2020 data:
These pore water data were obtained from sediment cores collected at five different stations on the Louisiana Shelf on the Northern Gulf of Mexico during the week of November 3-6, 2020 using an MC-800 multi-corer. These stations extend from the middle of the shelf offshore from Cocodrie, LA to the mouth of the Mississippi River North West Pass. All cores were processed within a few hours after collection. The field sampling was conducted during R/V Savannah cruise SAV-20-07.

2021 and 2022 data:
In July 2021, the pore water data were obtained from sediment cores collected with a MC-800 multi-corer at ten different stations on the Louisiana Shelf and slope in the Northern Gulf of Mexico during July 16-26, 2021. These stations span two transects, one from the middle of the shelf offshore from Cocodrie, LA to the mouth of the Mississippi River's South West Pass, and another one from North West Pass of the Mississippi River mouth to the south, across the slope. A single station (St. 15) was also sampled on the eastern side of the second transect in the transition from the shelf break to the mid-slope.

In October 2021, the pore water data were obtained from sediment cores collected with a MC-800 multi-corer at twelve different stations on the Louisiana Shelf and slope in the Northern Gulf of Mexico between October 25 and November 10, 2021. These stations extend from the middle of the shelf offshore from Cocodrie, LA to the mouth of the Mississippi River's South West Pass. Two stations (St. 15 and St. 12) were also sampled on a second transect from the shelf break to the slope southeast of the Bird's Foot.

In spring 2022, the pore water data were obtained from sediment cores collected with a MC-800 multi-corer at ten different stations on the Louisiana Shelf and slope in the Northern Gulf of Mexico during April 9-20, 2021. These stations span two transects, one from the middle of the shelf offshore from Cocodrie, LA to the mouth of the Mississippi River's South West Pass, and another from South West Pass of the Mississippi River mouth to the south, across the slope. Two stations (St. 15 and St. 12) were also sampled on a second transect from the shelf break to the slope southeast of the Bird's Foot.

In summer 2022, the pore water data were obtained from sediment cores collected with a MC-800 multi-corer at eleven different stations on the Louisiana Shelf and slope in the Northern Gulf of Mexico during July 9 -23, 2022. These stations span two transects, one from the middle of the shelf offshore from Cocodrie, LA to the mouth of the Mississippi River's South West Pass, and another from South West Pass of the Mississippi River mouth to the south, across the slope. Two stations (St. 15 and St. 12) were also sampled on a second transect from the shelf break to the slope southeast of the Bird's Foot.

All data:
The pore waters were first extracted by slicing sediment cores of < 25 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).