatively narrow and has low depth. The objective of the present study was increase the knowledge on the polychaete fauna of the continental shelf off Northeastern semiarid coast, as well as characterize it in terms of spatial distribution and relationships with environmental factors. A review on the importance of these animals as indicators of environmental quality was performed. Samplings of sediments and associated fauna, besides measurements of abiotic variables were realizes in 15 sites distributed in three zones of depth (0-20m; 20-40m; 40-60m) at the continental shelf off Ceará, Piauí and Maranhão States, in the zone between Coreaú River (CE) and Parnaíba Delta (MA). It were found 4.385 specimens of polychaetes, belonging to 39 families. The Paraonid family was the most abundant (802 specimens; 18,29%) and frequent (66,7%) in the samples. In terms of feeding guilds, the study area was dominated by deposit feeders both in abundance and richness, independently of the substrate type. The polychaetes did not presented distinct distribution relative to the depth zones, but had significant differences considering the type of substrate. The variable that more contributed to explain the structure of the fauna was the silicate content, directly related to the influence of the sedimentary input of the rivers, mainly Parnaíba River. The Paraonid family was studied more particularly, at the most specific level possible. Twenty species were identified: 14 of the genus Aricidea, 2 of the genus Cirrophorus, besides genera Levinsenia, Paradoneis, Paraonides e Paraonis, each one with a single species. This study presented five new records of species for Northeastern coast (Aricidea cf. cerruti, A. cf. quadrilobata, A. cf. suecica, Cirrophorus cf. furcatus and Levinsenia cf. oligobranchiata), two new records of species (A. cf. wassi and A. cf. pseudannae) and one genus (Paraonides) for the Brazilian coast.