Mean individual I/Ca ratios, number of measurement spots (n) and errors for recent benthic foraminifera at different sampling sites of the Peruvian oxygen minimum zone. The number of the specimen (#) is used to distinguish between different specimens from the same sample. The heterogeneity is defined in section 2.6 od Glock et al. (2016). Cleaned (yes/no) refers if the sample had undergone an oxydative cleaning procedure as described in Glock et al. (2016). In addition, core locations and bottom water oxygen concentrations (O2BW) are listed. I/Ca ratios were measured with SIMS following the protocols described in Glock et al. (2016). Samples were taken during RV Meteor cruises M77/1 in the framework of the SFB754.