Some More Facts About Marine Debris

When looking at the career pages of the AWI (Alfred-Wegener-Institut, based in Bremerhaven, Germany), the requirements for getting a job with them seem to be quite challenging. PhDs, Science Officer, Master Students, and a doc for their Antarctic station. There is a good reason for that. They are experts and extremely good at what they are doing. One of the items they keep looking at is marine debris and its origin, distribution and impact.

The text below answers a couple of fundamental questions on marine debris. This is rather similar to a previous post here on Active Outside (basic Q&A on waste in oceans), yet it does give more details and background information on various topics. All of the below (plus lots more) can also be found on the website of AWI. Some of their answers I have shortened a bit. Also, the reason for including it here as full text instead of including a link is quite simple. I would like to keep the content, even if AWI decides to (re)move their page.

Their researchers and scientists are doing a more than fabulous job. Their realistic view on this matter is something I value highly (e.g. their comment on estimated numbers of marine debris floating on the surface of the oceans).

I hope the lines below will increase your understanding of marine debris and the dangers coming with it. There is a whole lot more literature available for this topic, and I am sure the more you read the more worrying the entire complexity of it all will get for you. Do not use plastic wherever you can, that’s the easiest way to help.

Ok, here we go, the text below is (more or less) the one available on the AWI-homepage. No pictures of marine debris this time. But I am sure you will nonetheless enjoy this “no-pics” read.

Which types of plastic litter are there in the ocean?

Practically every type of plastic material and plastic object we use today can be found there. Cigarette filters, shopping bags, plastic bottles, etc. Packaging makes up the majority of the litter. The most noticeable type are the patches that are so dense they cover the surface of the water, making them highly visible – like sheets and bags made of polyethylene.

Yet they, too, can eventually sink to the ocean floor when organisms settle on them. Though higher-density plastics like PVC, polyester and polyamide sink immediately, a great deal of plastic litter initially floats on the surface. The longer these plastics spend in the water, the more they are subjected to ultraviolet radiation from sunlight, and to the salt in the seawater. Battered into smaller and smaller pieces by the waves, the resulting fragments eventually reak down into tiny particles ranging from only a few micrometres to one millimetre in size – which explains why they’ve been dubbed microplastics.

Where does the plastic waste come from?

Global plastic production has increased several-fold over the past few decades, rising by 620 per cent between 1970 and 2013, and the amount of marine debris has experienced similar growth. Many sources estimate that roughly 80 per cent of marine plastic litter originates on land. But according to a recent Australian study, how much litter from the world’s various coastal regions finds its way to the oceans primarily depends on how advanced the different countries’ waste collection and recycling systems are.

Waste recycling is particularly poor in China and Southeast Asia, where a tremendous amount of plastic litter ends up in the ocean. If waste recycling isn’t significantly improved, thanks to increasing production the amount of litter worldwide will continue to rise until at least the year 2100.

In contrast, the amount of plastic waste dumped into the sea by ships will most likely have decreased: for decades now, the International Convention for the Prevention of Pollution from Ships (MARPOL) has outlawed dumping plastic waste. But of course, some waste still finds its way off board, whether intentionally or not.

How much plastic litter is there in the ocean?

It’s extremely difficult to gauge the total amount of plastic waste in our oceans. There have been a number of scientific studies seeking to estimate the volume or total weight of the plastics by measuring the amount in a given area and extrapolating for the whole. But these estimates involve a number of uncertainties, firstly because the researchers only collect random samples and can only project the total amount.

Secondly, it’s extremely difficult to estimate the total amount because the litter stems from various sources, not all of which can be measured in detail. It is blown out to sea from landfills and sewage treatment plants; it is washed out into coastal waters from canals and rivers, or dumped directly into the ocean. All this is supplemented by waste from ships and fishing nets. In order to estimate the total amount, the microplastics, plastics floating on the surface and those that sink to the ocean floor would all need to be taken into account. Not only is such a task difficult from a technical perspective, the lack of international standards means that different countries’ figures on litter production often cannot be compared.

Accordingly, a team of researchers recently chose to pursue a different approach, using production data to calculate how much litter is produced worldwide. Their conclusion: every year, between 4.8 and 12.7 million tons of the plastic waste produced on land eventually reach the ocean.

Where does plastic litter end up?

Researchers have determined that the amount of plastic litter floating on the ocean’s surface is considerably smaller than the total amount of marine anthropogenic plastic. Based on litter surveys in 680 regions, a recent study estimates that roughly 269,000 tonnes of plastic litter are floating on the surface, only a fraction of the amount mentioned in Answer 3 above.

Today, we still cannot explain the discrepancy with certainty; most likely, it is due to a number of factors. The authors of the study believe a major portion of the litter breaks down into microparticles, which gradually sink. It’s also conceivable that animals like e.g. zooplankton (krill or fish larvae) unwittingly ingest the microparticles when they feed, removing them from the surface. Some plastics are most likely frozen in the sea ice of the Arctic and Antarctic. Working together with partners from other European marine research organisations, an AWI expert has determined that, given time, larger pieces of litter also sink to the bottom – even plastic bags.

Above all, plastics tend to accumulate in the deep-sea trenches, the deepest points on the ocean floor. Most likely, tides are responsible for transporting the plastic so far down. Plastic litter has even been found in remote regions like the Arctic. To date we still don’t know just how much litter there is in the water column worldwide, as it’s impossible to completely comb through such a gargantuan volume of water.

What are garbage patches?

Many of the pieces of plastic suspended in the water eventually drift out to the open sea. Sooner or later, most of them are caught by the great rotating ocean currents, also known as gyres. Once swept up, the plastic moves deeper and deeper into the gyre, as a result of which the litter becomes concentrated at the centre. Because of this effect, over the past years the amount of litter at the centres of the gyres has grown so rapidly that these areas are now also referred to as garbage patches.

However, contrary to what many images in the media would seem to suggest, the litter is not densely packed; the first thing you see when you look at a garbage patch is mostly water. According to scientific surveys, even in the centre of a gyre, “only” between 50 and 60 pieces of plastic drift in an area of one square kilometre; most of it is small pieces of debris ranging from one to two centimetres in length.

At first blush, that may not seem like that much garbage, but compared to the North Sea, the effect of the concentration in the garbage patches becomes clear: although the North Sea is much closer to land (and therefore to the sources of pollution), on average it is home to only 30 to 35 pieces of plastic per square kilometre – only half as many as in the garbage patches, which are several thousands of kilometres from land.

How large are the garbage patches?

Today we know of five major ocean gyres, and plastic litter has condensed to form garbage patches in each. Located in the Atlantic, the Indian Ocean and the Pacific, the largest is the North Pacific Gyre, which stretches from the Equator to roughly the 50th parallel – where e.g. the Russian island Sakhalin can be found. However, the garbage patch only includes the area at the core of the gyre, where the plastic litter can become extremely dense.

It’s difficult to say just where a garbage patch begins, or exactly how much area it covers; to estimate this, the concentration of litter in the water would need to be measured at many different sites. Yet even these measurements are uncertain, since the ocean is in constant motion: currents and winds can make the plastic drift apart or drive them together. Today we can safely say that the garbage patches have an average diameter of several hundreds of kilometres. In the opinion of the AWI experts, it’s ultimately irrelevant how large the respective patches are.

The fact is, the litter collects in these patches, which means these ocean regions are hardest hit by plastic pollution. Computer simulations of ocean currents indicate that the gyres are interconnected by smaller currents, which eventually transport a great deal of the litter to the North Pacific Gyre – which is why so much litter gathers there. The simulations also show that there may be a sixth, smaller garbage patch in the Barents Sea to the northeast of Norway. However, this thesis still has to be confirmed by research on site.

Where do microplastics come from?

Microplastics include a wide range of plastics that find their way to the sea. A substantial portion – just how much is still unclear – is created directly in the ocean, when larger pieces of plastic slowly break down. Large amounts of microparticles are also produced directly in the course of plastic manufacturing; what’s more, microparticles can even be released when we wear, wash and dry synthetic textiles like microfleece or other sportswear.

In many cases, this involves minute microfibres that are first suspended in the air, before being carried out to sea by the wind. Washing a single load of laundry with these textiles can release roughly 2,000 fibres, which most wastewater treatment plants can only partially filter out. A study conducted in Norway recently concluded that in developed countries, microparticles can also be produced by wear on car tyres; rain washes them into sewer canals, streams, rivers and ultimately out to sea.

The paint used on ships, which releases small particles of additives like bonding agents and alkyd resins, represents a further source of microparticles. These additives are released as the paint becomes more weathered or is worn off. According to the latest estimates, the percentage of plastic particles from cosmetics (e.g. peelings) is comparatively low – but could also be avoided.

What are the risks of marine debris?

Given how diverse marine debris is, it can also have a variety of effects on marine life. Larger pieces of plastic can become deadly traps – as can be seen in the six-pack rings that can strangle seabirds, or old fishing nets, which sea turtles can get tangled in and ultimately drown. Experts are currently discussing whether marine debris still “only” kills individual animals, or if it might even endanger entire populations.

A recent study shows that today 90 per cent of all seabirds swallow plastic parts; different species are at different levels of risk, depending on their feeding habits. The situation is especially critical for northern fulmars, which spend their entire lives on the open sea and exclusively feed from the water’s surface. Experiments on dead animals have revealed that in some cases, their stomachs are completely full of plastic; many of them must have simply starved to death. As such, it’s highly plausible that plastic litter could decimate fulmar populations in the years to come. What remains unclear is how microplastic particles affect marine animals and ultimately human beings.

Laboratory experiments have shown that different species vary in terms of their vulnerability to the particles. If bivalves are subjected to high concentrations, the particles are transported from the digestive tract into the animals’ cells and tissues, where they can cause inflammations. In contrast, marine isopods appear to have mechanisms in their digestive tracts that prevent microparticles from spreading to other parts of their bodies. And we still have no idea whatsoever whether or not microparticles unwittingly consumed together with seafood pose a threat to human health.

What are the economic impacts of marine debris?

In many sectors, the plastic litter in our oceans is already producing additional costs and cutting into profits. Tourism is a good example. Since litter-covered beaches scare off tourists, beach communities have to clean them on a regular basis, in most cases shouldering the costs of plastic collection and disposal themselves. Depending on the region and the level of pollution, plastic litter can also pose problems for fishers. If too much litter clogs their nets, it reduces their catches. It also costs them time to remove the litter from their nets.

Further, litter like old fishing nets can get caught in propellers of ships, which can cause serious damage and even disable the ships.  When that happens, the Coast Guard or some other agency has to come to the rescue, producing additional costs. Another aspect to bear in mind: with all of the litter that ends up in our oceans, valuable raw materials on the order of millions of tonnes are lost to the global recovered substance cycle.

And plastic is almost exclusively manufactured on the basis of petroleum. If a research team’s estimates are any indication, as much as 12.7 million tonnes of plastic end up as marine debris every year, a tremendous amount that can neither be recycled nor used as fuel in power plants.

How can we prevent the spread of marine debris?

Significantly reducing the amount of marine debris will require fundamental changes. One way would be to use more plastics that are completely biodegradable. Though we already have compostable plastic, when it breaks down it often leaves behind microparticles or fibres. Another solution would involve making a radical change in our consumer behaviour.

Global plastic production is currently growing by approximately 4 per cent every year, a trend that can only be reversed if, for example, industry reduces the amount of packaging materials it uses, and consumers consciously reduce their demand for plastics. Further, researchers at the AWI consider environmental education to be particularly important – it’s essential to make children and young people aware of the risks posed by plastic debris, and of alternatives to plastic, so as to achieve a long-term change in purchasing behaviour. In this regard, international litter collection campaigns are promising: though collecting litter on coasts and along rivers removes comparatively little waste from the environment, the educational value of these campaigns is very high.

Another good example is the “Fishing for Litter” campaign, in which fishers from several European countries have committed to dispose of the plastic litter they catch in their nets on land, instead of simply throwing it back into the sea.

To finish it all up

That was it. I honestly do hope all of this information will be of great use and value for you. If you have some top of the range sources and more information on marine debris, plastic pollution, litter in oceans, etc., then feel free to send me some lines or post here as a comment. Thank You!

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