water quality= green/tan bubbles ?

Went for a late afternoon dip at the south end of La Ropa today and for the second time in two months noticed green/tanish bubbles on the surface of the water. The bay was fairly calm. As the fish swims from the sewer treatment plant its a distance, hoping its more a natural phenomenon rather than man induced?

Does the municipality keep any type of regular water quality records and if so, where are the samples taken?