What is Filamentous Green Algae?

Filamentous green algae control services in Florida

There are probably many different types of algae in lakes and ponds at any given time, although they may not be causing any strain on the pond’s health. Knowing how to identify what kind of algae is in a waterbody is paramount to determining if they may be negatively affecting its health now or if it might in the future.

Filamentous green algae are relatively easy to identify, as it often forms dense mats that float on a pond’s surface, looking a little bit like wet wool. Most pond owners and managers refer to this type of algae as pond scum, but it is also called string or floating algae. Filamentous algae is a common pond alga that, when left untreated, can quickly cover the entirety of the pond’s surface.

Algae are a natural and important part of a healthy pond or lake, providing oxygen and forming the base of the aquatic food chain. Problems arise when too many nutrients cause algal blooms or when filamentous algae include mats, moss, or scum on the surface of the water body. That’s why algae control in Florida is crucial to the health of the many lakes and ponds in the state.

What Is Filamentous Green Algae

Filamentous algae are a common aquatic plant problem faced by pond managers. These algae differ from planktonic algae made up of free-floating individual cells. They play an important role in the pond’s ecosystem, producing oxygen and food for animals that live in the water body. However, they can also cause issues such as stagnation and clogs.

Filamentous algae begin as microscopic plants that then link together and become mesh-like filaments. These rudimentary plants usually grow on the surface of hard objects but can break free into floating mats. These algae begin growing in the shallow water along the bottom of water bodies where the light penetration is high and aquatic plants or rocks in the water.

The algae photosynthesize, producing oxygen, and bubbles get trapped in the mats, causing them to float to the surface. The filaments become entwined and form dense mats that block sunlight and keep it from reaching the depths of a lake or pond.

This type of algae does not have roots, it gets nutrients from the water, so its growth and reproduction are entirely dependent on the amount of nutrients in the water. Since stormwater ponds collect water that flows through roads and yards, they often collect fertilizer used on lawns and grow an abundance of algae due to the excess nutrients they contain. For this reason, it is not unusual for stormwater ponds to become filled with large floating mats of algae, especially during the warmer months of the year.

There are several different filamentous algae species, including green filamentous algae and cyanobacteria or blue-green algae, and mats often consist of more than one species.

What Causes Algal Accumulations?

Accumulations of filamentous algae are caused by an overload of nutrients in the pond or lake water, especially nitrogen and phosphorus. In some instances, these nutrients are added as fertilizers to stimulate the growth of the planktonic algae eaten by microscopic zooplankton and insects. The zooplankton and insects then become food for fish in the pond.

In other instances, excess nutrients unintentionally enter the water body as runoff from fertilized crops and pet, livestock, and wildlife waste. Taking regular and early measures to control these nutrients will help mitigate problems associated with filamentous algae.

Is Filamentous Green Algae Harmful?

In general, although they look and smell nasty, filamentous green algae do not create toxins harmful to humans. However, they offer no real benefit to ponds and lakes and this type of algae cannot be eaten by aquatic animals. It’s also important to know that beyond filamentous green algae there are certain types of filamentous algae that do produce toxins and can be harmful. Proper identification of the algal species by a professional is the best way to determine the type of algal bloom and potential threat.

Filamentous algae can significantly impact the life of a pond. It can reproduce at an amazingly fast rate, seemingly overnight. Algae has a short life, and when it dies off, it is eaten by decomposer bacteria. These bacteria emit dangerous carbon dioxide (CO2), and if there are many dead algae and bacteria, the CO2 levels could be hazardous. The pond can choke itself and become a dead zone.

How Do You Remove Filamentous Green Algae?

Filamentous algae can proliferate quickly, so fast that in a matter of weeks, they can form mats that float to the surface of ponds and lakes. Proactive lake and pond management is more sustainable than trying to remove filamentous green algae from lakes and ponds. The best way to help prevent ponds from algae overgrowth is to reduce nutrients in waterbodies. Avoid fertilizing the ground around a pond or lake, and add a vegetative buffer of native plants around the pond to help filter excess nutrients from stormwater runoff. Excess nutrients can also be controlled by use of the nutrient remediation products such as Phoslock, Alum and biochar.

Additionally, lake and pond fountains or submersed aeration systems can be installed to help improve circulation and increase dissolved oxygen levels. Dissolved oxygen supports desirable fish and microbes, eliminates toxins, improves water clarity, limits algae, muck, and bad odors, and helps reduce the impact of organic pollutants. Adding naturally occurring beneficial bacteria to digest materials in pond sludge also helps lower the organic material in the water and increase oxygen levels, therefore improving water quality and

For situations where a filamentous algae bloom is already present, there are solutions to help manage the algae:

Physical Control – although this method is labor-intensive, raking the algal mats from the water’s surface is effective, especially for smaller water bodies. Once raked off the surface of the pond, the mats can be disposed of somewhere else in the landscape, far enough away from the water so that they don’t decay and trigger another algal bloom. This is a time-consuming method that doesn’t guarantee blooms won’t occur in the future.

Algacidal Control – aquatic algaecides developed for use in ponds can help control algae growth in water bodies. Aquatic algaecides that are EPA-registered should only be applied by licensed professionals in proper doses.

Once existing algae blooms are controlled, it is recommended to implement the sustainable pond management solutions noted above for ongoing balanced water quality, thus reducing the likelihood of future water quality issues like filamentous algal blooms. Remember, there are many types of filamentous algae and proper identification through professional water testing is the best way to get a complete understanding of the problem at hand and to help devise a plan for controlling the algae and implementing sustainable solutions for ongoing management.

Professional help is often needed to keep a community’s pond sparkling and healthy. Contact us for lake & pond management in Florida today. We’ll be happy to answer all your questions and perform a free on-site inspection of your pond.