Episodic enhancement of phytoplankton stocks in New Zealand subantarctic waters: contribution of atmospheric and oceanic iron supply

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Title Episodic enhancement of phytoplankton stocks in New Zealand subantarctic waters: contribution of atmospheric and oceanic iron supply
Author Boyd, P. W.; McTainsh, Grant Harvey; Sherlock, V.; Richardson, K.; Nichol, S.; Ellwood, M.; Frew, R.
Journal Name Global Biogeochemical Cycles
Year Published 2004
Place of publication United States
Publisher American Geophysical Union
Abstract Around 30% of oceanic waters are high nitrate low chlorophyll (HNLC) where low iron levels limit algal growth. HNLC waters have mainly been studied using shipboard and lab experiments. Since 1997, remote-sensing of phytoplankton via SeaWiFS Ocean Color has permitted monitoring of the constancy of this “HNLC condition,” i.e., spatial homogeneity and low temporal variability of chlorophyll over annual cycles. These trends can be exploited, as episodic iron inputs should be conspicuous by subsequent expression as iron-elevated algal stocks. Subantarctic (SA) waters near New Zealand are HNLC, and the proximity of the arid Australian landmass, and the iron-rich Subtropical Front, provide natural laboratories to detect episodic atmospheric and oceanic iron supply, respectively. Two approaches were used: Oceanic supply was inferred from episodic increases in chlorophyll concentrations in SA waters, detected using Ocean Color archives. Additional archives were used to confirm the oceanic provenance of iron supply, and identify supply mechanism(s). Atmospheric supply was assessed using data on source areas and loads for dust storms monitored in central Australia. Dust transport and its fate was assessed using air mass forward trajectories and SeaWiFS Ocean Color and Aerosol Optical Depth maps. During 1997–2001, episodic elevated chlorophyll events occurred in SA waters southeast of New Zealand. There was no evidence of these events being mediated by atmospheric iron supply; however, neither wind-driven lateral advection or vertical mixing alone could account for these episodes. Dust storms, over this period sent plumes either into high iron SubTropical (ST) waters or into SA waters in early spring, when cells are probably light- rather than iron-limited.
Peer Reviewed Yes
Published Yes
Publisher URI http://www.agu.org/journals/gb/
Alternative URI http://dx.doi.org/10.1029/2002GB002020
Volume 18
Issue Number 1
Page from 1
Page to 23
ISSN 0886-6236
Date Accessioned 2005-03-29
Language en_AU
Faculty Faculty of Environmental Sciences
Subject PRE2009-Biological Oceanography
URI http://hdl.handle.net/10072/5209
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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