By: Nicholas Lorge
Aquatic Field Biologist
As an owner of a pond, you may be curious about what causes algae blooms and vegetation to become a problem. Many factors are at play, but one of the most prominent is related to the amount of nutrients available for use by algae and plants. Similar to terrestrial plants, both algae and aquatic plants require basic nutrients to grow and thrive. For example, phosphorus is a common nutrient needed for all plants and acts as a catalyst for growth in many aquatic plant and algae species. For this reason, it is important that nutrients remain in balance to ensure the waterbody remains in good health.
Without a doubt, phosphorus is the most important nutrient within aquatic ecosystems. Excess phosphorus can be a major problem, oftentimes causing unwanted and even toxic algae blooms within ponds and lakes. For a pond to remain in good health, it is imperative that phosphorus levels are under control and don’t reach eutrophic levels, which translates into a very unhealthy pond. The battle against the eutrophication of ponds is constant, as nutrients are continuously entering aquatic environments from the surrounding land.
Nutrients can be brought into waterbodies from multiple reasons, but most commonly, nutrients are carried into a waterbody through runoff from stormwater and also melting snow. Soluble nutrients like phosphorus and nitrogen get into the water as the water runs off of roads and lawns, eventually flowing into a pond or other waterbody. For this reason, lawn fertilizers and salted roads from the winter months are generally a negative for ponds and lakes that accumulate high amounts of water runoff. Other means of entrance for nutrients come from groundwater, recycled plant and algae material, and also animal waste (geese). With all of these different means of entrance into a waterbody, attempting to reduce the amount of nutrients that enter the waterbody is a key factor to having a healthy pond or lake.
When a water body is already loaded with high amounts of nutrients, there are still means of reducing the total amount of nutrients and ultimately restoring the pond. The first and most common method of reducing nutrients within a waterbody is the use of beneficial aquatic bacteria. Many bacteria species in aquatic ecosystems feed on nutrients such as phosphorus and nitrogen, making it an extremely important tool to use to maintain waterbody health. This method takes considerably longer than other methods, but it is a natural means of reducing nutrients within an aquatic system a maintain balance. Another great option involves nutrient-binding products.
One great product is called Phoslock, and it specifically targets phosphorus within the water column and sediment, and then permanently binds to the molecules. This renders the phosphorus unusable by aquatic plants and algae. This type of application is especially recommended in ponds that contain high amounts of nuisance algae and plant growth on a regular basis. Another good method of controlling nutrients is treating with alum. The goal of these types of products is similar to Phoslock in that the product binds to free nutrients within the water column. Although, unlike Phoslock, this binding process is not permanent, so repeat applications will be necessary to continuously remove phosphorus and other nutrients from the water column.
All in all, phosphorus and other nutrients directly affect the overall health of an aquatic waterbody. Nutrients are continuously entering aquatic waterbodies by means of runoff from roads, groundwater, animal waste, etc. High amounts of phosphorus and other nutrients can lead to both toxic and nuisance algae blooms and a higher amount of nuisance vegetation. For these reasons, it is important to have routine nutrient-reduction applications performed in all ponds and even many lakes.