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Microbes mediate the flow of energy and matter through the Earth system. In the ocean, diverse microbial communities repartition key elements (and their isotopes) among different chemical phases, altering the fate and fluxes of this material. In so doing, these tiny wonders profoundly influence Earth’s geochemical cycles and climate, shaping planetary habitability.
My research group, the Rutgers Marine Biogeochemistry Lab (RUMBL), investigates feedbacks between ocean chemistry and microbial metabolism that affect Earth system stability. Our work focuses on
(1) how microbes reshape nutrient landscapes in response to (climate-driven) shifts in ocean chemistry/physics (biogeochemical feedbacks), and
(2) how these changes affect distribution of carbon in Earth’s reservoirs (climate feedbacks).
Wedding field-based observations, laboratory experiments, and computational methods, our analytical toolkit includes elemental and stable isotope analyses (nitrogen, carbon, and bioactive transition metals) and ‘omics approaches.
Current projects include:
Does ocean warming reduce iron demand in Southern Ocean phytoplankton? The Southern Ocean is a major sink for atmospheric carbon due to biologically-mediated export (Huang et al. 2023 PNAS). Following observations made on the HMS Discovery in Dec 2023-Jan 2024 (Selden et al., in prep.), this project investigates the hypothesis that, by increasing the efficiency of key iron-containing enzymes (e.g., in photosynthesis and nitrogen acquisition pathways), warming will increase iron use efficiency of iron-limited and cold-adapted phytoplankton, with important consequences for the Southern Ocean biological carbon pump. Preliminary results presented by summer REU students Dylan Buchmiller (TAMU-G) and Karina Lai (UW) at Ocean Sciences Meeting, February 2026.
How will climate-driven shifts in regional circulation alter diffusive mixing and new nitrogen supply/utilization in the tropical Atlantic Ocean? The availability of nitrogen limits ecosystem productivity across vast swaths of the surface ocean, constraining potential carbon export and thus CO2 exchange between the atmosphere and deep sea. In collaboration with Dr. Joe Gradone (Rutgers), this project will investigate: (1) the relationship between basin-scale changes in salinity and the occurrence of salt fingering, a diffusive process which drives water mass mixing more efficiently than mechanical turbulence, (2) the contribution of nitrate fluxes driven by salt fingering to nitrogen supply and “new” primary production, and (3) its impact on upper ocean ecosystem structure. Field campaign supported by grant from the Schmidt Ocean Institute and scheduled for August 2026.
Can new AI tools to predict protein structure from sequence elucidate metal requirements and chemical form in marine phytoplankton? Most metabolic processes are driven by enzymes which contain metal co-factors, meaning that the availability of key metals (e.g., iron, zinc, copper) to a microbial community affects its biogeochemical and ecological function. However, directly assessing metal demand, quotas, and chemical speciation in marine environments is analytically challenging and expensive. In collaboration with Drs. Nathan Yee and John Reinfelder (Rutgers) and Dr. Bhoopesh Mishra (IIT), this project aims to use cutting edge artificial intelligence (AI)-powered tools to predict the occurrence and structure of protein metal-binding sites from ‘omics data, and will test the utility of these tools in phytoplankton cultures against state-of-the-art spectroscopy measurements. Funded by NSF-EAR-GG grant starting September 2025.
I AM CURRENTLY RECRUITING STUDENTS! Please reach out to me by e-mail (crselden@marine.rutgers.edu) if you are interested in discussing opportunities with RUMBL.