Influence of Some Environmental Variables on the Zooplankton Community of Aguieira Reservoir (Iberian Peninsula, Portugal): Spatial and Temporal Trends

Abstract

This research was aimed to assess the spatial and temporal trends in the zooplankton community of Aguieira reservoir at the Mondego catchment (Iberian Peninsula, Portugal) in response to some environmental variables. A total of 24 zooplankton as well as water samples were collected in the months of March (spring), May (early summer), September (late summer) and December (winter) of 2010 and 2011. The data from these samples was obtained by the Descriptive (range, percentage) and multivariate statistics (Non-metric Dimensional Scaling (n-MDS), Bray-Curtis distance, Canonical Correspondence Analysis (CCA). Altogether twenty-three zooplankton species were recorded which included Rotifera (12), Cladocera (8) and Copepoda (3). In terms of abundance, Rotifera (Keratella spp. and Polyarthra sp.) dominated in May and September, while Copepoda (Copidodiaptomus numidicus and Tropocyclops prasinus) overtook in December and March. Cladocera was the least abundant taxon of which Daphnia longispina and Bosmina coregoni has shown abundance from December-March whereas Chydorus sphaericus, Ceriodaphnia pulchella and Diaphanosoma brachyurum from May-September. Results of n-MDS exhibited similar spatial and inter-annual patterns with environmental variables and zooplankton community. However, there were differences between the samples collected in the months of March/December and May/September in both the years. Results of CCA revealed water temperature and algal biomass as the main environmental gradients that influenced the zooplankton community. Since some of the observed changes in the zooplankton composition might be influenced by other complex abiotic/biotic interactions. Therefore this study suggests further research to understand the complexity of the interactions between biological, environmental and climatic parameters of the reservoir. Neverthless, understanding the dynamics and nature of zooplankton communities is crucial for the implementation of good management practices for reservoirs.