SAVANNAH, Ga. -- The U.S. Army Corps of Engineers’ Savannah River basin lakes, J. Strom Thurmond, Richard B. Russell and Hartwell, have some strange inhabitants that are alien, globby-looking things, and sometimes mistaken for the eggs of some aquatic creature, but in-fact, they are filter-feeding, microscopic invertebrates known as Freshwater Bryozoan or zooids, and their presence indicates a healthy body of water.
There are approximately 4,000 different species, but only 50 types live solely in freshwater. The most common Bryozoans, which translates to “moss animal” in Latin, are the Pectinatella magnifica. It thrives in the Savannah River lakes and makes its own substrate, forming large gelatinous colonies that attach to anything stationary and grow just below the surface of the water.
“The bryozoan can be found commonly on docks, sticks and other underwater structures,” said Rebecca Downey, J. Strom Thurmond Project Office natural resource specialist. “These harmless, aquatic invertebrates live in colonies and are natures natural water filter. They are signs of clean water quality and are sometimes food to many snails, insects, and fish.”
Their diet consists of bacteria, algae and protozoa. They have tentacles that are lined with microscopic hairs at the end of its body, which they use to catch food particles, drawing the particles toward their mouths.
Their growth is temperature dependent, coming to life around June in South Carolina and Georgia and disintegrate by winter. And while they have a positive impact on the ecology of a body of freshwater, they can be a nuisance to humans if they grow in the wrong place, like inflow or outflow pipes, etc. However, they are easily moved if they become bothersome.
“They can be easily removed from surfaces by scrapping them off,” Downey said. “Also, the colonies usually start to die off in the fall when the weather begins to cool and will likely be completely gone by the wintertime. But we are happy to know they are currently thriving in our lakes.”
When a colony disintegrates, the statoblasts [masses of cells that function as "survival pods”] are released and move to a new location by water currents or on another organism. They can also remain in the sediment until the following spring when the cycle starts over.
Click here to view a video of Freshwater Bryozoan in at J. Strom Thurmond Lake.