Isotopic composition of suspended particulate nitrogen (δ15Nsus) in surface waters of the Atlantic Ocean from 50°N to 50°S

Mino, Yoshihisa; Saino, Toshiro; Suzuki, Koji; Marañón, Emilio

doi:10.1029/2001gb001635

Cited by 52 publications

(45 citation statements)

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“…2) were within the range (-28 to -12‰ and -1.5 to 19‰, respectively) reported in surface water at middle latitude in the northern hemisphere (Rau et al, 1982(Rau et al, , 1998(Rau et al, , 2001Saino andHattori, 1985, 1987;Altabet, 1989;Altabet et al, 1991;Saino, 1992;Goericke and Fry, 1994;Minagawa et al, 2001;Mino et al, 2002). The C/N of 5.6 to 9.9 at 0-10 m depth fell within the range of plankton of 5-12 (Tyson, 1995).…”

Section: Sediments Off Tokachisupporting

confidence: 57%

Distribution and sources of organic matter in surficial sediments on the shelf and slope off Tokachi, western North Pacific, inferred from C and N stable isotopes and C / N ratios

et al. 2006

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Organic carbon (C) and total nitrogen (N) contents and corresponding isotope ratios were determined in surficial sediment (0-3 cm) at 94 stations ranging from 21 to 1995 m water depth off Tokachi, Hokkaido, Japan, to elucidate the distribution and source of sedimentary organic matter. Suspended particulate organic matter (POM) in the seawater and suspended POM and sediment in the Tokachi River were also examined. River mouth, and the sedimentary organic matter from 134 to 1995 m water depth was of marine origin. The organic C content in the sediment was high near the Tokachi River mouth, and also around 1000 m water depth. The C content was significantly correlated with silt plus clay content, with different regression lines for those stations shallower and deeper than 134 m, owing to several stations of higher C content with the elevated C/N ratio on the inner shelf. These results suggest that transport and deposition of organic-rich fine sediment particles by hydrodynamic processes were major factors 3 controlling C content off Tokachi. In addition, the supply of a fraction of terrestrial organic matter with high C/N probably also affected C content on the inner shelf.

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Section: Sediments Off Tokachisupporting

confidence: 57%

Distribution and sources of organic matter in surficial sediments on the shelf and slope off Tokachi, western North Pacific, inferred from C and N stable isotopes and C / N ratios

et al. 2006

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“…This study, confined to the open ocean, revealed consistently higher δ 15 N values (by up to 5 ‰) below the surface layer and small variability with either depth or geographical location, with all values falling between 9 and 11 ‰ north of the equator. Surface-layer values were lower, but still substantially above (>6 ‰) the normal oceanic range (e.g., Altabet, 1989;Mino et al, 2002;Montoya et al, 2002). The only exception to this general trend was found in the region affected by a Trichodesmium bloom where δ 15 N fell to ∼4 ‰.…”

Section: Introductionmentioning

confidence: 89%

Intra-annual variability of carbon and nitrogen stable isotopes in suspended organic matter in waters of the western continental shelf of India

et al. 2011

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Abstract. Intra-annual variations of δ 13 C and δ 15 N of watercolumn suspended particulate organic matter (SPOM) have been investigated to understand the biogeochemical cycling of C and N in the Western Continental Shelf of India (WCSI). The key issues being addressed are: how the δ 15 N of SPOM is affected by seasonally varying processes of organic matter production and respiration and how it relates to the δ 15 N of sedimentary organic matter that appears to show a decreasing trend despite an apparent intensification of seasonal oxygen deficiency over the past few decades? A secondary objective was to evaluate the sources of organic carbon. Elemental carbon and nitrogen concentrations, C/N ratios in SPOM, along with ancillary chemical and biological variables including phytoplankton pigment abundance were also determined on a seasonal basis (from March 2007 to September 2008), with the partial exception of the southwest (SW) monsoon period. The results reveal significant shifts in isotopic signatures, especially δ 15 N, of SPOM before and after the onset of SW monsoon. Very low δ 15 N values, reaching a minimum of −4.17 ‰, are found during the pre-monsoon period. Our results provide the first direct evidence for the addition of substantial amounts of isotopically light nitrogen by the diazotrophs, especially Trichodesmium, in the region. The δ 15 N of SPOM is generally lower than the mean value (7.38 ‰) for surficial sediments, presumably because of diagenetic enrichment. The results support the view that sedimentary δ 15 N may not necessarily reflect denitrification intensity in the overlying waters due to diverse sources of nitrogen and variability of its isotopic composition. The observed intra-annual variability of δ 13 C of SPOM during the pre-monsoon and post-monsoon periods is generally small. Phytoplankton production and probably species composition could drive some of the observed changes. The largest changes (depletion of Correspondence to: M. V. Maya (mmayae11@gmail.com) δ 13 C and increase in C/N) appear to occur during the preand post-monsoon seasons, presumably through episodic deposition of terrestrial organic matter from the atmosphere. During the SW monsoon, when a large input of terrestrial organic matter is expected through runoff from land, the C/N ratio remains low, but significant difference is observed between δ 13 C data in 2007 and 2008. Inputs of soil organic matter that may have elemental and isotopic signatures different from those of the conventional (C 3 plant derived) organic matter could explain the constancy of the C/N ratio.

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“…These values are the typical concentrations of organic nitrogen in oligotrophic oceans (e.g. Minagawa et al, 2001;Mino et al, 2002;Meador et al, 2007).…”

Section: Geochemical Data Analysismentioning

confidence: 98%

Determination of total N 2 fixation rates in the ocean taking into account both the particulate and filtrate fractions

et al. 2010

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Abstract. Using the 15 N 2 tracer method and high-sensitivity δ 15 N analytical systems, we determined N 2 fixation rates for ocean samples by dividing them into particulate (>0.7 µm) and filtrate (<0.7 µm) fractions. While N 2 fixation in the filtrate fraction had been ignored in previous studies, we found a significant N 2 fixation rates in the filtrate fraction in our study. The areal N 2 fixation rates in the western North Pacific Ocean estimated from the particulate fraction varied from <1 to 160 µmol N m −2 d −1 , and those rates estimated from the filtrate fraction ranged from <0.5 to 54 µmol N m −2 d −1 . Thus, N 2 fixation in the filtrate fraction accounts for on average 50% (ranging from <10% to 84%) of the total N 2 fixation rates. If these results are confirmed generally in the ocean, the new total N 2 fixation flux, which includes fixation in the filtrate fraction, possibly doubles the original estimates; therefore, the revised influx may reduce the imbalance in the global oceanic fixed nitrogen budget.

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Isotopic composition of suspended particulate nitrogen (δ¹⁵N_sus) in surface waters of the Atlantic Ocean from 50°N to 50°S

Abstract: [1] Isotopic composition of suspended particulate nitrogen (d 15 N sus ) has been studied in near-surface waters along a transect extending from 50°N to 50°S in the Atlantic Ocean.

Cited by 52 publications

References 62 publications

Distribution and sources of organic matter in surficial sediments on the shelf and slope off Tokachi, western North Pacific, inferred from C and N stable isotopes and C / N ratios

Distribution and sources of organic matter in surficial sediments on the shelf and slope off Tokachi, western North Pacific, inferred from C and N stable isotopes and C / N ratios

Intra-annual variability of carbon and nitrogen stable isotopes in suspended organic matter in waters of the western continental shelf of India

Determination of total N <sub>2</sub> fixation rates in the ocean taking into account both the particulate and filtrate fractions

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Isotopic composition of suspended particulate nitrogen (δ15Nsus) in surface waters of the Atlantic Ocean from 50°N to 50°S

Abstract: [1] Isotopic composition of suspended particulate nitrogen (d 15 N sus ) has been studied in near-surface waters along a transect extending from 50°N to 50°S in the Atlantic Ocean.

Cited by 52 publications

References 62 publications

Distribution and sources of organic matter in surficial sediments on the shelf and slope off Tokachi, western North Pacific, inferred from C and N stable isotopes and C / N ratios

Distribution and sources of organic matter in surficial sediments on the shelf and slope off Tokachi, western North Pacific, inferred from C and N stable isotopes and C / N ratios

Intra-annual variability of carbon and nitrogen stable isotopes in suspended organic matter in waters of the western continental shelf of India

Determination of total N &lt;sub&gt;2&lt;/sub&gt; fixation rates in the ocean taking into account both the particulate and filtrate fractions

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Isotopic composition of suspended particulate nitrogen (δ¹⁵N_sus) in surface waters of the Atlantic Ocean from 50°N to 50°S

Determination of total N <sub>2</sub> fixation rates in the ocean taking into account both the particulate and filtrate fractions