Microplastics Could Impair the Ocean’s Carbon Capture Capacity

Microplastics are not merely present on the ocean’s surface. A comprehensive study on small particles has shown their widespread presence throughout the water column, potentially impacting the ocean’s capacity to sequester carbon from the atmosphere.

“There are countless entities like this all across the ocean’s interior,” states Tracy Mincer from Florida Atlantic University.

Mincer and his team analyzed microplastic data collected over the last decade from nearly 2,000 global locations. While many assessments concentrate on shallow ocean surfaces, their dataset incorporated samples from various depths, including some of the ocean’s deepest regions.

The researchers found microplastics documented precisely where research efforts were focused. This includes the Mariana Trench, where more than 13,000 microplastic particles were recorded, nearly 7 kilometers per cubic meter.

They were taken aback by the uniform distribution of the smallest particles throughout the water column. “While we anticipated finding plastics at both the ocean’s surface and its depths, they were unexpectedly widespread,” remarked Aron Stubbins from Northeastern University, Massachusetts.

Additionally, these plastic polymers contribute significantly to the carbon particles present in the water. At a depth of 2,000 meters, an area less biologically active than the surface, they account for 5% of the carbon content.

The ecological ramifications of these findings are not yet fully understood. One major concern is that buoyant plastics consumed by plankton may decrease the amount of carbon that is effectively transported to deeper layers through fecal pellets and carcasses. This could impede the ocean’s biological carbon pumps, says Stubbins. However, he emphasizes that quantifying the impact of this phenomenon remains a challenge. “We are uncovering a variety of plastics throughout the ocean,” he notes.

“We can no longer afford to overlook the insights of chemists and biologists in understanding how vast ocean systems operate,” stated Douglas McCauley from the University of California, Santa Barbara. He believes this research will clarify the discrepancies between estimates of millions of tons of plastic entering the oceans and the actually measured quantities. “Sadly, it’s not vanishing. Instead, it has dispersed throughout the water as microplastics,” he adds.