Scientists not sure what's causing Great Lakes algae

DETROIT (AP) — A newly released report says there's a lack of hard scientific evidence about what's causing massive algae blooms spreading across most of the Great Lakes.

The report says it's widely assumed that runoff from farms and sewage treatment plants is a leading cause of resurgent algae. Invasive mussels and climate change are considered likely factors as well. But it says those beliefs are based largely on observations instead of more reliable scientific experimentation.

The document was presented Thursday during the annual meeting of the International Joint Commission, a U.S.-Canadian agency that advises both nations on issues affecting the Great Lakes and other shared waters.

Federal officials say nuisance and toxic algae will be a high priority under a continuing program to deal with the lakes' biggest environmental problems.