MARINE DEBRIS - Marine Pollution: What Everyone Needs to Know - page 42

dumping in rivers and streams, and spillage of materials dur-
ing production or transportation. Commercial fishing is a
major source of lost nets and ropes. Derelict vessels sit on the
bottom of ports and waterways, creating a threat to naviga-
tion. Many sink at moorings, or remain partly submerged in
the intertidal zone or stranded on the shoreline. One unusual
source of a great deal of debris, large and small, was the 2011
earthquake and tsunami in Japan, which sent houses, docks,
cars, and everything they contained adrift in the Pacific Ocean.
What are the major constituents of debris?
Plastics, as mentioned before, comprise a large proportion of
the debris, and the variety and quantity of plastic items has
increased dramatically, including domestic material (shop-
ping bags, cups, bottles, bottle caps, food wrappers, balloons)
(Figure 3.1), industrial products, and lost or discarded fishing
gear. As these materials are commonly used, they are common
in marine debris. Derelict fishing gear includes nets, lines,
crab and shrimp pots, and other recreational or commercial
fishing equipment that has been lost, abandoned, or discarded
in the water. Modern gear is generally made of synthetic mate-
rials and metal, so lost gear can persist for a very long time.
Monofilament fishing line can persist for hundreds of years.
Glass, metal, and rubber are used for a wide range of products.
While they can be worn away—broken down into smaller and
smaller fragments—they generally do not biodegrade entirely.
Today, most of what we use comes packaged in plastic, which
can last for centuries. It is this stability and resistance to deg-
radation that causes it to be so problematic. A generation ago,
products were packaged in reusable or recyclable materials
like glass and paper. Today, we use products that we dispose
of at the end of their short life, and which end up in landfills,
on our beaches, and in the ocean as marine litter.
In addition to the visible litter on beaches, microscopic
plastic debris from many sources including the breakdown of