TY - JOUR

T1 - Rapid depletion of dissolved organic sulphur (DOS) in freshwaters

AU - Brailsford, F. L.

AU - Glanville, H. C.

AU - Wang, D.

AU - Golyshin, P. N.

AU - Johnes, P. J.

AU - Yates, C. A.

AU - Jones, D. L.

PY - 2020/5/2

Y1 - 2020/5/2

N2 - 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.

AB - 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.

KW - Dissolved organic matter

KW - DOS processing

KW - Nutrient cycling

KW - Radioisotopes

KW - Sulphate

U2 - 10.1007/s10533-020-00669-4

DO - 10.1007/s10533-020-00669-4

M3 - Article

VL - 149

SP - 105

EP - 113

JO - Biogeochemistry

JF - Biogeochemistry

SN - 0168-2563

IS - 1

ER -