Plastic pollution in our oceans has been a persistent concern, and a recent study published in Nature offers new insights into what happens to plastics once they enter the ocean. Conducted by a team of scientists, this research addresses the longstanding mystery surrounding the discrepancy between estimates of plastic entering the ocean and the amount observed on its surface.

The Mystery of Missing Plastics

A significant puzzle in the realm of oceanic plastic pollution has been the mismatch between estimates of plastic entering the ocean and the visible plastic debris floating on the ocean’s surface. Recent estimates have shown that plastic input into the ocean can be significantly higher than what is observed on the surface. Several theories have emerged to explain this gap, including potential overestimations of input, various removal processes, and plastic fragmentation.

A Comprehensive 3D Model

Fig. 2 Fluxes (top and bottom) are given in kilotonnes per year; standing stocks (left and right) are given in kilotonnes. Sizes of objects are not to scale. Fragmentation loss is defined as particles becoming smaller than 0.1 mm. Credit: thisillustrations.com.

To unravel this mystery, the researchers developed a comprehensive 3D global marine mass budget for buoyant plastics. They gathered data from diverse marine sources, including coastlines, ocean surfaces, and deep ocean regions, while considering a wide range of particle sizes, ranging from 0.1 to 1,600.0 millimeters.

Key Findings

The study’s findings provide critical insights into the fate of marine plastics:

1. Dominance of Larger Plastics: The research highlights that plastics larger than 25 millimeters constitute over 95% of the initially buoyant marine plastic mass, totaling 3,100 out of 3,200 kilotonnes in 2020.

2. Revised Ocean Plastic Input: The study estimates an annual ocean plastic input of approximately 500 kilotonnes, a considerably lower figure than previous estimates. This challenges earlier assumptions about the extent of plastic pollution entering oceans.

3. No Missing Sink: The research suggests that there isn’t a “missing sink” for marine plastic pollution. This implies that plastic entering the ocean accumulates rather than vanishes, posing a long-term threat to marine ecosystems.

4. Extended Residence Times: Plastics remain in the marine environment for more extended periods than previously believed. This prolonged presence could harm marine ecosystems if effective countermeasures and prevention strategies aren’t implemented.

5. Fragmentation Matters: Fragmentation of plastics into smaller particles significantly contributes to the increasing number of smaller plastic particles. These fragments are often underestimated in mass budget analyses.

6. Types of Plastics Studied: The research primarily focused on buoyant plastics initially entering the marine environment, such as polyethylene, polypropylene, and polystyrene, which constitute the majority of marine plastic pollution.

Implications for the Future

The research holds significant implications for understanding and addressing marine plastic pollution:

– Long-Term Impact: Plastics persist in oceans for extended durations, with potential increasing harm to marine ecosystems over time if mitigation strategies and cleanup efforts remain insufficient.

– Reevaluating the Problem: The study challenges previous assumptions about the scale of plastic pollution in oceans, underscoring the urgency of global efforts to reduce plastic emissions and protect our oceans.

– Importance of Particle Size Analysis: The research emphasizes the importance of accurately assessing different particle sizes in mass budget studies, given that larger plastics dominate the total mass.

For more detailed information, you can access the full study here.