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Blue-Green Algae in Colorado waters

Blog by: Matt Snider , CO 8/17/2023
Blue-green algae has made a lot of headlines this year.  So what is it and what do you need to know?  

The bloom is basically a common water bacteria that happens to be multiplying rapidly in the lake.  When this happens, it creates a "bloom" or a concentration of bacteria which may be producing harmful toxins.

If you've read any information on the blooms, you may know what it looks like: spilled paint or pea soup (and as you may guess it is often blueish or greenish.) Whether these blooms are toxic or not can only be determined by testing.

Common advice is to avoid water contact if you see anything like it. You can report suspicious sightings by contacting the CDPHE which works with CPW.

Can I still fish during a blue-green algae bloom?
Yes you can, unless the water manager prohibits it. Just keep yourself, others, and pets out of the water. Keep fresh water handy and/or cleaning wipes to wash your hands after handling fish. 

Can I boat in a lake with the algae?
Yes, just try to avoid boating through the blooms to avoid splashing. 

Can I eat fish caught from a lake suspected of blue-green algae?
Yes.  Wash the meat thoroughly with fresh water, discard the remains, and thoroughly wash yourself after cleaning the fish.  Same as usual.  

Should I go swimming in the lake?

Basically, you want to avoid all skin contact with infected waters. Easy enough.

See this Blue-green Algae FAQ provided by CDPHE.

CDPHE has a helpful map to summarize (somewhat) current conditions, graphically showing lakes around Colorado that are either confirmed to have blue-green algae problems, or are clear. Or, in some cases, in between. See the map here

Some active toxic blooms listed in Colorado at time of this writing:

Others are listed as a caution, with potential toxicity: 

Not all lakes in Colorado are tested, nor is testing required.  If you see something that looks like it may be blue-green algae, just keep it off your skin, wash thoroughly what you catch, and report it.

The good news (besides being able to fish and eat fish) is that the blooms will go away on their own. Natural events will take care of it: wind, cooling, and other factors will dissipate the algae.

Photo of what blue-green algae looks like, courtesy of CDPHE
Blog content © Matt Snider