Dataset: Water column dissolved organic carbon (DOC) reactivity along the York River Estuary (YRE) from surface samples collected in October 2018 and February, April, and July 2019

These data represent concentrations of dissolved organic carbon (DOC) in units of micromoles per liter (µM) from samples collected during dark bottle incubations of estuarine surface water. These data were collected as part of a study that evaluated spatiotemporal and environmental controls on water column DOC reactivity along the York River Estuary (YRE), a temperate microtidal sub-estuary of the Chesapeake Bay in southeastern Virginia. The data were also collected as part of the larger, NSF-funded project (NSF BIO-OCE #1737258) entitled "Alteration of carbon fluxes by intense phytoplankton blooms in a micro tidal estuary."

During October 2018 and February, April, and July 2019, triplicate surface water samples (<0.5 meters below the surface) were collected from three locations along the YRE estuarine salinity gradient, referred to as upper (37°28'48.4"N 76°45'34.2"W), middle (37°20'13.2"N 76°38'24.0"W), and lower (37°15'06.5"N 76°26'34.4"W). Samples were collected using a DataFlow pump intake system. Surface water samples were dispensed directly into 2-liter (L) polycarbonate bottles and kept in the dark on ice for transport back to the Virginia Institute of Marine Science (VIMS). Prior to sample collection, all glassware and glass-fiber filters were combusted (500 degrees Celsius (°C) for 4 hours), and polyethersulfone (PES) filters and polycarbonate collection bottles were acid-rinsed (10% HCl).

Upon return to VIMS, the 2L water samples were immediately filtered sequentially through 0.7-micrometer (μm) (Whatman GF/F) and 0.2 μm (Sterlitech PES) filters into borosilicate glass bottles. The 0.2 μm filtrate was inoculated with the 0.7 μm filtrate (1% v/v) for microbial degradation experiments. The samples were incubated in the dark at in situ York River water temperature and sub-sampled at the onset of the experiment (T0), one day following onset (T1), and weekly for 28 days thereafter (T7, T14, T21, T28). Subsamples for DOC were filtered (0.45 µm PES) and frozen (-20°C) until analyses were completed within four weeks of collection. Concentrations of DOC ([DOC]) at each time point were measured using high-temperature combustion oxidation (Shimadzu TOC-V organic carbon analyzer).