Recovery of the algae and macroinvertebrate benthic community after Didymosphenia geminata mass growths in Spanish rivers

This study aims to assess the ecological profile of the invasive alga Didymosphenia geminata in NW Spain, analysing the biotic and abiotic factors related to the presence of massive colonies and their effect on river benthos. Physical and chemical parameters were measured in three infested rivers during 2009 and 2010, and biological samples of benthic community were taken according to standard protocols. Collected data was compared with that of control stations located in the same rivers but presenting no evident infestations. The autoecology shown by D. geminata in this study supports former observations reporting the expansion of its ecological niche, with current velocity and nutrients concentrations the environmental variables that best explain the establishment and development of mats in the studied rivers. Regarding its impact, it was observed that the mass growths of this diatom produced a dramatic change in the composition of the algae and macroinvertebrate benthic community which persisted after their disappearance. These results led to the development of a geostatistical predictive model to identify potential risk of dispersion of this diatom in Spanish rivers. The expected distribution of this algae according to this model agreed in general with the actual observed infestations, thus validating it as a tool to prevent and manage future infestations.