News

April 1, 2017

Great Lakes Water Levels

Michael Twiss

In the late 1950s Canada and the United States undertook a massive infrastructure development on the St. Lawrence River by damming the river between Massena, NY, and Cornwall, ON thereby harnessing a great hydroelectric power potential. The dammed river allowed for the creation of a larger system of locks, which permitted ocean-going vessels to access the entire Great Lakes region. However, from an ecological view point the dam created more stable yet unnatural water levels that protected shoreline development but also reduced biodiversity in the river wetlands as cattails, stimulated by the high nutrient levels of the day and stabilized by little water level variation, spread as deep into the river as they could grow and similarly inland.

In December 2016, Plan 2014, the new water level regulation plan for the St. Lawrence River & Lake Ontario was approved. Yes! - a 29% reduction in wetlands that have choked submerged aquatic vegetation and reduced wetland meadow on the river banks will result so we can expect more fish production and a more natural ecosystem in the future and that is good. However, based on previous studies, repeated wetting and drying of wetlands that will reduce their extent (expected under Plan 2014) can enhance the flux of methylmercury from these systems due to the stimulation of ‘sulfate-reducing bacteria’ (these microbes live wherever there is sulfate, just like you’ll eventually find mold wherever there is bread). Methylmercury is the form of mercury that accumulates in fish and organisms like us that consume fish. Wetlands, known for water purification services, retain contaminants. Unfortunately, the stable wetlands that established along the shore of the St. Lawrence River in the past 59 years occurred at a time when atmospheric Hg and sulfate deposition were very high in this region (due to coal combustion in the mid-west), thus a legacy of contamination exists that must be managed. Research in 2016 supported by New York Sea Grant estimates that 74 tons of mercury will be released into the river from the loss of these wetlands. Although twenty million dollars were spent to examine the impacts of creating a more natural water level management plan for the river no consideration was made for the impact of water levels on ‘biogeochemistry’ - the nexus of chemicals, geology, and the organisms that alter the fate of these chemicals in the environment. Therefore, there is a real risk that the new water level regulation plan designed to create more fish habitat will do so at the cost that fish may become more Hg contaminated. It follows that we must know how fast the mercury will be lost from the wetlands and where will it go. We can manage mercury contaminated fish with effective NYSDEC fish consumption guidelines while the mercury dissipates but I suspect all the bald eagle, mink and otter on the river are illiterate.

The International Joint Commission (IJC; Canada, United States) has an active committee on Great Lakes Adaptive Management that will assess how Plan 2014 is restoring ecosystem integrity. A study will begin in 2017, funded by the Ontario Ministry of the Environment and Climate Change will examine the impact of Plan 2014 on mercury. If mercury mobilized by Plan 2014 threatens the aquatic food web there is a process by which the IJC can be informed and adjust Plan 2014 to protect the biota and people that rely on this magnificent waterway.

Michael Twiss is a Professor of Biology at Clarkson University, an elected member of the Board of Directors of the International Association for Great Lakes Research, and is appointed to the Great Lakes Science Advisory Board of the International Joint Commission and the USEPA Great Lakes Advisory Board’s Science and Information Subcommittee. He teaches aquatic science and botany in the Adirondack Semester offered by Clarkson University in Saranac Lake. Contact info: mtwiss@clarkson.edu

News Archive