About Ocean Plastic

Plastic breaks into smaller pieces but it's still there
Plastic breaks into smaller pieces but it’s still there

What happens to garbage when it washes out to sea?

Organic garbage, or garbage that used to be living, like wood, paper and food scraps, is biodegraded. This means that it is broken down by microorganisms like bacteria into compounds that can be used by other organisms. Plastic is different. It is a relatively new, man-made product, and microorganisms have not evolved to eat plastic and turn it into the building blocks of new life. Sunlight causes big pieces of plastic to fragment into lots of little pieces of plastic, but it is still plastic. In the ocean, organic garbage disappears, but plastic remains for a very long time.

Broken bits of plastic as seen from the side of the ship
Broken bits of plastic as seen from the side of the ship

What does the “Garbage Patch” look like?

Here is a picture of the Sailing School Vessel Robert C. Seamans in the North Pacific subtropical gyre, an area sometimes referred to as the “Garbage Patch.” The white specs in the water, barely visible next to the ship, are tiny fragments of plastic. These little plastic pieces may have started out as milk jugs, bottle caps or plastic forks, but now it is impossible to tell what they were. In this photo, plastic has aggregated into a long line. Usually the tiny plastic pieces are spread out over a much larger area, and the plastic is not visible from the ship’s deck. 

Neuston Net
Neuston Net

 How do scientists collect plastic in the ocean?

Floating plastic is collected at the air-sea interface (the “neuston layer”) with a fine-meshed plankton net that is towed alongside the ship. The contents of the net are examined and each tiny plastic fragment is removed with tweezers and counted. 

Zooplankton and plastic
Zooplankton and plastic

 Why can’t all this plastic be removed with nets?

There are a couple reasons why this will not work…

  1. The ocean is way too large.
  2. We would also be catching and removing a lot of plankton, small plants and animals, that all the other animals in the sea depend on for food. No plankton means no tuna fish sandwiches.

Is the middle of the ocean full of water bottles?

No. Plastic can be divided into floaters and sinkers. Water bottles are made of PET (recycling code #1, polyethylene terephthalate) which sinks because it is denser than sea water. Water bottles sink to the bottom near shore unless their caps are on and they hold air. Eventually plastic bottles break apart, and then they sink. Below are the types of plastic that float. These are they plastics that travel the ocean’s surface.

Floating Plastic

#2 HDPE (high density polyethylene) – milk jugs, detergent bottles, grocery bags

#4 LDPE (low density polyethylene) – garbage and sandwich bags, plastic wrap, 6-pack holders

#5 PP (polypropylene) – yogurt and margarine tubs, screw on caps, lids, straws, plastic forks, rope

#6 PS (polystyrene) – floats when expanded into egg cartons, packing pellets, take-out containers, styrofoam cups

Here is a list of plastics that sink. They cause problems in near shore sediments.

Sinking Plastic

#1 PET (polyethylene terephthalate) – bottles for water, soda and juice, some take-out and produce containers

#3 Vinyl (polyvinyl chloride) – plastic pipes, fencing, shower curtains

#6 PS (polystyrene) sinks when it is not expanded, plastic cups, some plastic utensils

The last category of plastic is #7, everything else. Some of it floats, some sinks. This plastic is difficult to recycle because it is composed of a variety of different materials.

Plastic breaks into smaller pieces but it's still there
Plastic breaks into smaller pieces but it’s still there

Why does the plastic I’ve picked up on the beach look old and weathered?

Because it is. Plastic becomes faded and brittle when it is exposed to the sun. It may have been floating out at sea for awhile before it washed up. But you picked it up and threw it in the garbage – good job! You have made the beach a nicer place and prevented that plastic from ending up in the ocean again.

Ocean gyres
Ocean gyres

 What is a gyre and why are they full of plastic?

Gyres are large, circular ocean currents created by wind and the earth’s rotation. There are gyres in the North Atlantic, South Atlantic, North Pacific, South Pacific and Indian Oceans. These surface currents carry floating materials, like plastic, into their center. They form an oceanographic “dead-end,” where plastic accumulates and cannot easily escape. Natural debris breaks down but plastic debris fragments into smaller and smaller pieces.

Are there laws against dumping trash at sea?

There are now. But before the 1972 London Convention, a United Nations agreement to control ocean dumping, the oceans were used a handy place to get rid of waste. Ocean dumping laws became more restrictive with MARPOL (as in marine pollution) in 1988 and the London Protocol of 1996.  

Why is plastic in the ocean a problem? 

Marine animals can get tangled up in plastic. Many animals from tiny zooplankton to seabirds, fish and sea turtles eat plastic. In some cases this causes death, in others it doesn’t. Toxins adhere to plastic and can be transferred to animals when eaten. Plastic floating in the ocean transports plants and animals to other parts of the globe where they can become invasive. We do know that an enormous amount of plastic is accumulating in the ocean, but there is still much to learn about the effects of this plastic on the environment. Right now scientists have many more questions than answers.

Where is the plastic washing up on our beaches coming from?

Some plastic comes from ships at sea, but most of it is land based. It washes in from the shore, it is swept down rivers and it blows into the ocean from land. Much of the plastic in the ocean comes from less developed countries that don’t have garbage collection, recycling or adequate landfills. These countries have plenty of plastic coming in, but without good ways to manage waste, much of it eventually washes out to sea. This plastic may float into an ocean gyre and stay awhile, or it may wash up on a beach.