Rapid depletion of dissolved organic sulphur (DOS) in freshwaters

F.L. Brailsford*, H.C. Glanville, Wang D, P.N. Golyshin, Penny J Johnes, Christopher A Yates, D. L. Jones

*Corresponding author for this work

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Abstract

Sulphur (S) is a key macronutrient for all organisms, with similar cellular requirements to that of phosphorus (P). Studies of S cycling have often focused on the inorganic fraction, however, there is strong evidence to suggest that freshwater microorganisms may also access dissolved organic S (DOS) compounds (e.g. S-containing amino acids). The aim of this study was to compare the relative concentration and depletion rates of organic 35 S-labelled amino acids (cysteine, methionine) with inorganic S (Na235SO4) in oligotrophic versus mesotrophic river waters draining from low nutrient input and moderate nutrient input land uses respectively. Our results showed that inorganic SO42-was present in the water column at much higher concentrations than free amino acids. In contrast to SO42-, however, cysteine and methionine were both rapidly depleted from the mesotrophic and oligotrophic waters with a halving time \ 1 h. Only a small proportion of the DOS removed from solution was mineralized and excreted as SO42-(\ 16% of the total taken up) suggesting that the DOS could be satisfying a demand for carbon (C) and S. In conclusion , even though inorganic S was abundant in freshwater, it appears that the aquatic communities retained the capacity to take up and assimilate DOS.
Original languageEnglish
Number of pages9
JournalBiogeochemistry
DOIs
Publication statusPublished - 2 May 2020

Keywords

  • Dissolved organic matter
  • DOS processing
  • Nutrient cycling
  • Radioisotopes
  • Sulphate

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