AEI prepress abstract  -  DOI: https://doi.org/10.3354/aei00256

Characterization of phytoplankton communities by pigment analysis and the detection of toxic cyanobacteria in Brazilian freshwater reservoirs with aquaculture production

Louise Schlüter*, Gianmarco S. David, Niels O. G. Jørgensen, Raju Podduturi, Andréa Tucci, Andréa S. Dias, Reinaldo José da Silva

*Email: lsc@dhigroup.com

ABSTRACT: The intensified use of water bodies and reservoirs for example for aquaculture production, increases the need for monitoring and early warning of toxins from cyanobacteria. To minimize effects from toxins, simple and fast analytical monitoring methods are crucial. Here, the content of pigments and microcystins in 14 different strains of cyanobacteria cultured under different growth conditions was investigated to determine the influence of light and nutrient starvation on pigment/chlorophyll a (Chl a) ratios. The obtained pigment/Chl a ratios were applied in the CHEMTAX software to calculate the biomass of toxic cyanobacteria, as well as other phytoplankton groups. CHEMTAX ratios from the laboratory cultures were applied to water samples collected during four sampling periods at six fish farms in different reservoirs in São Paulo State, Brazil. Cyanobacteria generally dominated in all reservoirs in all sampling periods and constituted on average 44-66% of the average phytoplankton biomass. The concentrations of microcystins were significantly correlated to the Chl a concentrations of cyanobacteria and showed that the pigment method can be used to detect microcystins producing cyanobacteria in the Brazilian reservoirs. When the concentration of cyanobacteria in the reservoirs was above 4 µg Chl a l-1, microcystins were always detected. Our results show that pigment analysis can be used to provide fast and reliable results for the early warning of toxic cyanobacteria in freshwater reservoirs used for aquaculture, and pigment analyses were found to provide fast and reliable results regarding the presence of cyanobacteria and the risk of toxic cyanobacteria.