RUI Microbial Observatory at Soap Lake 

The National Science Foundation's Soap Lake Microbial Observatory was initiated in July 2002, and is funded through June, 2003. This is a collaboration between investigators at Central Washington University, Washington State University, and University of Missouri-Rolla to study the microbial ecology of Soap Lake, a haloalkaline lake located in Central Washington. Soap Lake is a lake characterized by permanent meromixis - a permanent chemically stratified state. The upper layer, termed the mixolimnion, and the lower layer, termed the monimolimnion, have not mixed for 2,000 - 10,000 years. Both layers are alkaline, with a pH 9.8-10.2, and both are salty. The alkaline pH is attributed to the high concentrations of carbonate, which on windy days will help to create layers of suds at the lake edges (hence the name "Soap Lake"). 

Photo of Soap Lake circa 1920, showing the characteristic suds.


The mixolimnion is now considered brackish, with a TDS (total dissolved solids) of 14 g/L , while the monimolimnion has a TDS of 85 grams/L. The lake is also saturated with sulfate, which can be found precipitated in the sediments as the mineral mirabilite. The lake supports great rates of sulfate reduction, with levels of sulfide in the monimolimnion regularly exceeding 200 mM. There is essentially no dissolved oxygen in the monimolimnion, which makes it a perfect site to study anaerobic activities. These attributes, among others, make Soap Lake an ideal site for a Microbial Observatory.