MEPS 448:51-66 (2012)  -  DOI:

Environmental controls on Emiliania huxleyi morphotypes in the Benguela coastal upwelling system (SE Atlantic)

Jorijntje Henderiks1,*, Amos Winter2, Malte Elbrächter3, Rainer Feistel4, Anja van der Plas5, Guenther Nausch4, Ray Barlow6

1Department of Earth Sciences, Uppsala University, Villavägen 16, 75 236, Uppsala, Sweden
2Department of Marine Sciences, University of Puerto Rico, Mayaguez, PR 00681-9000, Puerto Rico
3Alfred Wegener Institute for Polar and Marine Research, Wattenmeerstation Sylt, Hafenstr. 43, 25992 List/Sylt, Germany
4IOW-Leibniz Institute for Baltic Sea Research, Warnemünde, 18119 Rostock, Germany
5NatMIRC, MFMR (National Marine Information & Research Centre, Ministry of Fisheries & Marine Resources), PO Box 912, Swakopmund, Namibia
6Bayworld Centre for Research & Education, 7806 Cape Town, South Africa

ABSTRACT: Two distinct morphotypes of the coccolithophore Emiliania huxleyi were observed as part of the phytoplankton succession offshore of Namibia, where coastal upwelling created strong gradients in sea surface temperature (SST), salinity, and nutrient conditions. The sampled surface waters hosted a characteristic succession of phytoplankton communities: diatoms bloomed in newly upwelled waters above the shelf, whereas dense coccolithophore communities dominated by E. huxleyi were found farther offshore, in progressively aging upwelled waters. A substantially calcified E. huxleyi morphotype (labeled Type A*) dominated plankton assemblages at stations influenced by upwelling, that immediately succeeded coastal diatom blooms. This morphotype caused a chlorophyll and 19’-hexanoyloxyfucoxanthin (19’-HF) maximum with >1 • 106 cells l−1, straddling a pycnocline at 17 m depth where the in situ N:P ratio was •13. Farther offshore, within <20 nautical miles distance, populations of Type A* drastically declined, and a more delicate morphotype with thin distal shield elements and open central area (Type B/C) was found. This morphotype was most abundant (~0.2 • 106 cells l−1) in high-phosphate, nitrogen-depleted surface waters (N:P • 8), where it co-existed with other coccolithophores, most notably Syracosphaera spp. Extensive surface blooms of coccolithophores observed by satellites in the same region in the past were identified by microscopy as being produced by E. huxleyi and S. pulchra. However, blooms of E. huxleyi at greater depths in the euphotic zone, such as those observed in this study, will go undetected by satellites and thus underestimate coccolithophore biomass and calcification within upwelling regions.

KEY WORDS: Emiliania huxleyi · Morphology · Ecology · Plankton succession · Coastal upwelling · Namibia

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Cite this article as: Henderiks J, Winter A, Elbrächter M, Feistel R, van der Plas A, Nausch G, Barlow R (2012) Environmental controls on Emiliania huxleyi morphotypes in the Benguela coastal upwelling system (SE Atlantic). Mar Ecol Prog Ser 448:51-66.

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