SMAST Seminar - "Life on Marine Snow – How Microbial Ecosystems Drive Carbon and Nitrogen Cycling" by: Clarissa Karthauser

Wednesday, January 28, 2026 at 12:30pm to 1:30pm

Department of Estuarine and Ocean Sciences

"Life on Marine Snow – How Microbial Ecosystems Drive Carbon and Nitrogen Cycling"
Clarissa Karthauser
Postdoctoral Investigator, WHOI

Wednesday, January 28, 2026
12:30 - 1:30 pm
SMAST E 101-103 and via Zoom

Abstract:

Diverse organic particles are hotspots of biological activity within the ocean. The most common marine particle type, marine snow, can form from dead and living biological material and embed abiotic components such as dust grains and plastics. Marine animals produce fecal pellets, another common and more compact organic particle type. In an otherwise homogeneous water mass, particles provide microbes with steep chemical gradients and platforms for ecological interactions that drive key processes on the micro-scale, affecting large-scale element cycling. If included in water samples, particle-associated communities act differently than while sinking or floating in the water column. If combined on a filter, their uniqueness and heterogeneity merges into a muddy mass. As they sink through the ocean from top to bottom, particles provide links between different water layers and nourishment to organisms below the productive surface ocean. Studying and treating particles as small ecosystems with their own unique properties is key in understanding their role in microbiology and biogeochemistry. To do this, I adapted a set of methods to the requirements of small, fragile, and highly heterogeneous samples. During this presentation, I will share two discoveries I made by incubating individual particles aerobically and anaerobically, combined with genetic, microscopic, and chemical analyses. Aerobic experiments revealed how fecal pellet packaging limits microbial respiration, while my anaerobic experiments showed that denitrification was carried out by microbial consortia on particles, in contrast to anammox, which was carried out by free-living microbes.

Join Meeting
https://umassd.zoom.us/j/97440069270
Meeting ID and passcode required. Please email Callie Rumbut for more information

SMAST East 101-103 : 836 S. Rodney French Boulevard, New Bedford MA 02744
Callie Rumbut
c.rumbut@umassd.edu
https://umassd.zoom.us/j/97440069270