Salinity Thresholds, Lake Size, and History: A Critique of the NAS and CORI Reports on Mono Lake
Hurlbert, Stuart H.
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These two reports usefully summarize and evaluate large amounts of <br /><br />information. They both suffer from and perpetuate, however, a deficient concep- <br /><br />tual framework for analyzing changes in the Mono Lake ecosystem. Specifically, <br /><br />their assessments of the present and future state of this lake 1) use language <br /><br />implying that salinity-induced changes in the biota will begin to occur only at <br /><br />certain critical salinity thresholds, 2) neglect the significance of lake size as a <br /><br />determinant of bird food supplies, and 3) lack historical perspective in failing to <br /><br />consider what changes in the lake ecosystem may have been caused by historical <br /><br />changes in the salinity and size of the lake. The desirability of developing explicit <br /><br />models for the system is emphasized. Especially needed are models for: 1) the <br /><br />influence of salinity and lake size on the abundance of brine flies and brine shrimp, <br /><br />and 2) the influence of the abundance of these invertebrates on the bird populations <br /><br />that use the lake. To illustrate the heuristic value of such models, Rawson's models <br /><br />relating productivity and standing crop to lake mean depth are applied to Mono <br /><br />Lake. The results suggest some unusual consequnces of the lake's particular mor- <br /><br />phometry, especially for lake level changes between 6370 ft and 6380 ft.