Plastic pollution in the ocean – a quick google search reveals what probably most people’s first guess would be when asked to think about plastic pollution in the ocean. We all know the photos of the floating bottles, shopping bags, ripped flip-flops and straws. These are the known villains in our fight against the plastic tide.
The zero-waste movement, straw-free restaurants and the still fairly recent 5p charge for shopping bags in the UK are our well known and useful weapons against those villains and they seem to be effective. The in 2015 introduced 5p charge on plastic bags for example has reduced the usage of those bags by 85% (The Guardian, 2016). However, there are also other less obvious types of plastic pollution that should deserve perhaps even more or at least an equal role in this fight – microplastics.
Microplastics are pieces of plastic less than 5mm in length, about the size of a sesame seed (NOAA, 2017). Since they are less obvious way of pollution, they have often been overlooked and had a head start in this game since scientists and policy makers are only now catching up and recognizing their importance. Ironically enough, the effect of those smallest agents could have significant impacts especially on some of the biggest and charismatic shark species like the basking shark (Cetorhinus maximus).
Basking sharks are filter feeders wich means they feed entirely on zooplankton near the water surface. It’s estimated that they can live up to 50 years. Both of these aspects of their life history make them particularly vulnerable to the effects of microplastic pollution. (If you want to find out more about them and their lifestyle check out this article by TFUI founder Melissa.)
This is because microplastics tend to accumulate at the surface, especially in areas where the water is relatively stationary or near sea shores. Unfortunately, these are also common foraging habitats for our basking sharks and their prey. It has been estimated that a 7m long basking shark can consume as much as 30.7kg of zooplankton in just one day! Therefore, basking sharks are at great risk of accumulating those microplastics throughout their lifetime. This can cause multiple problems for the shark.
Firstly, microplastics have been shown to transport and contain persistent, bioaccumulative and toxic substances such as PCBs, which have caused for example damage to cells in the nervous system of other fish species. Secondly, toxic substances added to the plastic such as phthalates can leach from the microplastics into the environment. Those have also been shown to influence hormone levels in other vertebrates which can have serious consequences for reproduction and overall population levels. Lastly, the accumulation of microplastics in the tissue of the affected animal can also cause physical harm. Studies with accidentally caught basking sharks in the Mediterranean already showed the presence of toxic PCB substances in their tissues.
where does microplastic come from?
Microplastics come from a variety of sources. Some forms of microplastic are manufactured in their ‘micro’ size, whereas other microplastics come from the breakdown and slow degradation of bigger pieces of plastic. Examples of microplastics that are manufactured in ‘micro’ size include so called “nurdles”, which often act as the base material for industrial plastic production. However, microplastics are also commonly used in the cosmetic industry as exfoliants and can be found in some cleansers and toothpastes. Washing of synthetic clothing can also produced microplastic fibres, which are often not filtered out in wastewater treatment plants and so get to the ocean. So, big chance you actually got some of those secret agents hiding in your closet right now…
what can we do about them?
guest blogger and tfui officer julia jung
TFUI Founder Melissa C. Marquez is author of all animal bios and "Behind the Fins" segments.
SEE MELISSA'S TEDx TALK HERE:
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