Water volume reduction increases eutrophication risk in tropical semiarid reservoirs

Carlos Alberto Nascimento da Rocha Junior, Mariana Rodrigues Amaral da Costa, Rosemberg Fernandes Menezes, José Luiz de Attayde, Vanessa Becker

Resumo


Aim: Global patterns of temperature and precipitation have significantly changed over the last century and nearly all predictions point to even greater changes by the end of 2100. Long periods of drought in the semi-arid region reduce the water level, increasing the susceptibility of lakes to eutrophication due to increased nutrient concentrations in water. This study aims to test the hypothesis that decreasing the water level as a result of prolonged drought, will affect the reservoirs trophic state in Brazilian semi-arid region, increasing the susceptibility of these water bodies to eutrophication. Methods: We studied 16 reservoirs in two sub-basins with contrasting precipitations regimes, inserted on Piranhas-Açu watershed. Piancó basin (PB) is humid and Seridó basin (SB) is dry. Linear regressions analyzes were performed to assess the significance of the relationship between the concentrations of total phosphorus (TP) and chlorophyll-a (CHLA) and the percentage of maximum volume stored (%MVS). In addition, a two factorial analysis of variance (two-way ANOVA) was performed to compare the effects of two variation factors (period and geographical region) on limnologic variables. Results: the results showed a significant reduction in the reservoirs %MVS both for PB and SB regions. At the last period, all reservoirs were classified as eutrophic, but TP concentrations reached much higher values in SB than in PB. The linear regressions analyses showed that the TP were negatively related to %MVS during all sampling periods sampled. The two-way ANOVA results showed that both region and season increased TP. Conclusions: We conclude that the contrasting differences in aridity observed between the two basins affect the water quality and trophic state of the reservoirs. Our findings might help to predict the consequences of climate changes on freshwater ecosystems of Brazilian drylands, using a comparative approach of ecosystems in space-for-time substitution.


Palavras-chave


climate change, eutrophication, semiarid, fountains.



Licença Creative Commons
Este obra está licenciado com uma Licença Creative Commons Atribuição-NãoComercial 4.0 Internacional.

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