Global distribution of dissolved organic matter along the aquatic continuum: Across rivers, lakes and oceans

Philippe Massicotte, Eero Asmala, Colin Stedmon, Stiig Markager

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Abstract

Based on an extensive literature survey containing more than 12,000 paired measurements of dissolved organic carbon (DOC) concentrations and absorption of chromophoric dissolved organic matter (CDOM) distributed over four continents and seven oceans, we described the global distribution and transformation of dissolved organic matter (DOM) along the aquatic continuum across rivers and lakes to oceans. A strong log-linear relationship (R2 = 0.92) between DOC concentration and CDOM absorption at 350 nm was observed at a global scale, but was found to be ecosystem-dependent at local and regional scales. Our results reveal that as DOM is transported towards the oceans, the robustness of the observed relation decreases rapidly (R2 from 0.94 to 0.44) indicating a gradual decoupling between DOC and CDOM. This likely reflects the decreased connectivity between the landscape and DOM along the aquatic continuum. To support this hypothesis, we used the DOC-specific UV absorbance (SUVA) to characterize the reactivity of the DOM pool which decreased from 4.9 to 1.7 m2 × gC −1 along the aquatic continuum. Across the continuum, a piecewise linear regression showed that the observed decrease of SUVA occurred more rapidly in freshwater ecosystems compared to marine water ecosystems, suggesting that the different degradation processes act preferentially on CDOM rather than carbon content. The observed change in the DOM characteristics along the aquatic continuum also suggests that the terrestrial DOM pool is gradually becoming less reactive, which has profound consequences on cycling of organic carbon in aquatic ecosystems.
Original languageEnglish
JournalScience of the Total Environment
Volume609
Pages (from-to)180-191
ISSN0048-9697
DOIs
Publication statusPublished - 2017

Keywords

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution
  • Absorption
  • Biogeochemistry
  • Carbon cycling
  • Chromophoric dissolved organic matter (CDOM)
  • Dissolved organic carbon (DOC)
  • Specific UV absorbance (SUVA)
  • Biological materials
  • Dissolution
  • Ecology
  • Ecosystems
  • Geographical distribution
  • Hydrogeology
  • Lakes
  • Oceanography
  • Organic carbon
  • Organic compounds
  • Piecewise linear techniques
  • Stream flow
  • Chromophoric dissolved organic matter
  • Dissolved organic carbon
  • Dissolved organic matters
  • Freshwater ecosystem
  • Linear relationships
  • Piecewise linear regression
  • Specific uv absorbance
  • Aquatic ecosystems
  • Surveying
  • Waterways
  • Ecology and Ecosystems
  • Biological Materials
  • Oceanography, General
  • Geology
  • Geochemistry
  • Chemical Operations
  • Organic Compounds
  • Combinatorial Mathematics, Includes Graph Theory, Set Theory

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