The carbon isotopic fractionation accompanying formation of biomass by alkenone-producing algae in natural marine environments varies systematically with the concentration of dissolved phosphate. Specifically, if the fractionation is expressed by epsilon p approximately delta e - delta p, where delta e and delta p are the delta 13C values for dissolved CO2 and for algal biomass (determined by isotopic analysis of C37 alkadienones), respectively, and if Ce is the concentration of dissolved CO2, micromole kg-1, then b = 38 + 160*[PO4], where [PO4] is the concentration of dissolved phosphate, microM, and b = (25 - epsilon p)Ce. The correlation found between b and [PO4] is due to effects linking nutrient levels to growth rates and cellular carbon budgets for alkenone-containing algae, most likely by trace-metal limitations on algal growth. The relationship reported here is characteristic of 39 samples (r2 = 0.95) from the Santa Monica Basin (six different times during the annual cycle), the equatorial Pacific (boreal spring and fall cruises as well as during an iron-enrichment experiment), and the Peru upwelling zone. Points representative of samples from the Sargasso Sea ([PO4] < or = 0.1 microM) fall above the b = f[PO4] line. Analysis of correlations expected between mu (growth rate), epsilon p, and Ce shows that, for our entire data set, most variations in epsilon p result from variations in mu rather than Ce. Accordingly, before concentrations of dissolved CO2 can be estimated from isotopic fractionations, some means of accounting for variations in growth rate must be found, perhaps by drawing on relationships between [PO4] and Cd/Ca ratios in shells of planktonic foraminifera.

中文翻译：

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自然界和实验室中 13C 的一致分馏：一些触藻藻类的生长速率效应

伴随着自然海洋环境中产生烯酮的藻类形成生物质的碳同位素分馏随溶解磷酸盐的浓度而系统地变化。具体来说，如果分馏由 epsilon p 表示大约 delta e - delta p，其中 delta e 和 delta p 分别是溶解 CO2 和藻类生物量的 delta 13C 值（通过 C37 链二烯酮的同位素分析确定），如果是溶解的 CO2 浓度，微摩尔 kg-1，然后 b = 38 + 160*[PO4]，其中 [PO4] 是溶解磷酸盐的浓度 microM，b = (25 - epsilon p)Ce。在 b 和 [PO4] 之间发现的相关性是由于将营养水平与含烯酮藻类的生长速率和细胞碳预算联系起来的影响，最有可能是由于微量金属对藻类生长的限制。此处报告的关系是来自圣莫尼卡盆地（年度周期中的六个不同时间）、赤道太平洋（北方春季和秋季航行以及铁富集实验期间）的 39 个样本 (r2 = 0.95) 的特征，以及秘鲁上升流带。代表马尾藻海样本的点 ([PO4] < 或 = 0.1 microM) 落在 b = f[PO4] 线以上。对 mu（增长率）、epsilon p 和 Ce 之间预期相关性的分析表明，对于我们的整个数据集，epsilon p 的大多数变化源于 mu 而非 Ce 的变化。因此，在通过同位素分馏估算溶解的 CO2 浓度之前，必须找到一些解释增长率变化的方法，