Impact of Marine Fungi on Global Biogeochemical Cycling of C and N

Award Period
Award Amount
Agency Name
Simons Foundation
Award Number
PI First Name
PI Last Name
David Valentine
Area/s of Research
Ecology and Evolution

Fungi have been long overlooked as a player in the biogeochemical cycling of carbon and nitrogen in marine environments. Compared to their terrestrial counterparts, marine fungi are vastly understudied partly due to the bias of research interests, and partly because of their cell biology and feeding strategies. As osmotrophs, fungi feed by secreting extracellular enzymes into the environment to depolymerize food substrates before transporting the digested monomers and nutrients back into the cell for growth. As major decomposers of a wide range of complex carbon substrates such as cellulose, hemicellulose, and lignin, fungi produce carbon dioxide, volatile fatty acids, and under anoxia, potentially hydrogen. Recent evidence has suggested that fungi in marine sediments could be responsible for a significant portion of denitrification and nitrous oxide (N2O) production. Moreover, fungi’s ability to degrade large particles in the water column, along with their spore-forming life cycles, provides them a special position in the microbial food web, which remineralizes organic matter in the mixed layer and reduces particle export.

However, most of our knowledge describing marine fungi’s ecological roles remains qualitative. Research on marine fungi in the past decade has focused on their diversity. Little is known about the marine fungi’s activity and their quantitative contribution to geochemical cycles of carbon (C) and nitrogen (N). I propose to work in David Valentine and Michelle O’Malley’s laboratories at UC Santa Barbara to determine the fungal activity in organic matter degradation and N2O production in coastal and estuarine sediments in Santa Barbara, coastal waters off Santa Barbara, and on a research cruise to the eastern tropical North Pacific oxygen minimum zone (Chief Scientist: Bess Ward). Next-generation sequencing will be used to link fungal abundance and diversity to their activities. Additional incubations will be performed to examine the influence of elevated nutrient input and temperature (individually) on the contribution of fungal biomass degradation and denitrification.

This project will contribute to elucidating the potentially significant role marine fungi play in the global biogeochemical cycling of C and N.