EFFECTS OF TEMPERATURE INCREASE AND NUTRIENT ENRICHMENT ON THE STRUCTURE OF PHYTOPLANKTON FUNCTIONAL GROUPS OF A BRAZILIAN SEMI-ARID RESERVOIR

Maria da Conceição de Souza, Luciane Oliveira Crossetti, Vanessa Becker

Resumo


Aim: Semi-arid region is the most vulnerable region to climatic variability risks. According to the Intergovernmental Panel on Climate Change (IPCC), changes in temperature and precipitation patterns will intensify the drought events that could favor the dominance of cyanobacteria, affecting the water quality. Our study aimed to evaluate through experimental scale, changes in the phytoplankton functional groups structure due to the increase of temperature and nutrients provided by IPCC scenario. Methods: Two experiments were performed, one in a rainy season and another in the dry season. The nutrient enrichment was based on the anuual mean values (August 2012 – August 2013) of soluble reactive phosphorus and nitrate verified in the reservoir. The microcosms were submitted to two different temperatures, five-year average of air temperature in the reservoir (control) and 4°C above the control temperature (warming). The experiment took 12 days long and, at every three days. All species were classified by Reynolds functional groups. Results: The functional groups H1, X1, LOand S1 were the most representative in both seasons. Our results showed that bloom-forming cyanobacteria, especially species of functional groups H1 and M, which are commonly reported in reservoirs of the Brazilian semi-arid region, were not significantly benefited by the warming and nutrients enrichment. The recruitment of other blue green species, as well as diatoms and green algae could be observed. Conclusions: The effects of warming and/or nutritional enrichment can change the structure of the phytoplankton community. However, as not expected as the pessimist scenario, in our study the phytoplankton functional bloom-forming groups did not show changes in its relative biomass. Instead, the recruitment of diatoms and green algae currently found in enriched environments were verified, especially in the rainy period, when usually the nutrients dilution is verified. 


Palavras-chave


Cyanobacteria, experiment, warming, reservoir



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

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