Broad-scale trophic shift in the pelagic North Pacific revealed by an oceanic seabird

Human-induced ecological change in the open oceans appears to be accelerating. Fisheries, climate change and elevated nutrient inputs are variously blamed, at least in part, for altering oceanic ecosystems. Yet it is challenging to assess the extent of anthropogenic change in the open oceans, where historical records of ecological conditions are sparse, and the geographical scale is immense. We developed millennial-scale amino acid nitrogen isotope records preserved in ancient animal remains to understand changes in food web structure and nutrient regimes in the oceanic realm of the North Pacific Ocean (NPO). Our millennial-scale isotope records of amino acids in bone collagen in a wide-ranging oceanic seabird, the Hawaiian petrel ( Pterodroma sandwichensis ), showed that trophic level declined over time. The amino acid records do not support a broad-scale increase in nitrogen fixation in the North Pacific subtropical gyre, rejecting an earlier interpretation based on bulk and amino acid specific δ 15 N chronologies for Hawaiian deep-sea corals and bulk δ 15 N chronologies for the Hawaiian petrel. Rather, our work suggests that the food web structure in the NPO has shifted at a broad geographical scale, a phenomenon potentially related to industrial fishing.

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Vertical and latitudinal variations in amino acid fluxes and compositions of settling particles along 175°E in the North Pacific Ocean

Tellus B ◽

10.3402/tellusb.v55i2.16758 ◽

2003 ◽

Vol 55 (2) ◽

pp. 445-455

Author(s):

Lallan P. Gupta ◽

Hodaka Kawahata

Keyword(s):

Amino Acid ◽

Pacific Ocean ◽

North Pacific ◽

North Pacific Ocean ◽

Settling Particles ◽

The North ◽

Latitudinal Variations ◽

The North Pacific

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Food web structure variability in the surface layer, at a fixed station influenced by the North Western Mediterranean Current

Hydrobiologia ◽

10.1007/bf00023170 ◽

1996 ◽

Vol 321 (2) ◽

pp. 145-153 ◽

Cited By ~ 20

Author(s):

Urania Christaki ◽

France Van Wambeke ◽

Epaminondas D. Christou ◽

Pascal Conan ◽

Raymond Gaudy

Keyword(s):

Surface Layer ◽

Food Web ◽

Western Mediterranean ◽

Food Web Structure ◽

The North ◽

Web Structure ◽

North Western ◽

Fixed Station

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Reconstructing variability in West Greenland ocean biogeochemistry and bowhead whale (Balaena mysticetus) food web structure using amino acid isotope ratios

Polar Biology ◽

10.1007/s00300-017-2136-x ◽

2017 ◽

Vol 40 (11) ◽

pp. 2225-2238 ◽

Cited By ~ 9

Author(s):

Corinne Pomerleau ◽

Mads Peter Heide-Jørgensen ◽

Steven H. Ferguson ◽

Harry L. Stern ◽

Jacob L. Høyer ◽

...

Keyword(s):

Amino Acid ◽

Food Web ◽

Isotope Ratios ◽

Bowhead Whale ◽

Balaena Mysticetus ◽

Food Web Structure ◽

West Greenland ◽

Web Structure ◽

Ocean Biogeochemistry

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Millennial-scale variations in sedimentary oxygenation in the western subtropical North Pacific and its links to North Atlantic climate

Climate of the Past ◽

10.5194/cp-16-387-2020 ◽

2020 ◽

Vol 16 (1) ◽

pp. 387-407 ◽

Cited By ~ 1

Author(s):

Jianjun Zou ◽

Xuefa Shi ◽

Aimei Zhu ◽

Selvaraj Kandasamy ◽

Xun Gong ◽

...

Keyword(s):

North Atlantic ◽

North Pacific ◽

Deep Ocean ◽

Co2 Concentration ◽

Atmospheric Co2 ◽

Intermediate Water ◽

The North ◽

Geochemical Parameters ◽

The North Pacific ◽

Millennial Scale

Abstract. The deep-ocean carbon cycle, especially carbon sequestration and outgassing, is one of the mechanisms to explain variations in atmospheric CO2 concentrations on millennial and orbital timescales. However, the potential role of subtropical North Pacific subsurface waters in modulating atmospheric CO2 levels on millennial timescales is poorly constrained. An increase in the respired CO2 concentration in the glacial deep-ocean due to biological pump generally corresponds to deoxygenation in the ocean interior. This link thus offers a chance to study oceanic ventilation and coeval export productivity based on redox-controlled sedimentary geochemical parameters. Here, we investigate a suite of geochemical proxies in a sediment core from the Okinawa Trough to understand sedimentary oxygenation variations in the subtropical North Pacific over the last 50 000 years (50 ka). Our results suggest that enhanced mid-depth western subtropical North Pacific (WSTNP) sedimentary oxygenation occurred during cold intervals and after 8.5 ka, while oxygenation decreased during the Bölling-Alleröd (B/A) and Preboreal. The enhanced oxygenation during cold spells is linked to the North Pacific Intermediate Water (NPIW), while interglacial increase after 8.5 ka is linked to an intensification of the Kuroshio Current due to strengthened northeast trade winds over the tropics. The enhanced formation of the NPIW during Heinrich Stadial 1 (HS1) was likely driven by the perturbation of sea ice formation and sea surface salinity oscillations in the high-latitude North Pacific. The diminished sedimentary oxygenation during the B/A due to a decreased NPIW formation and enhanced export production, indicates an expansion of the oxygen minimum zone in the North Pacific and enhanced CO2 sequestration at mid-depth waters, along with the termination of atmospheric CO2 concentration increase. We attribute the millennial-scale changes to an intensified NPIW and enhanced abyss flushing during deglacial cold and warm intervals, respectively, closely related to variations in North Atlantic Deep Water formation.

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Persistent millennial-scale links between North Pacific intermediate-water ventilation and North Atlantic Climate during the deglaciation and last glaciation

10.5194/egusphere-egu2020-7221 ◽

2020 ◽

Author(s):

Jianjun Zou ◽

Xuefa Shi ◽

Aimei Zhu ◽

Yuan-Pin Chang ◽

Min-Te Chen ◽

...

Keyword(s):

North Atlantic ◽

North Pacific ◽

North Pacific Ocean ◽

Meridional Overturning Circulation ◽

Intermediate Water ◽

North Pacific Intermediate Water ◽

The North ◽

Last Glaciation ◽

The North Pacific ◽

Millennial Scale

The deep ocean carbon cycle, especially carbon sequestration and outgassing, is one of the mechanisms to explain variations in atmospheric CO2 concentrations on millennial and orbital timescales. However, the potential role of subtropical North Pacific subsurface waters in modulating atmospheric CO2 levels on millennial timescales is poorly constrained. Here, we investigate a suite of geochemical proxies in a sediment core from the northern and middle Okinawa Trough to understand variations in intermediate-water ventilation of the subtropical North Pacific over the last 50,000 years (50 ka). Our results suggest that enhanced mid-depth western subtropical North Pacific (WSTNP) sedimentary oxygenation occurred during cold intervals during the last deglaciation and last glaciation, while oxygenation decreased during the B&#246;lling-Aller&#246;d (B/A) and warm interstadials. The enhanced oxygenation during cold spells is linked to the intensified North Pacific Intermediate Water (NPIW), while interglacial increase after 8.5 ka is linked to an intensification of the Kuroshio Current due to strengthened northeast trade winds over the tropics. The enhanced formation of NPIW during Heinrich Stadials was likely driven by the perturbation of sea ice formation and sea surface salinity oscillations in high-latitude North Pacific. The diminished sedimentary oxygenation during the B/A and interstadials due to decreased NPIW formation and enhanced export production, indicates an expansion of oxygen minimum zone in the North Pacific and enhanced CO2 sequestration at mid-depth waters. We attribute the millennial-scale changes to intensified NPIW and enhanced abyss flushing during deglacial cold and warm intervals, respectively, closely related to variations in North Atlantic Deep Water formation. Out study extends the millennial-scale links between ventilation in the subtropical North Pacific Ocean and the Atlantic Climate into the last glaciations, highlighting the key roles of Atlantic Meridional Overturning Circulation in regulating the North Pacific environment at millennial timescales. Note: Financial support was provided by the National Program on Global Change and Air-Sea Interaction (GASI-GEOGE-04) and by the National Natural Science Foundation of China (Grant Nos.: 41876065, 41476056, and U1606401).

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