Depth profiles of pore water constituents from sediment cores collected on the Louisiana Shelf of the Northern Gulf of Mexico during 2020, 2021, and 2022 on R/V Savannah cruises SAV-20-07, SAV-21-25, SAV-21-24, SAV-22-06, and SAV-22-11

This data set reports depth profiles of pore water concentrations of dissolved inorganic carbon (DIC), orthophosphate (PO43-), ammonium (NH4+), total alkalinity (TA), carbon isotopic fractionation of DIC (13C-DIC), dissolved manganese (Mnd), dissolved calcium (Cad), reduced iron (Fe(II)), total dissolved Fe (Fed), and dissolved Fe(III) (Fe(III)d) by the difference of total dissolved Fe and Fe(II). Data were collected during five R/V Savannah cruises in fall 2020, summer and fall 2021, and fall and spring 2022. On each cruise pore water data were obtained from sediment cores collected with an MC-800 multi-corer at multiple stations. Cruise IDs were: SAV-20-07, SAV-21-25, SAV-21-24, SAV-22-06, SAV-22-11.

All cores were processed within a few hours after collection. The pore waters were first extracted by slicing sediment cores of < 40 centimeters (cm) long and centrifugation of the pore waters under N2 atmosphere to avoid air contamination. Pore waters were then immediately filtered through 0.22-micrometer (um) PSE syringe filters under N2 atmosphere and either analyzed immediately onboard (Fe speciation, orthophosphate, DIC), preserved acidified with hydrochloric acid at 4 degrees Celsius (Cad, Mnd), frozen (ammonium), or preserved at 4 degrees Celsius after addition of HgCl2 (TA) until analysis.  In addition, samples for TA and carbon isotopic analyses were preserved in glass bottles, whereas other samples were preserved in polypropylene containers.

DIC was analyzed by flow injection analysis (Hall and Aller, 1992), orthophosphate, ammonium, and Fe speciation by spectrophotometry (Murphy and Riley, 1962; Strickland and Parsons, 1972; Stookey, 1970), TA by Gran titration (Gran, 1952), the carbon isotopic signature by isotope ratio mass spectrometry (Wang et al, 2018), and Mnd and Cad by ICP-MS (Magette et al., 2025 In preparation).