Historically, oceanographers have used the pigment chlorophyll-a as the primary currency of photosynthetic biomass because it is relatively simple to measure in seawater and is found in all marine phytoplankton. Yet, both the light reactions of photosynthesis that ultimately fuel the metabolism of photoautotrophs and the colour of the ocean used to detect chlorophyll biomass from space are related to the absorption of photons by all phytoplankton pigments and not just chlorophyll-a. Using bio-optical measurements collected across the global ocean (from field observations and from satellites), this project will look beyond chlorophyll-a and develop a mechanistic understanding of how light energy is processed by the ocean’s microflora whose growth supports the rest of marine life and makes phytoplankton a key player in the global carbon cycle.
Methodology
This project will reframe the estimation of marine primary production around the key step that drives the photochemistry of marine phytoplankton – the absorption of photons.
Variability in the light absorption properties of marine phytoplankton will be examined across ocean biomes using global bio-optical datasets covering a wide range of oceanographic settings, from productive polar seas to oligotrophic gyres. The taxonomic structure and photo-acclimatory status of phytoplankton that together are responsible for changes in the spectral shape and efficiency of phytoplankton absorption will be investigated. The development of photon absorption budgets across a range of ocean provinces will lead to a understanding of the fraction of solar energy that can be channelled into marine photosynthesis and ultimately used to fix carbon. A spectrally resolved model of primary production will be used to obtain an improved representation of light and photosynthesis over a range of marine ecosystems.
The project will improve our global estimates of marine primary production and the retrieval of phytoplankton groups from satellite, both of which are critical to understand the gross synthesis and net storage of organic carbon in the global ocean. The research will also determine the significance of the underwater light environment in driving the global macroecology of marine primary producers.
Training and Skills
The successful applicant will have an aptitude for multidisciplinary research and good quantitative and computing skills. The student will receive guidance in working with large oceanographic datasets. They will acquire a thorough grounding in the modelling of marine primary production. Potential opportunity to participate in a research cruise if this student wishes.
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