The remaining 20% of debris in the Great Pacific Garbage Patch comes from boaters, offshore oil rigs, and large cargo ships that dump or lose debris directly into the water. The majority of this debris—about 705,000 tons—is fishing nets. More unusual items, such as computer monitors and LEGOs, come from dropped shipping containers.

While many different types of trash enter the ocean, plastics (e.g. plastic bags, bottle caps, plastic water bottles, Styrofoam cups) make up the majority of marine debris for two reasons. First, plastic’s durability, low cost, and malleability mean that it’s being used in more and more consumer and industrial products. Second, plastic goods do not biodegrade but instead break down into smaller pieces. 

 

Seals and other marine mammals are especially at risk. They can get entangled in abandoned plastic fishing nets, which are being discarded more often because of their low cost. Seals and other mammals often drown in these forgotten nets—a phenomenon known as “ghost fishing.”

 

Marine debris can also disturb marine food webs in the North Pacific Subtropical Gyre. As microplastics and other trash collect on or near the surface of the ocean, they block sunlight from reaching plankton and algae below. Algae and plankton are the most common autotrophs, or producers, in the marine food web. Autotrophs are organisms that can produce their own nutrients from oxygen, carbon, and sunlight.

 

If algae and plankton communities are threatened, the entire food web may change. Animals that feed on algae and plankton, such as fish and turtles, will have less food. If populations of those animals decrease, there will be less food for apex predators such as tuna, sharks, and whales. Eventually, seafood becomes less available and more expensive for people.

 

These dangers are compounded by the fact that plastics both leach out and absorb harmful pollutants. As plastics break down through photodegradation, they leach out colorants and chemicals that have been linked to environmental and health problems. Conversely, plastics can also absorb pollutants from the seawater. These chemicals can then enter the food chain when consumed by marine life.

It may not be cost-effective to skim the surface of the entire ocean. Even a cleanup focusing on “garbage patches” would be a tremendous challenge. Keep in mind these points:

  -  Concentration areas move and change throughout the year

  - These areas are typically very large
  -  The marine debris is not distributed evenly within these areas
  -  Modes of transport and cleanup will likely require fuel of some sort

  -  Most of the marine debris found in these areas is small bits of plastic

This all adds up to a bigger challenge than even sifting beach sand to remove bits of marine debris. In some areas where marine debris concentrates, so does marine life. This makes simple skimming the debris risky—more harm than good may be caused. Remember that much of our ocean life is in the microscopic size range.

Analysis by an oceanographer and undergraduate physics student suggests that targeting the patch itself is not the most efficient way to clean up the oceans:
  -  The largest flow of plastics is actually off the coasts, where it enters the oceans.

  -  You can remove the plastics before they have had a chance to do any harm – plastics in the patch have travelled a long way and potentially already done a lot of harm.

1. The Western Garbage Patch, located near Japan

2. The Eastern Garbage Patch,  between Hawaii and California.

For many people, the idea of a “garbage patch” conjures up images of an island of trash floating on the ocean. However, microplastics can’t always be seen by the naked eye. Even satellite imagery doesn’t show a giant patch of garbage. The microplastics of the Great Pacific Garbage Patch can simply make the water look like a cloudy soup. This soup is intermixed with larger items, such as fishing gear and shoes. 

-  Work through questions on your worksheet
-  Choose one student from each group to negotiate with other parties
-  Present plan to class
Class to vote on best plan