Effects of Fertilizer on Freshwater Ponds: What You Need to Know

Anyone who has a pond in their backyard, or is involved in agriculture, may be interested in what happens when fertilizer is added to a freshwater pond. Fertilizers are widely used to enhance plant growth in farms and gardens; however, their effect on the pond ecosystem can be both positive and negative. Although the controlled application can improve the productivity of an aquatic plant, heavy fertilizer runoff may cause unwanted environmental catastrophes, including algal blooms, oxygen depleting, and even fish kills. To establish a healthy or balanced aquatic environment, one must understand how fertilizers interact with freshwater ponds. This paper will discuss the effects that fertilizer produces on freshwater ponds, means minimizing negative impacts of fertilizers can be made, and offer guidelines on responsible fertilizer use.

Understanding Fertilizer and Its Components

Before understanding what happens when one adds fertilizers to a freshwater pond, it is necessary to understand what fertilizers are made of and how each of these components impacts aquatic ecosystems.

1. Key Nutrients in Fertilizer

Most fertilizers contain three major nutrients:

· Nitrogen (N): While nitrogen is essential for plant development, it facilitates photosynthesis and the building of proteins in aquatic plants and algae.

· Phosphorus (P): Stimulates algal and aquatic plant growth; usually the most limiting nutrient in freshwater systems.

· Potassium (K): An essential plant nutrient, but not as important to freshwater ecosystems as nitrogen and phosphorus.

2. How Fertilizer Enters Freshwater Ponds

Fertilizer can enter freshwater ponds through a number of pathways:

· Direct application: Fertilizer applied to fish ponds to stimulate aquatic plant or algae growth.

· Agricultural field runoff: Excess fertilizer from crops washes into the ponds when there is rain.

· Urban and residential: Fertilizers applied to lawns and gardens can be transported to ponds via stormwater runoff.

 Once in the water, these nutrients alter the natural balance of the pond ecosystem, which leads to a set of potential outcomes. Aquatic Ecosystems

What Will Happen When Fertilizer Is Added to a Freshwater Pond?

Fertilizing of a freshwater pond has both beneficial and detrimental effects depending on the rate applied and the method of application.

1. Algal and Aquatic Plant Productivity

One of the first events that occur after fertilizer is introduced into a freshwater pond is that algae and aquatic plants start growing rapidly. Nitrogen and phosphorus are enhancers of photosynthesis; thus, the new nutrients will boost the growth of:

· Phytoplankton (microscopic algae) - These minute organisms form the base of the aquatic food web.

· Macro-phytes (larger aquatic plants) - Species such as water lilies, duckweed, and cattails may benefit from added nutrients.

· Periphyton-Attached algae that grow on rocks and plants, increasing growth rates with nutrient enrichment.

2. The Risk of Algal Blooms

While a moderate growth of plants is beneficial, too much fertilizer input results in harmful algal blooms. This occurs when:

· Phytoplankton reproduces uncontrollably and forms thick layers of algae on the surface of the pond.

· Cyanobacteria, also known as blue-green algae, becomes dominant and releases toxins that are harmful to fish and other aquatic life.

· Water clarity decreases, reducing sunlight penetration and affecting submerged plant growth.

Algal blooms may cause aesthetic problems, such as green scum on the surface, and interfere with the natural balance of the pond.

Oxygen Depletion and Fish Kills

One of the major concerns about what will happen when fertilizer is added to a freshwater pond is oxygen depletion leading to fish deaths. It happens in two steps:

1.High oxygen consumption at night:

· During the day, algae and plants produce oxygen through photosynthesis.

· At night, respiration continues, but no oxygen is produced, resulting in temporary oxygen drops.

2.Oxygen depletion from decay:

· When too much algae die and decay, bacteria deplete oxygen as they break down the organic material.

· A chain reaction is set off as dissolved oxygen levels fall so low, suffocating the living fish and other aquatic organisms-a process called eutrophication.

Fish species such as trout, bass, and catfish show much susceptibility to low oxygen levels, and mass fish die-offs might occur in cases of extreme circumstances.

3. Disturbances in Aquatic Food Chains

Adding excessive nutrients will also disturb the pond's food web in the following ways:

· Giving rise to algal overgrowth, thereby competing with the native aquatic plants.

· Decreasing the availability of habitat for fish, amphibians, and invertebrates that are helpful to the ecosystem.

· Changing predator-prey relationships; rapid growth of algae can diminish populations of zooplankton that feed upon phytoplankton.

Such changes may bring adverse impacts on biodiversity and make it hard for native species to thrive.

How to Reduce Adverse Impacts of Fertilizer on Ponds

1. Use Fertilizer Wisely

· Use fertilizer only when necessary – test soil and water nutrient levels before adding fertilizer.

· Use slow-release or organic fertilizers – these reduce the risk of nutrient runoff.

· Apply during dry weather – Avoid fertilizing before rainfall to prevent runoff into ponds.

2. Create Buffer Zones Around Ponds

· Plant vegetative barriers such as grasses or shrubs that can filtration nutrients before entering the pond.

· Develop wetland buffer zones that absorb and process excess nutrients naturally.

3. Enhance Aeration in Ponds

· Increase oxygen through the use of aerators or fountains, thus preventing stagnation.

· Add floating plants-like water lilies that would shade the pond and reduce undue algae growth.

4. Nutrient Management

· Apply fertilizers at the reduced rate from the adjacent areas

· Use crop rotation or cover crops to reduce soil erosion and runoff

· Install controlled drainage systems that allow for the routing of excess water.

5. Regular Water Quality Monitoring

· For nitrogen and phosphorus in the pond

· For oxygen levels to prevent fish kill

· Observe the algae growth and water clarity as an early warning against eutrophication.

These above management practices will help you effectively use fertilizer without harming pond ecosystems.

Conclusion

What will occur when fertilizers are put into a freshwater pond? It will depend upon the amount used and how it is controlled. A moderate addition of fertilizers will promote plants to grow well, enhance a good aquatic life in the pool, whereas too much nutrition could cause toxic algal blooms, oxygen depletion, and fish kills, tipping off the balance of the ecosystem.

Farmers, pond owners, and conservationists should be aware of such impacts with a view to sustaining healthy freshwater ecosystems. It is, therefore, very important that freshwater ponds be protected from the risks of nutrient pollution by practicing responsible fertilizer use, monitoring water quality, and maintaining natural filtrations. Have you ever noticed changes in any pond following a fertilizer application? Share your thoughts and questions with us in the comments section below!