Sedimentary nitrogen isotopic ratio as a recorder for surface ocean nitrate utilization
Mark A. Altabet
Search for more papers by this authorRoger Francois
Search for more papers by this authorMark A. Altabet
Search for more papers by this authorRoger Francois
Search for more papers by this authorAbstract
In two contrasting regions of the ocean, the equatorial Pacific and the southern ocean, the δ15N of core top sediments were strongly related to [NO3−] in surface waters. With distance from the equator in the equatorial Pacific, δ15N increased from 7‰ to 16‰ as [NO3−] decreased from 8μM to < 0.1 μM. Going from 60° to 30° S in the SE Indian Ocean, core top δ15N increased from 5‰ to 11‰ as surface [NO3−] decreased from 25μM to < 0.1 μM. These results are strong evidence that sedimentary δ15N in these regions is recording the increasing isotopic enrichment of near-surface NO3− with its depletion by phytoplankton. In the case of the equatorial Pacific, δ15N values for sinking particles collected at 150 m matched well the core top sediment values, demonstrating little diagenetic alteration of the near-surface generated isotopic signal. These equatorial Pacific data sets have variations with near-surface [NO3−] consistent with Rayleigh fractionation kinetics for a fractionation factor (ϵu) of 2.5‰. This value is substantially lower than previously found for temperate or polar regions, perhaps as a result of differences in phytoplankton species assemblage or growth condition. In the southern ocean south of the polar front, comparison of δ15N values for opal-rich sediments south and sinking particles indicates an apparent +5‰ diagenetic enrichment relative to the surface-generated signal that requires further investigation. This exception aside, our observations show that the surface-water relationship of increasing δ15N with increasing NO3− depletion is generally transmitted to and preserved in the sediments, an important requirement for further development and application of this important paleoceanographic tool.
References
- Altabet, M. A., Variations in nitrogen isotopic composition between sinking and suspended particles: Implications for nitrogen cycling and particle transformation in the open ocean, Deep Sea Res., Part A, 35, 535–554, 1988.
- Altabet, M. A., A time-series study of the vertical structure of nitrogen and particle dynamics in the Sargasso Sea, Limnol. Oceanogr., 24, 1185–1201, 1989.
- Altabet, M. A., W. B. Curry, Testing models of past ocean chemistry using foraminiferal 15N/14N, Global Biogeochem. Cycles, 3, 107–119, 1989.
- Altabet, M. A., W. G. Deuser, Seasonal variations in natural abundance of 15N in particles sinking to the deep Sargasso Sea, Nature, 315, 218–219, 1985.
- Altabet, M. A., andR. Francois, The use of nitrogen isotopic ratio for reconstruction of past changes in surface ocean nutrient utilization, in Carbon Cycling in the Glacial Ocean: Constraints on the Ocean's Role in Global Change, edited by R. Zahn, M. Kaminski, L. Labeyrie, and T. F. Pederson, NATO ASI Series, in press,1993.
- Altabet, M. A., J. J. McCarthy, Temporal and spatial variations in the natural abundance of 15N in PON from a warm-core ring, Deep Sea Res., Part A, 32, 755–772, 1985.
- Altabet, M. A., J. J. McCarthy, Vertical patterns in 15N natural abundance in PON from the surface waters of warm-core rings, J. Mar. Res., 44, 185–201, 1986.
- Altabet, M. A., L. F. Small, Nitrogen isotopic ratios in fecal pellets produced by marine zooplankton, Geochim. Cosmochim. Acta, 54, 155–163, 1990.
- Altabet, M. A., W. G. Deuser, S. Honjo, S. Stienen, Seasonal and depth-related changes in the source of sinking particles in the N. Atlantic, Nature, 354, 136–139, 1991.
- Barber, R. T., F. P. Chavez, Regulation of primary productivity rate in the equatorial Pacific Ocean, Limnol. Oceanogr., 36, 1803–1815, 1991.
- Biggs, D. C., S. P. Berkowitz, M. A. Altabet, R. R. Bidigare, D. J. DeMaster, R. B. Dunbar, A. Leventer, S. A. Macko, C. A. Nittrouer, M. E. Ondrusek, A cooperative study of upper-ocean particulate fluxes in the Weddell Sea, Proc. Ocean Drill. Program Initial Rep., 113, 77–86, 1988.
- Biggs, D. C., S. P. Berkowitz, M. A. Altabet, R. R. Bidigare, D. J. DeMaster, S. A. Macko, M. E. Ondrusek, I. L. Noh, A cooperative study of upper ocean particulate fluxes, Proc. Ocean Drill. Program Initial Rep., 119, 109–120, 1989.
- Boyle, E. A., Cadmium: Chemical tracer of deepwater paleoceanography, Paleoceanography, 3, 471–489, 1988.
- Calvert, S. E., B. Nielsen, M. R. Fontugne, Evidence from nitrogen isotope ratios for enhanced productivity during formation of eastern Mediterranean sapropels, Nature, 359, 223–225, 1992.
- Charles, C. D., R. F. Fairbanks, Glacial-interglacial changes in the isotopic gradients of southern ocean surface water, The Geologic History of Polar Oceans: Arctic vs Antarctic U. Bleil, J. Thiede, NATO ASI Series, 308, 519–538, 1990.
- Charles, C. D., P. N. Froelich, M. A. Zibello, A. Mortlock, J. J. Morley, Biogenic opal in southern ocean sediments over the last 450,000 years: implications for surface water chemistry and circulation, Paleoceanography, 6, 697–728, 1991.
- Chavez, F. P., Size distributions of phytoplankton in the Central and Eastern Tropical Pacific, Global Biogeochem. Cycles, 3, 27–36, 1989.
- Chavez, F. P., R. T. Barber, An estimate of new production in the equatorial Pacific, Deep Sea Res., Part A, 34, 1229–1243, 1987.
- Checkley Jr., D. M., C. A. Miller, Nitrogen isotope fractionation by oceanic zooplankton, Deep Sea Res., Part A, 36, 1449–1456, 1989.
- Chen, C. A., A. Poisson, C. Goyet, Preliminary data report for the INDIVAT I and INDIGO/INDIVAT 3 cruises in the Indian OceanDOE/NBB-0074U.S. Dep. of Energy, Washington, D.C., 1986.
- Cline, J. D., I. R. Kaplan, Isotopic fractionation of dissolved nitrate during denitrification in the Eastern Tropical North Pacific Ocean, Mar. Chem., 3, 271–299, 1975.
- DeNiro, M. J., S. Epstein, Influence of diet on the distribution of nitrogen isotopes in animals, Geochim. Cosmochim. Acta, 45, 341–351, 1981.
- Edwards, R. J., W. J. Emery, Australian southern ocean frontal structure during summer 1976–77, Aust. J. Mar. Freshwater Res., 33, 3–22, 1982.
- Eppley, R. W., F. P. Chavez, R. T. Barber, Standing stocks of particulate carbon and nitrogen in the equatorial Pacific at 150° W, J. Geophys. Res., 97, 655–661, 1992.
- Francois, R., M. A. Altabet, L. H Burkle, Glacial to interglacial changes in surface nitrate utilization in the Indian sector of the southern ocean as recorded by sediment δ15N, Paleoceanography, 7, 589–606, 1992.
- Francois, R., M. P. Bacon, M. A. Altabet, L. D. Labeyrie, Glacial/intergalcial changes in sediment rain rate in the S.W. Indian sector of Subantarctic waters as recorded by 230Th, 231Pa, U, and S15N, Paleoceanography, 8, 611–630, 1993.
- Fry, B., Food web structure on Georges Bank from stable C, N, and S isotopic compositions, Limnol. Oceanogr., 33, 1182–1190, 1988.
- Goering, J., V. Alexander, N. Haubenstock, Seasonal variability of stable carbon and nitrogen isotopic ratios of organisms in a North Pacific bay, Estuarine Coastal Shelf Sci., 30, 239–260, 1990.
- Gordon, A. L., E. J. Molinelli, Southern Ocean Atlas: Thermohaline and Chemical Distribution Data Set, Columbia University Press, New York, 1982.
- Keigwin, L. D., E. A. Boyle, Late quaternary paleochemistry of high-latitude surface waters, Palaeogeogr. Palaeoclimatol. Palaeoecol., 73, 85–106, 1989.
- Knauer, G. A., J. H. Martin, K. Bruland, Fluxes of particulate carbon, nitrogen, and phosphorous in the upper water column of the northeast Pacific, Deep Sea Res., Part A, 26, 97–108, 1979.
- Knox, F., M. McElroy, Changes in atmospheric CO2 influence of the marine biota at high latitude, J. Geophys. Res., 89, 4629–4637, 1984.
- Kumar, N., R. Gwiazda, R. F. Anderson, P. N. Froelich, 231Pa/230Th ratios in sediments as a proxy for past changes in southern ocean productivity, Nature, 362, 45–48, 1993.
- Labeyrie, L. D., J.-C. Duplessy, Changes in the oceanic 13/12C ratio during the last 140,000 years: High latitude surface water records, Palaeogeogr., Palaeoclimatol., Palaeoecol., 50, 217–240, 1985.
- Liu, K.-K., I. R. Kaplan, The eastern tropical Pacific as a source of 15N-enriched nitrate in seawater off southern California, Limnol. Oceanogr., 34, 820–830, 1989.
- Macko, S. A., Stable isotope organic geochemistry of sediments from the Labrador Sea (sites 646 and 647) and Baffin Bay (site 645), ODP leg 105, Proc. Ocean Drill. Program Sci. Results, 105, 209–221, 1989.
- Macko, S. A., P. G. Pereira, Neogene paleoclimate development of the Antarctic Weddell sea region: Organic geochemistry, Proc. Ocean Drill. Program Sci. Results, 113, 881–893, 1990.
- Minagawa, M., E. Wada, Stepwise enrichment of 15N along food chains: Further evidence and the relation between δ15N and animal age, Geochim. Cosmochim. Acta, 48, 1135–1140, 1984.
- Minagawa, M., D. A. Winter, I. R. Kaplan, Comparison of Kjeldahl and combustion methods for measurement of nitrogen isotope ratios in organic matter, Anal. Chem., 56, 1859–1861, 1985.
- Miyake, Y., E. Wada, The abundance of 15N/14N in marine environments, Rec. Oceanogr. Works Jpn., 9, 37–53, 1967.
- Montoya, J. P., Natural abundance of 15N in marine and estuarine plankton: Studies of biological isotopic fractionation and plankton processes, Ph.D. thesis,Harvard Univ.,Cambridge, Mass.,1990.
- Muzuka, A. N. N., S. A. Macko, T. F. Pederson, Stable carbon and nitrogen isotope compositions of organic matter from sites 724 and 725, Oman margin, Proc. Ocean Drill. Program Sci. Results, 117, 571–586, 1991.
- Park, Y.-H., L. Gamberoni, E. Charriaud, Frontal structure and transport of the Antarctic Circumpolar Current in the south Indian Ocean sector, 40 to 80°E, Mar. Chem., 35, 45–62, 1991.
- Rau, G. H., M. A. Arthur, W. E. Dean, 15N/14N variations in cretaceous Atlantic sedimentary sequences: Implication for past changes in marine nitrogen biogeochemistry, Earth Planet. Sci. Lett., 82, 269–279, 1987.
- Rau, G. H., C. W. Sullivan, L. I. Gordon, δ13C and δ15N variations in Weddell Sea particulate organic matter, Mar. Chem., 35, 355–369, 1991.
- Saino, T., A. Hattori, 15N natural abundance in oceanic suspended particulate matter, Nature, 283, 752–754, 1980.
- Saino, T., A. Hattori, Geographical variation in the water column distribution of suspended particulate organic nitrogen and its 15N natural abundance in the Pacific and its marginal seas, Deep Sea Res., Part A, 34, 807–827, 1987.
- Sarmiento, J. L., R. Toggweiler, A new model for the role of the oceans in determining atmospheric pCO2, Nature, 308, 621–624, 1984.
- Siegenthaler, U., T. Wenk, Rapid atmospheric CO2 variations and ocean circulation, Nature, 308, 624–626, 1984.
- Toggweiler, R., J. L. Sarmiento, Glacial to interglacial changes in atmospheric carbon dioxide: The critical role of ocean surface water in high latitudes, The Carbon Cycle and Atmospheric CO2: Natural Variations Archean to Present, Geophys. Monogr. Ser., 32 E. T. Sundquist, W. S. Broecker, 163–184, AGU, Washington, D.C., 1985.
10.1029/GM032p0163 Google Scholar
- Wada, E., Nitrogen isotope fractionation and its significance in biogeochemical processes occurring in marine environments, Isot. Mar. Chem E. D. Goldberg, Y. Horibe, 375–398, 1980.
- Wada, E., A. Hattori, Natural abundance of 15N in particulate organic matter in the North Pacific Ocean, Geochim. Cosmochim. Acta, 40, 249–251, 1976.
- Wada, E., A. Hattori, Nitrogen isotope effects in the assimilation of inorganic nitrogenous compounds by marine diatoms, Geomicrobiol. J., 1, 85–101, 1978.
- Wada, E., M. Terazaki, Y. Kabaya, T. Nemoto, 15N and 13C abundances in the Antarctic Ocean with emphasis on the biogeochemical structure of the food web, Deep Sea Res., Part A, 34, 829–841, 1987.
- Weiss, R. F., W. S. Boecker, H. Craig, D. Spencer, Hydrographic data in GeoSecs Indian Ocean Expedition, 5, U.S. Govt. Print. Office, Washington, D.C., 1983.