For millenia after millenia, the quality of Iowa’s water came as a byproduct of a very particular species; the freshwater mussel. Lying peacefully across the river beds of practically every Iowa waterway, millions of mussels main purpose is to filter out impurities, thereby releasing clean, freshwater back into the channel. While still abundant today in our creeks, streams and rivers, the population size is drastically smaller. Whereas once it was said mussels blanketed river floors from bank to bank, today it takes a more skilled eye.

Jennifer Kurth is a malacologist who specializes in freshwater mussels. In fact she is so well acquainted with the animal that her mother sometimes jokes, that she must be part mermaid.

Jennifer Kurth, Aquatic Biologist, Iowa DNR: I don’t know if you can actually see the trail here. He came up over there and is trying to get out to deeper water. Oh sorry, she is. So that’s a female plain pocketbook. Plain pocketbook is one of the species that has  has male and female shell shapes. This is a younger pimpleback. And these guys don’t have male and female shell shapes. The only way to know which way you have is to open it up and see if it’s pregnant.

As unimpressive as these shellfish may look, they are the foundation of ecosystems across North America. Improving the habitat for everything from insects and single-cell organisms to large fish and even humans.

Kurth: The United States is the hotspot for mussel biodiversity in the whole world. It gets better as you go to the south and east, so Virginia, Tennessee… I call them ‘Mother Nature's water filtration system.’ They help to keep our water clean. They’re filter feeders, so they actually have an incurrent syphon, where they bring in the water and all the stuff that’s in it. They separate it, and what they can eat they will. And what they don’t eat they will actually bind up in mucus and deposit it on the river bottom for other animals, scavengers like crayfish to eat. And a single mussel, depending on the size and the age, can average about 10 gallons of water per day, filtered. So if you think about the historic numbers of mussel beds that we used to have here in Iowa, our water was really pretty clean.

Of the 42 remaining species of mussels found in Iowa, the Boone River here in Wright County is home to 11 different varieties of mussels, with three of them listed as threatened.

Kurth: And the cool thing is this site has been sampled six times since 1982 and the number of species… I believe they found 4 species here in 1982, and then it went down to zero for a while. And then in 2009 I believe it had eight or nine species, and in 2015 is when we found 11 species, so they’re definitely making a comeback here on the Boone river which is exciting.

Of course for a comeback to happen, first a disaster must occur.

Kurth: Mussels really declined in the first part of the 20th century, latter part of the 19th century because they were massively harvested for the button industry. You know Muscatine was known as the button capital of the world for a while. They would just go out there with these massive rakes and just take every single mussel they could just because they didn’t want to leave anything for their competitors, whether it was useable for not. So they basically were harvesting in an unsustainable way.

Today commercial mussel harvesting is banned in the state of Iowa; but combined with modern farming practices and increased development raising the silt levels of Iowa rivers, mussels were pushed to the brink of extinction. Thankfully just as regulations were enacted, conservation and education jumped to the mussel’s aid as well.

Megan Bradley, Lead Mussel Biologist, USFWS Genoa, Wisconsin: So we’re here at the Dubuque ice harbor with the Mississippi River Museum and we’re harvesting our cages of infested fish to bring in the mussels that dropped of them over the season. So these mussels will be used for recovery as far north as the Chippewa River in Wisconsin and as far south as around Guttenberg in Iowa.

The harvesting crew of biologists, DNR employees, and volunteers are collecting thousands of juvenile Higgins Eye Pearly mussels, an endangered mussel found throughout the midwest. This recovery effort is an excellent example of the interconnected nature of mussels and the aquatic ecosystem they help maintain.

Bradley: Higgins Eye are a part of a group of mussels that lure in their host fish and the females have a part of their mantel, which is the part of the animal that builds their shell, that um is modified to look like a fish. And in the turbid water, apparently fish… you know their vision declines just like ours does… and so they have just kind of basic lure. It’s got like a frilly tale and a bit of an eyespot and the mussel is able to push her gills up, where her larvae are stored and the fish will come down, sees that, thinks it’s lunch, comes down and takes a bite. In doing that it breaks open the female mussels gills and gets infested with the larvae of the mussel.

Over the coming weeks, the larvae will transform into juvenile mussels and fall off their host fish to the river bottom. If they settle into a suitable habitat, a new mussel bed will propogate.

Jared McGovern, National Mississippi River Museum and Aquarium: These animals don’t have eyes. They have photo receptive cells that can tell if it’s light or dark. Itty bitty bundle of nerves that is kind of a brain but somehow they know what fish eat.

Jared McGovern is an educator at the National Mississippi River Museum and Aquarium and events like the Higgins Eye harvest are the perfect experience for students to learn all the wonders of these seemingly insignificant mollusks.

On top of seeing the harvest up close and personal, Dubuque area students learn all about the mussels' Iowa history, their lifecycle, species identification practices, and of course a firsthand look at their water filtration powers.

McGovern: I put these animals in here… 8 o’clock. It’s now close to 9 o’clock and in that time these animals have filtered about two and half gallons of water.

Hands on field trips like Jared’s have the potential to change a student’s life. Holding a mussel and learning how humans, wildlife and the ecosystem depends on is the kind of experience that builds conservationists. But if not, they at least learn that the quality of their environment can hinge on something as small as a freshwater mussel.

McGovern: These are a keystone species. They literally create a habitat with their body. These animals as they grow they are in such mass that and such volume in certain areas that they will they will cover the entire bottom of the Mississippi River. And they’re going to create a physical structure for algae to grow on, algae that then attracts insects, insects that attract fish, some fish even breed on these mussel beds… So as a keystone species if it was not for this particular animal, that habitat would not exist. These animals are one of the coolest and one of the most important animals living in the Mississippi River and in North America we have the most diverse population of anywhere else in the world.

REAP
Gilchrist Foundation