Thursday, February 15, 2018

How Many Mussels is Too Many? - Aquatic Invasive Species

     As the Willard students learned, mussels can clog up pipes, reducing water access, and use the resources that native species rely on, edging them out of the ecosystem. How do we know if the mussel population is large enough to be a concern?

     Heidi asked the students to image a nuclear power plant. Nuclear power plants rely heavily on the functioning of cooling systems. If mussels were introduced to the cooling system, the water flow would slow and heat up, rendering critical cooling processes ineffective. A small number of mussels would be disastrous.

     More likely, mussels would affect hydroelectric power.

     "Montana has some of the cheapest power in the US" because the Columbia Watershed has so many dams, Heidi pointed out. Mussels would slow the rate at which dams produce electricity, increasing power prices for all the residents receiving power from the Northwest.

     The problem lies in the rapid reproduction rates of mussels. Mussel populations do not stay small for long, as the students recalled on my first visit. Mussels' ability to thrive in most any water body contributes to their designation as "invasive," and means that any number of mussels where they are not supposed to be is too many.

Bar graph of ml of water filtered by
mussels in 1, 3, 8 hours
Chart of ml of water filtered by
mussels in 1, 3, 8 hours

   Heidi assisted the students in performing a small demonstration on the impact mussels have on water, aside from their physical presence. One student put a scoop of rich dirt into a plastic soda bottle to simulate the detritus that many water species extract nutrients from.

Photo courtesy of Bailey Roseveare

     "Mussels filter how much water per day?" she asked.
     "One liter [each]," a student answered. The student poured one liter of water into the bottle to represent the water column. Then Heidi held up a contraption with a small canister attached to a screw cap.

     "Specialized gills are what these cotton balls are going to represent," Heidi explained as she stuffed two cotton balls into the canister. After attaching it to the bottle, Heidi set out a clear glass jar and began to squeeze the bottle. The water was forced into the contraption and filtered by the cotton ball gills.

     "What do you notice about the water in the jar?" she asked.
     "It's clear."
     "It's pretty clean."
     "Is that a good thing or a bad thing?" Heidi followed up.
     "Bad," the students agree. One clarified that it was bad because the water had no nutrients left in it.
     "What's happening to the gills?" Heidi took the cotton balls out, now brown from collected soil.
     "They're getting dirty," a student replied.
     "They're filtering nutrients," Heidi reminded them.

     This realization that clear water was unhealthy contrasted the students' initial expectations from the week prior. They wrote that clear water was cleaner, which is good for our drinking water. They figured cleaner, clearer water was less likely to make humans and animals sick. Now, however, they understood that the detritus that makes water unappealing to us is actually an important food source. It also maintains ecosystem balance, as they would learn next.

     "The mussels create an environment unsuitable for living," a student concluded.
"Or we could call it sterile," Heidi elaborated.

     In addition to removing helpful material floating in the water, mussels can increase water toxicity. Mussels produce pseudofeces, or "fake poop".
If there's anything they don't want, the dump it out," Heidi explained. This means "they spit out the toxic stuff."

     The clear water column expands the literal zone of bodies of water. The litoral zone is the area where sunlight can reach the bottom of the water column. This is the section where plants can grow, as they utilize the sunlight for photosynthesis. A larger litoral zone allows more plants to flourish.

     "What happens [with plants] at the end of the growing cycle?" Heidi asked.
     "They die."
     "They die and release phosphorus, perfect conditions for algae blooms," Heidi confirmed. If there is a larger litoral zone, more plants grow, and more plants die, releasing more phosphorus. Algae blooms make water anaerobic, depleting the oxygen available and thus making it difficult for creatures that need oxygen, such as fish and certain bacteria, to survive. This anaerobic state is conducive to the growth of botulism, a toxic bacteria.

     The class read over an article in The Oakland Press about bird deaths that Heidi had passed out. What do mussels have to do with birds? I wondered. Botulism contaminates the food that loons and other waterfowl eat, entering their nervous systems and shutting down their bodies. The article went on to list the numbers of loons, ducks, gulls, and other birds found dead on the shores of water infested with mussels. It provided a stark image of the chain of effects mussels have on an ecosystem.

     Heidi connected the article back to Montana, noting the Montana has the largest loon population west of the Mississippi. If mussels made it to the Columbia Watershed, it would devastate this valued population.

     We revisited the pros and cons of having clear water in aquatic ecosystems, again emphasizing how our assumptions of human needs do not always match with the needs of other organisms.

     "Wow, and they're only this big, they're tiny!" a student expressed amazement at the damage that can be caused by a creature the size of a fingernail.

     Watching the students grasp the interconnectedness of ecosystem elements and the impacts small changes can have gave me hope that early education like AIS will lead to better environmentally-informed citizens in the future.

-Cassie Sevigny
AmeriCorps Team Member
Media Coordinator 

Thursday, February 8, 2018

Those are Some Gravelly Mussels - Aquatic Invasive Species-

     They're in our lakes, they're in our pipes, they're on our boats. They're in every major watershed in the US except the Columbia, which is ours.


     Mussels are bivalve mollusks. They have two shell halves that protect the mussel's soft body. Mussels can attach to many surfaces, including the outsides of boats, which enables them to travel between bodies of water. Such mobility is the reason for careful boat-cleaning requirements. Female zebra mussels can produce 500,000 eggs per year, with mature mussels sometimes reaching a million eggs per year, resulting in rapid reproduction and establishment in an ecosystem where there was no prior mussel population. This kind of population growth can threaten the ability of native species to survive. Originally from Eurasia and now thriving across North America, mussels provide the perfect example of an aquatic invasive species for WEN's Aquatic Invasive Species (AIS) curriculum, called Columbia Headwaters Education Kit 4.

     Heidi Sedivy leads AIS lessons once a week at Willard Alternative High School, where small class sizes enable intimate engagement with the imminent threat and application of science to relevant local issues. On January 30th I joined Heidi and Bailey, AIS Assistant, on my first classroom program.

    Bailey began by asking the students to think about how mussel invasion might affect human activities. As mussels settle down in the pipe that will become their home, they reduce the water flow rate exponentially. Given their proclivity for clogging up pipes, mussels could prevent the efficient transport of water for agricultural irrigation or hydrating cattle. This increases the difficulty of raising crops and animals, which would increase prices for consumers and decrease profits for companies.

     With human implications in mind, the class set up a lab to examine the physical effects of mussel populations on water flow. Heidi and Bailey demonstrated how to use the equipment. A translucent funnel (aka the top cut off of a plastic soda bottle) sat on top of a clear tube, about an inch in diameter. At the bottom was a filter before the rubber output. This tube simulates a pipe. White gravel would serve as our mussels (though they reminded me of the barnacles that grow on submerged posts and rocks in the Puget Sound).

   Split into two groups, the students poured 2 liters of water through the funnel and timed how long it took to travel through the tube and empty out into a bucket below. After a test-run of an empty tube, they added 5cm of gravel and timed the water again.

     "Mm, look at that dirty water," one girl remarked on the dirt washing off the tiny rocks.
     "You're cleaning our rocks for us!" Bailey replied.

     Even at this lowest increment of "mussels" the water took significantly longer to fully filter through.

     The students noticed that the tubes had slightly different rates, even without the rocks slowing the water.

     "Maybe one team is pouring faster," someone suggested.

     After several rounds of adding "mussels" and pouring water through, the data was ready for analysis. The students noticed that the water did filter through more slowly the more gravel they added to the tube. However, the times from each team did not quite match up...

     "I think those rates are really weird," one student commented.

     Indeed, the average time for 20 cm of gravel was .4 seconds faster than for 15 cm! How could this be?

     "The tube might be haunted," someone else said. While this counts as a hypothesis, we could not test it, so the conversation moved on. What else could cause variation in the experiment, or how could real mussel pipe-clogging differ from the model?

     "I think the rate would fluctuate because the mussels stick to the sides [of pipes] and not just the bottom." This could allow many more mussels to congregate before problematic water flow indicates their presence.

     The class wrapped up with some brief art: creating diagrams, or visual models, of the experiment. This way, when they created graphs the next week they would have a handy reference of what they did.

Mussel experiment diagram

-Cassie Sevigny
AmeriCorps Team Member
Media Coordinator