Officials: Algae in Ohio lake poses health risks Posted 5/23/2009 10:40 AM ET ST. MARYS, Ohio (AP) Ohio park officials say an abundance of toxic algae at a western Ohio Lake poses a health risk for swimmers and boaters. The algae at Grand Lake St. Marys releases a neurotoxin that can cause skin rashes and sore throats and kill small animals. State environmental officials say a water sample this week showed the toxin level at four times the low-risk level set by the World Health Organization. Officials have posted water-quality warnings as the swim season begins. The 13,000-acre lake in Mercer and Auglaize (AW'-glayz) counties is considered one of the state's most polluted and is its first inland lake where algae has created a health risk. Local activists say fertilizers and manure from nearby farms have contaminated the lake.