Aquatic biota responses to temperature in a high Andean geothermal stream

• Published in: Freshwater Biology
• Main Authors: Quenta‐herrera, Estefania, Daza, Antonio, Lazzaro, Xavier, Jacobsen, Dean, Dangles, Olivier, Cauvy‐fraunié, Sophie
• Other Authors: RiverLy - Fonctionnement des hydrosystèmes (RiverLy), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: geothermal streams; temperature; thresholds; tropical Andes; aquatic organisms; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Arctic; Global warming
• Online Access: https://hal.science/hal-03560268; https://doi.org/10.1111/fwb.13798

International audience The impact of global warming on mountain ecosystems is predicted to be high, and particularly in the tropical region. Geothermal streams have provided comprehensive evidence about how aquatic biodiversity changes across natural thermal gradients, but current knowledge is restricted to arctic and temperate zones. Thermal tolerances are different in tropical biological communities, resulting in high thermal sensitivity and low capacity to endure change in their thermal environments. This feature can change the response of aquatic organisms to warming, yet there is little empirical evidence to support this assumption. In this study, we address this issue by evaluating how water temperature affects biodiversity, and the structure of primary and secondary producers of a high-elevation geothermal stream system (4,500 m above sea level) in the Bolivian Andes. We analysed multi-taxa responses to increased water temperature using benthic macroinvertebrate families, benthic algae and cyanobacteria, fishes, and macrophytes as study organisms. Different models were run to assess the response of aquatic biota to temperature. In addition, threshold indicator taxa analysis was used to identify changes in macroinvertebrate taxa distributions along the thermal gradient. We found that macroinvertebrate richness decreased at 24-25 degrees C due to the different taxon-specific responses to temperature. Threshold indicator taxa analysis identified 17 temperature thresholds for each family of macroinvertebrates. Changes in macroinvertebrate community composition were significantly associated with changes in water temperature. Similarly, changes in macrophytes were associated with temperature differences, and high macrophyte richness was found at 19-20 degrees C. Chlorophyll-a concentration of green algae and diatoms was higher at intermediate temperatures 20-22 degrees C, macroinvertebrates density peaked at 27 degrees C, and fish body size reduced linearly with temperature. Temperature increase in the ...