Community signals of the effect of Didymosphenia geminata (Lyngbye) M. Schmidt on benthic diatom communities in Chilean rivers

Abstract

Background: Didymosphenia geminata (Lyngbye) M. Schmidt is a freshwater invasive benthic diatom native to oligotrophic systems of the Northern Hemisphere. Since 2010, freshwater systems of south-austral Chile, have experienced a progressive invasion of this species between 37°18′ S and 54°30′ S. This invaded area is characterized by biogeographic heterogeneity, anthropic pressure and lack of knowledge. The objective of this study was to analyze the effect of D. geminata on the community structure of benthic diatoms and the variability of this effect in Chilean rivers. Methods: The data were collected between 2010 and 2017 and pre-treated using fourth-root transformation to construct a Bray-Curtis similarity matrix and a Principal Coordinate Analysis to identify groups of sites. The α diversity and β diversity were estimated and compared using univariate indexes and the Mann-Whitney test, respectively. We used Permutational multivariate analyses of variance (PERMANOVA) and PERMDISP to estimate the spatial variation of communities, and an Analysis of Percentage Similarity (SIMPER) was performed to identify the species which contributed to the similarity between the groups of sites. Results: The results suggest significant differences between invaded and noninvaded rivers (54% of the total variation); the univariate indexes showed greater richness (S), greater diversity (H′), and less species turnover in invaded rivers. The PERMANOVA indicated significant interaction between D. geminata and the basins; there was also a significant effect on the internal dispersion in the basins. The SIMPER analysis showed that the groups composed exclusively of invaded sites had high mean similarity in all basins and small pedunculated benthic diatoms showed a significant response to the presence of D. geminata. Conclusion: We found high variability in the community structures, that determine a strong segregation between noninvaded and invaded sites by D. geminata, and that the main effect of D. geminata on diatoms benthic was the homogenization of the communities. This is reflected in the increase in density of small stalked diatoms and the reduction of species turnover among rivers in the same basin, leading to the loss of community heterogeneity that overcomes the spatial heterogeneity in the area invaded in Chile.

Didymo and Its Polysaccharide Stalks: Beneficial to the Environment or Not?

“…The authors did not observe species exclusion; however, it was observed that D. geminata is inclined towards a particular group of diatom species. This inclination can displace other diatom species and, therefore, cause different types of impacts, such as alterations in fluvial trophic webs [11].…”

Substratum‐associated microbiota

“…Reanalysis of the Puelo and Petrohue rivers in southern Chile confirmed the presence of mucilage‐producing forms of Didymosphenia from Peulo river and the presence of the genus in the Petrohue River, but without the production of mucilage masses likely due to the higher P levels of the latter system (Bravo et al, 2019). Diatoms assemblages from samples collected in rivers from south‐austral Chile from 2010 to 2017 contained higher numbers of small, pedunculate diatoms, and became more homogenized between basins in the presence of Didymosphenia , in contrast with the more variable assemblage structures of rivers without Didymosphenia (Salvo Pereira & Oyanedel Pérez, 2019).…”