Treeline displacement may affect lake dissolved organic matter processing at high latitudes and altitudes

• Published in: Nature Communications
• Main Authors: Catalán, Núria, Rofner, Carina, Verpoorter, Charles, Ruiz, M., Dittmar, Thorsten, Tranvik, Lars, Sommaruga, Ruben, Peter, Hannes
• Other Authors: European Commission, orcid:
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 2024
• Subjects: Dissolved organic matter (DOM); Ensure availability and sustainable management of water and sanitation for all; Responsible Consumption and Production; Take urgent action to combat climate change and its impacts; Alpine Lake; Hakala; Kalttopää; Kilpisjärvi; Subarctic
• Online Access: http://hdl.handle.net/10261/352583; https://doi.org/10.1038/s41467-024-46789-5; https://doi.org/10.13039/501100000780; https://api.elsevier.com/content/abstract/scopus_id/85188617774

Climate change induced shifts in treeline position, both towards higher altitudes and latitudes induce changes in soil organic matter. Eventually, soil organic matter is transported to alpine and subarctic lakes with yet unknown consequences for dissolved organic matter (DOM) diversity and processing. Here, we experimentally investigate the consequences of treeline shifts by amending subarctic and temperate alpine lake water with soil-derived DOM from above and below the treeline. We use ultra-high resolution mass spectrometry (FT-ICR MS) to track molecular DOM diversity (i.e., chemodiversity), estimate DOM decay and measure bacterial growth efficiency. In both lakes, soil-derived DOM from below the treeline increases lake DOM chemodiversity mainly through the enrichment with polyphenolic and highly unsaturated compounds. These compositional changes are associated with reductions in bulk and compound-level DOM reactivity and reduced bacterial growth efficiency. Our results suggest that treeline advancement has the potential to enrich a large number of lake ecosystems with less biodegradable DOM, affecting bacterial community function and potentially altering the biogeochemical cycling of carbon in lakes at high latitudes and altitudes. This research was supported by the European Union Seventh Framework Program [FP7/2007–2013] under grant no 262693 [INTERACT] to C.R. and the Austrian Science Fund (FWF) through project P-24098-B22 to MTP and RS. L.T. acknowledges funding from the Knut and Alice Wallenberg Foundation through grant 2018.0191 and from the Swedish Research Council through grant 2018-04524. N.C. acknowledges funding from the Wenner-Gren Foundation and is at present supported by the “Ramón y Cajal” fellowship RYC-2021-033714-I from the Ministry of Science and Innovation of Spain. We thank Antero Järvinen, Rauni Partanen, Oula Kalttopää, and Pirjo Hakala from Kilpisjärvi Biological Station for assistance with the experiment in Finland and Laurent Moya, Fabian Drewes, and Jolien Scholten for help during ...