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Global declines in oceanic nitrification rates as a consequence of ocean acidification

Global declines in oceanic nitrification rates as a consequence of ocean acidification
Global declines in oceanic nitrification rates as a consequence of ocean acidification
Ocean acidification produced by dissolution of anthropogenic carbon dioxide (CO2) emissions in seawater has profound consequences for marine ecology and biogeochemistry. The oceans have absorbed one-third of CO2 emissions over the past two centuries, altering ocean chemistry, reducing seawater pH, and affecting marine animals and phytoplankton in multiple ways. Microbially mediated ocean biogeochemical processes will be pivotal in determining how the earth system responds to global environmental change; however, how they may be altered by ocean acidification is largely unknown. We show here that microbial nitrification rates decreased in every instance when pH was experimentally reduced (by 0.05–0.14) at multiple locations in the Atlantic and Pacific Oceans. Nitrification is a central process in the nitrogen cycle that produces both the greenhouse gas nitrous oxide and oxidized forms of nitrogen used by phytoplankton and other microorganisms in the sea; at the Bermuda Atlantic Time Series and Hawaii Ocean Time-series sites, experimental acidification decreased ammonia oxidation rates by 38% and 36%. Ammonia oxidation rates were also strongly and inversely correlated with pH along a gradient produced in the oligotrophic Sargasso Sea (r2 = 0.87, P < 0.05). Across all experiments, rates declined by 8–38% in low pH treatments, and the greatest absolute decrease occurred where rates were highest off the California coast. Collectively our results suggest that ocean acidification could reduce nitrification rates by 3–44% within the next few decades, affecting oceanic nitrous oxide production, reducing supplies of oxidized nitrogen in the upper layers of the ocean, and fundamentally altering nitrogen cycling in the sea.
0027-8424
208-213
Beman, J. Michael
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Chow, Cheryl-Emiliane
5b7899db-25f3-4c94-a7c7-997907db0538
King, Andrew L.
8bfe9bd0-21d9-4deb-925c-acb996fc1d18
Feng, Yuanyuan
98b2ad15-0f5c-4644-b312-c57dedd77e65
Fuhrman, Jed A.
bbab10ae-1a33-41b4-90e3-f875f06ea53a
Andersson, Andreas
3bdfbb05-6c6a-42d6-84c9-4a7ac3a53390
Bates, Nicholas R.
954a83d6-8424-49e9-8acd-e606221c9c57
Popp, Brian
8833810f-8262-42ab-8aa5-5dbccc91323a
Hutchins, David A.
22662c12-8eb0-4279-8217-a6313f2c528e
Beman, J. Michael
f95bd04c-2580-4112-a6b8-173240977d3e
Chow, Cheryl-Emiliane
5b7899db-25f3-4c94-a7c7-997907db0538
King, Andrew L.
8bfe9bd0-21d9-4deb-925c-acb996fc1d18
Feng, Yuanyuan
98b2ad15-0f5c-4644-b312-c57dedd77e65
Fuhrman, Jed A.
bbab10ae-1a33-41b4-90e3-f875f06ea53a
Andersson, Andreas
3bdfbb05-6c6a-42d6-84c9-4a7ac3a53390
Bates, Nicholas R.
954a83d6-8424-49e9-8acd-e606221c9c57
Popp, Brian
8833810f-8262-42ab-8aa5-5dbccc91323a
Hutchins, David A.
22662c12-8eb0-4279-8217-a6313f2c528e

Beman, J. Michael, Chow, Cheryl-Emiliane, King, Andrew L., Feng, Yuanyuan, Fuhrman, Jed A., Andersson, Andreas, Bates, Nicholas R., Popp, Brian and Hutchins, David A. (2011) Global declines in oceanic nitrification rates as a consequence of ocean acidification. Proceedings of the National Academy of Sciences, 108 (1), 208-213. (doi:10.1073/pnas.1011053108).

Record type: Article

Abstract

Ocean acidification produced by dissolution of anthropogenic carbon dioxide (CO2) emissions in seawater has profound consequences for marine ecology and biogeochemistry. The oceans have absorbed one-third of CO2 emissions over the past two centuries, altering ocean chemistry, reducing seawater pH, and affecting marine animals and phytoplankton in multiple ways. Microbially mediated ocean biogeochemical processes will be pivotal in determining how the earth system responds to global environmental change; however, how they may be altered by ocean acidification is largely unknown. We show here that microbial nitrification rates decreased in every instance when pH was experimentally reduced (by 0.05–0.14) at multiple locations in the Atlantic and Pacific Oceans. Nitrification is a central process in the nitrogen cycle that produces both the greenhouse gas nitrous oxide and oxidized forms of nitrogen used by phytoplankton and other microorganisms in the sea; at the Bermuda Atlantic Time Series and Hawaii Ocean Time-series sites, experimental acidification decreased ammonia oxidation rates by 38% and 36%. Ammonia oxidation rates were also strongly and inversely correlated with pH along a gradient produced in the oligotrophic Sargasso Sea (r2 = 0.87, P < 0.05). Across all experiments, rates declined by 8–38% in low pH treatments, and the greatest absolute decrease occurred where rates were highest off the California coast. Collectively our results suggest that ocean acidification could reduce nitrification rates by 3–44% within the next few decades, affecting oceanic nitrous oxide production, reducing supplies of oxidized nitrogen in the upper layers of the ocean, and fundamentally altering nitrogen cycling in the sea.

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e-pub ahead of print date: 20 December 2010
Published date: 4 January 2011
Organisations: Ocean Biochemistry & Ecosystems

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Local EPrints ID: 356538
URI: https://eprints.soton.ac.uk/id/eprint/356538
ISSN: 0027-8424
PURE UUID: 9704a06b-122a-48d9-880d-0d73e2df104c

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Date deposited: 06 Sep 2013 09:22
Last modified: 18 Jul 2017 03:38

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Contributors

Author: J. Michael Beman
Author: Cheryl-Emiliane Chow
Author: Andrew L. King
Author: Yuanyuan Feng
Author: Jed A. Fuhrman
Author: Andreas Andersson
Author: Brian Popp
Author: David A. Hutchins

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