Hazards Hidden From the Human Eye: Do Micro- and Nanoplastics Accelerate Climate Change?

The Ocean Cleanup nonprofit’s installation pulling plastic from the Great Pacific Garbage Patch. Source: Smithsonian Magazine

We’ve all heard of the Great Pacific Garbage Patch. This infamous plastic accumulation zone situated between Hawaii and California has become the poster child for plastic pollution. I was first introduced to it when watching a Ted Talk with my classmates in fourth grade on an effort to clean up the expansive patch, showcasing teams with high-tech machinery sweeping pounds of plastic from the marine landfill. Afterwards, I was certainly inspired, convinced that eradication of the Great Pacific Garbage Patch signified the resolution of plastic pollution as a whole. Eight years later, I continue to find cleanup efforts exciting–however, I’ve also developed a more nuanced viewpoint on how to absolve this alarming aspect of the climate crisis. 

It’s important to first acknowledge that the Great Pacific Garbage Patch–or any “patch” of plastic pollution–isn’t really the concentrated island mass of plastic bags, straws, and takeout containers that we may picture. The reality is even more dystopian–99.8% of plastic that has entered the ocean in the last 70 years has sunk below the first few hundred feet of ocean, meaning that the vast majority of plastic lies beneath the surface, interspersed with deep-sea marine ecosystems. What’s more, much of this underwater plastic pollution is composed of microplastics and nanoplastics, broken-down particles ranging from the size of a dime to fragments invisible to the naked eye. The environmental impacts of microplastics are frightening. Not only do these microscopic particles pose equal danger to aquatic life as visible macroplastics, they also hold the potential to disrupt one of the Earth’s largest and most robust carbon sinks.

Macroplastics and broken-down microplastics on the ocean surface. Source: The University of Manchester

So, what exactly is a carbon sink? In simple terms, it’s anything that accumulates and sequesters, or stores, carbon compounds, thereby removing them from the atmosphere. Carbon sequestration, the removal and storage of carbon dioxide, is an essential component of the carbon cycle, as atmospheric carbon dioxide is a prime contributor to the greenhouse effect that instigates climate change. The two largest carbon sinks are vegetation and the ocean, the latter of which performs carbon sequestration through the biological carbon pump. In this pump, dissolved carbon dioxide is absorbed by primary producers, such as phytoplankton, through photosynthesis. Subsequently, this carbon is passed onto marine consumers, who excrete carbon-containing organic matter that is then remineralized on the ocean floor into rocks. Remineralized carbon is not released back into the atmosphere, resulting in a process that captures nearly one-third of carbon emissions produced by humans each year.

Evidently, the ocean’s biological carbon pump is essential. Here’s the problem: the interference of microplastics and nanoplastics is inhibiting its efficacy. Specifically, primary consumers–zooplankton, for instance–consume these plastic particles, incorporating them into their fecal pellets. This slows the sinking rate of carbon-containing organic matter, reducing the chance that carbon will reach the seafloor and be sequestered. Microplastics are also detrimental to the health of organisms integral to the functionality of the biological carbon pump. For instance, high concentrations of microplastics can result in a 45% percent reduction in the growth of numerous phytoplankton species.

This phenomenon is rather daunting, and given that flashy, impressive ocean cleanup operations aren’t a substantial solution, you may be left wondering: what exactly can we do? Well, as for removing existing plastic, projects such as The Ocean Cleanup nonprofit’s initiative are still helpful–although this may not be the most effective manner of combating plastic pollution, scientist Matthias Egger summarizes the situation well in saying, “conservation is not a zero-sum game”. The most crucial course of action is the most obvious: we must produce and use less plastic. Single-use plastics were already banned in the European Union last summer, part of an EU Plastics Strategy that aims to support the formation of a circular economy that produces less waste. This visible action is a model for the rest of the world, as a global plastic purge in the near future is an undeniable necessity for the survival of our oceans and Earth.