Move over phosphorus - algae has a new favorite food.
New research reveals nitrogen could play a greater role in the causes of algal blooms than what scientists initially believed. That's what Andrew Camilleri, a masters student at the University of Minnesota Duluth, found in his two years studying sites in the Great Lakes.
"It's been thought that the Great Lakes was all phosphorus limited, meaning that the algae needed phosphorus to grow," said the water resources science student. "But we found there was much more nitrogen limitation."
Camilleri's team was expecting algae growth to be tied mainly to the amount of phosphorus in the water - not nitrogen.
The study looked specifically at benthic algae, which grows on the bottom of the lake. Benthic algae growth can be good. It serves as a major food source in aquatic food webs. However, when there is an overload of nutrients in those environments, the source of food can quickly get out of hand.
"There's all this green stuff that's washing up on shores, clogging water intakes, obviously deteriorating the aesthetic value of waterfront properties, clog up fishermen's nets, so there's an issue of trying to regulate this algae," said Ted Ozersky, an assistant professor at UMD.
Algae blooms' harmful effects are well documented. But Camilleri's findings breathe new light into what causes them in the first place.
"It's exciting from a scientific standpoint, but I guess frightening because nitrogen inputs are harder to control," said Camilleri.
Unlike phosphorus, which Camilleri says is easy to control how it gets into water systems, nitrogen's gaseous state makes it more difficult to control - and the problem gets trickier.
"Lake Superior has actually been growing in nitrogen and we don't know why," Camilleri said.
The three general locations studied were Green Bay, Lake Michigan and Lake Superior. All three spots have varying levels of nutrients in the water, which Camilleri says diversified their sample, giving them a "gradient of different kinds of shorelines."
"Generally speaking, it's people that add nutrients," Ozersky said, "and the way they add nutrients is sewage. Sewage treatment plants are major sources of phosphorus and nitrogen. Also, fertilizers that we apply to the landscape for agriculture."
Algal blooms are more common on lakes with higher population densities, which is why Lake Superior doesn't experience as intense algal blooms as Lake Erie and Green Bay. However, because the lake is clear and allows a lot of sunlight to feed the vegetation at the bottom of the water, it doesn't take much to see algae grow when nutrients make their way into the water.
The necessity for this research, Camilleri says, is that by understanding the primary sources of algal blooms, they can be better isolated to prevent them from happening in the future.
Camilleri will be presenting his research at the Science on Deck event on Friday aboard the Blue Heron research vessel, which will be docked at the Twin Ports Harbor near the Great Lakes Aquarium. The event is free and goes from noon-4 p.m., including Camilleri's presentation at 3:15 p.m..