Work package 3

This work package is led by Amanda Poste and aims to identify key environmental determinants of exposure, uptake and food web transfer of MeHg and predict risk for MeHg exposure in fish in response to environmental change. The work package focuses on the processes that govern how Hg concentrations in water translate into Hg concentrations in aquatic biota, including predatory fish. In particular, we will investigate MeHg uptake at the base of the food web and trophic transfer through consumer trophic levels with a strong focus on the role of food web structure and trophic interactions.

Modelling tools (statistical, Bayesian, mechanistic) for characterizing Hg accumulation and food web transfer will be tested using field data from work package 2 and 3, and further developed to improve our ability to model Hg in boreal aquatic food webs. Comparisons with existing data and ongoing work (Kidd lab, UNB) will also support model development and identification of key drivers. These refined tools will be used to integrate the results all WPs and to estimate perform a risk assessment of MeHg exposure in fish, relevant to ecosystem function (fish reproduction and health), under changing environmental conditions.

The work package will include the following specific tasks

• Collection of field data to document and describe lake food web structure and Hg trophodynamics, with a particular focus on the lower food web;
• Investigate the importance of several environmental factors in driving changes in uptake of Hg at the base of the food web and transfer through trophic levels;
• Explain the variation and patterns in food web accumulation of Hg in boreal lakes in relation to lake and catchment characteristics, deposition and climate;
• Assess present and future MeHg ecosystem risk with a focus on future environmental change.