AS SEEN IN North Carolina Turfgrass Magazine, Nov/Dec 2013: Written by Industry Expert, Brad Harris, Forestry Biologist and Aquatic Specialist
Turf aeration is an integral part of a successful turf and integrated pest management (IPM) program. Golf course superintendents and turf care specialists have firsthand knowledge of how adequate turf aeration is beneficial in the short term, as well as in the long term, for a healthy stand of turf. Similarly, having oxygen adequately circulated throughout your pond’s water column will contribute to a healthy and balanced aquatic ecosystem.
Just as the roots of the turfgrass on your greens, fairways and tee boxes need adequate air exchange, beneficial bacteria occurring naturally in ponds and lakes also need oxygen to thrive. Aeration specifically benefits your water body by eliminating thermal stratification, preventing fish kills, reducing the nutrient load and eliminating foul odors from non-beneficial bacteria.
One condition that can affect the health of your lake or pond is called thermal stratification. When this occurs, it can lead to dissolved oxygen (DO) fluctuations in the water column that can be detrimental to aquatic life and the pond ecosystem. Thermal stratification of a pond or lake in the summer is a naturally occurring process where the top layer of warmer water (epilimnion) forms above a layer of cooler water (hypolimnion). The cooler layer of water is unexposed to atmospheric air and essentially suffocates the bottom half of the pond. As the oxygen depletes, ammonia and nitrite levels increase, and within a few months, many ponds reduce their living space by 50 percent. Thermal stratification can also occur in the winter.
Stratification can be mitigated at any point in the year with the addition of aeration. Adequate aeration circulates the pond’s water column, creating a uniform temperature and water density, from the top to the bottom of the pond. This, in turn, allows oxygen to enter the water column by way of the atmosphere at the pond’s surface and be circulated to the bottom of the pond, increasing the dissolved oxygen concentration in the water column.
Have you or another superintendent you know ever experienced a fish kill? It is a shocking symptom of an unhealthy pond ecosystem and undoubtedly raises a lot of questions. Fish kills occur naturally when a pond without proper aeration becomes stratified and then the upper and lower layers are suddenly mixed.
This is typically caused by a heavy rain event or high winds that mix the lower oxygen-deficient layer with the upper layer. When this happens, it lowers the overall dissolved oxygen concentration in the upper layer where the fish are living in the warmer months and causes a widespread fish kill. Proper aeration year round will eliminate the chances of a pond stratifying and prevent the dissolved oxygen from lowering to lethal levels.
If you have a problematic pond on your course that regularly has pond algae and/or aquatic weed problems, you may have been advised that the pond requires aeration to help promote the “good” or beneficial bacteria. Beneficial bacteria are naturally found in lakes and ponds and are responsible for breaking down organic matter being introduced into the water body and for metabolizing excess nutrients like nitrogen and phosphorus already available in the water column.
Organic matter can consist of grass clippings, leaves, limbs, sediment and waste created by aquatic life. Organic material is loaded with phosphorous and nitrogen that feed algae blooms and aquatic weed infestations. The majority of this nutrient-loaded organic material can be found in the sediment and lower layer of a stratified pond, where there is little to no oxygen and the break down of the organic material will be slow to nonexistent.
Beneficial bacteria need oxygen to be productive and to breakdown the existing nutrient and organic load. The slower these beneficial bacteria are at breaking down the organic load will directly result in more nutrients such as phosphorous and nitrogen becoming available to the algae and aquatic weeds in your pond.
When a pond is adequately aerated, the beneficial bacteria are very productive, thus reducing the nutrient load faster and resulting in less phosphorous and nitrogen available to the algae and aquatic weeds found in your pond. By encouraging these natural processes through proper aeration, you can typically reduce the amount and frequency of algaecide and aquatic herbicide treatments that might otherwise be required to maintain your waterbody. Many pond owners find that there is a long-term cost savings in reducing aquatic weed and algae treatments by adding aeration. In addition to aeration, your lake or pond management company might recommend adding additional beneficial bacteria to give a troublesome pond the boost that it needs to maintain a healthy water quality.
Aeration is also a solution to a foul “rotten egg” odor coming from your pond. This type of odor is caused by nonbeneficial bacteria in the pond that thrive in anoxic (no oxygen) environments. These anoxic-loving bacteria create hydrogen sulfide gas as a byproduct. Getting oxygenated water into these areas will eliminate the production of this gas and improve the beneficial bacterial production and balance. The introduced dissolved oxygen to the water and sediment will help the beneficial bacteria outcompete the anoxic, foul-odor-producing bacteria. This will improve the decomposition rate of the organic material and get rid of that “rotten egg” smell.
Depending on your pond’s characteristics, there are two types of aeration to consider: a fountain surface aerator or a submersed bottom diffused aeration system. While both are great sources of aeration for your pond, the depths, shape and size of the water body will play a significant role in determining the best type and size of the aeration system you will need.
Generally, floating fountain surface aerators aerate more efficiently in shallower water (with depths of three feet or less), while submersed aeration systems will be more effective in deeper ponds (eight feet or more). For the ponds that fall in the three-to-eight-feet range, other factors such as the pond shape, symmetry or size could determine the best option.
Floating fountain surface aerators are ideal for symmetrical ponds, while a submersed aeration system or multiple surface aerators are required for non-symmetrical ponds. The size of the pond will determine the size of the unit or system. Consult with your local lake and pond management company when deciding which will be a good fit for your pond, and remember that you can always use both for optimal results.
Contact the experts at 888-480-LAKE (5253) for all of your lake, pond and fisheries management needs.
Brad Harris is a Forestry Biologist and Aquatic Specialist with SOLitude Lake Management. Since 1998, SOLitude Lake Management has been committed to providing full service lake and pond management services that improve water quality, preserve natural resources, and reduce our environmental footprint. Services are available throughout the Eastern United States. Fisheries management consulting and aquatic products are available nationwide. Learn more about SOLitude Lake Management and purchase products at www.solitudelakemanagement.com.