The Great Salt Lake is known for its vastness, unique ecosystem, and a distinct, often unpleasant odor, colloquially termed “lake stink.” This smell, noted since early pioneer days, originates from specific biological and chemical processes within the lake. Understanding its scientific basis reveals the intricate relationship between the lake’s chemistry, its microscopic inhabitants, and environmental conditions.
The Lake’s Unique Chemistry
The Great Salt Lake is a hypersaline body of water, with salt concentrations significantly higher than the ocean. Its salinity fluctuates widely, from approximately 5% to over 30% in some areas. This extreme saltiness results from its nature as a terminal lake: water flows in from rivers but only leaves through evaporation, concentrating dissolved salts and minerals.
A railroad causeway divides the lake into two distinct sections. The North Arm, with minimal freshwater inflow, is more saline and chemically uniform, often near salt saturation. The South Arm receives most freshwater input, leading to lower average salinity and a tendency to stratify, forming a denser, saltier deep brine layer. The lake’s waters are rich in sodium chloride and have a high concentration of sulfates.
The Microscopic Culprits
Despite its harsh chemical environment, the Great Salt Lake teems with microscopic organisms adapted to high salinity. These “salt-loving” organisms, called halophiles, include bacteria, archaea, and algae. Algae like Dunaliella salina form the base of the lake’s food web and can influence its coloration.
Halophilic archaea, such as Halorubrum, thrive in salt-saturated regions, sometimes imparting pink, red, or violet hues to the water. These resilient microorganisms survive in low water activity and even within salt crystals. They are crucial to the lake’s ecosystem, playing a role in nutrient cycling and contributing to the processes that generate the lake’s distinctive odor.
The Source of the Odor
The Great Salt Lake’s characteristic “rotten egg” smell is primarily caused by hydrogen sulfide (H2S) gas. This gas is produced through biological and chemical reactions in the lake’s oxygen-deprived, or anoxic, environments. The lake’s sediments and deep brine layers are particularly prone to anoxic conditions, as oxygen-rich surface waters do not readily mix with these deeper zones.
Microorganisms, especially certain bacteria, are central to hydrogen sulfide production. These bacteria perform sulfate reduction, metabolizing abundant sulfates in the absence of oxygen and converting them into hydrogen sulfide gas. Anaerobic decomposition of organic matter, such as dead algae and plant remains in anoxic sediments, further contributes to H2S production. This microbial breakdown of sulfur-containing compounds, known as putrefaction, releases hydrogen sulfide as a byproduct.
Factors Influencing the Smell’s Intensity
The Great Salt Lake’s odor intensity varies due to several environmental factors. Strong winds can stir up shallow waters, mixing oxygen-depleted deep brine layers with surface waters. This releases accumulated hydrogen sulfide gas, making the smell more noticeable.
Warmer temperatures also increase microbial activity, boosting hydrogen sulfide production through decomposition and sulfate reduction. Additionally, exposed mudflats during low water levels intensify the odor. These areas contain rich organic matter that decomposes, releasing more sulfur gases. Northwest winds frequently transport the smell towards populated areas along the Wasatch Front.