A 36 kyr geochemical record from the Sea of Japan of organic matter flux variations and changes in intermediate water oxygen concentrations

Abstract. Instrumental records from the Norwegian Sea and the Trondheimsfjord show evidence that changes of bottom water temperature and salinity in the fjord are linked to the salinity and temperature variability of the North Atlantic Current (NAC). Changes in primary productivity and salinity in the surface and intermediate water masses in the Trondheimsfjord as well as the fjord sedimentary budget are mainly driven by changes in riverine input. In this study we use 59 surface sediment samples that are evenly distributed in the fjord to examine whether dinocyst assemblages and stable isotope ratios of benthic foraminifera reflect the present-day hydrology and can be used as palaeoceanographic proxies. In general, modern benthic δ18O and δ13C values decrease from the fjord entrance towards the fjord head with lowest values close to river inlets. This is essentially explained by gradients in the amounts of fresh water and terrigenous organic matter delivered from the hinterland. The distribution of benthic δ13C ratios across the fjord is controlled by the origin (terrigenous vs. marine) of organic matter, local topography-induced variability in organic matter flux at the water–sediment interface, and organic matter degradation. The dinocyst assemblages display the variations in hydrography with respect to the prevailing currents, the topography, and the freshwater and nutrient supply from rivers. The strength and depth of the pycnocline in the fjord strongly vary seasonally and thereby affect water mass characteristics as well as nutrient availability, temporally creating local conditions that explain the observed species distribution. Our results prove that dinocyst assemblages and benthic foraminiferal isotopes reliably mirror the complex fjord hydrology and can be used as proxies of Holocene climatic variability.

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Transportation of organic matter to the sea floor by carrion falls of the giant jellyfish Nemopilema nomurai in the Sea of Japan

Marine Biology ◽

10.1007/s00227-007-0807-9 ◽

2007 ◽

Vol 153 (3) ◽

pp. 311-317 ◽

Cited By ~ 39

Author(s):

Jun Yamamoto ◽

Miyuki Hirose ◽

Tetsuya Ohtani ◽

Katashi Sugimoto ◽

Kazue Hirase ◽

...

Keyword(s):

Organic Matter ◽

Sea Of Japan ◽

The Sea Of Japan ◽

Nemopilema Nomurai ◽

Sea Floor ◽

Giant Jellyfish

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Bacterial productivity and organic matter flux in the Southern Ocean and in the Antarctic Intermediate Water and Mode Water of the Indian Ocean

Deep Sea Research Part II Topical Studies in Oceanography ◽

10.1016/s0967-0645(96)00110-5 ◽

1997 ◽

Vol 44 (5) ◽

pp. 1005-1015 ◽

Cited By ~ 11

Author(s):

D.J.W. Moriarty ◽

M. Bianchi ◽

V. Talbot

Keyword(s):

Organic Matter ◽

Indian Ocean ◽

Southern Ocean ◽

Intermediate Water ◽

Bacterial Productivity ◽

Mode Water ◽

Antarctic Intermediate Water ◽

The Indian Ocean ◽

Matter Flux ◽

The Antarctic

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The nitrogen isotope effect of benthic remineralization-nitrification-denitrification coupling in an estuarine environment

Biogeosciences ◽

10.5194/bg-9-1633-2012 ◽

2012 ◽

Vol 9 (5) ◽

pp. 1633-1646 ◽

Cited By ~ 40

Author(s):

M. Alkhatib ◽

M. F. Lehmann ◽

P. A. del Giorgio

Keyword(s):

Organic Matter ◽

Water Column ◽

Pore Water ◽

Bottom Water ◽

Isotope Fractionation ◽

N Loss ◽

N Transformations ◽

Lawrence Estuary ◽

Water Oxygen ◽

Oxygen Concentrations

Abstract. The nitrogen (N) stable isotopic composition of pore water nitrate and total dissolved N (TDN) was measured in sediments of the St. Lawrence Estuary and the Gulf of St. Lawrence. The study area is characterized by gradients in organic matter reactivity, bottom water oxygen concentrations, as well as benthic respiration rates. N isotope effects on the water column associated with the benthic exchange of nitrate (εapp) and TDN (εsed) during benthic nitrification-denitrification coupling were investigated. The sediments were a major sink for nitrate and a source of reduced dissolved N (RDN = DON + NH4+). We observed that both the pore water nitrate and RDN pools were enriched in 15N relative to the water column, with increasing δ15N downcore in the sediments. As in other marine environments, the biological nitrate isotope fractionation of net fixed N loss was barely expressed at the scale of sediment-water exchange, with &varepsilon;app values <3‰. The strongest under-expression (i.e. lowest εapp) of the biological N isotope fractionation was observed at the most oxygenated sites with the least reactive organic matter, indicating that, through their control on the depth of the denitrification zone, bottom water oxygen concentrations and the organic matter reactivity can modulate εapp. For the first time, actual measurements of δ15N of pore water RDN were included in the calculations of εsed. We argue that large fractions of the sea-floor-derived DON are reactive and, hence, involved in the development of the δ15N of dissolved inorganic N (DIN) in the water column. In the St. Lawrence sediments, the combined benthic N transformations yield a flux of 15N-enriched RDN that can significantly elevate εsed above εapp. Calculated εsed values were within the range of 4.6 ± 2‰ and were related to organic matter reactivity and oxygen penetration depth in the sediments. &varepsilon;sed reflects the δ15N of the N2 lost from marine sediments and thus best describes the isotopic impact of fixed N loss from sediments on the oceanic fixed N pool. Our mean value for εsed is larger than assumed by earlier work, questioning current ideas with regards to the state of balance of the modern N budget.

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Influence of northwest Pacific productivity on North Pacific Intermediate Water oxygen concentrations during the Bølling-Ållerød interval (14.7–12.9 ka)

Geology ◽

10.1130/g20508.1 ◽

2004 ◽

Vol 32 (7) ◽

pp. 633 ◽

Cited By ~ 86

Author(s):

John Crusius ◽

Thomas F. Pedersen ◽

Stephanie Kienast ◽

Lloyd Keigwin ◽

Laurent Labeyrie

Keyword(s):

North Pacific ◽

Northwest Pacific ◽

Intermediate Water ◽

North Pacific Intermediate Water ◽

Water Oxygen ◽

Oxygen Concentrations

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Intermediate- and Deep-Water Oxygenation History in the Subarctic North Pacific During the Last Deglacial Period

Frontiers in Earth Science ◽

10.3389/feart.2021.638069 ◽

2021 ◽

Vol 9 ◽

Author(s):

Ekaterina Ovsepyan ◽

Elena Ivanova ◽

Martin Tetard ◽

Lars Max ◽

Ralf Tiedemann

Keyword(s):

Sea Level ◽

Deep Water ◽

Bering Sea ◽

North Pacific ◽

Intermediate Water ◽

Western Bering Sea ◽

Water Oxygen ◽

Wide Range ◽

The Bering Sea ◽

Oxygen Concentrations

Deglacial dissolved oxygen concentrations were semiquantitatively estimated for intermediate and deep waters in the western Bering Sea using the benthic foraminiferal-based transfer function developed by Tetard et al. (2017), Tetard et al. (2021a). Benthic foraminiferal assemblages were analyzed from two sediment cores, SO201-2-85KL (963 m below sea level (mbsl), the intermediate-water core) and SO201-2-77KL (2,163 mbsl, the deep-water core), collected from the Shirshov Ridge in the western Bering Sea. Intermediate waters were characterized by an oxygen content of ∼2.0 ml L−1 or more during the Last Glacial Maximum (LGM)–Heinrich 1 (H1), around 0.15 ml L−1 during the middle Bølling/Allerød (B/A)–Early Holocene (EH), and a slight increase in [O2] (∼0.20 ml L−1) at the beginning of the Younger Dryas (YD) mbsl. Deep-water oxygen concentrations ranged from 0.9 to 2.5 ml L−1 during the LGM–H1, hovered around 0.08 ml L−1 at the onset of B/A, and were within the 0.30–0.85 ml L−1 range from the middle B/A to the first half of YD and the 1.0–1.7 ml L−1 range from the middle to late Holocene. The [O2] variations remind the δ18O NGRIP record thereby providing evidence for a link between the Bering Sea oxygenation at intermediate depths and the deglacial North Atlantic climate. Changes in the deep-water oxygen concentrations mostly resemble the deglacial dynamics of the Southern Ocean upwelling intensity which is supposed to be closely coupled with the Antarctic climate variability. This coherence suggests that deglacial deep-water [O2] variations were primarily controlled by changes in the circulation of southern-sourced waters. Nevertheless, the signal from the south at the deeper site might be amplified by the Northern Hemisphere climate warming via an increase in sea-surface bioproductivity during the B/A and EH. A semi-enclosed position of the Bering Sea and sea-level oscillations might significantly contribute to the magnitude of oxygenation changes in the study area during the last deglaciation. Interregional correlation of different proxy data from a wide range of water depths indicates that deglacial oxygenation changes were more pronounced in the Bering and Okhotsk marginal seas than along the open-ocean continental margin and abyssal settings of the North Pacific.

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Pleistocene deep-sea ostracods from the Oki Ridge, Sea of Japan (IODP Site U1426) and condition of the intermediate water

Quaternary Research ◽

10.1017/qua.2017.68 ◽

2017 ◽

Vol 88 (3) ◽

pp. 430-445 ◽

Cited By ~ 1

Author(s):

Tatsuhiko Yamaguchi ◽

Kentaro Kuroki ◽

Katsura Yamada ◽

Takuya Itaki ◽

Kaoru Niino ◽

...

Keyword(s):

Sea Of Japan ◽

Deep Sea ◽

Japan Sea ◽

Winter Monsoon ◽

Early Pleistocene ◽

Circulation System ◽

The Sea Of Japan ◽

Intermediate Water ◽

Oxygen Isotope Stage ◽

Integrated Ocean Drilling Program

AbstractThe Sea of Japan (also termed the East Sea) has a circulation system isolated from the Pacific Ocean and East China Sea. The East Asian winter monsoon drives the circulation system and cools the Tsushima Warm Current (TWC) to form the Japan Sea Intermediate–Proper Water (JSIPW). The intermediate water conveys oxygen to deep-sea floors, which is available for benthic animals. During the Pliocene (3.5–2.8 Ma), Temperate Intermediate Water (TIW) was formed under the weak winter monsoon, and extinct ostracod TIW taxa were found. Little is known about early Pleistocene intermediate water and the extinction mode of benthic ostracods. We studied radiolarians and ostracods from deep-sea sediments between 2.0 and 1.3 Ma (Marine Oxygen Isotope Stage [MIS] 77 to MIS 41) at Integrated Ocean Drilling Program Site U1426, Sea of Japan. The ostracod faunas contained TIW and JSIPW taxa. The radiolarian subtropical-water taxa and the JSIPW ostracods indicate a small influx of the TWC and the JSIPW. The TIW occasionally expanded to the middle bathyal zone. By analogy with the relationship between the modern JSIPW and winter monsoon, weak winter monsoon possibly caused gentle temperature gradients in the water column and the expansion of the TIW. The JSIPW taxa expanded their ranges into the deep sea during interglacial periods.

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The nitrogen isotope effect of benthic remineralization-nitrification-denitrification coupling in an estuarine environment

Biogeosciences Discussions ◽

10.5194/bgd-8-11689-2011 ◽

2011 ◽

Vol 8 (6) ◽

pp. 11689-11723

Author(s):

M. Alkhatib ◽

M. F. Lehmann ◽

P. A. del Giorgio

Keyword(s):

Organic Matter ◽

Water Column ◽

Pore Water ◽

Bottom Water ◽

Isotope Fractionation ◽

N Budget ◽

N Transformations ◽

Lawrence Estuary ◽

Water Oxygen ◽

Oxygen Concentrations

Abstract. The nitrogen (N) stable isotopic composition of pore water nitrate and total dissolved N (TDN) was measured in sediments of the St. Lawrence Estuary and the Gulf of St. Lawrence. The study area is characterized by gradients in organic matter reactivity, bottom water oxygen concentrations, as well as benthic respiration rates. Benthic N isotope exchange, as well as the nitrate and TDN isotope effects of benthic nitrification-denitrification coupling on the water column, &varepsilon;app and &varepsilon;sed, respectively, were investigated. The sediments were a major sink for nitrate and a source of reduced dissolved N (RDN = DON + NH4+). We observed that both the pore water nitrate and RDN pools were enriched in 15N relative to the water column, with increasing δ15N downcore in the sediments. As in other marine environments, the biological nitrate isotope fractionation of net nitrate elimination was barely expressed at the scale of sediment-water-exchange, with &varepsilon;app values <3‰. The strongest under-expression of the biological N isotope fractionation was observed at the most oxygenated sites with the least reactive organic matter, indicating that, through their control on the depth of the denitrification zone, bottom water oxygen concentrations and the organic matter reactivity can modulate &varepsilon;app. For the first time, actual measurements of δ15N of pore water RDN were included in the calculations of &varepsilon;sed. We argue that large fractions of the sea-floor-derived DON are reactive and, hence, involved in the development of the δ15N of dissolved inorganic N (DIN) in the water column. In the St. Lawrence sediments, the combined benthic N transformations yield a flux of 15N-enriched RDN that can significantly enhance &varepsilon;sed. Calculated &varepsilon;sed values were within the range of 4.6 ± 2‰, and were related to organic matter reactivity and oxygen penetration depth in the sediments. &varepsilon;sed reflects the δ15N of the N2 lost from marine sediments and thus best describes the isotopic impact of N elimination on the oceanic fixed N pool. Our mean value for &varepsilon;sed is larger than assumed by earlier work, questioning current ideas with regards to the state of balance of the modern N budget.

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Spatial distribution of benthic foraminiferal stable isotopes and dinocyst assemblages in surface sediments of the Trondheimsfjord, central Norway

Biogeosciences Discussions ◽

10.5194/bgd-10-5889-2013 ◽

2013 ◽

Vol 10 (3) ◽

pp. 5889-5921 ◽

Cited By ~ 1

Author(s):

G. Milzer ◽

J. Giraudeau ◽

J. Faust ◽

J. Knies ◽

F. Eynaud ◽

...

Keyword(s):

Organic Matter ◽

Climatic Variability ◽

Intermediate Water ◽

North Atlantic Current ◽

Local Conditions ◽

Bottom Water Temperature ◽

The North ◽

Show Evidence ◽

Matter Flux ◽

Instrumental Records

Abstract. Instrumental records from the Norwegian Sea and the Trondheimsfjord show evidence that changes of bottom water temperature and salinity in the fjord are linked to the salinity and temperature variability of the North Atlantic Current (NAC). Changes in primary productivity and salinity in the surface and intermediate water masses in the Trondheimsfjord as well as the fjord sedimentary budget are mainly driven by changes in riverine input. In this study we use 59 surface sediment samples that are evenly distributed in the fjord to examine whether dinocyst assemblages and stable isotope ratios of benthic foraminifera reflect the present-day hydrology and can be used as paleoceanographic proxies. In general, modern benthic δ18O and δ13C values decrease from the fjord entrance towards the fjord head with lowest values close to river inlets. This is essentially explained by gradients in the amounts of freshwater and terrigenous organic matter delivered from the hinterland. The distribution of benthic δ13C ratios across the fjord is controlled by both the origin (terrigenous vs. marine) of organic matter and local topography-induced variability in organic matter flux at the water-sediment interface. The dinocyst assemblages display the variations in hydrography with respect to the prevailing currents, the topography, and the freshwater and nutrient supply from rivers. The strength and depth of the pycnocline in the fjord strongly varies seasonally and thereby affects water mass characteristics as well as nutrient availability, temporally creating local conditions that explain the observed species distribution. Our results prove that dinocyst assemblages and benthic foraminiferal isotopes reliably mirror the complex fjord hydrology and can therefore be used as proxies of Holocene climatic variability.

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