Changes in water quality related to permafrost thaw may significantly impact zooplankton in small Arctic lakes

Abstract

Rising temperatures are leading to permafrost thaw over vast areas of the northern hemisphere. In the Canadian Arctic, permafrost degradation is causing significant changes in surface water quality due to the release of solutes that can alter conductivity, water clarity, and nutrient levels. For this study, we examined how changes in water quality associated with permafrost thaw might impact zooplankton, a group of organisms that play an important role in the food web of Arctic lakes. We conducted a biological and water quality survey of 37 lakes in the Mackenzie Delta region of Canada's Northwest Territories. We then used this data set to develop models linking variation in the abundance, diversity, and evenness of zooplankton communities to physicochemical, biological, and spatial variables. Subsequently, we used these models to predict how zooplankton communities might respond as water quality is altered by permafrost thaw. Our models explained 47%, 68%, and 69% of the variation in zooplankton abundance, diversity, and evenness, respectively. Importantly, the most parsimonious models always included variables affected by permafrost thaw, such as calcium and conductivity. Predictions based on our models suggest significant increases in zooplankton abundance (1.6-3.6 fold) and decreases in diversity (1.2-1.7 fold) and evenness (1.1-1.4 fold) in response to water quality changes associated with permafrost thaw. These changes are in line with those described for significant perturbations such as eutrophication, acidification, and the introduction of exotic species such as the spiny water flea (Bythotrephes). Given their important role in aquatic food webs, we expect these changes in zooplankton communities will have ramifications for organisms at higher (fish) and lower (phytoplankton) trophic positions in Arctic lakes.

Effects of increased temperature on arctic slimy sculpin Cottus cognatus is mediated by food availability: Implications for climate change

“…Consumption is temperature‐dependent in fishes and whether increases in temperature within the habitable thermal limits of a species will be beneficial or detrimental to fish production will ultimately depend on how food resources respond (Hill & Magnuson, 1990; Kitchell et al., 1977). Generally, aquatic ecosystems in the Arctic are predicted to become more productive with future warming (Levine & Whalen, 2001; Prowse et al., 2006; Vucic et al., 2020). For instance, zooplankton biomass is expected to increase in arctic lakes with increases in temperature and longer ice‐free periods (Klobucar et al., 2018), and these predicted increases fall within the range of increased consumptive demand predicted for fish species, such as Arctic char (Budy & Luecke, 2014).…”

Drivers of fish biodiversity in a rapidly changing permafrost landscape

“…Full sampling details have been described previously in Vucic et al. (2020) and Cohen et al (2021). Briefly, we obtained lake bathymetry data using a Humminbird® Helix 5 chart plotter (Johnson Outdoors Marine Electronics, Inc.) and Reefmaster bathymetry software (Reefmaster Ltd.).…”

“…Climate warming and increasing human development are contributing to widespread permafrost degradation in circumpolar regions, with potentially significant consequences for freshwater biodiversity including fish (Raynolds et al., 2014; Segal, Lantz, & Kokelj, 2016b; Thienpont et al., 2013; van der Sluijs et al., 2018; Vucic et al., 2020). Impacts to permafrost through active layer deepening and thermokarst (i.e., melting of ground ice) processes are leading to impacts on fish habitat quantity and quality including increased dissolved organic carbon and nutrient delivery to lakes, and altered catchment drainage patterns (Nitze et al., 2020; Vonk et al., 2015; Wauthy et al., 2018; Wrona et al., 2013).…”

“…We selected the lower Mackenzie River basin as our study area, an ice‐rich permafrost region that is experiencing considerable environmental change including rapid warming, widespread permafrost thaw, and new major highway development (Burn & Kokelj, 2009; Tyson, Lantz, & Ban, 2016). Although there have been several previous studies examining lake water quality and lower trophic levels within the context of environmental change in the Mackenzie Delta region (e.g., Cohen et al, 2021; Houben et al., 2016; Kokelj et al., 2005; Thienpont et al., 2013; Vucic et al., 2020; Zhu et al., 2019), comparable work examining lake fishes remains a substantial data gap here and in other ice‐rich permafrost regions worldwide (Heino et al., 2020; Laske et al., 2016; Raynolds et al., 2014). The importance of understanding changing fish biodiversity is echoed by Indigenous knowledge holders across the circumpolar north who have reported observations of environmental change directly relevant for their food security and cultural identity (Knopp et al., 2020).…”

Abundant and rare bacterial taxa structuring differently in sediment and water in thermokarst lakes in the Yellow River Source area, Qinghai-Tibet Plateau

“…In cold region, thermokarst lakes are especially important due to their huge abundance (Polishchuk et al, 2017), massive storage of water, carbon, and nutrients (Reyes and Lougheed, 2015), as well as their enormous contributions of greenhouse gases (Walter et al, 2006; Serikova et al, 2019; In’T Zandt et al, 2020). Although immense amounts of microbial research have been conducted in thermokarst lakes, overwhelming majority of which focused on surface water (TRANVIK, 1989; Shirokova et al, 2013; Vucic et al, 2020) rather than sediment or both. However, the differences and linkages between sediment and water in thermokarst lakes are remain largely unknow.…”