|Collecting plankton samples on English Lake|
A brief lesson in the changing biology of our lakes
Hand over hand I pulled the sock net into the boat. The porous fabric let lake water out while capturing tiny creatures inside. As I pulled up on it, the net ushered the little creatures into a plastic tube at the bottom, and once the seven-foot net was completely out of the water, I unlatched the tube at the end to see what was inside.
Thousands of tiny freshwater plankton - a brown cocktail of basic living organisms that look like insects you've never seen before - bubbled at the bottom of this 500 ml, white, scientific-looking tube. They came from the deepest part of English Lake, 25 feet below the surface of the water. Some of them were creepy crawlers with exoskeletons, others were just gelatinous blobs of life (think amoebas). But among the living test-tube cocktail squirmers we did not notice any spiny water fleas.
Originating from northern Europe and Asia, the planktonic spiny water flea is an invasive crustacean among our American waters. It was inadvertently introduced into the Great Lakes during the 1980s and has since been detected in inland waters in Michigan, Minnesota, Ohio, New York and Ontario. In 2003 it was discovered in the Gile Flowage in Iron County...
These creatures are predators of our smaller, native zooplankton and can reproduce asexually and rapidly, effectively wiping out native plankton populations that support young fish habitat. They do not seem to affect larger fish, and in fact there is evidence to suggest they are targeted by perch and bass, but other immature game fish have difficulty eating them because of their long, spiny tails.
By now we know that any species that greatly affects the biodiversity of other aquatic life, especially a foreign invader, is a bad sign for northern Wisconsin's recreation industry, which relies heavily on healthy habitats for plant and wildlife. Therefore, the early detection of aquatic invasive species, especially in inland waters of the Lake Superior watershed, is fundamental to sustaining the natural habitat, which we all so greatly depend on.
My brief excursion on English Lake with Diane Daulton, water resources management specialist, of the Wisconsin Department of Natural Resources (WDNR) and Scott Caven, aquatic invasive species coordinator for Ashland County's land and water conservation department was an excellent, hands on introduction to how fieldwork is conducted by our area professionals in terms of coordinating research, collecting data and understanding problem areas on actual bodies of water, rather than numbers in a lab or water cooler theories from an office.
Besides plankton trolling on our half-day survey of the Ashland County lake, we also performed snorkel inspections at the public boat landing and five other sites that had the potential to introduce invasive plant and animal species. Areas where there looked to be high traffic from backyard boat landings, inlets from other bodies of water, and bottleneck locations that promote high boat traffic were snorkeled for 15 minutes each. In addition we performed what's called a "meander survey" of the entire shoreline. A sort of thorough glance at the plants growing at the water surface.
While we can't all be certified scientists or WDNR specialists, we can be vigilant citizen observers. In Wisconsin, the DNR relies heavily on citizen surveys to get a better idea of what's happening in the far reaches of the north, where population is sparse and lakes, rivers and streams cut through vast areas of state and national forest. If you're interested in learning more about protecting our inland waters from the dozens of invasive aquatic species that have already found their way into the Great Lakes, a good place to start is dnr.wi.gov/topic/invasives. The key to fighting back a tide of misinformation and misunderstanding is, as usual, education.
See you out there,
A woodsman in training.