Polysaccharide Stalks in Didymosphenia geminata Diatom: Real World Applications and Strategies to Combat Its Spread

Didymosphenia geminata is a species of freshwater diatom that is known as invasive and is propagating quickly around the world. While invasive species are generally considered a nuisance, this paper attempts to find useful applications for D. geminata in the biomedical field and wastewater remediation. Here, we highlight the polysaccharide-based stalks of D. geminata that enable versatile potential applications and uses as a biopolymer, in drug delivery and wound healing, and as biocompatible scaffolding in cell adhesion and proliferation. Furthermore, this review focuses on how the polysaccharide nature of stalks and their metal-adsorption capacity allows them to have excellent wastewater remediation potential. This work also aims to assess the economic impact of D. geminata, as an invasive species, on its immediate environment. Potential government measures and legislation are recommended to prevent the spread of D. geminata, emphasizing the importance of education and collaboration between stakeholders.

Distribution of Didymosphenia, Gomphonema and Gomphosphenia diatoms (Bacillariophyta) in Turkish inland waters

In this study, a total of 53 taxa were identified from 13 catchments in Turkey. Gomphonema affine var. rhombicum E.Reichardt, G. angusticephalum E.Reichardt & Lange-Bertalot, G. calcifugum Lange-Bertalot & E.Reichardt, G. elegantissimum E.Reichardt & Lange-Bertalot, G. exilissimum (Grunow) Lange-Bertalot & E.Reichardt, G. graciledictum E.Reichardt, G. italicum var. densistriatum Levkov, Mitic-Kopanja & E.Reichardt, G. linearoides Levkov, G. megolobrebissonii D.A.Chudaev, Kociolek & M.A.Golobova, G. minusculum Krasske, G. minutum f. syriacum Lange-Bertalot & Reichardt, G. reediae Levkov, Mitic-Kopanja & E.Reichardt, G. sarcophagus W.Gregory, G. subcapitatum (Grunow) E.Reichardt & Levkov and Gomphosphenia holmquistii (Foged) Lange-Bertalot were recorded for the first time in Turkey. Of the identified taxa, Didymosphenia geminata (Lyngbye) M.Schmidt, Gomphonema acuminatum Ehrenberg, G. affine Kützing, G. angustatum (Kützing) Rabenhorst, G. augur Ehrenberg, G. micropus Kützing, G. minutum (C.Agardh) C.Agardh, G. olivaceum (Hornemann) Brébisson, G. parvulum (Kützing) Kützing and G. truncatum Ehrenberg are common in the waters. G. angustius E.Reichardt, G. insignaffine Reichardt, G. insigne W.Gregory, G. italicum Kützing, G. laticollum E.Reichardt, G. pumilum var. rigidum E.Reichardt & Lange-Bertalot, G. stonei E.Reichardt, G. supertergestinum E.Reichardt and G. vibrio Ehrenberg have been recently recorded from the Turkish waters. The genus Gomphosphenia in Turkey has so far been represented only by G. grovei (M.Schmidt) Lange-Bertalot.

Polyphenols Extracts From Didymosphenia Geminata (Lyngbye) Schmidt Altered the Motility and Viability of Daphnia Magna

The invasive diatom Didymosphenia geminata (Lyngbye) Schmidt, D. geminata has invaded the austral zone of Chile, causing significant ecological, scientific and societal concerns. We aimed to evaluate the viability and motility Daphnia magna (D. magna), as a biosensor for effects of D. geminata. Toxicity assays were performed in dilutions of river water alone (V/V dilution) and in river water contaminated with D. geminata (V/V dilution) or polyphenols extracted from D. geminata under controlled conditions and different time (acute 30 min and 7 hrs). Our results indicated that D. magna was sensitive to increasing concentrations of D. geminata extracts. We observed a 50% (IC50) viability reduction after 24 h of exposure to a 0.023 V/V dilution and the same value when using polyphenols from D. geminata; additionally, this treatment further reduced the motility capacity by 50% after 72 h. The D. magna organisms were acutely responsive, showing a 50% reduction in frequency at 15 min. We conclude that D. magna is sensitive to polyphenols produced by D. geminata in rivers, suggesting potential chronic toxic consequences on several aquatic species following exposure to these diatom substances.

Effects of a diatom ecosystem engineer (Didymosphenia geminata) on stream food webs: implications for native fishes

Stream habitat changes affecting primary consumers often indirectly impact secondary consumers such as fishes. Blooms of the benthic algae Didymosphenia geminata (Didymo) are known to affect stream macroinvertebrates, but the potential indirect trophic impacts on fish consumers are poorly understood. In streams of the Kootenai River basin, we quantified the diet, condition, and growth rate of species of trout, char, and sculpin. In 2018, macroinvertebrate taxa composition was different between a stream with Didymo and a stream without, but trout diets, energy demand, and growth rates were similar. Trout abundance was higher in the stream with Didymo, but the amount of drifting invertebrates was higher in the stream without. In 2019, we surveyed 28 streams with a gradient of coverage. Didymo abundance was correlated only with the percentage of aquatic invertebrates in trout diets and was not related to diets of char or sculpin or condition of any species. Thus, we found no evidence for a trophic link between Didymo blooms and the condition or growth of trout, char, or sculpin in mountainous headwater streams.

Valve morphology of Didymosphenia geminata (Bacillariophyceae) from Santa Cruz and Tierra del Fuego provinces, Patagonia, Argentina.

Background and aims: In 2013, blooms similar to those produced by Didymosphenia geminata (Lyngbye) M. Schmidt around the world, were detected in the Grande River basin, Tierra del Fuego province, and in 2014 in de las Vueltas River in Santa Cruz province. The aim of this paper is to analyze the valve morphology and morphometry of these materials to establish if they correspond to D. geminata or to other species of the genus that is producing the massive growth in southern Patagonia. M&M: Samples were collected at Grande River in 2013 and 2015 and, in de las Vueltas River in 2015 and 2016. Samples were analyzed with light and electron microscopy. For morphometric analyses 100 specimens from each sample were measured and statistical analyses were carried out using the R statistical package. Results: The studied populations have the same fine morphology described for other populations collected in Patagonia. Nevertheless, in some sampling sites from Santa Cruz province, we found a morphotype with a markedly smaller size, subcapitated poles, little marked constrictions of the poles, a broad central area (relative to cell size) and 1 to 3 stigmata, that was never reported in South America. Conclusions: The studied populations correspond to D. geminata ssp. geminata Metzeltin & Lange-Bertalot. From a morphological point of view the smaller morphotype present in Santa Cruz belongs to the same subspecies but can be easily misidentified during the routine monitoring programs carried out with light microscope due its size and valve outline.