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Organic carbon and apparent oxygen utilization in the western South Pacific and the central Indian Oceans

MARINE CHEMISTRY 2000年第3期68卷 249-264页

作者： Doval, MD Hansell, DA Bermuda Biol Stn Res GE-01 St Georges Bermuda

Samples for total organic carbon (TOC) analysis were collected on WOCE Line P15S (0 degrees to 67 degrees S along 170 degrees W) and from 53 degrees to 67 degrees S along 170 degrees E in the western South Pacific, and on Line 18 (5 degrees N to 43 degrees S along 80 degrees/90 degrees E) in the central Indian Ocean. TOC concentrations in the upper ocean varied greatly between the regions studied. Highest surface TOC concentrations (81-85 mu M C and 68-73 mu M C) were observed in the warmest waters (> 27 degrees C) of the western South Pacific and central Indian Oceans, respectively. Lowest surface TOC concentrations (45-65 mu M C) were recorded in the southernmost waters occupied (> 50 degrees S along 170 degrees W and 170 degrees E). Deep water (> 1000 m) TOC concentrations were uniform across all regions analyzed, averaging between 42.3 and 43 mu M C (SD: +/- 0.9 mu M C). Mixing between TOC-rich surface waters and TOC-poor deep waters was indicated by the strong correlations between TOC and temperature (r(2) > 0.80, north of 45 degrees S) and TOC and density (r(2) > 0.50, southernmost regions). TOC was inversely correlated with apparent oxygen utilization (AOU) along isopycnal surfaces north of the Polar Frontal Zone (PFZ) and at depths < 500 m. The TOC:AOU molar ratios at densities of sigma(T) 23-27 ranged from -0.15 to -0.34 in the South Pacific and from -0.13 to -0.31 in the Indian Ocean. These ratios indicate that TOC oxidation was responsible for 21%-47% and 18%-43% of oxygen consumption in the upper South Pacific and Indian Oceans, respectively. At greater depths, TOC did not contribute to the development of AOU. There was no evidence for significant export of dissolved and suspended organic carbon along isopycnal surfaces that ventilate near the PFZ. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词： total organic carbon dissolved organic carbon apparent oxygen utilization Western South Pacific Ocean Central Indian Ocean

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Dissolved organic carbon and apparent oxygen utilization in the Atlantic Ocean

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DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS 2014年 85卷 80-87页

作者： Pan, Xi Achterberg, Eric P. Sanders, Richard Poulton, Alex J. Oliver, Kevin I. C. Robinson, Carol Univ Southampton Natl Oceanog Ctr Southampton Ocean & Earth Sci Southampton SO14 3ZH Hants England Natl Oceanog Ctr Southampton Southampton SO14 3ZH Hants England Univ E Anglia Sch Environm Sci Norwich NR4 7TJ Norfolk England Helmholtz Ctr Ocean Res GEOMAR D-24148 Kiel Germany

Dissolved organic carbon (DOC) distributions along two Atlantic Meridional Transects conducted in 2005 in the region between 47 degrees N and 34 S showed clear latitudinal patterns. The DOC concentrations in the epipelagic zone (0-100 m) were the highest (70-90 p,M) in tropical and subtropical waters with stable mixed layers, and lowest (50-55 mu M) at the poleward extremities of the transects due to deep convective mixing supplying low DOC waters to the surface. A decrease in DOC occurred with depth, and lowest DOC concentrations (41-45 mu M) in the 100-300 m depth range were observed in the equatorial region due to upwelling of low DOC waters. A strong relationship between DOC and AOU was observed in the sigma-t 26-26.5 isopycnal layer which underlies the euphotic zone and outcrops at the poleward extremities of the North and South Atlantic Subtropical Gyres (NASG and SASG) in the region ventilating the thermocline waters. Our observations reveal significant north-south variability in the DOC-AOU relationship. The gradient of the relationship suggests that 52% of the AOU in the sigma-t 26-26.5 density range was driven by DOC degradation in the NASG and 36% in the SASG, with the remainder due to the remineralisation of sinking particulate material. We assess possible causes for the greater contribution of DOC remineralisation in the NASG compared to the SASG. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Dissolved organic carbon apparent oxygen utilization Particulate organic carbon Carbon export Atlantic Meridional Transect

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Variability of dissolved reactive phosphate and apparent oxygen utilization along the west coast of India

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CHEMISTRY AND ECOLOGY 2006年第2期22卷 113-123页

作者： Gopinath, A Sindhu, R Nair, SM Cochin Univ Sci & Technol Sch Marine Sci Dept Chem Oceanog Cochin 682016 Kerala India

This work focuses on the spatial variability of dissolved reactive phosphate along the west coast of India. In this study. samples of surface and bottom water was collected from each of the 27 sites during a single pre-monsoon transect along the west coast of India to study the variation of dissolved reactive phosphate. Phosphate showed an enrichment pattern with increase in depth of the water column. In addition to this, an offshore increase in phosphate concentrations was noticed for both surface and bottom stations. Almost all the surface stations of this study area were found to be characterized by negative apparent oxygen utilization (AOU) values. and bottom stations of the deeper offshore zone (200 m depth) displayed large positive AOU values. The bottom stations of shallow near coastal waters and the deeper offshore zone are characterized by an inverse relationship between phosphate and dissolved oxygen. whereas at these depths, a direct relation was observed between phosphate and AOU. AOU is calculated as the difference between oxygen saturation value at the in situ temperature and salinity and the actual measured concentration. This oxidative re-mineralization mechanism decreases the observed dissolved oxygen well below the expected theoretical values, which is concordant with the higher concentration of phosphate and high positive AOU values.

关键词： reactive phosphate apparent oxygen utilization dissolved oxygen re-minerilization shallow near coastal waters

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Distributions of dissolved oxygen and apparent oxygen utilization in the Cosmonaut Sea and Amundsen Sea in austral summer 2021

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Advances in Polar Science 2023年第4期34卷 272-303页

作者： GUO Jiaying YANG Xufeng ZHAO Jun ZHU Yuanli LI Dong PAN Jianming Key Laboratory of Marine Ecosystem Dynamics Ministry of Natural ResourcesHangzhou 310012China Second Institute of Oceanography Ministry of Natural ResourcesHangzhou 310012China

Dissolved oxygen(DO)and apparent oxygen utilization(AOU)are crucial parameters for investigating marine ecosystem evolution and the marine *** this study,DO and AOU data were obtained and their spatial distribution characteristics were explored in the Cosmonaut Sea and Amundsen Sea in austral summer *** standard deviation range of DO parallel samples was<0.1–3.7μmol·L–1,which met the accuracy requirements of the survey *** DO concentration decreased sharply with water depth in the photic zone and increased slowly to the *** in the surface layer of the two seas was significantly negatively correlated with chlorophyll a(p<0.01),and AOU was significantly lower in the south Cosmonaut Sea than in the north Cosmonaut Sea and Amundsen Sea(p<0.01).In austral summer,AOU was as low as<130μmol·L–1 in the nearshore Cosmonaut Sea with thicker Antarctic Surface Water down to ca.500 *** early winter,AOU was lower than 50μmol·L–1 in the north Amundsen Sea in subsurface water(75–150 m).The unmodified Circumpolar Deep Water with high AOU(>160μmol·L–1)could surge up to ca.150–200 m in both seas,with stronger intrusion in the Amundsen *** AOU in bottom water was significantly lower(p<0.01)in the Cosmonaut Sea(118.9±11.8μmol·L–1)than the Amundsen Sea(141.7±7.4μmol·L–1),indicating the stable existence of fresh oxygen-rich Antarctic Bottom Water in the Cosmonaut Sea.

关键词： dissolved oxygen apparent oxygen utilization Antarctic Cosmonaut Sea Amundsen Sea

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Distributions of dissolved oxygen and apparent oxygen utilization in the Cosmonaut Sea and Amundsen Sea in austral summer 2022

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Advances in Polar Science 2024年第3期35卷 327-369页

作者： DING Yufei ZHU Changfeng ZHANG Cai ZHANG Haifeng ZHAO Jun GUO Xiaoze ZHANG Wei PAN Jianming Key Laboratory of Marine Ecosystem Dynamics Ministry of Natural ResourcesHangzhou 310012China Second Institute of Oceanography Ministry of Natural ResourcesHangzhou 310012China Organic Geochemistry Unit Key Laboratory of Geoscience Big Data and Deep Resource of Zhejiang ProvinceSchool of Earth SciencesZhejiang UniversityHangzhou 310027China

Dissolved oxygen(DO)and apparent oxygen utilization(AOU)are essential parameters for evaluating the impact of climate change on marine *** this study,we utilized data on DO and AOU collected from the Amundsen Sea(western Antarctic)and the Cosmonaut Sea(eastern Antarctic)during the 38th Chinese National Antarctic Research Expedition,along with chlorophyll a(Chl a)data,to analyze the impact of primary production and the spatial distribution and structural features of water masses in these *** findings show that the standard deviation range of parallel DO samples is between 0.1 and 3.9μmol·L^(-1),meeting the precision criteria of the survey *** values lower than 0.0μmol·L^(-1) were commonly observed in the surface waters of both regions,with the highest incidence in the polynya of Amundsen Sea,indicating a strong influence of high primary *** Cosmonaut Sea exhibited the highest AOU values(higher than 160.0μmol·L^(-1))in the 75-500 m layer,while AOU value in the Amundsen Sea did not exceed 160.0μmol·L^(-1),suggesting potential upwelling of Circumpolar Deep Water to 100 m in the Cosmonaut Sea with minimal changes in its properties,whereas significant changes were noted in the properties of upwelling modified Circumpolar Deep Water in the Amundsen *** values lower than 125.0μmol·L^(-1)were detected in the near-bottom waters of the Cosmonaut Sea,indicating the presence of Antarctic Bottom Water.

关键词： dissolved oxygen apparent oxygen utilization Southern Ocean water mass chlorophyll a

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The efficiency of the microbial carbon pump as seen from the relationship between apparent oxygen utilization and fluorescent dissolved organic matter

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PROGRESS IN OCEANOGRAPHY 2023年 210卷

作者： Xiao, Xilin Yamashita, Youhei Gonsior, Michael Jiao, Nianzhi Xiamen Univ Coll Environm & Ecol Xiamen 361102 Peoples R China Xiamen Univ Innovat Res Ctr Carbon Neutralizat State Key Lab Marine Environm Sci Coll Ocean & Earth SciFujian Key Lab Marine Carbo Xiamen 361102 Peoples R China Hokkaido Univ Fac Environm Earth Sci Grad Sch Environm Sci Sapporo Japan Univ Maryland Chesapeake Biol Lab Ctr Environm Sci Solomons MD 20688 USA Xiamen Univ Innovat Res Ctr Carbon Neutralizat Xiamen 361102 Peoples R China

The mechanism behind the source/production of refractory dissolved organic matter (RDOM) in the ocean re-mains an enigma, but the biological origin of RDOM has now been recognized and conceptualized as the mi-crobial carbon pump (MCP). Consequently, the development of a proxy for the efficiency of the MCP production of RDOM is desirable. It has widely been observed that marine humic-like fluorescent dissolved organic matter (FDOMH) is linearly correlated with apparent oxygen utilization (AOU), and hence it is promising for exploring this relationship. Here, we discuss whether the slope of the AOU-FDOMH correlation can be an indicator for evaluating the MCP efficiency in the dark ocean. We gathered all the peer-reviewed literature on AOU-FDOMH relationships and summarized the general results and factors that may affect this relationship. Finally, we pro-pose to make the AOU-FDOMH relationship comparable and applicable at a global scale in future studies to better constrain sources and sinks of FDOMH and its link to heterotrophic microbial respiration, namely, the FDOM-based MCP efficiency.

关键词： Refractory dissolved organic matter Microbial carbon pump Fluorescent dissolved organic matter apparent oxygen utilization

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Mixing Accounts for More Than Half of Biogeochemical Changes Along Mode Water Ventilation Pathways

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GEOPHYSICAL RESEARCH LETTERS 2025年第7期52卷

作者： Jutras, M. Bushinsky, S. M. Cerovecki, I. Briggs, N. Univ Hawaii Mnoa Dept Oceanog SOEST Honolulu HI 96822 USA Univ Calif San Diego Scripps Inst Oceanog San Diego CA USA Natl Oceanog Ctr Southampton England

Mode waters are critical for ocean ventilation and carbon sequestration. Using observations, we trace their subduction pathways and biogeochemical evolution. Solving modified mixing equations that account for respiration reveals that less than 50% of the oxygen changes along mode water ventilation pathways are due to respiration within the water mass, the rest being due to mixing with oxygen-poorer surrounding waters. Consequently, measured changes in oxygen or apparent oxygen utilization overestimate respiration by a factor of up to two, as do derived biogeochemical quantities such as remineralized carbon. Measured nitrate changes either overestimate or underestimate remineralization depending on surrounding concentrations. Mean true respiration rates in mode waters range from -0.1 to -0.4 mu ${\upmu }$mol kg-1yr-1 ${\text{kg}}<^>{-1}{\text{yr}}<^>{-1}$. Applying a fixed stoichiometric ratio to this respiration, we find that the total carbon export is highest in Southern Ocean mode waters, while carbon remineralization rates are highest in subtropical mode waters.

关键词： marine biogeochemistry apparent oxygen utilization mixing respiration argo

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Nutrient dynamics and biogeochemical processes at the Polar front of Indian sector of the Southern Ocean: Influence of Circumpolar deep water intrusion

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POLAR SCIENCE 2025年 43卷

作者： Soares, Melena A. Mishra, R. K. Sabu, P. Venkataramana, V. Naik, R. K. Sarkar, A. Chacko, R. Anilkumar, N. Minist Earth Sci Natl Ctr Polar & Ocean Res Vasco Da Gama 403804 Goa India Kuwait Inst Sci Res Safat 13109 Kuwait MESs Vasant Joshi Coll Arts & Commerce Vasco Da Gama 403726 Goa India

The Circumpolar Deep water (CDW) is one of the largest water masses in the Southern Ocean. The cross-frontal flow of the CDW is a vital mode of redistribution and transport of heat, salts, nutrients, etc. in the ocean. The present study aims to understand the role of the CDW intrusion on nutrient dynamics and biogeochemical processes at the Polar frontal region. The study noted a patch of high nutrients layer at similar to 300-400 m in the Polar Front-II, underlying the dicothermal layer or the temperature minimum layer. This high nutrient patch was attributed to the intrusion of the CDW at the Polar front, influencing the physico-chemical processes in the water column. It was evident that, the density gradient, stratification and overall, the combined effect of physicochemical and biological factors as a consequence of intrusion of the CDW contributed to the formation of the high nitrate patch at the Polar Front-II. Even though, the CDW intrusion did not significantly impact the photic layer dynamics during this study, the possible barrier effect during austral summer contribute to the formation of the high nitrate layer. This feature may be responsible for trapping nutrients in the subsurface due to stratification, and made available to the photic region via upwelling processes, consequently triggering changes in the biological community structure and biogeochemical processes.

关键词： Circumpolar deep water Polar front Nitrates apparent oxygen utilization

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Global trends in the fluorescence characteristics and distribution of marine dissolved organic matter

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MARINE CHEMISTRY 2011年第1-4期126卷 139-148页

作者： Jorgensen, Linda Stedmon, Colin A. Kragh, Theis Markager, Stiig Middelboe, Mathias Sondergaard, Morten Univ Aarhus Dept Marine Ecol Natl Environm Res Inst DK-4000 Roskilde Denmark Univ Copenhagen Marine Biol Sect DK-3000 Helsingor Denmark Univ Copenhagen Freshwater Biol Lab DK-3400 Hillerod Denmark

A fraction of dissolved organic matter (DOM) is able to fluoresce. This ability has been used in the present study to investigate the characteristics and distribution of different DOM fractions. A unique global dataset revealed seven different fluorescent fractions of DOM: two humic-like, four amino acid-like and one chemically uncharacterized. The spectral characteristics of the amino acid-like fractions resemble those of pure tryptophan, tyrosine and phenylalanine. The fluorescence intensities of these amino acid-like fractions are highest in the surface waters, rapidly decreasing with depth and at a constant low level in the bathypelagic layer. Such profiles indicate that amino acid-like DOM is linked to surface water production. From calibration curves we estimated the mean surface water concentrations of tryptophan and tyrosine to be 12.5 and similar to 15.9 nmol L-1, respectively, while mean deep water concentrations are 5.1 and similar to 6.5 nmol L-1. The fluorescence intensities of the humic-like DOM fractions were low in the surface layer, rapidly increasing in the mesopelagic layer and at constant high level in the bathypelagic layer. The low fluorescence intensities observed in the surface layer indicate the quantitative importance of photochemical degradation as a sink of the humic-like compounds. In the dark ocean (below 200 m), significant linear relationships between humic-like DOM fluorescence and microbial activity (apparent oxygen utilization. NO3- and PO43-) were found. These observations imply a link to dark ocean microbial remineralization and indicate that the major source of humic-like compounds is microbial turnover of organic matter. The results of the present study show that the distribution of the humic-like DOM fractions is a balance between supply from continental run off, net microbial production and photochemical removal in surface waters. (C) 2011 Elsevier B.V. All rights reserved.

关键词： Dissolved organic matter Fluorescence Humic Amino acids PARAFAC EEM Nutrients apparent oxygen utilization

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Vertical and horizontal distribution of fluorescent dissolved organic matter in the Southern Ocean

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MARINE CHEMISTRY 2007年第3-4期106卷 498-509页

作者： Yamashita, Youhei Tsukasaki, Ayumi Nishida, Tamihito Tanoue, Eiichiro Nagoya Univ Grad Sch Environm Studies Dept Earth & Environm Sci Nagoya Aichi 4648601 Japan

The vertical and horizontal distribution of fluorescent dissolved organic matter (FDOM), determined by fluorescence intensity at 320 nm excitation and 420 nm emission, were clarified in nine stations on two transects at the Southern Ocean, including a subtropical, subantarctic, polar frontal and Antarctic zone. All vertical profiles of fluorescence intensity showed that levels were lowest in the surface waters, increased with increasing the depth in mid-depth waters (similar to 2000 m), and then stayed within a relatively narrow range from there to the bottom. Such vertical profiles of FDOM were similar to those of nutrients, but were adverse to dissolved oxygen. In water columns below the temperature-minimum subsurface water (dichothermal waters) in the Antarctic zone and below the winter mixed layer in the other zones, we determined the relationships of fluorescence intensity to concentrations of nutrients and apparent oxygen utilization (AOU) over the entire area of the present study, and found significant linear correlations between the levels of fluorescence intensity and nutrient concentrations (r= 0.70 and 0.71 for phosphate and nitrate + nitrite, respectively) and AOU (r= 0.91). From the strong correlation coefficient between fluorescence intensity and AOU, we concluded that FDOM in the Southern Ocean is formed in situ via the biological oxidation of organic matter. The regeneration of the nutrients/consumption of the oxygen/formation of FDOM was active in mid-depth waters. However, the correlations between fluorescence intensities and nutrients and AOU were different in the mid-depth water masses, Subantarctic Mode Water (SAMW), and Antarctic Intermediate Water (AAIW), indicating that the sources of organic matter responsible for FDOM formation were different. A considerable amount of FDOM in the SAMW is thought to be produced by the remineralization of DOM in addition to sinking particulate organic matter, while DOM is less responsible for FDOM formation i

关键词： dissolved organic matter biogeochemical cycle fluorescence nutrients apparent oxygen utilization Southern Ocean

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