Safety alert issued for suspected algae bloom at Lake Lanier cove

A suspected harmful algae bloom in a small cove of Lake Lanier’s Six Mile Embayment has prompted a swimming safety alert in Cumming, putting a familiar Forsyth County summer spot under renewed scrutiny. Chattahoochee Riverkeeper said the bloom appeared confined to a single isolated area after it was first observed on Sunday, June 7.

The warning is aimed at the people most likely to be on the lake as heat and weekend traffic build: swimmers, boaters, anglers and pet owners. Riverkeeper told visitors to stay away from water that looks discolored, smells foul or contains green or blue scum, all signs that can point to a harmful algal bloom. The concern is immediate because exposure can happen through skin contact, swallowing contaminated water or breathing in droplets and aerosols near the bloom.

Pets are part of the risk, too. The alert matters for families with dogs and children because animals can be exposed if they drink from or play in affected water, and the U.S. Environmental Protection Agency says harmful algal blooms can threaten humans, wildlife and pets. The EPA also says exposure can come through direct contact, inhalation of droplets or aerosols, and contaminated drinking water.

Chattahoochee Riverkeeper said it monitors Lake Lanier year-round and conducts monthly nutrient monitoring from April through October. The group has said its 2025 monitoring helped bring attention to Lake Lanier’s highest algae levels in years, and it previously said the lake had its highest algae levels in 20 years based on 2019 data. Riverkeeper has also linked recurring algae problems on Lake Lanier to nutrient pollution and stormwater runoff.

The cove warning lands against a wider history of bloom concerns on the lake and nearby waterways. Chattahoochee Riverkeeper said it documented its first suspected animal death tied to a harmful algal bloom in 2021 on the main stem of the Chattahoochee River at Bull Sluice Lake along the Gold Branch Trail. Since then, it has documented blooms on Lake Lanier, West Point Lake and Lake Harding in the late summer and early fall.

Lake Lanier remains a major public asset for Forsyth County and metro Atlanta, serving water supply, flood protection and recreation at the same time. That makes even a localized bloom in the Six Mile Embayment more than a minor nuisance, especially when summer lake use is climbing and a few feet of polluted water can quickly complicate a day on the water. The practical rule from Riverkeeper is simple: if the water looks or smells wrong, stay out and keep pets away.