Human-made chemicals embedded across global oceans, major study finds

Human-made chemicals have become woven into the chemistry of the ocean, a major new study has found, offering one of the clearest pictures yet of how deeply industrial pollution has penetrated marine ecosystems.

Led by Jarmo-Charles Kalinski of Rhodes University and Daniel Petras of the University of California, Riverside, the research, published in Nature Geoscience, brings together a large global collaboration: 30 scientists across 19 institutions spanning seven countries, including South Africa, the US, Germany, Brazil, the Netherlands, Taiwan and Chile.

Their project is the largest meta-analysis of marine non-targeted mass spectrometry data to date, marking a significant step beyond previous studies that were limited to small, regionally focused areas. 

By combining high-resolution mass spectrometry with scalable computational tools, the team mapped human-made organic chemicals — known as xenobiotics, which do not naturally occur in marine ecosystems — across 2 315 seawater samples from the Pacific, Atlantic and Indian Oceans.

The study also incorporated earlier research by Kalinski in Algoa Bay, which examined estuaries including the Swartkops and Sundays rivers, providing valuable insight into how human chemicals enter coastal waters.

“I expected there to be much more cohesive or coherent knowledge available when I started this project and the fact that there is not is quite worrisome,” Kalinski said in a statement. 

“We found that industrial chemicals, many of which are rarely monitored, may be far more abundant and widespread than previously recognised.”

The authors said their analysis revealed that common pollutants such as pesticides and pharmaceuticals were predominantly detected in estuaries and coastal areas but declined with distance from shore, whereas industrial chemicals and additives, including polyalkylene glycols, phthalates and organophosphates, were widely distributed across marine ecosystems.

In coastal waters, human-derived molecules accounted for up to 20% of the detected dissolved organic matter. Even 20km from shore, the chemicals represented about 1% of the total signal.

The “chemical fingerprint” allows scientists to measure the extent of human impact on the ocean’s natural chemistry. While the long-term ecological consequences remain largely unknown, there is concern that the chemicals could affect marine microbial processes and the ocean’s carbon cycle, potentially altering ecosystem dynamics in ways that are difficult to predict.

While much of the focus has been on coastal hotspots, the persistence of industrial compounds in open-ocean waters reveals how human activity has left a measurable imprint on the global ocean.

Scientists warn that the chemicals might have cascading effects on marine ecosystems, fisheries and the ocean’s carbon cycle, with potential implications for climate regulation and food security. 

A key breakthrough was the combination of standardised mass spectrometry methods with scalable computational approaches, which allowed thousands of samples from separate studies to be analysed together as a single, unified dataset.

“This work was only possible because of the efforts of our collaborators around the globe and open science,” said Petras. “By making our data public, we hope to accelerate research and enable a more complete understanding of human chemical impacts on the ocean.”

Sharing robust, standardised data is a responsibility for the global scientific community. “It’s our duty as scientists to make robust research data available for everyone because we are working together: the scientific community and the human community in a bigger context,” added Kalinski.

The study underscores the need for long-term, standardised monitoring to track the presence and impact of human-made chemicals in marine ecosystems. 

By combining international collaboration with open data, scientists hope to better understand and mitigate the human impact on the oceans. “Long-term monitoring and open-science collaboration are essential to understand the risks posed by human-made chemicals to marine ecosystems,” Kalinski added.