The media attention given to turtles that die from eating plastic bags and photographs of marine animals entangled in plastic netting has highlighted the worldwide problem of marine debris: human-created waste that ends up in the sea. Carol Brammage looks at how bad this problem has become.

It is estimated that between 60% and 80% of marine debris is plastic material. Some of this debris comes from ocean-based sources such as ships. Most of it comes from land-based sources in the form of trash that is washed or blown into the sea.. The many sources of plastic waste include debris from industries, agriculture, commercial enterprises, public institutions and transport spillages. Familiar items such as plastic carrier bags, fast-food packaging and disposable items from plastic cutlery to cigarette lighters all contribute to the endless waste.

Rubbish gets washed up on shorelines, sometimes in overwhelming concentrations and even on remote islands, and can be harmful to beachcombing animals and birds. Floating plastic debris when ingested by marine animals and birds can block their digestive tracts resulting in death by choking or starvation. Derelict fishing gear and other floating debris all too often drown, strangle or injure marine creatures that become entangled in them.

Plastics have been accumulating in our environment since the 1950s when the mass production of plastics began. According to the American federal agency NOAA (National Oceanic and Atmospheric Administration), most commonly used plastics never really “go away”, they just break down into ever smaller fragments.

In an article on plastic debris published in Philosophical Transactions of the Royal Society. Biological Sciences in 2009, marine ecologist Richard Thompson and fellow authors Barnes, Galgani and Barlaz commented on the durability of plastics:

“The longevity of plastics is a matter for some debate, and estimates range from hundreds to thousands of years. It is considered that (with the exception of materials that have been incinerated) all of the conventional plastic that has ever been introduced into the environment still remains to date unmineralised either as whole items or as fragments.”

In addition to post-consumer waste, significant amounts of preproduction pellets used in making plastic, and even plastic spherules used in cosmetics such as facial scrubs, end up in the ocean. Larger plastic marine debris items fragment over time as a result of UV exposure and physical abrasion, adding to the volume of microplastics in the sea.

Microplastics, commonly defined as being particles less that 5 millimetres in diameter, are becoming an increasing focus of research. NOAA reports that there is evidence that persistent organic pollutants (POPS) bind to plastic debris in the oceans and that “the uptake potential of organic contaminants from the marine environment to plastic debris” is receiving increasing scientific attention. Plastics in the ocean can transport not only “invader” species but also contaminants, and they have the potential to adsorb (attract and hold to surface) organic contaminants in the marine environment. According to the NOAA, it is possible “that plastics could also desorb these contaminants to biota that ingest plastics”.

Plastic debris attracts and accumulates some organic toxins to concentrations thousands of times higher than ambient seawater. Marine specialists agree that microplastics warrant further scientific scrutiny.

Although the global scale and distribution is not yet accurately mapped or quantified, it is known that microplastics are widely – though not uniformly – distributed. There are vast areas of ocean where floating plastics concentrate as a result of spiraling patterns in ocean currents that are known as gyres. Dubbed “garbage patches”, there are five major ocean gyres: the North Atlantic, South Atlantic, North Pacific, South Pacific, and Indian Ocean gyres.

According to to NOAA’s marine debris website, the name “garbage patch” has led to the belief that such an 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.”  However, this is not an accurate representation. Although litter and larger debris, such as derelict fishing nets are found in these areas, much of the concentrated waste is small floatable bits of plastic that are not immediately visible.

The North Pacific Gyre, says NOAA, “is the one most notable because of its tendency to collect debris”. Being a fluid system it is difficult to measure it exactly but it “is roughly estimated to be approximately 7 to 9 million square miles”.

Research projects that collect and analyse samples from the region in order to obtain accurate information include two recent expeditions investigating how much plastic is accumulating, how it is distributed, and how it is affecting ocean life.

In an August 2009 expedition, researchers from the Scripps Institution of Oceanography collected samples in the North Pacific Gyre. As reported on the Scripps Environmental Accumulation of Plastic Expedition (SEAPLEX) website, first results published in June 2011, reveal that more than 9% of “mid-water fishes contained plastic debris, primarily broken-down bits smaller than a human fingernail”.

As discussed on the Seaxplex website by researcher Chelsea Rochman, as smaller organisms ingest contaminated plastics, potentially these contaminants may bioaccumulate in their body tissues. A concern requiring further research is that as these organisms in turn are eaten by animals higher up the food chain – culminating in humans eating tuna for instance – concentrations of contaminants are magnified in a process known as biomagnification.

Also investigating the distribution and impact of marine plastics, the Algalita Marine Research Foundation’s latest expedition took place in July 2011. Although too early for formal research results, Algalita expedition members share their first-hand observations and experiences on their blog.

It is not only marine ecologists and activists who are concerned about plastic pollution. There are many who hope that we can change our wasteful ways. In line with this hope, Karen Ristuben, an artist, environmental advocate and member of the Algalita expedition, concludes her blog entry with a list:

“Ten things you can do:
1. Stay informed about our plastic world and environmental toxins.
2. Reduce your use of one-time, single use plastics.
3. Conduct your own personal trash audit.
4. Creatively reuse and repurpose your plastic products.
5. Refuse to use plastic shopping bags and don’t buy bottled water.
6. Support legislation that increases producer responsibility.
7. Support and try to improve local recycling efforts.
8. Pick a place and pick up the trash there every day.
9. Educate children about responsible use of plastic so they can teach their parents.
10. LIVE MORE SIMPLY.”

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About the author

EthicalLiving.com.au