large amounts of plastic debris enter the ocean, where it slowly fragments
and accumulates in convergence zones. Scientists are concerned about the
possible impacts of small plastic fragments—microplastics—in the
environment. The role of plastics as a vector for transporting chemicals
and species in the ocean is as yet poorly understood, but it is a
potential threat to ecosystems and human health. Improved waste management
is the key to preventing plastic and other types of litter from entering
has become a global repository for much of the waste we generate. Marine
debris includes timber, glass, metal and plastic from many different
sources. Recently, the accumulation and possible impacts of microplastic
particles in the ocean have been recognized as an emerging environmental
issue. Some scientists are increasingly concerned about the potential
impact of releases of persistent bio-accumulating and toxic compounds (PBTs)
from plastic debris. At the same time, the fishing and tourism industries
in many parts of the world are affected economically by plastic entering
nets, fouling propellers and other equipment, and washing up on beaches.
Despite international efforts to stem the flow of plastic debris, it
continues to accumulate and impact the marine environment. To reduce the
quantity of plastic entering the ocean, existing management instruments
need to be made more effective and all aspects of waste treatment and
disposal need to be improved.
Several common types of
plastic are buoyant and have been transported by ocean currents to the
remotest regions of the planet, including the Arctic and Antarctic . Media
attention has focused on reports of the relatively high incidence of
plastic debris in areas of the ocean referred to as ‘convergence zones’
or ‘ocean gyres’. This has given rise to the widespread use of terms
like ’plastic soup’, ‘garbage patch’ and ‘ocean landfill’.
Such terms are rather misleading in that much of the plastic debris in the
ocean consists of fragments that are very small in size while the areas
where they are floating are not, for example, distinguishable on satellite
images. Nevertheless, publicity resulting from media reports and from the
activities of several NGOs has helped to raise public and political
awareness of the global scale of the plastic debris problem, together with
the larger issue of marine litter.
What are the
The “garbage patch,” as
referred to in the media, is an area of marine debris concentration in the
North Pacific Ocean. The name “garbage patch” has led many to believe
that this area is a large and continuous patch of easily visible marine
debris items such as bottles and other litter—akin to a literal blanket
of trash that should be visible with satellite or aerial photographs. This
is simply not true. While litter items can be found in this area, along
with other debris such as derelict fishing nets, much of the debris
mentioned in the media these days refers to small bits of floatable
plastic debris. These plastic pieces are quite small and not immediately
evident to the naked eye.
Where are the
garbage patch - Concentrations of marine debris have been noted
in an area midway between Hawai‘i and California within the North
Pacific Subtropical High, an area between Hawaii and California. Due to
limited marine debris samples collected in the Pacific it is still
difficult to predict its exact content, size, and location. However,
marine debris has been quantified in higher concentrations in the calm
center of this high-pressure zone compared to areas outside this zone. It
should be noted that the North Pacific Subtropical High is not a
stationary area, but one that moves and changes. This area is defined by
the NOAA National Weather Service as "a semi-permanent, subtropical
area of high pressure in the North Pacific Ocean. It is strongest in the
Northern Hemispheric summer and is displaced towards the equator during
the winter when the Aleutian Low becomes more dominant. Comparable systems
are the Azores High and the Bermuda High." The High is not a
stationary area, but one that rotates, moves, and changes.
garbage patch - There is a small "recirculation gyre"
south of the Kuroshio current, off the coast of Japan that may concentrate
floating marine debris; the so-called western garbage patch. The exact
forces that cause this clockwise rotation are still being researched;
however it may be caused by winds and ocean eddies (clockwise or
counter-clockwise rotating waters). Research is ongoing by academia such
as the University of Hawaii and Massachusetts Institute of Technology, to
further understand the true nature of and forces behind these
Are the Pacific
“garbage patches” the only areas where marine debris concentrates?
The “patches” are not
the only open ocean areas where marine debris is concentrated. Another
important area is the North Pacific is the Subtropical Convergence Zone (STCZ).
This area, located north of the Hawaiian archipelago, has a high abundance
of marine life, is a known area of marine debris concentration, and is one
of the mechanisms for accumulation of debris in the Hawaiian Islands (Pichel
et al., 2007).
similar to the North Pacific Subtropical High and STCZ exist in other
oceans of the world. Little research to date has been conducted on marine
debris in these areas. Because of this no one can say for sure how large
these areas are, especially since they move and change, sometimes daily,
and no accurate estimate exists of how much debris is out there.
What is plastic marine
The word “plastic” is
used to describe a collection of artificial or manmade chemical compounds
that come in about as many shapes, sizes, and colors as you can imagine!
For example, foam carry-out containers (made of polystyrene) and bottle
caps (made of polypropylene) are items that would be considered plastic
marine debris if found in our oceans or waterways.
it’s actually a plastic!)
Why is plastic marine
debris so common?
Plastics are used in many
aspects of daily life and are a big part of our waste stream. Many
plastics are colorful and will float in water, which makes plastic debris
a very visible part of the marine debris problem. However, an accurate
estimate does not yet exist for how much debris is composed of plastic
Can plastic marine debris
Plastic has the potential
to harm fish and other wildlife in two main ways.
Direct Impacts -
Studies have shown that fish and other marine life do eat plastic.
Plastics could cause irritation or damage to the digestive system. If
plastics are kept in the gut instead of passing through, the fish could
feel full (of plastic not food) and this could lead to malnutrition or
- Plastic debris accumulates pollutants such as PCBs (polychlorinated
biphenyls) up to 100,000 to 1,000,000 times the levels found in seawater.
PCBs, which were mainly used as coolant fluids, were banned in the U.S. in
1979 and internationally in 2001. It is still unclear whether these
pollutants can seep from plastic debris into the organisms that happen to
eat the debris and very difficult to determine the exact source of these
pollutants as they can come from sources other than plastic debris. More
research is needed to help better understand these areas.
degradability in the ocean
The degradation time
for plastic in the marine environment is, for the most part, unknown. Estimates
are in the region of hundreds of years. Most types of plastic cannot be
considered biodegradable in this environment, as the term ‘biodegradable’
would only apply to those that are broken down by bacterial action or oxidation
into simpler molecules such as methane, carbon dioxide and water (Narayan 2009).
‘Biodegradable’ or ‘oxy-degradable’ plastics may be broken down in
industrial composters, or in landfill, in a controlled environment with a
temperature consistently above 58ºC (Song et al. 2009). The temperature in most
oceans is far below that, and the degradation process is therefore much slower.
Plastic in the ocean tends to fragment into smaller particles of similar
composition, a process aided by the action of waves and wind. UV radiation in
sunlight plays an important role in breaking down certain plastics (PP, PE).
When plastic is manufactured, a UV stabilizing agent is sometimes added to
extend the ‘life’ of certain items, also making it harder for them to break
down after disposal. Seawater absorbs and scatters UV, so that plastics floating
at or near the surface will break down more rapidly than those at depth. When
plastic objects sink to the seabed, the breakdown process is slowed
significantly since there is virtually no UV penetration and temperatures are
much colder. Plastic debris has been observed on the ocean floor from the depths
of the Fram Strait in the North Atlantic to deepwater canyons off the
Mediterranean coast, and much of the plastic that has entered the North Sea is
thought to reside on the seabed (Galgani et al. 1996, Galgani et al. 2000,
Galgani and Lecornu 2004).
The surface of most plastic objects is subject to fouling in the sea due to the
growth of bacteria, algae, barnacles, shellfish and other organisms. This
process spans the entire size spectrum of debris, from microplastics to large
single items such as buoys. A biological surface layer may affect breakdown
mechanisms. Fouling may also increase the density of plastic objects, causing
them to sink, with particles being redistributed throughout the whole water
column and some eventually sinking to the ocean floor. Later removal of the
biological surface layer by grazing organisms may cause the objects to float
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