Elemental composition of the biofilm in intertidal estuarine beaches of Uruguay García-Alonso, J.1, Lercari D.2, Ferreira Araujo B.F.3, Almeida, M.G.3, Rezende, CE3. 1Department of Ecology and Evolution, Centro Universitario Regional Este, Universidad de la República, Campus de Maldonado, 20000, Maldonado, Uruguay. Tel. ++598- 42222142. Email: [email protected] 2Unidad de Desarrollo de las Ciencias del Mar (UNDECIMAR) Facultad de Ciencias, Universidad de la Republica, Iguá 4225, 11400 Montevideo, Uruguay. Tel. ++589-25258619 int 334. 3Environmental Sciences Laboratory, Biosciences and Biotechnology Center, Universidade Estadual do Norte Fluminense, Alberto Lamego, 2000, Campos dos Goytacazes, Rio de Janeiro, 28.013-602, Brazil. Tel. ++22-27261618/27261521.

Estuaries and adjacent coasts are places of transition from land to sea, and from fresh to saltwater, becoming globally one of the most productive natural habitats. South-American estuarine coasts of the Atlantic Ocean are already affected by anthropogenic impact or are at risk of potential change due to new industries settlement. Some elements are essentials for life while other might be assumed as markers of anthropogenic activities (pollutants). Elements such as Al, Fe, Ba, Mn, Ca, Cd, Cr, Co, Cu, Ni, P, Pb and Zn were measured in the biofilm of the intertidal areas along the salinity gradient of the Rio de la Plata estuary and oceanic adjacent coast. The intertidal physicochemical characteristics (temperature, conductivity, pH, dissolve oxygen, granulometry and total carbonates content) were used to investigate the anthropogenic impacts of urbanised areas along the Uruguay coast. Biofilm sediment samples were collected directly with a 50 ml centrifuge tube and transported in cool boxes to the laboratory where samples were frozen at -20. Samples were liophilized and total and bioavailable elements were measured by ICP-OES digested with HNO 3 HF-HCl and 1 N HCl, respectively. Univariate (MANOVA) and multivariate methods (PCA) were used to describe the along-shore variations in metal concentrations. More abundant elements were Al, Fe and Ca in all samplings. Anthropic marker elements such as Cr, Pb, Zn and Cu were found at toxic levels in beaches corresponding to Montevideo coast, with similar distribution of P. Ordination of samples highlights the distinctive state of urban beaches, placed unaccompanied along the first principal component, position mainly driven by Hg, Ca and Ni.

Key words: Elemental composition; beaches; Uruguay

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