[ESAC Seminar] Nene Putzi

“Marine Snow as Hotspots of Greenhouse Gas Emissions in the Eastern Tropical South Pacific”

Using functional profiling of free-living and particle-associated microbial communities, we investigated pathways of aerobic and anaerobic respiration, with emphasis on nitrogen cycling and greenhouse gas production. Free-living communities exhibited sharp oxygen-gradient–linked shifts in high-affinity oxidases and enrichment of canonical denitrification genes in ODZs, yet generally lacked complete denitrification pathways, suggesting limited potential for nitrous oxide (N₂O) release. In contrast, particle-associated communities within sinking marine snow displayed coherent patterns of all four canonical denitrification genes across most depths, creating conditions favourable for pathway completion. However, as particles degrade, they lose the ability to retain high concentrations of intermediate metabolites, leading to increasingly incomplete denitrification and the release of N₂O—a potent greenhouse gas—into the water column and eventually the atmosphere. Additional pathways, including DNRA, anammox, sulfate reduction, and metal reduction, contributed variably but were generally less relevant for climate-active gases. Methanogenesis was ecologically insignificant. Together, these findings highlight the critical role of marine snow-associated microbial communities in shaping nitrogen transformations and greenhouse gas fluxes in the ETSP, underscoring their importance in regulating ocean–climate interactions.

ESAC Early-Career Seminar Series —

A forum for students and postdocs to share recent research, hone presentation skills, and build community among peers, sponsored by the EAPS Student Advisory Committee. Open to current EAPS graduate and undergraduate students and postdocs. Typically hosted on Thursdays during the semester, including pizza lunch.

Contact: esac.officers@gmail.com