Roger Hannigan Gilson is reporting for the Times Union a green slick of toxic bacteria has formed on a large section of the Wallkill River in Ulster County over the past several days. Commonly referred to as algal blooms, these slicks actually consist of a toxic form of cyanobacteria, which can be harmful to humans and deadly to dogs. The Department of Environmental Conservation received nine reports of the toxic bloom during the past week on a section of the Wallkill from the village of New Paltz to Sturgeon Pool in Rifton. There has been an additional report of cyanobacteria in the Wallkill tributary Rondout Creek in Rosendale, suggesting the slick might be spreading to the city of Kingston. But, according to Dan Shapley, the co-director of science and patrol for the environmental group Riverkeeper, the size of the slick is far greater. Shapley said the slick extends more than 14 miles, from the community gardens in New Paltz to Creek Lochs in Rosendale, where the Wallkill meets the Rondout. Cyanobacteria can release toxins that can cause irritation and a burning sensation when touching human skin. Ingesting or breathing in droplets of water with these toxins can lead to illness and some people experience allergic reactions and breathing difficulties when exposed, according to the DEC. The slicks can be much more harmful to dogs, resulting in stumbling, difficulty breathing, elevated heart rate, seizures, convulsions and paralysis. Dogs occasionally die from exposure, according to Shapley. Cyanobacteria develops in waterbodies when two distinct conditions exist: high levels of nitrogen and phosphorous, both of which are found in fertilizer, and warm, still water. This is not the first time the slicks have struck the Wallkill. Blooms have been reported near New Paltz dating back to 2015, according to the DEC. A bloom in 2016 affected 30 miles of the river from Montgomery in Orange County to Rosendale, and lasted for more than 50 days. Read the full story in the Times Union.