A major goal of this trip is to show people the amazing biodiversity found in our rivers. Since I began the trip on Aug. 25, I have taken a group snorkeling and kick seining for fish. I have searched for macroinvertebrates (small aquatic insects that live beneath the river’s rocks and logs) with Georgia Adopt-a-Stream and New Echota River Alliance, and I’ve taken numerous photos of land animals along the river’s banks. However, our basin is a hotspot for another group of animals that too often get overshadowed by more charismatic creatures—freshwater mussels.
Today, a group of about 20 of us paddled 11 miles down the Oostanaula and learned a lot more about these unique creatures. At the end of the day, everyone took home a hand full of mussel shells. Helping with identification was Jason Wisniewski with the Georgia Department of Natural Resources, the state’s mussel expert who has earned the nickname “Clambo.” The upper Coosa River basin has the largest mussel diversity in Georgia, and Georgia ranks third among the 50 states for mussel diversity.
Mussels, which live partially buried in the river bottom, are much more than mere “rocks with guts.” They are very important to our aquatic ecosystems because they filter nutrients out of the water and help clean our rivers. They are also very important indicator species. Because they tend to stay in one location their entire lives (mussels have a foot like a snail, but don’t ever travel very far) and because of their sensitivity as a filter feeder, they are very susceptible to pollution, sedimentation, and habitat alterations.
The Coosa basin’s mussel populations have been decimated by all of these threats. In fact, of the upper Coosa River basin’s 43 native mussels only 28 remain. Seven of the remaining 28 are federally protected species. Globally, mussels are considered one of the most threatened groups of animals on the planet.
Survival of freshwater mussels is made even more precarious because of their unique life cycle—which is dependent upon the river’s fish (which have also experienced declines). Female mussels use modified appendages as lures that often resemble small fish. These lures attract other fish looking for a meal. When the fish hits these lures, the mother mussel releases its larval called “glochidia.” Instead of getting a tasty meal, the unsuspecting fish sucks the glochidia into its gills where they attach and mature to their juvenile stage. The young mussels then drop from the fish and embed themselves in the river bottom to grow into adult mussels. In some cases, mussels rely on a particular species of fish as their host, thus a decrease in a certain fish population can cause a decrease mussel populations.
While pollution and sediment have killed many mussels, the biggest cause of the extinction of some mussel species and the decline of others has been the construction of dams. Many mussels cannot survive in lake habitats and dams have restricted many migrating fish (which host the young mussels) from certain portions of the Coosa River system.
Though mussels have a hard time competing for attention with other cute, cuddly animals like panda bears, they are perhaps of even greater value because of the services they provide for us and our rivers. Certainly, the paddlers on today’s excursion can attest that mussels are much more than rocks with guts. With names like pistolgrip, three horned warty back, and washboard, perhaps they can be just as charismatic as the panda.
The highlight of the paddle was a battle between an eastern king snake and a northern water snake, but in my opinion watching a southern pocketbook extend its foot into the river bottom and begin filtering the water was just as cool.