Persistent Organic Pollutants in Our Precious Ocean
2017, High School, Prose
The classic 1870 science fiction novel Twenty-Thousand Leagues Under the Sea by Jules Verne presents the ocean as a vast expanse, full of wonder and infinitely resilient. While it is certainly true that the ocean holds a wealth of marvels, many of which have yet to be seen by human eyes, scientists have long since disproven the sentiment expressed in the novel that “nature’s creative powers … were greater than the power of man to destroy” (219). Yet, despite all the evidence, we have only recently begun to pay close attention to the problems that 99% of the Earth’s biosphere faces. For most of the history of environmental science, we have been preoccupied with our impact on land and air. Few bothered to find out, or even had the technology to find out, the scope of our impact on the far away, inky depths of the ocean. In fact, interest in marine environmental issues has lagged behind that in terrestrial ones by a century (Rozwadowski). However, the ocean’s impact on our everyday lives is enormous—and vice versa.
The sea provides us with an immense variety of ecosystem services that are estimated to be worth a minimum of $2.5 trillion USD (“Recognizing the value…”). Ecosystem services are “[n]atural processes that sustain human life and which depend on the functional integrity of natural communities and ecosystems” (Cain et al. 579). They can be classified into four broad categories: cultural, provisioning, regulating, and supporting. The ocean has provided cultural services through its influence on our society (”Ecosystem Services”). Its power and beauty have inspired countless artistic masterpieces throughout the ages. How would we have Moby Dick without the ocean? What would Greek mythology be like without Poseidon? Civilizations all around the world have been shaped by the sea, but for many, cultural services are far less important than marine provisioning services, which provide us with natural resources and put food on the table for billions around the world.
The ocean has been a source of wealth since time unmemorable. Sixty-four percent of the global gross national product (GNP) comes from the areas that are less than 100 km from the ocean (“Oceans, Fisheries, and…”). This same area contains 40% of the world’s population (“Percentage of…” 170). Many people are dependent on the ocean as a source of income. The World Bank estimates that one-tenth of the human population derives its livelihood directly from either fishing or aquaculture. This statistic does not even include those who indirectly rely on the ocean for tourism and business. Furthermore, the ocean is an important source of nutrition for billions of people; 16% of the world’s animal protein comes from the oceans (“Oceans, Fisheries, and…”).
We can intuitively appreciate the money brought in by the sea, yet this wealth pales next to the marine-regulating services, which are the benefits we receive from the ocean’s role in ecological processes (”Ecosystem Services”). The ocean accounts for half of worldwide net primary productivity, a measure of the amount of energy captured and made available to organisms (Cain et al. 578). In addition, it acts as a massive carbon sink, absorbing and storing 25% of the carbon dioxide released by human activities. This carbon absorption has significantly dampened the progress of global warming, though this service has its own costs (Heinze et al. 327-36). The sea also provides regulating services by impacting the climate. Ocean currents, aptly nicknamed “thermal conveyers,” are responsible for 40% of the heat transfer between the tropics and the poles and the creation of drastically different climates at similar latitudes. More locally, the marine regulating services help to moderate daily temperature fluctuations by cooling the land during the day and warming it during the night (Reece et al. 49).
In order to continually provide us with these services, the ocean must be able to sustain and maintain itself. This is the role of supporting services, which include activities such as nutrient recycling. Unfortunately, human activities have disrupted the ocean’s supporting services. The sea seems so enormous to us, so impervious to human alteration, that we have repeatedly misused it throughout the ages. Thousands of years ago, humans had already altered the coasts where they lived, but their populations were so small that they could only cause local harm. However, today, with our population exceeding seven billion, our activities are increasingly damaging the ocean beyond its capacity to recover. Overfishing has decimated marine populations; the ocean’s role as a carbon sink has caused its pH to fall; invasive species have reduced biodiversity; boat and sonar activity have made the ocean as noisy as New York City; our love of disposable products has dumped literally tons of trash into the ocean (Roberts 1-228). While these issues certainly must be addressed, perhaps no threat to the ocean is as pernicious and omnipresent as persistent organic pollutants (POPs).
POPs are a group of manmade chemicals that, as their name suggests, persist in the environment for long periods of time because they are not easily degraded by natural processes. They include compounds such as DDT, aldrin, mirex, and dioxins. Most are widely synthesized because of their usefulness in pesticides, plastics, and solvents, but some, such as dioxins, are the unintentional products of industrial processes. Recently, 12 POPs, dubbed “The Dirty Dozen,” were banned by an international treaty. However, the properties of POPs guarantee that they will be continue to be hazardous for decades, even after they have been banned (Johansen 11).
POPs are exceptionally harmful to marine life. In one lab experiment, phytoplankton productivity was depressed by 50% by polychlorinated biphenyls (PCBs), a type of POP, at a concentration of only one part per billion (Koslow 145). POPs have also been shown to be toxic to larger lifeforms, causing cancer, anatomical defects, and immunosuppression. For instance, belugas that live in or around the heavily POP-polluted St. Lawrence River have an unusually large number of afflictions, including rare cancers, deformed spines, and pneumonia. In addition to these malicious effects, POPs have also been shown to behave as endocrine disrupters (substances that mimic hormones). Male fish exposed to estrogen-mimicking POPs have been shown to become feminized, leading to reproductive failure (Johansen 134-40). Humans are not immune to POPs either. POP exposure has been linked to increased incidence of type II diabetes, heart disease, and chronic kidney disease (Lee 1235; Sergeev 756; Shankar). Furthermore, at least nine POPs are suspected of being or are proven to be carcinogenic (“Persistent Organic…”). Unfortunately, the toxic effects caused by POPs are inescapable because of their universal distribution.
POPs know no bounds. They are found virtually everywhere, from the trenches of the oceans to the glaciers of the poles. They owe much of their extensive presence to their semi-volatility. POPs can evaporate and condense within normal seasonal temperatures. During summertime, high temperatures allow them to evaporate and wander to far-flung places. When the atmosphere cools sufficiently, they condense and settle out of the air into a new area. If the new area at some point becomes hot enough, the POPs evaporate again and begin the cycle anew. This mode of travel is called the grasshopper effect, and it accounts for the accumulation of POPs in the poles. By roaming through the atmosphere, POPs can easily travel to the North and South poles, where the frigid temperatures cause them to condense. Unfortunately, since the poles are cold year-round, POPs that are deposited there are trapped, which presents a major problem for local seals, polar bears, and other marine life (Roberts 139).
But in spite of their presence in the remote poles, it would seem impossible for POPs to be able to reach the dark, deep ocean. Because POPs are lipophilic (fat-loving), they are largely insoluble in water and therefore have difficulty diffusing to the sea floor. However, the lipophilic property of POPs allows them to collect in animal feces and fat. Animal pellets and carcasses sink in water, eventually arriving—laden with POPs—at the ocean bottom (Koslow 143-51). Furthermore, POPs have a high affinity for plastics and become concentrated in them (Rios et al. 1230). When plastic particles sink, they bring POPs along with them. Sadly, just like in the poles, POPs on the ocean bed are trapped; there is very little exchange between the deep sea and the surface (Koslow 144). In fact, the level of PCBs in the Mariana Trench (10,994 m below the surface) was equal to the level found in Japan’s Suruga Bay, an infamous site of pollution (Carrington).
The poles and the deep ocean are not the only places where POPs accumulate, though. These malicious chemicals accrue in animal fat due to their lipophilic nature. Organisms at the bottom of the food chain acquire POPs from the environment and are then consumed by predators, who are in turn devoured by higher predators. However, animals that consume contaminated prey cannot purge themselves of POPs. Since POPs are manmade, evolution has not yet devised a way to effectively remove these compounds from the body. As such, the level of POPs in an animal rises as it eats more prey and as it occupies higher levels in the food chain. This phenomenon, called biological magnification, poses a serious threat to the animals that are near the top of the food chain, including humans (Reece et al. 1256). Occasionally, POPs become so concentrated in these animals that their bodies are condemned as toxic waste. Biological magnification is especially detrimental to marine mammals, who have a large amount of body fat and tend to feed high up on the food chain. Furthermore, marine mammals produce fatty milk, which passes the POPs accumulated in the mother’s body to the newborn. This POP-laced milk results in higher infant mortality, as well as higher levels of toxic POPs in the next generation’s adults. Likewise, humans also pass along POPs to babies through milk, which can harm a child’s development. In fact, children with mothers who have higher levels of POPs in their bodies tend to be less intelligent (Johansen 138-39; Roberts 141-142).
Once we grasp the long-lasting and malicious effects caused by POPs, it is truly depressing to imagine a world where POPs are amassing in remote places, crippling marine life, and hampering the vital ocean ecosystem services. After all, if POPs are so obstinately immune to degradation, how can we possibly destroy them? How will we even reach the isolated regions of the poles and ocean bottom to clean them up? Is there even a way to stop biological magnification? It seems as if our good-intentioned development of POPs has cursed us and the ocean to a slow and painful death. Still, we have time to redeem ourselves. Human ingenuity produced POPs, and human ingenuity can dispose of them.
Perhaps the single most important action we can take is to limit further production and use of POPs. While POPs do have incredible longevity, they eventually decompose. Without further production, they will eventually disappear from the environment, albeit very slowly. The Stockholm Convention of 2001 was a monumental step towards international cooperation to end POP production. As of the time of this writing, 152 countries have signed the convention’s treaty that originally banned 12 classes of POPs, dubbed “The Dirty Dozen.” Sixteen new chemicals have since joined the Dirty Dozen as POPs whose production should be limited. However, practical considerations limit the treaty’s effectiveness. One of the greatest challenges to eliminating POPs is that there are often no alternatives. The Stockholm Convention only authorizes the elimination of the POPs listed in its Annex A. The other chemicals are only restricted in their use and release, because either they are vitally important or they are generated by essential industrial processes. Among this group of POPs is DDT. Half a century after Rachel Carson published Silent Spring, we still have no better, cheaper alternative to DDT. Many developing countries even today continue to rely on DDT to control malaria. As such, the Stockholm Convention allows DDT’s continued use (Stockholm Convention).
As DDT shows, in order to wean ourselves off of POPs, we must learn to survive without them. Therefore, we must make scientific research on affordable substitutes a priority. At the same time, we should remember to bolster our efforts in developing clean-up methods. By combining decreased production and increased destruction, we can rid the Earth of POPs at a much faster pace, a matter of great importance for the endangered species threatened by them. However, scientific research is always expensive, and most countries do not have the resources to produce substitutes for all POPs. Combatting POPs will require full international collaboration, an endeavor that many countries may be reluctant to undertake. Still, the world has already proven that it can accomplish great scientific tasks when nations cooperate. One well-known example is the Human Genome Project, which involved six nations and managed to sequence all of the three billion bases pairs of the human genome in only 13 short years (“Who was…”; “The Human…”). Nonetheless, in our race against POPs, we still need to exercise caution. We must make certain that the solutions we develop do not become problems themselves because substitutes by definition share properties with what they are replacing. Thus, careful environmental screening is a necessity in order to prevent us from being trapped in a vicious cycle of solving problems with new problems (Stockholm Convention).
We should not only directly combat POPs but also mitigate POPs’ current effects by developing and implementing other programs, such as cleaning up plastics and prohibiting ocean trawling. As mentioned before, POPs tend to concentrate in plastics, which carry POPs to the sea floor. Plastics are also an important source of ingested POPs, as many marine animals mistake plastics for food (Rios et al. 1236; Carrington). Ocean trawling further exacerbates problems caused by POPs because it disrupts sediment deposits, recirculating the POPs that have been trapped there for decades (Roberts 264). By removing plastic debris and restricting trawling, we can eliminate mechanisms by which POPs become more dangerous and ease other problems that further stress the ocean.
The ocean is of such immeasurable importance to human beings because it enriches our culture, provides for millions of families, and plays an indispensable role in the Earth’s processes. It is also the home of rich and diverse marine life, many of whom may be driven to extinction by POPs before their wonders are revealed to us. We must not let POPs contaminate the jewel that is our ocean. While POPs are pernicious, omnipresent, and resistant to degradation, they are not invincible. In fact, the baby steps we have taken have already bore fruit. The atmospheric levels of the Dirty Dozen have begun to slowly decline in the years since the implementation of the Stockholm Convention. We have also discovered promising new methods to remove POPs, such as bacteria that have the unique ability to break down PCBs (“Technological…”). Nature’s creativity may be no match for humanity’s destructive power, but human ingenuity is definitely more powerful than POPs.
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I decided to enter this Contest because environmental science has always been a passionate, albeit sometimes depressing, topic for me. When I started this project, I read about all types of pollution, from noise to plastics. Most topics brought up such visually dramatic images: birds covered in oil, seals slowly strangled by plastic, and so on. However, when I read about POPs, no startling images came to mind. Yet, as I learned more, I began to grasp what a scourge they are to the oceans. I became determined to write my essay on these invisible chemicals that cost us so much and so silently. Nonetheless, I had a hard time connecting the topic to my life experiences. After all, I live in Shoreview, Minnesota, smack in the middle of North America and 1,000 miles away from the nearest beach. Then I realized that millions of people around the world feel the same way. Why should a farmer in Iowa care about poisoned fish? Why should someone in Nepal feel concerned about chemicals in an ocean trench? I became convinced that I had to explain why the ocean is important and that it affects us all no matter how far away we are from it. It was my hope that my essay will prove to myself and others that repairing the havoc that POPs have wreaked on the oceans is urgent and worthwhile—because sometimes the greatest challenge to cleaning up pollution is that we just don’t care.