Eutrophication – Is Your Lake “Over the Hill?”

Why is the lake greener than it used to be? Where did all this “pond-scum” come from? Why has the lake developed an odor? These may be questions that you have been pondering recently, and a potential answer to these questions is: eutrophication. From the Greek word meaning “well nourished”, eutrophication refers to the process in which lakes become nutrient enriched and filled with sediment. Eutrophication is a natural process which usually occurs over vast periods of time, however it can be greatly accelerated with activities such as land development, industrial, agriculture, and wastewater disposal.

The most obvious sign of man-made, or cultural eutrophication, is the creation of dense phytoplankton blooms (microscopic, single-celled plant-like organisms) and even worse are blooms of cyanobacteria, which produce lethal toxins. These blooms can be foul smelling, reduce water clarity, and be harmful to the water quality. In some cases, depending on the nature of species present, they can produce toxins which are harmful to wildlife, pets, and people. These alga species usually thrive in water that is high in nutrients, particularly phosphorus and nitrogen. These nutrients are becoming more abundant in our waterways, creating Harmful Algal Blooms (HABs) and disrupting many ecosystems. To reduce the likelihood of a harmful algal bloom, we need to reduce the levels of one or both of these nutrients. Because nitrogen can be fixed from the atmosphere by several species of blue-green algae, controlling the levels of phosphorus tends to be more effective.

So…how do we slow down or reverse the process of eutrophication?

Reduce the amount of nutrients that flow into the pond or lake.

Nutrients will naturally flow into a pond via erosion and sedimentation. When erosion around a water body occurs, soil is washed into the lake or pond. This sediment typically contains nutrients such as nitrogen and phosphorus which can fuel algal blooms. A buffer zone planted with native vegetation around the lake or pond is a great way to reduce the amount of sediment that reaches the water body. The plants’ root systems catch sediments, and the plants absorb some of the nutrients before they reach the lake or pond. Human activities have greatly accelerated the nutrient loading of many bodies of water around the world. The overuse of fertilizers and improper sewage treatment/disposal are the main causes of cultural eutrophication. This artificial increase in nutrient influx has led to the need for development of technologies that can sequester nutrients, mainly phosphorus. Research and development have led to the commercial manufacturing of some impressive products that can filter soluble reactive phosphorus from moving water. Such products can be installed or applied strategically within a lake or pond to slow down or stop phosphorus from entering a waterbody.

Reduce the availability of the nutrients already in the lake or pond.

Nutrients that have already made their way into the waterbody will tend to be cycled through algae, plants, animals, bound in sediment, and freely reactive in the water. Removing excess nutrients tends to be more difficult than reducing the amount coming in, but advances in technology are making this proposition much easier.  Once again, technological advances have led to the development of specialized products that contain a phosphorus binding mineral that can be applied directly to a waterbody. This process serves to bind free reactive phosphorus rapidly and permanently within the water column, making it unavailable to further produce nuisance vegetations.

As an individual, how can I help reduce nutrients loading in our Lakes, Ponds, and Streams?

• Reduce the use of lawn fertilizers. Read the label of fertilizers carefully and only use the amount necessary.
• Wash full loads of laundry in washing machines.
• Only use low phosphorus or phosphorus-free detergents.
• Collect and properly dispose of pet feces.
• Compost garden and food wastes.

Water is our most important and abundant resource. Without proper care and diligent stewardship, we stand to lose everything.