Physiological consequences of exposure to salinized roadside ponds on wood frog larvae and adults

Abstract

Aquatic organisms living adjacent to roads face many challenges posed by exposure to toxic runoff. The use of deicing road salt across northern latitudes has salinized nearby freshwater habitats. Freshwater amphibians exposed to road salt at early life stages typically experience reduced survival; however, few studies address laterlife effects. One study investigating whether populations can adapt to roadside ponds found survival in wood frog embryos raised in roadside environments was lowest in individuals with parents from roadside ponds. We investigated whether this negative response is also exhibited in late larval stages in reciprocally transplanted individuals from roadside populations and those located away from roads ('woodland' populations). We found reduced growth rates and more variable developmental rates in larvae raised in roadside ponds relative to woodland ponds regardless of origin, but no difference in survival between rearing environments. Laboratory exposure to road salt at relevant concentrations (0.6 ppt salinity) reduced larval activity and foraging behaviors, which may explain slower growth observed in the transplant experiment. Physiological assays of adult males migrating to breed revealed increased water retention in roadside populations. Further, these bloated males exhibited elevated resting plasma corticosterone levels and reduced capacity to secrete corticosterone when stimulated. Potential fitness consequences, such as reduced longevity and fecundity post metamorphosis through adulthood, of the roadside habitat could affect wood frog demography. Taken together, we provide evidence that the conditions experienced in the roadside environment pose challenges across life stages that have implications for persistence if populations are challenged with further stressors.

Incorporating evolutionary insights to improve ecotoxicology for freshwater species

“…These effects include osmoregulatory disruption (Karraker & Gibbs, 2011a), diminished growth and development (Johnson et al, 2015), increased malformations and disease susceptibility (Brady, 2013;Hopkins, French, & Brodie, 2013;Karraker & Ruthig, 2009), and behavioral changes (Hall et al, 2017), all of which can influence fitness, community dynamics, and ecosystem function (Schuler et al, 2017;Van Meter & Swan, 2014).…”

Combined effects of salinity and infectious disease on Daphnia dentifera at multiple scales

“…; Hua & Pierce, 2013), and a range of invertebrates (including Simocephalus sp., Moina sp., Daphnia sp., and hemipterans; Arnér & Koivisto, 1993;Bos, Cumming, Watters, & Smol, 1996;Brock, Nielsen, & Crossle, 2005;Carbonell et al, 2016). Additionally, increased salinity can have numerous sub-lethal effects on freshwater individuals including decreased adult body size or growth (Hall & Burns, 2002;Hall et al, 2017), reduced fecundity (Martínez-Jerónimo & Martínez-Jerónimo, 2007), increased hatching time (Carbonell et al, 2016), and reduced average daily activity (Jones et al, 2017). The combination of lethal and sub-lethal effects on individuals can cascade through the food web, potentially altering species interactions.…”

Indicators of wood frog (Lithobates sylvaticus) condition in a suburbanizing landscape

“…, Brady , Hall et al. ) and examined the relationship between skeletal abnormalities and road proximity (Reeves et al. ).…”

“…For wood frogs, assessing larval responses may be appropriate as environmental conditions experienced during larval development may influence terrestrial stage morphology and performance (Berven 1990, Boes andBenard 2013). Larval wood frogs are sensitive to pool conditions that can be influenced by nearby vegetation and land use (Skelly et al 2002, Watkins and Vraspir 2006, Karraker et al 2008, and their survival may decline with road salt (Sanzo and Hecnar 2006, Karraker et al 2008, Hall et al 2017) and herbicide contamination (Relyea 2012) and light pollution (Perry et al 2008). Few studies have examined the effects of natural and suburban-associated land cover types on amphibian larvae.…”

“…Few studies have examined the effects of natural and suburban-associated land cover types on amphibian larvae. Some studies have compared larval responses between forest and roadside pools (Karraker et al 2008, Brady 2013, Hall et al 2017) and examined the relationship between skeletal abnormalities and road proximity (Reeves et al 2008). Although Shepack et al (2017) experimentally introduced larvae into pools where breeding populations had been extirpated by urbanization and examined their survival and morphology, to our knowledge, no study has examined the relative influences of suburban-associated land cover types at multiple spatial scales on the larval survival and development of a vernal pool-breeding amphibian.…”