How Is Plastic Trash Affecting the Ocean Food Chain?

According to Carey Okrand in an article posted at Smithsonian.com, up to 1 trillion plastic bags are used globally each year and over 3 million tons of plastic are used to manufacture bottled water annually. Unfortunately, little of that plastic is recycled. In fact, so much plastic is thrown away yearly that it could circle the globe four times. While some of those bags, bottles and other debris end up in landfills, some of it ends up in streams and rivers, then is carried out into the oceans. All of this oceanic plastic pollution adversely affects the food chain.

Lantern Fish

• Myctophids, more commonly known as lantern fish, are food for many ocean species, including tuna and squid. They represent up to 60 percent of the ocean's "fish-mass" and are considered an integral component of the ocean's food chain. During a 2008 expedition, scientists from the 5 Gyres Institute dissected 600 lantern fish and found that one third contained plastic. When lantern fish mistakenly eat plastic, it makes them feel full so they do not eat real food. Plus, the toxic chemicals used to make the plastic stay inside their stomachs because it cannot leave or be digested. When the fish is eaten by mahi mahi, for example, that fish then consumes those chemicals and passes them along up the food chain.

Chemical Concentration

• The ocean food chain not only consumes the chemicals used to make the plastic but also chemicals from the surrounding water drawn to floating pieces of debris like a magnet. Richard Thompson, a marine scientist from the University of Plymouth, found that when plastic degrades in the ocean, chemicals, such as the banned pesticide DDT, in the water around the plastic become concentrated on the plastic's surface. When fish eat this plastic, they are ingesting all of those concentrated toxins. Thompson believes those chemicals will end up in the organism's tissues as the digestive system tries to break the plastic down. As a result, fish with higher concentrations of toxins will become part of the food chain.

Consumption and Death

• For some oceanic organisms, the toxins on the plastic are not as problematic as the plastic itself. According to a Voice of America article about the work of the 5 Gyre Institute, sea birds, turtles and fish die by the hundreds yearly from eating plastic. As with the lantern fish, most of these creatures assume the plastic is edible, then feel full so they do not eat real food, thus leading to malnutrition. Also, the plastic may cause physical damage to the organism as it is being consumed. The 5 Gyres Institute scientists estimate that more than 40 percent of marine mammals and 86 percent of sea turtles have plastic inside them. As plastic kills off valuable members of the oceanic food chain, organisms higher up that chain may find food sources in shorter supply.

Human Health

• Because humans consume fish and other marine life harvested from the oceans, they are also part of the oceanic food chain. The chemicals on the plastic eaten by the fish end up in their tissue, then enter our bodies when we consume those fish. These toxins, known as persistent organic pollutants, have been linked to a variety of health problems, including cancer, childhood developmental problems, immune system problems, diabetes and low birth weights. Anna Cummins, a co-founder of the 5 Gyres Institute, had a "body burden analysis" done to see which of these chemicals were in her body. The results showed traces of PCBs, DDT, PFCs and flame-retardant chemicals in her blood.