Intensification of open-ocean oxygen depletion by vertically migrating animals

Bianchi, Daniele; Galbraith, Eric D.; Carozza, David A.; Mislan, K. A. S.; Stock, Charles A.

doi:10.1038/ngeo1837

Cited by 227 publications

(238 citation statements)

References 26 publications

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“…Where available, we used the direct DVM depth estimates from acoustic data from ref. 21. These regions are shown with dots in Fig.…”

Section: Dvm Association With Anoxic Watersmentioning

confidence: 99%

“…One of the few studies that targeted N excretion by migrators (30) combination of NH 4 + and dissolved organic nitrogen into the mesopelagic zone (200−300 m depth) equivalent to 20-30% of the sinking flux of organic N. The maximum values of these inputs were much larger, and reached between 2 and 3.5 times the inputs by particles. Average active transports around 15−35% of the total organic matter input are commonly reported across the ocean (21). The inclusion of micronekton, in particular myctophid and other vertically migrating fish, which are abundant but often undersampled, would increase these fractions (21,35).…”

Section: Dvm Effects On the N Cycle In Anoxic Watersmentioning

confidence: 99%

“…Average active transports around 15−35% of the total organic matter input are commonly reported across the ocean (21). The inclusion of micronekton, in particular myctophid and other vertically migrating fish, which are abundant but often undersampled, would increase these fractions (21,35).…”

Section: Dvm Effects On the N Cycle In Anoxic Watersmentioning

confidence: 99%

“…21. ADCP data provide continuous, depth-resolved views of migrating sound-scattering layers, which can be integrated with in situ net data to obtain a comprehensive picture of migrating animal communities (22)(23)(24).…”

Section: Dvm Association With Anoxic Watersmentioning

confidence: 99%

“…In many areas where a direct estimate from acoustic data was not possible, we estimated the DVM depth using a multiple linear regression against hydrographic data (oxygen, surface chlorophyll, mixed layer depth, and temperature) as described in ref. 21. We used the O 2 data from the monthly World Ocean Atlas (WOA) climatology (28), after applying the correction of ref.…”

Section: Dvm Association With Anoxic Watersmentioning

confidence: 99%

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Enhancement of anammox by the excretion of diel vertical migrators

Bianchi

Babbin

Galbraith

2014

Proc. Natl. Acad. Sci. U.S.A.

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Measurements show that anaerobic ammonium oxidation with nitrite (anammox) is a major pathway of fixed nitrogen removal in the anoxic zones of the open ocean. Anammox requires a source of ammonium, which under anoxic conditions could be supplied by the breakdown of sinking organic matter via heterotrophic denitrification. However, at many locations where anammox is measured, denitrification rates are small or undetectable. Alternative sources of ammonium have been proposed to explain this paradox, for example through dissimilatory reduction of nitrate to ammonium and transport from anoxic sediments. However, the relevance of these sources in open-ocean anoxic zones is debated. Here, we bring to attention an additional source of ammonium, namely, the daytime excretion by zooplankton and micronekton migrating from the surface to anoxic waters. We use a synthesis of acoustic data to show that, where anoxic waters occur within the water column, most migrators spend the daytime within them. Although migrators export only a small fraction of primary production from the surface, they focus excretion within a confined depth range of anoxic water where particle input is small. Using a simple biogeochemical model, we suggest that, at those depths, the source of ammonium from organisms undergoing diel vertical migrations could exceed the release from particle remineralization, enhancing in situ anammox rates. The contribution of this previously overlooked process, and the numerous uncertainties surrounding it, call for further efforts to evaluate the role of animals in oxygen minimum zone biogeochemistry.anammox | denitrification | oxygen minimum zone | diel vertical migration W ater column oxygen minimum zones (OMZs), where oxygen concentrations plummet to submicromolar levels (1), are responsible for approximately one-third of the total removal of fixed nitrogen from the oceans (2, 3). Several processes mediated by specialized prokaryotes convert fixed inorganic nitrogen (NH 4 + , NO 2 − , and NO 3 − ) to N 2 in anoxic waters. Canonical denitrification, consisting of dissimilatory NO 3 − reduction to NO 2 − (DNRN) followed by the further oxidation of organic matter with NO 2 − (the denitrification step), was long considered the dominant fixed N removal pathway in anoxic waters. Over the last decade, anammox has gained attention as a major sink of fixed N in nearly anoxic waters (O 2 < 10 mmol·m −3 ) (4, 5).Stoichiometric considerations would suggest a close coupling between denitrification and anammox (6, 7). Under anoxic conditions, the NH 4 + liberated by the remineralization of organic matter through DNRN and denitrification should accumulate in the water column because conventional (aerobic) nitrification cannot proceed. However, this accumulation is not observed in the cores of anoxic waters, where observed NH 4 + concentrations are generally much less than 1 mmol·m −3 (8). In these regions, oxidation of NH 4 + with NO 2 − by anammox is thought to be the major sink of NH 4 + (9). Given that no significant NH 4 + acc...

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“…Where available, we used the direct DVM depth estimates from acoustic data from ref. 21. These regions are shown with dots in Fig.…”

Section: Dvm Association With Anoxic Watersmentioning

confidence: 99%

Section: Dvm Effects On the N Cycle In Anoxic Watersmentioning

confidence: 99%

Section: Dvm Effects On the N Cycle In Anoxic Watersmentioning

confidence: 99%

Section: Dvm Association With Anoxic Watersmentioning

confidence: 99%

Section: Dvm Association With Anoxic Watersmentioning

confidence: 99%

See 3 more Smart Citations

Enhancement of anammox by the excretion of diel vertical migrators

Bianchi

Babbin

Galbraith

2014

Proc. Natl. Acad. Sci. U.S.A.

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Major role of the equatorial current system in setting oxygen levels in the eastern tropical Atlantic Ocean: A high-resolution model study

Duteil

Schwarzkopf

Böning

et al. 2014

Geophys. Res. Lett.

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Understanding the causes of the observed expansion of tropical ocean's oxygen minimum zones (OMZs) is hampered by large biases in the representation of oxygen distribution in climate models, pointing to incorrectly represented mechanisms. Here we assess the oxygen budget in a global biogeochemical circulation model, focusing on the Atlantic Ocean. While a coarse (0.5°) configuration displays the common bias of too large and too intense OMZs, the oxygen concentration in an eddying (0.1°) configuration is higher and closer to observations. This improvement is traced to a stronger oxygen supply by a more realistic representation of the equatorial and off-equatorial undercurrents, outweighing the concurrent increase in oxygen consumption associated with the stronger nutrient supply. The sensitivity of the eastern tropical Atlantic oxygen budget to the equatorial current intensity suggests that temporal changes in the eastward oxygen transport from the well-oxygenated western boundary region might partly explain variations in the OMZs.

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Diel vertical migration of zooplankton at the S1 biogeochemical mooring revealed from acoustic backscattering strength

2016

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We examined the diel vertical migration of zooplankton by using the backscatter strength obtained from moored acoustic Doppler current profilers at mooring site S1 in the North Pacific subtropical gyre. There was seasonal variability in the vertical distribution and migration of the high‐backscatter layers in that they became deeper than the euphotic zone (<100 m) in winter and were confined above this depth in other seasons. Seasonal changes in daylight hours also affected the timing of the diel migration. We found that lunar cycles affected vertical distributions of zooplankton near the surface by changing the light intensity. Physical events, such as mixed‐layer deepening and restratification and the passage of a mesoscale eddy, also affected zooplankton behavior possibly by changing food environment in the euphotic zone. Since the comparison with net samples indicated that the backscatter likely represents the bulk biomass, the accuracy of biomass estimates based on net samples could be influenced by the high temporal variability of zooplankton distributions.

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Intensification of open-ocean oxygen depletion by vertically migrating animals

Cited by 227 publications

References 26 publications

Enhancement of anammox by the excretion of diel vertical migrators

Enhancement of anammox by the excretion of diel vertical migrators

Major role of the equatorial current system in setting oxygen levels in the eastern tropical Atlantic Ocean: A high-resolution model study

Diel vertical migration of zooplankton at the S1 biogeochemical mooring revealed from acoustic backscattering strength

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