The oceans are awash in garbage, and it is taking a toll on the environment.
Even places considered natural paradises — World Heritage sites and areas where sea turtles lay their eggs — are becoming clogged with fishing nets, bottles, cans and other forms of trash.
Of particular concern are microplastics, the detritus created when plastic is broken down into tiny pieces by ultraviolet rays. The true scale of the problem is not fully known, but many experts have pointed out the toxicity of such waste for marine lifeforms, the potential deleterious effects on ecosystems and the health hazard this poses to humans.
Marine trash can be broadly classified into two categories: natural products such as plants, and man-made items such as plastic. The issue was discussed at a summit of Group of Seven leaders in June, and the international community is becoming cognizant of the urgent need to develop measures to elucidate the true nature of the problem and reduce the volume of garbage in the world’s waters.
Junk of all forms can be found drifting off Japan’s shores, including plastic bags and bottles, furniture, tires and hypodermic needles. It seems that as fast as people pull the waste out of the water, more appears. And the cycle of destruction goes on, with seals and sea turtles becoming enmeshed in old fishing nets and fish and birds gobbling up pieces of trash.
Japan’s Environment Ministry conducted a study of marine trash that drifted ashore in seven areas of the country every year for five years through fiscal 2014. The study focused on Kamisu, Ibaraki Prefecture; Hakui, Ishikawa Prefecture; Awaji, Hyogo Prefecture; Shimonoseki, Yamaguchi Prefecture; Tsushima, Nagasaki Prefecture; Minami-Satsuma, Kagoshima Prefecture; and Ishigaki, Okinawa Prefecture.
Over the five-year span, some 48.1 tons of junk washed up on those shores. Much of it was plastic, which accounted for 47.3% of the total by weight. When broken down by number of items, plastic accounted for even more, at 60-90%.
Polyethylene terephthalate bottles were the most common type of plastic trash. Most of those that washed up on the Japanese shores facing the Sea of Japan and the East China Sea drifted over from South Korea and China, while on the coastlines facing the Pacific Ocean, the bulk of the bottles came from Japan. Along the coasts of Shimonoseki and Tsushima, more than 50% of the bottles were from South Korea, while at Ishigaki over 80% were of Chinese origin. In contrast, virtually all the PET bottles that drifted ashore at Awaji, along with more than 80% of those at Kamisu and 70% of those at Minami-Satsuma, originated from Japan.
Tests conducted on plastics found drifting in the oceans have found high concentrations of polychlorinated biphenyl, a toxic substance. There have even been reports that the fat found in seabirds that have swallowed plastic contains very high levels of harmful chemicals. The chorus of voices expressing concern about the maritime ecosystem continues to grow as such reports become more numerous.
Another potential problem that has been pointed out is microplastics. These small fragments — 5mm or smaller — can ride ocean currents for great distances. Some experts say the situation is so dire that the oceans are already a “soup of microplastics.”
These particles impact all living organisms. Recent research has found that plankton, the lowest player in the marine food chain, ingest microplastics and that fish consumed by people often eat microplastics.
Not only does the plastic itself contain toxic substances, but it also readily absorbs substances that are harmful to humans, such as the pesticide DDT.
Kyushu University professor Atsuhiko Isobe, an expert on ocean trash, sounded a warning: “There are no reports yet of this having an effect on humans. But … if the density of microplastics floating in the seas continues to rise, we don’t know what could happen in the future.”
Last year, the Tokyo University of Marine Science and Technology and Kyushu University conducted a survey of maritime trash floating within 200km of land at 45 sites across Japan. Researchers observed the garbage with the naked eye from ships and used nets to collect trash floating on the surface. According to their findings, each ton of seawater contains an average of 2.4 pieces of microplastic.
When Kyushu University conducted a similar survey in the Inland Sea from 2010-2012, the average was just 0.4 piece. But in the more recent study, the amount discovered had increased in roughly half the locations.
“We thought there would be more trash closer to spheres of daily existence, but that is not necessarily true. The problem has already spread to oceans across the globe,” Isobe said.
According to a report released last year by the United Nations Environment Program, plastic particles are found in such everyday items as toothpaste, washing gels and facial cleansers. These particles become mixed with wastewater and could find their way to the oceans.
The extent to which microplastics have spread is not yet known. But as Isobe pointed out, “There have been reports of microplastics floating in the middle of the Atlantic and the Pacific.”
This fiscal year, Japan’s Environment Ministry — working with Kyushu University, Ehime University, Tokyo University of Marine Science and Technology and Tokyo University of Agriculture and Technology — will launch a study aimed at grasping the state of marine trash in the Antarctic Ocean. This is a departure from earlier studies, which have largely focused on the seas around Japan.