UI research team addresses problem with invasive clams
They’re small — growing no more than a couple inches in length — but they’re many.
Each one is capable of singlehandedly creating 350 more every reproductive cycle and they’re taking over bodies of water across Idaho.
The Asian clam, like many invasive species, is a serious problem in bodies of water like Lake Tahoe in California and Illia Dunes in Washington. A University of Idaho research team is testing a possible solution in Lake Pend Oreille, which currently has a smaller infestation of the clams.
“It’s kind of an alarming thing and there’s very little that’s actually been done to try to get rid of the Asian clams,” said Elizabeth Braker, a graduate member of the research team, “In November, they were able to find that the clams are still very localized to the marina areas in Ellis Port Bay. They’ve extended south along the shore, but they haven’t spread to any other areas of the lake that we know of.”
Braker said knowing the infestation route is important in trying to establish a method for getting rid of the clams.
Christine Moffitt, the main researcher of the project, said outreach with those who live around Lake Pend Oreille was a crucial aspect in getting started.
“You have to engage with the public, because you could have the greatest idea, but if the public doesn’t understand it, or if they don’t buy into it, it’s not going to fly,” Moffitt said.
Braker said the research team is using a new process to decrease the clam population, a combination of two different treatment ideas. The first, sodium hydroxide, came from another graduate student working with Moffitt on a project to treat ballast water in ships, which Braker said could be a starting point for an invasive species.
“It’s easily accessible and it causes mortality to Asian clams and possibly other invasive species that might be sucked into ships’ ballast tanks when they are crossing the ocean and could inadvertently be released in American waters, and therefore cause an infestation,” Braker said.
Based on the research in the project, Braker said sodium hydroxide is an effective way to kill Asian clams, because it kills the larvae within hours and full-grown clams within 10 days.
The other half of the process is rubber pond liner, which is already used to control an invasive plant species in Lake Pend Oreille. Braker said similar barriers used in Lake Tahoe resulted in a 90-100 percent mortality rate for the clams. She said the situations are different, which is where the sodium hydroxide is involved.
The researchers started the research project about a week ago, placing small burlap sacks filled with sodium hydroxide on the bottom of the lake, before trapping the chemical with the rubber pond liner.
The combination creates a contained area between the sediment on the bottom of the lake and the rubber pond lining. Braker said it would allow a quick increase in the pH of the isolated area of the lake, killing the clams quickly. She said there would be no long-term negative effects on the lake because sodium hydroxide reacts with carbon dioxide in water to form an inert salt.
Moffitt said the research team planned to cover the whole affected area at the same time, but ran into unexpected problems with high water and would finish treating the infestation after spring break. She said the halt illustrated a common occurrence with fieldwork.
“In the lab, it’s wonderful, because you can control the environment, you can set what you want and even that can have great failures,” Moffitt said. “But you go out in the field, and what happened to us last weekend was that the water levels were a whole lot higher than they’re supposed to be this time of year in the lake.”
Braker said the clams have a big impact on the water quality if left unchecked.
“If they reach densities like they did in Lake Tahoe of up to 3,000 Asian clams per square meter, then suddenly you have an extremely good water filtration — so good that you’ll have crystal clear water to begin with, and then when there’s no more food, then you see massive die-offs,” Braker said. “They basically filter themselves out of their nutrients.”
Braker said Asian clams are hardy creatures that are so good at surviving, they displace native organisms by taking all the food. She said a single clam can filter through five gallons of water every day. Asian clams are hermaphroditic, meaning a clam can reproduce independently.
While large boats can be responsible for spreading invasive species, Braker said, it’s possible for them to spread from small boats, or even waders.
“I think it’s important to note where this infestation is,” Braker said. “It’s off of two very popular marinas. So it stands to reason that the clams got there via a boat that didn’t properly clean, drain and dry their hull, their tanks. And they come and they put in there at the ramp, launched at the ramp and all it would have taken is one little veliger, one clam larvae, to grow this population.”
Daphne Jackson can be reached at [email protected]