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Resources

THE GOOD (AND BAD) OF GREEN

In previous Lunchtime Lessons, we expressed the importance of having the correct balance of nutrients in a reservoir. The lesson noted that clear water isn’t always an indication of a healthy reservoir, but too many nutrients can also be harmful. As the weather starts to warm and the sun is shining, the waters you fish will start to look more green, but you may be asking, how do I know the difference if the water is harmful or not?
THE GOOD (AND BAD) OF GREEN
Normally green tinted water is a sign of a productive waterbody with a great phytoplankton bloom. Phytoplankton is a critical link in the food chain of fish, including bass, crappie, bream, walleye, and catfish. However, not all green water is caused by phytoplankton blooms. Some green tinted water is caused by cyanobacteria, also known as blue green algae. Last summer, the topic of cyanobacteria and the potential for Harmful Algae Blooms (HABs) became a bigger topic in Central Arkansas. The heavy late winter and spring rains caused an influx of nutrients to wash into lakes. The additional nutrients combined with the correct temperature range and abundant sunlight created ideal conditions for cyanobacteria to thrive. Unfortunately some of the cyanobacteria that was present in these lakes started releasing cyanotoxins and became HABs. Cyanotoxins have the ability to be harmful to humans, pets, and wildlife. The exact reasons why this happens is not fully understood but the addition of nutrients (phosphorus and nitrogen) is considered a major factor.
While on the water, at first glance, it can be difficult to tell the difference between a good, healthy, phytoplankton bloom and a potentially harmful algal bloom. All blooms cause water to appear green, but at closer glance, can be different in appearance. Blooms that cause green water fall within three categories:
THE GOOD: A phytoplankton bloom that is beneficial to a pond or reservoir will make the water appear green, with visibility usually less than 16-inches. The greenish color will appear, mostly, uniformly in the water. These blooms are the result of phytoplankton appearing in the water column, which serve as the base of the food chain for the fishery. A good bloom will not affect the smell or taste of the water, and is safe for humans, wildlife, and pets.
THE ANNOYING: Another typical of algal bloom is known as a nuisance algal bloom. These are usually caused by plants (or even pollen), and are not necessarily dangerous, but can simply be annoying and reduce the aesthetic of a waterbody. A good rule of thumb is if the green material looks like something you can scoop or grab out with a pitchfork, it is likely not a HAB. Nuisance algal blooms can appear stringy, like filamentous algae (see left image).
THE WORST (AND HARMFUL): The final type of blooms are the HABs (pictures below). As stated above, these are caused with the right combination of sunlight and nutrients. Harmful algal blooms appear shiny or oily, almost as if paint was spilled in the water. Some HABs can cause water to have a bad smell and can alter the taste as well. Below are links to more resources about identifying HABs and other algal blooms. If you would like to report a nuisance or harmful algal bloom, please contact the Arkansas Department of Environmental Quality or you can fill out THIS FORM.
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