Climate change is altering the structure and functioning of river ecosystems worldwide. In mountain rivers, glacier retreat has been shown to result in systematic changes in aquatic invertebrate biodiversity, but the effects of ice loss on other biological taxa and on whole-ecosystem functions are less well understood. Using data from mountain rivers spanning six countries on four continents, we show that decreasing glacier cover leads to consistent fungal-driven increases in the decomposition rate of cellulose, the world’s most abundant organic polymer. Cellulose decomposition rates were associated with greater abundance of aquatic fungi and the fungal cellulose-degrading Cellobiohydrolase I (cbhI) gene, illustrating the potential for predicting ecosystem-level functions from gene-level data. Clear associations between fungal genes, populations and communities and ecosystem functioning in mountain rivers indicate that ongoing global decreases in glacier cover can be expected to change vital ecosystem functions, including carbon cycle processes.
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This research was funded by a Natural Environment Research Council Scholarship (no. NE/L002574/1) awarded to S.C.F. Additional financial support for laboratory overheads was provided to S.C.F. by the River Basin Processes and Management Cluster, School of Geography, University of Leeds. S.C.F., L.E.B. and J.L.C. received funding from INTERACT under the European Union H2020 (GLAC-REF, grant agreement no. 730938, Transnational Access) for fieldwork in Finse, Norway. Fieldwork in Ecuador was funded by the Pontifical Catholic University of Ecuador under project no. M13434 (PUCE 2016-2017). A.J.D. and K.C.R. were supported by a Natural Environment Research Council grant (no. NE/M02086X/1), and E.H. was funded by the Alaska Climate Adaptation Science Center. We thank L. Füreder (Austria); the Ecuadorian Ministry of the Environment (research permit no. MAE-DNM-2015-0030), the Reserva Ecológica Antisana, Public Metropolitan Company of Potable Water and Sanitation of Quito (EPMAPS) and Water Projection Fund (FONAG) (Ecuador); the Parc National de la Vanoise (France); the Department of Conservation (New Zealand); and U. Fjellstyre and T. Buttingsrud (Norway) for permission to access field sites and work within protected areas. We also thank the Finse Alpine Research Centre, Obergurgl Alpine Research Centre and the Design School of the University of Leeds for the use of their field and laboratory facilities, and N. Friberg for his hospitality. For their assistance and support in the field, we thank P. Andino, R. Espinosa, P. Rosero and J. Sutherland, and S.C.F. gives special thanks to C. Fell and N. Fell.
The authors declare no competing interests.
Peer review information Nature Climate Change thanks Luz Boyero and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Fell, S.C., Carrivick, J.L., Cauvy-Fraunié, S. et al. Fungal decomposition of river organic matter accelerated by decreasing glacier cover. Nat. Clim. Chang. 11, 349–353 (2021). https://doi.org/10.1038/s41558-021-01004-x