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Bill Hancock,Marine Biochemists:Benefits of Aeration in your Pond Bottom
Aeration and Its Benefits to Your Pond Bottom
By Bill Hancock, Marine Biochemists.com
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There is no doubt that properly aerating a pond or lake provides many benefits important for supporting fish, regulating nutrients, and for increasing the general health of the aquatic environment. However, there are some misconceptions concerning aeration’s actual effect on the bottom “muck”. Contrary to some claims of being a “magic bullet” aeration cannot on its own solve all of a pond’s soft sediment or “muck” problems. Aeration can, however, be a key component in accelerating the natural or enhanced digestion of soft sediment if certain watershed controls are put into place.
Muck is basically a complex mixture of organic compounds originating from erosion, run-off debris, windblown “dusts”, leaf litter, plant decay and animal wastes. Anything from grass clippings to goose droppings add to the loading of organic soft sediment. The levels of the build-up of organic muck depend on the age of the pond, erosion, drainage patterns into the pond, disruptive activities around the pond including development of shoreline or drainage areas, fertilizer use in drainage areas, waterfowl populations, etc.
In almost every pond, organisms that feed upon organic sediment are initially aerobic or oxygen-requiring bacteria. In ponds without aeration, aerobic bacteria thrive until dissolved oxygen levels near the bottom sediment water interface (SWI or “where the muck meets the water”) become depleted. Once conditions turn anaerobic (devoid of oxygen), anaerobic bacteria take over the SWI niche. Anaerobic bacteria are far less efficient at breaking down organic matter than aerobic strains, and lead to the production of noxious decay gases such as hydrogen sulfide and methane.
The addition of aeration aids in maintaining dissolved oxygen levels near the SWI. Ideally, the dissolved oxygen level near this interface should be maintained 2 ppm or higher at any given time, thus allowing sustainable aerobic decay of the muck. Proper aeration accomplishes this task by circulating a pond’s entire water column over a relatively short period of time allowing oxygen to dissolve into moving surface waters exposed to the atmosphere, and then distributes these oxygen-enriched waters to bottom areas. This circulation pattern also allows organic decay gases to “gas-off” into the atmosphere.
The overall effect of proper aeration on the bottom muck is going to depend on several influencing factors. First, if the input of organic debris exceeds the consumption of the existing muck, muck will continue to accumulate. The converse is also true. If organic debris inputs are less than the consumption of muck, then levels of muck in the pond will begin to decrease. In other words, if
one can keep the debris from entering the pond, one can make headway on what is in the pond. Several watershed management techniques that accomplish this task and enhance aeration’s ability to reduce organic sediment include • Leaving an uncut buffer zone of vegetation around the pond • Limiting yard and garden wastes from entering the pond • Discouraging waterfowl to congregate in or around the pond • Removing debris/organic materials from the pond Physically removing organic debris such as branches or leaves from a pond can enhance aeration’s effect. This type of debris eventually breaks down adding to muck accumulation. If branches or trees have been added for fish structure, consider replacing them as they age with structures created from plastic drain tile or other substances that do not undergo organic decay. Dredging is an immediate way to reduce soft sediments and debris, but such projects are limited due to suitable sediment disposal sites and significant costs. If good watershed management practices are put in place, aeration can be expected to reduce muck of a period of several years. Bioaugmentation accelerates this process, but its impacts will not be seen until a few years after its implementation. In three test ponds serviced by Marine Biochemists - Wisconsin where watershed management was enhanced and bioaugmentation implemented, measured soft sediment levels were noticeably reduced by several inches during the first season. In the Twister TA-22 Diffuser. This is one of second and third years of the program, soft sediment was visibly reduced along shoreline areas. In all three of thethe diffusers that we would use to do ponds, hard bottom was achieved along near shore areas what we talked about in this article. after the fourth and fifth year. The successful results in these test ponds can be attributed to the cooperation of the surrounding landowners and the continuation of programs over several seasons. Unfortunately, other ponds with aeration introduction showed few signs of soft sediment improvements largely due to continual organic influxes outside of adjacent landowners’direct control. Aeration can definitely make a dent in the amount of muck in a pond, but expectations have to be tempered with patience and the importance of long-term control of surrounding influences. Aeration alone cannot magically eliminate a pond’s “mucky” problems, but it is an essential step in halting or reversing soft sediment accumulation. If you have questions or would like to find out more about your pond, you can call Marine Biochemists at 309/452-0461.
247 Broadway • Quincy, IL HOURS: MON-FRI 8am-5pm SAT9am-1pm 217/222-6006
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