Are foraminifera what they eat?

在海洋中，被称为浮游植物的微观植物利用二氧化碳、光和营养物质产生有机物质，这些有机物质提供了海洋食物链的基础。二氧化碳转化为有机物的过程称为光合作用。碳元素在地球上以三种形式存在，质子数量相同，但中子数量增加：99%的碳以碳-12（6个质子，6个中子）的形式存在，约1%的碳-13（6个质子，7个中子）的形式存在，还有一小部分碳-14（6个质子，8个中子）。在光合作用过程中，植物会主动区分较重的碳13（较小的原子更容易被吸收），从而导致碳12的相对富集。二氧化碳和有机物中碳的碳-13 /碳-12（=碳同位素）比值的比较提供了分馏的测量方法。在大西洋内，浮游植物的碳同位素比率通常与生产力有关，与低生产力地区相比，高生产力地区的浮游植物的碳同位素比率要高得多。如果我们能在地质样品上测量浮游植物的有机碳同位素，我们可能能够获得该地区过去生产力变化的信息。问题在于：(1)形成有机物质的许多蛋白质在埋在沉积物中后可能会降解；(2)从大块沉积物中提取的有机物质（不可能只从浮游植物中提取有机物质）可能来自其他几种来源（包括陆生植物，或从其他地方的深海洋流携带的旧物质），因此可能不能代表实际的地表水条件。这项研究计划将测试浮游有孔虫（生活在海面附近并以浮游植物为食的浮游动物）有机碳同位素是否也跟踪生产力，以评估其在海洋生产力历史重建中的应用。

In the oceans microscopic plants called phytoplankton use carbon dioxide, light and nutrients to produce organic matter, which provides the basis of the marine food-chain. The process where carbon dioxide is converted into organic matter is termed photosynthesis. The element carbon occurs on earth in three forms, with the same amount of protons, but increasing neutrons: 99% of carbon exists like carbon-12 (6 protons, 6 neutrons), ~1% as carbon-13 (6 protons, 7 neutrons), and a minute fraction of carbon-14 (6 protons, 8 neutrons). Plants actively discriminate against the heavier carbon-13 during photosynthesis (it is easier to incorporate the smaller atom) causing relative enrichment in carbon-12. Comparison of the ratio of carbon-13 over carbon-12 (=carbon isotope) of the carbon in carbon dioxide and that of organic matter provides a measure of fractionation. Within the Atlantic Ocean the carbon isotope ratio of phytoplankton generally tracks productivity, with phytoplankton from high productivity regions having considerably higher carbon isotopic ratios compared with low productivity regions. If we could measure phytoplankton organic carbon isotopes on geological samples we might be able to obtain information of past productivity changes in the area. The problem is that (1) many of the proteins that form the organic material may degrade after burial in sediments, (2) the organic material extracted from bulk sediments (it is not possible to just extract organic material from phytoplankton material) may be sourced from several other sources (including terrestrial plants, or old material carried by a deep sea current from somewhere else), and so may not represent actual surface water conditions. This research proposal will test whether planktonic foraminifera (zooplankton that live near the sea surface and eats phytoplankton) organic carbon isotopes also track productivity, to assess it's application for historical reconstructions of marine productivity.