Long‐term forecast of thermal mortality with climate warming in riverine amphipods

• Published in: Global change biology 2023-09, Vol.29 (17), p.5033-5043
• Main Authors: Verberk, Wilco C. E. P., Hoefnagel, K. Natan, Peralta‐Maraver, Ignacio, Floury, Mathieu, Rezende, Enrico L.
• Format: Article
• Language: English
• Subjects: Acclimation; Acclimatization; Amphipoda; Amphipoda - physiology; Animal biology; Aquatic crustaceans; Aquatic Organisms - physiology; Bioclimatology; Climate Change; climate vulnerability; Critical temperature; Ecological effects; Ecology, environment; Environmental Monitoring; Environmental stress; Frameworks; Global Warming; Heat; Heat stress; Heat tolerance; Heat-Shock Response; Hypoxia; Invertebrate Zoology; Life Sciences; Mortality; Mortality risk; Netherlands; Oxygen; oxygen limitation; Oxygenation; Physiological effects; Probability theory; Rivers; Scaling; Temperature; Temperature effects; Temperature tolerance; thermal biology; thermal safety margin; water quality; Weather forecasting
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.16834

Forecasting long‐term consequences of global warming requires knowledge on thermal mortality and how heat stress interacts with other environmental stressors on different timescales. Here, we describe a flexible analytical framework to forecast mortality risks by combining laboratory measurements on tolerance and field temperature records. Our framework incorporates physiological acclimation effects, temporal scale differences and the ecological reality of fluctuations in temperature, and other factors such as oxygen. As a proof of concept, we investigated the heat tolerance of amphipods Dikerogammarus villosus and Echinogammarus trichiatus in the river Waal, the Netherlands. These organisms were acclimated to different temperatures and oxygen levels. By integrating experimental data with high‐resolution field data, we derived the daily heat mortality probabilities for each species under different oxygen levels, considering current temperatures as well as 1 and 2°C warming scenarios. By expressing heat stress as a mortality probability rather than a upper critical temperature, these can be used to calculate cumulative annual mortality, allowing the scaling up from individuals to populations. Our findings indicate a substantial increase in annual mortality over the coming decades, driven by projected increases in summer temperatures. Thermal acclimation and adequate oxygenation improved heat tolerance and their effects were magnified on longer timescales. Consequently, acclimation effects appear to be more effective than previously recognized and crucial for persistence under current temperatures. However, even in the best‐case scenario, mortality of D. villosus is expected to approach 100% by 2100, while E. trichiatus appears to be less vulnerable with mortality increasing to 60%. Similarly, mortality risks vary spatially: In southern, warmer rivers, riverine animals will need to shift from the main channel toward the cooler head waters to avoid thermal mortality. Overall, this framework generates high‐resolution forecasts on how rising temperatures, in combination with other environmental stressors such as hypoxia, impact ecological communities. We describe a flexible analytical framework to forecast heat mortality in riverine amphipods, incorporating physiological acclimation, temporal scale and differences in water oxygenation. We bridge the gap between experimental data and the ecological reality of thermal fluctuations by expressing heat tolerance as