C:N ratios in the mixed layer during the productive season in the northeast Atlantic Ocean

Körtzinger, Arne; Koeve, Wolfgang; Kähler, Paul; Mintrop, L.

doi:10.1016/s0967-0637(00)00051-0

Cited by 149 publications

(156 citation statements)

References 82 publications

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“…Hence the export and decomposition of TON and TOP does probably contribute to excess nitrate build-up in subsurface water of the study area, by 20% for σ 0 =26.2 and by 40% for σ 0 =26.2. This result is in agreement with analyses of Landolfi (2005) and Landolfi et al (2008), who emphasized the importance of dissolved organic nutrients for the build-up of DINxs in oligotrophic gyres.…”

Section: Subsurface Water: Oxygen Doc and Nutrients; Subduction Andsupporting

confidence: 92%

“…It affects regional budgets of carbon and nitrate in surface water only if the excess carbon fixed is stored or exported. The accumulation, and export of dissolved organic matter of a large C:N ratio can explain carbon overconsumption as shown by Kähler and Koeve (2001) and Körzinger et al (2001) for the temperate eastern North Atlantic, but to a considerably smaller extent than suggested for that area by Sambrotto et al (1993). In these studies, excess carbon showed to be fixed during summer, a season of nutrient depletion and high temperature in surface water, i.e.…”

Section: Possible Solutionsmentioning

confidence: 70%

“…Modifications to it suggested e.g. by Takahashi et al (1985), Minster and Boulahdid (1987), Andersen and Sarmiento (1994) and Körzinger et al (2001), account for differences observed in different ocean basins and the fact that the oxidation state of carbon in organic mater is not exactly that of carbohydrates and more oxygen is needed for its oxidation to CO 2 . Their ratios differ from the Redfield ratio, but not to an extent to substantially alter our conclusions.…”

Section: Nutrients In the Subtropical North Atlanticmentioning

confidence: 99%

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Oxygen, carbon, and nutrients in the oligotrophic eastern subtropical North Atlantic

et al. 2010

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Abstract. The Beta Triangle, a region of the oligotrophic subtropical eastern North Atlantic Ocean, is notorious for its enigmatic oxygen, carbon, and nitrogen balances, in which nutrient supply is said to explain only a fraction of production necessary for estimated carbon export. Rates of dissolved organic carbon accumulation and dissolved organic nitrogen utilization in surface water and an assessment of oxygen utilized, organic matter consumed, and nitrate and phosphate regenerated in subsurface water, show that conventional production estimates miss substantial shares of biotic production.The shallow export of total organic carbon, predominantly dissolved (DOC), by subduction is responsible for about 50-70% of apparent oxygen utilization in subsurface water between the base of the surface layer at ca. 140 m and ca. 195 m depth, but it is insignificant below. Additionally, there is an estimated accumulation of 1.0 to 1.75 mol DOC m −2 a −1 in surface water. Including DOC dynamics in its carbon balance reveals the surface of this ultra-oligotrophic part of the ocean to be net autotrophic.Increasing subsurface values of excess nitrogen (DINxs) imply the export of nitrogen from surface water stemming from production not exclusively fuelled by new nitrate supplied from below. Total organic nitrogen (almost exclusively dissolved, DON) is consumed in the surface layer at a rate estimated at 0.13 to 0.23 mol m −2 a −1 . There is no variation in dissolved organic phosphorus (DOP) in the same direction. DON utilization thus contributes to the pronounced subsurface DINxs signature.DOC export and accumulation are important in the carbon balance in surface and near-surface water. DON utilization and, probably, N 2 fixation contribute significant amounts to Correspondence to: P. Kähler (pkaehler@ifm-geomar.de) the nitrogen supply of surface water. These processes can close part of the enigmatic carbon and nitrogen balances in the Beta Triangle. There are, however, no comparable processes which can explain the equally enigmatic situation concerning phosphorus supply in this area.

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Section: Subsurface Water: Oxygen Doc and Nutrients; Subduction Andsupporting

confidence: 92%

Section: Possible Solutionsmentioning

confidence: 70%

Section: Nutrients In the Subtropical North Atlanticmentioning

confidence: 99%

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Oxygen, carbon, and nutrients in the oligotrophic eastern subtropical North Atlantic

et al. 2010

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“…MacCready and Quay, 2001) relying on the mean global validity of the Redfield stoichiometry of C:N uptake in organic matter. Although there is evidence that, at least seasonally, particle formation with a C:N ratio significantly higher than the Redfield Ratio takes place (Körtzinger et al, 2001a;Engel et al, 2002) the present analysis indicates that export at the base of the mixed layer does not reflect this in the annual mean, at least in the North Atlantic. More such investigations are required from other areas.…”

Section: Elemental Ratios In Total (Dissolved + Particulate) Fluxcontrasting

confidence: 78%

“…MacCready and Quay, 2001). Indeed, this ratio is so accepted as being the "norm" that deviations in the so-called "Redfield ratios" of particles in surface waters are interpreted as "overproduction" of carbon, or an elevated efficiency of the biological pump (Körtzinger et al, 2001a;Engel et al, 2002). In the mesopelagial, changes in these ratios in sinking particles with depth are taken to reflect the remineralisation time and length scales of different elements (Honjo et al, 1982;Honjo and Manganini, 1993).…”

Section: Introductionmentioning

confidence: 99%

Solubilization of particles in sediment traps: revising the stoichiometry of mixed layer export

Antia¹

2005

Biogeosciences

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Abstract. Sinking particles, once caught in sediment trap jars, release dissolved elements into the surrounding medium through leaching from their pore fluids, chemical dissolution and the activity of free exoenzymes. This results in an increase in dissolved elements in the trap jar supernatant. Elemental fluxes as traditionally measured by sediment traps underestimate total export when this particle-associated dissolved flux is not considered. The errors introduced are variable and alter both the absolute levels of flux as well as the stoichiometry of export. These errors have been quantified and corrections applied for samples from sediment traps in the North Atlantic based on measurements of excess dissolved carbon, nitrogen, phosphorus, silica and calcium in the supernatant of the collection cups. At the base of the winter mixed layer, on average 90±6% of phosphorus fluxes are found as excess phosphate whereas for carbon and nitrogen dissolved concentrations account for 30 (±8)% and 47(±11)% of total fluxes respectively. Excess dissolved silica is on average 61 (±17)% of total biogenic silica flux. Little (<10%) of calcium is solubilized. The proportion of dissolved to total flux decreases with trap deployment depth. Calculations of the C:N:P ratios for particles only are well above the Redfield ratios of 106:16:1 (Redfield et al., 1963), although the mid-water dissolved N:P and N:Si values as well as the C:N:P ratios of remineralisation along isopycnals conform to the Redfield ratios at this site. Accounting for dissolved fluxes of all these elements brings the stoichiometry of export in agreement with the Redfield Ratio and with other geochemical estimates of winter mixed layer export. A factor of 3 to 4 higher ratios of organic: inorganic carbon export also implies that the net atmospheric CO 2 sequestration by the biological pump is about 50% higher at this site when the dissolved elemental fluxes are considered. Solubilization is thus a process that should be accounted for in protocols used to measure vertical fluxes with sediment traps.

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Global patterns of phytoplankton nutrient and light colimitation inferred from an optimality‐based model

Arteaga

Pahlow

Oschlies

2014

Global Biogeochemical Cycles

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The widely used concept of constant ”Redfield” phytoplankton stoichiometry is often applied for estimating which nutrient limits phytoplankton growth in the surface ocean. Culture experiments, in contrast, show strong relations between growth conditions and cellular stoichiometry with often substantial deviations from Redfield stoichiometry. Here we investigate to what extent both views agree by analyzing remote sensing and in situ data with an optimality‐based model of nondiazotrophic phytoplankton growth in order to infer seasonally varying patterns of colimitation by light, nitrogen (N), and phosphorus (P) in the global ocean. Our combined model‐data analysis suggests strong N and N‐P colimitation in the tropical ocean, seasonal light, and N‐P colimitation in the Northern Hemisphere, and strong light limitation only during winter in the Southern Ocean. The eastern equatorial Pacific appears as the only ocean area that is essentially not limited by N, P, or light. Even though our optimality‐based approach specifically accounts for flexible stoichiometry, inferred patterns of N and P limitation are to some extent consistent with those obtained from an analysis of surface inorganic nutrients with respect to the Redfield N:P ratio. Iron is not part of our analysis, implying that we cannot accurately predict N cell quotas in high‐nutrient, low‐chlorophyll regions. Elsewhere, we do not expect a major effect of iron on the relative distribution of N, P, and light colimitation areas. The relative importance of N, P, and light in limiting phytoplankton growth diagnosed here by combining observations and an optimal growth model provides a useful constraint for models used to predict future marine biological production under changing environmental conditions. © 2014. American Geophysical Union. All Rights Reserved.

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C:N ratios in the mixed layer during the productive season in the northeast Atlantic Ocean

Cited by 149 publications

References 82 publications

Oxygen, carbon, and nutrients in the oligotrophic eastern subtropical North Atlantic

Oxygen, carbon, and nutrients in the oligotrophic eastern subtropical North Atlantic

Solubilization of particles in sediment traps: revising the stoichiometry of mixed layer export

Global patterns of phytoplankton nutrient and light colimitation inferred from an optimality‐based model

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