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Rapid depletion of dissolved organic sulphur (DOS) in freshwaters

Brailsford, F.L.ORCID: 0000-0002-1088-3527, Glanville, H.C., Wang, D., Golyshin, P.N., Johnes, P.J., Yates, C.A. and Jones, D.L. (2020) Rapid depletion of dissolved organic sulphur (DOS) in freshwaters. Biogeochemistry, 149 . pp. 105-113.

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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 35S-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.

Item Type: Journal Article
Publisher: Springer
Copyright: © The Author(s) 2020
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