Image of a Pectinatella magnifica. Credit: Triclops200Recently we noticed that one of the most popular articles of all time on www.aquascape.net is “The Blob.” Since we doubt folks are surfing our site for a review of the 1958 sci-fi film, it seems that there’s a lot of interest in the gelatinous masses spotted on the shores and in the shallows of local lakes and streams each summer. The proper name for these blobs is “Colonial Bryozoans,” and the particular freshwater variety we see in Georgia is Pectinatella magnifica.
Most bryozoan species live in marine environments, but (as evidenced by their presence in these parts) there are several freshwater species as well. Colonial bryozoans function similarly to coral, with each colony containing thousands of tiny zooids, all filtering the water for food particles. They are more likely to occur, and thrive, in warm, fertile water bodies where there’s plenty of available organic matter to feed them.
The “jelly” that gives each colony a blob-like appearance is actually zooecium, a protective coating that holds the colony together. Neither the jelly nor its contents pose any health threat to humans, fish, or other animals. In fact, colonial bryozoans can be safely handled – no gloves required, except for the squeamish – and the colonies are often harmlessly consumed by wildlife.
The colonies die when the weather turns cold, but they do leave behind their tiny, egg-like statoblasts, which can survive the winter and start new colonies the following summer. Depending on a variety of factors, colonies may come and go over the years.
Of interest, the “blobs” do seem to be spreading. In the past, Pectinatella magnifica were seen only east of the Mississippi River, but they have now been discovered as far away as the Pacific Northwest. Although harmless here, there’s some concern about their impact as a non-native species in other areas.
Finally, if you did land here looking for a scary movie, we have one for you:
