Feasibility of using an automated colorimetric procedure for the determination of seawater nitrate in the 0 to 100 nM range: Examples from field and culture

Raimbault, Patrick; Slawyk, Gerd; Coste, B.; Fry, Juliane L.

doi:10.1007/bf01313277

Cited by 121 publications

(68 citation statements)

References 13 publications

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“…For nitrate and nitrite determination, samples were taken into 250-ml polyethylene flasks and analyzed on board immediately using a semiautomatic Technicon Autonanalyser ® II, according to Raimbault et al (1990), for both low-nitrate waters (<500 nmoles l −1 ; detection limit = 3 nmoles l −1 ) and for high-nitrate waters (>500 nmoles l −1 ; detection limit = 0.05 µmoles l −1 ) according to Tréguer and le Corre (1975). Ammonium concentrations (40 ml collected in 50 ml Schott glass bottles) were measured using the fluorometric method (Holmes et al, 1999; detection limit = 0.005 µmoles l −1 ).…”

Section: Methodsmentioning

confidence: 99%

Evidence for efficient regenerated production and dinitrogen fixation in nitrogen-deficient waters of the South Pacific Ocean: impact on new and export production estimates

2008

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Abstract.One of the major objectives of the BIOSOPE cruise, carried out on the R/V Atalante from OctoberNovember 2004 in the South Pacific Ocean, was to establish productivity rates along a zonal section traversing the oligotrophic South Pacific Gyre (SPG). These results were then compared to measurements obtained from the nutrient -replete waters in the Chilean upwelling and around the Marquesas Islands. A dual 13 C/ 15 N isotope technique was used to estimate the carbon fixation rates, inorganic nitrogen uptake (including dinitrogen fixation), ammonium (NH 4 ) and nitrate (NO 3 ) regeneration and release of dissolved organic nitrogen (DON). The SPG exhibited the lowest primary production rates (0.15 g C m −2 d −1 ), while rates were 7 to 20 times higher around the Marquesas Islands and in the Chilean upwelling, respectively. In the very low productive area of the SPG, most of the primary production was sustained by active regeneration processes that fuelled up to 95% of the biological nitrogen demand. Nitrification was active in the surface layer and often balanced the biological demand for nitrate, especially in the SPG. The percentage of nitrogen released as DON represented a large proportion of the inorganic nitrogen uptake (13-15% in average), reaching 26-41% in the SPG, where DON production played a major role in nitrogen cycling. Dinitrogen fixation was detectable over the whole study area; even in the Chilean upwelling, where rates as high as 3 nmoles l −1 d −1 were measured. In these nutrient-replete waters new production was very high (0.69±0.49 g C m −2 d −1 ) and essentially sustained by nitrate levels. In the SPG, dinitrogen fixation, although occurring at much lower daily rates (≈1-2 nmoles l −1 d −1 ), sustained up to 100% of the new production (0.008±0.007 g C m −2 d −1 ) which was two orders of magnitude lower than that measured in the upwelling. The annual N 2 -fixation of the South PacificCorrespondence to: P. Raimbault (patrick.raimbault@univmed.fr) is estimated to 21×10 12 g, of which 1.34×10 12 g is for the SPG only. Even if our "snapshot" estimates of N 2 -fixation rates were lower than that expected from a recent ocean circulation model, these data confirm that the N-deficiency South Pacific Ocean would provide an ideal ecological niche for the proliferation of N 2 -fixers which are not yet identified.

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Section: Methodsmentioning

confidence: 99%

Evidence for efficient regenerated production and dinitrogen fixation in nitrogen-deficient waters of the South Pacific Ocean: impact on new and export production estimates

2008

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“…Nanomolar concentrations of nitrate were determined on-board on fresh samples using a segmentedflow automatic analyser (Technicon/Bran Luebbe) and following the method of Raimbault et al (1990). To determine the concentration of dissolved reactive phosphate, water samples were collected and stored frozen at -20°C until analysed in the laboratory with the same segmented-flow automatic analyser, following standard colorimetric methods (Grasshoff, 1976).…”

Section: Nutrient Concentrationsmentioning

confidence: 99%

Size-fractionated phytoplankton biomass and production in the tropical Atlantic

Moreno-Ostos¹,

Fernández²,

Huete-Ortega³

et al. 2010

Sci. Mar.

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SUMMARY: Two meridional transects were conducted in the tropical and subtropical Atlantic to describe (i) the spatial variability of total and size-fractionated (picophytoplankton and phytoplankton >2 mm) chlorophyll a (chl a) concentration and primary production, (ii) the relative contribution of each phytoplankton size fraction to total biomass and carbon fixation, and (iii) the spatial variability of size-fractionated phytoplankton growth rate (P/B) and assimilation number (P/chl a) in the ocean. The highest chl a for both size fractions was observed in the Western Tropical Atlantic province (WTRA), while the lowest chl a was found in the upper mixed layer (UML) of the South Atlantic Tropical gyre (SATL). A similar pattern was found for carbon fixation. Within the SATL, the highest picophytoplankton contribution to total production was recorded at the Deep Chlorophyll Maximum (DCM), while the contribution of phytoplankton >2 mm was higher in the UML. Additionally, the relative contribution of large phytoplankton to total integrated primary production was higher than its contribution to total biomass. Both size fractions depicted maximum P/B and P/chl a in WTRA surface waters. In the SATL province, phytoplankton >2 mm showed the highest P/B and P/chl a along the UML, while picophytoplankton P/B and P/chl a peaked around the DCM. We suggest that the differential impact of light on small and large phytoplankton may help to explain the contrasting dynamics of the two size classes.Keywords: phytoplankton, cell size, spatial variability, oligotrophic subtropical gyres, primary production, biomass.RESUMEN: Biomasa y producción en diferentes clases de tamaño de fitoplancton en el Atlántico tropical.-Se realizaron dos transectos latitudinales en el Atlántico tropical y subtropical para describir (i) la variabilidad espacial de la concentración de clorofila a (chl a) y de la producción primaria total y fraccionada en clases de tamaño de fitoplancton (picofitoplancton y fitoplancton >2 mm), (ii) la contribución relativa de cada clase de tamaño a la biomasa y fijación de carbono total, y (iii) la variabilidad espacial de la tasa de crecimiento (P/B) y del número de asimilación (P/chl a) para cada clase de tamaño en el océano. Las dos clases de tamaño consideradas presentaron la máxima chl a en el afloramiento ecuatorial y la mínima en la capa de mezcla del giro oligotrófico del Atlántico Sur. Se encontró un patrón similar en el caso de la fijación de carbono. En el giro oligotrófico del Atlántico Sur la mayor contribución del picofitoplancton a la producción total se registró en torno al máximo profundo de clorofila, mientras que la contribución de la fracción >2 mm fue mayor en la capa de mezcla. Además, la contribución relativa del fitoplancton >2 mm a la producción primaria total fue mayor que su contribución a la biomasa total. Ambas clases de tamaño presentaron máximos valores de P/B y P/chl a en las aguas superficiales del afloramiento ecuatorial. En el giro oligotrófico del Atlántico Sur la fracción de fitoplancto...

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“…Ambient nitrate, nitrite and phosphate concentrations were measured immediately by pumping the 250 ml sample through a Technicon AutoAnalyzer®. Nitrate and nitrite concentrations in the nanomolar range (lower detection limit=3 nmoles l −1 ) were obtained using the sensitive method of Raimbault et al (1990). Nitrate at submicromolar levels (detection limit 0.05 µmoles l −1 ) and phosphate (detection limit 0.02 µmoles l −1 ) were measured according to the method of Armstrong et al (1967).…”

Section: Inorganic Nutrientsmentioning

confidence: 99%

“…The main objective of this work is to describe inorganic and organic distributions by comparing the different environmental conditions covered by the BIOSOPE cruise. Since ambient concentrations are often below the detection limit of conventional analytical procedures (Brzezinski, 1985;Garside 1985;Sahlsten, 1987;) the more sensitive methods of Garside (1982), Raimbault et al (1990) and Holmes et al (1999) have to be employed in order to detect the trace nutrients. In this paper we describe spatial and vertical distributions of inorganic and organic nutrients in the South Pacific in particular in the oligotrophic SPG.…”

Section: Introductionmentioning

confidence: 99%

Distribution of inorganic and organic nutrients in the South Pacific Ocean − evidence for long-term accumulation of organic matter in nitrogen-depleted waters

2008

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Abstract. During the BIOSOPE cruise the RV Atalante was dedicated to study the biogeochemical properties in the South Pacific between the Marquesas Islands (141 • W-8 • S) and the Chilean upwelling (73 • W-34 • S). Over the 8000 km covered by the cruise, several different trophic situations were encountered, in particular strong oligotrophic conditions in the South Pacific Gyre (SPG, between 123 • W and 101 • W). In this isolated region, nitrate was undetectable between the surface and 160-180 m and only trace quantities (<20 nmoles l −1 ) of regenerated nitrogen (nitrite and ammonium) were detected, even in the subsurface maximum. Integrated nitrate over the photic layer, which reached 165 m, was close to zero. Despite this severe nitrogendepletion, phosphate was always present in significant concentrations (≈0.1 µmoles l −1 ), while silicic acid was maintained at low but classical oceanic levels (≈1 µmoles l −1 ). In contrast, the Marquesas region (MAR) to the west and Chilean upwelling (UPW) to the east were characterized by high nutrient concentrations, one hundred to one thousand fold higher than in the SPG. The distribution of surface chlorophyll reflected the nitrate gradient, the lowest concentrations (0.023 nmoles l −1 ) being measured at the centre of the SPG, where integrated value throughout the photic layer was very low (≈ 10 mg m −2 ). However, due to the relatively high concentrations of chlorophyll-a encountered in the DCM (0.2 µg l −1 ), chlorophyll-a concentrations throughout the photic layer were less variable than nitrate concentrations (by a factor 2 to 5). In contrast to chlorophyll-a, integrated particulate organic matter (POM) remained more or less constant along the study area (500 mmoles m −2 , 60 mmoles m −2 and 3.5 mmoles m −2 for particulate organic carbon, particulate organic nitrogen and particulate organic phosphorus, Correspondence to: P. Raimbault (patrick.raimbault@univmed.fr) respectively), with the exception of the upwelling, where values were two fold higher. The residence time of particulate carbon in the surface water was only 4-5 days in the upwelling, but up to 30 days in the SPG, where light isotopic δ 15 N signal noted in the suspended POM suggests that N 2 -fixation provides a dominant supply of nitrogen to phytoplankton. The most striking feature was the large accumulation of dissolved organic matter (DOM) in the SPG compared to the surrounding waters, in particular dissolved organic carbon (DOC) where concentrations were at levels rarely measured in oceanic waters (>100 µmoles l −1 ). Due to this large pool of DOM in the SPG photic layer, integrated values followed a converse geographical pattern to that of inorganic nutrients with a large accumulation in the centre of the SPG. Whereas suspended particulate matter in the mixed layer had a C/N ratio largely conforming to the Redfield stochiometry (C/N≈6.6), marked deviations were observed in this excess DOM (C/N≈16 to 23). The marked geographical trend suggests that a net in situ source exists, mainly due to biologic...

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Feasibility of using an automated colorimetric procedure for the determination of seawater nitrate in the 0 to 100 nM range: Examples from field and culture

Cited by 121 publications

References 13 publications

Evidence for efficient regenerated production and dinitrogen fixation in nitrogen-deficient waters of the South Pacific Ocean: impact on new and export production estimates

Evidence for efficient regenerated production and dinitrogen fixation in nitrogen-deficient waters of the South Pacific Ocean: impact on new and export production estimates

Size-fractionated phytoplankton biomass and production in the tropical Atlantic

Distribution of inorganic and organic nutrients in the South Pacific Ocean − evidence for long-term accumulation of organic matter in nitrogen-depleted waters

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