TY - JOUR

T1 - Aquatic biota responses to temperature in a high Andean geothermal stream

AU - Quenta-Herrera, Estefania

AU - Daza, Antonio

AU - Lazzaro, Xavier

AU - Jacobsen, Dean

AU - Dangles, Olivier

AU - Cauvy-Fraunié, Sophie

N1 - Funding Information: We thank Belinda Robson, Andy Green and three anonymous reviewers for their helpful corrections and suggestions on a previous version of the manuscript. We thank Jorge Molina for assistance with the field work. This work was funded by the Fond Français pour l'Environnement Mondial (FFEM) and the Fondation pour la Recherche sur la Biodiversité (FRB) (Modeling biodiversity and land use interactions under changing glacial water availability in tropical high Andean wetlands‐ BIOTHAW, AAP‐SCEN‐2011‐II). Publisher Copyright: © 2021 John Wiley & Sons Ltd.

PY - 2021

Y1 - 2021

N2 - 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°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°C. Chlorophyll-a concentration of green algae and diatoms was higher at intermediate temperatures 20–22°C, macroinvertebrates density peaked at 27°C, and fish body size reduced linearly with temperature. Temperature increase in the geothermal stream resulted in a reduction of aquatic diversity and primary and secondary producers by simplifying the community structure to a few warm-adapted taxa and reduced body size. These patterns differed from those obtained in temperate/arctic geothermal streams, but are similar to other studies at high-elevation. In a context of increasing warming, the ecological structure of high-elevation streams might lose cold-adapted taxa, and change to smaller populations. Additional studies based on ecosystem functioning of geothermal streams could lead to a better understanding on how warming affects high-elevation streams.

AB - 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°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°C. Chlorophyll-a concentration of green algae and diatoms was higher at intermediate temperatures 20–22°C, macroinvertebrates density peaked at 27°C, and fish body size reduced linearly with temperature. Temperature increase in the geothermal stream resulted in a reduction of aquatic diversity and primary and secondary producers by simplifying the community structure to a few warm-adapted taxa and reduced body size. These patterns differed from those obtained in temperate/arctic geothermal streams, but are similar to other studies at high-elevation. In a context of increasing warming, the ecological structure of high-elevation streams might lose cold-adapted taxa, and change to smaller populations. Additional studies based on ecosystem functioning of geothermal streams could lead to a better understanding on how warming affects high-elevation streams.

KW - aquatic organisms

KW - geothermal streams

KW - temperature

KW - thresholds

KW - tropical Andes

U2 - 10.1111/fwb.13798

DO - 10.1111/fwb.13798

M3 - Journal article

AN - SCOPUS:85111067573

VL - 66

SP - 1889

EP - 1900

JO - Freshwater Biology

JF - Freshwater Biology

SN - 0046-5070

IS - 10

ER -