Composição da nematofauna em uma praia urbana tropical impactada por efluentes de esgoto.

Abstract

Sandy beaches have complex hydrodynamic processes and they are widely used for tourism and recreation. The interstitial space provides habitat for organisms of the Phylum Nematoda, considered the most abundant in unconsolidated bottom benthic ecosystems. The distribution tends to suffer interference, mainly, from granulometry, in addition to other factors. The present study investigated the nematofauna composition on a tropical urban beach impacted by sewage effluents, to test two hypotheses: 1) the structure of the nematofauna community is influenced by granulometric characteristics and 2) the nematofauna composition on the beach of Barra de Jangada presents temporal differences, considering the trophic groups and maturation stages. The collections were carried out in the months of July (rainy season) and September (dry season) of 2020. In each one, two transects were established, one of them located close to a sewage along the intertidal zone and the other distant at 100 meters. In each transect, four sampling points were marked, then biosedimentological replicas and for granulometric analysis were collected. Samples were screened and nematodes identified at the genus level. The sediment was predominantly classified as moderately well sorted fine sand. We recorded 42 genera, belonging to 20 families, Xyalidae being the most representative, with greater abundance and richness of genera. The genera Promonhystera, Theristus, Mesacanthion, Paracanthonchus and Pseudosteineria represented more than 90% of the samples. The greatest richness found occurred in the dry season and, considering the transects, the first one showed greater diversity. The upper midlittoral region had the lowest diversity between the zones in both months. PERMANOVA indicated significant differences in communities and DistLM showed that granulometry significantly influences community composition. The most abundant trophic group was non-selective deposit eaters. Juveniles were dominant in the both periods.