Effects of ephemeropterans and shrimps on periphyton and sediments in a coastal stream (Atlantic forest, Rio de Janeiro, Brazil)

Abstract

AbstractWe investigated the importance of shrimps (Atyidae and Palaemonidae) and ephemeropterans (Baetidae) in the removal of periphyton and sediments in a Neotropical stream. The experimental site was open with homogeneous bedrock, shallow depth (8–15 cm), and intermediate water current velocity (0.2–0.3 m/s). We used 2 intensities of electrical current to exclude both shrimps and ephemeropterans (high-intensity treatment) or only shrimps (low-intensity treatment) from fixed areas (180 × 30 cm) of bedrock. When both ephemeropterans and shrimps were excluded in 2 experiments, matter accumulated on the bedrock to 5 and 20× the level in controls; when only shrimps were excluded, no accumulation was observed. Chlorophyll a increased significantly in the high-intensity exclusion, but most of the accumulation was fine organic and inorganic matter. In experiment 1, benthic matter and chlorophyll a decreased by an order of magnitude in areas in which ephemeropterans increased ∼40×. The increase in ephemeropteran...