AVERY COOPER: A harmful algal bloom is once again showing up on the Snake River. This is the fourth year in a row that Whitman County Public Health leaders have warned about algal blooms in the river. NWPB’s senior environmental correspondent Courtney Flatt has more.

COURTNEY FLATT: In spots along the Snake River, a harmful algal bloom is showing up. It’s popping up along 50 river miles. It’s slightly farther upriver than in years past.

Water samples tested positive for Microcystin, a liver toxin. 

Health leaders say people, pets and livestock should avoid any part of the river that looks like it has green or blue scum. It can look similar to spilled paint. 

Whitman Health leaders say finding the cause of these consecutive blooms is complex. The algae is made up of a bacteria that exists naturally in the river.   But when various  conditions  trigger it to grow rapidly – like warm weather, fertilizer runoff or sewage leaks –  it forms blooms. And those blooms produce the toxins.

 I’m Courtney Flatt.