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Does food web structure modify the resilience of shallow lakes to harmful algal blooms?
YEAR: 2020

Problem: Shallow lakes are the most common inland waterbody and are highly susceptible to eutrophication which often leads to frequent and severe harmful algal blooms (HABs). HABs contain toxin-producing cyanobacteria, cause poor drinking water quality, and contribute to fish kills. Furthermore, more frequent HABs have been linked to increased greenhouse gas (GHG) emissions. Therefore, reducing HABs in shallow lakes is a priority for lake managers. However, restoration is often slow or unsuccessful due to a host of physical and biological barriers. Food web manipulation has had success improving water quality, but it is often only a short-term solution. Food web structure, and its underlying stability, has been linked to ecosystem resilience to perturbation in a large body of theoretical literature. Additionally, there is evidence that food web structure can also regulate GHG flux. Therefore, greater ecosystem resilience can reduce the frequency of HABs, decrease GHG flux, sustain more nutrient loading, and allow faster recovery from dangerous algal blooms.

Objectives: The objectives of our proposed research are two-fold: (1) Determine the empirical relationship between food web structure and ecosystem resilience and (2) assess how food web structure affects GHG flux.

Methods: To meet our objectives we propose a manipulation experiment using six large ponds to test the effect three food web structures have on ecosystem resilience to a one-time nutrient pulse, similar to a large storm event. We will establish three different food webs with varying levels of complexity and interaction strength, replicated in two ponds each. This will allow us to mechanistically assess how food web structure influences ecosystem resilience and GHG flux.

Outcomes: The outcomes of this project will further our understanding of how food web structure mediates disturbances in shallow lakes. This knowledge is crucial for managers in order to implement more successful lake restoration programs. This is because understanding the influence of food web structure on ecosystem resilience can inform strategies that could engineer more resilient ecosystems, thereby increasing restoration success.

Read the research findings here.