Non-Targeted Metabolomics Enables the Prioritization and Tracking of Anthropogenic Pollutants in Coastal Seawater

Anthropogenic pollutants inundate marine ecosystems as human population growth and urbanization rapidly increase along the coast. Our analytical methods are typically aimed at measuring and monitoring a restricted number of compounds. To prioritize coastal anthropogenic impacts in a comprehensive fashion, we applied large-scale non-targeted liquid chromatography tandem mass spectrometry. We integrated an advanced data analysis pipeline that allows scalable comparison of chemotypes between samples in addition to expanded compound annotation using molecular networking. Using this workflow, we explored the chemical impacts of a major rain event in January 2018 in coastal San Diego, USA. We observed the seawater chemotype shift significantly after the rain event. Molecular drivers of this shift could be attributed to multiple anthropogenic compounds, such as pesticides, cleaning products, drugs and chemical additives that could be connected to potential point sources. Expanding the search of identified xenobiotics to other public tandem mass spectrometry datasets, we could further contextualize their origin and show their potential importance in other ecosystems. Ultimately, the mass spectrometry and data analysis pipeline applied here offer a scalable framework for future molecular mapping and monitoring of marine ecosystems, which we hope will contribute to a more deliberate assessment of how chemical pollution impacts marine environments.