Defining salinity limits on the survival and growth of benthic insects as conservation management targets for saline Walker Lake, Nevada, USA

Authors: David B. Herbst, R. Bruce Medhurst, Scott W. Roberts, Ian D. Bell

Year: 2012 (xliv)

Abstract

Walker Lake, Nevada, a saline desert lake, has been undergoing loss of stream inflows, lowering of lake level, and concentration of dissolved salts for over a century due to agricultural diversions of water. This lake is or has been inhabited by native fish and visited by many species of water birds that depend on productive invertebrate life for food resources. The extent to which salinity limits the present and future viability of resident invertebrate fauna was evaluated using salt-tolerance bioassays and studies of salinity effects on growth and behavior in larval stages of the midges Cricotopus ornatus and Tanypus grodhausi, and nymphs of the damselfly Enallagma clausum. We found that salinities into and above a range of 20-25 g/L present either lethal limits or sublethal inhibitions to survival and growth that will eliminate or substantially reduce the current community of common benthic invertebrates. Midge mortality was high above 25 g/L and damselfly nymphs were most vulnerable in early instars, and grew slowly and fed less when salinity increased from 20 to 30 g/L. A conservation target for the lake that incorporates survival of native fish and optimum production of invertebrate life should be within the range of 10 to 15 g/L salinity of Walker Lake water.