Warming winters threaten peripheral Arctic charr populations of Europe

Abstract

As the global climate warms, the fate of lacustrine fish is of huge concern, especially given their sensitivity as ectotherms to changes in water temperature. The Arctic charr (Salvelinus alpinus L.) is a salmonid with a Holarctic distribution, with peripheral populations persisting at temperate latitudes, where it is found only in sufficiently cold, deep lakes. Thus, warmer temperatures in these habitats particularly during early life stages could have catastrophic consequences on population dynamics. Here, we combined lake temperature observations, a 1-D hydrodynamic model, and a multi-decadal climate reanalysis to show coherence in warming winter water temperatures in four European charr lakes near the southernmost limit of the species’ distribution. Current maximum and mean winter temperatures are on average ~ 1 °C warmer compared to early the 1980s, and temperatures of 8.5 °C, adverse for high charr egg survival, have frequently been exceeded in recent winters. Simulations of winter lake temperatures toward century-end showed that these warming trends will continue, with further increases of 3–4 °C projected. An additional 324 total accumulated degree-days during winter is projected on average across lakes, which could impair egg quality and viability. We suggest that the perpetuating winter warming trends shown here will imperil the future status of these lakes as charr refugia and generally do not augur well for the fate of coldwater-adapted lake fish in a warming climate.

Lakes in Hot Water: The Impacts of a Changing Climate on Aquatic Ecosystems

“…For example, egg survival of Arctic charr ( Salvelinus alpinus ) is limited by warming winter water temperatures, which already exceed tolerance temperatures in some European lakes (Kelly et al. 2020 ). Warming water temperatures and low oxygen concentrations at depth can also reduce the ecological niche dimensions of many fishes.…”

“…Although this may be construed to be a positive consequence of climate change for local communities that now have a new food source, the question remains as to how these range expansions will affect native fish populations, such as the Arctic charr, a species already stressed by climate warming (Kelly et al. 2020 ).…”

LéXPLORE: A floating laboratory on Lake Geneva offering unique lake research opportunities

“…; Lynch et al, 2015; Straile et al, 2007) and Arctic charr ( Salvelinus alpinus ; Caudron et al, 2014). However, these species now face additional threats from increasing temperatures, modified riverine flows and changing wind patterns during critical development phases (Kelly et al, 2020; Mari et al, 2021; Nõges et al, 2018). Core datasets (Box 3; Appendix S1) and plankton studies (Section 3.5) from LéXPLORE will support investigations on the temporal coupling between the emergence of fish larvae and the phenology of plankton, or the risk of so‐called match–mismatch phenomena (Cushing, 1990).…”

Sentinel responses of Arctic freshwater systems to climate: linkages, evidence, and a roadmap for future research

“…For example, at Lake Windermere in northwest England, Arctic char appear to have changed their migration patterns to avoid hypoxic oxygen levels (Jones et al 2008). Modeling of water temperatures suggests that European populations of Arctic char are highly vulnerable to climate warming (Kelly et al 2020).…”