Session Title :

Reducing mercury bioaccumulation in reservoirs and other managed aquatic ecosystems

Synopsis :

With source control being of limited effectiveness in controlling mercury loading to aquatic ecosystems, more study is needed of in-system approaches to controlling mercury bioaccumulation. In this session, researchers from around the world will discuss manipulations of biogeochemical and ecosystem level processes in managed aquatic ecosystems to reduce mercury bioaccumulation.

Description :

The accumulation of mercury in aquatic food webs, and its subsequent uptake into humans via fish consumption, is a world-wide concern. The in-situ production of methylmercury within aquatic ecosystems, rather than aerial deposition or watershed runoff, is an important source of methylmercury in many reservoirs and other managed aquatic ecosystems. Many reservoirs, lakes and estuaries are highly managed to provide flood protection, support fisheries, and address toxic and unpalatable reduced compounds formed in anoxic bottom waters. A multitude of in-system management strategies have been developed. Aquatic ecosystems are commonly destratified, aerated with air, or oxygenated with pure oxygen gas, to improve oxygen content and repress the accumulation of reduced compounds in bottom water. The addition of nitrate salts to sediments has also been used to repress the accumulation of reduced compounds in bottom water. Biomanipulation involves manipulating fisheries to enhance populations of large- body zooplankton that consume phytoplankton, thereby enhancing water clarity. The addition of iron, aluminum, and calcium salts has also been used to enhance phosphorus retention in sediment, thereby lowering internal nutrient loading eutrophication. How these or other strategies could be used to manage the mercury cycle and repress mercury bioaccumulation in aquatic biota has yet to be comprehensively assessed.

Session Objective

The objective of this session is to bring together a wide range of experts to discuss results of applied studies aimed at reducing the formation of methylmercury and/or its uptake into the aquatic food web in reservoirs and other managed aquatic ecosystems. Presenters will include scientists, engineers, and resource managers from North America, Asia, and Europe. Presentations will focus on controllable aspects of biogeochemical processes, such as redox-related transformations at the sediment-water interface, and ecosystem level processes, such as productivity and food web structure, that affect methylmercury uptake into biota. Some studies have yielded unexpected and counterintuitive results. Exploring these complex connections between mercury cycling and reservoir management, this session will enhance our understanding of potential benefits and limitations of in-reservoir management strategies to reduce methylmercury bioaccumulation.

Importance to Conferees

This session will spur interest among presenters and attendees to work together across disciplines to connect fundamental aquatic ecology science with applied engineering and reservoir management practices. This linkage between science and management is a prerequisite to developing effective strategies to ameliorate the impacts of mercury contamination on lake wildlife and humans worldwide.