Multiple species drive flexible lake food webs with warming

Abstract

Climate change is rewiring the food webs that determine the fate of diverse ecosystems. Mobile generalist consumers are responding to climate change by rapidly shifting their behaviour and foraging, driving food webs to flex. Although these responsive generalists form a key stabilizing module in food web structure, the extent to which they are present throughout whole food webs is largely unknown. Here, we show that multiple species comprising key trophic roles drive flexible lake food webs with warming. By examining lakes that span a 7°C air temperature gradient, we found significant reductions in nearshore derived carbon and nearshore habitat use with increased temperature in three of four fish species. We also found evidence that the response of lake trout to increased temperatures may reduce their biomass and cascade to release their preferred prey, the pelagic forage fish cisco. Our results suggest that climate warming will shift lake food webs toward increased reliance on offshore habitats and resources. We argue that species across trophic levels broadly couple lake macrohabitats, suggesting that potentially stabilizing responsive consumers are present throughout food webs. However, climate change appears to limit their ability to responsively forage, critically undermining a repeated stabilizing mechanism in food webs.

Thermal preference influences depth use but not biomass of predatory fishes in response to lake morphometry

“…In response, the cold-adapted top predator lake trout responds by retreating to the offshore to forage and at most accessing nearshore resources in quick forays (Guzzo et al 2017b, Cruz-Font et al 2019). Other cold-water fishes exhibit similar responses across natural gradients in lake temperature (Bartley et al in press, 2018, Tunney et al 2014), suggesting that thermal accessibility may be limiting for many species. Various morphometric factors appear to influence the accessibility of the nearshore in lakes.…”

The effect of climate change on Galaxias maculatus thermal habitat availability in northern Andean Patagonian lakes

“…Understanding the thermal response of species to global climate change (GCC) is crucial to predicting their fate in the future and informing conservation management (Bozinovic et al., 2011; Vázquez et al., 2017). Furthermore, since effects on key species in trophic webs may cascade throughout entire ecosystems (Bartley et al., 2018; Pörtner & Peck, 2010), understanding the biological and/or ecological response of such species to increasing temperatures (due to GCC) is central to understanding possible consequences at ecosystem level.…”