SoMAS Study: Microplastics in Oceans Distort Carbon Cycle Understanding

A study by researchers in Stony Brook University's School of Marine and Atmospheric Sciences (SoMAS) shows that when microplastics are accidentally collected and measured with natural ocean organic particles, the carbon released by plastics during combustion appears as if it came from natural organic matter, which distorts scientists' understanding of the ocean's carbon cycle.

The recent finding is detailed in a paper published in PLOS One.

The carbon cycle in our oceans is critical to the balance of life in ocean waters and for reducing carbon in the atmosphere, a significant process to curbing climate change or global warming.

Microplastics are everywhere in the oceans. These small plastic fragments come from the breakdown of larger plastic items polluting the seas. Once they reach the sea through rivers, wastewater or runoff, they spread through coastal and open-ocean waters.

SoMAS researchers applied a battery of analytical tools routinely used to measure the carbon content in a water or sediment sample. Then they calculated the carbon yield from both microplastics contaminants and sedimentary organic matter.

According to Luis Medina, the corresponding author, such measurements help marine scientists better understand how carbon moves, changes, and is stored in marine environments. The measurements are critical to building models that may help predict environmental changes, such as climate change.

"However, we demonstrate that the tools used to measure carbon in the ocean cannot distinguish between natural carbon from living organisms and carbon that comes from plastic," explains Medina, an expert in ocean biochemistry and assistant professor in SoMAS. "This ultimately means that many measurements of particulate organic carbon may be unintentionally impacted by the presence of microplastics."

For example, an organic sample can be warped due to microfibers from clothing and plastic particles from sampling, storage and processing gear which enter unnoticed and become part of measured carbon inventories.

Some of the carbon measurement differences between the microplastics and organic matter are minor and may not appear to affect full-scale measurements. Yet the authors suggest the carbon yield from microplastics may be quietly distorting decades of carbon measurements of the oceans and influencing models that scientists use to predict climate-related changes.

The authors believe that their experimental results are the first to quantitatively document the potential impacts of plastics contamination on environmental organic matter analysis. And they write that their "results underscore the need to re-evaluate best practices for processing organic matter samples for carbon analysis."

The research was supported, in part, by several grants from the National Science Foundation (NSF) - grants NSF OCE-2023115, and NSF-MRI grant OCE-1336724.