Fighting off sea lampreys could cause more harm than good
HOUGHTON — Lampricides are applied in tributaries each year to kill invasive sea lampreys but what happens to those chemicals?
Megan McConville of Northern Michigan University is researching just that. McConville presented some of her recent findings at a seminar at the Great Lakes Research Center earlier this week.
Lamprey are an invasive species of fish that have historically caused substantial damage to Great Lakes ecosystems and fisheries. Controlling the lamprey population has been an area of focus since the 50s with considerable success.
“It’s heralded as one of the most effective invasive species control efforts,” McConville said.
One key element has been the use of lampricides, chemicals that kill young lamprey while they remain in tributaries.
McConville focused her research on the breakdown of two lampricides, TFM and niclosamide.
TFM is more selective for lamprey than niclosamide but McConville found other differences in how they degraded over time.
Light breaks down the chemicals, a process known as photodegradation, either directly as light or indirectly in the form of organic matter.
“Generally the products are less toxic and less persistent which is a good thing,” McConville said.
PH of the water plays a role in the speed of this breakdown, McConville discovered. TFM photodegrades faster in higher pH water while niclosamide does the same in low pH water.
With organic matter, niclosamide breaks down even faster.
“As we add more organic carbon we see that these rates of degradation increase so in terms of persistence in the environment this is good,” said McConville. “Our rates are nearly tripling as we add more and more organic carbon to this system.”
TFM remains stable and unchanged by increases in organic matter.
However, upon leaving the lab these numbers are less rosy. While field testing water where lampricides were applied McConville found other factors made the process slower and less certain.
Deeper water can lessen sunlight breakdown as can tree cover, clouds and other factors that vary between bodies of water.
“A lot of these tributaries are not going to be subjected to photodegradation of the lampricides,” she said. “We’ve really effectively proved that a lot of the mass that makes its way into the lakes.”
Now the question is, what happens to the lampricides when they get there? Do they break down quickly or linger?
“You finish with one project and come to a million new questions,” McConville said.
She would like to research the subject further as well as answer questions involving unintentional chemicals that end up in the waterways and behavior of granular lampricides.