CARBON-ISOTOPE FRACTIONATION BY MARINE-PHYTOPLANKTON IN CULTURE - THE EFFECTS OF CO2 CONCENTRATION, PH, TEMPERATURE, AND SPECIES
CARBON-ISOTOPE FRACTIONATION BY MARINE-PHYTOPLANKTON IN CULTURE - THE EFFECTS OF CO2 CONCENTRATION, PH, TEMPERATURE, AND SPECIES
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DOI：
10.1029/93gb03393
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发表时间：
1994-03-01
影响因子：
5.2
通讯作者：
WHITAKER, D
中科院分区：
文献类型：
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作者：
HINGA, KR;ARTHUR, MA;WHITAKER, D
在不同的CO2浓度、温度、生长速率(受光照限制)和pH(但几乎相同的[CO2aq])条件下建立了海洋浮游植物的封闭培养，以评估这些变量对相对于溶解无机碳源的碳同位素分馏程度的相对影响。在封闭培养中，培养生物量的增加不得超过会显著影响溶解碳系统的水平。在对中肋骨条藻和虎纹草的实验中，增加二氧化碳浓度导致碳同位素辨别力增加(导致有机物逐渐消耗在DeltaC-13C中，即更大、更负的epsilon(P))。在相同条件下，湖北龙须草的Epsilon(P)值比中肋骨条藻低8-10ppm。对于中肋骨葡萄球菌的培养，这一比例接近20%。范围以依赖于[CO2aq]的epsilon(P)为单位。这种效应是非线性的，在高[CO2aq]时趋于平稳。在pH为7.5-8.3的范围内，但在恒定的[CO2aq]范围内，中肋骨链球菌的碳同位素分馏变化约为千分之九，在pH 7.8-7.9时最小。即使在考虑了CO2aq的DeltaC-13的平衡温度依赖性后，温度对分馏的影响也是-千分之八。在一定的生长速率范围内，没有发现中肋骨条藻的生长速率效应。用于确定浮游植物物种碳同位素分馏的培养实验必须在明确的温度、pH和二氧化碳浓度条件下进行。由于影响DeltaC-13org的各种可能因素，从海洋沉积物中有机碳的DeltaC-13测量得到的古代大气PCO2的后遗症将需要仔细校准。
Closed cultures of marine phytoplankton were established under variable conditions of CO2 concentration, temperature, growth rate (by light limitation), and pH (hut with nearly identical [CO2aq]) in order to assess the relative influence of these variables on the extent of carbon isotope fractionation relative to dissolved inorganic carbon sources. Culture biomass was not allowed to increase beyond levels that would significantly affect the dissolved carbon system in the closed cultures. In experiments with Skeletonema costatum and Emiliania huxleyi, increasing CO2 concentrations led to increased carbon isotope discrimination (resulting in organic matter progressively depleted in deltaC-13C, i.e., a greater, more negative epsilon(p)). Epsilon(p) values for E. huxleyi were 8-10 parts per thousand less than for S. costatum under identical conditions. For the S. costatum cultures, there was nearly a 20%. range in [CO2aq]-dependent epsilon(p). The effect was nonlinear with a leveling off at high [CO2aq]. Over a pH range of 7.5-8.3 but at a constant [CO2aq] there was a variation in carbon isotope fractionation by S. costatum of about 9 parts per thousand with a minimum at pH 7.8-7.9. There was a temperature effect of -8 parts per thousand on fractionation even after equilibrium temperature dependency of deltaC-13 of CO2aq was taken into account. No growth rate effect was found for S. costatum over a modest range of growth rates. Culture experiments used to determine the carbon isotope fractionation by phytoplankton species must be conducted under well-defined conditions of temperature, pH, and CO2 concentrations. Hindcasts of ancient atmospheric pCO2 from measurements of deltaC-13 of organic carbon in marine sediments will require careful calibration because of the variety of possible factors that influence deltaC-13org.