Ecology of a Pond

This is an overview of the natural processes of an earthen pond, and the proper maintenance for a healthy pond.

Introduction

Pond ecology is best defined as the interaction of pond life with the environment that exists in the pond. A nutrient-rich, shallow pond with limited water flowing through it will become filled with algae and aquatic plants. Due to low oxygen levels, there may be little animal life present. In contrast, a freshly created, deep, spring-fed pond may also have little animal life due to low temperatures and a lack of food supply.

All ponds will age. A pond starts with water, little nutrients, and not a lot of animal life. Over time, the pond will increase in nutrients through a process called eutrophication. The additional nutrients will help with the growth of aquatic life. When these organisms die, their remains decay in the pond which releases the nutrients it took to grow them back into the pond water, thus keeping the lifecycle going.

An accumulation of material that resists decay will eventually fill up the pond and become a bog which resembles dry land. You want to slow down this process as much as possible. Here are some ways that you can achieve this.

Essential Nutrients

Growing aquatic life requires the four elements of carbon, oxygen, nitrogen, and phosphorous. Though it takes more than just these elements, there needs to be an abundance of them. To avoid the rapid aging of your pond (eutrophication), the levels of nitrogen and phosphorus need to be lower. Animal exposure to the water supply of your pond should also be restricted to limit the addition of nitrogen and phosphorus from animal waste.

Possible Buffers

Maintenance of vegetation in all areas where water needs to flow in order to reach the pond is essential. These buffers will slow the water down and filter it. When water is moving slowly, it causes a drop in sediment. Keeping sediment out of the pond will help prevent it from filling and becoming shallow. This directly contributes to keeping the pond from turning back into dry land. Aeration for deeper ponds are also cooler ponds, and the growth of organisms is slowed in lower temperatures. In conclusion, a buffer area helps maintain conditions that help slow the aging process of the pond.

Sedimentation Pools

Another method to keep sediment out of a pond is to provide a shallow pool at the inlet of the pond. Water flowing through this pool can drop sediment on its way to the pond. This pool should be small enough that it can easily be cleaned with a backhoe from the shore. A sedimentation pool is especially useful for sediment removal.

Limiting Fertilization

Whenever possible, decreasing the use of fertilizer on turf in the watershed area of a pond is beneficial. One of the reasons is because plant growth is efficient with the use of fertilizer elements. Applying fertilizers at appropriate rates will cause some elements, like nitrogen, to be unused and moved off-site. Reducing fertilizer rates will lower the amount of elements that move off-site.

Maintaining an Ecological Balance

Ideally a pond requires a complete and balanced food web. First, planktonic algae must be present in an amount that is enough for feeding zooplankton. The zooplankton will then be consumed by smaller fish and aquatic insects, and then they become food for larger fish. Then, the larger fish are prey for raccoons, bears, and fishermen.

The higher plant community is another part of ecological balance. Many plants are detrimental to the food web just described. From a pond owners perspective, a pond with a lot of vegetation lacks attractiveness, interferes with swimming, boating, and fishing. There are also issues for aquatic life. There are some aquatic plants that provide shade, hiding spots for small fish, habitat for aquatic animals and insects, and food source for some fish and animals. When the vegetation becomes overgrown, the angler’s hook gets tangled, and the bait is not as visible to fish. The excessive vegetation not only hides the bait, but it hides the prey making fishing unsuccessful.

Here are some other examples of excessive vegetation and the problems they can cause. Ponds that are completely covered with water lilies or lotus will block out sunlight, preventing the growth of any other vegetation underwater. There won’t even be sufficient light to grow planktonic algae. This will become an unproductive pond except for lilies. 

Another example is having too much duck week or water meal. When the entire pond surface is covered with these plants, like lilies and lotus, light cannot reach to sustain life beneath the surface. These plants deplete the water of oxygen because they become a barrier between the water and the atmosphere. As a result, the pond will become oxygen-deficient to a level that will cause fish to die.

However, you can eliminate too much vegetation or remove beneficial plants along with the targeted weeds. This is something to keep in mind when doing weed control in ponds. Some methods are for treating the pond in parts over time. For example, the use of mechanical methods or the use of grass carp to keep things “pruned up” as opposed to wiped out. The use of a surface pond aerator will also reduce weed growth.