Dissolved organic carbon export and subsequent remineralization in the mesopelagic and bathypelagic realms of the North Atlantic basin

Carlson, Craig A.; Hansell, Dennis A.; Nelson, Norman B.; Siegel, David A.; Smethie, William M.; Khatiwala, S.; Meyers, Meredith M.; Halewood, Elisa R.

doi:10.1016/j.dsr2.2010.02.013

Cited by 229 publications

(272 citation statements)

References 83 publications

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“…POP was analyzed using the ash-hydrolysis method with oxidation efficiency and standard recovery checks (Lomas et al, 2010). TOC and TON concentrations were determined using hightemperature combustion techniques (Carlson et al, 2010). Total P (TP) concentrations were quantified using a hightemperature persulfate oxidation technique and TOP calculated by subtraction of the MAGIC-SRP value (Lomas et al, 2010 (and PON) values were taken at slightly different depths but on the same sampling day.…”

Section: Methodsmentioning

confidence: 99%

C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean

et al. 2015

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Abstract. Nitrogen (N) and phosphorus (P) availability, in addition to other macro-and micronutrients, determine the strength of the ocean's carbon (C) uptake, and variation in the N : P ratio of inorganic nutrient pools is key to phytoplankton growth. A similarity between C : N : P ratios in the plankton biomass and deep-water nutrients was observed by Alfred C. Redfield around 80 years ago and suggested that biological processes in the surface ocean controlled deepocean chemistry. Recent studies have emphasized the role of inorganic N : P ratios in governing biogeochemical processes, particularly the C : N : P ratio in suspended particulate organic matter (POM), with somewhat less attention given to exported POM and dissolved organic matter (DOM). Herein, we extend the discussion on ecosystem C : N : P stoichiometry but also examine temporal variation in stoichiometric relationships. We have analyzed elemental stoichiometry in the suspended POM and total (POM + DOM) organic-matter (TOM) pools in the upper 100 m and in the exported POM and subeuphotic zone (100-500 m) inorganic nutrient pools from the monthly data collected at the Bermuda Atlantic Time-series Study (BATS) site located in the western part of the North Atlantic Ocean. C : N and N : P ratios in TOM were at least twice those in the POM, while C : P ratios were up to 5 times higher in TOM compared to those in the POM. Observed C : N ratios in suspended POM were approximately equal to the canonical Redfield ratio (C : N : P = 106 : 16 : 1), while N : P and C : P ratios in the same pool were more than twice the Redfield ratio. Average N : P ratios in the subsurface inorganic nutrient pool were ∼ 26 : 1, squarely between the suspended POM ratio and the Redfield ratio. We have further linked variation in elemental stoichiometry to that of phytoplankton cell abundance observed at the BATS site. Findings from this study suggest that elemental ratios vary with depth in the euphotic zone, mainly due to different growth rates of cyanobacterial cells. We have also examined the role of the Arctic Oscillation on temporal patterns in C : N : P stoichiometry. This study strengthens our understanding of the variability in elemental stoichiometry in different organic-matter pools and should improve biogeochemical models by constraining the range of non-Redfield stoichiometry and the net relative flow of elements between pools.

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Section: Methodsmentioning

confidence: 99%

C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean

et al. 2015

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“…This volume was then decanted into precombusted 24 mL borosilicate vials, transported on ice, and stored in the dark at 220uC until sample analysis. DOC and dissolved organic nitrogen (DON) samples were analyzed via high temperature combustion using a Shimadzu total organic carbon and nitrogen analyzer (model TOC-V/TNM-1) and corrected to consensus reference material values (Hansell 2005;Carlson et al 2010). Errors represent the standard deviation of n 5 3 sample replicates per sample date.…”

Section: Methodsmentioning

confidence: 99%

Elemental and isotopic characterization of dissolved and particulate organic matter in a unique California upwelling system: Importance of size and composition in the export of labile material

Walker

McCarthy

2012

Limnology & Oceanography

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We report the interseasonal variation in bulk elemental and stable isotopic (d 13 C, d 15 N) composition of dissolved and particulate organic matter (DOM, POM) during a high-resolution time series (2007)(2008)(2009)) on the Big Sur coast. In addition to interseasonal variations, we explore the relationships between physical size and reactivity (i.e., composition) of exportable organic matter (OM) pools, and characterize the elemental and isotopic composition of size-fractionated POM and DOM pools within this potentially high-nutrient, low-chlorophyll (HNLC) California upwelling region. Average POM concentrations were low (, 5.2 mmol C L 21 and , 0.7 mmol N L 21 ), and all OM pools had low C : N ratios (DOM average 5 15.0 and POM , 7.8)-indicating that this upwelling center may represent an important source of N-rich material to offshore environments. Seasonal ''excess'' dissolved organic carbon (DOC) production was significant (, 30-80 mmol L 21 DOC); however, dissolved organic nitrogen (DON) production and cycling was largely decoupled from both DOC and physical processes. Overall, our results are consistent with this region representing an ''HNLC upwelling system.'' The distinct bulk elemental and isotopic OM composition and seasonality vs. that of high-productivity upwelling regions highlights the need to better understand the biogeochemical diversity of upwelling systems. Finally, we observed a quantifiable size-composition relationship across both POM and DOM size classes, perhaps representing a powerful new tool for modeling N vs. C fluxes in ocean biogeochemical cycles.

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“…Here we use conventional radiocarbon ages of SPE-DOM samples to obtain a DOC degradation rate. Other previous approaches used mixing models of [DOC], inverse models or correlated observed net losses of total [DOC] with water mass tracers to derive exponential decay rates (e.g., Hansell et al, 2009Hansell et al, , 2012Carlson et al, 2010). Our model approach defines an upper limit for the degradation rate as it includes decay of 14 C and preferential loss of young compounds according to the degradation continuum.…”

Section: Degradation Rate Of Bulk Doc Modeled From Spe-dom D 14 Cmentioning

confidence: 99%

Molecular transformation and degradation of refractory dissolved organic matter in the Atlantic and Southern Ocean

Lechtenfeld

Kattner

Flerus

et al. 2014

Geochimica et Cosmochimica Acta

249

259

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More than 90% of the global ocean dissolved organic carbon (DOC) is refractory, has an average age of 4000-6000 years and a lifespan from months to millennia. The fraction of dissolved organic matter (DOM) that is resistant to degradation is a long-term buffer in the global carbon cycle but its chemical composition, structure, and biochemical formation and degradation mechanisms are still unresolved. We have compiled the most comprehensive molecular dataset of 197 Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses from solid-phase extracted marine DOM covering two major oceans, the Atlantic sector of the Southern Ocean and the East Atlantic Ocean (ranging from 50°N to 70°S). Molecular trends and radiocarbon dating of 34 DOM samples (comprising D 14 C values from À229& to À495&) were combined to model an integrated degradation rate for bulk DOC resulting in a predicted age of >24 ka for the most persistent DOM fraction. First order kinetic degradation rates for 1557 mass peaks indicate that numerous DOM molecules cycle on timescales much longer than the turnover of the bulk DOC pool (estimated residence times of up to~100 ka) and the range of validity of radiocarbon dating. Changes in elemental composition were determined by assigning molecular formulae to the detected mass peaks. The combination of residence times with molecular information enabled modelling of the average elemental composition of the slowest degrading fraction of the DOM pool. In our dataset, a group of 361 molecular formulae represented the most stable composition in the oceanic environment ("island of stability"). These most persistent compounds encompass only a narrow range of the molecular elemental ratios H/C (average of 1.17 ± 0.13), and O/C (average of 0.52 ± 0.10) and molecular masses (360 ± 28 and 497 ± 51 Da). In the Weddell Sea DOC concentrations in the surface waters were low (46.3 ± 3.3 lM) while the organic radiocarbon was significantly more depleted than that of the East Atlantic, representing average surface water DOM ages of 4920 ± 180 a. These results are in accordance with a highly degraded DOM in the Weddell Sea surface water as also shown by the molecular degradation index I DEG obtained from FT-ICR MS data. Further, we identified 339 molecular formulae which probably contribute to an increased DOC concentration in the Southern Ocean and potentially reflect an accumulation or enhanced sequestration of refractory DOC in the Weddell Sea. These results will contribute to a better understanding of the persistent nature of marine DOM and its role as an oceanic carbon buffer in a changing climate.

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Dissolved organic carbon export and subsequent remineralization in the mesopelagic and bathypelagic realms of the North Atlantic basin

Cited by 229 publications

References 83 publications

C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean

C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean

Elemental and isotopic characterization of dissolved and particulate organic matter in a unique California upwelling system: Importance of size and composition in the export of labile material

Molecular transformation and degradation of refractory dissolved organic matter in the Atlantic and Southern Ocean

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