Vertically Resolved Plankton Metabolism From Autonomous Measurements in the Oligotrophic Ocean

We analyzed the in situ diel variability in dissolved O 2 from a compilation of quality‐controlled measurements collected with underwater gliders in the North Pacific Subtropical Gyre over a period spanning 14 years (2008−2021) and totaling >10,500 vertical profiles. We derived metabolic rates at different depths (0−110 m) from the diel oscillations in O 2 anomaly (ΔO 2 ), calculated here as the difference between instantaneous and 2‐day mean O 2 concentrations, using all assembled measurements. Depth‐integrated annual gross oxygen production and community respiration (CR) derived from this study (± standard deviation) were 87 ± 3 mmol O 2 m −2 d −1 and 89 ± 4 mmol O 2 m −2 d −1 , respectively. Gross oxygen production and CR decreased with depth and were lower in winter and spring than in summer and fall. Hourly rates of O 2 change indicated relatively constant nighttime respiration, but enhanced net O 2 production in the morning compared with the afternoon. We found that when ΔO 2 was calculated by subtracting the O 2 concentration at equilibrium (ΔO 2 ‐eq), as proposed in other studies, metabolic rates were overestimated by approximately 31%–36% in this oligotrophic oceanic region, due to diel variations in O 2 solubility driven by temperature oscillations. By demonstrating the reliability of depth‐resolved characterization of ocean metabolism, we hope to pave the way for the use of autonomous underwater observations to characterize primary productivity and respiration in understudied ocean regions, improving the spatiotemporal resolution provided by conventional methods.