PhD Candidate: Jessica Venetz

Defence date: 30-10-2024
Time: 14:30
Institute: Radboud Universiteit
Location: Aula, Comeniuslaan 2, Nijmegen
Online: Livestream

PhD supervisors:
prof. dr Mike Jetten
prof. dr. Caroline Slomp
dr. Annelies Veraart

Title thesis: Biogeochemical drivers of microbial methane removal in eutrophic coastal waters

Abstract:

Coastal ecosystems are biogeochemical hotspots for methane emissions. Ongoing eutrophication and warming will amplify deoxygenation which will lead to an imbalance between methane production and removal, and ultimately result in even higher methane emissions. Understanding water column methane removal is therefore crucial for mitigating water-air methane emissions. In this thesis we combined biogeochemistry and microbial ecology, to investigate the drivers for microbial methane removal in two eutrophic coastal ecosystems, the marine Lake Grevelingen (the Netherlands) and the Stockholm Archipelago (Sweden). Sediment-water and water-air methane fluxes were overall higher than expected and driven by eutrophication. We show that the aerobic gamma proteobacterial methanotrophic bacteria (γ-MOB) build a methane biofilter in the water column and that these can partially counteract the high sediment-water methane fluxes. We conclude that MOB-mediated methane removal is a major contributor to mitigating methane emissions in coastal waters and that the functional resilience of the MOB community is sustained by their genomic versatility. Moreover, the functioning of the methane biofilter is driven by an interplay of physical and chemical drivers and interactions with the microbial community. It is therefore important to consider such interactions and further investigate the system dynamics with an interdisciplinary approach.