By Petra Dreiser

A paper led by Chelsea M. Rochman, associate professor in the department of ecology & evolutionary biology, and her postdoctoral fellow Erin L. Murphy has been awarded a 2025 Cozzarelli Prize from the journal Proceedings of the National Academy of Sciences (PNAS). The paper, “A Quantitative Risk Assessment Framework for Mortality Due to Macroplastic Ingestion in Seabirds, Marina Mammals, and Sea Turtles,” was co-authored with colleagues from Ocean Conservancy. 

The annual Cozzarelli Prize, named to honour the late PNAS editor-in-chief Nicholas R. Cozzarelli, acknowledges research teams in six categories whose articles published in the journal reflect scientific excellence and originality. 

Rochman and colleagues’ paper is the first global study to quantify the likelihood of mortality caused by the ingestion of macroplastics in sea birds, marine mammals, and sea turtles. Specifically, it asks how much plastic swallowed by an animal is likely too much for it to survive. The work not only fills a gap in missing monitoring and risk-assessment frameworks for macroplastics—increasingly requested by various governments over the past few years— but also for the first time breaks down potentially fatal quantities by plastic type. The researchers differentiated between hard plastics (e.g., water bottles and caps), soft plastics (e.g., plastic bags and films), fishing debris (e.g., fishing line and hooks), and rubber (e.g., balloons). 

In all cases, mortality thresholds proved lower than expected. “Shockingly, even one bottle cap is 95 per cent likely to kill a seabird,” says Rochman, who also serves as head of operations and program lead of Scientific Programming and Application for the U of T Trash Team and was recently recognized as one of the world’s most cited researchers. These stark numbers, she and the team hope, will “underline the urgency of both prevention and cleanup,” translating into “specific, effective plastic-pollution policies” that will also actively contribute to wildlife protection. 

“Chelsea Rochman’s research continues to provide a template for anyone interested in studying the devastating effects of plastics in the environment,” notes EEB chair Joel Levine. “With this particular work, she and her team have documented how easily plastics in the water—a scourge visited on the planet by humanity—can kill sea creatures and turn the food web into a deathtrap. It is encouraging to see this research provide a foundation for policy at a global level.”