Where is all the plastic in the ocean?

About 10 days ago, we went out with a little group of students and we intentionally spilled 138 gr of plastic samples in a small lake in Hong Kong to test our optical plastic particle sensor. After a few seconds we had to stop the test because our experiment became the feast of many fishes and turtles. It was terrifying to see how quickly plastic debris spread, how voraciously animals came to eat it and how difficult it was to clean it up. It took 10 of us, 4 boats and 40 minutes to clean 138 gr of plastic debris with no waves, no current and very moderate wind. Imagine tons of plastic debris in the open sea and all the animals there…

Today  I have been under an avalanche of questions about plastic pollution in the ocean. It seems hard to trust a reliable source of information or maybe it is the science that is moving very fast. People ask me maybe because I have sailed across the gyre myself, collected plastic samples in Hawaii, and nowadays working on an optical plastic sensor with a team of young students in Hong Kong when I am not developing a fleet of sailing robots that I hope one day will be out there measuring plastic and other pollutions like radioactivity, acidification, oil spills, overfishing and other urgent ocean issues. But to be honest I have much more questions than I have answers – at this stage we all do. I am writing to compile some informations I came across recently, trying to make sense and propose some ideas.

 

When we found out

“Every year we produce about 300 million tons of plastic, a portion of which enters and accumulates in the oceans. […] In 2012 alone, 288 million tons of plastic were produced (PlasticsEurope 2013), which is approximately the same weight of the entire human biomass (Walpole et al., 2012). […] The discovery of fragmented plastic during plankton tows of the Sargasso Sea in 1971 led to one of the earliest studies of plastic in the marine environment. Using a 333 micron surface net trawl, Carpenter and Smith collected small fragments of plastics in 1971, resulting in estimates of the presence of plastic particulates at an average of 3,500 pieces and 290 g/km2 in the western Sargasso Sea (Carpenter and Smith, 1972). Shortly after, Colton et al., (1974) surveyed the coastal waters from New England to the Bahamas and confirmed distribution of plastic all along the North Atlantic. These studies have been recently updated in two comprehensive studies of the North Atlantic gyre (K. L. Law et al., 2010; Moret- Ferguson et al., 2010). Indeed, plastic is found in most marine and terrestrial habitats, including bays, estuaries, coral reefs, lakes and the open oceans. (Rochman et al., 2014, Wright et al., 2013). The ingestion rate of plastic particles by mesopelagic fish species in this area is estimated between 12,000 and 24,000 ton/year (Davison and Asch, 2011).
“How the oceans can clean themselves, A feasibility Study” Ocean Cleanup Array, June 2014.

 

What we thought we knew

AVANI-trawl, photo marcus Eriksen

I trust Algalita Foundation and 5 gyres for that I was lucky to meet them in person and they had been to several gyres many times as an independent non-profit organisation. Below are some journeys they have done with a manta trawler as you see a picture of above. They explain their method very well and in simple words here.
Gyre_Sampling_Locations_1999-2008_000
In 2008, we had a horrifying map but we felt somehow confident about the data.

Plastic ocean Ma

In 2010, Dohan and Maximienko  (Illustration above, 2010. Oceanography 23, 94–103.), based on the trawler data by Algalita and other organisations produced this famous simulation of where we should expect plastic to be. Don’t be fooled by some pictures you probably saw of the “plastic continent”, such thing does not exist in the middle of the ocean.

Yet, the Algalita announced that “Estimates of plastic in the world’s oceans exceed 100 million tons. Though 20% comes from ocean sources like derelict fishing gear, 80% comes from land, from our watersheds.” http://www.algalita.org/pdf/PLASTIC%20DEBRIS%20ENGLISH.pdf

So at this stage, we thought, we would find tens of millions of tons of plastic debris in the gyres. Well…

 

What we think we know now

Thanks to Dr Blurton of the Hong Kong Harbour School who sent me the pdf, I was quite shocked with this new publication “Plastic debris in the open ocean” by Andrés Cózara, Fidel Echevarríaa, J. Ignacio González-Gordilloa, Xabier Irigoienb, Bárbara Úbedaa, Santiago Hernández-Leónd, Álvaro T. Palmae, Sandra Navarrof, Juan García-de-Lomasa, Andrea Ruizg, María L. Fernández-de-Puellesh, and Carlos M. Duartei. Good job ladies and gentlemen. The pdf is here : http://www.pnas.org/content/early/2014/06/25/1314705111.full.pdf
I am selecting only some essential information but I recommend you to read the paper, it’s short, only 5 pages + references.

"Concentrations of plastic debris in surface waters of the global ocean" Plastic debris in the open ocean
In 2010 (yes, 4 years ago – but the paper has been published June 6th 2014), the team embarked on a sailing journey around the world as the “Malaspina science expedition” , doing  3,070 ocean samples with a manta trawler. The grey areas is where prior research ( explained above) suggest they would find plastic accumulation, and that was verified as you see with the yellow, orange and red dots. But…

“Those little pieces of plastic, known as microplastics, can last hundreds of years and were detected in 88 percent of the ocean surface sampled during the Malaspina Expedition 2010,” lead researcher and the author of the study Andres Cozar from the University of Cadiz, told AFP. The total amount of plastic in the open-ocean surface is estimated at between 7,000 and 35,000 tons, according to the report. This amount, though big, is lower than the scientists expected.” http://rt.com/news/169564-ocean-surface-covered-plastic/

"Range of the global load of plastic debris in surface waters of the open ocean" Plastic debris in the open ocean

  • Before this paper, much of the attention was focused toward the North Pacific Garbage Patch => turns out all the other oceans are in bad shape too.
  • Before this paper, we knew plastic was present in all oceans but the general consensus was that it was accumulating in the center of the gyres mostly => Now we have measured plastic to be present on 88% of the world ocean surface. Pretty much everywhere.
  • Before this paper, the estimates were ranging from tens of millions of tons to hundred of millions of tons => Now maximum 35’000 tons. [silence] 35’000 tons? That’s it!!!??? Is that amazing good news, or is that bad news!?

 

What we (think we) really know now

Out of the estimated millions of tons of plastic debris we emit, we can now only find at most 35’000 tons spread over 88% of the oceans. S0 we know now where is less than 1% of the plastic we anticipated finding. Where is the 99%+ of the rest of the plastic? This is really embarrassing.

 

The media is going crazy about it

The articles about this are popping out from all part, I wont try to keep track of all the links, because they are pretty much all based on the same paper I mentioned above. Many are spreading panic, instead of awareness unfortunately.

 

What will the Ocean CleanUp  Array collect?

Back in October 2012 “according to Boyan Slat’s calculations, a gyre could realistically be cleaned up in five years’ time, collecting at least 7.25 million tons of plastic combining all gyres. He however does note that an ocean-based cleanup is only half the story, and will therefore have to be paired with ‘radical plastic pollution prevention methods in order to succeed.” (Wikipedia, retrieved July 2nd, 2014). 

In June 2014, in the feasibility study : “The Ocean Cleanup Array is estimated to be 33 times cheaper than conventional cleanup proposals per extracted mass of plastics. In order to extract 70 million kg (or 42 percent) of garbage from the North Pacific Gyre over 10 years, we calculated a total cost of 317 million euro.”

Multilevel Trawl

Sure, the “multi-level trawler” (p102 0f the Feasibility Study)  used by the Ocean Cleanup team is radically different from the “regular manta trawler” everybody else uses. But the difference of plastic quantity is not found here either. There are so many variables to making a correct plastic measurement, the speed of the boat, the size of the mesh, the position of the trawler in the regards to the wake of the boat, the wind and the waves …

So, how can the Ocean Cleanup collect 70’000 tons from the North Pacific Gyre alone if the most recent estimate of ALL the plastic in ALL ocean surface combined is only of 35’000 tons? And how can this information even be trusted when ” Last year, an estimated 150,000 tons of marine plastic debris ended up on the shores of Japan and 300 tons a day on India’s coasts (http://plastic-pollution.org/ retrieved July 3rd 2014)”.  If this recent study  from the Malaspina expedition confirms true, would the collection of plastic debris with the Ocean Cleanup array be less meaningful? And less profitable if at all? But wait, that is not the question. Of course we need to stop emitting plastic in the ocean – that’s not a new idea and that is self-evident. And of course we must collect the plastic that is already out there and will continue to accumulate in the ocean – even if it is expensive instead of profitable. I personally support Boyan Slat and his team. No matter how many people say “this is impossible” someone has got to try. Even if it is to fail, we must try and try again, again we succeed. This technology, or another technology.

But the real question remains : where is the plastic? How can we have plastic measurements dropping so dramatically?

 

How can we find out what is really going on?

Such a large amount of plastic has not disappeared over night, between 2008 (Algalita estimate) and 2010 (Malaspina measurements).

Scientists argue that :

  • some plastic breaks down so small, it goes through the fine plankton net they use. Plastic still floats but we can’t be measured unless we use an extra finer mesh that is probably more fragile, forcing the ship to move the trawler even slower (it was already recommended to sail at 2 Nautical Knots, well up to 8 knots for the fast Erikson trawler).
  • the plastic chemical composition changes causing it to distribute in the water column or sink at the bottom of the ocean
  • the plastic is being ingested by animals and is being pooped, dropping to the bottom of the ocean, or it moves into the food web with all it’s toxics and until it eventually reached our plates

But we don’t know yet in which proportions each of these phenomenon happen at all yet.

 

Some ideas

Optical sensing

If the plastic is so small that it go through the mesh, maybe it is not a mesh we should be using to measure plastic. What about optics?
For a long time Laser Optical Plankton Counters (LOPC) have been in use to measure plankton. We don’t collect physical sample, we collect data, the machine can keep running without interruption, the data is more granular and instantly processed.

Laser-Optical Plankton Counter (LOPC)  Laser-Optical Plankton Counter (LOPC)

In the LOPC, water carrying plankton is  flowing. The plankton is being “flashed” by a laser and it is from the outline it that is then counted automatically.

Laser-Optical Plankton Counter (LOPC)

Mobile sensing platform

Haching a video water channel at the Hong Kong aharbour School

With a motivated group of young students, we hacked a low cost water video channel.

Testing the Ocean Plastic optical sensor, Hong Kong Harbour School

We attached our optical sensor to a small Remote Controlled (RC) power boat. As we sailed, some water that contains plastic debris was video recorded and the plastics bits were also captured in the pink net at the back of the video channel. The point of the pink net is too measure the plastic physically collected that has travelled through the video channel, and compare it with the estimate that we can make from the video alone. We have not done that experiment comparison yet, but it would give us an idea of how reliable our video estimate is in comparison to the real measured weight of plastic collected.

We managed to capture video of plastic particles moving through the video channel. This still very rough.

 

Motion tracking of plastic parts


We have been very lucky to get some help from Edward Fung who started to tinker with the video on OpenCV.

 

Isolation and quantification of plastic

Now, it would be great if we could find out what is plastic and what is not. One of the greatest difficulty being that plastic debris becomes a habitat or a transport for a lot of marine life. How can an untrained software (as opposed to a machine learning based software) distinguish plastic from something else? Typically a plastic fragment would be wrapped into a “bubble” of organic matter, making it more difficult to isolate from an optical perspective. Thankfully, one student in our team, Brandon Wong found out this research : http://www.idec.com/sgen/technology_solution/our_core_tech/plastic_sensing.html

“We succeeded in developing technology that is capable of sensing plastics using an InGaAsP (Indium Gallium Arsenide Phosphide) semiconductor laser diode (LD)

It was discovered that upon measuring light absorption spectra in plastics, in the wavelength range of 300 to 3000 nm, the peak values were always observed at or near 1700 nm, regardless of plastic types. This discovery opened the possibility for simple optical sensing of plastics with the use of a LD in this wavelength range. Observation of unique light absorption characteristics within the near infra-red spectrum of each different plastic type has led us to develop the world’s first technology capable of detecting different types of plastics with the use of a LD (with three different wavelengths).”

So this is really exciting if we could use the right “lighting” and camera to optically detect such great variety of plastic. There are several inspiring DIY spectrometer projects out there to get inspired from. Check also the Riffle with Optical data logger capacity.

 

Size adjustment

If we manage to get that optical detection running, the last but not least challenge may be to scale  from a regular webcam to a microscope-scaled system.

 

"Size distribution of floating plastic debris collected during the Malaspina circumnavigation at calm conditions." Plastic debris in the open ocean

According to the research done during the Malaspina Ocean Expedition the plastic particles we are trying to measure are very very small… Could we be heading in the direction of microfluidic systems?

If the plastic debris we are trying to test are incredibly small, could we control the flow in a very precise yet robust way to perform spectral and / or chemical analysis? Many questions to explore…

So with such a system, could we answer the 2 first questions? :

  • sensing plastic that is extremely small
  • sensing plastic that is small and broken and sunk at the bottom of the ocean – that would imply that this machine can be taken thousands of meter deep : super high-pressure resistant

I day dream that a fleet of autonomous sailing robots doing the remote sensing work. In fact the Ocean Cleanup feasibility study mentions the relevance of deploying such sensor network system in it’s recommandation pages :

P439_Ocean cleanup array_TOC_Feasibility_study_lowres

Is that a fleet of Protei right there :) !?

And now the third question ? What part do animals have in the “plastic disappearing” plot? We wont be able to see that in an optical system unless we’re dealing with tiny transparent animals.

 

Animal testing

I feel terrible for even thinking about this but that is just an idea at this stage. What I am about to propose might be totally unethical, I don’t know. Marine biology and toxicology are not my areas at all. Forgive my ignorance and please correct anything wrong that I may propose, please comment to help.

As I used as this post introduction, our experience with dispersing 138gr of plastic had become a spill in a few seconds on which turtles and fishes came to feast. We had to interrupt the experiment and it took 10 of us during 40 minutes to collect 138gr of plastic debris with 4 boats on a lake that had no current, no waves and very moderate wind. What we learnt is that turtles and fishes love to eat plastic. In fact many studies about suffering, dead animal dissection and observation of carcasses indicate that birds, and marine animals feed abundantly on plastic. But how do you measure how much plastic an animal is willing to eat when given the choice?

In a controlled environment – say a box – we place an aquatic animal. We feed this animal a mix of plastic and “real” food in equal quantities with an excess of overall quantity.

  • Will the animal eat more food or plastic (behaviour)? Will that behaviour change over time? Does the animal develop a preference for certain plastic? By the taste? Smell? Texture? Colour? Motion?
  • How much plastic would still remain untouched in the environment?
  • How much plastic will travel through the digestive system?
  • How much plastic would remain within the digestive system? And if so, how much would the plastic be digested if at all?
  • What are the short term symptoms of plastic poisoning (mechanical) ?
  • What are the long term symptom of plastic poisoning (chemical)?
  • What is the lethal dose for type A / B / C / D / Plastic?
  • What is the most lethal shape or size of plastic fragment?
  • Is an animal dead by plastic attractive as a food form for another carcasses-eating animals?
  • When an animal dies and decompose, how much of the overall plastic of the experiment remains?

many more questions could be asked and variables included such as the size of the box, the season, the age of the animal, the sex, social learning doing the experiment with multiple animals simultaneously.

 

Who is active in Hong Kong?

There are several groups in Hong Kong interested in the topic of plastic pollution

 

My non-conclusion

What we thought we know about plastic pollution has just been challenged in a very big way. And I believe this will happen again soon as we investigate.
The plastic pollution is present at a whole different scale, both small for the particle size and huge by it’s distribution over pretty much the entire ocean surface (88%) and abyssal depths.
The effects of plastic pollution at theses scales are still very unknown. As we keep developing new concepts for ocean cleaning we are still lacking understanding of where is the plastic, how is it transformed while travelling great distances? How does it impact marine life? How does plastic and it’s chemical compounds travel through the food chain to our plates? What are the consequences on human health? What can we do about it?

The more we learn about plastic in the ocean and the more we understand how harmful of a substance it is. And as André Cózar concludes in this important paper.

The abundance of nano-scale plastic particles has still not been quantified in the ocean, and the measurements of microplastic in deep ocean are very scarce, although available observations point to a significant abundance of microplastic particles in deep sediments, which invokes a mechanism for the vertical transport of plastic particles, such as biofouling or ingestion. Because plastic inputs into the ocean will probably continue, and even increase, resolving the ultimate pathways and fate of these debris is a matter of urgency.

So many more questions now… But 2 ideas how to investigate. More ideas? Suggestions? Readings?

 

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  1. If you want older references I recommend :
    – 2006 : “Plastic Debris in the World’s Oceans” Greenpeace
    http://www.greenpeace.org/international/en/publications/reports/plastic_ocean_report/

    – 2011 : “Microplastic Litter in the Dutch Marine Environment”
    http://www.noordzeeloket.nl/images/Microplastic%20Litter%20in%20the%20Dutch%20Marine%20Environment_851.pdf

    – 2011 “Plastic Debris in the California Ecosystem” : http://calost.org/pdf/science-initiatives/marine%20debris/Plastic%20Report_10-4-11.pdf

  2. Super interesting panel about plastic pollution recovery with Marcus Eriksen (5 Gyres), Boyan Slat (The Ocean Cleanup), and Nick Mallos (Ocean Conservancy) : http://marinedebris.info/chat/interactive-panel-discussion-utility-feasibility-cleaning-ocean-plastics

    Thanks to Carolyn Campbell for linking to the video.

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