From the Operations Crew

From the Operations Crew
News - 5/5/2020
Filamentous Algae

We all look forward to this time of year. As the weather improves and the days lengthen, the natural world around us explodes with life, growth, and color. Our yards, parks, and natural spaces seem to bloom and blossom instantly. While we can’t see such drastic changes on the surface of a lake, aquatic ecosystems are behaving the same way as our lawns and gardens. Growth of plants and algae rise exponentially at this time of year, which often presents some challenges to the aesthetic and recreational standards the LOC aims to maintain.

You may notice the growth of filamentous algae, especially in shallow areas where sunlight reaches the sediment. The term “filamentous algae” refers to a set of species that behave in the same way, forming stringy colonies that make mats. It first grows on bottom substrates such as rocks, silt, aquatic plants, and structures, and for a long time will stay down there out of sight. During warm, sunny weather this algae does what all photosynthetic organisms do, which is generate oxygen. In fact, they generate enough oxygen to create bubbles, which get trapped in the algal mats and make them buoyant, bringing them to the surface. Once on the surface, sunlight bleaches the mats and they start to decay.



While all forms of algae play an important role in aquatic ecosystems, this is the point at which they become problematic for lake users. Filamentous algae grow aggressively in warm, shallow, and nutrient rich water. The LOC manages nutrient inputs, riparian habitat, aeration, and surface debris removal with a variety of techniques designed to minimize the impact of algal growth. Nevertheless, just as parts of your backyard seem to “get away from you” despite best efforts in Spring and Summer, algae still present a challenge on Oswego Lake.

The LOC’s Pesticide Discharge Management Plan (PDMP) defines action thresholds for when algaecides and herbicides should be applied. For filamentous algae, the threshold is reached when recreation is impacted, or when we receive substantiated complaints from shareholders. There are several options for treatment, but the most effective is an application of a product such as Captain XTR, a chelated copper-based algaecide. Historical use of copper sulfate as an algaecide has a negative environmental record due to its limited duration efficacy and toxicity, but modern chelated copper products have been shown to have much lower toxicity and greater efficacy. Conveniently, there are no irrigation, swimming, fishing, or other water use restrictions.  When we schedule an application of this type, you will receive a notification at least 24 hours in advance at the email address you have on file at the LOC. We ask that if you are in or on the water at the time, you stay clear of the application boat, as its bearing and speed are important for a proper and even application. Depending on conditions, you can usually start to see the impact of the treatment within 3-5 days, but the full effects should not be expected for at least a week. As it dies back, it can still be an aesthetic issue for a short while, but overall conditions should markedly improve each day thereafter.

While these treatments are safe and effective, we do aim to make them as seldom as possible for the overall health of the ecosystem. Also, there is a restricted interval for re-treatment, as it’s unavoidable that at certain times there may be a few days of less than desirable algae conditions.

We hope that our debris collection systems and summer crew can keep up with manually removing the dead algae, but we always welcome your help. A few scoops of algae and leaves hardly take up any space in your yard debris container or compost bin. Or, put it and any other debris you recover from the lake (please, no yard debris) in a bucket or can and call us and we’ll come by and empty it. You can also help by reducing nutrient inputs: limiting fertilizer use near the water or around storm drains, switching to phosphorus-free fertilizers, and keeping leaves and yard debris out of the water. Feel free to contact Operations with any questions you may have or for tips about managing your lakefront to minimize nuisance filamentous algae. Every effort helps, we thank you in advance!