Environmental carbonate chemistry selects for phenotype of recently isolated strains of Emiliania huxleyi

详细信息    查看全文

• 作者：Rosalind E.M. Rickaby^a ; ^{rosalind.rickaby@earth.ox.ac.uk" class="auth_mail" title="E-mail the corresponding author} ; Michaë ; l Hermoso^a ; Renee B.Y. Lee^a ; Benjamin D. Rae^a ; ^b ; Ana M.C. Heureux^a ; Cecilia Balestreri^c ; Leela Chakravarti^c ; Declan C. Schroeder^c ; Colin Brownlee^c
• 关键词：Coccolithophores ; Carbonate chemistry ; Photosynthesis ; Calcification ; Polysaccharides ; Stable isotopes ; Phytoplankton culture ; Photosynthesis ; Coccoliths ; Oxygen isotopes ; Coccolith-associated polysaccharides
• 刊名：Deep Sea Research Part II: Topical Studies in Oceanography
• 出版年：2016
• 出版时间：May 2016
• 年：2016
• 卷：127
• 期：Complete
• 页码：28-40
• 全文大小：2643 K

文摘

Coccolithophorid algae, particularly Emiliania huxleyi, are prolific biomineralisers that, under many conditions, dominate communities of marine eukaryotic plankton. Their ability to photosynthesise and form calcified scales (coccoliths) has placed them in a unique position in the global carbon cycle. Contrasting reports have been made with regards to the response of E. huxleyi to ocean acidification. Therefore, there is a pressing need to further determine the fate of this key organism in a rising CO₂ world. In this paper, we investigate the phenotype of newly isolated, genetically diverse, strains of E. huxleyi from UK Ocean Acidification Research Programme (UKOA) cruises around the British Isles, the Arctic, and the Southern Ocean. We find a continuum of diversity amongst the physiological and photosynthetic parameters of different strains of E. huxleyi morphotype A under uniform, ambient conditions imposed in the laboratory. This physiology is best explained by adaptation to carbonate chemistry in the former habitat rather than being prescribed by genetic fingerprints such as the coccolithophore morphology motif (CMM). To a first order, the photosynthetic capacity of each strain is a function of both aqueous CO₂ availability, and calcification rate, suggestive of a link between carbon concentrating ability and calcification. The calcification rate of each strain is related linearly to the natural environmental [CO₃²⁻] at the site of isolation, but a few exceptional strains display low calcification rates at the highest [CO₃²⁻] when calcification is limited by low CO₂ availability and/or a lack of a carbon concentrating mechanism. We present O₂-electrode measurements alongside coccolith oxygen isotopic composition and the uronic acid content (UAC) of the coccolith associated polysaccharide (CAP), that act as indirect tools to show the differing carbon concentrating ability of the strains. The environmental selection revealed amongst our recently isolated strain collection points to the future outcompetition of the slow growing morphotypes B/C and R (which also lack a carbon concentrating mechanism) by more rapidly photosynthesising, and lightly calcified strains of morphotype A but with their rate of calcification highly dependent on the surface ocean saturation state. The mechanism of E. huxleyi response to carbonate chemistry in the modern ocean appears to be selection from a continuum of phenotype.