Environmentalists and researches say blue-green algae is worsening in freshwater ponds on Long Island.

The algae forms when too much nitrogen is present, usually from sewage or fertilizer runoff. Last year, Suffolk County led the state with 16 lakes closed because of the algae, including Lake Ronkonkoma.

This year, the scientists who perform research for the state Department of Environmental Conservation say that Wickapogue Pond in Southampton and Laurel Lake in Mattituck have unusually early signs of the algae. Another type of algae called mahogany tide is also showing elevated levels in the Peconic River, and scientists say it's showing up earlier than in past years.

Experts say blue-green algae is not only toxic for marine life, it's also harmful to humans and other animals. There have been reports of dog mortalities from licking their paws after contact with the algae.

To combat the spreading problem, environmentalists say the 350,000 Suffolk homes that discharge wastewater through cesspools need to be addressed. They say sewage treatment plants may need to be constructed as well.

Environmental activists are calling for action to combat the effects of the algae.