A solid-fill causeway completed in 1959 by the Southern Pacific Railway divides the shallow Great Salt Lake. The salinity of the south arm (Gilbert Bay)varies with climatic cycles, but usually is between 11% and 16%. Water flows through culverts and breaches in the causeway into the north arm (Gunnison Bay)and evaporates further so that salinities are near saturation (30%). The open waters of Gilbert Bay supports a variety of phytoplankton species, particularly the green algae, Dunaliella viridis, which are grazed by brine shrimp (Artemia franciscana). In the upper right section of the photo one can see a slick of resting eggs (cysts) of the brine shrimp that have been concentrated in a convergence zone.


Gunnison Bay supports bacteria-like Archaea, and Dunaliella salina that yield the striking pink color. The waters of Gunnison Bay are too salty to support populations of invertebrates.


Water depth near this region of the lake is ca. 8.5 m. Promontory Point is in the left background.
Photo: 24 June 2009