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Isotopic composition of sinking particles: Oil effects, recovery and baselines in the Gulf of Mexico, 2010–2015

Isotopic composition of sinking particles: Oil effects, recovery and baselines in the Gulf of Mexico, 2010–2015
Isotopic composition of sinking particles: Oil effects, recovery and baselines in the Gulf of Mexico, 2010–2015
The extensive release of oil during the 2010 Deepwater Horizon spill in the northern Gulf of Mexico perturbed the pelagic ecosystem and associated sinking material. To gauge the recovery and post-spill baseline sources, we measured Δ14C, δ13C and δ34S of sinking particles near the spill site and at a reference site and natural seep site. Particulates were collected August 2010–April 2016 in sediment traps moored at sites with depths of 1160–1660 m. Near the spill site, changes in Δ14C indicated a 3-year recovery period, while δ34S indicated 1–2 years, which agreed with estimates of 1–2 years based on hydrocarbon composition. Under post-spill baseline conditions, carbon inputs to sinking particulates in the northern Gulf were dominated by surface marine production (80–85%) and riverine inputs (15–20%). Near the spill site, Δ14C values were depleted in October 2010 (–140 to –80‰), increasing systematically by 0.07 ± 0.02‰ day–1 until July 2013 when values reached –3.2 ± 31.0‰. This Δ14C baseline was similar to particulates at the reference site (3.8 ± 31.1‰). At both sites, δ13C values stayed constant throughout the study period (–21.9 ± 0.5‰ and –21.9 ± 0.9‰, respectively). δ34S near the spill site was depleted (7.4 ± 3.1‰) during October 2010–September 2011, but enriched (16.9 ± 2.0‰) and similar to the reference site (16.2 ± 3.1‰) during November 2012–April 2015. At the seep site, Δ14C values were –21.7 ± 45.7‰ except during August 2012–January 2013 when a significant Δ14C depletion of –109.0 ± 29.1‰ was observed. We interpret this depletion period, also observed in δ13C data, as caused by the incorporation of naturally seeped oil into sinking particles. Determination of post-spill baselines for these isotopic signatures allows for evaluation of anthropogenic inputs in future.
2325-1026
43
Chanton, Jeffrey P.
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Giering, Sarah
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Bosman, Samantha H.
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Rogers, Kelsey L.
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Sweet, Julia
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Asper, Vernon
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Diericks, Arne R.
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Passow, Uta
56cfacd9-3579-4418-b17c-99d818fa7a2a
Chanton, Jeffrey P.
a6cbb960-c365-494a-bb1a-df329b02aff1
Giering, Sarah
e9b75287-e35e-414a-a5f2-cef9f2ab2efd
Bosman, Samantha H.
26b728fc-7636-47a2-b54c-25a153ef1850
Rogers, Kelsey L.
122c8151-a189-436d-842b-291ba1a283a7
Sweet, Julia
5039a891-3547-4a1a-89a8-558199863092
Asper, Vernon
07ef3e02-e08f-454c-a4ed-edb4b8538946
Diericks, Arne R.
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Passow, Uta
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Chanton, Jeffrey P., Giering, Sarah, Bosman, Samantha H., Rogers, Kelsey L., Sweet, Julia, Asper, Vernon, Diericks, Arne R. and Passow, Uta (2018) Isotopic composition of sinking particles: Oil effects, recovery and baselines in the Gulf of Mexico, 2010–2015. Elementa: Science of the Anthropocene, 6 (1), 43. (doi:10.1525/elementa.298).

Record type: Article

Abstract

The extensive release of oil during the 2010 Deepwater Horizon spill in the northern Gulf of Mexico perturbed the pelagic ecosystem and associated sinking material. To gauge the recovery and post-spill baseline sources, we measured Δ14C, δ13C and δ34S of sinking particles near the spill site and at a reference site and natural seep site. Particulates were collected August 2010–April 2016 in sediment traps moored at sites with depths of 1160–1660 m. Near the spill site, changes in Δ14C indicated a 3-year recovery period, while δ34S indicated 1–2 years, which agreed with estimates of 1–2 years based on hydrocarbon composition. Under post-spill baseline conditions, carbon inputs to sinking particulates in the northern Gulf were dominated by surface marine production (80–85%) and riverine inputs (15–20%). Near the spill site, Δ14C values were depleted in October 2010 (–140 to –80‰), increasing systematically by 0.07 ± 0.02‰ day–1 until July 2013 when values reached –3.2 ± 31.0‰. This Δ14C baseline was similar to particulates at the reference site (3.8 ± 31.1‰). At both sites, δ13C values stayed constant throughout the study period (–21.9 ± 0.5‰ and –21.9 ± 0.9‰, respectively). δ34S near the spill site was depleted (7.4 ± 3.1‰) during October 2010–September 2011, but enriched (16.9 ± 2.0‰) and similar to the reference site (16.2 ± 3.1‰) during November 2012–April 2015. At the seep site, Δ14C values were –21.7 ± 45.7‰ except during August 2012–January 2013 when a significant Δ14C depletion of –109.0 ± 29.1‰ was observed. We interpret this depletion period, also observed in δ13C data, as caused by the incorporation of naturally seeped oil into sinking particles. Determination of post-spill baselines for these isotopic signatures allows for evaluation of anthropogenic inputs in future.

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Accepted/In Press date: 12 May 2018
Published date: 30 May 2018

Identifiers

Local EPrints ID: 427345
URI: http://eprints.soton.ac.uk/id/eprint/427345
ISSN: 2325-1026
PURE UUID: 3e3422ee-285e-4e63-9d27-e8083bdf041b

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Date deposited: 14 Jan 2019 17:30
Last modified: 25 Nov 2021 22:21

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Contributors

Author: Jeffrey P. Chanton
Author: Sarah Giering
Author: Samantha H. Bosman
Author: Kelsey L. Rogers
Author: Julia Sweet
Author: Vernon Asper
Author: Arne R. Diericks
Author: Uta Passow

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