Watershed concentrations of dissolved inorganic carbon, dissolved organic carbon, and particulate organic carbon in the York River Estuary sampled in 2019-2021.

We measured the concentrations of dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and particulate organic carbon (POC) at four stations in the Pamunkey and Mattaponi Rivers, the main freshwater sources to the York River Estuary (YRE), approximately monthly from April 2019 to December 2019, and on selected dates during 2020 and 2021 to capture a wide range of discharge conditions. Sampling locations included the USGS non-tidal gauging stations above the fall line on each river, and a station in the tidal fresh region of each river, approximately halfway between the gauges and the confluence of the two rivers at the head of the YRE. Samples were collected to assess variation in each carbon species with freshwater discharge, changes in concentrations in the tidal fresh zone of the estuary, and carbon loading to the YRE.