Zebra Mussels: A Warning Tale

By Alexander Pralea, Editor

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A ship begins the arduous journey from Istanbul in along the Black Sea, filling its ballasts with water to maintain its balance. Inflated with water, the ship voyages to ports along North America, burrowing deep into the Great Lakes. There it releases its full ballasts, releasing countless species into the to waters. Most detrimental of the consequences of this process has been the introduction of the invasive Zebra and Quagga mussel species into North American waters, which have damaged native ecosystems.

With the silence and speed of the plague, the Zebra mussel species infiltrated North American waterways as early as the 1970’s. The existence of manmade canals connecting the Great Lakes to the Hudson and Mississippi Rivers facilitated this process by opening a whole network of tributaries for these pests to enter. Without the limiting factors of its previous environment, the Zebra Mussel population multiplied, much to the harm of the indigenous species of mussels that could not compete with this species undergoing exponential growth. Not only did it outcompete the native mussel species, but it also threw the entire ecosystem off balance due to its voracious appetite. It devastated the population of phytoplankton and in turn that of zooplankton, the main predator of phytoplankton, and that of the fish that preyed on zooplankton. The problem was further worsened by the remaining phytoplankton’s inability to fulfill an important role due to their reduced numbers: photosynthesis, the production of oxygen and glucose from carbon dioxide and water. Without phytoplankton, fish lacked enough oxygen to respire. Compounding this was the fact that Zebra Mussels shifted the concentration of nutrients to the benthic zone (the lake’s bottom), thereby causing eutrophication, or the excess growth of plants that steal even more resources from fish, which decimated fish populations. In turn, this wreaked havoc on local economies as fisheries failed to be productive and various structures were destroyed by these mussels. Recently, the introduction of the Quagga mussel has limited and even reversed the success of the Zebra Mussel, but it has continued to spell doom for the local communities of fish and shellfish whose populations it still threatens.

Today, the rapid spread of the Zebra and Quagga Mussel serves as a warning story of the dangers of negligent human exploitation of the environment. Recent legislation has emerged to combat the trend of releasing ballast water in freshwater ecosystems, which has helped control the Zebra and Quagga mussel problem, but this effort fails to account for the ecological damage caused by humans elsewhere. Farmers’ overreliance on pesticides leads to run-off in drinking water, which, in addition to dangering human health, leads to excessive algae growth that imperils fish populations and precipitates eutrophication. Mass logging across the Amazonian and Bornean rainforests destroys the habitats of millions of species and leaves the acidic, nutrient-poor soil of rainforests unusable for agriculture. Overall, humans are destroying Earth’s biodiversity at an unprecedented rate through their carelessness and unchecked population growth, heading the Earth to its next great extinction. Anthropogenic climate change worsens this trend; natural selection does not allow organisms to adapt to fast changes in temperature, meaning that many organisms will go extinct even with human intervention. The US’s leaving the Paris Climate Accord and the effective dismantling of the EPA through the weakening of the Clean Water Act of 1970 sets the world up for a dangerous future in which our posterity cannot experience the same life as we can. Fortunately, the world has shown it is possible to address such issues, as evinced by the success of the Montreal Protocol of 1987 in limiting the global use of substances that harm the ozone level. The United States’ turn to isolationism at a time during which its global presence is needed to help reverse or decelerate climate change is disheartening, but if the global community binds together, it can slow down the rate of species extinction and limit ecological damage.





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