Effect of the current velocity in the distribution of freshwater macroinvertebrates in rivers of Bonito, Brazilian Center-West / Efeitos da velocidade da correnteza na distribuicao de macroinvertebrados limnicos em rios de Bonito, Centro-Oeste

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The patterns of distribution and abundance of the freshwater macroinvertebrates are determined by the ambient characteristics that take the differences in the availability of resources and shelters against predation and disturbance, thus influencing, the structure of the communities. The current velocity is one of the more important ambient factors in the distribution of these organisms, that able to influence the size of the individuals. In this work it was studied the distribution of macroinvertebrates associates the macrophytes in different speeds of the water with objective 1) evaluating if the variation in the community structure of the macroinvertebrates associates the macrophytes in different rivers and current velocity and 2) to verify if the structure of the molluscs communities is similar in two levels of speed of the water, in relation to the distribution of their sizes. This study it was carried through in two rivers in the region of Bonito, Mato Grosso do Sul, Brazilian Center-West. Twenty-two taxa of macroinvertebrates in the two rivers were collected, represented for 19 families and the Turbellaria, Oligochaeta and Hirundinea classes. The samples were numerically dominated by gastropods, mainly of the Hydrobiidae family and for amphipod of the Hyalellidae family. The snails presented greater density in low speeds, while the amphipod was registered only in the Sucuri river. Significant differences in the richness of species and the mean density of macroinvertebrates between the rivers and current velocities had not been found, but the composition of the communities was different. The samples collected in places with low speed in the Sucuri river was significantly different of those of the Baia Bonita river, while it did not have significant difference in relation to the samples collected in low and high speeds in the same river, although to have a tendency to the separation. On the other hand, the samples gotten in areas of high speed in the Sucuri river had not differed from those of the Baía Bonita river. The four main groups that had contributed for these differences was snails of the families Hydrobiidae and Ancylidae, amphipod and odonate. These families influenced the differences of these communities because they had occurred in different densities in the samples or because they were absent in one of environments. The similarity inside of one river can be related to the presence of great banks of aquatic macrophytes in the study areas that can reduce the speed of the water or provide setting place. There are not observed interactions between the river and the size for the snail s species, suggesting that the factor river did not influence in the variation of the size distribution what also can be resultant of the presence of aquatic plants in environments.

ASSUNTO(S)

molluscs macroinvertebrados moluscos macroinvertebrates ecologia

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