Government guidelines insufficient to protect freshwater ecosystem from salt pollution

According to an international study, current water quality guidelines aren't protecting freshwater from increasing salt pollution due to road de-icing salts. The research shows that freshwater salinization causes a massive loss of zooplankton and an increase in algae even when levels are within the lowest thresholds in Canada.

Salt pollution in freshwater lakes, streams, and wetlands, even when limited to levels specifically chosen to protect the environment, threatens the biodiversity and overall function of freshwater ecosystems. Rick Relyea, director of the Darrin Fresh Water Institute at Rensselaer, is an expert in the impacts of road salt on freshwater ecosystems.

Dr. Relyea is the director of the Jefferson Project at Lake George and has conducted extensive research on the effects of road salt on aquatic environments. His work has helped to establish that road salt is bad for the environment. Dr. Relyea has collaborated with an experimental network of 16 sites in four countries across North America and Europe. A Canadian scientist, Marie-Pier Hébert, led an experiment that showed that lake salinization reduces zooplankton abundance and diversity.

Significant damage is being done to freshwater lakes even though regulators have deemed them safe and protective.

Increasing salt levels threaten zooplankton, a critical food resource for many young fish, and changes caused by rising salinity could alter water quality and clarity, and cause growth and population declines in economically important fish species.

The results indicate a major threat to the freshwater environment and the need for governments to reexamine current threshold concentrations to protect lakes from salinization.

Salt pollution occurring from human activities such as the use of road de-icing salts is increasing the salinity of freshwater to the point that the guidelines designed to protect fresh waters aren't doing their job.

The Environmental Protection Agency has established a threshold for the concentration of chloride in the US. In Canada, it is 120 milligrams of chloride per liter. The thresholds are generally higher in Europe.

It can take less than a small amount of salt to make a big difference in the health of the water.

In other countries such as Germany, concentrations between 50 and 200 milligrams per liter are considered slightly polluted by salts, and concentrations between 200 and 400 are considered moderately polluted by salts.

The study shows that negative impacts are below the limits. Three quarters of the study sites had chloride concentration thresholds that caused a reduction in zooplankton.

The loss of zooplankton triggered a cascading effect that resulted in an increase in the number of freshwateralgae at almost half of the study sites.

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, according to the co-leader of the project and paper.

The scientists chose to study zooplankton communities from natural habitats instead of short-duration, single-species laboratory studies because of the greater diversity of species and naturally occurring predator-prey and competitive interactions within the zooplan.

The study was designed to understand how the thresholds would hold up in a more natural setting.

They looked at whether current water-quality guidelines protect lake organisms in regions with different geology, water chemistry, land-use, and species pools.

Many salt-contaminated lakes with chloride concentrations near or above thresholds established throughout North America and Europe might have already experienced food web shifts. The variability of our results show how thresholds should integrate the susceptibility of ecological communities at the local and regional scale. While the government guidelines may protect freshwater organisms in some regions, that is not the case for many regions in the U.S., Canada, and Europe.

Reducing the amount of road salt used to melt winter snow and ice to keep people safe and traffic moving is one of the solutions. A previous study suggests best management practices.

Current water quality guidelines across North America and Europe do not protect lakes from salinization.

More information: Current water quality guidelines across North America and Europe do not protect lakes from salinization, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2115033119. Journal information: Proceedings of the National Academy of Sciences Citation: Government guidelines insufficient to protect freshwater ecosystem from salt pollution (2022, February 21) retrieved 21 February 2022 from https://phys.org/news/2022-02-guidelines-insufficient-freshwater-ecosystem-salt.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.