A freshwater predator hit twice by the effects of warming across trophic levels.

Tomas Jonsson,Malin Setzer

doi:10.1038/ncomms6992

Abstract

Many ecological responses to climate change have been documented. However, due to indirect effects, some responses can be complex and difficult to predict. For example, our understanding of effects on consumers involving responses on several trophic levels is limited. Here, combining the knowledge of trophic interactions in the EU's fourth largest lake with long-term climate and catch data, we analyse potential drivers of change in this system's apex predator. We show that warm winters correlate with later poor catches of great Arctic charr (Salvelinus umbla), and that in recent years predator-prey cycles involving this species have disappeared. The likely mechanisms are trophic mismatches directly and indirectly affecting two stages of charr, the fry and the juveniles, respectively. Our study illustrates how a long-lived consumer may be subjected to double jeopardy from the effects of warming across trophic levels, and that a food web approach can aid in disentangling the chain of mechanisms responsible.

Highlights

Many ecological responses to climate change have been documented
We know of no example of indirect effects of climate change on an apex predator in a freshwater system where the mechanisms operating across trophic levels have been analysed
A pressing issue is how populations that already are endangered, due to other anthropogenic stressors, will respond to a combination of direct and indirect effects of climate change and how their management may need to be adjusted[32]. This is true for many aquatic species that may have less potential for dispersal in response to a changing climate. We address these issues by analysing the climate effects on an endangered[33] stock of Arctic charr—the apex predator in the second largest lake in Sweden (Lake Vattern, Supplementary Fig. 1)—to study the effects of warming across multiple trophic levels and be able to discuss implications of this for future climate change effects on the population

Summary

Introduction

Many ecological responses to climate change have been documented. due to indirect effects, some responses can be complex and difficult to predict. This is true for many aquatic species that may have less potential for dispersal in response to a changing climate (when compared with many marine or terrestrial species) We address these issues by analysing the climate effects on an endangered[33] stock of Arctic charr (great Arctic charr; Salvelinus umbla)—the apex predator in the second largest lake in Sweden (Lake Vattern, Supplementary Fig. 1)—to study the effects of warming across multiple trophic levels and be able to discuss implications of this for future climate change effects on the population. Disentangling the possibly complex mechanisms driving the effects of warming on a population hinges on the identification of critical stages in the life cycle and knowledge of important interactions with other species and how these may be affected by climate This analysis is aided by a good understanding of the trophic interactions in the pelagic food web of Lake Vattern and the ontogenetic niche shifts in its apex predator (Fig. 1). Using a combination of data on commercial catches, and environmental data, we analyse whether warming has affected three potentially

Methods

Results

Conclusion