hide
Free keywords:
Stream; pond; connectivity; riparian zone; leaf litter; Cerrado
Abstract:
Using standardized artificial substrates (bricks and nylon nets), we analyzed the effect of different treatments on benthic invertebrate colonization in riparian ponds of a Cerrado stream in Mato Grosso, Brazil. Treatments were (1) leaf litter (removal vs. addition of naturally fallen, undecomposed leaves), (2) connectivity (meander pond: direct connection; connected pond: indirect connection; and isolated pond; no connection to the stream) and (3) season (dry vs. rainy season). Benthic invertebrate colonization was generally low. Approximatly 78 % of all animals were chironomids, with microcrustaceans (cladocerans and harpacticoids) together making up nearly 7 %, springtails 3 %, caddisfly larvae 2.1 %, mayfly larvae 1 %. The isolated pond was the least densely colonized habitat, with highly significant lower densities than the two connected ponds (Factorial ANOVAs, p <0.0001). Season had a strong effect on colonization density, which was significantly higher during the rainy than during the dry period (p = 0.001). Significant positive effects of the litter addition treatment on invertebrate colonization were only found during the dry season in the meander pond, where invertebrate densities increased about threefold between litter-free and litter-added treatments (p = 0.03). All other combinations showed a slightly negative, non-significant effect of litter addition. As only few specimen of shredding invertebrates were found, we concluded that recently fallen leaf litter seems to be more important as a mechanical matrix for colonization, FPOM retention and cover from predators, than as a food source in riparian ponds of Cerrado streams.
