The Clam Shell Liming Project
Maine rivers have been greatly affected by human activity, most notably intensive forestry practices, industrialization and acid rain. Rivers most affected are those in the Downeast region, which are characterized by thin soils and low alkalinity bedrock. With a significantly decreased ability to buffer increasing acidity and nutrient loss, pH levels in these rivers are often low enough to be detrimental to fish health, particularly for environmentally sensitive species such as Brook Trout and Atlantic Salmon.
Inspired by large-scale liming projects in Europe that have shown positive results for streams with similar water quality issues, the Maine Department of Environmental Protection's Salmon Program developed the Clam Shell Liming Project for implementation by Project Salmon Habitat and River Enhancement (SHARE), an NGO well known for restoration activities in Downeast Maine. Maine Fishery Resources Office staff have been providing technical and financial support. Scientists hope that, by treating streams with clam shells as a lasting, calcium carbonate source, they can improve water quality by reducing acidity while also providing better calcium nutrition for fish and neutralizing aluminum and other toxic metals within the system (Whiting 2013).
The project began in 2010 with one site and 2 metric tons of clam shells. Now, five years later in 2014, the study has expanded to nine separate sites treated with more than 10 tons of shells within the Machias and East Machias watersheds of Downeast Maine.
The ultimate goal? To increase biodiversity and improve ecosystem integrity throughout Maine's salmon rivers by using clam shells as a calcium carbonate source.
At each site, approximately 40% of the stream bottom is treated with clam shells, which act as a calcium carbonate source and increases alkalinity within the stream. The clam shells were chosen for their large surface areas and potential to form good habitat for both fish and aquatic invertebrates. Currently, the clam shells appear to be positively impacting a wide range of physical and biological factors within the stream.
Throughout the project, staff and volunteers have been actively monitoring the impacts of clam shell placement on fish abundance, macroinvertebrate diversity, leaf pack decomposition rates and a wide variety of water quality metrics. Please see the following reports and presentations for more information on this project.
For more details on the project, see the following reports and presentations:
Last updated: January 8, 2016