A distribuição espacial e a biomassa orgânica de organismos macrobentónicos no Saco da Inhaca

Abstract

ABSTRACT The present work describes the specific composition, distribution and variation of benthic biomass in Saco da Inhaca. Sediment samples were randomly collected for one month with a moving substrate sampling tube to a depth of 20 cm on 5 different substrates. Environmental parameters such as texture, organic matter, salinity, sediment pH and the exposure level of the study area were also analyzed. The results of the sedimentological analysis indicated great similarities in almost all the parameters under study. From this analysis, sands were the most dominant textural portion over clays and silts. As for the level of exposure of the sediment in the substrates where gastropods and bivalves dominated, respectively the pneumatophore zone of Avicennia marina and the sandbank zone, the exposure of the sediment was higher. The lowest level of sediment exposure was found in the channel margins and the muddy substrate, where polychaetes predominated. A total of 103 species of benthic macroinvertebrates were identified in Saco, verifying a dominance in the abundance of gastropods (well represented by the species Assimenea capensis) over the other taxonomic groups. Polychaetes were the most diverse group. The highest abundance was observed in the pneumatophore zone of Avicennia marina due to the predominance of the gastropod Assimenea capensis and the lowest in the muddy substrate zone, where the polychaetes were well represented by the species Dendronereis qrborifera and Prionospio sexculata. more accentuated in the substrates where polychaetes were the most abundant, namely the muddy substrate zone and the channel margin zone and smaller in the remaining substrates where gastropods dominated. Most of the benthic biomass is more represented in the first layers in all substrates. Only polychaetes are found distributed in the middle layers. The total benthic biomass of all species was estimated at an average of 1.3 g AFDW/M2. Gastropods and bivalves had a greater contribution to biomass than polychaetes and the taxonomic group "other species".