LEMN Workshop 4.4 - "Lake Erie Land and Water - Clarifying the Urban - Eutrophication Linkage" was a binational workshop that was held at the Stoneridge Inn, London, Ontario on March 23rd 2010. This workshop was sponsored by the Ontario Great Lakes Program of Ontario Ministry of Agriculture, Food and Rural Affairs.

Workshop Resources

Workshop Purpose

Aquatic researchers have a series of explanations for the behaviour of nutrients that enter Lake Erie; for example the links between nutrients, Dreissenid mussels, and harmful algal blooms.

We also know that nutrients arrive in the lake via storm events. However, we lack an in-depth understanding of the key types and the regulators of nutrients and the transformations they undergo on the landscape.

We will look to workshop participants’ expertise to help us determine the relative importance of different agricultural practices and the effectiveness of management practices in regulating nutrient loads.

A key task of the workshop will be for participants to generate flow charts that summarize their understanding of the key sources and links; and identify the most important research needs.

The resulting information will be integrated into a lakewide 'conceptual map' that adds the roles of land-based activities to our picture of the eutrophication process in Lake Erie.

We hope that the research needs can result in future opportunities for collaborative projects.

The findings will also be especially useful for informing the Canadian and US teams negotiating revisions to the Great Lakes Water Quality Agreement.

Workshop Background

Recent manifestations of eutrophication in Lake Erie have become increasingly prevalent, despite evidence that total phosphorus loadings are at or near target levels that previously were deemed adequate to prevent appearance of nuisance algae, hazardous algal blooms and other manifestations. Findings of various task groups and symposia suggest that changes in the form rather than just the quantity of phosphorus may be responsible.

Potential sources have been related to agricultural practices, increasing discharge from urban centres, and/or transformations or altered cycling by in-lake processes. In February 2009, the Water Quality Board of the IJC and LEMN convened a workshop to assess the weight of evidence supporting each hypothesis: www.ijc.org/en/priorities/2009/reports/2009-eutrophication.pdf

Possible causes and ultimate endpoints were summarized by participants in a series of flow charts (fuzzy cognitive maps (FCMs) designed to graphically represent understanding and uncertainties about the processes. Agricultural activities appeared to be a key external driver of the reappearance of eutrophication, and likely play an especially important in the Lake Erie ecosystem. Furthermore, practices related to agriculture are likely more amenable to 'no regrets' management actions than other possible causes of the eutrophication issue.

This workshop will further develop our understanding of the causes and consequences of the reappearance of eutrophication emphasizing the role of agricultural activities in Lake Erie. The goal is to develop a detailed fuzzy cognitive map that focuses on the agriculture-related, land-based pathways and variables that have the potential to influence eutrophication in Lake Erie.

Workshop Tasks

• Review key concepts and links between agriculture and Lake Erie eutrophication as developed in 2 previous workshops;
• Refine existing fuzzy conceptual maps to reflect complexity and assess understanding of the agricultural processes;
• Compile consensus-based composite map reflecting best available knowledge of agricultural & soil science;
• Assess evidence for key pathways and their responsiveness to implementation of ‘no regrets’ management actions to mitigate agricultural influences on eutrophication in Lake Erie.