This weekend, thousands of rowers will be competing in the Head of the Charles Regatta, but the harmful algae bloom that's been in the Charles River since the summer is still there.

For months, Massachusetts' cyanobacteria advisory page has listed parts of the river that separate Boston and Cambridge . Also called blue-green algae, the bacteria can be toxic to people and animals.

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"It can cause things like skin irritation, skin eye irritation, also other digestion problems if it is ingested, so it is something to be aware of," said Laura Jasinski, executive director of the Charles River Conservancy.

Jasinski says there are several things that can fuel a bloom.

"Some of that is heat, so we tend to see them more

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