A couple of decades ago it seemed finding a new invasive species in the Great Lakes was as common as finding a fish hook in a bait shop. Was it a sudden influx of new arrivals or were more discovered just because people started looking? Probably because more emphasis on identifying undocumented species was given. Invasives have been showing up in the Great Lakes since the Erie Canal was opened.
As walleyes rebounded in Lake Erie and salmon were established in the other lakes, more and more people became aware of the importance of the lakes and the threats invasive species posed to them. There have so far been 186 invasive species cataloged in the lakes.
While various agencies fought over (and are still fighting over) just who has, should have and should butt out of anti-invasive species regulations, the influx of invasives has nearly ground to a halt. Some say it’s because all the possible invasives which could infiltrate and occupy the Lakes have already arrived. Some say it’s because of the “swish and spit” regulations put into place over a decade ago. S&S requires ocean going boats to swap out freshwater bilge with saltwater and then sealing their ballast tanks while they are in the lakes. (Ballast water has been the major vector in introducing zebra and quagga mussels, round gobies and other invasives.) Very few organisms can survive both in fresh and salt water. No new invasives have been found in the lakes since 2006.
With ballast-water-borne-invasives curbed or halted, the threat of Asian carp has sucked up most of the available funds dedicated to finding and fighting new arrivals. Asian carp control has become an industry all in itself.
Some are still searching for invasive newbies, however, and Cornell University researchers have confirmed two new exotic species have established themselves in the Great Lakes. Cornell has been monitoring zooplankton populations in all five of the Great Lakes since 2012.
Every spring and summer, Cornell researchers hop on the EPA’s research vessel, Lake Guardian, to tow nets across 72 areas in the Great Lakes to monitor zooplankton populations. In recent years, they’ve included close-to-shore scans, sifting through western Lake Erie’s often pea-green waters.
Generally speaking, western Lake Erie has the most diverse assemblages of zooplankton anywhere in the Great Lakes because of how nutrient rich it is, and how different it is than the other Great Lakes. It’s shallow and it’s relatively warm – both factors promotes healthy populations of zooplankton. Plankton serves as the base of the food chain because they are the staple of several small fish species’ diets.
Cornell’s team of six trained taxonomists examine thousands of samples the trawls scoop up, looking through high-powered microscopes. When they see something unusual they figure out what it is.
Unlike larger organisms, these almost microscopic invasives don’t have a commonly used name such as “alewife,” zebra mussel” or “fish-hook flea.” One of them carries the handle Mesocyclops pehpeiensis, the other is known only as: Diaphanosoma fluviatile.
The first one is a predatory species native to tropical and temperate areas of Asia. It feeds on other species of zooplankton and the larvae of mosquitoes. This little creature was found near Ohio’s East Harbor State Park.
Diaphanosoma fluviatile, a filter-feeding zooplankton originally from Central and South America and the Caribbean, was found in the Maumee River near Toledo Harbor. It is quite similar to some native species of zooplankton. While they don’t outwardly have characteristics that would make them impervious to predators because this new immigrant is acclimated to warmer weather, it may have a competitive advantage in the summer months.
Mesocyclops is believed to have arrived in the U.S. on aquatic plants from Asia. Researchers speculate Diaphanosoma could have hitchhiked with migratory birds.The arrival and staying power of both species in western Lake Erie remains a mystery to scientists who say it is the farthest north either has been tracked in the Western Hemisphere.
Though neither is considered an “official” invasive species because they have been found in low abundance compared with native zooplankton, they now join the more than 180 foreign species that have crept into the Great Lakes. If they show signs of spreading or out competing native species they may become an official invasive which will open the door to big bucks funding options to study them more in depth as well as to initiate control or elimination options.