Amino acid nitrogen isotopic analysis of aquatic and terrestrial plants from an estuarine delta

Aquatic and terrestrial plants were collected from the Sacramento-San Joaquin River Delta. Nitrogen isotope values of bulk plant tissue and individual amino acids were measured. Fifty-six specimens from thirty-nine native, introduced and invasive species were collected. Growth forms and habits include trees, shrubs, forbs, and grasses as well as floating, submerged, and emergent aquatic plants. Bulk tissues were processed and the nitrogen isotope values were measured following Tipple and Ehleringer, 2018 (Oecologia, 187, 1053-1075). Amino acids were hydrolyzed, derivatized, and the carbon isotope values of individual amino acids were measured following Vokhshoori and McCarthy, 2013 (PLoS ONE, 9, 6, e98087). The purpose of this study was to assess trophic discriminate factors at the base of estuarine systems with multiple primary producers. This study provides an authentic dataset of primary producers for trophic position assessments in estuarine and mixed terrestrial-marine source environments.