Utah's Gunnison Island

Aerial view of Gunnison Island - Great Salt Lake, Utah
Aerial view of Gunnison Island - Great Salt Lake, Utah

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Gunnison Island is located in Gunnison Bay, the northwest arm of Utah's Great Salt Lake. Historically, circulating currents have kept its water mixed with the rest of the lake, so that Gunnison Bay had approximately the same salinity level as the Great Salt Lake as a whole.

In the 1950s, a solid-fill railroad causeway was built across the bottom of the bay, isolating it from the rest of the lake. Little fresh water flows into Gunnison Bay, and there is little exchange of water through the small cuts in the causeway.

In the years since the railroad's construction, evaporation has gradually increased the salinity to extremely high levels, far higher than the rest of the lake, and approaching that of the Dead Sea. The reddish-purple water color is the result of the algae Dunaliella salina and bacterium Halobacterium that thrive in the hypersaline environment.

Numerous birds, including a large population of American White Pelicans, use the island as a rookery. In the 1890s, the bird's guano was mined as fertilizer. These days, the entire island is part of Gunnison Island State Wildlife Management Area, with access restricted to protect the nesting birds.