A mysterious resurgence of phosphorus in the Great Lakes is endangering the aquatic food chain and human health, says a binational agency that advises Canada and the U.S.

Fifteen years after the last programs to control phosphorus runoff ended, the International Joint Commission urged on Wednesday a renewed effort to get the oxygen-depleting chemical out of the water.

The call to action was one of 32 recommendations the commission made to both governments in its biennial report on the state of the Great Lakes at Detroit's Wayne State University.

The report specifically urges the two governments, which are currently renegotiating a binational water quality agreement, to include human health language in the agreement.

The report underlined a growing problem with phosphorous in the Great Lakes, especially in Lake Erie, which over the last few years has seen an increase in algal blooms caused by excessive nutrient runoff such as phosphorous.

Those blooms include blue-green algae — also known as cyanobacteria — which produce toxins that pose a health risk to people and animals when they are exposed to them in large quantities.

"We don't know where the phosphorous is coming from," Bill Bowerman, chair of the IJC's science advisory board and a wildlife ecologist at South Carolina's Clemson University, said during Wednesday's  IJC news conference.

"Some of our monitoring programs that would allow us to understand this either are under threat or have disappeared over the past 15 years."

Report points to possible culprits

The report suggests key factors likely include inadequate municipal wastewater and residential septic systems, agricultural runoff, industrial livestock operations and the impacts of climate change, which causes more frequent and intense rainstorms.

University of Windsor aquatic ecologist Douglas Haffner says eutrophication — excessive aquatic plant growth — is a growing problem all over the world.

"It's becoming a major threat again," said Haffner, who is not a member of the IJC's science advisory board.

"The problem stems from [the fact] we are now almost at seven billion people and we need to feed them. So we are farming marginal lands and increasing crop production by adding more nutrients that eventually go to the lakes and rivers."

Calling Lake Erie the "poster child" for eutrophication, the commission's U.S. co-chair, Lana Pollack, said much of the lake is back to being coated with slimy green algal blooms in the summer, as it was in the 1960s and early '70s.

"They said, 'Well, we have this one fixed.' Well, we don't have this one fixed," she said.

The commission recommended all levels of government restore and protect wetlands and forest lands, which act as a filter for some pollutants, including phosphorous.

It also recommended various ways to reduce runoff of polluted water into the lakes. That includes creating buffer strips on farmland, rain gardens and green roofs in urban areas, along with reductions in urban sprawl and its resulting impervious surfaces.

Chemicals of 'emerging concern'

The biennial report, aimed at improving water quality in a lake system that contains 20 per cent of all fresh surface water on Earth, also highlighted problems with chemicals of "emerging concern." That includes veterinary and human pharmaceuticals, flame retardants and pthalates used to make plastic flexible.  

Problems with invasive species, such as Asian carp, were also highlighted.

"With the Asian carp threatening to invade the Great Lakes, the report recommends using a revised Great Lakes Water Quality Agreement as a vehicle for the development and deployment of binational protocols for rapid response before invasive species enter the lakes," the commissioners wrote.

The spectre of Asian carp making its way into the Great Lakes has scientists warning that the invasive fish could vacuum up plankton, starving out native species such as trout and walleye. That would unravel the aquatic food web and threaten the region's $7 billion fishing industry.

Most of the concern has focused on Chicago-area waterways infested with two types of Asian carp — bighead and silver — that have slowly but surely migrated up the Mississippi River and its tributaries since escaping from Deep South fish farms.

The fast-growing and breeding fish were introduced to control the growth of algae in Arkansas aquaculture ponds, but flooding in the early 1990s allowed them to spread throughout the Mississippi watershed.

Scientists have singled out the Chicago Sanitary and Ship Canal — a man-made waterway built in 1900 to connect Lake Michigan and the Mississippi River Basin — as a potential conduit for the fish into the Great Lakes. Two underwater electric barriers built in 2002 and 2004 were meant to keep the fish out, while allowing commercial boat traffic to continue.