hide
Free keywords:
-
Abstract:
From January 1971 till August 1972 ecological studies were carried out on the aquatic macroinvertebrates of the benthos community of three Central-Amazonian inundation forests. The three investigated forests were chosen according to the influence of different water types. These forests were:
1. a site with an inflow of whitewater on Ilha de Curarí, 2. a site in a mixed water area at Lago Janauarí, and 3. a site in a black water area at Rio Tarumã Mirím. The annual water level fluctuations caused
similar ecological conditions concerning seasonal changes, whereas the differences between the forests
depended on the inflow of the different water types.
The benthos composition differs according to the inundation forest type. Stenecious species, occurring only in one of the three forests, as well as euryecious species, inhabiting the three forests, were
found. In addition many species were obtained which live either in white and mixed water or in mixed
and black water.
The soil invertebrates adapted to the annual water level fluctuations. The most common adaptation may be seasonal dispersal, being developed as a migration or a translocation. Migrations could be detected for Campsurus notatus and Eupera simoni in white respectively mixed water. In black waters
numerous species show a translocation, caused by the oxygen deficit of the deep water.
A diapause stage can be assumed for Eupera simoni. This dormant stage enables the bivalve to persist in the forest during the dry period.
Brasilocaenís irmleri assumingly transports its eggs by the current in optimal habitats, where it develops rapidly in 14-21 days.
A dependence on the forest habitat was detected for some species of the mixed and black water.
Other species of the inundation area, particularly of the white water area, are not dependent on the forest habitat.
In addition to seasonal changes in the benthos composition, a vertical stratification was found.
The inundation forest can be subdivided in a river or lake near part, a central part, and a terra firme near part.
The intestinal content studies on the soil invertebrates and the oxygen conditions in the three inundation forests indicate the probable different breakdown of the litter in the forest of the várzea on the one hand and the igapó on the other hand.
Secondary productions could be estimated for the white water area with 10-15 g/m2 and year and for the mixed water area with 90-110 g/m2 and year. In the inundation forest of the mixed water, having the highest production of the three forests, environmental factors like oxygen concentration, sedimentation etc. and trophic factors offer favourable conditions for the inhabitation of the benthos.
