Ocean deoxygenation and zooplankton: Very small oxygen differences matter

Wishner, Karen F.; Seibel, Brad A.; Roman, Christopher; Deutsch, Curtis; Outram, Dawn M.; Shaw, C. Tracy; Birk, Matthew A.; Mislan, K. A. S.; Adams, Thomas J.; Moore, D.C.; Riley, Stephen C.

doi:10.1126/sciadv.aau5180

Cited by 108 publications

(135 citation statements)

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“…The theoretical arguments, if true, may warrant the abandonment of P crit . However, contrary to Dr Wood's claims, across species, P crit is strongly correlated with the environmental O 2 level to which species are exposed and is therefore ecologically relevant (Childress and Seibel, 1998;Mandic et al, 2009;Wishner et al, 2018). P crit is also correlated with multiple steps of the O 2 transport cascade, from gill surface area through haemoglobin P 50 to mitochondrial P 50 (Childress and Seibel, 1998;Lau et al, 2017;Mandic et al, 2009), and is a sensitive measure of an animal's overall ability to extract O 2 because altering physiological traits along the cascade can change P crit .…”

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confidence: 82%

Don't throw the fish out with the respirometry water

Regan

Mandic

Dhillon

et al. 2019

Journal of Experimental Biology

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Dr Wood's Commentary (Wood, 2018) provides six reasons to question the usefulness of P crit and proposes alternative ṀO 2 versus P O2 analyses as its replacement. While we agree with some of Dr Wood's arguments, we feel that none of them warrant abandoning P crit , especially in favour of his proposed alternatives, which provide different information than P crit . A more useful way forward would involve (1) clearly defining P crit , to avoid misinterpretation, and (2) standardizing (or at least clearly describing) the methods used to determine and report P crit , to optimize its comparative value. This topic demands further discussion because Dr Wood's conclusion could have unwarranted influence on how future hypoxia research is conducted and past hypoxia research is interpreted.Dr Wood's arguments are either theoretical (reasons 3-6) or methodological (reasons 1, 2). The theoretical arguments, if true, may warrant the abandonment of P crit . However, contrary to Dr Wood's claims, across species, P crit is strongly correlated with the environmental O 2 level to which species are exposed and is therefore ecologically relevant (Childress and Seibel, 1998;Mandic et al., 2009;Wishner et al., 2018). P crit is also correlated with multiple steps of the O 2 transport cascade, from gill surface area through haemoglobin P 50 to mitochondrial P 50 (Childress and Seibel, 1998;Lau et al., 2017;Mandic et al., 2009), and is a sensitive measure of an animal's overall ability to extract O 2 because altering physiological traits along the cascade can change P crit . For example, anatomical restructuring of the gill to favour O 2 diffusion [e.g. reducing gill epithelial thickness through seawater acclimation in sculpins (Henriksson et al., 2008); increasing lamellar surface area through hypoxia acclimation in crucian carp (Sollid et al., 2003)] can lower P crit . These relationships between P crit and plastic traits along the O 2 transport cascade clearly reflect the physiological relevance of P crit and indicate that P critespecially when it shifts with acclimationdoes indeed represent the P O2 at which O 2 uptake becomes constrained. Therefore, contrary to reason 6, P crit per se does carry biologically relevant information. Hence, P crit remains a useful tool for understanding hypoxic performance because it allows for predictive statements.Much of Dr Wood's reasoning centres on the over-interpretation of P crit . P crit does not necessarily quantify an animal's overall hypoxia tolerance (the product of some combination of aerobic metabolism, anaerobic metabolism and metabolic depression; reason 5), reveal what biological processes the O 2 consumed at P crit is supporting (reason 4), or indicate the onset P O2 of enhanced glycolytic reliance (reason 4) or metabolic depression (reason 5).These ideas have long been excluded from the definition of P crit . Simply, P crit defines the lowest water P O2 at which the animal can maintain some benchmark ṀO 2 state (e.g. ṀO 2,std , the ṀO 2 of an inactive and post-absorptive ectotherm...

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confidence: 82%

Don't throw the fish out with the respirometry water

Regan

Mandic

Dhillon

et al. 2019

Journal of Experimental Biology

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“…The availability of dissolved O 2 is a key metabolic constraint for marine ecosystems, restricting habitat of aerobic animals (Wishner et al, 2018) while favoring anaerobic microbial metabolisms when O 2 concentrations are low (Kondo & Moffett, 2013;Lam et al, 2009;Penn et al, 2016;Ward et al, 2009). The large-scale O 2 distribution of the ocean interior is driven by the subduction of waters from the mid-latitude surface ocean and the subsequent consumption of O 2 via respiration of organic matter.…”

Section: Introductionmentioning

confidence: 99%

Ventilation Pathways for the North Pacific Oxygen Deficient Zone

Margolskee

Frenzel

Emerson

et al. 2019

Global Biogeochemical Cycles

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Oxygen deficient zones (ODZs) in the tropical ocean exert a profound influence on global biogeochemical cycles, but the factors that regulate their long‐term structure and sensitivity to oceanic change remain poorly understood. We analyzed hydrographic observations and a high‐resolution physical/biogeochemical model to diagnose the primary pathways that ventilate the tropical Pacific ODZs. Historical and recent autonomous observations reveal pronounced and widespread O2 peaks, termed secondary oxygen maxima (SOMs), within the depths of the broader O2 minimum layer, especially at the equatorward edge of both northern and southern ODZs. In the northern ODZ, Lagrangian particle tracking in an eddy‐permitting numerical model simulation attributes these features to intrusions of the Northern Subsurface Countercurrent along the equatorial edge of the ODZ. Zonal subsurface jets also ventilate the poleward edge of the northern ODZ but induce a smaller O2 flux and do not yield detectable SOMs. Along the ODZ's eastern boundary, oxygenation is achieved by the seasonal cycle of upwelling of low‐O2 water onto the continental shelf, followed by downwelling of O2‐replenished near‐surface waters back into the ODZ. Waters entering the northern Pacific ODZ originate from the extratropics in both hemispheres, but two thirds are from the Southern Hemisphere and arrive later and with a wider range of transit times. These results suggest that predicting future changes in the large Pacific ODZs will require a better understanding of the climate sensitivity of the narrow zonal jets and seasonal dynamics of coastal upwelling that supply their O2.

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“…While reduced oxygen concentration at constant PO 2 will not result in reduced metabolic rate (e.g. in most shallow and terrestrial habitats), reduced oxygen partial pressure at depth or due to eutrophication will result in a precise decrement in MMR (1/P crit-max ; ~5% kPa −1 for most shallow-living and terrestrial species), with consequences for vertically mobile and mesopelagic species( 39 ).…”

Section: Discussionmentioning

confidence: 99%

“…A low P crit is usually interpreted as an indication of hypoxia tolerance and, across large PO 2 gradients, P crit is roughly correlated with habitat PO 2 ( 17, 39, 40 ). However, P crit must also respond to selection for an increase in aerobic scope, via increased MMR or reduced BMR (eq.…”

Section: Mainmentioning

confidence: 99%

Oxygen supply capacity in animals evolves to meet maximum demand at the current oxygen partial pressure regardless of size or temperature

Seibel

Deutsch

2019

Preprint

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AbstractPhysiological oxygen supply capacity is associated with athletic performance and cardiovascular health and is thought to cause hypometabolic scaling in diverse species. Environmental oxygen is widely believed to be limiting of metabolic rate and aerobic scope, setting thermal tolerance and body size limits with implications for species diversity and biogeography. Here we derive a quantifiable linkage between maximum and basal metabolic rate and their temperature, size and oxygen dependencies. We show that, regardless of size or temperature, the capacity for oxygen supply precisely matches the maximum evolved demand at the highest persistently available oxygen pressure which, for most species assessed, is the current atmospheric pressure. Any reduction in oxygen partial pressure from current values will result in a decrement in maximum metabolic performance. However, oxygen supply capacity does not constrain thermal tolerance and does not cause hypometabolic scaling. The critical oxygen pressure, typically viewed as an indicator of hypoxia tolerance, instead reflects adaptations for aerobic scope. This simple new relationship redefines many important physiological concepts and alters their ecological interpretation.One sentence summary: Metabolism is not oxygen limited

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Ocean deoxygenation and zooplankton: Very small oxygen differences matter

Abstract: Novel midwater ocean sampling shows that physiology dictates zooplankton distributions in submesoscale low oxygen features.

Cited by 108 publications

References 84 publications

Don't throw the fish out with the respirometry water

Don't throw the fish out with the respirometry water

Ventilation Pathways for the North Pacific Oxygen Deficient Zone

Oxygen supply capacity in animals evolves to meet maximum demand at the current oxygen partial pressure regardless of size or temperature

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