Otras modalidades de juego
Nota 4: Con el propósito de prevenir el juego lento, el Comité puede, en las condiciones de la competencia (Regla 33-1), establecer
Although every garbage patch is a mystery, the scientific community consensually advocates that these patches are almost entirely made up of microplastics – the tiny bits of plastic that are not always visible to the naked eye and much less visible from space. The patches are not real compact islands of plastic waste. In truth, patches are like confetti or a thin soup of tiny particles (thickest in the middle of the gyres), which partially justifies the difficulty in
362 See ibid 1 and check table 1 on page 3.
363 See Melanie Bergmann and Michael Klages, ‘Increase of Litter at the Arctic Deep-sea Observatory
measuring the size of the so-called patches and, at the same time, the total amount of units, weight and volume of plastic particles existent on the sea.
It is thus highly improbable to disclose with accuracy the real figures, and there are several reasons. Gyres, and therefore patches, are vast, remote and are always shifting with weather conditions, currents and other physical processes within the oceans. The two most famous patches are relatively well documented, but little is known about plastic accumulation in other gyres, and even less about the vast majority of the sea surface outside the gyres (that remains unsurveyed).
One of the most detailed analysis of the distribution of plastic among the five major ocean repositories dates back to 2014. It took into account 24 expeditions across all five sub- tropical gyres occurred between 2007 and 2013, and estimated that the gyre in the North Pacific represented nearly one-third (containing 37.9% and 35.8% by particle count and mass, respectively) of the plastic pollution in all oceans, counting two trillion pieces. With 1.3 trillion pieces, the Indian Ocean had the second-largest volume of plastic. The North Pacific and the Indian Ocean contained thus 56% of all particles. The third was the North Atlantic, with 930 billion pieces, the fourth was the South Pacific, with 491 billion pieces and the fifth was the South Atlantic, with 297 billion pieces.364
Beyond question, accumulation rates vary widely in accordance with many challenging factors. The nature of the gyres itself makes it hard to measure accurately. In the open sea, bodies of water are bounded by atmospheric pressure systems and by the currents those systems create. In other words, air defines the body of water. When air pressure systems move, the body of water moves as well.365 Floating debris is constantly moving, shifting with
seasonal weather, and consequently its shape, size and density are also changing. In sum, one trawl may pick up next to nothing, because it missed the most concentrated spots, while the following one can be full of plastic debris.
Adverse meteorological conditions are also a constraint. It has been demonstrated that the trawls carried out during strong winds tend to capture fewer floating microplastics than during calm conditions. Due to wind-driven mixing, plastic debris is vertically distributed within the upper water column, becoming out of reach of surface-trawling nets.366 It is
364 Marcus Eriksen and others, ‘Plastic Pollution in the World’s Oceans..., 8. 365 Charles Moore, ‘Trashed’...
366 Surface net tows cannot account for the total amount of plastic pieces in the upper ocean mixed layer, except in
low wind conditions (u10 < 5 m/s), see Tobias Kukulka and others, ‘The Effect of Wind Mixing on the Vertical
possible, though, to combine surface and subsurface observations with one-dimensional column model, in order to estimate the total amount of plastic in the wind-mixed surface layer. Improved estimates of plastic concentration in the subtropical North Atlantic predicted an average integrated concentration 2.5 times the measured surface value, with a maximum of 27 times the surface value.367 Concluding, surface tow measurements significantly underestimate the total plastic content even for moderate wind conditions, which requires a reinterpretation of the existing marine plastic debris data sets.
Not all trash floats on the surface, but it is not always the wind’s fault. Plastic is a collective term for a variety of synthetic polymers with variable material properties, including density. This means that some consumer plastics, such as PET, PVC and PS are denser than seawater and sink, centimetres or several meters.368 Density analysis of plastic samples collected at the sea surface revealed that 99% were less dense than seawater.369
Additionally, plastics gradually lose buoyancy in seawater due to biofilm formation. Under the weight of fouling by a wide variety of bacteria, algae, animals and accumulated sediment, plastics can sink to the seabed.370
The last factor influencing the imprecision of the measures is the lack of standardised methodology used for the identification and quantification of microplastics in the marine environment. Small differences in the models can definitely contribute to different estimates, and, in fact, only standardised sampling procedures – already proposed by the Marine Strategy Framework Directive – will allow the spatiotemporal comparison (and monitoring) of microplastic abundance across marine environments.371
Although the scientific community recognises all the factors above described, they are not sufficient, not in any way, to answer to a very recently placed question.
367 ibid.
368 Erik van Sebille, ‘How Much Plastic is There in the Ocean?’ (World Economic Forum, 12 January 2016)
<www.weforum.org/agenda/2016/01/how-much-plastic-is-there-in-the-ocean/> accessed 31 July 2017 and Alexander G J Driedger and others, ‘Plastic Debris in the Laurentian Great Lakes: A Review’ (2015) 41(1) Journal of Great Lakes Research 10.
369 Kara Lavender Law and others, ‘Plastic Accumulation in the North Atlantic Subtropical Gyre’..., 1187. 370 Elemental analysis of plastic samples revealed the presence of nitrogen, which is absent in virgin polyethylene
and polypropylene and is thus indicative of bioaccumulation. See Kara Lavender Law and others, ‘Plastic Accumulation in the North Atlantic Subtropical Gyre’..., 1187. Biofouling occurs more quickly in soft and thin plastic fragments, but neither the magnitude nor the speed of this process across different types of small fragments has been reported. See Julia Reisser and others, ‘Marine Plastic Pollution in Waters around Australia: Characteristics, Concentrations, and Pathways’ (2013) 8(11) Plos One 7.
The first map ever of marine litter, prepared by the marine ecologist Andrés Cózar and a team of researchers, showed a worldwide distribution of plastic on the surface of the open sea, mostly accumulating in the convergence zones of each of the five subtropical gyres, with a comparable density. The most important was the revelation of an important gap in the size distribution of floating plastic debris as well as the finding that the global surface load of plastic in the ocean was well below, on the order of tens of thousands of tons, of what was expected compared with production and ocean leakage rates (already exposed above).372 These observations, published in 2014, on the size distribution of floating plastic debris point to important size-selective sinks, removing millimetre-sized fragments of floating plastics on a large scale. Besides the lack of observed increasing temporal trends in surface plastic concentration,373 these new findings provide strong support to the hypothesis of substantial losses of plastic from the ocean surface.
Four main possibilities have been thus proposed: shore deposition, fragmentation, sedimentation/biofouling and ingestion.374 Although a rigorous attribution of losses to each of these mechanisms is not yet possible, ‘resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean’,375 and to work on solving the problem.
As mentioned above, the 15 to 51 trillion particles of plastic debris on the open sea, weighing between 93 and 236 thousand metric tons, only correspond to 1% of global plastic waste estimated to enter the sea in the year 2010.376 It was also estimated that: about 15% of marine debris floats on the sea surface; another 15% remains in the water column; and 70%
372 Andrés Cózar and others, ‘Plastic Debris in the Open Ocean’..., 10241.
373 Richard Thompson published in 2004 the first assessment of microplastic abundance over time. He found that
while the amount of microplastics measured between the British Isles and Iceland increased from the 1960s and 1970s to the 1980s and 1990s, no significant increase was observed between the later decades. See Richard Thompson and others, ‘Lost at Sea..., 838. Similarly, the 22-year-study on the North Pacific, organised by the Sea Education Association and published in 2010, found no significant increase in annual mean concentrations of floating microplastics in the western North Atlantic subtropical gyre between 1986 and 2008, nor in the eastern North Pacific subtropical gyre between 2001 and 2012.See Kara Lavender Law and others, ‘Plastic Accumulation in the North Atlantic Subtropical Gyre’..., 1185-6. Another previous analysis focusing the missing plastic can be found in Kara Lavender Law and others, ‘Distribution of Surface Plastic Debris in the Eastern Pacific Ocean from an 11-Year Data Set’ (2014) 48(9) EST 4732-8.
374 Biofouling and ingestion are interconnected. Recent laboratory studies have demonstrated that microplastics are
readily consumed by copepods and that these microplastics are later egested along with waste organic matter in faecal pellets. Sinking faecal matter represents thus a mechanism by which floating plastics can be vertically transported away from surface waters. See Mathew Cole and others, ‘Microplastics Alter the Properties and Sinking Rates of Zooplankton Faecal Pellets’ (2016) 50 EST 3239-40.
375 Andrés Cózar and others, ‘Plastic Debris in the Open Ocean’..., 10239. 376 Erik van Sebille and others, ‘A Global Inventory..., 1.
rests on the seabed.377 These figures mean that plastic debris estimates in the oceans may
have been vastly underestimate. In reality, there is greater plastic accumulation than what was previously suspected.
It was known that the deep sea – the deeper parts of the ocean, especially those beyond the edge of the continental shelf, in the range of 200m to 2500m – could be a plastic debris repository, but not at this scale. A study from 2014, exposed that microplastics, in the form of fibres, were up to four orders of magnitude more abundant (per unit volume) in deep-sea sediments from the Atlantic Ocean, Mediterranean Sea and Indian Ocean than in contaminated sea surface waters.378 Given the vastness of the deep sea and the prevalence of
microplastics at all sites investigated, the deep sea floor appears to provide an answer to the question where is all the plastic?
Due to technical challenges and prohibitive costs of conducting research in the deep sea, little is known about the abundance, types, sources, the depth in which debris is penetrating and its impacts on this vast habitat. Opportunely, more and more studies are being carried out and the most recent came from Japan.379 From 1982 to 2015, plastic debris occurrences in the deep sea of six oceanic regions (South Atlantic, North Atlantic, Indian Ocean, South Pacific, Eastern North Pacific, and Western North Pacific) were archived in a database. Its analysis revealed that 3425 man-made debris items have been found in 5010 dives. More than 33% of this debris was macro-plastic, 89% of which was single-use products. In areas deeper than 6000m, these ratios increased to 52% and 92%, respectively. It is noteworthy that the relative dominance of plastic debris was larger at greater depths than at shallower depths (18-22% at >1000 m) and it was almost exclusively single-use plastic.380
377 European Commission, ‘Commission Staff Working Document - Overview of EU Policies, Legislation and
Initiatives Related to Marine Litter’ SWD(2012) 365 final, 3.
378 Plastic microfiber abundance in the sediments ranged from 1.4 to 40 pieces per 50ml, and samples from four
locations in the Indian Ocean showed that microplastics had also accumulated on the surface of octocorals. Rayon, a semi-synthetic fibre was detected in all samples, contributing to 56.9% of the total number of fibres seen. Of the remaining fibres, polyester was the most prevalent (53.4%), followed by other plastics, which included polyamides and acetate (34.1%), then acrylic (12.4%). See Lucy C Woodall and others, ‘The Deep Sea is a Major Sink for Microplastic Debris’ (2014) 1 Royal Society Open Science 5.
379 The Global Oceanographic Data Centre of the Japan Agency for Marine-Earth Science and Technology
launched in March 2017 the Deep-sea Debris Database for public use, where photographs and videos of debris that have been collected since 1983 by deep-sea submersibles and remotely operated vehicles were archived. See Sanae Chiba and others, ‘Human Footprint in the Abyss: 30 Year Records of Deep-sea Plastic Debris’ (2018) Marine Policy 1-9, available at <https://doi.org/10.1016/j.marpol.2018.03.022>. In this study, evidence of distribution of plastic debris was shown in the abyssal zone (4000-6000m) and for the first time in the hadal zone (>6000m), that includes the world’s deepest trench at over 10000m deep.
380 ibid 1 and 4. In a study off the California coast, the relative occurrence of plastic debris increased in the 2000-
These results may indicate that previous studies may have greatly underestimated the extent of anthropogenic marine debris on the seafloor due to limitations in observing deeper regions. The deepest record was a plastic bag at 10898m in the Mariana Trench, which is actually designated as a Marine National Monument Marine Protected Area by the USA. However, and has seen before, this designation cannot prevent the hazards of plastic pollution.381
The data showed that, in addition to resource exploitation and industrial development, the influence of land-based human activities, even in the form of single-use products, has reached the deepest parts of the sea in areas more than 1000km from the mainland. Additionally, this study showed that association of plastic debris and deep-sea biota occurs at a relatively high frequency especially bearing in mind the low biomass and/or sporadic distribution of deep-sea ecosystems. Nearly 17% of debris images were found with at least one organism, and entanglement of plastic bags were detected even in the cold seep communities. There are reasons to believe that all pelagic, mesopelagic, and deep-sea species may be at risk.382
European deep waters were also surveyed, by various European institutions between 1999 and 2011.383 Across 32 sites, plastic (bags, derelict fishing lines and nets) was the most prevalent waste item found on the seafloor. Waste was found at all sites and all depths sampled, but the sites with the highest waste density were found principally closer to shore – with the exception of the Gulf of Lion –, such as the Lisbon Canyon, the Blanes Canyon, the Guilvinec Canyon and the Setúbal Canyon. Waste was even found in deepest and remote locations, such as the Charlie-Gibbs Fracture Zone across the Mid-Atlantic Ridge.
Similar conclusions were taken after the remotely operated vehicle dives in Portugal
plastic among the plastic debris. It is plausible that single-use plastic, having high buoyancy, tends to be transported far distances via oceanic currents and other physical mechanisms from coastal regions before settling and accumulating on the deep-sea floor. Additionally, the findings provide evidence that submarine canyons – and there are as many as 660 submarine canyons worldwide with an estimated 15% with nearshore heads that receive substantial coastal sediment inputs – collect debris and act as conduits for debris transport from coastal to deep sea. See Kyra Schlining and others, ‘Debris in the Deep: Using a 22-year Video Annotation Data Base to Survey Marine Litter in Monterey Canyon, Central California, USA’ (2013) 79 Deep-Sea Research 96-105. To elaborate this study, the team reviewed 1149 video records of marine debris from 22-years of remotely operated vehicle deployments in Monterey Bay, covering depths from 25m to 3971m. The majority of debris was plastic (33%) and metal (23%).
381 ibid 1 and 6. 382 ibid 5 and 6.
383 Christopher K Pham and others, ‘Marine Litter Distribution and Density in European Seas, from the Shelves to
Deep Basins’ (2014) 9(4) Plos One 1-13. Surveyed sites were located on continental shelves and slopes, submarine canyons (where litter originating from land accumulates in large quantities), seamounts, banks, mounds, ocean ridges and deep basins, at depths ranging from 35 to 4500m.
submarine canyons of Lisbon, Setúbal, Cascais and Nazaré.384 Waste was more abundant at
sites closer to the coastline and population centres than those further out to sea, suggesting the majority of the litter was land sourced. As a matter of fact, although plastic (fragments, sheets, bags, bottles, polystyrene cups, packaging, buoys, rubber gloves, boots, tyres) was the dominant type of marine debris, followed by fishing gear, the fact is that the dimension of the cities and the existence or not of rivers influenced the amount and the type of plastic waste. That is why fishing gear represented 37% of the total waste in Nazaré, and juts 9% in the other canyons.
As more areas of seafloor are being explored, benthic waste is progressively being revealed to be more widespread than previously assumed. In reality, understanding spatial patterns in waste abundance and distribution in the deep sea is challenging, owing to the lack of standardisation in the sampling and analytical methodologies used. Furthermore, the high cost of sampling the deep sea limits the ability to perform standardised surveys across large areas to better understand the extent of marine plastic pollution.385 Few doubts exist though regarding the degradation process. If most polymers are highly persistent in the marine environment, in the depths where oxygen concentrations are lower and light is absent, the degradation is much slower.386 That is mostly why the accumulation trends in the deep sea are of special concern.
384 Gideon Mordecai, ‘Litter in Submarine Canyons off the West Coast of Portugal’ (2011) 58 Deep-Sea Research
II 2489-96. For more reliable data on Portuguese waters see Sara Sá and others, ‘Spatial Distribution if Floating Marine Debris in Offshore Continental Portuguese Waters’(2015) 104(1-2) MPB 269-78.
385 Christopher K Pham and others, ‘Marine Litter Distribution..., 3.
V. Sources of Marine Plastic Debris
As expected, plastic pollution has a large number of concrete sources. Its identification – when possible – is important to: determine accurately the quantities of plastics and microplastics entering the sea; provide an indication of regional and local sources; determine the feasibility of introducing management measures; reduce the inputs; and even to solve the problem by adjusting legislative measures or by creating new ones.
Plastic materials are manufactured onshore, but plastic waste can be produced in land, far or near the shore or other water sources, and at sea. At any phase of plastic’s lifecycle, product can get lost, becoming waste, if it was not already classified as waste at the time. As already demonstrated, plastic waste is ending up in the sea and the pathways are water, especially riverine transport – and this is the main reason why we will also address rivers in this section –, the atmosphere (wind and storms) and direct deposition into the sea.
In view of the above, marine debris researchers traditionally classify debris sources as either land- or ocean-based, depending on where debris enters the water. In 1991, GESAMP estimated that globally 80% of marine litter was coming from land-based sources, and 20% from ocean-based sources.387 Although adopted by the scientific community over the years, we note that these estimates may not be the most accurate since they were grounded in the belief that plastic waste was typically buoyant and that much of it could be found