Creatures from the River: Bryozoa

Yesterday, while out conducting routine water monitoring, our Water Quality Specialist Masaya Maeda found this blob in the water near Bladensburg Waterfront Park. Not as pretty as some of his other photos but it's still part of our river's ecosystem, and a nifty specimen at that.

It's a colony of Bryozoa, which is a group of organisms that has been around for approximately 5 million years! Most of these critters live in marine waters, but there is one class from the Bryozoan phylum that lives in freshwater: Phylactolaemata. The colonies form on submerged logs, branches, etc. and can be 2 to 7 feet in diameter.

The colony Masaya found is probably Pectinatella magnifica, common name magnificent bryozoan. They are native east of the Mississippi River and thrive in warm water (temperatures above 60F) which is why they are more visible during the summer months. As filter feeders, they feed on detritus (dead plant and animal matter) so their presence here probably suggests the water needs cleaning, though Masaya reports that it has been a few years since he last saw them. Their tolerance for pollution is uncertain as studies have shown conflicting results, but if they are living in the Anacostia it would seem that they have some level of tolerance for pollution.

Magnificent bryozoans are becoming a big problem in the western US, where they are not native. From US Fish and Wildlife, "They are worried because increases in filter feeding activity makes water clearer, permitting solar light to reach greater depths. This can allow more aquatic plants to grow and shift the natural balance of that habitat. Scientists think that if water temperatures rise due to climate change, Magnificent bryozoa may find more suitable habitat here. And once they are here in large numbers they can disperse rapidly." P. magnifica has also been found in Canada, Europe, and Asia; this species seems to have adapted to many different habitats.

Next time you are near the Anacostia River (or any slow-moving freshwater source), see if you can spot one of these unique colonies! We would love to know their range in the watershed and see more photos!