Iron Biogeochemistry in the High Latitude North Atlantic

自工业革命开始以来，由于燃烧化石燃料和砍伐森林，二氧化碳的浓度显著增加。二氧化碳影响着地球的气候，它的浓度现在如此之高，以至于地球的大气层正在变暖，天气变得更加极端。海洋中的小型漂浮植物，称为浮游植物，从大气中吸收二氧化碳，从而有助于降低大气浓度。浮游植物细胞也需要氮、磷和硅等营养物质来生长。近年来，人们发现世界海洋许多地区的浮游植物缺乏铁。例如，在南大洋，浮游植物细胞的生长受到非常低的铁浓度的限制。因此，这片海洋中的浮游植物并没有像理想条件下那样从大气中去除尽可能多的二氧化碳。许多人认为，北大西洋通过撒哈拉沙漠的尘埃运输获得了足够的铁。然而，最近的实验表明，即使在北大西洋浮游植物细胞可能缺乏铁。在这个项目中，我们想研究铁是否限制了北大西洋高纬度（>60 N）浮游植物的生长。为了实现这一目标，我们将参加3次研究航行，并采集水、沉积物和大气尘埃和雨水的样本。我们将分析样品中的铁和营养盐，并计算Fe与N、P、C向表层海洋的供应比例，以及它们在沉积物中的比例。我们将使用模型来帮助我们计算这些元素的海洋转移。如果浮游植物在高纬度北大西洋受到铁的限制，那么这将是因为它们获得的铁与其他营养物质相比太低了。我们还将直接调查铁是否限制了高纬度北大西洋水样中浮游植物的生长。为了找到答案，我们将在船甲板上的透明瓶中培养从海洋表面采集的浮游植物细胞。我们将在一些瓶子中添加铁，而其他瓶子将完全不添加铁。浮游植物的生长和生理状态将通过测量色素（叶绿素a）浓度等来确定。这些测量结果将告诉我们，与我们没有添加Fe的瓶子相比，添加Fe的瓶子是否显示出更高数量的浮游植物细胞和更高的生长。拟议项目的结果将使我们更好地了解铁等营养物质在海洋浮游植物细胞生长中的作用。收集的数据将帮助计算机建模人员设计改进的气候模型，使我们能够更好地预测未来100年气候变化的范围。

The concentration of carbon dioxide has increased significantly since the start of the industrial revolution as a result of burning of fossil fuels and deforestation. Carbon dioxide influences the climate on earth and its concentration is now so high that the earth's atmosphere is warming and the weather is becoming more extreme. Small floating plants in the ocean, called phytoplankton, take up carbon dioxide from the atmosphere and that way help to reduce the atmospheric concentrations. The phytoplankton cells also need nutrients like nitrogen, phosphorus and silicon to grow. Recently, it has been discovered that the phytoplankton in many regions of the world's oceans are lacking Fe. For example, in the Southern Ocean the growth of the phytoplankton cells is limited by very low Fe concentrations. Therefore, the phytoplankton in this ocean do not remove as much carbon dioxide from the atmosphere as they could do under ideal conditions. Many people think that the North Atlantic Ocean receives enough Fe through dust transport from the Sahara. However, recent experiments have shown that even in the North Atlantic phytoplankton cells may be lacking Fe. In this project, we want to study whether Fe is limiting phytoplankton growth in the North Atlantic at higher latitudes (>60 N). In order to achieve this, we will take part in 3 research cruises and take samples of water, sedimenting material, and atmospheric dust and rain. We will analyse Fe and nutrients in the samples and calculate the supply ratios of Fe to N, P, C to the surface oceans, and their ratios in sedimenting material. We will use models to aid us with the calculations for the oceanic transfers of these elements. If the phytoplankton are Fe limited in the high latitude N Atlantic then it will be because the amount of Fe they get in relation to other nutrients is too low. We will also directly investigate whether Fe is limiting the growth of phytoplankton in water samples from the high latitude N Atlantic. To find this out, we will grow phytoplankton cells taken from the surface ocean in transparent bottles on the deck of the ship. We will add Fe to some bottles, whereas other bottles will receive no added Fe at all. The growth and physiological state of the phytoplankton will be determined using a number of measurements, such as pigment (chlorophyll a) concentrations. These measurements will show us whether the bottles with added Fe show a higher number of phytoplankton cells and a higher growth, compared with the bottles to which we added no Fe. The results of the proposed project will provide us with a better understanding of the role that nutrients like Fe play in the growth of phytoplankton cells in the ocean. The gathered data will help the computer modellers to design improved climate models that will allow us to better predict the extend of climate change over the next 100s of years.