DOC cycling in a temperate estuary: A mass balance approach using natural 14C and 13C isotopes

Abstract

We measured dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and their corresponding △14C and γ13C values in order to study the sources and fates of DOC in the York River Estuary (Virginia, U.S.A.). The d△14C and γ13C values of DOC and DIC at the freshwater end‐member indicate that during periods of moderate to high flow, riverine DOC entering the York was composed of decadal‐aged terrestrially organic matter. In nearly all cases, DOC concentrations exceeded conservative mixing lines and were therefore indicative of a net DOC input flux from within the estuary that averaged 1.2 µM L−1 d−1.