Relação da energia fluvial com o padrão de distribuição da espécie Limnoperna fortunei (Dunker) (Mollusca, Bivalvia, Mytilidae)

Abstract

The introduction of exotic species can irreversibly alter natural ecosystems causing irreparable impacts on biological communities, contributing to the extinction of native species and altering the functioning of ecosystems. Biological invasions are thus one of the greatest threats to biodiversity in Brazil and around the world. The species Limnoperna fortunei (Dunker, 1857) popularly known as Golden Mussel, is a species of bivalve mollusk originating in China and the rivers of Southeast Asia. Initially it was registered in Argentina in the estuary of the river La Plata, probably for having introduced by the ballast water of the ships, since then, the species has been dispersed along the basin of the Prata river, already having reached the Pantanal region of Brazil. In 2004, it reached the headwaters of the Paraná River in the central plateau of Brazil. The objective of this work was to contribute to the development of a methodology for mapping areas favorable to larvae accumulation and to test a method using geoprocessing tools, focusing on the study of river fluvial correlation with the spatial distribution of larvae golden mussel. The study area was on the Paranaíba River, one of the formators of the important Paraná River, where a total of 22 stations were sampled, covering the stretch downstream of the São Simão HPP on the Paranaíba River. In the field, the physico-chemical data were taken through a multiparameter probe, and in the laboratory the identification of the larval stages and quantification. It was used in the present work the Relation Extension-RDE index, which is the hydraulic gradient, stream power and analyzed its correlation with the number of larvae in the 22 stations. The average density of the points sampled was 55.3 ind/m3. When analyzed all parameters (density, pH, conductivity and RDE), the result was a negative correlation that is statistically significant (Sperman rank correlation = -0.97) between RDE and larval density indicating that the decrease in RDE increases the number and concentration density of larvae. This work, using methods and techniques of geoprocessing, allowed to identify in an innovative way a direct relationship between the surface flow velocity of the waters and the distribution pattern (number and density of concentration) of L. fortunei larvae. This result has important implications for the analysis and modeling of environmental systems as well as for landscape management, indicating that the higher the river water energy, the lower the larval density found. This work demonstrates that the fluvial geomorphology of the stretches should be considered as an important factor in the distribution and dispersion of the species since it allows to identify that areas with lower levels of energy are favorable to the establishment and colonization of the golden mussel proving that the monitoring efforts should focus on these areas.