Autonomous oceanic primary production through novel chlorophyll fluorometry

海洋浮游植物负责地球上大约一半的初级生产。因此，这些微生物构成了海洋食物链的基础，也是碳和营养物质的行星地球化学循环的关键组成部分。浮游植物初级生产力在各大洋之间差异很大，从与锋面和漩涡等物理现象有关的几公里空间尺度到在整个海洋盆地观察到的强烈梯度。此外，浮游植物的光合速率响应环境强迫的形式，通过气候时间尺度的光和营养物质的可用性在次日常。然而，我们对浮游植物光合作用的时空变化的理解受到海洋系统极端采样不足的严重阻碍，这最终限制了我们对海洋生产力大小的最佳估计的信心。主动叶绿素荧光测定法是一项突破性的技术，有可能通过促进高质量的光合速率原位测量来克服这一采样问题;特别是如果这种仪器可以发展到可以在自主观测平台上常规部署的程度。目前可用的仪器不足以达到这一目的。这个博士项目旨在填补这一关键的技术空白，促进在前所未有的规模上更好地了解海洋光合作用的变化。

Oceanic phytoplankton are responsible for approximately half the primary production on Earth. These microbes hence constitute both the base of the marine food-chain and a crucial component of the planetary biogeochemical cycles of carbon and nutrients. Phytoplankton primary production varies widely across the oceans from spatial scales of a few km associated with physical phenomena such as fronts and eddies, to the strong gradients observed across whole ocean basins. Moreover, phytoplankton photosynthetic rates respond to environmental forcing in the form of light and nutrient availability at sub-daily through to climatic time scales. However, our understanding of this spatio-temporal variability in phytoplankton photosynthesis is severely hampered by extreme under-sampling of marine systems, which ultimately limits confidence in our best estimates of the magnitude of oceanic productivity. Active chlorophyll fluorometry represents a groundbreaking technology with the potential to overcome this sampling problem through facilitating high quality in situ measurements of photosynthetic rates; especially if such instrumentation can be developed to the point where it can be deployed routinely on autonomous observational platforms. Currently available instrumentation is inadequate for this purpose. This PhD project aims to fill this crucial technological gap, facilitating improved understanding of the variability of oceanic photosynthesis across unprecedented scales.