Environmental factors driving the dominance of the harmful bloom‐forming cyanobacteria Microcystis and Aphanocapsa in a tropical water supply reservoir

• Published in: Water environment research 2019-11, Vol.91 (11), p.1466-1478
• Main Authors: Magalhães, Aline A., Luz, Lafayette D., Aguiar Junior, Terencio R.
• Format: Article
• Language: English
• Subjects: Aluminium; Aluminum; Aphanocapsa; Blooms; Cyanobacteria; Dominance; Ecophysiology; Environmental factors; Environmental health; Environmental Monitoring; Eutrophic environments; Eutrophic waters; Eutrophication; Fresh Water; Generalized linear models; Hydrology; microcystin; Microcystis; Monitoring; Nutrients; Organic chemistry; Phosphorus; picocyanobacteria; Reservoirs; residence time; Retention time; Sediments; South America, Brazil; Statistical models; toxic blooms; Tropical climate; Tropical environment; Tropical environments; Water analysis; Water levels; Water sampling; Water stability; Water Supply; water‐level reduction
• ISSN: 1061-4303; 1554-7531
• DOI: 10.1002/wer.1141

Harmful cyanobacterial blooms in reservoirs have become a serious global issue for environmental health. However, dominance among different toxic cyanobacteria genera remains poorly understood, especially in tropical areas. We evaluated the influence of environmental factors, including total phosphorus, dissolved aluminum, water level, and precipitation on the change of the dominant genus from Microcystis to Aphanocapsa, in a hypereutrophic tropical reservoir, using 443 water samples over six years of field monitoring by applying generalized linear models (GLM). The results pointed out the prevalence of longer hydrologic retention time leading to enhanced water stability, and nutrients’ accumulation into the hypolimnetic zones of the reservoir may have favored the ecophysiological advantages for the picocyanobacteria Aphanocapsa, which reached densities greater than 1 million/ml. In addition, this article also suggests that physical–chemical remediation methods applied for immobilizing phosphorus in the sediments of the reservoir may be low effective in limiting cyanobacterial growth. These findings are not only meaningful to the understanding of the dynamics of cyanobacterial genera but also to improve the management of eutrophic reservoirs in tropical regions. Practitioner points We assessed cyanobacterial dominance changes based on 6‐year field monitoring. First article addressing the dominance of Aphanocapsa spp. in a tropical reservoir. Species of Aphanocapsa responded better to hydrological changes in the reservoir. The use of remediators was accompanied by an increase in cyanobacteria biomass. Under an optimal range of temperature and light along the year, the prevalence of lower water levels leading to longer water residence time and nutrients' accumulation into the hypolimnetic zones may have favored the dominance of Aphanocapsa over Microcystis in a tropical reservoir.