Bivalve mollusk assemblages on São Paulo's northern continental shelf, southeast Brazil.
Soft bottom bivalve mollusc assemblages were sampled along a depth gradient (10 to 100 m) on the northern São Paulo shelf during the austral summer and winter. A one-way analysis of similarity permutation test revealed there was no seasonal difference in the structure of the bivalve assemblages in the area. A clustering analysis indicated 3 groups of stations corresponding to the bathymetric gradient. Both K-dominance curves and Shannon and Pielou indexes showed higher biological diversity and higher evenness for the shallower area. Most of the bivalves found were classified as suspension-feeders, co-occurring with deposit-feeder species, suggesting an absence of negative interactions between these trophic groups. Differences in the frequency of disturbance along the depth gradient caused by wave storms--more common in winter--and also by predation and anthropogenic activities, such as dredging of fishing boats and input of gross sewage, likely explain the higher diversity found on the inner shelf of Ubatuba.
Soares-Gomes
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Department of Marine Biology, Fluminense Federal University, C. P. 100.644, CEP 24001-970, Niterói, RJ, Brazil. abiliosg@vm.uff.br
Pires-Vanin
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D000818:Animals; D044822:Biodiversity; D001699:Biometry; D049872:Bivalvia / Q000145:classification*; D001938:Brazil; D011156:Population Density; D012621:Seasons; D012623:Seawater