| Resumo: | This research was aimed to monitor and characterize the zooplankton community of Aguieira reservoir (40.33 N; 8.19 W). Aguieira trophic state, nutrient concentration (the highest amounts were observed in summer) and water quality, can be correlated to the internal disturbances induced by the intense water level fluctuations. These criteria indeed lead to an increase in the suspended particulate material in the water column. In addition, the input of allochthonous nutrients originated from human activities in the catchment area will increase the phytoplankton biomass (mainly Cyanobacteria) during summer. The phytoplankton community was dominated by the Cyanobacteria, whereas the zooplankton community by the rotifer, Keratella cochlearis and by the caldoceran, Chydorus sphaericus. In the absence of Cyanobacteria, the subsistence of Copidodiaptomus numidicus, Daphnia longispina and Bosmina coregoni was highly evident. Zooplankton community showed similar spatial and inter-annual patterns. However, n-MDS ordination was able to differentiate between the two identified groups: samples obtained from December-March and from May- September. Canonical correspondence analysis (CCA) identified two main environmental gradients that shape zooplankton community. One being temporal, mainly related to temperature. The other is a trophic gradient which is associated to chlorophyll a concentration, water transparency, nitrates and nitrites. Variance partitioning using CCA revealed that the largest portion (45%) of the total variation observed (70%), was attributed to the interaction between lake and environmental variables.
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