High-frequency oxygen and temperature data from a mesopelagic POC-degradation experiment in the Southeast Pacific oxygen minimum zone

This dataset contains high-frequency dissolved oxygen (O₂) and temperature measurements from a shipboard incubation experiment conducted with mesopelagic seawater collected within the Southeast Pacific oxygen minimum zone off central Chile during the DIZMO cruise in October 2025. The experiment investigated respiratory responses following the addition of fresh, diatom-derived particulate organic carbon (POC).

Mesopelagic seawater was collected at 210 m depth at Station 8 (33.080° S, 72.860° W) and filtered through a 0.8-µm polycarbonate filter. Six experimental bottles received a pulse of diatom-derived POC, while unamended bottles served as controls. Dissolved O₂ was measured using optical sensor spots connected to a four-channel FireSting-O₂ meter (PyroScience).

The dataset includes the high-frequency O₂ records for experimental Bottles 1–4 during the main monitoring period, as well as the shorter records obtained after the O₂ sensors were transferred to Bottles 5 and 6 and Control 1 at approximately 60 h of incubation. The Control 1 record is included for completeness but was not used to estimate a control O₂-consumption rate because no continuous O₂ record was available for the control over the incubation. Temperature records corresponding to both measurement periods are also provided.

O₂ measurements were recorded at 10-s intervals, whereas temperature was recorded at 30-s intervals. Time in each file represents elapsed time from the beginning of the corresponding instrumental recording period. O₂ concentrations are reported in µmol kg⁻¹ and temperature in °C.

Bottles 5 and 6 were not continuously monitored before sensor transfer. Consequently, their earlier O₂ trajectories used in the associated manuscript were reconstructed statistically and should not be interpreted as directly measured O₂ data. The files deposited here contain the instrumental observations rather than reconstructed O₂ trajectories.

These data support the manuscript “Rapid mesopelagic respiration following a pulse of diatom-derived carbon in a Southeast Pacific oxygen minimum zone” by Díaz-Rosas et al., submission for consideration in Biogeosciences.