A two-decade timeseries of baseline nutrient variations in the San Francisco Bay as recorded in nitrogen isotope values of amino acids from benthic filter-feeders

Amino acids were isolated from the muscle tissue of Potamocorbula amurensis, an invasive clam species, collected from two locations in the northern portion of the San Francisco Bay. Clam specimens were collected biannually in 1997, 2002, and from 2009-2017 at both locations. The nitrogen isotope values of individual amino acids were measured. Clam specimens were collected at USGS Sites 4.1 (Suisun Bay) and 8.1 (Carquinez Strait) in the San Francisco Bay and processed as described in Stewart et al. (2013; doi:10.3354/meps10503). Amino acids were hydrolyzed from P. amurensis, derivatized, and isolated following Vokhshoori et al. (2013; doi:10.3354/meps10746). Nitrogen isotope values of individual amino acids were measured following Vokhshoori and McCarthy, 2013 (doi:10.1371/journal.pone.0098087). The purpose of this study was to isolate variations in nutrient baseline over the twenty-year period following the arrival of invasive P. amurensis.