Growth and physiological responses in largemouth bass populations to environmental warming: Effects of inhabiting chronically heated environments

• Published in: Journal of thermal biology 2020-02, Vol.88, p.102467-9, Article 102467
• Main Authors: White, Dalon P., Wahl, David H.
• Format: Article
• Language: English
• Subjects: Adaptation; Aerobic capacity; Bass; Climate change; Developmental plasticity; Food conversion; Growth; Growth rate; High temperature; Lakes; Largemouth bass; Metabolic rate; Metabolism; Micropterus salmoides; Phenotypic plasticity; Physiology; Ponds; Power plants; Temperature; Temperature effects; Temperature tolerance; Thermal tolerance
• ISSN: 0306-4565; 1879-0992
• DOI: 10.1016/j.jtherbio.2019.102467

Ectotherms are susceptible to increasing environmental temperatures associated with anthropogenic warming. Supra-optimum temperatures lead to declining aerobic capacity and can increase exposure to lethal temperatures, resulting in reduced performance. Although the capacity of phenotypic plasticity to minimize the effects of temperature on physiological processes is well studied, evidence of generational changes (e.g. transgenerational plasticity and rapid adaptation) in response to environmental warming is limited in natural populations. We investigated metabolism, growth, and thermal tolerance of largemouth bass (Micropterus salmoides) populations inhabiting thermally altered lakes (i.e. power plant cooling lakes) which have year-round elevated temperature regimes and exhibit supra-optimum temperatures on a yearly basis, and compared these traits with those in largemouth bass populations from ambient lakes. Largemouth bass from ambient and heated groups (n = 3 populations per group) were spawned in an ambient, common garden pond environment, then acclimated to either a normal summertime temperature (24 °C) or a supra-optimum temperature (30 °C). Fish from heated populations had significant reductions in the resting metabolic rate at both temperatures and markedly increased growth rates at 30 °C. By comparing pond-raised fish to fish removed directly from heated lakes, we showed that developmental plasticity played little role in establishing the metabolic rate. A lower resting metabolic rate contributed to an increase in the conversion efficiency of food to biomass of largemouth bass from heated lakes, regardless of temperature. Despite inhabiting heated lakes for many decades, neither critical thermal maximum nor minimum were altered in heated populations when raised in a common garden environment. These results suggest that largemouth bass can lessen sub-lethal effects of warming by altering physiological processes to reduce the impact of warming on aerobic scope and that these changes are generationally transient, but changes in maximum thermal tolerance in response to warming is limited to phenotypic plasticity. Once temperatures extend past the thermal optimum (Topt), physiological performance (e.g. growth) drops precipitously due to the relationship between ṀO2max and ṀO2rest. Due to the precipitous nature of the slope of the ṀO2max at supra-optimal temperatures, and if ṀO2max remains constant (e.g. Donelson et al., 2012; Sandblom et al., 2016), ev