Fertilizer Effects on Freshwater Algae

Transportation of Fertilizers

• Fertilizers make their way into bodies of freshwater in several different ways, from residential lawns and gardens to commercial farms and feedlots. Improperly applied fertilizers mean that there is too much nutrient content in the soil, and it cannot be used by the plants it was intended for. There nutrients can be washed away by rains, funneled into groundwater and then joining up with runoff from other areas. Nitrogen is extremely water-soluble, and if not used it will quickly seep down into the groundwater with other water molecules; rainwater or storms are not even required to send these nutrients into freshwater areas.

  Nutrients like the nitrogen and phosphorus deposited by fertilizers can bond with the soil particles if not quickly and efficiently used by plants. Once these soil particles dry out, they can easily be picked up by the wind and carried for long distances.

Algal Blooms

• Algae always exists in freshwater environments, where it plays an important role in returning oxygen to both the water and the air. When nutrients are introduced to the water from fertilizers, the algae experiences a rush of the nutrients needed for it to reproduce. The algal cells will continue to multiply as long as there are nutrients available, and this growth can result in the development of algal blooms. Some algal blooms occur naturally and disappear quickly, but those fueled by fertilizers can continue to develop as long as there are nutrients unused.

  Harmful algal blooms occur when the algae affected by the fertilizer release toxins into the water. This occurs when the freshwater algae affected is blue-green algae; there is a similar effect in the marine environment when some types of red algae form red tides.

Consequences of Algal Blooms

• Blue-green algae normally releases toxins into the water, but when there is a small amount of algae present, the toxins are dispersed throughout the water. During harmful algal blooms, the concentration of the toxicity increases dramatically. People exposed to the high concentration of toxins can suffer from allergic reactions, severe gastroenteritis, dizziness, numbness and other neurological effects. Dogs who swim in water contaminated by these algal blooms are at a high risk for developing severe neurological impairments that can quickly lead to death. The same toxins kill fish, birds and other wildlife that lives in the waters.

  Normal algal blooms -- those that are caused by a type of algae that doesn't release a toxin -- can still be dangerous. Fertilizer-fueled algal growth can easily cause a covering of algae so thick that the sunlight cannot reach plants and animals below the water. This situation can lead to the death of an ecosystem if not remedied.

Prevention

• Proper application of fertilizers is key to the prevention of these devastating algal blooms. Residential areas can also contribute to the problem, so proper fertilization of backyard gardens and lawns is just as important as responsibility on a commercial scale. Follow the directions on fertilizer precisely.

  Be sure that the lawn or garden requires fertilization. Some soils are naturally rich in all the nutrients needed for plant life, so there may not be a need for some types of fertilizers. Most local college extension offices or environmental agencies have the equipment necessary to do a soil test to determine the nutrient content of soils; this test will help determine whether or not fertilization is necessary and how often it should be done.