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Calcification morphotypes of the coccolithophorid Emiliania huxleyi in the Southern Ocean: changes in 2001 to 2006 compared to historical data


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Cubillos, JC and Wright, SW and Nash, G and de Salas, MF and Griffiths, B and Tilbrook, B and Poisson, A and Hallegraeff, GM (2007) Calcification morphotypes of the coccolithophorid Emiliania huxleyi in the Southern Ocean: changes in 2001 to 2006 compared to historical data. Marine Ecology - Progress Series, 348. pp. 47-54. ISSN 0171-8630

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We conducted a scanning electron microscopic survey of morphological variations in the
calcareous nanoplankton species Emiliania huxleyi in Southern Ocean surface water samples
collected along a transect from 43 to 64° S and 141 to 145° E during November 2001, October to
February 2002/2003, 2003/2004, 2004/2005 and 2005/2006. The results were compared with historical
data from a similar transect occupied in December to January 1983/1984 and January to February
1994 and 1995. While E. huxleyi was absent or extremely sparse (0.1 to 1 cells ml–1) south of 60° S
in 1983/1984 and 1994/1995, this species was consistently present at about 100 cells ml–1 between
60 and 65° S during 2002 to 2006. The extended geographic range and/or increased southward
abundance of this keystone species suggests a significant shift in Southern Ocean ecology over the
past 2 decades, analogous to an observed recent range extension into the Bering Sea. Morphotype A
‘overcalcified’ mainly occurred north of the Subantarctic Front and was replaced by the weakly
calcified Morphotype B/C between the Subantarctic Front and Southern Antarctic Circumpolar
Current Front. This north–south shift in E. huxleyi calcification morphotypes closely tracked the
north–south decline in the calcite saturation state as calculated from carbonate system measurements.
Based on current evidence, no significant changes are apparent in the calcification status of E.
huxleyi in the Southern Ocean during the past 12 yr. All cultured isolates from north of the Polar
Front belonged to Morphotype A, while all strains isolated south of the Polar Front belonged to Morphotype
B/C and their morphologies appeared conservative in culture. The north–south trend of
decreased calcification of E. huxleyi in the Southern Ocean thus reflects the shift in dominance of one
ecotype to another, rather than the environmental effect of decreased carbonatre ion concentrations
and calcite saturation state on a single, ‘apparently cosmopolitan’, population.

Item Type: Article
Journal or Publication Title: Marine Ecology - Progress Series
Publisher: Inter-Research
Page Range: pp. 47-54
ISSN: 0171-8630
Identification Number - DOI: 10.3354/meps07058
Additional Information:

Copyright © 2007 InterResearch

Date Deposited: 07 Apr 2008 14:09
Last Modified: 18 Nov 2014 03:33
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