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Bryozoan

AUBURN UNIVERSITY, Ala. – For those that have been to the lake, there is a real chance they stepped onto the dock’s ladder and felt something strange. The unknown can be scary. Is it fish eggs, a weird plant, brains or a scene from Mars Attacks? Fortunately, this strange substance is something of an Earthly nature. It is a bryozoan.

Appearance

While they might look like the aliens from Mars Attacks, bryozoan anatomy is quite interesting.

“The individual zooid heads form together with other zooids to create the gelatinous matrix,” said Rusty Wright, an aquatic resources specialist with the Alabama Cooperative Extension System.

The gelatinous colonies that form somewhat resemble a brain, with their round structure and rosette-like patches of brownish purple on the outside. These colonies are rather firm and can grow to the size of a softball up to three feet in diameter.

“These specific bryozoans are colonial, meaning that they stick together to thrive,” Wright said. “However, not all bryozoans are colonial, as other similar species live by themselves.”

The heads also have tentacle like structures at the mouth, which create a water circulation to filter out bacteria and small algae for food. With features like these, no wonder people assume they are something from a Tim Burton film.

Where are bryozoans found?

Bryozoans (Pectinatella magnifica) are actually colonies of many animals. Much like their saltwater cousin, coral, they have many separate bodies surrounding their gelatinous insides. They can be found in freshwater bodies of water across the United States, mainly in the eastern part of the country.

Once out of the larval free-swimming phase, bryozoans attach themselves as a group to a hard substance, such as a stick or even docks and ladders. These colonies can eventually break free and float about the pond or lake.

Impact on Water

Overall, bryozoans are considered to have a fairly neutral impact on lakes and rivers. While there are no major adverse effects, there are some positives and negatives to keeping them around.

Positives

  • They can help clear up a lake by consuming suspended material.
  • Their presence is a sign that the lake or river is healthy because they are usually only able to reproduce and form in healthy freshwater.

Negatives

  • They can clog a drainage intake.
  • They can attach to floats or other buoyant objects like fish cages. As they grow, they can cause these items to sink.

Removal Methods

Since these creatures do not have major positive or negative effects, most people leave them be. However, if they become a nuisance on a structure, like a boat, dock or ladder, Wright said there are a few ways to remove them.

  • Break them apart from the structure. Since bryozoans are made of many different heads, this will not kill the animal. People can release it into the water, and it will just float around the lake.
  • Use antifouling paint. Copper kills essentially all marine life. If it is inconvenient to break them off, one can apply an antifouling paint to the ladders or other structures to prevent the bryozoan larvae from attaching. This paint is usually used on the bottom of boats to keep aquatic life from growing on them.
  • Copper sulfate granules. One can also use copper sulfate granules directly on the colony to kill them.

More Information

For more information about bryozoans, or other aquatic topics, visit www.aces.edu or contact one of the Alabama Extension aquatic resources professionals across the state.

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