A new molecular isotopic toolkit to examine estuarine food webs and biogeochemistry: Compound specific isotope analyses of amino acids from aquatic and terrestrial plants of the Sacramento-San Joaquin Delta, California

Aquatic and terrestrial plant materials were collected from the Sacramento-San Joaquin Delta region. Carbon and nitrogen isotope values of individual amino acids and bulk materials were measured. Fifty-six specimens were collected from three locations within the Delta, two flooded islands, Mildred and Liberty Islands, as well as an adjacent terrestrial riparian habitat (Big Break Regional Shoreline). Specimens included terrestrial trees, shrubs, forbs, and grasses as well as floating, submerged, and emergent aquatic plants. Bulk leaf tissues were processed and the carbon and nitrogen isotope values of bulk tissues were measured following Tipple and Ehleringer, 2018 (Oecologia, 187, 1053-1075). Amino acids were hydrolyzed, derivatized, and isolated following Vokhshoori et al., 2013 (Marine Ecology Progress Series, 504, 59-72). Carbon and nitrogen isotope values of individual amino acids were measured following Vokhshoori et al., 2013 and Vokhshoori and McCarthy, 2013 (PLoS ONE, 9, 6, e98087), respectively. The purpose of this research was to create a novel molecular isotope toolset to increase the understanding of biogeochemistry and food web structure of the Sacramento-San Joaquin Delta's tidal wetlands and estuarine marshes.