Life in a Hypervariable Environment
The Great Salt Plains (GSP) spans approximately 65 km2 in northwestern Oklahoma, USA. Although soil on the flats consistently retains about 10–20% water by weight, the flats are largely devoid of macroscopic plants due to seepage and evaporation of subterranean NaCl-dominated Permian brine at 15–25% salinity. Except following infrequent heavy rain, a thin (<1–10 mm) variable salt crust persists over much of the flats, and the interstitial water is often near NaCl saturation (>25%). However, several intermittent and a few permanent freshwater streams traverse the flats, providing localized lower salinity niches. Episodic heavy direct rainfall and associated flooding of these streams inundates vast areas of the flats with fresh or low salinity water, which quickly recedes. The flats then return to the more typical salt crust over a period of days to weeks.
Other than the GSP, virtually nothing is known about algae of hypersaline intermittent lakes, even in Australia which has countless such lakes (Timms, in press). Algae are ubiquitous on the GSP flats, although chlorophyll biomass is typically very low, and diversity appears to be restricted to a small subset of genera in the divisions Cyanophyta, Chlorophyta, and Bacillariophyta (Major et al., 2005; Kirkwood and Henley, 2006). Chlorophyll biomass is correlated with interstitial dissolved inorganic nitrogen (DIN), particularly ammonium, but not soluble reactive phosphorus (Kirkwood and Henley, 2006). However, given the dynamic salinity and temperature conditions on the flats surface (Major et al., 2005; Kirkwood and Henley, 2006), nutrient availability may be a comparatively trivial problem for physically stressed algae and cyanobacteria. Indeed, most GSP algal isolates are unable to grow in the laboratory at the high interstitial salinities typically found in situ, yet direct soil samples invariably yield viable algae when exposed to reduced salinities in the laboratory (Major et al., 2005; Kirkwood and Henley, 2006). Thus, most or all of the algae of the GSP must tolerate high salinities that will not support growth.
KeywordsDissolve Inorganic Nitrogen Soluble Reactive Phosphorus Great Salt Lake Desiccate Condition Great Salt Plain
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