A variação da diversidade de microcrustáceos (Cladocera e Copepoda) a jusante de pequenos reservatórios é influenciada por táxons litorâneos

Abstract

The project consisted of analyzing the fate and dilution of zooplankton assemblages downstream of the reservoirs and streams of the UFSCar Lagoa do Sino campus. We evaluated how ecological attributes change downstream of two reservoirs, in short and/or nycthemeral cycles due to vertical migration effects of zooplankton. The hypotheses tested were: (i) zooplankton dilution occurs from the reservoir, with loss of abundance and diversity; (ii) the behavior is similar in both reservoirs, because the distance is similar even with contrasting vegetation cover and velocity; (iii) the effect of the abrupt reduction of water in the stream as a disturbance does not cause an increase in diversity, due to the small size of the system in terms of flow rate and length of the lotic stretches. A total of 8 points were sampled in each section, 1 in the lentic zone of each reservoir and 6 longitudinally downstream in two sections of the same stream, as it is a cascade system. Sampling was carried out twice during one year, with collections being made every 6 hours for two consecutive days in each campaign. Zooplankton was obtained by filtering 400 liters of surface water through a conical plankton net with a 68-μm mesh opening. Limnological variables were measured by a multiparameter probe. The results show the presence of littoral taxa coming from the reservoirs, and there was an increase in littoral taxa residing in the streams. It can be concluded that there was a dilution of species abundance downstream of the streams, but richness and diversity remained stable due to the contribution of littoral taxa.