Summertime Brings Algal Activity

As the summer season gets going, even with the current low water conditions, the critters in the lake that are at the bottom of the food chain get busy! The algae and other plankton that are naturally found at SML love warm waters as much as we do.

Usually, these microorganisms go about their life cycles without us ever noticing. They produce oxygen and they are food for larger zooplankton, which are food for fish. Unless they get out of balance, we really don’t have to think about them.

Sometimes algae, diatoms and cyanobacteria can become unbalanced. When they do, they overgrow and create what is called a bloom. Most of the time, these blooms are no cause for concern. They last for a short time and then things settle down. But sometimes certain cyanobacteria (aka blue-green algae) can produce toxins that if swallowed (when swimming, surfing, waterskiing) can cause rashes, intestinal and/or respiratory distress.

Harmful Algal Blooms (HABs) caused by cyanobacteria often look like spilled green or light blue paint on the surface of the water. Sometimes the blooms can look like small green granules floating in the water column or accumulated up on a beach. VDH offers photos of HABs and more reference information.

If you see conditions like this, you can report them to the Virginia Department of Health. If someone reports a suspected HAB, the VDH will alert the Department of Environmental Quality so they can collect a sample. Samples are tested for toxins at the state lab and results are returned in about 2 weeks. Only if toxin levels exceed state standards would the VDH issue a swimming advisory. No toxins have ever been found at SML that exceeded the state standards.

If a potential HAB has been reported, that location shows up on the VDH HAB Dashboard map. Several HAB reports have recently been posted on the HAB Dashboard. The first samples collected by DEQ at a location reported on June 18 had no toxins.

The SMLA Dock Watch Program continues to monitor 22 docks around the lake for cyanobacteria activity. The volunteers report any unusual findings. The Dock Watch 2025 Annual Report details how this program keeps a close eye on cyanobacteria at our docks.

A good piece of advice from the VDH is “when in doubt, stay out” to avoid potential exposures to cyanobacteria.