Publication Date:
2013-12-18
Description:
The North Pacific subtropical gyre (NPSG) plays a major part in the export of carbon and other nutrients to the deep ocean. Primary production in the NPSG has increased in recent decades despite a reduction in nutrient supply to surface waters. It is thought that this apparent paradox can be explained by a shift in plankton community structure from mostly eukaryotes to mostly nitrogen-fixing prokaryotes. It remains uncertain, however, whether the plankton community domain shift can be linked to cyclical climate variability or a long-term global warming trend. Here we analyse records of bulk and amino-acid-specific (15)N/(14)N isotopic ratios (delta(15)N) preserved in the skeletons of long-lived deep-sea proteinaceous corals collected from the Hawaiian archipelago; these isotopic records serve as a proxy for the source of nitrogen-supported export production through time. We find that the recent increase in nitrogen fixation is the continuation of a much larger, centennial-scale trend. After a millennium of relatively minor fluctuation, delta(15)N decreases between 1850 and the present. The total shift in delta(15)N of -2 per mil over this period is comparable to the total change in global mean sedimentary delta(15)N across the Pleistocene-Holocene transition, but it is happening an order of magnitude faster. We use a steady-state model and find that the isotopic mass balance between nitrate and nitrogen fixation implies a 17 to 27 per cent increase in nitrogen fixation over this time period. A comparison with independent records suggests that the increase in nitrogen fixation might be linked to Northern Hemisphere climate change since the end of the Little Ice Age.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sherwood, Owen A -- Guilderson, Thomas P -- Batista, Fabian C -- Schiff, John T -- McCarthy, Matthew D -- England -- Nature. 2014 Jan 2;505(7481):78-81. doi: 10.1038/nature12784. Epub 2013 Dec 15.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Ocean Sciences Department, University of California, Santa Cruz, California 95064, USA [2] Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80309, USA. ; 1] Ocean Sciences Department, University of California, Santa Cruz, California 95064, USA [2] Lawrence Livermore National Laboratory, Livermore, California 94550, USA [3] Institute for Marine Sciences, University of California, Santa Cruz, California 95064, USA. ; Ocean Sciences Department, University of California, Santa Cruz, California 95064, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24336216" target="_blank"〉PubMed〈/a〉
Keywords:
Amino Acids/chemistry
;
Animals
;
Anthozoa/chemistry/metabolism
;
Aquatic Organisms/*metabolism
;
Climate Change
;
Ecosystem
;
Hawaii
;
History, 15th Century
;
History, 16th Century
;
History, 17th Century
;
History, 19th Century
;
History, 20th Century
;
History, 21st Century
;
History, Ancient
;
History, Medieval
;
*Ice Cover
;
Nitrates/analysis
;
*Nitrogen Fixation
;
Nitrogen Isotopes/analysis
;
Pacific Ocean
;
Plankton/metabolism
;
Radiometric Dating
;
Seawater/chemistry
;
Time Factors
;
Tropical Climate
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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