Abundance and diversity patterns of the sessile macrobenthic community associated with environmental gradients in Vitoria Harbor, southeastern Brazil

Harbor terminals and urban sewage effluents affect the composition and distribution of epibenthic organisms. In this study, we hypothesized that the benthic community structure at the Vitoria Harbor changes spatially in a similar to 3 km scale, and that these changes are associated with environmental gradients resulting from point-source sewage and differences in the physical and chemical parameters of the water along the harbor access channel. Four sites, internal (PI), intermediate-internal (PMI), intermediate-external (PME) and external (PE), varying from 0.5 to 4.0 km off the harbor, were sampled on five quadrats at six sampling dates (N = 30 per site). The epibenthic community on the shallow sublitoral rocky shore was sampled fortnightly from December 2005 to February 2006 by point-intersection method. A total of 27 taxa were registered with higher richness and diversity values at the external sites. The similarity analysis indicated two distinct systems, with the internal sites PI and PMI apart from the external PME and PE, which showed 97% of dissimilarity. While the internal sites presented some estuarine characteristics and a high coverage (> 60%) of hydrozoans and bryozoans with silt/clay, the external ones showed coastal water influence and higher amounts of sedimentary material substrate (> 50%). This pattern reflects the estuarine gradient and the suspended sedimentary material at the internal sites, which is carried out to the external parts of the channel. The data showed two distinct benthic communities and support the hypothesis that the community structure varies along the harbor access channel in a gradient from the inner to the outer portion of the estuary.