The creation of locks and canals in the 1800s, and eventually the St. Lawrence Seaway in 1959, facilitated the linkage of all 5 Great Lakes to the St. Lawrence River, Gulf of St. Lawrence, and, subsequently, the Atlantic Ocean. The engineering nous required to construct these projects and, crucially, to open the Great Lakes to transatlantic commercial shipping was and still is remarkable. It made the import and export of North American and international commodities immeasurably faster and cheaper; in turn, this helped grow cities, towns, and villages throughout the Great Lakes. However, opening the Great Lakes to ships emanating from foreign bodies of water also opened them up to non-native aquatic organisms. These “foreigners” usually enter the Great Lakes via the discharge of ballast water from commercial vessels as they pass through the locks and canals, and some of them have had a calamitous impact on the Great Lakes Ecosystem.
Two of the costliest invasive species to infiltrate the Great Lakes via its canals are, oddly enough, two of its smallest ones. The common names of these species are the quagga and zebra mussel. They are about the size of a fingernail, attach to solid substrate via their lone “foot,” and are filter feeders. So, what’s the problem with them? They sound innocuous enough, right? Unfortunately, that is not the case! Their presence has led to the rapid decline of native fish such as lake trout, and they assemble in such vast numbers that they are capable of clogging pipes of all varieties. For instance, they’ve clogged drainage pipes from lakeside industries, hydropower facilities, and even drinking water reservoir intake pipes. All in all, it is estimated the fingernail-sized mussel invaders have cost communities and businesses approximately 5 billion dollars, and this does not include the ecological damage to the natural ecosystem, which can’t be quantified.
So, you may still be wondering what factors allow these mussels to inflict so much economic and ecological damage to the Great Lakes Ecosystem. Well, there are essentially four critical components that facilitate this havoc. The first is they have no native predators in the Great Lakes, unlike in their native water bodies in Russia and Ukraine. Second, they have an astounding reproductive capacity. For example, a single female can produce up to one million veligers per year (a veliger is their microscopic offspring), and they can live up to five years. So, you can do the math from there—that’s a lot of mussels. Third, they are filter feeders, which means they eat the phytoplankton and zooplankton that make up the base of the Great Lakes food chain and consequently starve fish that directly or indirectly feed on the plankton. Lastly, they can attach to essentially any solid substrate, whether natural or manmade, and can thrive even while living amongst their own species at exceedingly dense numbers.
Moreover, the negative domino effect of these components is laid out here. The lack of native predators and the mussel’s incredible reproduction rate mean their populations have exploded to the unfathomable number of 10 trillion throughout the great lakes. This inordinate number has led to them depleting the base of the food chain—phytoplankton and zooplankton—that native fish like lake trout eat during their early stages. Also, once lake trout mature they begin eating smaller fish that also rely on phytoplankton and zooplankton. Thus, the mussel’s diet essentially starves both smaller feeder fish and native fish such as trout, which in turn has produced a devastating trophic cascade that has vastly altered the predominant biomass throughout the Great Lakes. In addition to the disruption of the food chain, these invaders have cost businesses across the Great Lakes hundreds of millions of dollars in damage to infrastructure which, as previously mentioned, is largely due to the mussels attaching to and clogging pipes. The cost of constantly needing to remove them from essential pipes and other surfaces is mainly what leads to these enormous sums. Thus, while the list presented above is rather simplistic and certainly does not reflect all the costs and damages inflicted by these mussels, it does highlight some of the pertinent issues that exist due to their presence in the lakes.
Alright, so the plot of the zebra and quagga mussel hasn’t been overly uplifting thus far. However, I assure you that will change! The Great Lakes web of life isn’t vanishing just yet, and I wanted to use the mussel example to show how resilient ecosystems, even those as vast as this one, can be. Moreover, these mussels are a lesson that politicians, lawmakers, and citizens alike can all learn something from if we only delve deeper into the underlying issues surrounding them and really all invasive species.
In recent years, the numbers of native fish, such as lake trout and lake whitefish, have started to recover due to a combination of conservation efforts and, more notably, a change in their diets, especially that of the whitefish. The whitefish is toothless, normally scours the lake bottom for food, and does not eat other fish. Additionally, their normal diet used to largely consist of a minute, shrimp-like organism that covered the lake bottom. However, the quagga and zebra mussel all but eliminated the shrimp’s food source, plankton. Thus, the shrimp declined and consequently the whitefish did as well. But then, something extraordinary happened—fishermen and biologists noticed that both the numbers and size of the whitefish were increasing. In turn, they attributed this increase to a remarkable alteration in their feeding patterns. For instance, the whitefish, which remember was not piscivorous, is now eating a small fish called a goby, and it appears that their intestines are adapting to this new diet by growing larger, which allows them to more efficiently and effectively process this fish. Furthermore, the goby, which is an invasive, is one of the only fish in the Great Lakes that is capable of eating—yes, you guessed it—the quagga and zebra mussel! They possess molar like teeth, which allow them to grind through the hard shells of the mussels. There are many people who believe the goby may be one of the answers to help reduce mussel numbers, while also providing larger, native fish such as trout, bass, and whitefish with a novel but abundant food source. This example displays that even amidst the chaos and seemingly hopeless circumstances, aquatic life can bounce back. If given the chance, an ecosystem such as the Great Lakes can return to a healthy equilibrium. It won’t happen overnight, but it is more than capable of doing so if we let nature do the brunt of the work, while we watch and intervene only when absolutely necessary.
Furthermore, in addition to the fish of the Great Lakes adapting, politicians, lawmakers, and citizens appear to be likewise adapting. For example, one program based in Wisconsin, called “Clean Boats, Clean Waters,” trains inspectors so that they can perform educational outreach programs in their community, check recreational boats for invasive species, and distribute information to the general public. Also, since the mussel invasion started 30 years ago, regulations governing ballast water discharge in commercial vessels have strengthened considerably. Building on the Clean Water Act, the Coast Guard and Environmental Protection Agency, in concert with environmental advocates and politicians, have made it mandatory for all boats entering the St. Lawrence Seaway to discharge their ballast water in the ocean. The idea is that most organisms will be expelled from the ballast tanks and any ones left will be killed by the influx of saltwater. It is not foolproof, but it appears that it has been fairly effective since the number of new invasive species has steadily declined since ships began doing this. Additionally, there is legislation in the works that would make the installation of cleaning systems designed to kill all organisms in ballast tanks using things such as ozone, chlorine, and UV mandatory on all commercial ships entering the seaway after 2021. However, since there is no official deadline date set for ships to have these installed, it remains to be seen if this will end up being upheld and adhered to in the coming years. Regardless though, people from many different backgrounds throughout the Great Lakes are ascertaining the grave threat that invasive species pose to this ecosystem. Rather than sit idly, action is being undertaken now to try and prevent the next invasion.
Wrapping up, I think the moral of this story is that vigilance and learning from past mistakes are vital to protect the Great Lakes and natural areas around the globe. We can’t undo what has already been done by quagga and zebra mussels, but we can analyze the situation for what it is and take preventative measures to ensure this does not happen in the future. We can protect the Great Lakes and offer the negatively affected organisms a helping hand. However, we should also remember that quite often nature is extremely resilient and often has the best solution to countering problems induced by humans. In the story of the quagga and zebra mussel, we see bits and pieces of all the aforementioned topics. I think, most importantly, we also see a positive change in the collective mindset of citizens, politicians, and even some industries. A change in mindset that tends toward proactive, as opposed to reactive, measures in terms of protecting the integrity of the awe-inspiring and bountiful ecosystem that is the Great Lakes.
What laws or methods have you heard of being implemented to mitigate the spread and/or impact of invasive aquatic organisms locally or abroad?”
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