The fellowship began with the development of essential equipment - most notably a low-cost, optocoupler-based regulation system (OptoReg) that interfaces with widely available FireSting oxygen meters, effectively converting them into oxygen regulators. At approximately EUR 500 for a four-channel unit, compared with more than EUR 10,000 per channel for commercial systems, OptoReg removes a major financial barrier to multi-stressor climate research. Additional equipment included programmable temperature controllers, individual-chamber CTmax arenas, and behavioural arenas with remote monitoring capabilities. Using these systems, experimental work was conducted across three work packages. WP2 quantified the oxygen limit for thermal tolerance (PCTmax) across multiple oxygen levels, warming rates, and acclimation temperatures, revealing that PCTmax is not a fixed species property but depends critically on thermal exposure history and warming rate. WP3 established the Metabolic Niche Framework by combining measurements of standard metabolic rate, critical oxygen tension, incipient lethal oxygen saturation, and accumulated oxygen deficit with thermal tolerance assays, demonstrating that the anaerobic transition line – where aerobic metabolism becomes unsustainable – shifts systematically with acclimation temperature and warming rate. WP4 investigated behavioural-metabolic linkages using a sequential experimental design in which individual fish were first assessed for hypoxia-avoidance behaviour and subsequently transferred to respirometry, revealing that behavioural responses to progressive hypoxia correlate with metabolic traits underlying physiological hypoxia tolerance rather than baseline metabolic rate. During the fellowship, the fellow delivered teaching in four undergraduate courses: Animal Ecophysiology and Ecotoxicology (BI2025), Animal Structure and Function (BI1006), Human Anatomy and Physiology (BI2024), and Special Zoophysiology (BI3021), and served as course organiser for Special Zoophysiology and leader of the annual one-week field course for Animal Ecophysiology and Ecotoxicology. The fellow also served as main supervisor for one Erasmus master's student and co-supervisor for two PhD students. International collaborations were established through participation in two collaborative research expeditions at the Kristineberg Center for Marine Research and Innovation in Sweden. These expeditions brought together researchers from Canada, the United States, Australia, Denmark, Norway, and Sweden, resulting in co-authored publications in Methods in Ecology and Evolution and PLOS Biology, with additional manuscripts currently under review and in development. Research results have been disseminated through (1) first-authored and co-authored peer-reviewed publications in Conservation Physiology, Journal of Thermal Biology, Physiology, Methods in Ecology and Evolution, and PLOS Biology, with additional first-authored manuscripts from the fellowship's core datasets currently in preparation; (2) conference talks and posters at three consecutive Society for Experimental Biology annual meetings; (3) invited symposium presentations at Aarhus University; and (4) departmental seminars at NTNU. Public engagement has been achieved via social media and through research lectures and seminars delivered to students at NTNU. The OptoReg system has been adopted by several international laboratories.
