The Great Lakes have been the unwilling host of more than 130 invasive species
. These introductions were mainly the result of humans unwittingly giving free rides via transoceanic vessels to aquatic invasive species.
Let's name a few of the top invasive species: the zebra mussel (Dreissena polymorpha
) and its close cousin the quagga mussel (D. rostriformis bugensis
), round goby (Neogobius melanostomus
), Asian carp (Cyprinus carpio
), water chestnut (Trapa natans
), and the spiny water flea (Bythotrephes
sp.). The zebra and quagga mussels
have received much attention because their high-density colonies have restructured nutrient dynamics in Lake Ontario, and they are implicated in the demise of native freshwater unionid mussels. Not too long after the zebra mussel became a household name, the round goby first appeared in the St. Clair River in 1990, and since that time has spread to all five Great Lakes. This species, which comes from the Ponto-Caspian region, is an aggressive benthic fish that is associated with lowered native fish abundances, such as mottled sculpins, in habitats where this invasive fish has colonized. Round gobies are very territorial when spawning and nest guarding occurs from June to September. In fact, they are so aggressive that they have driven mottled sculpins to deeper waters to the point of local extinction.
At right is a map of the Ponto-Caspian region, where round gobies and zebra mussels hail from!
Honestly, when you takes into account point and non-point source pollution, eutrophication, invasive species, and climate change, the future of the Great Lakes looks pretty depressing. I mean, the zebra mussels are here, and they are not going anywhere. Lake Ontario is the lake I am most familiar with, and I remember walking on the beaches and seeing zebra and quagga mussel shells all around me.
When I took Limnology (study of inland waters) during my first semester of grad school, one of the main points our professor drove home was that Lake Ontario will never be the same as it was 50 or 100 years ago. Instead, Lake Ontario — and as far as I can tell, all the Great Lakes — will take a new path, and this path could take 100 years until equilibrium is reached. As invasive species take over the near shore and deeper zones, food webs will be altered and some native fish species will probably decline to the point of extinction.
It is sad, and it is overwhelming to think that human influence has altered the Great Lakes at a faster rate than all the processes it took to form these lakes in the first place.
This is a picture I took over the summer of 2012; if you look closely you can see all the zebra mussel shells. This was taken at a small beach on Lake Ontario.
Despite these environmental, moral, and for me, philosophical dilemmas, there is hope for the Great Lakes. On Jan. 6, 2014, Congresswoman Louise Slaughter, co-chair of the bipartisan Great Lakes Task Force in the U.S. House of Representatives, released a positive statement regarding the efforts of the Army Corp of Engineers to stop aquatic invasive species in their tracks. The Army Corp of Engineers released a report to prevent the spread of aquatic invasive species such as Asian carp between the Great Lakes and Mississippi River basins. This report, formally called the Army Corp of Engineers (Corps) Great Lakes and Mississippi River Interbasin Study (GLMRIS)
, provides several options to prevent Aquatic Nuisance Species (ANS) from spreading between the Great Lakes and Mississippi River basins. However, this report does not select a recommended plan.
As part of the GLMRIS report, six steps are outlined as the underlying study principles in the efforts against ANS. The six steps are as follows:
1) Identifying problems and opportunities
2) Inventorying and forecasting conditions
3) Formulating alternative plans
4) Evaluating alternative plans
5) Comparing alternative plans
6) Selecting a plan.
As part of Step 1, this report delineates four major problems of invasive species:
1) Impact from ANS
2) Transfer of ANS through aquatic pathways
3) Transfer of ANS through non-aquatic pathways
4) Impacts of new ANS.
Some of the most pertinent impacts of invasive species are reduced species richness and lower biodiversity in areas where they reproduce and take over. One of the major factors at play in the control of ANS is shared boundaries, which “are recognized in terms of potential ANS transfer between the United States and Canada and between the Great Lakes basin and the Atlantic Slope drainage and between the Mississippi River and the Gulf of Mexico.”
That was a mouthful, but bear with me. Basically anywhere where there are basins or watersheds that border the Great Lakes and Mississippi River, basins are termed as shared boundaries.
The boundaries of the Great Lakes and Mississippi River basins. (Photo: www.umesc.usgs.gov
Well, there are a lot of problems associated with ANS, but there are plenty of opportunities to control them. GLMRIS names four opportunities, such as control of ANS, control ANS transfer through aquatic pathways, control ANS transfer through non-aquatic pathways, and control new aquatic nuisance species. To control new aquatic invasive species effectively, there needs to be early detection and rapid response. In the report it states that the most effective way to prevent movement of ANS from the Great Lakes basins to the Mississippi River basins is hydrological separation. Completely separating the Great Lakes and Mississippi River basins would involve assessing and implementing effective measures along a span of 1,500 miles and smaller aquatic pathways.
Clearly, there is hope for managing aquatic invasive species, but, just as lakes take a long time to form and for intricate processes within them to occur, it will take substantial years and funding to implement effective control strategies. As transoceanic shipping is bound to continue and bring in goods and unexpected hitchhikers through the St. Lawrence Seaway, there will be more aquatic invasive species to battle. There is not just one answer to the issue of invasive species, and this report fully admits that there is uncertainty with any control measure. All we can do right now is making sure we can do our part to hamper the spread of aquatic invasive species.
Image credit for black & white map: University of Toledo