Physiological variability amongst 10 newly isolated strains of the marine coccolithophore Emiliania huxleyi

Ten genetically distinct strains of Emiliania huxleyi were taken as environmental samples from wild populations in the North Atlantic and North Sea. The strains were grown in dilute batch cultures and initially, the ecologically relevant parameters of growth, photosynthesis and calcification were investigated. Significant variation in growth was found to occur, ranging between 0.48 – 1.02 cell divisions day-1 and significant variation in calcification rates were measured, ranging between 2.004 pg cell-1 day-1 – 4.526 pg cell-1 day-1 (inorganic carbon). The greatest level of variation was found amongst four of the strains sampled from the same location, suggesting a high level of genetic diversity within a wild population. Five of the ten strains were subsequently grown in dilute batch cultures at three pCO2 levels ranging from ~360 µatm to ~960 µatm. Growth rate, particulate organic carbon content and particulate inorganic carbon content were measured and organic and inorganic carbon production calculated. The five strains did not show a uniform response to carbonate system manipulations but were all found to follow an overall trend of decreased calcification and decreased PIC:POC ratios in response to elevated pCO2. The results show that the sensitivity and response of E. huxleyi strains from wild populations demonstrate a noteworthy degree of intraspecific variability, in line with response patterns reported from culture bank strains in similar investigations on ocean acidification impacts on calcification