Freshwater mussels could help filter out bacteria and nitrogen levels in surrounding waterways, UI researchers investigate.
Maria Kuiper
The Iowa River, which winds through the University of Iowa campus, is home to an animal that could, over time, help decrease water pollution. Mussels have a population of about 500 million in the upper Mississippi River alone.
These powerful, yet tiny creatures were the subject of a lecture at Hancher on Thursday night called “Science on Tap: Freshwater Mussels to the Rescue?”
Mussels live on river bottoms and eat by suspension feeding. This means they suck in water, filter out particles, and push the rest back out. Although a simple process, this could eventually lead to the reduction of nitrogen levels in waterways.
Craig Just, an assistant professor in the Department of Civil and Environmental Engineering, said Iowa City and its surrounding areas are a main source of nitrogen runoff.
“The Iowa City area produces 16 to 27.1 pounds per acre of nitrogen run-off,” Just said. “Twenty percent of land-applied nitrogen fertilizer in the Mississippi and Gulf of Mexico is from the Corn Belt.”
Just said the nitrogen runoff creates a 7,000-square mile area called the “Dead Zone” in the Gulf of Mexico. This results in a $20 million loss to the fishing industry annually.
Besides fertilizer, a main contributor to the nitrogen runoff is drainage tile, an agricultural drainage system that removes excess water from soil below the surface.
“Iowa has enough drainage tile to go to the moon and back four times,” Just said. “That is about 2 million miles.”
This is where Just and his graduate students had the idea to investigate how mussels help nitrogen pollution by “eating, pooping, peeing, and puking.” One type of mussel, a pocketbook mussel, can turn over 10 gallons of water a day. In the northern 300 miles of the Mississippi, mussels filter 14 billion gallons of water per day.
Mussels take in particles, filter them, and release it out as ammonia and urea. Just and his team found that bacterial levels went down, but surprisingly nitrate levels went up.
“We need to be cautious about how mussels can release nitrate since it is very mobile,” Just said. “A small negative outcome may be outweighed by a potentially much larger benefit, but this will need reassurance by further research.”
Ellen Black, a graduate student in Civil and Environmental Engineering, said even though mussels may release some nitrogen, there are more benefits.
“Mussels will filter out anything,” Black said. “Whether it be nitrogen or not, mussels can help purify water in other ways, like E. coli.”
Louis Licht, the president and CEO of engineering company Ecolotree, also provided insight into the benefits of mussels.
“Water pollution started to get bad around the invention of the plow,” Licht said. “Some of the problems can be fixed by engineers, but some of it can be done by nature itself.”
Just said if environmental engineers and the world population can work together, it would be better in the long run financially and environmentally.
“If we can get the ecosystem back in better balance, in respect to nitrogen outputs,” Just said, “then we would avoid the cost of nitrate removal in water treatment plants.”
Iowa City taxpayers currently pay $7 million for the water-treatment plant, Just said. If nitrate levels go down, taxes would also go down.