GPS Seminars & Events

Nitrite is a fleeting but revealing chemical intermediate that traces the balance between microbial production and consumption of nitrogen within the ocean's oxygen-deficient zones and the productive sunlit layer. Using newly reanalyzed UV-spectral data from the global Biogeochemical-Argo (BGC-Argo) float array, we can now observe nitrite - and maybe thiosulfate, an intermediate of the sulfur cycle that emerges when oxygen is absent - across vast regions and seasons, revealing signals previously invisible to scientists. This talk will take a world tour through these nitrite seascapes, from the Eastern Tropical Pacific to the Arabian Sea and the productive Equator, showing how nitrite dynamics expose microbial regime imbalances, the coupling between nitrogen and carbon cycles, and links to mesoscale physical features. I will conclude with perspectives on next-generation strategies and approaches that can extend this new chemical vision globally, offering a path toward real-time observation of the ocean's invisible biogeochemical transformations.

Nitrite is a fleeting but revealing chemical intermediate that traces the balance between microbial production and consumption of nitrogen within the ocean's oxygen-deficient zones and the productive sunlit layer. Using newly reanalyzed UV-spectral data from the global Biogeochemical-Argo (BGC-Argo) float array, we can now observe nitrite - and maybe thiosulfate, an intermediate of the sulfur cycle that emerges when oxygen is absent - across vast regions and seasons, revealing signals previously invisible to scientists. This talk will take a world tour through these nitrite seascapes, from the Eastern Tropical Pacific to the Arabian Sea and the productive Equator, showing how nitrite dynamics expose microbial regime imbalances, the coupling between nitrogen and carbon cycles, and links to mesoscale physical features. I will conclude with perspectives on next-generation strategies and approaches that can extend this new chemical vision globally, offering a path toward real-time observation of the ocean's invisible biogeochemical transformations.

Aerobic methanotrophy has evolved in the biosphere more than once.  Studies of aerobic methanotrophy have focused on two proteins: particulate methane monooxygenase (pMMO) and soluble methane monooxygenase (sMMO). Laboratory experiments and natural mesocosms, however, indicate that a broader range of proteins is capable of oxidizing methane and other small hydrocarbons in the environment, even at low substrate concentrations. Across a series of field expeditions in Alaska and California, we have measured methane gas fluxes in a variety of landscapes, including rivers, permafrost, desert, oak woodland, and arid rangeland. These environments encompass a wide range of temperature (subzero to > 40 ºC), moisture, and methane concentration conditions. Alaska riverine methane concentrations are substantial, in some cases surpassing deep sea methane concentrations near methane seeps. Across this variety of landscapes and conditions, we observe significant soil methanotrophy—even at and below atmospheric concentrations of methane (ca. 2 ppm). Using amplicon-based soil and water microbial community composition, metagenomic analyses, and laboratory experiments, we provide new insights into the range of metalloproteins that may be able to accomplish methanotrophy across a wide variety of environments.