Between the Niobrara, Platte, and Loup Rivers and the east-facing buttes of Butte County, the Sandhills cradle the alkaline lakes of western Nebraska. The lakes flourish with wildlife and inspire wonder in all who visit and contemplate their subtle beauty. Surprisingly, the Sandhills alkaline lakes (SAL) are unique to the Western Hemisphere and are a true treasure—but they are also a well-kept secret, even to most Nebraskans. What makes this ecosystem so special? Potash.
Potash (potassium carbonate, K2CO3) was named for the ash formed from burning plants, but the term today is applied to several potassium-containing salts. Potash leaches slowly through soils and into closed water basins, where the salts accumulate as water evaporates. Many of the interdunal lakes in Garden and Sheridan Counties are highly alkaline (pH > 10), and it is common to see their shorelines encrusted white from evaporated brine. Are there alkaline lakes in other places? Yes, but what makes the alkaline lakes of the Sandhills unusual is the high carbonate (alkalinity) coupled with the high potassium content of the water. Most other known alkaline lakes on Earth are relatively high in sodium, rather than potassium; these are referred to as soda lakes. The other two regions of the world with lakes similar to those of the Sandhills are the northern playa of Lake Chad in Africa and Qaidam Basin in China.
These lakes are intriguing because a potassium-rich environment is anathema to most cellular life, and yet these lakes are teeming with life, microbial life. How do these organisms adapt to the otherwise toxic environment? The potassium-to-sodium ratios in the highly alkaline lakes are approximately ten times higher than ocean water or fluids of the human body. This means that the organisms living in these conditions are expending enormous energy just to maintain their standard physiological state, assuming they have physiologies similar to other known organisms. Or perhaps they have unknown physiological mechanisms. These questions are central to understanding how anything can live in such a harsh environment and also how these environments fostered their evolution. Our preliminary studies on the diversity of bacteria of the alkaline lakes indicate that many are from groups classified according to terms that refer to life in extreme conditions, including haloalkaliphilic (loving alkaline salty environments), chemolithoautotrophic (making energy from rocks), and salt-tolerant polyextremophiles (tolerant of more than one extreme condition). Given the unusual and harsh conditions of the Sandhills alkaline lakes, a team of scientists is working to describe the diversity of microbial life and to uncover just how they carry out life in such a strange and wondrous environment.