Journal Article

Climate warming will test the limits of thermal plasticity in rainbow trout, a globally distributed fish

Lima, Lais, Metzger, David C H, Schulte, Patricia M, Farrell, Anthony P, Strowbridge, Nicholas, Gilbert, Matthew J H, Zhang, Yangfan, McKenzie, Jessica L, Fangue, Nann A

2025

Overview

Abstract Phenotypic plasticity is thought to be critical in allowing organisms to cope with environmental change, but the factors that limit this plasticity are poorly understood, which hampers predictions of species resilience to anthropogenic climate change. Here, we ask if limited plasticity in key traits constrains performance at high temperatures, using two California hatchery strains of rainbow trout (Oncorhynchus mykiss). Aerobic and anaerobic metabolic performance declined at a high but ecologically relevant acclimation temperature (24°C), suggesting performance cannot be maintained at this temperature, despite acclimation. Similarly, while both whole-organism thermal tolerance and hypoxia tolerance improved with acclimation to moderately elevated temperatures, compensation was limited at the highest acclimation temperature. These limits at the whole-organism level were aligned with limits at lower levels of biological organization. At the organ level, absolute scope to increase heart rate with acute warming (ΔƒHmax) did not increase between the upper two acclimation temperatures, and the safety margin for cardiac performance decreased at the highest acclimation temperature. At the cellular level, at 24°C, there were transcriptomic changes in the heart consistent with a cellular stress response. These limits across multiple levels of biological organization were observed under conditions that are ecologically relevant at the southern end of the species range, which suggests that thermal plasticity is likely insufficient to buffer rainbow trout against even modest anthropogenic warming in these regions. Lay Summary Understanding the boundaries of acclimation capacity in response to increased temperature can provide valuable insights into conservation and management. In rainbow trout, we show that acclimation limits occur at ecologically relevant temperatures and are aligned with thermal limits across molecular, physiological and whole-animal phenotypes.

• Publisher: Oxford University Press
• Subject: Acclimation / Acclimatization / Cellular stress response / Climate change / Environmental changes / Global warming / Heart rate / High temperature / Hypoxia / Oncorhynchus mykiss / Organisms / Phenotypes / Phenotypic plasticity / Plastic properties / Plasticity / Safety margins / Salmon / Temperature / Temperature tolerance / Thermal stress / Transcriptomics / Trout