Science Results : Daily Update

Daily Update | Current SEA Research

July 12, 2010

By Giora Proskurowski

One question that I haven't addressed in this space is: What are the implications and consequences of having plastic debris in large regions of the Earth's oceans? One reason I am somewhat hesitant to discuss this is that I feel that the state of our understanding of the problem is in such infancy that my treatment of this topic is bound to be incomplete. But that is just a typical scientific cop-out – "We need more data before we can answer any questions" – and there is a real need for guidance from those that are actively involved in quality research.

However, a measured scientific appraisal can rarely compete with shocking simpler portrayals, such as the widespread notion that the "Great Pacific Garbage Patch" is a floating island or continent of trash. While the media hyperbole surrounding this topic increases public interest and concern, I believe that what we know, or can reliably predict, is more than enough to convince skeptics that something needs to change – without the exaggerations.

It is easy to brush off the topic of plastic pollution in the ocean. It occurs thousands of miles from land, in regions of the planet that are rarely visited by humans, and relatively sparsely populated by marine life. It is also easy to pass off responsibility – "I recycle," or "It must come from some other (developing) country," or "It is all fishing- or marine industry-related waste." While there may be kernels of truth in all those arguments, the reality of the situation is that open-ocean plastic pollution occurs over incredibly large regions of the Earth, has widely distributed point sources, and – because the oceans connect the whole globe – has far reaching consequences.

From SEA's nearly 25 years of plastic data from the North Atlantic, we know that the region of high concentration of plastic in the Atlantic has an area of at least 1.5 million square miles (high concentration defined as greater than 10,000 pieces/square kilometer). That area is almost certainly much larger, as we have yet to find the eastern boundary of this region, despite extending our map of plastics 1000 miles east on this expedition. In eight years of sampling the North Pacific subtropical gyre, our data suggest a similarly large region exists there, about 1.3 million square miles (at the same concentration as above). However, the Pacific region could be easily doubled in size, as our cruise tracks have explored only the northwest portion of the predicted region.

Plastic pollution in the open ocean has been documented to be a threat to marine wildlife. Entanglement in plastic debris has prematurely ended the lives of countless swimming and flying animals of all types. Seabirds, fish, turtles, and other large animals have all been observed to ingest plastic in the ocean. Many plastics contain toxic additives, and plastics attract and accumulate persistent organic pollutants (POPs), makes these fragments a bigger threat to the animals that eat them. Plastics can also be a safe harbor for many animals; serve as an attachment point for fish eggs, barnacles, many types of larval and juvenile organisms; and therefore act as a transport mechanism that may spread harmful, invasive, or exotic species to new locales.

What we don't know is just as scary. Do these POPs bioaccumulate in the tissues of small fish, and get amplified up the food chain? Do plastics affect phytoplankton growth? Does the base of the animal food chain, the zooplankton, consume the small plastic fragments, and what is the effect? What happens to the plastics as they degrade to smaller and smaller pieces? It is likely that the answers to each of these questions is "Yes." Understanding to what degree these processes affect marine life is the next step.

Given the massive area over which plastic pollution occurs, the effects of this pollution are scaled up dramatically. The incredibly massive scale of the ocean is tricky to grasp. While an ounce or so of plastic in our net tow doesn't seem like a lot, when scaled up at 21 pounds per square mile, you quickly get to staggering numbers when discussing regions of a million square miles. Similarly, the effect on the biology may not seem like a lot on a meter-to-meter basis, but could easily be devastating on an ecosystem-wide scale.

Because the oceans are always in motion and act as a global connector, no oceanic phenomenon is truly localized. Thus, what happens in the middle of the Atlantic may have repercussions across the globe. It is difficult to predict every consequence of having millions of pounds of plastic debris in the Atlantic. However, given what we know, our best hope is to keep the problem from getting worse. For that to happen, continued study of the ocean system is needed to give policymakers and the public the information they need to make wise choices about how to live within the natural world.