Sulfur Cycling in the Cariaco Basin and the Meromictic Green Lake in Fayetteville, New York

摘要

An imbalance in the flux of oxidants and reductants to the suboxic zone (which lies between layers containing oxygen (O2) and hydrogen sulfide (H2S)) has been observed in many anoxic basins. These basins also have high levels of chemoautotrophy and elemental sulfur in the suboxic zone, which is defined here as the region where oxygen levels are < 2microM and sulfide levels are < 2microM. It has been hypothesized that there is a 'cryptic sulfur cycle' in the suboxic zone that is mediated by sulfate (SO42--) reducers and sulfide oxidizers. This study examines elemental sulfur in the Cariaco Basin and a meromictic lake using HPLC and Raman microspectroscopy techniques to evaluate if the elemental sulfur is produced by biological or chemical oxidation. Concentrations of particulate sulfur (> 0.2microm) and total zerovalent sulfur (TZVS made up of particulate sulfur, colloidal sulfur, and polysulfides) were determined in the suboxic zone of the Cariaco Basin in November 2014 and 2015. Analysis of samples from November 2015 with Raman microspectroscopy found sulfur inside cells at two depths in the suboxic zone. HPLC and Raman analyses of samples from Fayetteville Green Lake found little elemental sulfur, perhaps indicating that the layer previously observed to contain high concentrations of elemental sulfur and TZVS by Zerkle et al (2010) may have been missed, and that samples need to be collected with higher depth resolution than used during the present study. Raman microspectroscopy was effective for finding sulfur associated with cells. Future work could include examining samples collected with high depth resolution from Fayetteville Green Lake, examining previous Cariaco samples with Raman microspectroscopy, and exploring density data from the Cariaco Basin to see if high levels of elemental sulfur are associated with intrusions of oxygenated water.