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

Marine Ecology Progress Series

Ray Barlow¹  Anja van der Plas¹  Jorijntje Henderiks¹  Guenther Nausch¹  Rainer Feistel¹  Amos Winter¹  Malte Elbr#xe4chter¹ 

关键词: Emiliania huxleyi;    Morphology;    Ecology;    Plankton succession;    Coastal upwelling;    Namibia;   

DOI  :  10.3354/meps09535

学科分类：海洋学与技术

来源: Inter-Research

【 摘 要 】

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.

【 授权许可】

Unknown