Written by Claire Lacey.
If you’ve never come across it, the idea of “Plastic Free July” originated in Western Australia in 2011 as an initiative of the Plastic Free Foundation. It was created as a challenge encouraging individuals to reduce the use of plastics during the month of July. This year participants can sign up and pledge to either avoid single-use plastic packaging, try and reduce their use of takeaway items (plastic bottles, take-away cups and so on), or go completely plastic-free. You can challenge yourself for a day, a week, a month, or longer. The campaign has absolutely caught the public attention, with their website stating a reduction of more than 300 million kgs (660 million lbs.) of plastic waste globally, attributed to this initiative.
As environmental issues go, this one has a comparatively high level of public awareness; whilst many people have never considered the impact of, say, ocean noise on marine life, almost everyone you ask will have some level of familiarity with at least some of the issues that result from plastic debris in the marine environment. Despite this awareness, it remains as much of an issue as ever; with plastic representing up to 90% of the total litter found on beaches, shorelines, and the seabed (see here).
Marine plastics cause issues in 3 main ways. These are a) entangling animals (which can cause direct injury and death), b) animals eating (ingesting) plastic trash – which causes internal damage and can result in starvation), and c) chemical leaching – where harmful chemicals are released from the plastic or the surface of the plastic as it is slowly broken down. Graphic by Anna Schmalz
Types of plastic pollution
Macroplastics are those we are most familiar with. They are classified as plastic items larger than 5mm (~1/8 inch), so this category includes litter, discarded fishing gear, plastic bags – all the stuff we see when out walking the beach. This can cause direct injury to marine life via entanglement or by ingestion. To those of us working on the oceans regularly, we see more reminders than we’d like of this issue. Earlier this year, a sperm whale stranded on Kaua’i; plastic found in the stomach of this animal is suspected to have been a contributing factor in its death (read more here).MMRP Researchers also come across this issue in their work, including working to disentangle humpback whales caught up in discarded fishing gear (see Martin's blog post).
Marine plastics are often described by size class; macroplastics are large pieces, including litter. Microplastics are smaller than 5mm, and nanoplastics are smaller than 1μm.
Plastic is a very tough material, but objects do still deteriorate slowly – particularly with exposure to UV and salinity. Think about what happens to that plastic yard chair left outside all year round… Macroplastics break up into microplastics – those smaller than 5mm- and nanoplastics – those smaller than 1μm. These smaller pieces can also enter the environment directly, coming from the plastic industry and from things like clothing microfibers. These tiny pieces are very easily ingested; either eaten deliberately if the animal mistakes them for prey items; by accumulation through the food chain, as predator species such as marine mammals “take on” the burden of all of the plastic previously eaten by their prey; or by being swallowed inadvertently from the water as the animal opens its mouth to take in prey. Quantifying the impact of this issue on marine mammals is extremely challenging, due to the number of species, feeding strategies and habitats involved, however, a 2022 study by Kahane-Rapport and colleagues estimated blue whales to be exposed to more than 10 million pieces of microplastic per day during their peak feeding periods.
Example of the mechanisms by which whales can ingest plastic – taken from a 2021 paper by Zantis and colleagues
It’s not just an issue for baleen whales – ingestion is also a problem for filter-feeding rays (like mantas) and filter-feeding sharks (like whale sharks) (see study by Germanov and colleagues (2018) for more info). This ingestion can cause physical damage to internal organs and can stop nutrients from being properly absorbed. They can also cause chemical damage, as toxic chemicals are released from the plastic itself as it slowly breaks down. This is the least well-studied area of plastic pollution, and researchers are still trying to fully understand the effects of this issue.
All of this shows that despite huge public awareness of this issue, it is a long way from being resolved. We’ll be using the MMRP Instagram account throughout July to further highlight this issue so keep an eye out for more information, and suggestions of how you can make a difference. And if you want to sign up for the Plastic Free July Challenge, you can do so here!