Most of the pollution running into the seas off the southern coast of the United States is coming from rivers, not wastewater treatment plants, exposing critical wildlife habitats in the Gulf of Mexico to growing threats from microplastics and other pollutants.

New research from the CMCC suggests that tiny plastic particles are accumulating in areas crucial to marine life, including sea turtle habitats, as well as marine environments inhabited by red snapper and dolphins – threatening both biodiversity and food security.

A study published in the journal, npj Emerging Contaminants demonstrates how computer modelling can map the movement and impact of these pollutants “with unprecedented precision”, using advanced models to track different sizes and types of microplastics over short periods across three years in the northern Gulf of Mexico.

“The findings paint a concerning picture of pollution patterns that directly threaten both marine ecosystems and the seafood that reaches consumers across the globe,” the study’s authors have said. “The Gulf of Mexico is increasingly polluted by tiny plastic particles.”

Most of that pollution is making its way there from rivers and not from wastewater treatment plants, the study has found. These findings challenge common assumptions about the sources of microplastic pollution. It also found that heavier plastics tend to settle at the bottom of the ocean, while floating particles show surprising resilience to wave motions.

A major buildup of microplastics was identified west of the Mississippi River Delta, creating a pollution hotspot in waters that serve as critical habitat for numerous marine species.

The study’s approach combines plastic pollution mapping with detailed analysis of marine species distributions, creating an unprecedented view of where these threats overlap. The implications extend directly to human health and food security.

“The fact that plastic impacts regions of intense fishery (which means we’re ingesting some) is often the best way to activate a policy response or gain public interest,” said CMCC scientist, Annalisa Bracco, co-author of the study.

This is the latest study to map out the extent of plastic pollution within North American marine environments. Earlier this month, researchers at Tulane University, New Orleans published a global assessment of where plastics pose the greatest ecological risks to marine ecosystems. It found that the highest risk areas weren’t always the ‘garbage patches’ where plastics visibly pile up but often where plastics overlap with higher populations or marine life and pollutants.

These findings led scientists to conclude that even in waters with relatively modest levels of plastic pollution, severe ecological threats can still be faced. These are sentiments echoed by researchers from the CMCC. 

The most recent study also offers more than just a documentation of the ongoing problem in the region but provides a roadmap for action. By identifying specific point sources of plastic pollution, the research enables targeted mitigation activities that could significantly reduce environmental impact.

“It is important to show how state-of-the-art modelling tools can be used to address coastal problems that interest the general public,” said Bracco. “It is somewhat easier to raise awareness of the risks associated with plastic pollution (just one of the many anthropogenic threats) when linking it to fish, turtles, and dolphins instead of simply delivering the likely plastic distribution maps.”

The research also demonstrates the critical importance of making climate and environmental science relevant to everyday concerns. “In other words, it is important to look for ways to make our research relevant to everyday life (in this case, the fish we consume) to help put in motion the change that is needed,” said Bracco.

This comprehensive approach to understanding the microplastic pollution represents a significant advancement in coastal environmental research, providing both the scientific foundation and practical framework needed to protect marine ecosystems and the communities that depend on them.

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