Effect of seafloor depth on phytoplankton blooms in high-nitrate, low-chlorophyll (HNLC) regions

Type Article
Date 2005-11
Language English
Author(s) Tyrrell T.1, Merico A.1, Waniek J. J.1, Wong C. S.2, Metzl N.3, Whitney F.2
Affiliation(s) 1 : Univ Southampton, Natl Oceanog Ctr Southampton, Southampton SO14 3ZH, Hants, England.
2 : Inst Ocean Sci, Sidney, BC V8L 4B2, Canada.
3 : Univ Paris 06, CNRS, IPSL, LOCEAN, F-75252 Paris, France.
Source Journal Of Geophysical Research-biogeosciences (2169-8953) (Amer Geophysical Union), 2005-11 , Vol. 110 , N. G02007 , P. 1-12
DOI 10.1029/2005JG000041
WOS© Times Cited 39
Keyword(s) phytoplankton, ocean color, bathymetry, HNLC, North Pacific, iron
Abstract We calculated correlations between seafloor depth and phytoplankton blooms in all three main high-nitrate, low-chlorophyll (HNLC) regions, but with a particular focus on the subarctic North Pacific area. It has long been known that the central parts of the east and west subarctic North Pacific are HNLC regions. The deep western basin of the Bering Sea is also HNLC, whereas the wide continental shelf of the eastern Bering Sea is not. We carried out a statistical comparison of spatial maps of (1) seafloor depth and (2) chlorophyll a concentration from satellite data. This comparison reveals that shallow waters have, on average, higher peak chlorophyll a concentrations (more intense phytoplankton blooms) than deep waters (p << 0.01). Possible artifacts of the satellite data are considered but it is concluded that the signal is genuine, in part because the same patterns are found in in situ data. There are several possible explanations for the observed correlation; the most probable, we suggest, is that iron diffusing out of the seafloor causes alleviation of iron limitation in shallow waters.
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