Rising levels of chloride, aluminum in Halifax lakes a concern, study says
Levels of chloride, arsenic and aluminum in some Halifax lakes are a concern, according to a recently published Dalhousie University study study.
The peer-reviewed study examined four decades of water quality data from 50 lakes.
It says that the concentrations of aluminum in 29 percent of the lakes, chloride in 20 percent of the lakes, and arsenic in one lake were higher than Canadian guidelines for the protection of aquatic life.
The lead researcher said rising chloride levels have a “huge impact” on a lake’s ecosystem because aquatic life is used to a certain level of salinization.
“If you increase the chloride levels,” said Rob Jamieson, “you sort of disrupt that environment and create an opportunity for organisms that are more tolerant of those chloride levels to become more dominant in the ecosystem.”
Jamieson also said that higher chloride levels are unlikely to directly harm the fish that live in the lakes, but the organisms they depend on for food.
He added that other researchers have found that blue-green algae, which produce toxins harmful to humans and pets, are more tolerant of higher chloride levels and could become a bigger problem.
The study identified urban development as a possible reason for rising concentrations of substances such as chloride.
For example, clearing forests and paving new subdivisions leads to increased runoff, which releases pollutants into nearby lakes.
New roads also need to be salted to keep the roads safe in winter.
Environmental monitoring is important
The Halifax Regional Municipality supported the Dalhousie study by paying for a helicopter, which allowed researchers to collect samples quickly.
Emma Wattie, a manager on the HRM environment and climate change team, said it is important to monitor lake waters so that human impacts on ecosystems can be detected before it is too late to make changes.
“We can’t do anything if we don’t know what’s going on in our lakes,” Wattie said.
She added that data could help the city make decisions, such as which products to use as fertilizer or where to build housing.
“Knowing the quality of certain lakes can help us decide where we should be … investing in our communities,” Wattie said.
There are more than 1,000 lakes in the municipality, she said.
Despite the concerns raised by the study, Jamieson said that overall “the water quality and lakes around the Halifax area [are] generally very good, and this water quality supports a number of recreational activities that people can participate in.”
The study, which used samples collected in 2021, is a continuation of a long-term monitoring program that began in 1980 with the Department of Fisheries and Oceans. Sampling takes place approximately every 10 years.
