Physiological Differences in Largemouth Bass Populations from Thermally Influenced Powerplant Cooling Reservoirs Suggest Rapid Adaptation to Increased Thermal Regimes

Creating large-scale, replicated model systems that allow building predictive models of the effects of climate change on organisms is difficult. To this end, we used artificially heated power plant cooling lakes that have been established for 4-5 decades as a model system for increased temperature effects in aquatic ecosystems. Temperature increases in these systems are similar to those predicted by global climate change models by the year 2100. Adult largemouth bass (Micropterus salmoides) from multiple powerplant cooling reservoirs and ambient reservoirs were bred in a common pond environment and growth, metabolism, and temperature tolerance was assessed in a laboratory setting. Results show clearly enhanced growth rates in the powerplant-based population, especially at temperatures higher than those seen in the ambient reservoirs. Results also suggest decreased resting metabolic rate, which couples well with increased growth. There was not an effect on maximum temperature tolerance, though there was a significant effect on minimum temperature tolerance between the populations. These results suggest that within a 50 year time frame, largemouth bass can adapt to cope with a strongly increased temperature regime similar to those predicted by global climate change models.