Planktic foraminiferal I/Ca from Holocene sediments of the Pacific and Indian Ocean

2020 ◽  
Author(s):  
Helge Arne Winkelbauer ◽  
Simon Chenery ◽  
Elliott Montagu Hamilton ◽  
Melanie Leng ◽  
Babette Hoogakker
Keyword(s):  
Planktonic Foraminifera ◽  
Subsurface Water ◽  
Future Trends ◽  
Oxygen Minimum Zones ◽  
Climatic Trends ◽  
The Pacific ◽  
Oxygen Cycle ◽  
Holocene Sediments ◽  
Oceanographic Conditions ◽  
Oxygen Minimum

<p>Current climatic trends are expected to lead to expansion of oxygen minimum zones and an overall decrease in oxygen concentration [O<sub>2</sub>] in the oceans. In order to improve predictions of future trends we need to create a better understanding of the natural oxygen cycle. The iodine to calcium ratio (I/Ca) of planktonic foraminifera is an increasingly popular proxy to assess upper water column oxygenation. Recent studies suggest that this ratio is mainly controlled by subsurface water dissolved oxygen concentrations. A thorough assessment of the proxy has been carried out for the South Atlantic, but is currently lacking for the Indian and Pacific Oceans, which contain the worlds’ most intense and large oxygen minimum zones. Here we present results of recent (Holocene) planktonic foraminifera (mixed layer and deep dwelling species) I/Ca measurements across a range of oceanographic conditions ([O<sub>2</sub>] varies between < 10 µmol/kg to > 200 µmol/kg) from the Indian and Pacific Ocean to further refine the proxy, using sample material provided by Lamont-Doherty Core Repository.</p>

scholarly journals Nitrous oxide dynamics in low oxygen regions of the Pacific: insights from the MEMENTO database

2012 ◽  
Vol 9 (12) ◽  
pp. 5007-5022 ◽  
Author(s):  
L. M. Zamora ◽  
A. Oschlies ◽  
H. W. Bange ◽  
K. B. Huebert ◽  
J. D. Craig ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
N2o Emissions ◽  
Low Oxygen ◽  
N2o Production ◽  
Oxygen Minimum Zones ◽  
A Value ◽  
The Pacific ◽  
Production And Consumption ◽  
The Relationship ◽  
Oxygen Minimum

Abstract. The eastern tropical Pacific (ETP) is believed to be one of the largest marine sources of the greenhouse gas nitrous oxide (N2O). Future N2O emissions from the ETP are highly uncertain because oxygen minimum zones are expected to expand, affecting both regional production and consumption of N2O. Here we assess three primary uncertainties in how N2O may respond to changing O2 levels: (1) the relationship between N2O production and O2 (is it linear or exponential at low O2 concentrations?), (2) the cutoff point at which net N2O production switches to net N2O consumption (uncertainties in this parameterisation can lead to differences in model ETP N2O concentrations of more than 20%), and (3) the rate of net N2O consumption at low O2. Based on the MEMENTO database, which is the largest N2O dataset currently available, we find that N2O production in the ETP increases linearly rather than exponentially with decreasing O2. Additionally, net N2O consumption switches to net N2O production at ~ 10 μM O2, a value in line with recent studies that suggest consumption occurs on a larger scale than previously thought. N2O consumption is on the order of 0.01–1 mmol N2O m−3 yr−1 in the Peru-Chile Undercurrent. Based on these findings, it appears that recent studies substantially overestimated N2O production in the ETP. In light of expected deoxygenation and the higher than previously expected point at which net N2O production switches to consumption, there is enough uncertainty in future N2O production that even the sign of future changes is still unclear.

scholarly journals The metabolic response of pteropods to acidification reflects natural CO<sub>2</sub>-exposure in oxygen minimum zones

2012 ◽  
Vol 9 (2) ◽  
pp. 747-757 ◽  
Author(s):  
A. E. Maas ◽  
K. F. Wishner ◽  
B. A. Seibel
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Consumption ◽  
Ocean Acidification ◽  
Metabolic Response ◽  
Ammonia Excretion ◽  
Individual Species ◽  
Tropical Regions ◽  
Oxygen Minimum Zones ◽  
The Pacific ◽  
Oxygen Minimum

Abstract. Shelled pteropods (Thecosomata) are a group of holoplanktonic mollusks that are believed to be especially sensitive to ocean acidification because their aragonitic shells are highly soluble. Despite this concern, there is very little known about the physiological response of these animals to conditions of elevated carbon dioxide. This study examines the oxygen consumption and ammonia excretion of five pteropod species, collected from tropical regions of the Pacific Ocean, to elevated levels of carbon dioxide (0.10%, 1000 ppm). Our results show that pteropods that naturally migrate into oxygen minimum zones, such as Hyalocylis striata, Clio pyramidata, Cavolinia longirostris and Creseis virgula, were not affected by carbon dioxide at the levels and duration tested. Diacria quadridentata, which does not migrate, responds to high carbon dioxide conditions with reduced oxygen consumption and ammonia excretion. This indicates that the natural chemical environment of individual species may influence their resilience to ocean acidification.

scholarly journals Response of Export Production and Dissolved Oxygen Concentrations to pCO<sub>2</sub> and Temperature Stabilization Scenarios

2016 ◽  
Author(s):  
T. Beaty ◽  
A. M. E. Winguth ◽  
C. Heinze
Keyword(s):  
Pacific Ocean ◽  
Dissolved Oxygen ◽  
Radiative Forcing ◽  
Oxygen Solubility ◽  
Oxygen Minimum Zones ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Do Concentration ◽  
Oxygen Minimum ◽  
Oxygen Concentrations

Abstract. Dissolved oxygen (DO) concentration in the ocean is an important component of marine biogeochemical cycles and will be greatly altered as climate change persists. In this study a global oceanic carbon cycle model (HAMOCC 2.0) is used to address how mechanisms of oxygen minimum zones (OMZ) expansion respond to changes in CO2 radiative forcing. Atmospheric pCO2 is increased at a rate of 1% annually and the model is stabilized at 2 X, 4 X, 6 X, and 8 X preindustrial pCO2 levels. With an increase in CO2 radiative forcing, the OMZ in the Pacific Ocean is controlled largely by changes in particulate organic carbon (POC) export, resulting in increased remineralization and thus expanding the oxygen minimum zones within the tropical Pacific Ocean. A potential decline in primary producers in the future as a result of environmental stress due to ocean warming and acidification could lead to a substantial reduction of vertical carbon flux and thus increased DO concentration particularly in the Pacific Ocean at a depth of 600-800 m. In contrast, the vertical expansion of the OMZs within the Atlantic and Indian Oceans are linked to reduced oxygen solubility due to rise in potential temperature and to a lesser extent changes in remineralization rates. Changes in oxygen solubility also lead to the formation of a new OMZ in the western subtrobical Pacific Ocean. The development of the new OMZ results in dissolved oxygen concentration of ≤50 μmols throughout the equatorial Pacific Ocean at 4 times preindustrial pCO2. Total ocean area with dissolved oxygen concentrations of ≤50 μmols increases by 2.5%, 4.5%, and 7.6% for the 2 X, 4X, and 8 X CO2 simulations, respectively.

scholarly journals The metabolic response of pteropods to ocean acidification reflects natural CO<sub>2</sub>-exposure in oxygen minimum zones

2011 ◽  
Vol 8 (5) ◽  
pp. 10295-10316 ◽  
Author(s):  
A. E. Maas ◽  
K. F. Wishner ◽  
B. A. Seibel
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Consumption ◽  
Ocean Acidification ◽  
Metabolic Response ◽  
Ammonia Excretion ◽  
Individual Species ◽  
Tropical Regions ◽  
Oxygen Minimum Zones ◽  
The Pacific ◽  
Oxygen Minimum

Abstract. Shelled pteropods (Thecosomata) are a group of holoplanktonic mollusks that are believed to be especially sensitive to ocean acidification because their aragonitic shells are highly soluble. Despite this concern, there is very little known about the physiological response of these animals to conditions of elevated carbon dioxide. This study examines the oxygen consumption and ammonia excretion of five pteropod species, collected from tropical regions of the Pacific Ocean, to elevated levels of carbon dioxide (0.10%, 1000 ppm). Our results show that pteropods that naturally migrate into oxygen minimum zones, such as Hyalocylis striata, Clio pyramidata, Cavolinia longirostris and Creseis virgula, were not affected by carbon dioxide at the levels and duration tested. Diacria quadridentata, which does not migrate, responds to high carbon dioxide conditions with reduced oxygen consumption and ammonia excretion. This indicates that the natural chemical environment of individual species influences their resilience to ocean acidification.

scholarly journals Nitrous oxide dynamics in low oxygen regions of the Pacific: insights from the MEMENTO database

2012 ◽  
Vol 9 (8) ◽  
pp. 10019-10056 ◽  
Author(s):  
L. M. Zamora ◽  
A. Oschlies ◽  
H. W. Bange ◽  
J. D. Craig ◽  
K. B. Huebert ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Low Oxygen ◽  
N2o Production ◽  
Oxygen Minimum Zones ◽  
A Value ◽  
Regional Production ◽  
The Pacific ◽  
Production And Consumption ◽  
The Relationship ◽  
Oxygen Minimum

Abstract. The Eastern Tropical Pacific (ETP) is believed to be one of the largest marine sources of the greenhouse gas nitrous oxide N2O). Future N2Oemissions from the ETP are highly uncertain because oxygen minimum zones are expected to expand, affecting both regional production and consumption of N2O. Here we assess three primary uncertainties in how N2O may respond to changing O2 levels: (1) the relationship between N2O production and O2 (is it linear or exponential at low O2 concentrations?), (2) the cutoff point at which net N2O production switches to net N2O consumption (uncertainties in this parameterization can lead to differences in model ETP N2O concentrations of more than 20%), and (3) the rate of net N2O consumption at low O2. Based on the MEMENTO database, which is the largest N2O dataset currently available, we find that N2O production in the ETP increases linearly rather than exponentially with decreasing O2. Additionally, net N2O consumption switches to net N2O production at ~ 10 μM O2, a value in line with recent studies that suggest consumption occurs on a larger scale than previously thought. N2O consumption is on the order of 0.129 mmol N2O m−3 yr−1 in the Peru–Chile Undercurrent. Based on these findings, it appears that recent studies substantially overestimated N2O production in the ETP. In light of expected deoxygenation, future N2O production is still uncertain, but due to higher-than-expected consumption levels, it is possible that N2Oconcentrations may decrease rather than increase as oxygen minimum zones expand.

scholarly journals The evolving response of mesopelagic fishes to declining midwater oxygen concentrations in the southern and central California Current

2018 ◽  
Vol 76 (3) ◽  
pp. 626-638 ◽  
Author(s):  
J Anthony Koslow ◽  
Pete Davison ◽  
Erica Ferrer ◽  
S Patricia A Jiménez Rosenberg ◽  
Gerardo Aceves-Medina ◽  
...  
Keyword(s):  
Baja California ◽  
Southern Oscillation ◽  
Global Climate ◽  
California Current ◽  
Deep Ocean ◽  
Near Surface ◽  
Oxygen Minimum Zones ◽  
The North ◽  
The Pacific ◽  
Oxygen Concentrations

Abstract Declining oxygen concentrations in the deep ocean, particularly in areas with pronounced oxygen minimum zones (OMZs), are a growing global concern related to global climate change. Its potential impacts on marine life remain poorly understood. A previous study suggested that the abundance of a diverse suite of mesopelagic fishes off southern California was closely linked to trends in midwater oxygen concentration. This study expands the spatial and temporal scale of that analysis to examine how mesopelagic fishes are responding to declining oxygen levels in the California Current (CC) off central, southern, and Baja California. Several warm-water mesopelagic species, apparently adapted to the shallower, more intense OMZ off Baja California, are shown to be increasing despite declining midwater oxygen concentrations and becoming increasingly dominant, initially off Baja California and subsequently in the CC region to the north. Their increased abundance is associated with warming near-surface ocean temperature, the warm phase of the Pacific Decadal oscillation and Multivariate El Niño-Southern Oscillation Index, and the increased flux of Pacific Equatorial Water into the southern CC.

scholarly journals In situ quantification of ultra‐low O 2 concentrations in oxygen minimum zones: Application of novel optodes

2016 ◽  
Vol 14 (12) ◽  
pp. 784-800 ◽  
Author(s):  
Morten Larsen ◽  
Philipp Lehner ◽  
Sergey M. Borisov ◽  
Ingo Klimant ◽  
Jan P. Fischer ◽  
...  
Keyword(s):  
Oxygen Minimum Zones ◽  
Oxygen Minimum

scholarly journals Expanded oxygen minimum zones during the late Paleocene-early Eocene: Hints from multiproxy comparison and ocean modeling

2016 ◽  
Vol 31 (12) ◽  
pp. 1532-1546 ◽  
Author(s):  
X. Zhou ◽  
E. Thomas ◽  
A. M. E. Winguth ◽  
A. Ridgwell ◽  
H. Scher ◽  
...  
Keyword(s):  
Ocean Modeling ◽  
Early Eocene ◽  
Oxygen Minimum Zones ◽  
Late Paleocene ◽  
Oxygen Minimum

scholarly journals Toward a global calibration for quantifying past oxygenation in oxygen minimum zones using benthic Foraminifera

2021 ◽  
Author(s):  
Martin Tetard ◽  
Laetitia Licari ◽  
Kazuyo Tachikawa ◽  
Ekaterina Ovsepyan ◽  
Luc Beaufort
Keyword(s):  
North Pacific ◽  
Transfer Functions ◽  
Late Quaternary ◽  
Global Climate ◽  
Single Species ◽  
Pore Waters ◽  
Oxygen Minimum Zones ◽  
Global Calibration ◽  
Circularity Index ◽  
Oxygen Minimum

Abstract. Oxygen Minimum Zones (OMZs) are oceanic areas largely depleted in dissolved oxygen, nowadays considered in expansion in the face of global warming. Their ecological and economic consequences are being debated. The investigation of past OMZ conditions allows us to better understand biological and physical mechanisms responsible for their variability with regards to climate change, carbon pump and carbonate system. To investigate the relationship between OMZ expansion and global climate changes during the late Quaternary, quantitative oxygen reconstructions are needed, but are still in their early development. Here, past bottom water oxygenation (BWO) was quantitatively assessed through a new, fast, semi-automated, and taxonfree morphometric analysis of benthic foraminiferal tests, developed and calibrated using Eastern North Pacific (ENP) and the Eastern South Pacific (ESP) OMZs samples. This new approach is based on an average size and circularity index for each sample. This method, as well as two already published micropalaeontological approaches based on benthic foraminiferal assemblages variability and porosity investigation of a single species, were here calibrated based on availability of new data from 23 core tops recovered along an oxygen gradient (from 0.03 to 1.79 mL.L−1) from the ENP, ESP, AS (Arabian Sea) and WNP (Western North Pacific, including its marginal seas) OMZs. Global calibrated transfer functions are thus herein proposed for each of these methods. These micropalaeontological reconstruction approaches were then applied on a paleorecord from the ENP OMZ to examine the consistency and limits of these methods, as well as the relative influence of bottom and pore waters on these micropalaeontological tools. Both the assemblages and morphometric approaches (that is also ultimately based on the ecological response of the complete assemblage and faunal succession according to BWO) gave similar and consistent past BWO reconstructions, while the porosity approach (based on a single species and its unique response to a mixed signal of bottom and pore waters) shown ambiguous estimations.

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