Caracterização espaço-temporal da macrofauna bentônica no estuário do rio Guajará-Mirim, município de Vigia-Pará, Brasil.

Abstract

Estuaries are transitional between the continent and the ocean where rivers meet the sea environments, resulting in measurable dilution of seawater. This study was performed to characterize the composition and distribution of the macroinvertebrate fauna of the estuary Guajará-Mirim river in the municipality of Vigia-PA. For that sampling time and seasonal space were performed on the moon Quadrature bimonthly from September 2011 to July 2012 were pre-established four stations along the estuary, in each of the stations took measurements of pH, salinity, temperature, dissolved oxygen (OD), nitrite (NO2), nitrate (NO3), N ammonium (NH4), phosphate (PO4) and depth. Samples of macrofauna and sediment were collected with a background of type catcher Ekman-Birge (0.0225 m²). Then, the samples were pre-washed in the field on 0.5 mm mesh, packed in a plastic pot with 10% formalin (buffered with borax to prevent decalcification clam) and stained with rose bengal (to make it efficient sorting and subsequent identification) and taken to the laboratory for further identification. The sediment samples were put up in plastic bags, stored in Styrofoam with ice and taken to the laboratory in which they were dried (70 ° C) for later analysis of organic matter and particle size. Laboratory biological samples were identified to the lowest possible taxonomic level. (Type W Shapiro-Wilks test, Kruskal-Wallis test, Man-Whitney test, one-way ANOVA test) and multivariate (RDA) univariate techniques were used for data analysis. The macrofauna were distributed in 33 taxa, consisting mainly of annelids, especially species polychaeta Namalycastis abiuma, Nephtys fluviatilis and Mediomastus californiensis were more abundant and had higher densities throughout the collection period. The results showed spatial variation in the density and richness, diversity and equitability showed already significant temporal structure of macrobenthic associations. The RDA showed that the environmental variables, silt, pH, organic matter (OM) and nitrate (NO3) were the most significant parameters for structuring the macrobenthic community. Overall, despite the low concentrations of salinity of the river estuary Guajará-Mirim, macrobenthos constitutes mainly of estuarine species, with dominance of a few species, maintaining high densities of these organisms throughout the collection period.