Determination of thiosulfate in a meromictic lake

Abstract

SUMMARY: An analytical procedure using a new high performance liquid chromatography (HPLC) for the sensitive measurement of thiosulfate (S2O32−) in natural water was examined. Using a Shodex Asahipak NH2P‐50 (4E) column and the HPLC system, thiosulfate was identified clearly by UV absorption at 215 nm with 100 mM Na2HPO4 (pH 8.5) as a solvent. Thiosulfate could be quantified in less than 20 min with a detection limit of about 10 pmol which corresponds to an injection of 20 μL from a standard with a concentration of 0.5 μM. Starting at the lowest detectable concentration, the calibration curve for thiosulfate was linear over a concentration range of four orders of magnitude. Thiosulfate analysis was not affected by the saline concentration of samples at up to 1 M NaCl. This procedure was applied to water samples of a meromictic lake, Lake Suigetsu, Fukui, Japan. Thiosulfate was found in lake water sampled below the chemocline at a concentration of less than 1–60 μM but not in the oxic surface water.

Abundance and diversity of sulphate-reducing bacterioplankton in Lake Suigetsu, a meromictic lake in Fukui, Japan

“…Lake Suigetsu has attracted considerable interest, especially in bacterial sulphate reduction with reference to the carbon cycle, because of the large accumulation of sulphide in the deeper layers of the lake (Kondo et al 2000); however, little is known about the distribution and structure of the SRB population in the lake. Since no suitable media are available to enumerate all SRB simultaneously, we developed a method to quantify the microorganisms responsible for sulphate reduction directly from natural samples (Kondo et al 2004).…”

“…Seawater from the Sea of Japan comes through Lakes Hiruga and Kugushi next to Lake Suigetsu. Thus the anoxic water chemistry of Lake Suigetsu is dominated by inorganic sulphur compounds with a high concentration of sulphate and steep gradients of sulphide at the chemocline (Kondo et al 2000, Matsuyama 1973, Matsuyama & Saijo 1971. Because Lake Suigetsu is highly sulphidic, we assume microbiological sulphate reduction is responsible for the production of sulphide.…”

“…Members of the Desulfobulbaceae family can use alternative electron acceptors leading to sulphate and can disproportionate sulphur oxianions while Desulfobulbus is known to be able to grow by fermentation of lactate or ethanol and CO 2 without sulphate. Sulphate concentrations below the oxycline are 2-8 mM (Kondo et al 2000) which is sufficiently high as not to limit sulphate reduction. However, we previously reported that thiosulphate was detected in anoxic waters below the oxycline (6-7 m) of Lake Suigetsu, ranging from 1 mM or less to 60 mM (Kondo et al 2000).…”

“…Sulphate concentrations below the oxycline are 2-8 mM (Kondo et al 2000) which is sufficiently high as not to limit sulphate reduction. However, we previously reported that thiosulphate was detected in anoxic waters below the oxycline (6-7 m) of Lake Suigetsu, ranging from 1 mM or less to 60 mM (Kondo et al 2000). This suggests thiosulphate may be used as an electron acceptor or may be disproportionated by microorganisms belonging to cluster G, including the thiosulphate-disproportionating bacterium Desulfocapsa.…”

“…Lake Suigetsu is a meromictic lake in Fukui, Japan, characterised by a permanent oxycline at a depth between 5 and 8 m separating the aerobic freshwater epilimnion from the anaerobic, saline, sulphidogenic hypolimnion (Kondo et al 2000, Matsuyama 1973, Matsuyama & Saijo 1971, Takahashi & Ichimura 1968. Seawater from the Sea of Japan comes through Lakes Hiruga and Kugushi next to Lake Suigetsu.…”