“…A second geochemical tracer is shell δ 13 C. In mollusks, shell δ 13 C records may be influenced by metabolic rate, trophic level, and reproductive condition, although the processes by which this influence occurs are not well understood [30,42,68,73,74,75,84,95]. Another major source of shell δ 13 C variation is changes in the δ 13 C of dissolved inorganic carbon (ΣCO 2 ) in seawater.…”