Posted July 31, 2012:
Why do the ponds have a lot of algae and plant material this time of year?
Typically, summertime is the growing season for all aquatic plant material due to (1) the rainy season bringing a lot of new water in the ponds and (2) a spike in the nutrient levels in the ponds, which causes any type of plant matter to grow.
The biggest issue we are experiencing right now is the growth of an underwater plant called hydrilla. It grows to the surface where it forms dense mats, and it can grow in water levels only a few inches deep or over 20 feet deep. Hydrilla grows very quickly, up to 10 inches per day under the right conditions, although in Brighton Lakes, it has been growing one or two inches per day.
The District’s aquatic weed control contractor, American Ecosystems, is in the community at least two or three times each month, monitoring the ponds for all noxious plant materials, and treating them as necessary. When hydrilla is sprayed, the plant itself will begin to turn brown and die. During this decomposition stage, it will generally cause algae to bloom on top of the water as nutrients are released. The herbicide being used is Sonar, which is a contact herbicide, meaning the chemical has to come in contact with the plant material. It is an effective product, but it takes 30 to 45 days and multiple treatments.
As residents, you can help!
While the District will continue to monitor, maintain and treat these ponds through the contract with American Ecosystems, there are some things you as residents as do to help.
First, remember all these ponds are intended for stormwater management, and they are all part of an integrated stormwater management system. What affects one will affect others.
- Do not blow your grass clippings in the ponds, in the street or down the culverts, or allow your landscape contractors to do so, since these end up in the ponds and cause the nutrient levels to spike.
- Keep fertilizer at least 15 feet from the edge of the pond. Fertilizer that runs into the pond also causes a rise in nutrient levels, which causes any plant matter—good and bad—in the ponds to grow, just as it would your grass.
Aquatic Weed Control
The District maintains the stormwater retention areas within Brighton Lakes, a major function that includes controlling the aquatic weeds within the waters. The District currently has a contract with American Ecosystems to perform these functions, which includes monthly inspections and treatment of aquatic weeds and algae within the stormwater ponds and canals.
Treatments include hand removal of algae, installing plant material to help absorb the excess nutrients in the pond, and applying chemical treatments to noxious species as needed based on monthly observations.
- Visually interesting stormwater retention ponds and canals with attractive plant material
- Compliance with permits with other governmental agencies
- Healthier food chain in the aquatic system for other wildlife
- Help control mosquito population with the reduction in weeds and algae
- Rooted plants help stabilize the lake banks and shorelines
What Residents Can Do
- Do not fertilize the pond or lake
- Do not apply lawn fertilizers closer than 15 feet from the shoreline
- Do not blow lawn clippings into the pond or lake or into the street where it can run through the drainage system
Some of the problems caused by aquatic weeds are as follows:
- Interfere with or prohibit recreational activities
- Detract from the aesthetic appeal of a body of water
- Stunt or interfere with a balanced fish population
- Fish kills due to removal of too much oxygen from the water
- Produce quiet water areas that are ideal for mosquito breeding
- Certain algae can give water bad tastes and odors
- Impede water flow in drainage ditches, irrigation canals, and culverts, causing water to back up
- Deposition of weeds, sediment, and debris, can cause bodies of water to fill in
(suggestions and problems provided by Carole A. Lembi, Aquatic Weed Specialist, Purdue University)