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.
- Dissolved organic matter
- DOS processing
- Nutrient cycling
Brailsford, F. L., Glanville, H. C., D, W., Golyshin, P. N., Johnes, P. J., Yates, C. A., & Jones, D. L. (2020). Rapid depletion of dissolved organic sulphur (DOS) in freshwaters. Biogeochemistry. https://doi.org/10.1007/s10533-020-00669-4