Where are the ocean’s 99% of plastics hiding and what risks does this pose to human health?
Plastic has become an integrated and essential resource in the lives of humans globally. Our dependence on this synthetic, man-made material came after WWII due to its versatility and low cost.¹ However, the accumulation of plastic waste has now reached over 8.3 billion tons, with an annual influx exceeding 9 million tons flowing into the ocean every year.² This staggering amount has led to projections that by 2050, the ocean will have more plastic than fish.² Some of the plastic waste in the marine environment eventually breaks down into microplastics which are pieces of plastic 5mm or smaller. Microplastics have been discovered in all major regions of the world’s oceans, from the north pole to the south. ³ And although we still have much to learn about the consequences of oceans filled with plastic, recent scientific studies reveal the profound impact of these plastic particles on marine ecosystems, wildlife and their ability to enter the human food chain.
I had the opportunity to interview Dr. Ryota Nakajima, group leader of the Marine Plastics Research Group (M-Plastics) at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Dr. Nakajima is a world-class scientist with interests in plastic issues in the deep-sea environment. Through the course of our conversation, I learnt about how the deep ocean harbours the majority of the ocean’s plastic waste, the effect of microplastics on wildlife and humans, and what changes we can expect to see in the coming years.
The Conversation
Before diving into the world of plastics, Dr. Nakajima focused the first decade of his career working on tropical reef systems. ‘I wanted to study tropical rainforest systems, there were no researchers doing that but instead I found some laboratory in my university working on coral reefs, mangroves and those kinds of tropical reef systems that really fascinate me, so I chose coral reefs’. During his masters and PhD he studied the trophic structure of zooplankton and in his last year of graduate school he moved to Malaysia where he studied the behaviours of zooplankton and Diel vertical migration. ‘I found very interesting results. I confirmed that phytoplankton is not enough for sustaining zooplankton biomass but instead detritus and micro-zooplankton is really important’. He also studied the importance of coral mucus, stating that ‘Coral mucus enhances the microbiome and carbon cycle. Coral mucus is very important for sustaining the high productivity in coral reef ecosystems. Without mucus, coral reefs cannot be so diverse’.
Dr. Nakajima came to JAMSTEC as a postdoc in 2012. ‘At that time I was very keen on deep sea ecosystems so I really wanted to come to JAMSTEC’. The Japanese government was in the process of turning 10% of the ocean within their EEZ (Exclusive Economic Zone) into Marine Protected Areas (MPAs). ‘My task was to select which were the best, most scientifically important deep sea places’. Japan’s ministry of environment selected one of his research sites as a Marine Protected Area which it remains today. After 4 years at JAMSTEC working on deep sea chemosynthetic ecosystems such as hydrothermal vents, Dr. Nakajima was eager for a new adventure and set off towards the United States. ‘I wanted to meet scientists overseas and I wanted to know what they’re thinking about so I chose the US. I quit JAMSTEC officially and said bye bye’. However, after completing 2 more years of coral reef study at the Scripps Institution of Oceanography, he returned to JAMSTEC, this time in the field of microplastics and plastic issue. ‘I wanted to come back to JAMSTEC because it is a nice environment for research and I wanted to go back to deep sea studies’.
Where is the Ocean’s 99% of Plastic Waste Hiding?
‘Deepsea plastics' is a very new field. Most plastic has buoyancy and floats on the surface but there are very few scientists working on plastics in the deep sea. Even now it's still mysterious’. Ocean currents create rotating water masses known as gyres which act as a perfect system for accumulating plastic on the surface of the ocean. Currently, there are 5 known garbage patches floating in the ocean’s 5 largest gyres.⁴ But according to Dr. Nakajima, these 0.01 to 0.03 Tg (teragram) of plastics only account for less than 1% of the ocean’s plastics! The other 99% seemingly ‘missing’.⁵
‘Once plastic enters the ocean, it cannot float on the surface forever’. Aside from fishermen’s buoys which remain buoyant, most plastics ‘end up in the deep sea because of factors like biofouling’ – the process in which organisms such as barnacles or algae attach themselves to a material⁶ – in this case, plastics, which make them sink to the ocean floor. Another example he mentioned was the accumulation of microplastics in larvacean mucus housings and their faecal matter, which drops quickly to the sea floor.⁷
The M-Plastics group was implemented in 2019 and focuses research efforts on understanding the impact of plastic on marine ecosystems (especially deep-sea ecosystems). The research group is also developing new technology to identify microplastics as well as, the distribution and abundance of plastics from sea surface to the deep seafloor. Right now, Dr. Nakajima is observing the ocean floor surrounding Japan. Roughly 50% of plastic waste that ends up in the ocean is coming from China and Southeast Asia alone and Japan is believed to be a repository ‘hotspot’ for deepsea plastics.⁸ The Kuroshio current is an ocean current that passes through Southeast Asia and travels north along the Japan archipelago before redirecting eastward toward the Pacific Ocean. ‘The Kuroshio current brings lots of debris from China, Southeast Asia and also South Korea and Japan which end up in the Great Pacific Garbage Patch (GPGP)’.
The Kuroshio Current
The Kuroshio current has two main gyres (circulating water current) which capture and accumulate debris in the centre of their vortices but as Dr. Nakajima explained earlier, plastic ‘really cannot float forever, eventually it goes down’. It is believed that lots of plastic debris is hidden under the centre of these gyres. In 2019, Dr Nakajima travelled to one of these gyres, known as the Kuroshio Extension Recirculation Gyre which sits roughly 500 km offshore of Tokyo city. Using JAMSTEC’s submersible vehicle Shinkai 6500, they reached depths of around 5,700m – 5,800m underwater. When recalling the dive, Dr. Nakajima stated, ‘There was a lot of plastic. When you reach the bottom and turn on the light, immediately you can find plastics. And when you move 10ms, oh there’s plastic, there’s plastic! The oddest one was a food package from a chicken hamburger and at the time (I saw it) it was 35 years old. The printing was vivid and fully intact. When I took it in my hand, I thought, oh this could last at least 100 years for sure’. Even the pilot, with his many experiences diving with the Shinkai 6500 was shocked by the level of plastic waste in such a remote area of the ocean.
Dr. Nakajima explained that white coloured shopping bags are the most abundant debris found in the deep sea. And through his calculations, determined the maximum density of abundance of plastic per square kilometre was 7,000 items. Thus far, this is the largest record of plastic found in the abyssal plains (which covers over 75% of the deep seafloor), giving evidence that Japan is a likely hotspot for deep sea plastics.⁸
This summer (end of August-mid September) the Shinkai 6500 will be used again, this time around the Kuroshio Recirculation Gyre roughly 500 km off Shikoku island. Using JAMSTEC’s supercomputer, plastic debris movement and accumulation below the gyre has been simulated. ‘Debris gets stuck in vast crevices on the seafloor so we can assume that lots of debris goes to the deepsea floor and gets stuck in crevices. That’s what the supercomputer told us so we are going back to the deepsea floor to see if that’s true’.
What Technology is Used for the Detection of Microplastics?
I asked Dr. Nakajima, what phase of the plastic lifecycle causes the most harm? He advised that, ‘Every aspect is a very big problem. Microplastics can turn into nano-plastics but no one can detect nano-plastics in the ocean because there is no technology that can detect it’. However, microplastics can be identified using a Fourier Transform Infrared (FTIR) spectroscopy machine. The machine is highly effective in determining plastic polymers although, is time consuming and laborious to use. Dr. Nakajima explained that, ‘You have to pick up every single piece of microplastic and put it in the machine one by one and have to measure each piece and it takes 20 or 30 seconds to tell you which polymer it is. For each (plastic) particle’. Currently, the M-Plastics group is developing an autonomous system that can filter ocean water using a paper filter and get infrared spectrum and images with a hyperspectral camera – which shows every 6 nanometers from near-to-short wave infrared.9 ‘Each plastic polymer has its own specific hyperspectrum like fingerprint recognition so you can distinguish which polymer type it is. So, wecombine with the filtering machine and hyperspectral imaging and also we use an Artificial Intelligence (AI) system that can help distinguish particles and we use AI to learn how to distinguish the polymer type’. This technique is in its final stages of refinement and is an exciting development for further understanding microplastic polymers. Unfortunately however, it does not solve the issue of plastic waste ending up in the ocean.
Health Risks to Human and Marine Life
Plastic production is a multi-billion dollar industry that feeds our consumerist lifestyles while concurrently, causes harm to over 800 marine and coastal species¹⁰often resulting in death due to entanglement and ingestion. ¹¹,¹² JAMSTEC researchers even discovered a plastic bag in the Mariana Trench at a depth of 10,898m and revealed that at depths greater than 6,000m, 52% of debris observed was macro-plastics, of which 92% was single-use products.¹³ On the other extreme, the breakdown of plastic into microplastics and even smaller particles increases rates of ingestion and the bioaccumulation of toxic chemicals. This causes impaired development in marine wildlife while also accumulating up the food chain to the human level.¹¹,¹²
‘The production of plastics is growing by 5 percent each year so it's skyrocketing. Which means the amount of plastic ending up in the ocean is also increasing’.
In Japan, plastic is used extensively and I wanted to know if the Japanese government plans to tackle the issue of not only plastic waste but also the immense production of plastics. Dr. Nakajima told me about the 2025 UN plastic treaty which will be a global and legally binding agreement to reduce plastic production and greenhouse gas emissions starting in 2025. By 2040, the treaty aims to limit plastic waste entering oceans by 80%, reduce plastic production by 55%, reduce greenhouse gas emissions by 25% and generate 700,000 new jobs.¹⁰ However, the goal is ambitious and likely to be impeded by lobbying and industry groups who make profits from the production of plastic. ‘Countries who produce oil are against the treaty and the direction of Europe and the US is different, also china. When I talk to the government people in Japan, they’re crazy. Their main purpose is to protect industrial plastic in japan. They want to achieve the goal (of) reducing the number (of plastic) yet protecting (the industry). Yeah it's crazy. It doesn’t work’.
But with matters as important as this, it takes more than just meetings, protocols and treaties to create actionable change. Support from individuals and the community as a whole is equally essential. ‘Japanese people use tons and tons of plastics. Everything is covered in plastics. Even in the supermarkets, peaches are covered by film, and styrofoam and finally covered by harder plastic. Why? Even Bananas get wrapped in plastic… come on! We’re gonna have to change our behaviour and thinking about packaging stuff’.
In Japan, there are systemic issues regarding the presentation of foods. ‘Japanese are very sensitive people. If there is a scratch on the surface of an apple they won’t buy it. It’s crazy. Even the farmers, they discard lots of products because of a scratch or stain. They just look for a really clean and nice shape and protect it with plastic. So those kinds of behaviours and customs have to be changed. If they start thinking about it, Japanese people can change easily. There is no connection between the government and the supermarket. We have to work from the government side, also the consumer side, and also the industrial side. We all have to work together to tackle the problem’.
The planning of a plastic treaty gave me hope for a world where plastics will cease to reign but Dr. Nakajima was more pragmatic about the situation. ‘I believe plastic is necessary. Imagine a hospital if they don’t use plastics? We need sanitization. So in certain areas, plastic is a necessary evil’.
But beyond the devastating impact plastic waste has on marine ecosystems and wildlife, studies are showing the severity of chemical additives in plastic to human health. ‘Plastic itself is not the problem. The emerging problem is the chemicals in plastic so-called additives. Some of the major additives are known for their persistence in the environment, bioaccumulation, long-range transportation and toxicity. Once the harmful chemicals are digested in the gut, the chemicals are absorbed and can accumulate and be harmful. It’s lipophilic which means they attach to oils, lipids and organs. It never goes out, simply accumulates, over time, over time’.
Studies in recent years have flagged the health risks of chemicals used in the manufacturing of plastics and other additives including UV stabilisers, flame retardants and heavy metals. These chemicals and additives are referred to as Endocrine Disrupting Chemicals (EDCs) and are found in many types of plastic products. Their prominence in the human body creates inflammation, kidney, liver, and thyroid problems, but can also cause more severe health issues including cancers, neurological impacts, infertility and modifications in male and female reproductive development, affecting future reproduction.¹¹,¹²,¹⁴,¹⁵,¹⁶
But there is light at the end of the tunnel. Dr. Nakajima believes that current fossil-fuel-based plastics can and must be replaced with bioplastics. ‘plastics can be bio-based, not made from petroleum, not from fossil oil but we can create plastic from plants - there is research going into that. If you burn bio-based plastics they produce co2 which was originally absorbed by plants so it isn’t enhancing global warming because it’s a cycle. If you need plastic, it's necessary its bio-based and/or fully recyclable but also at the same time we have to reduce the number of unneeded plastic things’. The future of bioplastics and biodegradable plastics is promising and a worthy topic on its own. Scientists have also discovered a bacterium that can break down PET plastic materials to their original carbon source through enzyme degradation.¹⁸ There is hope that with future research, these degraded materials could also be recycled to create new plastic polymers without the use of fossil fuels.¹⁹
The issue of plastic is beyond the capacity of any one individual or government body. We must address this problem collectively as a society and must each play our part. Whether that means supporting government leaders who enact legislation or shopping at grocery stores that promote recycling and plastic-free alternative packaging. It’s as simple as starting the conversation with the people around you to raise awareness. Dr. Nakajima also hopes to play his part.
It’s not a problem of which country, all countries must tackle this problem. Plastic is a problem in front of us and is now choking us. As I told you, 99% of plastics are missing which means when you go to the ocean, it just disappears and when it disappears you forget it and I just want to tell everyone the situation of plastic in the deep sea and on the seafloor and the fate of plastic and that it lasts more than 100 or even 1000 years and harming our lives and the whole ecosystem. (I want to) raise awareness of plastics, and telling (everyone) is my scientist mission’.
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