Researchers who conducted a large crowdsourced global experiment on the effects of deicing salt say their results show that current water quality guidelines across Europe and North America are not enough to protect lakes from salinization.
The research network for the study involved 16 sites in four countries and dozens of scientists who believe that the road salt problem has flown well under society’s radar, particularly in terms of its effects on zooplankton. These organisms are key members of the food web that clear lakes of algae, but are also food for fish.
At 80% of the study sites, chloride concentration thresholds that caused a more than 50% reduction in zooplankton were at or below the governments’ established chloride thresholds, triggering a cascading increase in phytoplankton biomass or microscopic freshwater algae.
Study contributor Dr. Andrea Kirkwood, Associate Professor of Biology at Ontario Tech University, notes that just one teaspoon (about five grams) of salt in a typical large water cooler jug can be harmful for aquatic organisms. Despite this danger, she says the acceptable threshold for chloride concentration in Canada is 120 milligrams per litre, while in the U.S., it is considerably less stringent at 230 milligrams per litre.
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“Changes caused by rising salinity alter nutrient cycling, water quality and clarity, and instigate growth and population declines in economically important fish species,” says Dr. Kirkwood in a statement about the study. “Governments need to reassess current threshold concentrations to protect lakes from salinization due to sodium chloride, one of the most common salt types leading to freshwater salinization,” she added.
The study notes that human-induced salinization is caused by the application of road deicing salts, agricultural practices, resource mining, and climate change. After deicing salts dissolve in rainwater and snowmelt, they wash into adjacent surface and groundwater.
Dr. Shelley Arnott, Professor of Aquatic Ecology at Queen’s University and co-leader of the project and research paper, says that more algae in the water could lead to a reduction in water clarity, which could affect organisms living on the bottom of lakes as well.
“The loss of zooplankton leading to more algae has the potential to alter lake ecosystems in ways that might change the services lakes provide, namely recreational opportunities, drinking water quality, and fisheries,” Dr. Arnott said in a statement.