Effects of an hypersaline effluent from an abandoned potash mine on freshwater biofilm and diatom communities

Hypersaline mining effluents affect the structure and function of stream biofilm

“…Previous studies assessing the salinity effects on biofilms have indicated that values between 4 and 10 g L −1 can reduce algal biomass (Kefford et al, 2011;Rotter et al, 2013). Additionally, under short-term exposures to salinities of 15 g L −1 , we observed significant effects on the photosynthetic efficiency and nutrient uptake capacity of the biofilm together with a significant decline in diatom biodiversity (Vendrell-Puigmitja et al, 2021). Besides, catabolism-related functions of stream biofilm such as respiration and extracellular enzyme activities were also affected at salt concentrations above 0.25 g NaCl L −1 (Martínez et al, 2020a).…”

“…We reconstituted the ion composition of the real hypersaline mining effluent from Menteroda (Germany) abandoned potash mine to be used in the salt addition treatments. This mining effluent is characterised by high concentrations of dissolved inorganic ions: 78.2 g Na + L −1 , 6.70 g K + L −1 , 117 g Cl − L −1 and 1.21 g Mg 2+ L −1 (Vendrell-Puigmitja et al, 2021). We replicated the ionic composition and concentration of this effluent under laboratory conditions to obtain an effluent of 216 g L −1 of salinity (191 g L −1 NaCl, 12 g L −1 KCl, 12.5 g L −1 Cl 2 Mg•6H 2 O) that mimicked the concentration of the mining effluent, used as a stock solution.…”

“…Therefore, they are essential as a basal resource for in-stream food webs and key elements in the self-purification processes occurring in rivers and streams (Wu, 2016;Hall and Meyer, 1998;Power and Dietrich, 2002). Biofilm functionality and structure can respond to different environmental changes (Ponsatí et al, 2016;Pereda et al, 2019), including salinisation (Vendrell-Puigmitja et al, 2021). However, to date, only a few studies have examined salinity tolerance thresholds on biofilm communities (Underwood et al, 1998;Forster et al, 2006;Bolhuis et al, 2013;Cañedo-Argüelles et al, 2017) and changes on their functionality need to be further evaluated (Silva et al, 2000;Cook and Francoeur, 2013;Cochero et al, 2017;Martínez et al, 2020a).…”

Freshwater salinisation: a research agenda for a saltier world

“…Most of the currently available studies and datasets on FS come from North America, Australia, and Europe [5] (Figure 2), where strong impacts of salinisation occurred in the past [23,24] due to industrialisation and intensive agriculture. There, salinisation is still ongoing (e.g., abandoned mines [25], coal extraction [26]) even if current regulations have slowed it down in many cases [27]. In contrast, FS has been poorly studied in South America, Africa, and Asia (Figure 2), which is worrying as these are the continents where FS drivers are intensifying.…”

“…Community level FS impacts at community level have been intensively studied. However, the current literature mainly addresses community structure (e.g., species richness or composition [25,75,76]). Functional aspects related to trait diversity, food web structure, and trophic dynamics remain poorly explored.…”