Did you know that there are over 400,000 known varieties of algae? 

So, when we say we want to help you understand algae, we really want to give more information on the algae that’s found in Geist Lake. So allow us to dive a little deeper, if you’ll forgive the pun. 

Native Algae 

Though we treat algae on the lake, these single-celled organisms aren’t inherently bad. The goal is never to rid Geist of all algae because many types are beneficial to the ecosystem. As the base of the aquatic food chain, they provide habitat, shelter, and oxygen for fish and other organisms. Native plants also stabilize the sediments that would otherwise be erodible and provide nutrient competition for the blue-green algae

For example, the fruits of the common Coontail algae provide a source of food for ducks and other wildlife. Below the water, they provide shelter for tiny invertebrates that are eaten by fish, frogs, and other wildlife species. 

Invasive Species

The algae that generally become a problem are invasive species. They can cause all sorts of problems for the natural environment and recreational use of water. Eurasian milfoil is the algae that Geist struggles with and sees the most damage from. This aquatic weed plagues the native plant and animal life and contributes to the degradation of an entire ecosystem.

Eurasian milfoil grows and forms thick mats over the surface of the water. This canopy of vegetation completely blocks out the sunlight and kills the native aquatic plants that fish and other underwater species rely on for food and shelter. This aquatic weed threatens to overtake the lake and severely shift the ecological balance. That’s not to mention making recreational activities like fishing and boating next to impossible.

Algae on Geist Lake

Blue-Green Algae

The algae you likely hear about most often is blue-green algae, which can be toxic to humans and animals. Geist Lake does not currently have any toxic blue-green algae but should conditions continue to worsen, it is a possibility in the future. 

While blue-green algae (technically cyanobacteria) are naturally present in freshwater, under certain conditions, they can overgrow and form toxic “blooms.” These conditions are a combination of warm, shallow, undisturbed, nutrient-rich surface waters that receive a lot of sunlight. 

Of course, we can’t control the amount of sunlight or the temperature, but the vital nutrients that the blue-green algae feed on are within our control. One of the goals of a reservoir conservancy district is to restore the integrity of the lake’s waters through catch basins, stream bank remediation, and reduce the pollutants and phosphorus that feed algae and aquatic weeds.

Algae Treatment

The Geist Lake Coalition (GLC) helps control the invasive species with our annual aquatic weed and algae control program. We use top-quality, EPA-approved herbicides and algaecides to manage resident lake access areas.

We can only afford to address the green algae on the lake where we’ve received contributions, so only about 1/20th of the lake is treated. The partial treatment of the lake is not perfect and never will be, but that’s why we’re working hard to form a reservoir conservancy district that will have the ability to enact long-term, sustainable solutions.

If you’re within the proposed district and interested in helping establish a prosperous and healthy Geist Reservoir, sign the petition.