We found this jelly-like blob at the bottom of the lake, beside our dock, attached to a tree branch. In all my 69 years of cottaging, this is a first for me. No one else I asked on the lake had ever seen one either. Is it the bryozoan Pectinatella magnifica?—Brenda Tryon, Dickie Lake, Ont.
Teamwork makes the Q&A dream work: we reached out to an expert in aquatic ecology at Trent University, who suggested we contact a bryozoology researcher in the U.K., who connected us with Tim Wood, a professor emeritus in the department of biological sciences at Ohio’s Wright State University. Short story short? You’ve I.D.’d the blob correctly.
Bryozoa—sometimes called “moss animals”—are simple, aquatic invertebrates. The species that you found is native to eastern North America. It probably travelled to your lake attached to the feathers of a duck or other waterbird, as a “dormant, asexual, seed-like capsule,” says Wood.
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Bryozoa form colonies. “The colonies can become very large, sometimes reaching the size of an office desk,” says Wood. This gets problematic if they grow on boat hulls or clog water-intake screens and filters. “Not long ago, a large mass of Pectinatella threatened the water supply to New York City,” says Wood. “Although, understandably, this never made the news.” (Well, the cat’s out of the bag now. Sorry, NYC!)
Don’t worry. A native bryozoa species, in general, does good, not evil. “They are basically harmless—non-toxic, and non-pathogenic,” says Wood. They’re filter-feeders and, therefore, they improve water clarity. Their feeding behaviour also produces food for other creatures. “Pectinatella swallows many kinds of particles, but mostly phytoplankton and protozoans,” says Wood. “Both are squeezed tightly in the gut, which ruptures the protozoans like water balloons.” The creature digests the liquid (yum!), but it doesn’t want the phytoplankton (gross!).
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“To prevent those particles from being ingested again, the phytoplankton is pressed into a pellet, infused with some mucus to hold it together, and released,” explains Wood. The pellet sinks to the bottom of the lake. “Down there, it provides nourishment that would not otherwise be available to immature insects and other small invertebrates,” he says. Score! Free pellet! (It’s not like they know how it was made.)
Got a question for Cottage Q&A? Send it to answers@cottagelife.com.
This article was originally published in the May 2024 issue of Cottage Life.
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