[All-postdocs] Bioseminar CLARK 507 Clarissa Karthauser

[Ana M Velez]

Woods Hole Oceanographic Institution
Biology Department Seminar - Clark 507

Thursday, April 28, 2022 - 12:00 Noon

Clarissa Karthauser
Postdoctoral Scholar, WHOI

Microbial Carbon and Nitrogen Cycling Associated with Marine Snow Particles
Sinking marine snow particles provide an essential link between carbon and nitrogen fixation in the sunlit surface waters and remineralization and nitrogen (N)-loss in the deeper water layers. Particles both regulate and introduce variability to these processes as they provide a micro-environment with steep chemical gradients and unique microbial communities that differ from the surrounding water column. Therefore, it is necessary to study carbon and nutrient cycling and the responsible microbial communities on the scale of single particles. During my PhD studies at MPI Bremen, I studied how sinking particles affect the two dominant N-loss processes, i.e., anammox and denitrification, in marine oxygen minimum zones (OMZs). The aim of my project was to quantify potential N-loss rates in individual particles, characterize the responsible microbial communities and test which properties of the sinking particles control N-loss in the Peruvian OMZ. An exciting outcome was that the two processes occur in different spatial patterns. While denitrification was directly associated with the particles, which provided organic substrates and a platform for the diverse denitrifying microbial consortia, anammox mainly occurred in the water surrounding the particles. However, particles were an important source of ammonium driving anammox and their abundance could therefore be used as a predictor of anammox rates. Single particle incubations enabled me to understand these microbial interactions with particles and apply them to large-scale estimates, which encouraged me to continue working at the scale of single particles for my postdoc. I recently joined the Ocean Twilight Zone project, where it is my aim to study the microbial contribution to remineralization on particles in the mesopelagic and link these measurements to carbon flux and attenuation estimates on larger temporal and spatial scales.

In person: Clark 507
Zoom: https://whoi-edu.zoom.us/j/96832080171 Meeting ID: 968 3208 0171
By dial: Find your local number: https://whoi-edu.zoom.us/u/ablHoKtbkc
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