Análise da influência da geoquímica do ambiente e das características do substrato na estruturação da população de Corbicula flumínea, MULLER 1974, (Mollusca, Bivalvia) no reservatório da usina elétrica de Volta Grande - MG/SP

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Corbicula fluminea (Müller, 1774) is a very common fresh water bivalve specie in Asiatic continent. Nowadays can be found widespread distributed in Europe, North and South America. Considering their high reprodutive rate and spreading capacity of their juvenile plancton forms, this bivalve could be considered as a highly invading specie, being a dominant component in a invaded environment. The present study has done a general survey about the environmental condition and population structure in Volta Grande Hydreletric Power Plant reservoir MG/SP. To do that, six points has sampled inside the study area and monitored during dry and wet seasons. In each sampling points were analyzed the granulometric bottom settled material to determined their petrography and mineralogy composition and quantify the abundant and trace elements . In the reservoir and intersticial water, in addition to quantifyng the same elements, were determined a wide range of physicalchemical parameters. This data were then checked against biological results (abundance and specimens size; abundant and trace elements in their shells) and from use and reservoir occupation in such a way to allow a better understanding about condition parameters and mollusc distribution. The waves and currents occurence during rainning seasons caused water and sediment moviments, provoking some mobility and individuals suspension with consequential aquatic organisms decrease. In spots where the settled bottom material had a thinner granulometry (silt and clay) a sediment suspension occured, causing a filtration decrease capacity and in consequence affecting it distribution. The granulometry couldnt be used to establish the individuals size considering that statistically, each granulometic layer showed significance, leading us to concluded that C. fluminea had similar sizes in all granulometric layers, being capable to colonize a large substrata variety, from rocks and gravels, to sand and clay. From obtained data, this specie hadnt showed preference to any kind of substratum. Could be seen from all physical-chemical parameters analyzed, that C. fluminea is very susceptible to changes in water quality. In addition, their settled life habit turn them as a potencially water quality bioindicator. This could be observed from the analysed variables, by a direct relation between water quality and their abundance. In one of the sampling points, the observed antropic activity by dragging sand for commercial purpouses, clearly had influence in individual sizes collected when the specimens didnt oversised 0,5 mm in length and cannot be saw any variability between dry and rainning seazons. It had realized that antropic activity makes settlement of C. fluminea difficult in the same way as other bentic organisms . The sampling points substratum granulometry showed that C. fluminea presence is not established by substratum preference, but a complex interaction between different factors as oxygen concentration, water pH, year season, waves occurence, etc. The sampling points granulometric characteristics showed big variations in every defined granulometric class and the presence of C. fluminea in each one of those, is an evidence too about the great adaptative capacity of this mollusc in occupying different environments. From the trace elements analysis results, has been possible to conclude that these parameters are into the normality established limits of the CONAMA N 357 Resolution ( 2005/03/17 ).

ASSUNTO(S)

geoquímica substratos materiais granulados Água geologia ambiental

ACESSO AO ARTIGO

Documentos Relacionados