Limnological variations of a deep reservoir in periods with distinct rainfall patterns Varia es na limnologia de um reservat車rio profundo em per赤odos com diferentes padr es de precipita o

作者：Ana Maria Geraldes; Catherine George

来源：Acta Limnologica Brasiliensia, 2012.

• precipita o
• periodos chuvosos e secos
• limnologia de reservatorios profundos
• comunidade de crustaceos zooplactonicos
• Anabaena flos-aquae
• rainfall
• wet and dry periods
• deep reservoir limnology
• crustacean zooplankton assemblage
• Anabaena flos-aquae

AIM: This study intends to provide information on how precipitation variation may impact environmental parameters (total phosphorus, water temperature, pH, conductivity, dissolved oxygen, Secchi depth, chlorophyll a and Anabaena abundance) and crustacean zooplankton composition and abundance. METHODS: Samples were collected monthly from October 2000 to September 2002 and from October 2007 to September 2009 at one single sampling station located at the deepest point of the reservoir. All data were obtained in the euphotic zone. RESULTS: The highest values of total phosphorous concentrations were reported together with the maximal values of precipitation. Conversely, conductivity decreased during the wet periods. Anabaena presence was only detected between September and December 2001. Daphnia longispina total abundance showed large inter-annual differences. A clear seasonal pattern was inferred for Diaphanosoma brachyurum and Ceriodaphnia pulchella. Both species are thermophilic and begin to be detected in early summer when the water temperature is around 15 oC. Copidodiaptomus numidicus abundance did not present a clear seasonal pattern. CONCLUSIONS: Some of the observed shifts in environmental parameters (Conductivity, total phosphorus concentrations and Anabaena abundance) resulting in changes in zooplankton abundance are induced by rainfall variation. The most affected species were those with a lack of seasonality (C. numidicus) or species occurring mainly in winter/early summer (Daphnia longispina). However, a wide range of physical, chemical and biotic interactions is likely to influence zooplankton abundance. Therefore, caution is advised when relating the observed variation exclusively with rainfall intensity. In fact, some of the observed shifts were induced by other factors varying subtly in a seasonal or inter-annual pattern, independently of rainfall intensity. OBJECTIVO: Com o presente estudo pretende-se obter informa o sobre os impactos da varia o da precipita o nas concentra es de f車sforo total, de clorofila a, oxig谷nio dissolvido, condutividade e profundidade do disco de Secchi, bem como na abundancia de Anabaena flos-aquae e das esp谷cies mais abundantes de crust芍ceos zooplact車nicos. M谷TODOS: As amostragens foram realizadas mensalmente de Outubro de 2000 a Setembro de 2002 e de Outubro de 2007 a Setembro de 2009 num 迆nico ponto localizado na zona mais profunda do reservat車rio. Todos os dados foram obtidos na zona euf車tica. RESULTADOS: As concentra es de f車sforo total foram mais elevadas durante os per赤odos de maior precipita o. Por se