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

Abstract

Background: 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. geminata coverage, 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. Methods: 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. geminata coverage, and the phytobenthic community. Results: Massive proliferation of D. geminata occurs 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. geminata coverage. When D. geminata coverage 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. Conclusions: Environmental factors such as conductivity, temperature and total phosphorus concentration influenced the temporal variability of D. geminata mats. 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. geminata correlated 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.

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

“…This inverse pattern has been observed in other systems affected by biological invasions, in which the invaders induce responses that varies with the spatial scale [15,26], and may be indicates that broad scale was more appropriately to examined the effects of D. geminata on the communities [10]. The high species richness and diversity associated to local changes in invaded rivers are similar to that described at local scales for rivers of New Zealand [24] and in the high zone of the Biobío River Basin in Chile [21]. Increased diversity may be related to the mucilagenous stalks of D. geminata that offer a habitat for small species of stalked diatoms to settle and increase their density, even surpassing that of D. geminata and of other native species [22].…”

Substratum‐associated microbiota

“…Thick mats of Didymo can alter the ecology of organisms around and within the mat. Electrical conductivity, temperature, and total P best explained temporal variation in Didymo coverage in the Andean sector of the Biobio River Basin, Chile, over the austral summer of 2014-2015 (Figueroa et al, 2018). Phytobenthic species richness was significantly higher at sites with >50% coverage than at uninvaded sites.…”

Polyphenols extracts from Didymosphenia geminata (Lyngbye) Schmidt altered the motility and viability of Daphnia magna

“…The most commonly, described D. geminata impacts are physicochemical changes in the watercourses in oligotrophic locations, including substantial increases in algal biomass, the retention of ne sediment, and benthic hydrodynamic alterations, which consequently affect biogeochemical states and processes such as redox conditions, pH and nutrient cycling in the benthic layer (Reid et al 2012). Other impacts are described in the periphyton biomass and benthic communities, showing higher tolerant invertebrate groups densities such as Oligochaeta Chironomidae, Cladocera and Nematoda, Orthocladiinae and also non-insect taxa (Brand and Grech 2020; Kilroy et al 2009) The toxic impacts of this microalgae start with the alteration of microenvironments and microalgal communities according to the seasonal variations of D. geminata (Chester and Norris 2006;Figueroa et al 2018) and the possibility of these microalgae spreading to new bodies of water (Montecino et D. geminata toxicological potential to affect other organisms remains unknown. Moreover, this pennate microalgae is rich in antioxidants such as polyphenols and pigments as diadinoxanthin (Lohr and Wilhelm 1999), which was also reported as D. geminata polyphenol toxicity on two salmonids species cell lines (Olivares-Ferretti et al 2019) and Salmo salar spermatozoa activation times (Olivares et al 2015).…”