Meeting Abstract

S9-2.1  Monday, Jan. 7  How oxygen and temperature changes across latitude and elevation determine ecological distribution patterns VERBERK, W.C.E.P.*; BILTON, D.T.; CALOSI, P.; SPICER, J.I.; Radboud University Nijmegen, The Netherlands; Plymouth University, UK; Plymouth University, UK; Plymouth University, UK wilco@aquaticecology.nl

Oxygen may set thermal tolerance limits. Such oxygen limitation arises when an individual’s capacity to supply oxygen to its tissues is insufficient to meet mitochondrial oxygen demand. Understanding the role of oxygen in limiting aquatic ectotherms is complex: temperature affects both oxygen demand and the availability of oxygen. We derived an index of oxygen supply (IOS) from first principles of gas diffusion, which incorporated both partial pressure and solubility and tested its ability to explain published patterns in body size and species richness across environmental clines linked to differences in both oxygen partial pressure (e.g. altitude) or oxygen solubility (e.g. salinity). We also experimentally tested wether thermal maxima of aquatic insects arise from a mismatch between oxygen supply and demand. Our IOS better explained patterns in biodiversity and body size than either solubility or partial pressure alone, thus resolving the question whether partial pressure or solubility limits oxygen supply in nature. Intriguingly, by returning to the first principles of gas diffusion, it became clear that more oxygen is actually available in warmer waters, counter to current wisdom. The experiment support oxygen limitation at thermal extremes: hypoxia lowered thermal maxima, whilst hyperoxia increased them. At the same time, individuals that strongly increased oxygen uptake at elevated temperatures had lower thermal maxima. Our discovery that oxygen supply is actually higher in warmer habitats, represents a significant shift in our understanding of how oxygen shapes aquatic communities and has major implications for our understanding of how thermal limits may arise, and our ability to predict the impacts of climate change.