Are Invasive Species Always Problematic?

      Last week when we discussed the destructiveness of invasive species. One milfoil plant has the potential to ruin an entire lake, and an Emerald Ash Borer can wreck havoc on an entire forest. When discussing our personal experiences with invasive species, zebra mussels were mentioned. Zebra mussels are native to Europe. They have razor sharp shells that cover up sandy lake bottoms. Since their discovery in Lake Champlain twenty-two years ago, they have been known to kill native mussels, ruin anchor lines, and cover up water intake pipes.
       The article on the Adirondack Almanack spends little time on the negative impacts of zebra mussels. Interestingly enough the guest writer, Declan McCabe, spends most of the article discussing the positive aspects the mussels have on Lake Champlain. Zebra mussels are incredible filters and have the ability to filter one liter of water a day. While the mussels do take over the sandy foraging ground of fish, the layers of mussels also provide good hiding spots for insects that are usually eaten by those fish. The mussels also give lake floor invertebrates a source of food via their excrement. Zebra mussels can also improve diversity where they colonize. The writer, who is a biologist, conducted an experiment with Ellen Marsden and Mark Beekey to compare parts of Lake Champlain's bottom that contain and don't contain zebra mussels. The results showed that areas with zebra mussels had twice as many species in them than areas without mussels after one month. Even in an aquarium setting, invertebrates in tanks with zebra mussels have a higher survival rate than those without. Zebra mussels may be an invasive species but they aren't completely destructive.

      McCabe acknowledges it would be better for the lake if the zebra mussels weren't there. However, like most invasive species, they are here to stay and it is critical to see how they interact with the Lake Champlain ecosystem. As it turns out they're not completely bad, and follow up studies have shown that the zebra mussels are past their peak numbers. They are still in the lake but their numbers are leveling off, suggesting the ecosystem could be reaching what he calls an equilibrium. Perhaps we will start to see other invasive species in the park (especially ones that are difficult to remove) reach an equilibrium and not be too harmful to their environment.

Sources Cited:

McCabe, Declan. "Understanding Zebra Mussel Impacts on Lake Champlain" Adirondack Almanack. October 6th, 2015. Accessed October 8th, 2015. http://www.adirondackalmanack.com/2015/10/understanding-zebra-mussel-impacts-lake-champlain.html

Photo: The 100th Meridian
http://www.100thmeridian.org/photobank/US_Fish_and_Wildlife_Service/Zebras/DSCN3674.JPG