Shedding light on ocean photosynthesis

Project Rationale :
The ocean contains millions of single celled plants called phytoplankton that form the base of the marine food web. Collectively they carry out half of all the photosynthesis on Earth. They play an important role for fisheries and in the storage of atmospheric carbon in the deep ocean. However, observing these microscopic organisms in the ocean is challenging. Field observations require ships and time-consuming laboratory techniques. An important avenue for making global-scale observations over long timescales is via satellites. The colour of the ocean surface can be measured from space contains information on phytoplankton concentrations and potentially the dominant species within the community. If effective, this approach could revolutionize our understanding and management of the ocean carbon cycle and fisheries, but there remain many challenges. This PhD project will explore how ocean colour can be used to derive information on phytoplankton on a global scale. The aim is to better understand how phytoplankton species distributions and productivity are controlled by the physical environment and how they relate to the surface ocean colour. The project will also assess whether changes in phytoplankton under a future climate change scenario will be observable from space.

Methodology :
The project will use a new state of the art global ocean system model developed as part of the ‘Darwin Project’ at MIT (http://darwinproject.mit.edu/media-library/). The model simulates a dynamic global ocean containing a diverse phytoplankton community. The model is one of very few that resolve ocean colour similar to that observed by satellites (Dutkiewicz et al. 2015, 2018). It is thus highly novel, allowing the relationship between phytoplankton, ocean photosynthesis and ocean colour to be explored in an entirely new way.
Model output, satellite data and relevant existing field data will be analyzed to explore how and why surface ocean colour varies in different ocean regions and over time. The importance of phytoplankton and species composition for setting the ocean colour will be identified. The model will be used as a ‘virtual world’ to explore existing and new algorithms (Sathyendranath et al. 2014) that aim to derive information on phytoplankton from ocean colour satellite data.
A future climate-change model simulation will be analysed to more deeply explore the interacting processes in the ocean system that lead to the predicted future phytoplankton species distributions and associated ocean colour signal. This will help identify whether predicted changes in ocean phytoplankton and photosynthesis will be observable from space.

Training:
The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at Ocean and Earth Science at the National Oceanography Centre Southampton. Specific training will
include:
Support will be given to analyse the MIT model output, satellite and in-situ data, principally using Matlab. Training will be provided in oceanography, statistics and via other relevant courses offered by the University. The student will join a vibrant research community in Southampton and will be able to visit the collaborators, including at MIT. There will be further opportunities to participate in research cruises and to present research at UK and international conferences. Although relevant training will be provided, some experience in programming (e.g. Matlab, Python, R) would be a definite advantage.