Notice the reddish water along some local beaches this weekend? Since we first reported on it Saturday morning, it’s spread. The photo above was tweeted by Russ Walker, who photographed it on Alki Point late today; next photo is from Chris Johnson, who saw it at Burien’s Seahurst Park.

Again, if you missed our Saturday story (and last year’s coverage), this is caused by single-cell organisms known as noctiluca. It’s NOT “red tide,” not toxic at all; it is described as common in Puget Sound, though last year was the first time in three years that its bloom drew a lot of attention (here’s what the state Ecology Department wrote about it in 2011; we’ll be following up with them about this year’s sightings).