CAREER: Marine Fungi and Carbon Processing in the Ocean

The ocean plays a major role in regulating Earth's climate by storing and recycling carbon, much of it through the activity of microscopic organisms. While bacteria have been extensively studied, marine fungi remain one of the least understood groups of ocean microbes. This project investigates how fungi help break down organic matter and recycle carbon in seawater. The research focuses on a newly discovered group of fungal enzymes that appear to be highly active in the ocean and may play an important role in marine food webs and carbon cycling. Using laboratory experiments, ocean expeditions, and modern genetic techniques, the project determines how marine fungi interact with bacteria and contribute to the movement of carbon through ocean ecosystems. This project also trains undergraduate and graduate students in laboratory, field and bioinformatic skills, and engages the public through partnerships with local outreach organizations and zoo-based education programs. Marine microorganisms regulate ocean chemistry through the production, transformation and remineralization of organic matter, yet the role of marine fungi in these processes remain poorly understood. Recent metatranscriptomic analyses revealed that fungal glycoside hydrolase family 7 (GH7) enzymes dominate expression of extracellular carbohydrate-active enzymes in the ocean, suggesting an unrecognized role for fungi in marine carbon cycling. However, the substrates, ecological functions, and biogeochemical significance of these enzymes remain unknown. This CAREER project addresses the central hypothesis that marine fungi are key degraders of complex polysaccharides and interact synergistically with bacteria to mediate carbon remineralization in the ocean Specific objectives are to (i) determine the substrates, biochemical properties and kinetics of representative oceanic GH7 enzymes, (ii) evaluate whether fungal and bacterial enzymes act synergistically during carbon processing using controlled co-culture experiments, and (iii) quantify fungal biomass, diversity, and contributions to carbon turnover through seasonal sampling campaigns across contrasting ocean regimes. By elucidating the molecular mechanisms and ecological significance of marine fungal activity, this work advances understanding of microbial interactions in ocean biogeochemistry and enables incorporation of fungal processes into predictive Earth system and carbon cycle models that affect marine resources. The integrated education plan combines laboratory instruction, ship-based field training and bioinformatics workshops to provide undergraduate and graduate students with hands-on experience in environmental microbiology, genomics, and quantitative data analysis. 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.