For the past few seasons, Lake Erie has “bloomed,” but not in a positive sort of way. Instead of seeing all sorts of game fish and desirable forage species expanding in the lake, anglers have witnessed dramatic blooms of blue-green algae.
These blooms are evident by “slicks” of algae on the surface of the water that look like green paint. The algae constitutes an unsightly mess that clings to boats and everything else, and when the algae dies and decomposes in the fall, it wreaks havoc with dissolved oxygen levels in the water.
According to Jeff Tyson, a fisheries biologist supervisor with the Ohio Department of Natural Resources Division of Wildlife, blue-green algae is found in most bodies of water throughout the country. It blooms extensively only when those water bodies have excessive levels of phosphorus. Blooms typically occur in late summer or early fall when water temperatures exceed 60 degrees.
Some phosphorus is a good thing, says Tyson. It drives good algal production, which feeds zooplankton, which feeds fish. In high concentrations, however, toxic blue-green algae blooms and contributes nothing toward zooplankton production.
Rooting out the cause
Blue-green algal blooms in Lake Erie are not a new phenomenon. During the period when Lake Erie was declared “dead” in the 1960s, similar blue-green algal blooms were extensive. The source of the phosphorous that produced those blooms was pollution from sewage and industrial outflows. During the ’70s, the U.S. and Canada implemented the Great Lakes Water Quality Agreement, which mandated that municipal sewage and industrial waste sources reduce phosphorus discharges into the lake. As a result, blue-green algal blooms virtually stopped, causing walleye and yellow perch populations to flourish in the ’80s and ’90s and Lake Erie to be declared recovered.
Experts believe that more recent blue-green algal blooms, beginning in the late ’90s, are associated with an increase in the inputs of phosphorus as a result of nonpoint sources, primarily agricultural runoff.
Phosphorous is a nutrient essential for plant growth. It is used extensively in fertilizers applied to increase production of agricultural plants and to grow lush green lawns.
Quantifying the threat
Tyson has been flooded with questions and concerns regarding the algae. Can a dog get sick from drinking the water? Can swimmers get sick? And, of course, what effect will it have on the walleye populations?
“Anything that is invasive or foreign to us is bad, as we have no way to control it or know the long-term effect it will have,” Tyson explains. “The return of blue-green algal blooms to Lake Erie suggests that Lake Erie is not operating properly. The impact that these blooms will have on Lake Erie fish production is unclear, but given past history I am concerned.
“Human health impacts of these blooms have been demonstrated in other systems, but there are ways to minimize that risk,” Tyson continues. “Most demonstrated human health effects are from ingestion of water or full-body contact, such as while swimming. Consumption can make you sick, as it affects your liver, but the effect it has will differ in each person. Therefore, people should not ingest untreated water from Lake Erie, and should minimize swimming activities during blooms. Minimal skin contact with the water (such as when fishing) should not affect human health.”
Consuming fish from these waters is still OK, as test results have not revealed any contamination in fish tissue. And so far the blooms don’t seem to be causing any direct mortality of adult fish populations in Lake Erie.
The only certainty is that the future of the blue-green algae in Lake Erie is unclear. Yet as long as large levels of phosphorus continue to enter the water and nothing is done to combat it, blue-green algae isn’t likely to go away anytime soon.
