Written by Erin Stewart, Territory Leader & Aquatic Biologist
Nutrients are required for all living things to survive. They are metabolized for energy or fuel so organisms can develop and grow. The nutrients humans and animals need are provided by the food we eat. When food is consumed and digested, it provides the fuel to synthesize or produce direct energy. Similarly, plants take up the nutrients they need from soil and the atmosphere through roots and leaves. In lakes and ponds, these nutrients are found suspended in the water and within bottom sediments. Aquatic plants absorb nutrients through roots down in the sediments or leaves. Submerged plants also absorb (CO2) from the water and sunlight that penetrates below the water surface.
Macronutrients are the major nutrients required for survival and micronutrients are needed in smaller quantities. A reduced amount of a major nutrient would be considered a limiting nutrient and can regulate growth. In aquatic environments, the standard macronutrients are nitrogen, phosphorus and potassium as well as, magnesium, calcium and sulfur. However, nutrients, which we normally think of as a good thing, can also be very damaging to aquatic resources if concentrations are too high. If a pond or lake is experiencing excessive algae or weed growth it is likely due to an excess of one or many of these nutrients. Just like it is not good for our bodies to eat too many cookies; it is not good for water to contain more “fuel” than the aquatic life can utilize in a healthy way.
To prevent a waterbody from becoming too green or fueling excessive plant growth, there are physical, chemical and biological options to safely and effectively manage the excess nutrients in the water:
Physically changing the water movement and dissolved oxygen concentrations through pond aeration is one of the most effective ways to improve water quality and reduce the potential for algae and vegetation growth. Inducing movement of the water column from bottom to top allows the water to absorb oxygen from the surface. As this water is circulated, the stratification of the water resource is reduced or eliminated and oxygen concentrations rise at the sediment-water interface. When this layer is high in oxygen or oxidative, the nutrients in the sediments are less likely to be released into the water for nuisance plant and algae consumption.
There are also products that naturally bind to phosphorus and settle it to the bottom, thus reducing bio-available or reactive concentrations. Aluminum sulfate (alum) is a salt-based product that binds phosphorus and other suspended particles in the water, forming a floc which settles to the bottom of a pond or lake. Phoslock is another product which is a mineral bound to a bentonite or clay matrix, permanently binding phosphorus in the water and remaining active in the sediments.
Biological products also work by breaking down or "digesting" nutrients within a pond or lake. Aquatic bacteria consume and absorb nutrients making them less available for nuisance algae and weed growth. Supplementing a pond or lake with high concentrations of these beneficial bacteria accelerates the natural processes of nutrient consumption and cycling within a resource. Reduction of excess nutrients shifts the biological community structure towards more balanced biological diversity, including “good” algae, diatoms, zooplankton and fish. As other organisms feed on the beneficial bacteria, nutrients are directed towards the animal food web, leaving less for algae and weeds to use for growth.
In addition, controlling external sources of nutrients to your water resource is important. Introducing a beneficial vegetative buffer around the shoreline can help absorb runoff from surrounding areas. Preventing grass clippings, leaves and debris from collecting in the waterbody reduces the nutrient influx from this organic material. Switching to low phosphate, slow-release fertilizers near resources, or stopping fertilizer use altogether within the watershed helps limit what enters the water. It is also beneficial to limit the presence of geese and be sure not to overfeed fish.
As always, it is important to assess water chemistry of every aquatic resource, especially if there is a problem that may likely be due to a nutrient imbalance. A water quality assessment will provide the information needed to determine the best solution for or “work-out routine” to manage nutrients and get your pond or lake back into great shape.
Contact the experts at 888-480-LAKE (5253) for all of your lake, pond, wetland and fisheries management needs.Erin Stewart is an aquatic biologist and regional leader based in Colorado. She has managed lakes and ponds in the region since 2008. Erin has in-depth knowledge of water quality and its impacts to fisheries and the overall health of local aquatic environments. Erin has interests in aeration design, fisheries management and wetlands restoration. She has also worked on several projects involving the management of cyanobacteria in drinking water reservoirs and recreational lakes in Colorado.
SOLitude Lake Management is a nationwide environmental firm committed to providing sustainable solutions that improve water quality, enhance beauty, preserve natural resources and reduce our environmental footprint. SOLitude’s team of aquatic resource management professionals specializes in the development and execution of customized lake, pond, wetland and fisheries management programs that include water quality testing and restoration, nutrient remediation, algae and aquatic weed control, installation and maintenance of fountains and aeration systems, bathymetry, mechanical harvesting and hydro-raking, lake vegetation studies, biological assessments, habitat evaluations, and invasive species management. Services and educational resources are available to clients nationwide, including homeowners associations, multi-family and apartment communities, golf courses, commercial developments, ranches, private landowners, reservoirs, recreational and public lakes, municipalities, drinking water authorities, parks, and state and federal agencies. SOLitude Lake Management is a proud member of the Rentokil Steritech family of companies in North America.