Dataset: pH microsensor profiling conducted alongside the destructive sampling of Chesapeake Bay sediments during incubation experiments at Horn Point Lab

The source material was collected from Chesapeake Bay (38.55505 N, 76.42794 W) (mesohaline), water column depth 26 meters, sediment horizon 0-10 centimeter below sea floor.

Incubation conditions: 16 degrees Celsius, S=15.5, dark, aerated.

Incubation Set-up: Sediments were homogenized and packed into polycarbonate core liners, sealed with a stopper at the bottom, and open to aerated aquarium water at the top. In a subset of cores, a polycarbonate filter (pore size 0.2 microns) was secured at 0.5 cm depth, to prevent downward growth of cable bacteria in these treatments. Sediments were incubated for up to 46 days. At 6 time points, microsensor profiles were measured, followed by destructive sampling.

Porewater extraction: Sediments were sectioned at 0.5 cm depth increments in an anaerobic glove bag under nitrogen atmosphere. Porewaters were separated by centrifugation (3500 rpm for 10 minutes), and filtered (0.2 micron) and aliquoted in the anaerobic glove bag. Samples for ferrous iron measurements were preserved with trace-metal grade nitric acid (final pH < 2).

Microsensor Profiling: High-resolution microsensor profiling of oxygen (O2), pH, and hydrogen sulfide (H2S) was performed on replicate sediment cores with 1 profile made per sediment core per analyte, using commercial microsensors operated with a motorized micromanipulator (Unisense A.S., Denmark). Oxygen sensor data were calibrated with a 2-point calibration using air-saturated water and anoxic zone of sediments. pH sensors were calibrated with a 3-point NBS buffer calibration. Sulfide (SumH2S) was calibrated with 5-point calibration using NaS2 (0-300 micromolar), and corrected with pH at the corresponding depth. Detailed methodology is given in Malkin et al. 2014.