Plastic Debris and 'Microplastics' Monitoring

While doing monitoring and assessment activities in the Grand Police area, we noticed something in the beach sand that we haven’t noticed at any of the other beaches around Mahé: many small pieces of broken up plastic. Though there is no as yet global standardised size, these plastic fragments are referred to based on their size, generally; macroplastics if they are larger than 25 mm, mesoplastics if they are between 5 mm and 25 mm, and microplastics if they are smaller than 5 mm. Plastic fragments such as these represent one of the lesser understood, yet seriously concerning, impacts that marine debris has on the health of our oceans and us.

While primary microplastics enter waterways and eventually the oceans in a micro size, secondary microplastics – such as the ones that are washed up on Grand Police beach – are the result of larger plastic debris in the ocean (eg. plastic bottles) breaking down into smaller and smaller pieces due to factors such as the movement of the waves and the sun’s rays. But it doesn’t end there. As they continue to fragment into ever smaller pieces, they absorb organic pollutants and toxins in the seawater like a sponge, and are then often mistaken for food and ingested by marine life. Accumulation of this kind of marine debris in the gut of various species can cause them to die of starvation. Little yet has been confirmed about the impacts that this may have on the health of humans, but it is possible that the chemical contaminants in the gut of fish species may be released from the gut wall into other tissues, which are then consumed by humans.  

It is undeniable that the ultimate measure to stop this problem from getting any worse is to stop plastic debris from entering our oceans altogether. However, until that can be achieved, we have to monitor and measure these plastic fragments washing up on the beach in order to try understand the scale of the problem and how best to manage it – “what gets measured, gets managed”. We do this by using sieves of two different mesh sizes to sift the sand along the strand line at a certain area on the beach. We then take the collected fragments back to our offices where we carefully measure and quantify them. Meticulous work it is!