Health Residents urged to keep pets out of Stoughton pond after dog’s death Though there are no conclusive results yet, town officials suspect an algae bloom may be to blame for the water issues. Algae blooms can cause illnesses in humans and be deadly to pets. John Tlumacki/The Boston GlobeStoughton officials are warning residents to avoid swimming in Ames Pond, especially with their pets, after a dog died last week. Algae blooms happen when naturally occurring cyanobacteria, also known as blue-green algae, multiply quickly, according to state officials. This creates a highly concentrated area known as a cyanobacterial algae bloom, which can be harmful to people and animals.