Frog eggs, aliens, zebra mussel sacs, I bet you’ve heard it all. So, what’s the truth about all those strange looking gelatinous blobs hanging on the lake timber?
Well, it is neither of the above that’s for sure. Those odd thick green and brown jelly sacs hanging all over our lake timber are known as Bryozoans aka “Moss Animals”. These so-called moss animals are microscopic aquatic invertebrates that live in colonies. Each colony is made of many individual creatures called “Zooids.” Zooids are microscopic cylindrical creatures with a mouth, digestive tract, muscles, and nerve centers and are covered by a protective matrix which may be delicate, hard, or gelatinous depending on the species, this is what gives it that “Blob/Brain” appearance. While most bryozoans live in the sea there is about 20 different freshwater species. Bryozoans live in standing and flowing water and need a firm substrate, such as rocks, sticks, submerged trees, sunken boats and so forth to attach to and Cannot live on silt bottoms.
Bryozoan colonies grow by budding from the adult zooids. At the end of summer, and when the lake temperatures begin to drop Bryozoans die. Their jelly sac dissolves and as it does it releases small brown discs that lie dormant through the winter freeze. Then as the water begins to warm new colonies begin to form. Bryozoans have existed for millions of years and many species are found as fossils, especially the seawater species. While it is thought that the freshwater species are more recent there have been fossils found here in Missouri and in other fresh water sources across the country.
What do they eat? Bryozoans are filter feeders, meaning they sieve food particles out of the water. By using their retractable “crown” of tentacles lined with cilia or (little hair whips) they can create a current towards the mouth. From this current they select small plankton, such as: Green algae, Bacteria Flagellates Other small one-celled animals. They are prey to snails, fish and insects.
Freshwater bryozoans are harmless and while they can be a little pesty their presence usually indicate good water quality with good oxygenation.
Most generally unless we were divers or viewing the bottom of the lake we wouldn’t see them however since our water is dropping they are being exposed and can be seen lining Bull Shoals and Table Rock lakes.
So, that’s the truth behind “The blob”. It’s really quite an interesting species and while it may not be the prettiest life form, it is just another unique way mother nature takes care of our lakes. I hope you have enjoyed this article. If you would like to learn more about fresh water Bryozoans I have left a few links for you.
Have a great day and Tight lines!!
Credits: Missouri Dept of Conservation, Dept of Ecology Washington, Bob Lusk Outdoors