Experimental effects of elevated salinity on three benthic invertebrates in Pyramid Lake, Nevada

Abstract

Salinity of Pyramid Lake increased from 3.7 to 5.5%o between 1933 and 1980. Concern over future reductions in overall species richness prompted experiments to assess responses of dominant lake organisms to elevated salinity. Salinity tolerances of three important benthic invertebrates, Hyalella aztecta, Chironomus utahensis, and Heterocypris sp., were tested in controlled laboratory bioassays and also in a semi-natural environment consisting of large (47 m 3 ) mesocosms.Densities of H. azteca in mesocosms were significantly lower at salinities of 8.0 and 11.0%o compared with 5.6%o controls in year one, but not in 8.5%o salinity mesocosms in year two. The 96-h LC 50 for H. azteca was high at 19.5%o. Short-term mortalities of C. utahensis were 100% at salinities of 13.3%o and greater. Fifty-seven percent fewer larvae matured from third to fourth instar at 8.9 than at 5.5%o salinity in 17 day subacute bioassays. Furthermore, larval chironomid densities and emergence of adults from mesocosms were significantly reduced at salinities of 8.0%o and higher compared with controls. Mortality of Heterocypris sp. was 50%o at a salinity of 18.6%o in laboratory bioassays and populations in mesocosms ranged between 40 and 100% lower at salinities of 8.0 and 11.0%o than in controls.Multiple generation mesocosm experiments indicated all three invertebrates were more sensitive to elevated salinity than results of short-term bioassays. Our studies suggest populations of these invertebrates may be reduced from present levels if Pyramid Lake's salinity were to double, although none are expected to be extirpated. Food habit shifts and reduced production of lake fishes are likely consequences of salinity-induced disruption in the benthic invertebrate forage base.

Salinity effects on macroinvertebrate assemblages and waterbird food webs in shallow lakes of the Wyoming High Plains

“…In our study, Gammarus lacustris was abundant in George and common in Caldwell (both oligosaline), but was absent from all other lakes; Hyalella azteca was abundant in all oligosaline lakes, but rare in mesosaline lakes. In mesocosms, H. azteca densities were lower in water with 8 and 11 g 1-' TDS than in water with 5.6 g 1-' (Galat et al, 1988). In our study, direct effects of salinity on other taxa could not be adequately evaluated because we did not identify most taxa to species.…”

“…Adequate understanding and predictive capabilities will require laboratory tests of tolerance to salt in both water and food, together with field data and modeling of indirect salinity effects on food web structure (Galat & Robinson, 1983;Vareschi, 1987;Galat et al, 1988;Gulley et al, 1992).…”

Effects of macrophyte growth forms on invertebrate communities in saline lakes of the Wyoming High Plains

“…5) . In inland waters, gastropods and to a lesser extent amphipods are salinity-intolerant (Rawson & Moore, 1944 ;Galat et al ., 1988 ;Swanson et al, 1988) . In the benthic community, chironomids were much more dominant in mesosaline than oligosaline lakes (Fig .…”

Water beetle tolerance to salinity and anionic composition and its relationship to habitat occupancy

“…Organisms have developed physiological traits for salt tolerance and adaptations to different types of chemicals (Herbst, 2001) that determine their habitat occupation, abundance and broad scale distribution (Galat et al, 1998;Williams et al, 1990;Cervetto et al, 1999). Salt acts like a toxic substance (Kefford et al, 2002) that threatens the internal hydric stability of an organism; thus, the occupation of saline habitats is mediated by the physiological adaptation of species to the effects of high salt concentrations (Bradley, 2009).…”