Collaborative Research: Changes in Microbial Composition and Metabolite Production Associated with Sinking Particles in the California Current System

The natural processes by which the ocean takes up carbon dioxide from the atmosphere and removes it to the deep sea are collectively called the ‘biological carbon pump.’ These processes are regulated, in part, by microscopic organisms attached to sinking organic particles. This study will use chemical analyses and information about the identity and metabolisms of particle-associated bacteria to understand how the composition of sinking particles influences microbial function and survival. Broadly, the project will examine how microbes control whether carbon is preserved in the deep ocean or recycled back to carbon dioxide. The project will strengthen scientific understanding of carbon cycle processes that affect coastal ecosystem health and fisheries productivity along the U.S. West Coast. In addition, it will advance national leadership in ocean science and data integration, support workforce development through training of early-career scientists and contribute to open-source research tools and education. Heterotrophic bacteria attached to sinking particles play a central role in attenuating particulate organic carbon (POC) flux and modulating oxygen concentrations in the ocean’s interior. However, the extent to which microbial community composition and metabolism are shaped by particle composition—and how microbial activity, in turn, transforms POC—remains poorly constrained. By characterizing the composition of organic matter across the particulate—dissolved continuum within the California Current Ecosystem Long-Term Ecological Research site, this project aims to use an integrated multi-omics approach to examine microbe–particle interactions in this highly productive and dynamic ecosystem. The changing organic chemistry of sinking and suspended particles between 50 m and 450 m depth will be assessed using a combination of targeted and untargeted metabolomic fingerprinting techniques, primarily based on liquid chromatography coupled with tandem mass spectrometry. Similarly, metagenomic and metatranscriptomic datasets from the same particle samples will be generated to characterize the composition and metabolic potential of microbial communities associated with sinking and suspended particulate organic matter. Together, these chemical and genomic datasets will be used to investigate sinking particle dynamics, interactions between sinking and suspended particles, and the succession of particle-associated microbial metabolic traits with depth. An additional goal of the work is to refine and streamline this integrated research framework to encourage its broader adoption and expand the database of coupled metabolomic and metagenomic analyses. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2547562 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Lihini Aluwihare | Institution: University of California-San Diego Scripps Inst of Oceanography, LA JOLLA, CA | Award Amount: $516,832 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2547562 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2547562.html