Effect of Didymosphenia geminatacoverage on the phytobenthic community in an Andean basin of Chile

The invasive diatom Didymosphenia geminata(Lyngbye) M. Schmidt has received considerable attention in recent years due to its rapid geographic expansion and massive proliferation, which have altered habitat availability for benthic species and triggered negative effects on stream ecosystems. We evaluated the changes in the community structure of phytobenthos caused by the temporal variation in D. geminatacoverage, in addition to the environmental variables correlated with the temporal variation of this invasive microalga in the Andean sector of the Biobio River basin, Chile. Environmental parameters were measured during the austral summer of 2014–2015, when phytobenthos samples were collected and used to develop a relative abundance matrix of taxa by calculating species richness and Shannon diversity. Multivariate techniques were used to establish the relationships among environmental variables, including D. geminatacoverage, and the phytobenthic community. Massive proliferation of D. geminataoccurs during summer (December–January). According to multiple regression analysis, electrical conductivity, temperature and total phosphorus were the variables that best explained the variation in D. geminatacoverage. When D. geminatacoverage was over 50%, phytobenthic species richness was significantly higher than at the uninvaded site, without a significant change in Shannon diversity. In addition, the % coverage of this invasive microalga and total phosphorus concentration were variables that differentiated phytobenthic communities among the study sites. Environmental factors such as conductivity, temperature and total phosphorus concentration influenced the temporal variability of D. geminatamats. In addition, the massive growth of this invasive diatom caused a higher species richness without altering Shannon diversity. Our results suggest that the spatio-temporal variability of D. geminatacorrelated with environmental variables will help predict the habitat suitability of this alga in other Andean rivers and allow a better understanding of ecological habitat alterations.