An Empirical Test of Metabolic Effects and Adaptive Potential in Response to Global Ocean Warming in a Model Fish Species, the Threespine Stickleback

Abstract

Climate change has had a significant influence on the world's oceans, which have shown constant increases in mean water temperature over the last 50 years. The biota of Arctic environments, ectotherms in particular, may be particularly threatened by this change: whilst southern animals have the possibility of migrating north, those adapted to colder northern climes have nowhere left to move and may be faced with the ‘choice’ of adapt or die. A key factor in adaptation to the changing thermal environment is the physiological response. Metabolic scope (the difference between minimum and maximum oxygen consumption rate) is likely a key fitness related trait because it defines energy available for locomotion, growth and reproduction. The unifying aim of our research is to develop a deeper understanding of the constraints and/or adaptive potential in metabolic scope with respect to thermal changes predicted due to climate change.As obligate ectotherms, threespine stickleback (Gasterosteus aculeatus) populations adapted to localized thermal conditions provide an excellent and logistically tractable model for study of thermal and metabolic evolution in a changing environment. We collected broodstock from anadromous Barents Sea fish and bred them under controlled conditions for two generations to standardize environmental & maternal sources of variance. The multi‐generational pedigree and large numbers of families (N=180, 40 families) permits estimation of additive genetic variance, whereas repeated measurements in multiple environments allows us to estimate direct environmental variance on metabolism and swimming performance. Maximum and minimum metabolic rates, in addition to critical swimming performance, were measured with the same individuals at three different temperatures: (i) contemporary summer temperature for Barents Sea coastal waters (12°C), (ii) extreme predictions under global warming (17°C), and (iii) stressful temperature (80% of CTmax). Individual critical temperature in observed population varied between 27.2 and 32.1°C. The preliminary results showed that minimum and maximum metabolic rates increased with the temperature rise: 61.6 ± 10.1 and 126.2 ± 36.1 mg O2/kg/hour at 12°C; 70.19 ± 11.8 and 144.9 ± 38.8 mg O2/kg/hour at 17°C; 114.0 ± 15.7 and 183.7 ± 32.0 mg O2/kg/hour at individual stressful temperature, respectively. However, the highest aerobic metabolic scope and swimming performance were observed at 17°C. Quantitative genetic analyses are ongoing, but point to the broad potential for adaptation to environmental change.Support or Funding InformationSM: Alfred Cordelin Foundation, Otto A. Malm Foundation, Oscar Öflund Foundation, LUOVA doctoral programme; RJSM, JM, TM: Academy of Finland