An analysis of more than 2,300 seawater samples from more than 20 field studies around the globe indicates that human-made chemicals—from plastic additives and industrial lubricants to pharmaceuticals and pesticides—are widespread in the marine environment, particularly in coastal and estuarine waters. The study, co-authored by University of Hawaiʻi at Mānoa oceanographers and led by biochemists at the University of California, Riverside, represents one of the most comprehensive chemical analyses of coastal oceans to date.
The team analyzed seawater samples collected over a decade from coastal regions from the Pacific, Atlantic and Indian Oceans. Reported in Nature Geoscience , the findings show that industrial chemicals, many of which are rarely monitored, are far more abundant and widespread than previously recognized.
"As part of this study we included samples from coral reefs across both the Pacific and Caribbean, including samples throughout Hawaiian and Tahitian ecosystems, and we were struck by how widespread things like pharmaceuticals, pesticides and plastics were even in some remote island reefs and dozens of kilometers offshore," said Craig Nelson, researcher in the UH Mānoa School of Ocean and Earth Science and Technology , graduate chair of oceanography, and one of the senior authors on the paper.
"Even in places we consider relatively pristine, we found clear chemical fingerprints of human activity," said Daniel Petras, assistant professor of biochemistry at University of California, Riverside. "The extent of this influence was surprising."
Impacts nearshore and offshore
The study found that in datasets from coastal environments as much as 20% of the measured organic material was of human origin, compared to about 0.5% in the open ocean. In extreme cases, such as river mouths impacted by untreated or poorly treated wastewater, that figure exceeded 50%. Across all samples, the 248 identified human-derived compounds tracked in this study made up around 2% of the total detected signal.
While pesticides and pharmaceuticals were expected to be most concentrated near shorelines, the study found that industrial compounds, including substances used in plastics, lubricants and consumer products, dominate the anthropogenic (human induced) chemical signal in all areas of the ocean.
The researchers also found that anthropogenic chemicals persist well beyond the coastline. Even more than 20 kilometers offshore, human-derived compounds accounted for roughly 1% of detected organic matter.
