Mysterious “Green Blobs” In Our Lake

The plain English explanation for the green blobs sometimes found in our lake is that they are colonies of microscopic animals that are, in the words of some children, "Slimy and yucky".  One of the names for them is Bryozoa and they are commonly smaller than a tennis ball but can be larger.

Bryozoans are not dangerous or harmful. Neither are they rare but they can appear in smaller or larger numbers in different years depending on a variety of environmental factors. They may even be beneficial to the lake because they eat algae and protozoa.

A more scientific explanation is that the majority of Bryozoans are marine (several thousand species), but one class, the Phyloctolaemata, is found exclusively in fresh water. Pectinatella magnifica, one species belonging to this class, is commonly found in freshwater lakes and rivers in North America. Most people call them jelly blobs or just plain “blobs” given their appearance. Each colony is a collection of genetically identical organisms (zooids) that exude a protective matrix, a gelatin-like substance made mostly of water, firm but slimy to touch. Zooids are microscopic cylindrical animals with a mouth, digestive tract, muscles and nerve centers. The zooids are covered by a protective matrix that may be delicate, hard, or gelatinous depending on the species. They feed by filtering tiny algae and protozoa through a crown of tentacles (lophophore).

To learn more about Bryozoa go to the following Web Site by the University of Massachusetts Amherst

U of Mass. Bryozoa Website