Nitrogen isotope dynamics of the Cariaco Basin, Venezuela
Open accessAbstract
We report 15 N/ 14 N measurements of water column nitrate and ammonium, sinking particles, and sediments from the Cariaco Basin, an anoxic marine basin off the coast of Venezuela. Water column denitrification occurring in the basin has only a very small isotopic imprint on nitrate in the basin because nitrate consumption is nearly complete in the actively denitrifying water near the oxic/anoxic interface (∼275 m). Being free of a large denitrification signal, the δ 15 N of shallow thermocline nitrate is ∼3.5‰, significantly lower than the mean deep ocean nitrate δ 15 N of 5‰. This may be due to the nitrification of newly fixed N, whether it occurs within the basin or in open Atlantic waters that flow into the Cariaco over the sill. The 15 N/ 14 N of the sinking flux in the deepest trap (∼1250 m) is similar to that of thermocline nitrate, as expected given the complete consumption of nitrate in the surface layer. Moreover, the 15 N/ 14 N of the seafloor sediment is similar to that of the sinking flux, as is common in environments of high export production, low O 2 , and good organic matter preservation. Thus the modern Cariaco Basin records the 15 N/ 14 N of the thermocline nitrate, which, in turn, may record the input of newly fixed N to the upper ocean, be it local or more regional in origin.
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In highly productive ocean-margin settings, sediments usually preserve the δ15N of thermocline nitrate.
“Because sediments deposited in highly productive ocean-margin environments typically record the δ 15 N of thermocline NO3 -(e.g., Thunell et al., 2004)”
From The chromium isotope composition of reducing and oxic marine sediments (2016) · cites this paper as Thunell et al., 2004
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Self-citation
- Authors
- Thunell, R. C., Sigman, D. M., Muller‐Karger, F., Astor, Y., & Varela, R.
- Affiliations
- University of South Carolina (US)
- Princeton University (US)
- College of Marine Science University of South Florida St. Petersburg Florida USA
- Fundación La Salle de Ciencias Naturales (VE)
- Fundacion La Salle de Ciencias Naturales, Estacion de Investigaciones Marinas de Margarita Isla de Margarita Venezuela
- Corresponding author
- Thunell, Robert C.
- Venue
- Global Biogeochemical Cycles
- Publisher
- American Geophysical Union (AGU)
- Published
- 2004-07
- Volume
- 18
- Issue
- 3
- ISSN
- 0886-6236 (ISSN-L)
- 1944-9224
- OpenAlex
- W1557365420
- Cited by
- 185
- References
- 73
- Citations by year
- 2026: 7 · 2025: 14 · 2024: 12 · 2023: 7 · 2022: 9 · 2021: 10 · 2020: 6 · 2019: 11 · 2018: 9 · 2017: 2 · 2016: 7 · 2015: 7 · 2014: 14 · 2013: 9 · 2012: 5
- FWCI
- 7.04
- Type
- journal article
- Language
- en
- Open access
- Locations
- Global Biogeochemical Cycles (publishedVersion)
- Digital Commons - University of South Florida (University of South Florida) (submittedVersion)
- Topics
- Physical Sciences › Earth and Planetary Sciences › Oceanography › Marine and coastal ecosystems
- Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Stratigraphy of Fossils
- Physical Sciences › Earth and Planetary Sciences › Geochemistry and Petrology › Groundwater and Isotope Geochemistry
- Keywords
- nitrogen isotopes, Cariaco Basin, anoxic basins, ammonium, denitrification, nitrification, sinking particles, marine sediment, thermocline, export production, organic matter preservation
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