Ocean alkalinity enhancement impacts particulate organic matter degradation and the microbial community composition
durch
8A-002 - Hörsaal Ostufer / Lecture Hall East
GEOMAR - Standort Ostufer / GEOMAR - East Shore
Abstract
Ocean Alkalinity Enhancement (OAE) is gaining attention as a promising marine carbon dioxide removal strategy. However, its potential biogeochemical side effects remain poorly understood. Here we present results from a mesocosm experiment conducted in Bergen, Norway, where we tested the effects of a gradient-based alkalinity enhancement (ΔTA 0–600 µmol/kg) simulating calcium- and silicate-based mineral addition. Over a 51-day period, we monitored microbial community dynamics via 16S rRNA gene amplicon sequencing and tracked biogeochemical changes, including particulate organic matter (POM) stoichiometry differences between water column and sediment trap. Using GLMMs within a Bayesian framework, we detected significant shifts in microbial community composition across the alkalinity gradient, with taxa-specific responses to both ΔTA and mineral type. These shifts coincided with decreased preferential N-consumption with increasing ΔTA. Our results suggest that OAE may modulate microbial ecosystem functions in ways that could feedback on the ocean carbon cycle-highlighting the need for microbial considerations in the risk assessment of marine CDR strategies.
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