This has been a banner year for algal blooms. Not only are we seeing the stringy, nuisance algae in abundance, but also many Harmful Algal Blooms.
Most algae are harmless, and an important part of the food web, but some species of algae produce toxins that can be harmful to people and animals. These are commonly called harmful algal blooms or HABs.
The NYS DEC has been tracking these for a few years now. They regularly publish updates at: Harmful Algal Blooms Notifications webpage.
For many waterbodies, the blooms are isolated within a specific part of a lake, usually a shoreline, but they can be widespread throughout the lake. Blooms also come and go. They may last an hour or less, or several days. Areas with isolated blooms can be avoided and recreation can continue where blooms are not seen. In all cases, it is better to be safe than sorry. Avoid any water contact in areas where there are suspected blooms. The picture key here is helpful, but not definitive.
This message from the NYS DEC: “If you suspect you have seen a harmful algal bloom, or you, your family, or pet has been in contact with a harmful algal bloom, please follow the instructions for reporting a bloom to DEC. If you see it, avoid it and report it!”