An Ancient Ally: Warnings from Freshwater Sponges

Underneath the rocks that cover the floors of our watershed lives possibly the oldest animals ever recorded, sponges. They’re not much to look at, in fact, you might not notice they’re an animal at all at first glance. These tan booger-like invertebrates are the simplest multicellular organisms but they relay to us very important information. The presence of healthy freshwater sponges indicates a high quality of water (U.S. National Parks Service, nd).

Our AmeriCorps members, led by freshwater sponge researcher Marc Yergin, waded through Kooser Run this May in the hopes of finding an abundance of freshwater sponges. Marc is what you might call a pioneer of freshwater sponge research in western Pennsylvania. For the past several years, Marc has been collecting data on the freshwater sponge population in our area. What he has found is that there has been a decrease in both their size and quantity.

Freshwater sponge found in Kooser Run in 2018 covering the entire base of the rock.

Decline in freshwater sponge population can be caused by acid mine drainage, agriculture runoff, chemical spills, and other disturbances. Despite having existed on earth for between 500-800 million years, sponges are incredibly sensitive. Freshwater sponges require a healthy pH between 7-8 and low levels of sediment and pollutants. There are more than 10,000 sponge species worldwide with only around 3% being freshwater sponges, the rest are found in oceans. There are 31 freshwater sponge species found in North America, but only 14 have previously been documented in Pennsylvania and only in the eastern side of the state. In his search, Marc found three species of sponges in our western Pennsylvania waters. This is the first literature report of freshwater sponges in western Pennsylvania (Yergin & Pearce, 2018).

Freshwater sponge found in Kooser Run this May.

Their presence is both an indicator of water health, as well as a contributor to it! Freshwater sponges act like filters removing bacteria and other small organic debris and substances (Yergin & Pearce, 2018). Water passes through small holes called pores and out larger holes called oscula. Sponges can funnel 10x their volume in water every minute! Talk about tiny yet mighty. Freshwater sponges also serve as food to animals that inhabit our waters such as crayfish, ducks, and a variety of macroinvertebrates (U.S. National Park Service).

AmeriCorps member Courtney Berish collecting a freshwater sponge sample.

Marc plans on monitoring our freshwater sponges in our area closely and hopes that his research proves the population plays an important role in the health of our watershed. MWA is eager to help and our AmeriCorps members already plan on getting back in the field with Marc next month!


“Freshwater Sponges (U.S. National Park Service).” National Parks Service, U.S. Department of the Interior,

Yergin, Marc, and Timothy Pearce. “Stalking the Freshwater Sponges of Western Pennsylvania.” Carnegie Museum of Natural History, 24 Sept. 2018,