Graduate Thesis Or Dissertation


Effects of Secondary Salinization on Three Coastal Breeding Amphibians in Oregon: Taricha granulosa, Hyliola regilla, and Rana aurora Public Deposited

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  • Due to threats of secondary salinization caused by increased saltwater intrusion upstream associated with climate change, this thesis examines how salinity affects the development and oviposition site selection habits of three Oregon coastal breeding amphibians, the Roughskin Newt (Taricha granulosa), the Northern Red-legged Frog (Rana aurora) and the Pacific Treefrog (Hyliola regilla). Often thought of as freshwater species, I conducted laboratory salt tolerance experiments at 0.1, 1, 2, 5, and 10 ppt and field surveys at coastal wetland sites with these species in order to determine how they are affected by salinity. Laboratory experiments indicated that the Pacific Treefrog may have a salt tolerance that falls between 2-5 ppt, and the Northern Red-legged Frog may have salt tolerance beyond 5 ppt. These species both experienced sublethal developmental effects from salinity concentrations as well as lethal effects from heightened salinity treatments. Field surveys corroborated these results and suggest that the Northern Red-legged frog can tolerate salt and may have chemosensory ability to distinguish between brackish and fresh waters, while the Pacific Treefrog did not display any ability to distinguish between these two. While laboratory experiments were not conducted on the Roughskin Newt, field surveys indicated that they showed behavioral preference for fresh water and a possible chemosensory ability to detect water salinity. These results suggest that all study species may experience population declines in the future associated with secondary salinization.
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