Environment and phytoplankton relative abundances in a hypersaline lake: 27 years in Great Salt Lake, USA and experiments

Over 27 years in Great Salt Lake (GSL: Utah, USA), phytoplankton relative abundances of chlorophytes, diatoms and cyanobacteria varied dramatically (monthly < 10–90% for each). This observed variability within the lake was compared to laboratory experimental results with pure cultures (> > 90%) of several of the most common GSL phytoplankton (chlorophyte–Dunaliella viridis, diatom–Nitzschia epithemioides, cyanobacterium–Euhalothece sp.). Maximum abundances and growth rates were measured across ranges of temperature (10–30 °C), salinity (30–150 ppt) and nutrients (nitrogen: 0.0–0.64 mg/L, silica:17–51 mg/L) observed within GSL. Experimental results indicated the abundance and growth rate of D. viridis increased as salinity and nitrogen increased and decreased as temperature increased. The abundances and growth rates of N. epithemioides and Euhalothece decreased as salinity increased, and increased as temperature and nitrogen increased, and N. epithemioides increased as silica increased. Observed GSL phytoplankton relative abundances responded to environmental conditions as observed in the experiments, but correlations were weak except for chlorophytes, as diatoms and cyanobacteria relative abundances occasionally increased with unfavorable experimental conditions. The weak correlations between laboratory results and GSL observations could be due to the release of diatoms and cyanobacteria from microbialite biofilms in the lake’s benthos with cold stress and high winds, as a 5–10% release can produce diatom and cyanobacteria phytoplankton relative abundances of 24–48%. This suggests a novel potential link between GSL pelagic and benthic zones.