Drivers of fish biodiversity in a rapidly changing permafrost landscape

Abstract

Rapid environmental change occurring in northern permafrost regions may have profound implications for fish biodiversity but remains poorly understood. Climate change, increasing human development, and resultant permafrost thaw may combine to alter the quality and quantity of fish habitat including reductions in preferred thermal habitat, changes in water quality, and modified drainage patterns. Our study objective was to understand how lake fish communities residing on permafrost landscapes may be responding to climate change and land use disturbance. We investigated the drivers of freshwater fish community health in lakes of the lower Mackenzie River basin, an ice‐rich permafrost region that is experiencing substantial warming, permafrost thaw, and new major highway development. We collected lake morphometry, water quality, and fish community data from 50 lakes and derived several indicators of aquatic health including fish species richness, relative abundance, and the occurrence of three culturally important fish species. We found that water quality and lake size were significant co‐drivers of fish community health whereas relationships with summer thermal habitat, as represented by July air temperature, were relatively negligible. Dissolved organic carbon (an indicator for lake browning) emerged as a particularly important driver of fish community structure, and fish community health steeply declined when dissolved organic carbon concentrations exceeded 17–18 mg/L. We suggest potential mechanisms for these declines including light inhibition during summer and a reduced capacity for overwintering in smaller and murkier lakes that may experience faster oxygen depletion rates. Using a more expansive regional water quality database of 203 lakes, we observed potential supporting evidence that warming and new road development increased dissolved organic carbon and total phosphorus concentrations, possibly reducing fish habitat quality in this region. Together, these results highlight how fishes relying on the numerous small and shallow lakes that dominate permafrost landscapes may be vulnerable to the combined effects of rapid warming and new infrastructure.

Browning of boreal lakes: Do public perceptions and governance align with the biological foundations?

“…Reduced photosynthesis also affects zooplankton community composition (Lehtovaara et al, 2014; Nicolle et al, 2012; Williamson et al, 2015). Darkening reduces the availability of euphotic benthic habitats for aquatic plants and periphyton (Couture et al, 2015) and often reduces fish biomass, fish production, and fish species diversity (Karlsson et al, 2009; Murdoch et al, 2021; Rahel, 1984; Rask et al, 1999). Decreased visibility weakens the foraging efficiency of visually hunting fish and modifies predator–prey interactions (Hedström et al, 2017; Ranåker et al, 2012; Santonja et al, 2017; Scharnweber et al, 2016).…”

The Color of Earth’s Lakes

“…Globally, our results suggest that climate change may decrease the percentage of blue lakes. Shifts in lake modal color from blue to green or brown, and vice versa, likely represent a substantial change in ecosystem structure and function (e.g., Hayden et al., 2019; Murdoch et al., 2021; Topp, Pavelsky, Dugan, et al., 2021; Topp, Pavelsky, Stanley, et al., 2021). The nature and mechanisms of these trajectories of change are unknown, and cross‐scale interactions between climate change and local controls may lead to nonlinear dynamics and tipping points in lake ecosystems.…”

Arctic roads and railways: social and environmental consequences of transport infrastructure in the circumpolar North

“…While culverts were built to mitigate disturbances to aquatic species, construction irreversibly altered their habitat, just as it did for terrestrial species like caribou and fox. There is some evidence following the ITH construction of phosphorus enrichment occurring in nearby adjacent lakes, and a potential reduction in fish habitat quality that is also being influenced by climate change impacts on water chemistry (Murdoch et al 2021). Every passing vehicle also presents a risk by generating dust that is dispersed onto tundra, altering the substrate and reducing vegetation cover (see above for examples elsewhere).…”