Postdoctoral Fellowship: PRFB: Characterizing Microeukaryotic Responses to Terrestrial Influence in Sediments Along a Continental Slope

This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2025. The fellowship supports research and training of the fellow that will contribute to biology in innovative ways. The marine subsurface biosphere is the least explored biome on Earth.

Studying microbes that live in this vast habitat enhances our understanding of global biogeochemical cycles and can support efforts to store excess carbon in seafloor sediment. Mounting evidence suggests eukaryotes are ecologically important in marine sediments, yet limited sampling of subseafloor eukaryotes has made it difficult to estimate their contributions to nutrient cycling and their potential to sequester sunken organic matter (OM) into the sediment.

Investigating these microbes is critical as the composition of subsurface sediment changes. Increasing terrestrial runoff is adding more land-derived OM to marine sediments, and microbes’ response to inputs of different origin may impact the global carbon cycle. To address these questions, the fellow will analyze microbial communities in sediment cores collected along a transect from the shallow Puerto Rico continental shelf to the depths of the Atlantic Ocean.

The results will provide critical data needed to identify which seafloor zones are most likely to permanently store sunken carbon. Undergraduate and high school students will be mentored throughout the project, and a new museum exhibit will be created to share these discoveries with the public at the Woods Hole Ocean Science Discovery Center.

The communities in ten sediment cores spanning all major oceanic water-depth zones (sublittoral, bathyal, abyssal and hadal) will be characterized down to 10 meters below the seafloor. The fellow will first determine the extent of terrestrial OM deposition along the Puerto Rico continental slope, quantifying its incorporation into marine sediments using carbon and nitrogen isotope measurements alongside radioanalytical total sedimentation rate analysis.

This dataset, combined with core depth and porewater nutrient data collected during coring, provides essential ecological context. DNA will then be extracted from sediment samples and marker gene sequencing, or metabarcoding, will be used to describe the subsurface eukaryotic community structure along this continental shelf gradient. Extracted RNA and metatranscriptomics will be used to examine eukaryotic activities, assessing their potential for carbon remineralization and contribution to global carbon cycling.

These results will address significant gaps in our knowledge of carbon distribution and cycling on Earth, and how these may change as OM inputs to marine sediment increase. Additionally, the project will provide the fellow with advanced training in bioinformatics and subsurface biology and geophysics, as well as hands-on teaching experience through hosting an on-site workshop and the publication of related methodological materials.

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.