Is it The Blob? No, it's a bryozoan colony

Education, Environmental, Sound Rivers

Posted on August 5th, 2021

This bryozoan colony was spotted this week in Barton Creek, at the southern end of Falls Lake, north of Raleigh, by a Sound Rivers’ Swim Guide volunteer.

Have you ever seen a gelatinous blob in local waters and wondered what it could possibly be?

While most people would guess it’s some type of algae or fungus, or even freshwater jellyfish or fish eggs, it’s likely a colony of bryozoans, or “Moss Animals.” Though the individual animals are tiny (less than 1/25 of an inch), they form colonies that can vary greatly in number, form and size.

Most Bryozoan species are marine animals — of almost 5,000 species, less than 90 have been identified in freshwater, and only 24 freshwater species have been found in North America.

In local waters, bryozoans can form jelly-like “green blobs” on underwater vegetation, branches and other structures or they could be found in free-floating round colonies. What you see on a colony’s surface — small, visible rosettes — are actually groups of 12-18 individual bryozoans.

Bryozoans feed on algae, so they can be considered filter feeders and may, in some instances, increase water clarity. Each bryozoan attached to the colony is clear or opaque, and it’s thought that the reason colonies look green is because of the algae each individual has ingested.

If you ever find one, and have a magnifying glass handy, a closer look of a bryozoan colony can be an eye-opening, and unique, experience.

Photos are courtesy of Linda Minetree and Sound Rivers’ Swim Guide volunteer Susan Baker.

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