Aquatic Invertebrates Inhabiting Saline Evaporation Ponds in the Southern San Joaquin Valley, California

A large number of shallow evaporation basins are currently being used to dispose of subsurface agricultural drain water in the southern San Joaquin Valley of California. The proliferation of ponds has led to an increase in shallow, saline aquatic habitats in this arid region of the state. During spring and summer 1987 we conducted a survey of three pond systems to describe invertebrate as- semblages inhabiting them. Because of relatively high salinities, evaporation ponds are harsh environments for most aquatic organisms. We found all ponds to have macroin vertebrate and zooplankton assemblages of very low diversity and there was a negative correlation between taxonomic diversity and salinity. Characteristic invertebrates among ponds included the water boatman Trichocorixa reticulata, Chironomidae (predominantly Tanypus sp.), brineflies (genus Ephydra), and the halophillic rotifer Brachionus plicitilis