Since the 1950′s annual plastic production has increased from 1.5 to 288 million tonnes in 2012 and is still on the rise. Thanks to the “one-use, throw away” mentality typically engrained in society, plastics now account for up to 80% of all marine debris, and approximately 80% of that is derived from terrestrial sources. What impact does all this plastic have on our marine ecosystems? So far, research has mainly focused on larger plastic fragments, that can easily be seen spotted floating about.
These large fragments have obvious impacts, such as entanglement, ingestion and suffocation of seabirds, turtles and mammals. In contrast, the impacts of smaller, less conspicuous (yet very ubiquitous) pieces, called “microplastics” are poorly understood. Microplastics as defined by the National Oceanic and Atmospheric Administration (NOAA) as pieces of plastic less than 5 mm in size, and they can arise from either primary or secondary sources. Primary microplastics are those specifically produced for direct use, such as for industrial abrasives, exfoliants or cosmetics. The prevalence of polyethylene microbeads for example, is quite astounding, check your favourite body-scrub and foundation… it’s even in some toothpastes! Secondary microplastics are inadvertently produced by the breakdown of larger pieces of plastic into smaller fragments from physical, chemical or biological degradation in the ocean, and also from the shedding of synthetic fibres by washing clothes.
Plastic takes a long time to decompose and microplastics end up accumulating in marine environments where they can be ingested by a range of organisms and can even be transferred through the food web. Another worrisome point is that once released into the environment, microplastics can absorb persistent organic pollutants like PCB’s, dioxins and DDT. They can become like “pills” of concentrated toxic chemicals that could be consumed by creatures like worms, shellfish, fish and, eventually, could end up on our plates!
Pollution of natural habitats by microplastics is a global problem that we are only just beginning to understand, but it is one that is expected to get worse as plastic production continues to rise. My research, conducted within the Biogeochemistry Research Group at TCD, explores the wider effects of microplastics on marine ecosystems. Through this work, I hope to provide scientifically sound recommendations that will feed into policy and help protect our ecosystems.