Microplastics - The Silent Pollutant

MICROPLASTICS – THE SILENT POLLUTANT If a plastic bottle is thrown in a pond, after a couple of days it will be significantly visible, covered in green algae, hinting its potential harm to the environment. However, if that same bottle is broken down into small enough pieces, they would not be visible when thrown in to the pond. Although, the very same amount of plastic was dumped in the same pond, one does not register the potential harm to the environment in the same manner.

Automatically, the same net negative effect impacted upon the environment, is even worse due to their smaller size. Microplastics are harming marine communities and habitats silently but effectively.

Microplastics, have been roaming in our oceans for ages, but it was only in the past few years that we have become aware of their brunt. These little pieces of suspended debris can reach sizes invisible to the naked eye. They start off as microbeads, which are very small solid plastic particles normally made from polyethylene, polypropylene and polystyrene.

These substances are added to cosmetics products such as exfoliators, as well as generated by 3D printers, and as a result of small particles in paints and coatings. They are also products of the chemical breakdown of larger plastic debris, ropes and synthetic fabrics due to strong winds and strong wave action or even by sun-induced photo-oxidation. These particles in some way or another move down the wastewater system and reach the oceans.

Although they are extremely small in size their effect is severe on ecosystems from which we benefit. A study found that the concentration of floating plastic in the Mediterranean, can reach a density of 1item per 4m2, with a 100% frequency of occurrence. These densities are dominated by millimetre-sized fragments. All of these can continue breaking down into nanoparticles, and the numbers get more alarming. Taking this into effect, these microplastics are continuously mixed up with bands of plankton in our oceans, which are then filter-fed, suspended or even taken up as detritus by several organisms including; crustaceans, bivalves, gastropods, porifera and many more sessile or crawling organisms on our sea bed. Microplastics are continuously getting incorporated in our ecosystems, by the process of bioaccumulation.

These particles can have organic matter which have small densities such as plant materials, bacteria, chemical contaminants such as pesticides, organo-halides, aromatic hydrocarbons

and heavy metals which adsorb (the permanent attachment of a molecule on the surface of another object yet not chemically incorporated with it to synthesise a new product) onto their surface. The adsorption of such chemicals to the surfaces of these molecules allow these particles to be easily transferred from one part of the ocean to another where they automatically get to disperse all around the world’s oceans.

Organisms are affected, since microplastics do not simply stay roaming round the organism’s body but, they incorporate into the tissues of the organism, creating systematic defects such as; improper feeding patterns, underdeveloped or non-functioning sex organs amongst other mutations which are passed over from one generation to another. The situation is amplified due to other co-occurring problems, which cause similar affects, such as heavy metal poisoning which are still posing an alarming problem. The biggest problem however, is that the effects upon the environment are still not clear. Is bioaccumulation of microplastics, in our environment, the biggest issues or can the situation become more adverse?

The following figure shows the potential pathways of microplastics and their biological interactions:

The public doesn’t have the skills and tools required to rid the oceans of microplastics, however, we all have the potential of the damage being made. Firstly, there must be more awareness on the dumping of waste in the oceans, and how to adequately dispose of it on land. Secondly, we must keep an eye out on the products which have microplastics in them, which may lead to the signalling of a social alarm. This may give way to a radical change in the way of how certain products are made and packaged. Last not least we must always be aware and updated on ongoing research and new findings regarding microplastics and their effects upon our ecosystems, and we must always create a social pressure towards our authorities to take such matters seriously to ensure a healthier world for our precedents and the rest of the generations to come.

References: Galloway, T.; Lewis, C. Current Biology 2017, 27, R445-R446.

The physical impacts of microplastics on marine organisms: A review. Stephanie L. Wright, Richard C. Thompson, Tamara S. Galloway, University of Exeter and University of Plymouth, 2013.