"This story takes you beneath the lakes' shimmering surface and illuminates an ongoing and unparalleled ecological unravelling of what is arguably North America's most precious natural resource." Saved from a century of industrial pollution by the Clean Water Act, the Lakes are now home to 186 nonnative species because the EPA allowed seafaring ships to dump their ballast water, thus introducing, among other species, two small mussels, the zebra and quagga. The mussels have cleansed the water, but killed native fish populations and have spread west into the Mississippi basin because of the Chicago Sanitary Canal.
Prior to the completion of the St. Lawrence Seaway lock system that opened up the Lakes to traffic from the Atlantic, the Lakes were isolated by Niagara Falls and the drop of almost 800 feet from the midwest to sea level. The only breach of that defense had been the Erie Canal and it is believed that the canal was the route taken to the Lakes by the sea-lamprey, which virtually eliminated the lake trout in the 1930's and 40's. The alewife followed, and by the mid-60's, alewives were 90% of the fish mass in Lake Michigan. A solution was to stock the Lakes with Pacific silver salmon, a predator fish that would feast on the alewives and was also a fun sport fish. That worked for decades until the alewives began dying off because the mussels were eating all the plankton. Without the alewives to feed on, the salmon numbers dropped precipitously. The invasive zebra mussel, a Black Sea native that arrived in ballast discharge, was first seen in the 1980's. It clogged water intake pipes and its cousin, the quagga, cleansed all the plankton in the water leaving the Lakes, particularly Michigan, clear as a glass of water and without many fish. One suggestion to solve this problem is to preclude the 'salties' from entering the Lakes, and some have pointed out that the cost of shipping goods offloaded somewhere on the St. Lawrence would be a fraction of what we've spent protecting our waters from invaders.
Another threat to the Lakes comes from the Mississippi basin, where the Asian carp has been reproducing and marching north for decades. Because of the mid-19th century Chicago Ship and Sanitary Canal, which reversed the flow of the diminutive Chicago river to the south and connected the Lakes to the Des Plaines River, there is no natural barrier to keep the carp out of the Lakes. The Corps of Engineers has placed an electric barrier just south of Chicago in an attempt to keep the carp out. No one knows if it will work indefinitely, and there is serious concern about the devastation the carp would wreak on the Lakes. Conversely, the Canal also allowed the migration of the mussels into the Mississippi basin, where they are causing the same problems that they've caused in the Lakes.
As for the future, the author offers up the hope that the native fish of the Lakes are evolving, finding new food sources and making a comeback. Specifically, both whitefish and trout are reviving. There is even a chance that science can create a gene to kill the invasive species that will not harm the water or another species. Clearly, time will tell, and since the Lakes hold 20% of the world's fresh water, one can only hope that somehow we do not continue to despoil these treasures.
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