Professor Pörtner is a leading scientist in the field of climate change research. His primary research interest is the effects of climate scenarios on the physiology of marine animals:
- Physiological and biochemical mechanisms limiting thermal tolerance and temperature dependent biogeography in invertebrates and fish. Cellular and whole animal energy budgets in various thermal regimes. Molecular mechanisms of thermal adaptation and limitation.
- The concept of oxygen and capacity limited thermal tolerance as a matrix integrating temperature, oxygen and CO2 effects on marine animals and ecosystems.
- Roles of climate oscillations in evolutionary history
Professor Pörtner has published more than 210 papers in peer reviewed journals. He is a Co-ordinating Lead Author of the Oceans chapter for IPCC AR5.
The concept of oxygen and capacity dependent thermal tolerance in aquatic ectotherms has successfully explained climate-induced effects of rising temperatures on species abundance in the field. Oxygen supply to tissues and the resulting aerobic performance characters thus form a primary link between organismal fitness and its role and functioning at ecosystem level. The thermal window of performance in water breathers matches their window of aerobic scope. Loss of performance reflects the earliest level of thermal stress, caused by insufficient functional capacity, the onset of hypoxemia and the progressive mismatch of oxygen supply and demand at the borders of the thermal envelope. The need to specialize on a limited temperature range results from temperature dependent trade-offs at several hierarchical levels, from molecular structure to whole organism functioning and may also support maximized energy efficiency. Various environmental factors like CO2 (ocean acidification) or hypoxia interact with these principal relationships. The conceptual analysis suggests that the relationships between energy turnover, the capacities of tissue and whole organism functions and activity and the width of thermal windows may lead to an integrative understanding of specialization on climate and, as a thermal matrix, of sensitivity to climate change and the factors involved. Such functional relationships might also relate to climate-induced changes in species interactions and thus, community responses at the ecosystem level.