BLACK LAKE TOXIC ALGAE HEALTH ADVISORY 8/4/14
The toxin level for microcystin was 162 micrograms/L in a sample collected on July 29, 2014, which is above the safe level. The state recreational advisory level is 6 micrograms.
Here is an article that describes what toxic algae is and why it's a health risk. Just bathe you and your animals after going in the lake. http://www.co.thurston.wa.us/health/ehadm/swimming/pdf/BGAlgae.pdf