Cascading sulfur cycling in simulated oil sands pit lake water cap mesocosms transitioning from oxic to euxinic conditions.

Base Mine Lake (BML), the first full-scale demonstration of oil sands tailings pit lake reclamation technology, is experiencing expansive, episodic hypolimnetic euxinia resulting in greater sulfur biogeochemical cycling within the water cap. Here, Fluid Fine Tailings (FFT)-water mesocosm experiments simulating the in situ BML summer hypolimnetic oxic-euxinic transition determined sulfur biogeochemical processes and their controlling factors. While mesocosm water caps without FFT amendments experienced limited geochemical and microbial changes during the experimental period, FFT-amended mesocosm water caps evidenced three successive stages of S speciation in ∼30 days: (S1) rising expansion of water cap euxinia from FFT to water surface; enabling (S2) rapid sulfate (SO) reduction and sulfide production directly within the water column; fostering (S3) generation and subsequent consumption of sulfur oxidation intermediate compounds (SOI).

pH and thiosulfate dependent microbial sulfur oxidation strategies across diverse environments.

Sulfur oxidizing bacteria (SOB) play a key role in sulfur cycling in mine tailings impoundment (TI) waters, where sulfur concentrations are typically high. However, our understanding of SOB sulfur cycling via potential S oxidation pathways (, r, and SI) in these globally ubiquitous contexts, remains limited. Here, we identified TI water column SOB community composition, metagenomics derived metabolic repertoires, physicochemistry, and aqueous sulfur concentration and speciation in four Canadian base metal mine, circumneutral-alkaline TIs over four years (2016 - 2019).

O partitioning of sulfur oxidizing bacteria drives acidity and thiosulfate distributions in mining waters.

The acidification of water in mining areas is a global environmental issue primarily catalyzed by sulfur-oxidizing bacteria (SOB). Little is known about microbial sulfur cycling in circumneutral pH mine tailing impoundment waters. Here we investigate biological sulfur oxidation over four years in a mine tailings impoundment water cap, integrating aqueous sulfur geochemistry, genome-resolved metagenomics and metatranscriptomics.