ECOLOGICAL RESPONSES TO MULTIPLE STRESSORS IN A SALINE LAKE AND IMPLICATIONS FOR CONSERVATION

Saline lakes throughout the world are threatened by decreasing water levels and increasing salinity due to climate changes and diversions of inflows. At Mono Lake, California, stream diversions led to an elevation decline and doubling of salinity. Since 1981, periods with large snowmelt runoff, followed by periods with low runoff and continued water diversions, have led to six episodes of strong year-round stratification followed by eventual winter mixing. During periods of persistent stratification, vertical mixing of nutrients and algal abundance were reduced and influenced Artemia monica, a critical food source for breeding gulls and migratory grebes and phalaropes. The variations in stratification of varying duration have compounded ecological variability due to climatic variation and changing management regimes. Measurements from 1980 to the present, combined with statistical analyses, experimental studies and modeling provide the basis for interpretation of ecological changes over 45 years. Adult Artemia abundance has large interannual variability and can include a large second generation associated with a very low spring hatch, years of high abundance associated with the breakdown of long periods of stratification, and a 42% decline in abundance-weighted fecundity. Recent high phytoplankton abundance during summer, not previously observed, indicate a significant shift in the balance between growth and loss of phytoplankton. These scientific results have contributed to revised regulation of water diversions and continue to guide adaptive management of the lake.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: John Melack, University of California, Santa Barbara (melack@bren.ucsb.edu)

Authors:

JOHN MELACK, University of California, Santa Barbara  (melack@bren.ucsb.edu)

Caroline Vignardi, University of California, Santa Barbara  (caroline@ucsb.edu)

Robert Jellison, University of California, Santa Barbara  (rjellison@ucsb.edu)