BOD bottles holding water collected in three strata of the Great Salt Lake show the extreme differences in the microbial community. The bottle on left shows water from the lake's surface where salinity at the time was near 6% and green algae and diatoms were dominant. The middle bottle contains purple-sulfur bacteria collected at 8.5 m (28')where a chemocline develops in the lake and where oxygen is absent. The purple pigment helps the bacteria capture the limited light at those depths and use it for a particular type of photosynthesis. The bottle on the right contains sedimented and decomposed algae in the deep brine layer (monimolimnion).
Photo: May 1996. Two hundred-year precipitation events had decreased the salinity in the lake considerably. The surface waters are more commonly 12-16% salinity (120-160 g/L).