Spatial distribution of macrobenthic fauna on three sandy beaches from northern Rio Grande do Sul, southern Brazil

Abstracts

The spatial distribution of benthic macrofauna on the beaches of Tramandaí, Jardim do Éden and Harmonia, was investigated over five consecutive days in April, 2003. The distribution pattern was also analyzed along with environmental parameters. Three transects were set on each beach, 50 m apart, with four sample stations set along each transect. On every station, three samples of benthic macrofauna were taken daily, with a core sampler with 20 cm diameter. In the midlittoral zone, the polychaete Euzonus furciferus and the isopod Excirolana armata dominated. In the swash zone, tidal migrators, Emerita brasiliensis,Donax hanlevanus and Mesodesma mactroides, were the most abundant species and, on some days, the polychaete Scolelepis gaucha. In the lower zones of the beaches, D. hanleyanus,M. mactroides and the amphipod Puelche orensani dominated. This zonation pattern was found for all three studied beaches, based on the average density of each species, over the five days period. Horizontal variation in the fauna was not found, either inter or intra the studied beaches, possibly due to little variability in slope and homogeneity of sediment grain size presented in the three beaches.

benthic macrofauna; spatial and temporal distribution; sandy beaches; Rio Grande do Sul littoral

A distribuição espacial da macrofauna bentônica nas praias de Tramandaí, Jardim do Éden e Harmonia foi investigadadurante cinco dias consecutivos no mês de abril de 2003. Foi analisado também o padrão de distribuição da fauna em relação aos parâmetros ambientais. Foram demarcadas três transversais distantes 50 m uma da outra em cada praia e em cada transversal foram inseridas 4 estações, nas quais foram tomadas diariamente 3 amostras da macrofauna bentônica com um corer de 20 cm de diâmetro. No mesolitoral dominaram o poliqueta Euzonus furciferus e o isópode Excirolana armata. Na zona de varrido, os migradores mareaisEmerita brasiliensis,Donax hanleyanus e Mesodesma mactroides foram os mais abundantes. Nas zonas inferiores das praias, dominaram D. hanleyanus,M. mactroides e o anfípode Puelche orensanzi. Este padrão de zonação foi encontrado para as três praias com base na média da densidade de cada espécie nos cinco dias estudados. Não foi encontrada variação na distribuição horizontal da fauna dentro e entre praias, provavelmente, devido a pouca variabilidade da declividade e a homogeneidade do tamanho do grão de sedimento que apresentaram as três praias.

macrofauna bentônica; distribuição espacial e temporal; praias arenosas; litoral do Rio Grande do Sul

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Publication Dates

• Publication in this collection
  01 Nov 2007
• Date of issue
  Sept 2006

History

• Reviewed
  16 Jan 2006
• Received
  17 Oct 2005
• Accepted
  25 Mar 2006