As filter feeders, they naturally draw in and expel large quantities of water, which ultimately allows them to accumulate microplastics.
In the past, The Optimist Daily has written about unassuming sea creatures such as sea cucumbers, which, despite their humble appearances, play a vital role in maintaining the health of the entire underwater ecosystem and can reveal important information about how human activity impacts marine environments.
Now, scientists are recognizing the significance of the simple sea squirt (also known as the tunicate Clavelina robusta) and how it can help us monitor the steadily growing quantity of microplastics present in the world’s oceans.
Microplastic is exactly what it sounds like: tiny particles of plastic that are created when larger pieces of plastic waste degrade and slowly crumble. The pieces are so small that they get absorbed into the flesh of the marine life that consumes them, which means that when we sit down to a dish of delicious seafood, we end up ingesting microplastics too, which can eventually lead to health issues.
Scientists have struggled to find an effective way to gather such microscopic particles of plastic from the oceans, but it turns out that sea squirts already do this by nature. Sea squirts are marine invertebrates known as tunicates, and they are a species that have thriving populations throughout the world. As filter feeders, they naturally draw in and expel large quantities of water, which ultimately allows them to accumulate microplastics.
To determine how effective these creatures might be in collecting microplastics, researchers kept sea squirts in tanks containing polystyrene nanoparticles. Then, the sea squirts were “harvested” and put through a chemical digestion process that breaks down the sea squirts’ tissues, leaving behind the microplastics and other residual organic compounds. A technique called asymmetrical-flow field flow fractionation is then employed to separate the microplastics from the organic compounds.
Once the microplastics are separated, they are placed on a specially designed chip that allows the particles to cluster together so that they can be easier to quantify. Raman spectroscopy is then used to identify the chemical structure of the microplastics.
Of course, in the study, the researchers already know that the sea squirts were exposed to polystyrene, however, if wild sea squirts were harvested, then scientists would be able to determine all the different types of plastic waste was present in the environment. This would also inform researchers on which types of plastic are most common, which could then pinpoint their origin and help us effectively address the most problematic sources of plastic waste.
Study source: Microplastics and Nanoplastics
Additional resources: NIST