Características ambientales, composición del fitoplancton y variación temporal de microcistina-LR disuelta en el embalse de As Forcadas (Galicia, NW España)

Abstract

Environmental characteristics, phytoplankton composition and temporal variation of dissolved microcystin-LR in As Forcadas reservoir (Galicia, NW Spain)Because of cyanobacteria can produce bioactive compounds and cyanotoxins their blooms are an environmental problem with serious implications for human and animal health. Among that, Microcystis aeruginosa is widely known because it may produce hepatotoxins called microcystins. In this work, we have studied the composition and dynamics of phytoplankton, the trophic state, the correlations of physicochemical parameters with dissolved microcystin-LR (MC -LR) concentrations and the bathymetric temporal variation of MC-LR in relation to the abundance of M. aeruginosa and temperature in As Forcadas reservoir (Valdoviño, A Coruña, Spain). Evidences of massive proliferation episodes of M. aeruginosa in As Forcadas have been recorded since 2006 (Cobo et al., 2012). We observed that the process of eutrophication in As Forcadas reservoir got worse in recent years and it is considered now as a reservoir with eutrophic characteristics. The results also indicated that temperature was one of the critical factors for M. aeruginosa development during the annual cycle. In addition, we observed that nutrients, especially ammonium, were favouring the development of this species. Finally, the highest concentration of MC-LR was observed at the bottom of the reservoir. These results show the importance of the knowledge of the annual cycle of the cyanobacteria and the bathymetric temporal variation of M. aeruginosa and its toxins.