Algae Bloom

Jennifer Slavens
Algae Bloom

If your favorite lake has ever turned bright green in the middle of the summer, you are familiar with one of the common symptoms of algae bloom.   Algae blooms are caused by a large number of phytoplanktons growing in your favorite lake, and can come in colors from red to green, with green being the most common/familiar.

Algae bloom in Minnesota is generally caused by excess fertilizer from farmland being washed into our lakes and streams.   This excess fertilizer causes the levels of nutrients in the lake such as phosphorus and nitrogen to increase.   Algae growth increases in water that is high in phosphates.   The algae in themselves are generally not dangerous (here in MN).   The problem is caused by the short life span of the algae.   As the algae dies, the dissolved oxygen in the water is used up during the decay process.   When the oxygen is used up rapidly and not replenished, we experience a “fish kill”, or large amounts of dying fish.   Fish require at least 30% dissolved oxygen in their habitat, and decay from an algae bloom can quickly deplete oxygen stores to below this level.

Algal blooms also decrease the amount of sunlight that is reaching aquatic plants, causing those plants to die as well.   These plants typically filter the water, and a loss of them causes more decaying material and additional loss of oxygen within the area.

Much research is being done on algal blooms and how to prevent or reduce them.   As a home remedy, homeowners, especially those in a watershed area, can reduce the amount of fertilizer they use, preventing many of these phosphates from entering the water.   This past February, scientists were able to map the genome of one of the harmful algae species, which will hopefully lead to new ways to fight algal bloom.