Experimental setup at Barrier Lake Field Station (C Loewen @Loewen_Ecology)
For decades, the management of Canada’s mountain lakes prioritized fish stocking to create angling opportunities and promote tourism. Although stocking programs have ended in most protected areas – replaced by a renewed focus on preserving natural ecosystems – the legacy of this historical practice continues, as non-native sportfish remain a prominent feature of our mountain waters. These alien predators are considered invasive because of their impacts on native species. For instance, introduced rainbow trout often compete or hybridize with native fish and affect fishless lake communities by preying on invertebrates and boosting algae growth; however, it is uncertain how these impacts might vary with climate change.
Biodiversity can be considered a form of “biological insurance” for impacted communities, because as environmental conditions change, the productivity of tolerant species may increase to offset losses by more vulnerable species. In alpine lakes, harsh environmental conditions limit the number of zooplankton occurring locally; however, these tiny organisms have evolved to travel long distances by wind or hitching a ride with passing waterfowl. As a result, even alpine lakes with low local biodiversity might be buffered against invasion impacts by the arrival of stress tolerant species from neighbouring lakes.
To test the effects of rainbow trout predation on zooplankton from previously fishless alpine lakes, and how these effects might differ with climate warming or the arrival of species from other nearby lakes, researchers from the University of Alberta conducted an experiment using live organisms in a series of large tanks at the University of Calgary’s Barrier Lake Field Station. They found that fish eliminated certain zooplankton species and reduced the overall productivity of the alpine community. However, the introduction of zooplankton from lower elevations rescued the community by providing species with specific physical traits that made them tolerant to fish predation. Results were unaffected by warming treatments. This study shows that, although alpine zooplankton communities are inherently sensitive to invasive fish, the arrival of regional species can reduce the impacts of invasion and help to maintain ecosystem functioning in the face of environmental change.
This is a summary article authored by Charlie Loewen. For further information, please see the original published research:
Charlie J.G. Loewen & Rolf D. Vinebrooke (2016) Regional diversity reverses the negative impacts of an alien predator on local species-poor communities. Ecology, 97:2740–2749 (doi:10.1002/ecy.1485).