Climate warming and projected loss of thermal habitat volume in lake populations of brook trout

Abstract

We applied an ensemble of climate warming models to an iconic protected landscape (Algonquin Park, Ontario) and the seasonal temperature profile model for lakes to assess changes in brook trout ( Salvelinus fontinalis) thermal habitat volume (THV) among lakes of different sizes in 30-year periods under two climate warming scenarios (RCP 4.5 and 8.5). Bayesian beta regression models show that lake size (surface area) and morphometry (dynamic lake ratio) are important factors in THV loss. THV loss increases as a function of the dynamic lake ratio (transition from bowl-shaped to dish-shaped lakes). The magnitude of this effect depends on the lake size category and the RCP scenario. Small (<100 ha) and medium (100–500 ha) dish-shaped lakes are projected to have greater THV loss in 2071–2100 (60%–100% of brook trout THV under RCP 8.5; 40%–70% under RCP 4.5) than large lakes (>500 ha) of similar shape. Climate warming projections for the balance of this century, regardless of the RCP category, will result in the loss of brook trout THV in lakes that range widely in size and morphometry.