Spatial distribution of chromium and lead in the benthic environment of coastal areas of the Río de la Plata estuary (Montevideo, Uruguai)

Abstract

Twenty-four sediment samples were collected seasonally during one year from the partially closed Montevideo Bay and the adjacent coastal zone, in Uruguay, in order to determine the impact of chromium and lead in the sediments. Analysis of related environmental variables included bottom water temperature, salinity, pH, dissolved oxygen, and several sedimentological variables such as redox potential and total organic matter. Concentrations and range of variation of these two metals were similar to those found in urbanized and industrialized estuarine environments. Metal enrichment is higher in the bay than in the adjacent coastal zone, however an important increase especially in Pb content was detected in an area previously considered as a pristine one. Considering both metal content and benthic environment characteristics, the study area can be clearly divided in at least two well-defined regions. One is the inner region of the bay near the streams, and the outermost stations of the bay and the adjacent coastal zone form the other. The first one can be considered highly polluted and the other moderately polluted. The values of the metals studied indicated that adverse biological effects are probably occurring, specially in the innermost region of Montevideo Bay.Key words: benthic environment, lead, chromium, Río de la Plata, Uruguay. RESUMO Distribuição espacial de cromo e chumbo no ambiente bentônico de regiões costeiras do estuário do Río de la Plata (Montevidéu, Uruguai)Com o intuito de determinar o impacto do cromo e do chumbo na Bahía de Montevidéu e na zona costeira adjacente, foram coletadas sazonalmente, durante um ano, 24 amostras de sedimento de fundo. Simultaneamente, foram analisadas amostras para temperatura, salinidade, pH e oxigênio dissolvido da água de fundo, além de diversas variáveis sedimentológicas, como potencial redox, matéria orgânica total, entre outras. As concentrações das duas espécies de metais estudadas foram similares às reportadas na literatura para áreas estuarinas industrializadas e urbanizadas. O enriquecimento metálico foi maior na baía do que na área costeira adjacente (Punta Carretas e Punta Yeguas), embora um importante enriquecimento, especialmente de chumbo, fosse observado na região de Punta Yeguas, área previamente considerada não impactada. Tendo por base o conteúdo de metais e as características do ambiente bentônico, a área de estudo pode claramente ser dividida em, ao menos, duas regiões distintas. Uma corresponde à região mais interna da Bahía de Montevidéu, perto da desembocadura dos arroios, e a outra, à região mais externa da baía e à região costeira adjacente. A primeira pode ser considerada Braz. J. Biol., 64(1): 103-116, 2004 104 MUNIZ, P., VENTURINI, N. and GÓMEZ-ERACHE, M.altamente poluída e a segunda, moderadamente. As concentrações dos metais estudados indicaram que estes provavelmente causam efeito biológico adverso, especialmente sobre a macrofauna, sendo mais acentuado na região interna da baía.Palavras-chave: ambiente bentônico, chumbo, crom...

Diatoms, protein and carbohydrate sediment content as proxies for coastal eutrophication in Montevideo, Rio de la Plata Estuary, Uruguay

“…The diatom data in relation to the trophic and salinity gradients presented here fit well with previous trophic state assessments MUNIZ at al., , 2004aVENTURINI et al, 2004;BURONE et al, 2006) but also with the findings proposed by Dell'Anno et al (2002), at least in terms of protein content. Even though previous research in the study area has clearly demonstrated the effects of human impacts on both benthic macrofauna and foraminiferal assemblages, heavy metal contamination and hydrocarbons were utilized as variables MUNIZ at al., , 2004aVENTURINI et al, 2004;BURONE et al, 2006).…”

“…The most heterogeneous sediments are those of the innermost part of the bay, most probably because of the influence of both Pantanoso and Miguelete Streams, which contribute with considerable amounts of sand. This fact had also been observed by Burone et al (2006), Venturini et al (2004) and Muniz et al ( , 2004a. Montevideo coastal zone displayed elevated organic matter percentages similar to those reported in other urban and industrial areas in the world (DELL´ANNO et al, 2002;BIGOT et al, 2006).…”

“…In particular, Actinocyclus normanii and Cyclotella meneghiniana are well known cosmopolitan proxies for aquatic degradation, eutrophication and contamination (PRYGIEL;COSTE, 2000;GARCÍA-RODRÍGUEZ et al, 2007b). Such degradation and hypertrophy of the inner Montevideo Bay have already been documented VENTURINI et al, 2004;MUNIZ at al., , 2004aBURONE et al, 2006). Particularly, Burone et al (2006) analyzed the benthic foraminiferal assemblages and observed that, in Montevideo Bay, there was an extremely poor foraminiferal fauna -including a totally azoic station -thus evidencing the high degree of local contamination.…”

“…Even though previous research in the study area has clearly demonstrated the effects of human impacts on both benthic macrofauna and foraminiferal assemblages, heavy metal contamination and hydrocarbons were utilized as variables MUNIZ at al., , 2004aVENTURINI et al, 2004;BURONE et al, 2006). In the present assessment, we introduce diatom species combined with the biochemical composition of organic matter to assess environmental degradation in the Montevideo coastal zone.…”

“…Thus, the control and management of such industries is a priority issue. Further information on the study area has been published elsewhere MUNIZ at al., , 2004aBURONE et al, 2006). …”