Spatio-temporal distribution of benthic fauna in mangrove areas in the Bay of Vitória estuary, Brazil

Abstract

The diversity and abundance of fauna may reflect the condition of the mangrove and be used as an indicator of habitat changes, thus the aim of this study is to analyze the distribution of fauna in mangroves under the influence of urban occupation, evaluating the types of forests (basin and fringe), sampling points along the estuary and effects of climatic seasonality through population parameters of crustacean and mollusc epifauna and infauna. Furthermore, this work assesses the influence of environmental variables on the diversity and composition of those communities in the studied forests. For the epifauna, three quadrats of 1 m2 were delimited at each point and the organisms were identified and quantified. For infauna, three sediment samples were collected at each point using a cylindrical sampler and os organisms retained was identified. The environmental variables analyzed were: salinity, standing crops and organic matter in the sediment and granulometry and vegetation data. There was a differentiated distribution of species between of fringe and basin, related to organic matter and standing crops as a consequence of the flooding frequency. The molluscs represented the community with the best response associated with these factors, an aspect justified by their eating and physiological habits. Crustaceans exhibited significant differences with higher diversity and richness in the rainy period, when their reproductive processes occur. For the plant community, Laguncularia racemosa was dominant in the basin and Rhizophora mangle in the fringes, also explaining the differences in the spatial distribution of the fauna. Data from ecological descriptors of crustaceans showed a positive correlation with the areas closest to urban occupation, while molluscs and infauna had a positive correlation with greater structural development of the forest. The mangrove in the Bay of Vitória, although with high anthropogenic pressure, has a diversified fauna and is integrated with vegetation and environmental factors.