Threatened Bliss Rapids snail's susceptibility to desiccation: Potential impact from hydroelectric facilities

Abstract

Water levels in the regulated Snake River, southern Idaho, U.S.A. can fluctuate daily and seasonally due to hydroelectric demands. The federally listed threatened Bliss Rapids snail, Taylorconclia serpenticola Hershler et al., 1994 (Family: Hydrobiidae), survives in and near these fluctuation zones. Remaining T. serpenticola populations occur only in sections of the Snake River that are impacted by these hydroelectric facilities and associated springs. Because effects of rapid draw-down in fluctuation zones on T. serpenticola are unknown, we conducted a laboratory experiment to evaluate potential impacts of desiccation. Our experiment compared desiccation resistance at several air temperatures, on dry and wetted substrates, and for ‘small’ vs. ‘large’ snails. Probit regression-maximum likelihood models estimated lethal time (LTj,,) values. Suiwival was significantly greater on wetted substrate than on dry substrate and was lowest at temperatures <0‘’C and at 37'^C on dry substrate. Survival was greatest at 17°C on wetted substrate. There was no significant difference in survival at temperatures above 0°C on dry substrate other than at 37°C. LTj,, survival ranged from 0.5 hours at -7°C to 157.0 hours at 17°C on wetted substrate. There were no significant differences in survival relative to snail size in any treatment. Our results suggest that desiccation could impact T. serpenticola populations if snails become stranded on dry substrates during rapid water-level fluctuations of the Snake River, particularly during subzero winter or extreme high summer temperatures. The most important factor determining survival would be the ability to find refuge on the undersides of cobbles, where snails typically occur, or in habitats that remained moist for the duration ot the draw-down of the river.

Effects of desiccation on native and non‐native molluscs in rivers

“…However, this requires anaerobic respiration, which is inefficient (McMahon, 1988;Byrne et al, 1990). For instance, additional experiments on the effect of size classes of D. rostriformis bugensis and M. leucophaeata showed that smaller individuals died faster than larger individuals, which agrees with other molluscan studies (Iwasaki, 1997;Paukstis et al, 1999;Montalto & Ezcurra de Drago, 2003;Richards & Arrington, 2008;Havel, 2011;Van Leeuwen & Van der Velde, 2012). In addition, aerial respiration affects the acid-base balance, ion regulation and excretion (Byrne & McMahon, 1991).…”

“…The spatiotemporal variability of these factors in ecosystems may affect desiccation tolerance of molluscs. Other behavioural strategies of molluscs are burial (Byrne et al, 1990) and the formation of dense overlapping layers of individuals, which create moist microhabitats that increase survival during droughts (Montalto & Ezcurra de Drago, 2003;Richards & Arrington, 2008). Moreover, desiccation tolerance is also determined by shell size of the specimens used for experiments.…”

“…Desiccation of molluscs can be prevented by burial behaviour (Byrne et al, 1990) and availability of specific microhabitats, such as debris Richards & Arrington, 2008), layers of living and dead molluscs (Byrne & McMahon, 1991;Montalto & Ezcurra de Drago, 2003) and stones. Desiccation of molluscs can be prevented by burial behaviour (Byrne et al, 1990) and availability of specific microhabitats, such as debris Richards & Arrington, 2008), layers of living and dead molluscs (Byrne & McMahon, 1991;Montalto & Ezcurra de Drago, 2003) and stones.…”

“…Severe winter droughts and heat waves may cause higher mortality rates of molluscs (Boyden, 1972;Skoog, 1976;Byrne et al, 1988;McMahon et al, 1993;Ricciardi et al, 1995;Paukstis et al, 1999;Richards et al, 2004;Richards & Arrington, 2008). The PNOFs were derived from SSDs based on experiments at 20°C mimicking summer conditions.…”

“…For several mollusc species, experimentally derived desiccation tolerances are available (Von Brand, McMahon & Nolan, 1957;Boyden, 1972;Skoog, 1976;Byrne, McMahon & Dietz, 1988;McMahon, Ussery & Clarke, 1993;Ricciardi, Serrouya & Whoriskey, 1995;Paukstis et al, 1999;Darrigran, Maroñas & Colautti, 2004;Richards, O'Connell & Shinn, 2004;Ramakrishnan, 2007;Richards & Arrington, 2008;Havel, 2011). For several mollusc species, experimentally derived desiccation tolerances are available (Von Brand, McMahon & Nolan, 1957;Boyden, 1972;Skoog, 1976;Byrne, McMahon & Dietz, 1988;McMahon, Ussery & Clarke, 1993;Ricciardi, Serrouya & Whoriskey, 1995;Paukstis et al, 1999;Darrigran, Maroñas & Colautti, 2004;Richards, O'Connell & Shinn, 2004;Ramakrishnan, 2007;Richards & Arrington, 2008;Havel, 2011).…”