Spring Pond Algae Invasion

Reader Contribution by Kenneth Rust
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by Kenneth Rust

This time of year as I talk with pond owners all over the nation, there are a full range of conditions. My friend Mike from Tennessee, referring to Baton Rouge, said, “Yep, I imagine the birds are already a-whistlin’ down there.” And so they are. Just this week, I swam in a pond for the first time to help a friend create spawning habitat for his fish. I also saw my first two snakes. In Louisiana, spring has arrived. Quite a contrast to my Northern friends, who have suffered through the “Polar Vortex,” which seemed like a whole season instead of an event. One thing for sure, temperatures are warming and spring is on the way. Warmer temperatures for pond owners always means algae production. While we welcome spring, it is also the season for the not-so-welcome invasion of algae.

The 3 Types of Pond Algae

Three types…Now these aren’t the only three types of algae, but these are three categories that will likely be important to you and your pond biology.

Green Phytoplankton: This algae is single-cell, free-floating algae. It is most often noticed as a green color to the water. It can range from a just a greenish tinge to pea soup. Green algae is productive and useful in the pond. Assuming you have sunny weather, it is a net producer of oxygen in the water. It is also the basis for the food chain for a bass-bluegill system, and contributes to other food webs as well. While it is a “good” algae, it can overproduce and the population eventually crashes, if the pond is too rich with nutrients. The level of production desired is also a matter of personal preference, depending on your goals for the pond. If you want to use the pond for swimming, typically, you will prefer little algae production of any kind.

Blue-green: This is the “mutant, evil twin” of green phytoplankton. Blue-greens are difficult classification for biologists. Cyanobacteria: Half-algae, half-bacteria. Blue-green algae are a deep green color, although they can vary from green to distinctly blue. Since it forms dense colonies and floats, it looks like someone spilled green paint on the water. The dense floating nature of blue-green algae shades out the green phytoplankton below, which reduces oxygen levels. Blue-green algae are not net producers of oxygen through photosynthesis. They are associated with high nutrient levels in the pond, and produce bad odors, off-flavor in fish, poor oxygen conditions, accelerated sludge accumulations, and they have been associated with toxic reactions in both pets and humans.

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