Wash Them Down the Microplastic Sink
Eelgrass’s impressive ability to sink and hold marine microplastics could be a next step in relieving ocean microplastic pollution.
Most of us are familiar with the ongoing problem of plastic pollution in our oceans. The International Union for Conservation of Nature estimates that over 14 million tons of plastic end up in the ocean each year. Through UV degradation and choppy currents, these big pieces of plastic break down into tiny microplastics (pieces less than 5mm in size) which threaten marine animals that mistake these pollutants for food. Additionally, the plastics may work their way up the food chain as predators consume microplastic-affected animals, eventually appearing inside humans. But, what if there was a way we could trap many of these plastics before they make their way into food webs?
Scientists are now looking into using eelgrass (a type of seagrass) as a bioremediation crop for marine microplastics. A study from the Ocean University of China shows that eelgrass has a remarkable ability to trap microplastics in the sediment by adhering the particles to their leaves. The eelgrass achieves this by slowing the water down as it flows through the blades long enough for microplastics to sink down to the sediment. Moreover, eelgrass attaches their own bacterial community to the particles as they brush by, causing microplastics to stick to the leaves or sink into the sediment.
Due to these properties, eelgrass beds are disproportionately higher in microplastic concentration compared to surrounding sediment. However, this can be detrimental to the animals that live within eelgrass beds, including mussels, crabs, sea snails, and organisms that eat the eelgrass leaves.
Although this seems like a huge drawback to eelgrass growth in the natural environment, a review by Dr. Paula Masiá out of the University of Oviedo raises the idea of using seagrasses as a bioremediation crop for wastewater treatment plants. A huge amount of coastal microplastics come from stormwater run-off and sewage sludge. Despite mentioning that “further investigations should target the best methods for growing resistant seagrasses in sludge waters,” Masiá’s research suggests that using the plastic sinking properties of eelgrass could keep a significant amount of microplastics from entering the ocean.
To sweeten the deal, the National Center for Biotechnology Information recently published a review looking at all the different ways marine bacteria, fungi, and microalgae (all of which are associated with the microbial communities of eelgrass) facilitate the degradation of microplastics. They suggest that microplastics that are adhered to the leaves of eelgrass are being degraded at an accelerated rate by the microbes, preventing the particles from floating around the ocean.
Dr. Anna Sanchez-Vidal, a prominent researcher of seagrasses, posits that “given the ever-increasing plastic load reaching our oceans, seagrass ecosystems such as [those of] P. oceanica [a type of seagrass] … will play a crucial role [in mitigating this problem].”
About the Author: Andrew Matayoshi
Andrew Matayoshi is a biological sciences major at UC Davis with an interest in marine ecology. He is particularly interested in researching coastal invasive species as well as coastal anthropogenic stressors that affect some of the most productive ecosystems in the world such as eelgrass beds. Andrew is not only passionate about research, but also finding implementable solutions to the big problems facing our coast which prompted him to write this piece. Solutions are needed now more than ever which is why Andrew helps run a startup dedicated to kelp forest restoration, and hopes by writing pieces like this and investigating innovative solutions, he can inspire more people to make actionable changes in their environment.
References
Abidli S, Lahbib Y, Trigui El Menif N. Microplastics in commercial molluscs from the lagoon of Bizerte (Northern Tunisia). Marine Pollution Bulletin. 2019;142:243–252. doi:10.1016/j.marpolbul.2019.03.048
Masiá P, Sol D, Ardura A, Laca A, Borrell YJ, Dopico E, Laca A, Machado-Schiaffino G, Díaz M, Garcia-Vazquez E. Bioremediation as a promising strategy for microplastics removal in wastewater treatment plants. Marine Pollution Bulletin. 2020;156:111252. doi:10.1016/j.marpolbul.2020.111252 3. Sanchez-Vidal A, Canals M, de Haan WP, Romero J, Veny M. Seagrasses provide a novel ecosystem service by trapping marine plastics. Scientific Reports. 2021;11(1):254. doi:10.1038/s41598-020-79370-3
Viel T, Manfra L, Zupo V, Libralato G, Cocca M, Costantini M. Biodegradation of plastics induced by marine organisms: future perspectives for bioremediation approaches. Polymers. 2023;15(12). doi:10.3390/polym15122673
Zhao L, Ru S, He J, Zhang Z, Song X, Wang D, Li X, Wang J. Eelgrass (Zostera marina) and its epiphytic bacteria facilitate the sinking of microplastics in the seawater. Environmental Pollution. 2022;292(Pt A):118337. doi:10.1016/j.envpol.2021.118337