USA. Great Salt Lake, UT. 2016. Swimming on the north shore of the great salt lake near the Spiral Jetty. Jaden Olson and Benjamin Anderson (left). They are students. In 1959, a 30-foot stone railroad causeway replaced the battered wood trestle. As a result, lake circulation reduced drastically. Great Salt Lake now has two distinct sections, the north arm and the south arm. The water in the north arm has a high salt concentration of approximately 26–28% due to little freshwater input. Only two types of known bacteria can currently live in the saturated North Arm waters: the halophiles Halobacterium and Halococcus. A purplish pigment in these halophiles is responsible for the unique reddish color of GSL's northern section.