Methodology: Porewater sulfide concentrations were determined photometrically, and sulfate concentrations were determined by ion chromatography.

Sampling and Analytical Procedures: This porewater sulfate and sulfide dataset consists of results obtained at the Max-Planck-Institute for Marine Microbiology in Bremen, Germany. The experimental procedures are listed here separately by institution. The sampling site names in the data table are based on Teske et al. 2016 and Teske et al. 2021.

For analyses at the Max-Planck Institute for Marine Microbiology (Gunter Wegener), intact sediment cores were sampled using the Rhizons (Rhizosphere Research Products, Wageningen, NL) as described previously (Seeberg-Elversfeldt et al., 2005). The overlying water was removed from the cores and holes were drilled into designated sediment sampling depths. Pretreated Rhizons were injected and suction was applied with syringes for approx. 30 min. The rhizome depths are given in the sample tables. For sulfide analysis, 1 ml porewater subsamples were fixed with 0.1 ml of 0.1 M zinc acetate solution to preserve the sulfide as zinc sulfide until analysis by the methylene blue method (Cline 1969). The same fixed porewater sample was used for measuring sulfate concentrations using ion chromatography (Metrohm 930 Compact IC flex oven, Metrosep A PCC HC/4.0 preconcentration column, and Metrosep A Supp 5 Guard/4.0 chromatography column). The concentrations of ammonia, phosphate, and silicate were determined from porewater using a continuous flow nutrient analyzer (QuAAtro39; Seal Analytical) as published previously (Grasshoff et al., 2009).

Known Problems/Issues: Problems with Mexican customs and the agent used by WHOI at the time have resulted in limited availability of sampling gear and sampling vials on the ship. Transport problems during the return trip have caused sample losses among the porewater samples, which are evident in occasional gaps in porewater profiles or short profiles.

Note that the Alvin frame grabber was not turned on during dive 4862; therefore positions and depth are approximations.