There is no swimming at Lake Pocotopaug in East Hampton after routine testing showed an algae bloom, according to the town’s website. According to the Chatham Health District, blue-green algae is not harmful in normal circumstances. An algae bloom is a rapid increase in the amount of algae and can be caused by a combination of warmer water temperatures and high nutrient concentrations that allows the algae to spread. As of August 8 the health district determined the water at Lake Pocotopaug was unsafe and officials closed the public swimming areas. Officials will retest the water and advise residents when it is safe to swim again.