Editor's Notebook: Tiny Canary in a Freshwater Coal Mine
Bowdoin College researchers are collecting data this summer on a freshwater zooplankton called Daphnia.

Editor's Notebook: Tiny Canary in a Freshwater Coal Mine

A nearly microscopic creature could provide huge insights on the impact of rock salt on freshwater bodies. Plus, Minnesota acknowledges salt sources other than winter deicing.

July 18, 2019

Researchers at Maine’s Bowdoin College have begun studying the impact of road salt on that state’s freshwater bodies, according to a recent report (http://bit.ly/2xQ6RUa).

When compared to historic data, some of Maine's freshwater ecosystems, particularly those close to roads, have been testing higher for sodium chloride – i.e. rock salt.

To better understand how all this salt is affecting the chemistry of Maine's lake waters, a Bowdoin professor and two student assistants are collecting data this summer on a freshwater zooplankton called Daphnia. The tiny crustacean is like a canary in a coal mine and can indicate at what level a contaminant is unsafe for an ecosystem. Specifically, the research is looking for chloride (from rock salt) and calcium (naturally occurring but impacted by salt) levels in freshwater lakes and streams and the impact on the creatures’ tiny shells.

While weaker shells could indicate elevated chloride and low calcium levels, the researchers say at this point there are numerous other factors that could influence shell strength and more study is needed.

And in related news, the Minnesota Pollution Control Agency (MPCA) is working with partners to develop a Statewide Chloride Management Plan that will address the impact of salt on freshwater bodies.

What I found to be most interesting in this article is the acknowledgement that rock salt from winter snow and ice operations isn’t the only culprit tainting freshwater resources. According to a recent article in the Country Messenger (http://bit.ly/32rWbZT):

“While most people are familiar with the harmful impacts of winter road salt, it turns out there are also several other significant ways that chloride makes its way into our environment. Some surprising culprits include water softener salt, agricultural fertilizer, manure, industrial discharges from factories, and dust suppressants applied to dirt and gravel roads. In fact, a 2019 report by the University of Minnesota estimates that 65% of all chloride discharged into lakes and rivers by wastewater treatment plants (136,000 tons of chloride annually) comes from water softeners.”

This may be a critical fact in the defense of winter services if, in the future, regulating agencies place a target on the backs of commercial snow and ice professionals to limit rock salt usage.

According to the article, MPCA is asking the public to provide comments on the draft of the states  proposed chloride management plan, which can be found at: www.pca.state.mn.us/water/draft-statewide-chloride-management-plan. Send comments via email to Eric Alms at eric.alms@state.mn.us.