Sakinaw Lake

The Hallam Lab

Investigating microbial communities…
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Sakinaw Lake

Ecosystem Type: Meromictic Lake
Location: 49° 40.968 N, 124° 00.119 W

Located along the west coast of British Columbia, Sakinaw Lake is a fascinating location to study microbial communities involved in gas cycling. The lake was once a fjord connected to the Salish Sea, but, at the end of the last deglaciation, the combination of land uplift and sea level fall isolated the basin. Since the time of isolation (~11,000 years ago) the water balance of the lake has evolved, through processes of evaporation and precipitation, such that the seawater is now overlaid with a 33 m thick layer of fresh water. This layering makes the lake strongly stratified, or meromictic, which inhibits seasonal overturning of the water column. Not unique to the BC coast, meromictic lakes are found on every continent and may have a variety of physical factors controlling their stratification

The surface layer of Sakinaw Lake is similar in microbial composition to most freshwater lakes, but at the depth of the redox transition zone, where salinity increases and oxygen decreases due to reduced mixing, the microbial community becomes specialized at utilizing electron acceptors, such as nitrate and sulphate, for microbial oxidation of organic material. This transition zone is seasonally very stable at Sakinaw Lake and is 30 m thick allowing for discrete replicate sampling of the microbial community along the redox gradient. Below this zone, the bottom waters, or monimolimnion, are anoxic and are supersaturated with gases such as methane (CH4), hydrogen sulphide (H2S), and carbon dioxide (CO2).

Repeat measurements of this stable, and broad, redox transition zone allowed for the sampling of many distinct microbial subpopulations that appear specialized to their niche within that zone. While most microbes are not capable of being brought into culture, Esther Gies used novel single cell genomic techniques to elucidate some of the ‘microbial dark matter’ and establish many bacterial and archaea candidate phyla as part of her PhD work.

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The good ship R/V Kraken that served the Hallam Lab so well.