When we talk about marine debris, and in particular plastic, the first thing that comes to mind for many people, is plastic bags and bottles. We have, in our efforts to reduce plastic use, have focused a great deal on these larger, more visible items. But they are not the only, nor necessarily the biggest, threat to the marine environment when it comes to plastic. Microplastics, nearly invisible to the naked eye and estimated to number over 5 trillion pieces are now considered a major issue. Before we discuss microplastics however, let’s recap on some important facts about plastic.
- In 2014, the amount of plastic created reached a record 314 million tons, a whopping 38% increase on the figures for 2014 (Plastic Oceans, 2015)
- Estimations of plastic waste reaching the oceans is between 4.8 and 12.7 million metric tons annually (Shim and Thomposon 2015, Wang et al 2016)
- Significant increases in the quantities of plastic in the North Pacific gyre and waters near the British Isles have been recorded between 1972 and 2010 (Wang et al 2016)
- Plastic is resistant to biological degradation and instead fragments into smaller pieces, never truly disappearing (Shah et al 2008, Webb et al 2012)
|Image courtesy of Flora and Fauna, 2013|
Microplastics; what are they?
Any piece of plastic that measure below 5mm in size are considered a microplastic (Li et al 2015, Shim and Thomposon 2015, Wang et al 2016). They are the most common type of plastic found in the oceans (numerically), accounting for 92% of the total number of plastic particles (5.25 trillion) or 13% of the total weight (Shim and Thomposon 2015).
There are two types of microplastic; Primary and (you guessed it) Secondary. Primary microplastics (sometimes called microbeads) are those that were purposefully created by humans for a reason. Those reasons could be for your facial scrub or cleanser type things, sand-blasting equipment or shower-gel stuff. Secondary microplastics on the other hand, come into existence through the fragmentation of larger pieces of plastic (through human breakages and UV light deterioration) (Shim and Thomposon 2015, Wang et al 2016)
These tiny little pieces of plastic can make their way into our marine environment through many different ways. Secondary are commonly born in the ocean, as lost plastic waste endlessly floats in the ocean it fragments under the sun’s UV rays. Primary microplastics find their way into the ocean through long migratory journeys. Some will be a result of poorly managed waste disposal or clean ups, whilst others (the cleansers) are so small they can be washed down the plughole and slip through every type of water treatment, straight into the sea. You have undoubtedly heard the saying ‘all rivers flow to the sea’, and this is true (albeit with some rerouting), so any plastic that reaches the ocean, especially microplastics, are likely to find their way there one day.
The Big Blue
What is next for these baby microplastics as they set out to explore the massive expanse of the ocean? Will they float aimlessly for eternity, drifting wherever the currents take them? Or will they sink down to the depths and become one with the sediment? Or, maybe choose to join the food chain and find themselves eaten? There is a lot of research that discusses the behaviour of microplastics in the ocean, but simply put, they can be split into three categories; Physical, Chemical and Biological.
Physical behaviour relates to their movement in the water, this could be through migration with the currents, or accumulation in one of the massive mid-ocean gyres and even sinking and resting with the sediment at the bottom (Wang et al 2016). On its own, the physical behaviour of microplastics doesn’t really present any concerns or problems with regards to environmental or health issues. However when we couple it with chemical and biological behaviour, it is a different story.
Chemical behaviour relates, primarily, for plastic to undergo chemical changes or absorption of chemicals. As already mentioned, ‘natural’ fragmentation or degradation of plastic can happen, though slowly (even slower in the ocean). This processes, which takes place when plastic is exposed to the suns UV rays, are called ‘photo-oxidative’ and ‘thermos-oxidative’ reactions and result in the polymer (plastics) to change its properties (strength, colour and shape) (Wang et al 2016)
As plastics are broken down into smaller and smaller pieces, the available surface area for a process of absorption increases, which in turn increases the rate of absorption. Research has shown the plastics are veritable sponges when it comes to absorbing chemicals. Persistent Organic Pollutants (POPs) are contaminants that remain in the environment for prolonged periods and can remain a threat to humans and wildlife. Some examples of potential POPs that can be absorbed include Polycyclic Aromatic Hydrocarbons (PAHs), Polychlorinated Biphenyls (PCBs) and Dichlorodiphenylytrichloethane (DDT) (Wang et al 2016, Webb et al 2012).
- There are approximately 100 PAHs out there that are released from burning coal, gas, trash, tobacco, wood and other organic materials. Needless to say, some of these are anticipated to be carcinogens and have been linked to lung, liver and skin cancers (US National Library of Medicine 2015).
- PCBs are man-made organics. They were banned in 1979, but before that were used in products of wide variety (plastics, floor finish, oil, transformers and cable insulation to name a few). During their manufactor and from poor waste management, PCBs leached into the environment and once there, they don’t break down much (persistent!). They have been shown to cause cancer as well as issues with immune, reproductive and nervous systems. So these are bad (EPA, 2013)
- DDT is probably more commonly known and was used as a pesticide until it was banned in many countries. Whilst it hasn’t been shown to cause reproductive or birth defects in humans, tests on animals found some species were susceptible to harm. Whilst humans exposed to it have claimed nausea, confusion, headache, vomiting and fatigue all occur (National Pesticide Information Center, 1999)
The ability for plastic to absorb these harmful chemicals may at first seem like a good thing, a way to get them out of the environment. However, due to the size of the microplastics, and the ease marine species have in ingesting them (even down to plankton!) it is concerning for the health of our oceans and ourselves. Plastic has the ability to absorb and concentrate chemcials, but in our bodies they have the ability to release them and store them in our tissue and fats. If we consider bioaccumulation or biomagnification, we can understand that as we ascend the food chain, the amounts of chemicals increases (based on the number of little fish the bigger fish has to eat, it accumulates chemicals from each of them. This is one of the reasons science says to avoid eating a lot of fish (Tuna!) more than once a week. Mercury and other chemicals are found in higher and higher concentrations which can result in poor health, birth defects and cancers; both for ourselves and life in the oceans. Basically put, our use of plastic is poisoning ourselves and the oceans.
So, in conclusion, we know that macro and microplastics are commonplace in the ocean, increasing annually and migrating across huge expanses of ocean. We know that microplastics are really small and easily ingestible by even the smallest of marine life and that because of this, they are more and more commonly found within the food chain, up to the top predators. We know that microplastics can absorb harmful chemicals and metals, which they store and can then release into body tissues and fats. We know that these chemicals can accumulate within species, and magnify as they move up the trophic level (food web). We know that getting microplastics out of the ocean is a huge challenge that is almost impossible due to the size of nets we’d have to use to collect them catching literally everything.
We also know how we can change this. The choices we make on a daily basis can influence the levels of plastic reaching the oceans. Here is a small list of things you can do to make a difference:
- Don't buy needlesslypackaged items; there is never a need for a plastic wrapped banana
- Always check your shower gels and facial scrubs for the ingredients; Polyethylene, Polypropylene, polyethylene terephthalate, polymethlyl methacrylate or nylon. It is all plastic!
- Pick up plastic trash when you see it on the floor and dispose of properly
- Stop using ‘single-use’ plastic and start carrying reusable bags and bottles
- Campaign to have microbeads banned in your local state (a la California)
- Volunteer with local NGOs working against waste
Help us help you. Change the World.
The Blue Temple Team
Li J, Yang D, Li L, Jabeen K and Shi H (2015) Microplastics in commercial bivalves from China. Environmental Pollution. Elsevier Ltd 207: 190–195. Available at: http://linkinghub.elsevier.com/retrieve/pii/S0269749115300658.
Shah AA, Hasan F, Hameed A and Ahmed S (2008) Biological degradation of plastics: A comprehensive review. Biotechnology Advances 26(3): 246–265.
Shim WJ and Thomposon RC (2015) Microplastics in the Ocean. Archives of Environmental Contamination and Toxicology. Springer US 69(3): 265–268. Available at: "http://dx.doi.org/10.1007/s00244-015-0216-x.
Wang J, Tan Z, Peng J, Qiu Q and Li M (2016) The behaviors of microplastics in the marine environment. Marine Environmental Research. Elsevier Ltd 113: 7–17. Available at: http://linkinghub.elsevier.com/retrieve/pii/S0141113615300659.
Webb H, Arnott J, Crawford R and Ivanova E (2012) Plastic Degradation and Its Environmental Implications with Special Reference to Poly (ethylene terephthalate). Polymers 5(1): 1–18. Available at: http://ehis.ebscohost.com.ezproxy.unal.edu.co/ehost/pdfviewer/pdfviewer?sid=9bbfdbf9-ecd6-4a32-ba36-682939850b58@sessionmgr10&vid=13&hid=2\nhttp://www.mdpi.com/2073-4360/5/1/1/\nhttp://www.mdpi.com/2073-4360/5/1/1/pdf.