Bloom Blues (and greens and yellowish browns…)
A blue-green algal bloom can resemble spilled paint as can be seen in this picture of an impacted waterbody in New York.
An algal bloom is constituted by the rapid increase of algae in an aquatic system. Although there is no hard and fast threshold level cited that determines if a bloom is present, when concentrations of an algal species reach hundred to thousands of cells per milliliter of water an algal bloom is present. Blooms can reach millions of cells per milliliter. Algae can reach bloom levels in fresh or marine water and there are several causative factors, with the most common being nutrient overloading. Blooms can be observed in many colors, the most commonly seen are green, yellowish-brown or red. Bright greenish-blue blooms may also occur, which will be composed of the misnamed “blue-green algae” that is actually cyanobacteria.
More often than not, algal blooms are the result of excess nutrient input into an aquatic body, specifically nitrogen and phosphorus. Although nitrogen will help aquatic plants, they cannot compete with the growth rate and reproduction of the algae, and eventually will die from shading out by huge algal blooms. Increased plant death contributes to the imbalance of the aquatic system; dead plant material feeds bacteria with more food available, bacteria reproduce and use up dissolved oxygen, when dissolved oxygen levels are low fish and aquatic insects cannot survive. The result can be a dead area. Some species of algae produce toxins, which can have impacts on wildlife; if affected water bodies are a source of drinking water, human populations will also feel the impact.
Eerie Conditions in Erie
Last weekend a harmful algal bloom on Lake Erie forced the city of Toledo, OH to ban the use of tap water by its residents who use the water for drinking, cooking and bathing. The ban was lifted by Monday morning, but algal blooms that are harmful to wildlife and human communities are becoming more common in coastal areas and freshwater bodies around the world due to changing weather and climate conditions. Blooms produce neurotoxins which can cause seizures or paralysis in humans, although those effects have most and best documented in marine mammals and birds.
The harmful bloom of cyanobacteria in Lake Erie severely impacted water quality and forced a tap water ban. Warm waters, excessive nutrient loading and the shallow depth of the lake are contributing factors to repeated blooms in the lake.
Hundreds of manatees were killed in Florida when a toxic algal “red tide” threatened waterways, and record numbers of seals and sea lions flooded rehabilitation centers in California due to another bloom earlier this year. Massive fish kills have also been reported due to harmful algal blooms. The algae responsible for toxic blooms like the one impacting water quality on Lake Erie is Microcystis, a cyanobacteria which requires warmer water temperatures and excess nitrogen and phosphorus to grow. Nitrogen and phosphorus can escape from leaky septic tanks and agricultural runoff combined with warming water temperatures, both fresh and marine, are creating the perfect opportunity for alga to take hold and populations to explode.
