Assessing the occurrence of cyanobacterial blooms in a large Brazilian reservoir using satellite remote sensing

In the last decades many large reservoirs, such as Furnas Reservoir, were built in southeastern Brazil to provide sufficient power supply to the region. External nutrient inputs from agriculture and domestic sewage, however, caused an increase of eutrophication in these systems and, consequently, an increase in cyanobacterial blooms. Blooms of cyanobacteria are associated with several problems in water quality such as dissolved oxygen depletion, taste and odor, and unsafe drinking water due to the presence of cianotoxins (CARMICHAEL 2001, VINCENT et al. 2004). In Furnas Reservoir, cyanobacterial dominance or blooms may occur throughout the year. Several potential toxic species were observed, including Cylindrospermopsis Lyngbya hieronymusii, Microcystis aeruginosa, M. novaceckii, M. panniformis, M. protocystis. Planktothrix planctonica, Radiocystis fernandoi, and Sphaerocavum brasiliensis. Because some reservoirs are also used as drinking water sources, cyanobacterial potential toxicity can Le a threat for human health, and early detection of blooms is an important asset. Orbital remote sensing can provide a tool for rapid detection and quantification of blooms because it allows monitoring large areas, such as an entire aquatic system, inside a short temporal scale (THIEMANN & KAUFMANN 2000, KUTSER 2004). Algorithms have been developed for aquatic systems monitoring. Some programs like Sea-viewing Wide Field-of-view Sensor (SeaWIFS) were established in the ocean, and they showed the potential use of remote sensing for aquatic environment studies (e.g., GREGG & CONKRIGHT 2002).