The ecophysiological basis for co-variability in light-limited and saturated rates of phytoplankton photosynthesis.

浮游植物是一种多样化的单细胞生物，生活在阳光照射的海洋上层。这些生物负责海洋中光能到化学能的绝大部分光合作用转化。因此，浮游植物构成了海洋食物链的基础，并最终负责每年由生物介导的全球氧气生产和从大气中去除二氧化碳的一半左右。由于它们在控制这些主要元素的循环中起着关键作用，我们必须了解是什么控制了浮游植物的光合作用，以及这些生物最终对持续的气候变化有多敏感。了解浮游植物对全球影响的必要的第一步是精确测量它们吸收的碳量。浮游植物的碳固定可以很好地近似为光合作用可用光量和吸收这些光的色素叶绿素量的函数。这两个变量都可以通过多种方法精确测量，从小型船舶测量到利用地球观测卫星进行的大规模全年重复测量。然而，将浮游植物的碳固定简单地处理为色素与光的乘积，忽略了浮游植物生理上的重要变异性。事实上，海洋中浮游植物将吸收的光转化为碳的效率差异很大。目前对这种变化的解释很差，给我们对每年固定碳量的最佳估计带来了很大的不确定性。目前的研究旨在通过研究浮游植物光合作用在一系列环境中无法解释的变化的特定方面来解决这种不确定性。在研究巡航期间，我们将同时测量浮游植物的整体光吸收率（相当于光合作用装置将光子转化为电子）和碳固定率。同时，我们将测量一些我们怀疑造成光吸收和碳固定比率无法解释的变化的因素。通过这项工作，我们不仅将增加我们对这些重要生物生理学的理解，而且还将在提高我们目前对浮游植物碳固定的最佳估计的准确性方面取得重大进展。

The phytoplankton are a diverse group of single celled organisms which live in the sunlit upper layer of the oceans. These organisms are responsible for the vast majority of the photosynthetic conversion of light energy to chemical energy in oceans. Phytoplankton thus form the basis of the marine food chain and are ultimately responsible for around half the biologically mediated global production of oxygen and removal of carbon dioxide from the atmosphere each year. Due to their key role in controlling the cycles of these major elements, it is important that we understand what controls phytoplankton photosynthesis and ultimately how susceptible these organisms might be to ongoing climate change. A necessary first step in understanding the global impact of phytoplankton is an accurate measure of the amount of carbon they take up. Phytoplankton carbon fixation can be reasonably well approximated as a function of the amount of light available for photosynthesis and the amount of the pigment, chlorophyll, which absorbs this light. Both of these variables can be accurately measured using a number of methods ranging from small scale ship based measurements to large scale year round repeated measurements using earth observing satellites. However, a simplistic treatment of phytoplankton carbon fixation simply as pigment multiplied by light ignores important variability in phytoplankton physiology. Indeed, the efficiency with which phytoplankton convert the light they absorb into carbon varies hugely in the oceans. Much of this variability is currently poorly explained, introducing large uncertainties into our best estimates of the amount of carbon fixed each year. The current study aims to address some of this uncertainty by studying a specific aspect of unexplained variability in phytoplankton photosynthesis in a range of environments. During research cruises we will make simultaneous measurements of the overall rate of phytoplankton light absorption (which is equivalent to the conversion of photons of light to electrons in their photosynthetic apparatus) and the rate of carbon fixation. At the same time we will measure a number of factors which we suspect are responsible for causing the unexplained variability in the ratio of light absorption and carbon fixation. By performing this work we will not only increase our understanding of the physiology of these important organisms, but will also make significant progress towards increasing the accuracy of our current best estimates of phytoplankton carbon fixation.