Freshwater ecosystems, ponds, ditches, lakes and wetlands, are hotspots for methane emissions, a greenhouse gas far more potent than CO₂ in the short term. Yet we still poorly understand what drives the enormous variability in how much methane these systems emit. This thesis investigates the role of bioturbators: organisms that live in or interact with sediments and physically or chemically alter them. These include rooted-in-sediment aquatic plants, small invertebrates such as worms, and invasive species like the red swamp crayfish. Through controlled laboratory and mesocosm experiments, combined with a systematic literature review, this thesis shows that bioturbators can both increase and decrease methane emissions, and that the outcome depends critically on the organism's traits, the intensity of disturbance, and the environmental context. Rooted macrophytes were found to reduce sediment methane storage, while the invasive crayfish Procambarus clarkii boosted emissions by destroying vegetation and resuspending sediments. These findings highlight that the biological drivers of greenhouse gas emissions from freshwaters are context-dependent, and that ignoring them risks systematic errors in carbon budget estimates.
Lucía Cabrera-Lamanna was born in 1992 in Montevideo, Uruguay. She obtained her Bachelor's degree in Biological Sciences and her Master's degree in Geosciences from Universidad de la República and CURE (Uruguay), respectively. Her Master's research focused on riparian vegetation as a nature-based solution to mitigate nutrient runoff from agriculture into freshwater ecosystems. She subsequently worked in Turkey on ecological monitoring of small water bodies and salinisation impacts on shallow lakes. In 2022, she moved to the Netherlands to pursue her PhD at the Department of Ecology, Radboud University, under the supervision of Prof. Sarian Kosten. Her doctoral research examined the biological drivers of greenhouse gas emissions from freshwater ecosystems, with a focus on bioturbation and methane dynamics. Her research interests span freshwater ecology, biogeochemistry, and the role of inland waters in the global carbon cycle.