The state of the Meramec this year, with it's very low but not clear water, has made me think of some of the causes of an over abundance of algae. Maybe fertilizer run off from farms or something. I don't know that I've ever seen murkier water for being this low. That's the reason this article caught my eye:
http://www.breitbart.com/Big-Government/2014/08/02/Toxic-Water-Algae-in-Toledo-Leads-to-State-of-Emergency