With a growing trend towards dedicating water features as wildlife habitat, turf staff must now find ways of balancing the aesthetic value of a water feature with the challenge of a hazard while preserving the ecological integrity of the pond.
Learning the basics of pond chemistry can help turf staff understand how flora, fauna and human influences play an intricate part in the nitrogen cycle. Here's a basic review.
pH is perhaps the most complicated chemistry topic when it comes to understanding water chemistry. pH is the measurement of free hydrogen ions in water as measured on a logarithmic scale of 1 to 14, with 7 considered neutral. Ponds should be between 5.5 and 8.5, the ideal range is 7.0 and 7.4.
High pH readings indicate that more hydrogen ions have bonded and are part of a molecule, primarily water molecules. Low pH readings indicate more free ions in the water.
To provide healthy pond water conditions for fish, the pond requires ample water molecules with oxygen as well as a reasonable amount of free hydrogen to bind with oxygen at the surface and at aeration points such as water fountains, stream inlets and water falls.
Higher pH readings indicate more hydrogen within water molecules and so reflect the degree of water molecules in the pond. These molecules make oxygen available to fish, plants and aerobic bacteria. The pH in a pond is always changing. Seasonal temperature and aquatic plant growing trends mixed with the constant removal of oxygen by fish and the introduction of organic matter all have significant influence upon water quality.
The decomposition of organic matter, also known as nitrogenous waste, by aerobic or oxygen using bacteria generates the waste product ammonia. If a pond is high in ammonia there are either too many fish present (fish produce waste high in ammonia), there is a low concentration of nitrosomonas bacteria, or there is an outside source of ammonia leaching into the water table. Often when fish are seen “gasping for air” on the surface there is either low dissolved oxygen in the water, a low pH, or the presence of ammonia or nitrite. As soon as you have ammonia in the pond, the nitrogen cycle becomes a major player in the state of your water quality.
Aerobic bacteria, or nitrosomonas bacteria, use oxygen on the ammonia and produce the bi-product nitrite. Nitrite can be deadly to fish, even small amounts cause a suppressed ability to carry oxygen in its bloodstream. It is important that nitrite is then worked on by another aerobic bacteria called nitrobacter which produces another by-product, nitrate. Nitrates are relatively harmless compared to ammonia and nitrites. Nitrates are a source of food for plants and can easily be removed by the presence of aquatic plants.
Okay, so in the real world this means that once you have organic matter decaying and releasing ammonia you then need oxygen present in order to convert it into nitrates. Plants produce the oxygen during the day as part of photosynthesis and continue to use the nitrates as food, thus creating more biomass which prompts the food web to grow. Eventually your pond could reach a stage where there is so much vegetation that it will start to stunt the fish growth.
What many golf courses will do is physically remove the aquatic plants. This has the least negative effects on the ecosystem as there must be an adequate amount of oxygen in order for the plant population to grow so high. (Note: aquatic vegetation, even algae, is high in nitrogen and can be an excellent addition to your compost).
Another control measure is the use of Koi. These "freshwater Manatees" are great grazers but can sometimes cause trouble down the line. If populations are allowed to grow beyond the ponds capability toproduce aquatic vegetation then there will be a lack of vegetation, thus a possible toxic level of ammonia. This is the reason why most Koi ponds have aerators and fountains to help add oxygen to the surface profile of the water.
Koi are a member of the carp family, which is known to practically beach themselves and eat the grasses along pond banks when there is limited aquatic vegetation. This reduces bank stability and can cause a release of sediment into the water which “shades” the pond bottom and further prevents plant growth.
Balancing your ponds N cycle can be tricky, but will pay off in many ways. Good water quality is important to supporting biodiversity within any ecosystem.
It is important to remember that pond chemistry is always changing. The bacteria necessary for the nitrogen cycle to work are dormant until the water temperature reaches 55 degrees Fahrenheit. This causes a fluctuation in ammonia levels during the cooler months of the year.
Ok, since you’re now a chemist lets see how this all relates to common golf maintenance activities. Regular maintenance regimes can have an influence on water quality, and each turf employee can do their part in protecting water quality.
Buffer zones should be implemented around all water bodies whenever possible. Buffer-zones provide many significant functions:
- They are able to slow down surface water flow and help filter run-off (fertilizers, loose soils and mower clippings)
- Plant roots provide stability to the pond banks which helps to prevent erosion. Loose sediment can obstruct fish spawning and can enter fish gills making it difficult for them to breath.
- If planted with showy material they can offer an aesthetic value to the course, contributing to the natural character of the property.
- On ponds that serve as a hazard, buffer zones can have physical characteristics (such as varied height or pockets of shrubs) that serve as a point of reference for where a player’s ball tends to enter the water.
- Native plants contribute to the overall habitat value of the property. A naturalized pond bank supports a healthy transition from riparian/meadow species, to wetland herbaceous species at the partially, fully submerged and aquatic levels. Wetland species help oxygenate the water.
It is best to have a no-spray zone policy in these areas, where fertilizers and chemical controls for pest management are not used within a pre-determined distance that reflects soil texture and grade of the site. If thresholds for disease are surpassed then minimal spot spraying or alternative mechanical controls (such as removing weeds by hand) should be used within this zone.
It is important to visually inspect ponds on a regular schedule throughout the year. Pond monitoring is an important part of any IPM program and should be part of the regular scouting activities. Approach pond monitoring in the same way that monitoring is done for turf. Establish a threshold for surface plants, algae and Koi. Then develop control methods for each that are suitable for aquatic ecosystems. Record your findings and review each season.