Acoustic Observation of Living Organisms Reveals the Upper Limit of the Oxygen Minimum Zone

Bertrand, Arnaud; Ballón, Michael; Chaigneau, Alexis

doi:10.1371/journal.pone.0010330

Cited by 131 publications

(141 citation statements)

References 43 publications

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“…4). Acoustic backscattering of a fauna unable to penetrate hypoxic waters delineates the HBL in the southern CC, much as backscattering from Peruvian anchoveta Engraulis ringens marks the shallower HBL at 50 to 100 m depth off Peru (Bertrand et al 2010). The aggregation of the mesopelagic micronekton within the HBL in the CC suggests that this fauna descends as deeply as possible to avoid visually orienting predators, while avoiding the effects of hypoxia.…”

Section: Discussionmentioning

confidence: 98%

Impact of declining intermediate-water oxygen on deepwater fishes in the California Current

Koslow¹,

Goericke²,

Lara‐Lopez³

et al. 2011

Mar. Ecol. Prog. Ser.

183

188

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Although declining oxygen concentration has been reported for the oxygen minimum zones (OMZs) of the tropical oceans and the North Pacific Ocean, consistent with model predictions of the effects of global warming, its ecological impacts are poorly understood. We report the apparent impact of declining oxygen on midwater fishes within the OMZ of the southern California Current (CC). Principal component analysis of the California Cooperative Oceanic Fisheries Investigations (CalCOFI) ichthyoplankton time series from 1951 to 2008 indicates that the dominant temporal pattern (principal component 1 [PC1]) represents the marked decline of the region's mesopelagic fishes during periods of reduced oxygen. Of the 27 taxa with loadings > 0.5 on PC1, 24 were mesopelagic. PC1 was strongly correlated with intermediate-water oxygen concentrations (r = 0.75, p < 0.05), which were about 20% lower in the past decade and the 1950s than in the period from 1970 to 1995. The abundance of mesopelagic fishes represented by PC1 was reduced, on average, by 63% between periods of high and low oxygen concentrations. We hypothesize that the underlying mechanism is the shoaling of the hypoxic boundary layer during periods of reduced oxygen, which renders the mesopelagic fauna more vulnerable to visually orienting predators. The mesopelagic fish fauna provides a vital trophodynamic link between the marine plankton and many higher predators. The decline of deepwater fish populations has profound implications for commercial fisheries, marine food webs and marine conservation: climate models predict a 20 to 40% decline in global deepwater oxygen concentrations over the coming century.KEY WORDS: Oxygen · Mesopelagic fishes · Oxygen-minimum zone · Climate change · California CurrentResale or republication not permitted without written consent of the publisher

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Section: Discussionmentioning

confidence: 98%

Impact of declining intermediate-water oxygen on deepwater fishes in the California Current

Koslow¹,

Goericke²,

Lara‐Lopez³

et al. 2011

Mar. Ecol. Prog. Ser.

183

188

View full text Add to dashboard Cite

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“…(2) Its consumption determines high nitrogen loss and in consequence a low N : P ratio of upwelled waters, below the classical Redfield ratio of 16, with a strong impact on primary and secondary production (Franz et al, 2012), and (3) it is a control factor in the distribution of organisms (e.g., Bertrand et al, 2010;Criales-Hernández et al, 2006;Ekau et al, 2010;Gutiérrez et al, 2008;Levin et al, 2002). The position, strength and thickness of the eastern South Pacific OMZ can be greatly modified by local and/or remote forcing (e.g., interannual timescales, Morales et al, 1999;Gutiérrez et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

The OMZ and nutrient features as a signature of interannual and low-frequency variability in the Peruvian upwelling system

et al. 2017

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Abstract. Over the last decades, the Humboldt Current upwelling ecosystem, particularly the northern component off the coast of Peru, has drawn the interest of the scientific community because of its unique characteristics: it is the upwelling system with the biggest catch productivity despite the fact it is embedded in a shallow and intense oxygen minimum zone (OMZ). It is also an area of intense nitrogen loss and anammox activity and experiences large interannual variability associated with the equatorial remote forcing. In this context, we examined the oceanographic and biogeochemical variability associated with the OMZ off central Peru from a monthly time series (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011) recorded off the coast of Callao (12• 02 S, 77 • 29 W). The data reveal a rich spectrum of variability in the OMZ that includes frequencies ranging from seasonal to interannual scales. Due to the efficient oceanic teleconnection off Peru, the observed variability is interpreted in the light of an estimate of the equatorial Kelvin wave contribution to sea level anomalies considering the peculiarities of its vertical structure (i.e., the first two baroclinic modes). The span of the data set allows us to contrast two OMZ regimes. The "strong" regime is associated with the strong 1997-1998 equatorial Pacific El Niño, during which the OMZ adjusted to Kelvin-wave-induced downwelling conditions that switched off the upwelling and drastically reduced nutrient availability. The "weak" regime corresponds to the post-2000 period associated with the occurrence of moderate central Pacific El Niño events and enhanced equatorial Kelvin wave activity, in which mean upwelling conditions are maintained. It is shown that the characteristics of the coupling between physics and biogeochemistry is distinct between the two regimes with the weak regime being associated with a larger explained variance in biogeochemical properties not linearly related to the ENSO oceanic teleconnection. The data also reveal a long-term trend from 1999 corresponding to a deepening of the oxygendeficient waters and warming. The implications of our results for understanding the OMZ dynamics off Peru are discussed.

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“…Also, differences in their range of habitat (sardines are generally farther offshore; Bertrand et al 2004, 2008, Swartzman et al 2008) may reflect differences in their ability to successfully reproduce in strong upwelling environments. These habitats are usually anoxic below a shallow oxycline (10 to 30 m; Bertrand et al 2008Bertrand et al , 2010, have strong offshore surface transport of food resources, eggs and larvae, and tend to favour certain groups of phytoplankton (e.g. diatoms), which may influence both anchovy and sardine reproductive success (P. Espinoza pers.…”

Section: Introductionmentioning

confidence: 99%

Long-term changes in zooplankton size distribution in the Peruvian Humboldt Current System: conditions favouring sardine or anchovy

Ayón¹,

Swartzman²,

Espinoza³

et al. 2011

Mar. Ecol. Prog. Ser.

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Changes in the size distribution of zooplankton in the Humboldt Current System have been hypothesized to underlie observed changes in sardine and anchovy populations, the dominant pelagic fish species. To examine this hypothesis, the size distribution of over 15 000 zooplankton data samples collected since the 1960s was qualitatively determined. Dominance of each size group of zooplankton (small, medium and large) and of euphausiids was modelled using generalized additive models as a function of year, latitude, time of day, distance from the 200 m isobath (a surrogate for onshelf versus off-shelf), sea surface temperature and salinity. The temporal (yr) pattern for euphausiid dominance was highly cross-correlated (i.e. was in phase) with the time series for estimated biomass of anchovy, and small zooplankton dominance with that for estimated sardine biomass. This supports the focal hypothesis based on feeding-energetic experiments, which showed energetic advantages to sardine filter feeding on smaller zooplankton and to anchovy bite feeding on larger copepods and euphausiids. Although euphausiids predominate offshore from the shelf break, anchovy biomass is generally highest on the shelf, suggesting a possible mismatch between anchovy feeding and euphausiid dominance. However, evidence concerning the offshore expansion of the anchovy range in cooler conditions, where both anchovy and euphausiids predominate, somewhat alleviates this apparent contradiction. A strong diel component to euphausiids and large zooplankton indicated diel migration for these zooplankton groups. That anchovy will preferentially eat euphausiids when they are more available (i.e. during the night and offshore) is supported by anchovy diet data.

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Acoustic Observation of Living Organisms Reveals the Upper Limit of the Oxygen Minimum Zone

Cited by 131 publications

References 43 publications

Impact of declining intermediate-water oxygen on deepwater fishes in the California Current

Impact of declining intermediate-water oxygen on deepwater fishes in the California Current

The OMZ and nutrient features as a signature of interannual and low-frequency variability in the Peruvian upwelling system

Long-term changes in zooplankton size distribution in the Peruvian Humboldt Current System: conditions favouring sardine or anchovy

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