Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

This dataset comprises results of respirometry experiments conducted at sea. Experimental animals were collected using either a modified tucker trawl or MOCNESS. Metabolic rates and critical oxygen pressures were measured using published methods (Birk et al., 2018; 2019; Wishner et al., 2018; Seibel et al., 2021). Briefly, individual specimens were placed in darkened sealed chambers filled with 0.2 μm filtered seawater that had been treated with antibiotics (25 mg/L each of streptomycin and actinomycin) to minimize bacterial respiration. The ratio of chamber size to body mass was approximately 1:20. Oxygen content was continuously monitored using Pyroscience Firesting or Presens oxygen meters and fiber optic probes with oxygen-sensitive fluorescent spots. Oxygen meters were calibrated with air-saturated seawater and concentrated Na2SO3 solution (PO2 = 0). Chamber water was mixed with magnetic stirrers (Cole-Parmer Immersible Stirrer EW-04636-50) to ensure homogenous oxygen levels throughout the chamber. Oxygen consumption rates (MO2) were calculated from the slope of PO2 over time. Only linear regressions with an R2 > 0.8 were included. The median MO2 value from non-hypoxic oxygen levels was calculated for each individual. The Pcrit for each individual was calculated using three metrics, including the traditional "breakpoint" method, the "sub-prediction interval (sub-PI)" and the alpha-method.

Data Processing:
Data were processed in R using published tools from Birk (2020). Calculated values of critical oxygen partial pressure (Pcrit) are compared among methods that use different bin sizes and/or definitions of Pcrit, as described below.

Pcrit_fixed_width: breakpoint Pcrit using 10 minute bins if total duration < 1000 minutes and 60 minute bins if total duration > 1000 minutes.

Pcrit_sub_reg: sliding bin width based on PO2. Pcrit defined as intersection of conforming line and lower 95% prediction interval bound. Outliers removed.

Pcrit_slide_width: sliding bin width based on PO2. Pcrit defined as breakpoint.

Pcrit_on_duration: breakpoint Pcrit using PO2 vs duration (biased low).

Pcrit_sub_reg_corrected: Plate Reader only - applies to runs where Pcrit was adjusted to compensate for the poor factory calibration of sensor dots.

BCO-DMO Processing:
- replaced "NA" with "nd" (no data);
- renamed fields to comply with BCO-DMO naming conventions;
- converted date to YYYY-MM-DD format;
- changed year of 2027 to 2017 on line 286;
- replaced values of "15? 18?" in the Temp column with "nd".

Description from NSF award abstract:
With climate change, ocean temperatures are expected to increase which in turn will reduce oxygen availability and increase metabolic oxygen demand in marine organisms. The investigators will conduct shipboard physiological experiments for various marine organisms and determine their distributions in relation to environmental conditions within an oxygen minimum zone (OMZ) in the Eastern Pacific Ocean. The goal will be to model and map a Metabolic Index (MI) to predict how vertical and horizontal distributions for these species might change throughout the world's oceans in the future. The MI is defined as the ratio between environmental oxygen supply and temperature-dependent oxygen demand. Oxygen supply includes both the environmental oxygen concentration across a habitat range and the physiological features of organisms that facilitate oxygen uptake, such as gills and circulatory systems. Thus, the MI will integrate measured tolerance and environmental exposure to low oxygen with environmental data. The investigators will measure tolerance to low oxygen, focusing on under-studied organisms, including the effect of temperature and organism size. They will sample along a natural gradient in oxygen content south of the California Current in the Eastern Pacific. The science team and a videographer will develop a blog about deep-sea biology and climate change using web-based and video technologies. Four graduate students will be funded on this project, and in conjunction with a recently developed course in pelagic ecology, several undergraduates will have the opportunity to participate in seagoing research.

This research fills a critical need for a physiology-based metric that can be used to predict changing marine communities as the oceans warm and hypoxic zones expand. Modern OMZs are extensive and characterized by deep-water (300-800 m) oxygen partial pressures lethal to most marine organisms, yet thriving communities exist there. Climate change is predicted to further deplete oxygen. The investigators will model and map a Metabolic Index (MI) for diverse marine species to help predict how in vertical and horizontal distributions of species may change throughout the world's oceans in the future. The MI will derive oxygen supply and demand data from published and planned measurements of the minimum environmental partial pressure of oxygen to which individual species are exposed (based on their distributions in the water column) and the minimum requirements to support routine aerobic metabolic demand (from shipboard respiration measurements of individuals). During research cruises in the Eastern Pacific along a gradient of OMZ intensity, the investigators will conduct shipboard physiological measurements to determine metabolic demand for understudied mesozooplankton and gelatinous taxa and determine the size- and temperature dependence for diverse species for incorporation into the MI. Vertically-stratified net sampling and in situ photography will identify and characterize unique OMZ community features, such as the lower oxycline biomass peak present in some OMZs and the oxygen-dependence of day and night habitat depths for vertically-migrating species. The MI will be mapped using climatological data to both test and generate hypotheses about the response of oceanic communities to climate change. In preliminary analysis, the MI suggests a metabolic constraint at a MI of ~2 that may act to limit vertical and horizontal habitat ranges.