Science Inventory

Trophic transfer efficiency in the Lake Superior food web: Assessing the impacts of non-native species

Citation:

Matthias, B., T. Hrabik, J. Hoffman, O. Gorman, M. Seider, M. Sierszen, M. Vinson, D. Yule, AND P. Yurista. Trophic transfer efficiency in the Lake Superior food web: Assessing the impacts of non-native species. JOURNAL OF GREAT LAKES RESEARCH. International Association for Great Lakes Research, Ann Arbor, MI, 47(4):1146-1158, (2021). https://doi.org/10.1016/j.jglr.2021.04.010

Impact/Purpose:

The Cooperative Science and Monitoring Initiative (CSMI), a bi-national science program under the Great Lakes Water Quality Agreement, provides a lakewide perspective on the ecological integrity of the Great Lakes. Ecosystem-based management relies on an understanding of how ecosystem structure and function changes as a result of perturbations, such as invasive species. However, data on unimpacted systems are scarce, therefore, we must rely on impacted systems to make inferences about ?‘natural states.’ Lake Superior is a unique case study to address the impacts of non-native species because the food web is dominated by native species. We developed an Ecopath with EcoSim model to investigate the effects of invasive species on the Lake Superior food web and found that invasive species have greater trophic efficiency than native species. Models such as those developed here offer valuable insight into the impact of invasive species on impacted systems, particularly by quantifying the cascading effect both up and down the food web.

Description:

Ecosystem-based management relies on understanding how perturbations influence ecosystem structure and function (e.g., invasive species, exploitation, abiotic changes). However, data on unimpacted systems are scarce; therefore, we often rely on impacted systems to make inferences about ‘natural states.’ Among the Laurentian Great Lakes, Lake Superior provides a unique case study to address non-native species impacts because the food web is dominated by native species. Additionally, Lake Superior is both vertically (benthic versus pelagic) and horizontally (nearshore versus offshore) structured by depth, providing an opportunity to compare the function of these sub-food webs. We developed an updated Lake Superior EcoPath model using data from the 2005/2006 lake-wide multi-agency surveys covering multiple trophic levels. We then compared trophic transfer efficiency (TTE) to previously published EcoPath models. Finally, we compared ecosystem function of the 2005/2006 ecosystem to that with non-native linkages removed and compared native versus non-native species-specific approximations of TTE and trophic flow. Lake Superior was relatively efficient (TTE = 0.14) compared to systems reported in a global review (average TTE = 0.09), and the microbial loop was highly efficient (TTE > 0.20). Non-native species represented a very small proportion (<0.01%) of total biomass and were generally more efficient and had higher trophic flow compared to native species. Our results provide valuable insight into the importance of the microbial loop and represent a baseline estimate of non-native species impacts on Lake Superior. Finally, this work is a starting point for further model development to predict future changes in the Lake Superior ecosystem.