by Sarah Olsen vtdigger.org New research shows that concentrations of nitrogen could make drinking water from lakes unsafe.Until recently it was thought that algae blooms could only be caused by high concentrations of phosphorus in lakes, but freshwater research now suggests that high levels of nitrogen can also increase the potential for harmful blooms.
The International Association for Great Lakes Research met for its 2015 conference May 25-29 at the University of Vermont. Dan Peckham, coordinator of the Harmful Algal Blooms Workgroup at the New England Interstate Water Pollution Control Commission, was the chair of a session on that topic.
Blue-green algae contains cyanobacteria, which produce the cyanotoxins that make seasonal blooms harmful, while green algae are harmless, Peckham said. Blue-green algae is the source ofseasonal toxic blooms on portions of Lake Champlain.
Hans Paerl, professor of marine and environmental sciences at the University of North Carolina-Chapel Hill. Courtesy of Hans Paerl
“Usually the concentration of cyanotoxins is associated with biodegradable dissolved phosphorus, but some people have been hypothesizing more recently that high levels of nitrogen may also be responsible,” Peckham said.
Hans Paerl, professor of marine and environmental sciences at the University of North Carolina-Chapel Hill, presented the information on nitrogen.
Paerl said freshwater researchers have developed tunnel vision by focusing on phosphorus for so long. Both nitrogen and phosphorus are needed to grow any kind of plant, including algae, he said.
“Excessive amounts of growth are caused by high levels of both nitrogen and phosphorus,” he said. Nitrogen is not worse than phosphorus, but both need to be reduced. “The bottom line is that nitrogen input needs to be controlled along with what we already know about controlling phosphorus input,” Paerl said.
Nitrogen and phosphorus wash into water bodies and then release into the air. The chemicals come from stormwater, wastewater, fossil fuels, soaps and fertilizers, according to the Environmental Protection Agency website.
“If we only reduce phosphorus we may not get there fast enough in terms of getting a lake or even a marine system back to what we would deem desirable,” Paerl said.
Paerl said the same protocols that keep phosphorus out of lakes and streams apply to nitrogen.
One difference is that sewage treatment plants will have to spend more money to remove both nitrogen and phosphorus from wastewater, he said.
“There’s no getting around that,” Paerl said.
Mike Winslow, a staff scientist at the Lake Champlain Committee since 2001, also presented at the conference on harmful algal blooms. Winslow has been monitoring Lake Champlain since 2003. He analyzed water samples until 2012. After that, the committee relied on visual monitoring.
Volunteers do not visually monitor harmful algae blooms in Lake Champlain until mid-June because the largest blooms are usually in August, he said.
“We certainly don’t see the extent of blooms that they see on Lake Erie,” Winslow said. “I mean their blooms are bigger than our lake.”
Winslow said he has never known of a time where blooms in Lake Champlain have affected the quality of drinking water in Vermont.
Elevated levels of nitrogen in drinking water are known to cause health problems in young children, according to theVermont Health Department.