Effects of freshwater salinization on a salt‐naïve planktonic eukaryote community

Abstract

Freshwater salinization is an increasing ecological and socioeconomic concern, with widespread evidence for increased salinity of inland waters associated with anthropogenic inputs and climate change. However, there remains an incomplete understanding of how increasing salinity of freshwater will alter the diversity and abundance of planktonic communities. We found that at salt concentrations relevant to U.S. and Canada water quality guidelines, the planktonic eukaryote community was highly simplified by the loss of almost all zooplankton and the loss of taxonomic diversity across planktonic groups, with only fungi and phytoplankton remaining at > 640 mg Cl À L À1 . Overall, our findings support that freshwater salinization can have devastating effects on the freshwater planktonic community in a lake without previous history of salt exposure, even at concentrations recommended by guidelines for water quality standards.

Limnology and Oceanography Bulletin Volume 32 Number 2 May 2023 41‐87

“…One of the real take-home messages for policy is that we really need to change what we're doing. Using an environmental DNA metabarcoding approach, we saw that the whole eukaryotic planktonic community, from phytoplankton to fungi to protozoans to zooplankton, shifted at a very low level of salt below the Canadian water quality guideline that is even lower than the US guideline (Astorg et al 2023).…”

Prioritizing taxa for genetic reference database development to advance inland water conservation

“…In addition, the genetic structure of metapopulations and metacommunities can be examined by tracking changes in COI haplotypes to reveal the relative importance of environmental selection (e.g., acidification) versus spatial and biogeographical landscape factors (Derry et al, 2009;Frisch et al, 2021;Martin et al, 2021). Combined with community metabarcoding of other markers (e.g., 18S rRNA gene or ITS), inferences of ecological responses to disturbance among taxa (COI + 18S rRNA gene: Astorg et al, 2022), and among genotypes or haplotypes within species (ITS2: Thibodeau et al, 2015;rbcL: Pérez-Burillo et al, 2021) can also be examined. Further, Petit-Marty et al (2021) found reduced intraspecific nucleotide diversity in long-lived animal species assessed as threatened by the International Union of Conservation of Nature (IUCN); COI barcodes also hold potential as an intraspecific tool for early assessment of species conservation status.…”

The ecosystem implications of road salt as a pollutant of freshwaters

“…However, a recent review provided some evidence that an SSD based on individuals and populations offers as much protection as an SSD based on community‐level experiments (Venâncio et al, 2022), indicating that laboratory‐based toxicity tests may adequately inform water quality guidelines. This review, however, did not capture recent community‐level field experiments that provide compelling evidence that current water quality guidelines do not adequately protect organisms in all lakes (Astorg et al, 2022; Greco et al, 2021; McClymont et al, 2022). A globally coordinated field experiment highlighted variation in community responses across a wide geographic region, with many communities being sensitive to salt at or below current water quality guidelines (Hébert et al, 2022; Hintz et al, 2022b).…”