By Dino Pezzimenti

It is rare to find a lake or a pond that does not have a cloud of green or stringy pond scum in it. But this is not just an eyesore; it has become an issue that can no longer be ignored.

The cloud of green is a form of algae. The green cloud (generally green, though it can be other colors) is called an algal bloom. Many of these blooms have millions of algae cells per cubic centimeter. As long as there is enough food, carbon dioxide, and sunlight the algal bloom will grow. These algae, also called phytoplankton, are a key component in the food cycle. They are necessary to sustain life as they supply oxygen and are a food for higher forms.

The stringy pond scum are also algae and sometimes called pond moss. Unlike the phytoplankton they are of little benefit.

Algae have increasingly been causing damage to the ecosystem. Some types of algae release toxins that are a poison to wildlife and, indirectly, to humans (e.g., shellfish poisoning) while some forms are useful (e.g., food for human consumption, fertilizer, livestock feed, etc.). But even the useful algae contribute to a problem when they increase in number.

Algae produce oxygen during photosynthesis which, since sunlight is required, occurs only during the day. At night the algae use oxygen so the large algal blooms will obviously deplete more of the available pond/lake oxygen during the night. Also these blooms block the sunlight and limit water contact with the air thus also reducing the oxygen. But the biggest problem occurs when the blooms die.

After the blooms die they decompose. This decomposition requires large amounts of oxygen. The decomposition also releases nutrients and carbon dioxide into the water. This release is required as part of the natural cycle to assure conditions for future phytoplankton to develop. But an excessive release will cause an imbalance in this cycle and that is where the problem occurs.

Increased oxygen depletion causes asphyxiation of fish and aquatic plant life and the body of water starts to die. This process is called eutrophication (the term eutrophication actually refers to an increase in nutrients, e.g., phosphorus, in an ecosystem and may occur in water or on land.)

The algae alone are not causing the problem and can even be viewed as an indicator of the problem severity. Algae feed on nutrients in the water, so as more nutrients are made available the algae multiply. This increase can be easily recognized in most any body of water. The main culprit nutrient is phosphorus.

Phosphorus is crucial for life as an important component of DNA, RNA (ADP, ATP) and cell membranes. Conversely, though, the organic forms of it can be toxic and, as such, were used in weapons (incendiary devices) and poisons (rat poison, herbicides)

Phosphorus is very reactive so it is not found as a free element and unless it is carried as part of a sediment particle (dust), it is not found in the atmosphere.

Phosphorus is most prevalent as a phosphate (a phosphorus atom with varying numbers of oxygen atoms attached to it) with orthophosphate (one phosphorus atom with four oxygen atoms attached) predominating. Phosphates are found in rocks, sediments and ocean salts. Natural forces, over time, or man-made processes in a short time, remove the phosphates from the rocks, sediments, and ocean salts and free them for use. The freed phosphates then enter into the natural phosphorus cycle.

As stated previously phosphorus is not found in the atmosphere so the phosphorus cycle is limited to land and water. And, even though phosphates move quickly through plants and animals it is one of the slowest cycles (it is not carried in the atmosphere). The phosphorus cycle is complicated but basically the cycle is: phosphates are nutrients (food) for plant life, herbivores feeding on the plant life absorb the phosphates, carnivores who feed on the herbivores absorb the phosphates, the carnivores die and decay releasing the phosphates and the phosphates start the cycle anew. Plants or herbivores dying naturally and decaying will also cause the phosphates to release as will urination and defecation. Over time manmade processes have caused an imbalance to this cycle by releasing excess phosphates to it. These excess sources of phosphate need to be controlled by consumers, industry, and government.

Phosphates are used in fertilizers and detergents and these two sources have been targeted as the main contributors. Phosphates in detergents have decreased due to bans and consumer choices yet the phosphate pollution problem continues. Removing phosphates from detergents is beneficial but it is not the only action that should be taken.

Lawn clippings, dead leaves, septic systems, and pet waste are a few examples of nutrient pollution that are caused directly by consumers. Lawn fertilizers containing phosphorus WILL NOT cause nutrient pollution if the manufacturer's directions are followed. Over fertilization and the careless overspray onto impervious areas (roads, etc.) cause the nutrient pollution.

But the biggest contributors to nutrient pollution, by far, are from agriculture (fertilization), municipal waste discharge (raw sewage), and industrial waste discharge. Local, State, and the Federal governments need to self regulate and legislate controls of these nutrient discharges into the environment. It is past the time to act. For more information contact Environment 21.

About the author: Dino Pezzimenti has been an engineer for Environment 21 Global Stormwater Solutions, LLC for the past two years. He has an M.S. from Kettering University and previously worked, as an engineer, seventeen years for a USDOE Subcontractor on the