(David Lawrence/Sea Education Association)
The Sea Education Association, based at Woods Hole, recently discovered more than 48,000 plastic fragments in the Atlantic Ocean during an expedition. But researchers fear that might be only a small sample of a bigger problem. SEA answers some questions and answers about ocean debris in this Q&A put together by the group's researchers.
Q. Where does the plastic and other marine debris come from?
A. In a variety of ways. From land, trash may be carried to the ocean in rivers or storm and sewage drains, swept from the beach by waves and surf, or blown offshore by winds, especially during heavy storms. Trash may also come from ships or offshore platforms, although dumping of plastic at sea has been banned since 1988. We don’t know how much marine debris enters the ocean, or whether most of it comes from land or from vessels at sea.
Q. What does this plastic debris look like, and what kind of plastic is it?
A. The majority of samples we collect are small fragments less than 1 centimeters in size – no bigger than your smallest fingernail – with a mass less than 0.15 g, or about 1/10th the mass of a paper clip. In most cases it is impossible to know what kind of object the plastic pieces came from. The most recognizable pieces are fragments of fishing line and industrial resin pellets (the “raw material” of consumer plastic products).
Physical properties of plastic samples collected by SEA in the Atlantic Ocean indicate the collected material is made of high density polyethylene, low density polyethylene, and polypropylene, which are used to make common household items such as milk jugs, plastic bags, and drinking straws. These materials have a density less than that of seawater, causing them to float on the sea surface.
A. The term “garbage patch” is very misleading – there are no large islands of trash floating in the open ocean. Most of the floating marine debris is not even visible from the deck of a ship because it is so small. There are regions of the ocean where floating debris (natural or man-made) accumulates due to the movement of ocean currents. High concentrations of plastic debris have been observed in these “convergence zones” in the North Atlantic and North Pacific Oceans, where currents driven by the wind converge or come together. No one has been able to accurately measure the full size of these accumulation regions – not only are they are far offshore and very difficult to access, but boundaries may shift in time due to the ever-changing ocean conditions and the varying (and not well-known) sources of debris.
Q. Why is plastic in the ocean a problem? Does it affect marine organisms?
A. The debris can threaten marine organisms through entanglement, especially by large debris such as derelict fishing gear, and by ingestion in organisms ranging in size from zooplankton to fish and larger animals such as sea turtles and seabirds. Additionally, plastics create a habitat for microorganisms and other species and can transport potentially invasive species to new regions of the ocean. Plastics are known to carry organic toxins and may be responsible for the transfer these and other chemicals to marine organisms.
Q. What happens to the plastic? Does it break down? Is anyone going to clean it up?
A. We don’t know how long plastic remains in the ocean. Most plastics become brittle when exposed to ultraviolet light and break down into smaller and smaller pieces, sometimes referred to as “microplastics”. No one knows just how small these pieces become – they are very difficult to measure once they are small enough to pass through the nets typically used to collect them. Current research suggests that most commonly used plastics will never fully degrade in the ocean.
Because most of the plastic in the ocean is in very small fragments there is no practical way to clean it up. One would have to filter enormous amounts of water to collect a relatively small mass of plastic – in a typical net tow that filters about 120,000 gallons of water, the plastic pieces collected would fit in the palm of your hand. In addition, using nets would also remove a “by-catch” of microscopic plankton and other organisms that are important to the ocean ecosystem. This could end up causing more harm than good.
Q. What is being done to address marine debris in the United States and around the world?
A. The National Oceanic and Atmospheric Administration has supported more than 140 projects to address marine debris across the United States. Many other organizations are working to raise awareness, clean up marine debris on beaches and in the ocean, and reduce the input of debris into the oceans through “Reduce, Reuse, and Recycle” campaigns.
This is how you can help, no matter where you live: Reduce the amount of trash you produce; choose items you can reuse over disposable products; recycle items if you must dispose of them.
SOURCES: Sea Education Association, NOAA
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