Within-Generation and Transgenerational Plasticity of a Temperate Salmonid in Response to Thermal Acclimation and Acute Temperature Stress.

AbstractThe rise in temperature associated with climate change may threaten the persistence of stenothermal organisms with limited capacities for beneficial thermal acclimation. We investigated the capacity for within-generation and transgenerational thermal responses in brook trout (Salvelinus fontinalis), a cold-adapted salmonid. Adult fish were acclimated to temperatures within (10°C) and above (21°C) their thermal optimum for 6 mo before spawning, then mated in a full factorial breeding design to produce offspring from cold- and warm-acclimated parents and bidirectional crosses between parents from both temperature treatments. Offspring from families were subdivided and reared at two acclimation temperatures representing their current (15°C) and anticipated future (19°C) habitat temperatures. Offspring thermal physiology was measured as the rate of oxygen consumption (Mo₂) during an acute change in temperature (increase of 2°C h^-1) to observe their Mo₂-temperature relationship. We recorded resting Mo₂, peak (highest achieved, thermally induced) Mo₂, and critical thermal maximum (CTM) as performance metrics. Although limited, within-generation plasticity was greater than transgenerational plasticity, with offspring warm acclimation elevating CTM by 0.5°C but slightly lowering peak thermally induced Mo₂. Transgenerational plasticity was evident as a slightly elevated resting Mo₂ and a shift of the Mo₂-temperature relationship to higher rates overall in offspring from warm-acclimated parents. Furthermore, offspring whose parents were warm acclimated were in worse condition than those whose parents were cold acclimated. Both parents contributed to offspring thermal responses; however, the paternal effect was stronger. Despite the existence of within-generation and transgenerational plasticity in brook trout, it is unlikely that these will be sufficient for coping with long-term changes to environmental temperatures.