Presenter(s): Maisie Bailey – Biology
Faculty Mentor(s): Richard Castenholz
Poster 61
Research Area: Natural science
The survival of photosynthetic microorganisms buried in muds of a saline lake over several years of a saline lake has been observed. This phenomenon was quite unexpected and unprecedented. Lake Abert is a large, closed basin, soda lake in eastern Oregon. It normally has a pH of ~10, a salinity of about 30-50 ppt, and annual temperatures of 4-25°C. Under these conditions the predominant phototrophs in the water were several species of cyanobacteria, diatoms, green algae, and micro-invertebrates. During 2013-2016, the lake water had shrunk in area, drying out almost completely due to evaporation exceeding input. Salinity reached over 200 ppt, with most of the sodium carbonates precipitated, NaCl remaining as the predominant salt in solution. Photosynthetic microorganisms were no longer present visibly nor culturable from this water. However, the former shores were bounded by moist muds (~50% water by weight), hyper-saline (>200 ppt), anoxic, with pH>10. Samples taken from this mud were collected and incubated in light at 24°C in liquid nutrient medium at a salinity of 30 ppt. Various cyanobacteria and diatoms grew as enrichments and were isolated and purified in culture. These results occurred after mud samples had been kept in the dark for over 12 months at 12°C. All of the cyanobacteria in culture also survived desiccation. Gene sequences of selected survivors will be obtained to ascertain if these strains are genetically unique. Survival under these severe conditions is unprecedented and results may apply to limits of photosynthetic microorganisms in other extreme environments.