Shifting stoichiometry: Long‐term trends in stream‐dissolved organic matter reveal altered C:N ratios due to history of atmospheric acid deposition. (5th November 2021)

• Record Type: Journal Article
• Authors: Rodríguez‐Cardona, Bianca M.; Wymore, Adam S.; Argerich, Alba; Barnes, Rebecca T.; Bernal, Susana; Brookshire, E. N. Jack; Coble, Ashley A.; Dodds, Walter K.; Fazekas, Hannah M.; Helton, Ashley M.; Johnes, Penny J.; Johnson, Sherri L.; Jones, Jeremy B.; Kaushal, Sujay S.; Kortelainen, Pirkko; López‐Lloreda, Carla; Spencer, Robert G. M.; McDowell, William H.
• Is Part Of: Global change biology. Volume 28:Number 1(2022)
• Page Start: 98
• Page End: 114
• Publication Date: 2021-11-05
• Subjects: atmospheric acid deposition -- C:N stoichiometry -- dissolved organic carbon -- dissolved organic matter -- dissolved organic nitrogen -- long‐term trends -- streams; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.15965
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Dissolved organic carbon (DOC) and nitrogen (DON) are important energy and nutrient sources for aquatic ecosystems. In many northern temperate, freshwater systems DOC has increased in the past 50 years. Less is known about how changes in DOC may vary across latitudes, and whether changes in DON track those of DOC. Here, we present long‐term DOC and DON data from 74 streams distributed across seven sites in biomes ranging from the tropics to northern boreal forests with varying histories of atmospheric acid deposition. For each stream, we examined the temporal trends of DOC and DON concentrations and DOC:DON molar ratios. While some sites displayed consistent positive or negative trends in stream DOC and DON concentrations, changes in direction or magnitude were inconsistent at regional or local scales. DON trends did not always track those of DOC, though DOC:DON ratios increased over time for ~30% of streams. Our results indicate that the dissolved organic matter (DOM) pool is experiencing fundamental changes due to the recovery from atmospheric acid deposition. Changes in DOC:DON stoichiometry point to a shifting energy‐nutrient balance in many aquatic ecosystems. Sustained changes in the character of DOM can have major implications for stream metabolism, biogeochemical processes, food webs, and drinking water quality (including disinfection by‐products). Understanding regional and global variation in DOC and DON concentrations is important for developing realistic models and watershed management protocols to effectively target mitigation efforts aimed at bringing DOM flux and nutrient enrichment under control. Abstract : The recovery of streams to atmospheric acid deposition has led to the changes in dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations that have altered the stoichiometric ratios (DOC:DON) of the dissolved organic matter (DOM) pool. Certain sites have shown increasing DOC:DON trends (enrichment of the C‐rich fraction of the DOM pool), declining DOC:DON trends (enrichment of the N‐rich fraction of the DOM pool), and/or no clear trends in DOC:DON ratios. The responses vary geographically suggesting that the controls of DOM trends are at the regional to local scale.