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Show Wurtsbaugh ( 1988) found that species ( cyanobacteria) that can fix atmospheric N2 and thus remove nitrogen limitation were limited by phosphorous. Both nitrogen and phosphorous are consequently of importance in regulating algal growth in GSL. The primary consumers of the bacteria and algae are brine shrimp and two species of brine flies. The biomass of these organisms is significant. Brine shrimp and their eggs are eaten by birds and commercially harvested by humans. Brine flies are eaten by birds and other species in their various life stages. Dead shrimp, flies, algae, other organisms and the waste products from all, in return, are recycled through the system by decomposers as base nutrients. Bacteria and Algae There are many species of bacteria that inhabit the waters of GSL. Often, these organisms assist in the decomposition of dead algae, animals and organic wastes entering the lake by stream flow and wind. It was reported in 1966 by Flowers and Evans that GSL hosts eleven species of bacteria that tolerate moderate to high levels of dissolved salt concentrations. The north arm of the lake supports only two genera of bacteria, Halobacterium and Halococcus, which are extreme halophiles present in numbers from 1,000,000 to 100,000,000 bacteria per milliliter, and are evident in the pink to purple color of this part of the lake. Relative to a freshwater lake, there are few species of bacteria and algae that exist in the hypersaline waters of GSL. However, these organisms have the potential under favorable conditions to exist in great numbers and account for a significant amount of biomass. A taxonomic study of the algal flora of the lake was done between November 1975 and July 1978. The flora consisted of four blue- green algae, seven green algae, one dinoflagellate and 17 diatoms species ( Felix and Rushforth, 1979). Two species of green algae, Dunaliella viridis and Dunaliella salina occur in the lake. During the winter months when there are no brine shrimp, these species typically thrive and the lake has a green hue. After brine shrimp populations are established by spring hatching, these species are grazed off Brine shrimp population numbers cycle over the course of the summer. Low numbers of brine shrimp allow these species to rebound and the lake can again have a green hue. Both of these species rely upon salinity levels of approximately 13- 19 percent to reproduce rapidly ( Van Auken and McNulty, 1973). Research is being conducted by Dr. Gary Belovsky of USU and GSLEP to further examine habitat parameters and productivity of lake algae. At the time of this writing, the experiments are still in progress. Diatom species in the lake seem to be more abundant when salinity levels fall. An abundance of these species gives the lake water a gold hue. Pennate diatoms are oblong in shape and have a silica covering. These diatoms are too large for brine shrimp nauplii to effectively forage upon them ( Stephens, 1998). Brine shrimp numbers seem to diminish when the lake is dominated by diatoms. Laboratory experiments at USU show die oflfs of brine shrimp in lake water that contained high numbers of diatoms and low numbers of green algae. Shrimp were observed with black spots on their bodies. This occurs when nutrition is poor and the shrimp subsequently are affected by a virus ( Belovsky, 1998). 69 |
