Ancient DNA Analysis and Stable Isotope Ecology of Sea Turtles (Cheloniidae) from the Gold Rush-era (1850s) Eastern Pacific Ocean

Abstract

Historical and archaeological evidence documents the importation of sea turtles from the eastern Pacific Ocean (Baja California) to California during the Gold Rush (1848–1855) and through the end of 19th century, but it is unknown whether these 19th century sea turtles foraged in similar ways to their modern counterparts. To identify the species of two Gold Rush-era sea turtle specimens recovered from archaeological deposits in San Francisco, California, we first analyze ancient DNA (aDNA). We then analyze carbon (δ13Ccol), nitrogen (δ15N), and hydrogen (δD) stable isotopes of bone collagen and carbon (δ13Cap) and oxygen (δ18Oap) stable isotopes of bone apatite to test if eastern Pacific sea turtle diets have changed over the past 160 years. Ancient DNA confirms that both archaeological specimens are green sea turtles (Chelonia mydas). The stable isotope values from the 19th-century specimens are statistically indistinguishable from the modern comparatives in both δ13Ccoland δ15N, suggesting that green sea turtle dietary intake has remained relatively unchanged since the 1850s. However, the values are unclear for δD and δ18Oapand require additional research.