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Special Session 1: Ecosystem under multiple stressors |
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Specific effects of low nitrate, low phosphate and ocean acidification on physiological responses of Emliania huxleyi to a verity of light intensities
Wednesday 11th @ 1047-1104
Multi-function Hall
Yong Zhang* , Institute of Ocean and Earth Sciences, Xiamen University
Kunshan Gao, Institute of Ocean and Earth Sciences, Xiamen University
Presenter Email: zhangyong1983@xmu.edu.cn
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| Rising pCO2 levels in the atmosphere increased the global average temperature and CO2 concentration in the surface ocean. Enhanced water column stratification due to ocean warming shoaled the upper mixed layer of the oceans, which increased the light intensity of phytoplankton exposure in this layer and may decrease the concentrations of nitrate and phosphate transported from deep water to surface. In this study, we investigated the specific effects of low nitrate (LN), low phosphate (LP) and high CO2 (HC) concentrations on physiological responses of Emiliania huxleyi to different light intensities. At all nutrients conditions, high CO2 decreased the growth, particulate organic (POC) and inorganic (PIC) carbon production rates. At low CO2 level (LC), maximum growth rate was increased by decreasing phosphate concentration; at high CO2 level, it was decreased by decreasing nitrate concentration. These showed that rising CO2 level enhanced the effect of low nitrate on growth rate but attenuated the effect of low phosphate on growth rate of E. huxleyi. Maximum PIC production rates were significantly larger at LN than at HNHP condition. Optimum light intensities were shifted toward lower levels for POC production at LN condition and for PIC production at LP condition. These indicate that high-light tolerances were decreased by LN for POC production, and by LP for PIC production. In order to acclimate to increasing light intensity, E. huxleyi tended to decrease Chl a and carotenoid contents at LN condition, and to increase non-photochemical quenching (NPQ) at LP condition, especially at high CO2 level. When exposure to incubation light intensities for 12 hours at both low and high CO2 levels, maximum photosynthetic carbon fixation and calcification rates were increased by decreasing nitrate and decreased by decreasing phosphate concentration. These results indicated that E. huxleyi showed different photo-acclimation mechanism including both light reaction and downstream metabolism to LN and LP conditions. This study provides an outlook on effects of multi environmental stress factors on a cosmopolitan phytoplankton. |
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