Shedding light on particles in the ocean

Sinking particles in the ocean play a fundamental role in the distribution of many elements in the ocean, in particular for carbon. Plankton in the surface ocean convert CO2 into particulate matter. Some of these particles sink, transporting large quantities of carbon to depth and fueling the deep-sea food web. This “biological carbon pump” plays an important role in the global carbon cycle and thus in controlling our climate.

Traditionally, the flux of sinking particles has been measured using sediment traps. However, these have limited spatial and temporal resolution, leaving many questions about the functioning of the biological carbon pump unanswered. The rapid development of camera technologies now allows the collection of large data sets on particle size and characteristics at high spatial and temporal scales. These optical systems can be deployed remotely on e.g. gliders and moorings, promising great use in future research. However, whilst technologies to image particles have advanced greatly during the last two decades, techniques to analyze the large collected data sets have not. To make things even more complicated, different devices often measure different optical properties and use different specifications, leading to problems in comparing results. What is urgently needed are efficient routines to analyze and characterize particles from imaging devices

You will develop routines to characterize particles from several imaging devices that are currently in use. This will involve intercalibration of these devices in the lab as well in the field using simultaneous deployments. Data from simultaneous deployments are already available, and more will be collected during the COMICS and CUSTARD programmes. You will also have the opportunity to participate in research cruises and collect such data yourself. We will encourage you to engage with the SCOR working group ‘TOMCAT’ (Translation of Optical Measurements into particle Content, Aggregation & Transfer) to collaborate with international partners, which will allow you to extend your work to include additional particle imaging devices.

When developing the particle characterization routines, you will consider the user-interface, particularly the use of analysis routines for non-experts and the output format of the results. Finally, if time allows, the immense data set you have collated will be used to explore various aspects of the biological carbon pump. This may involve looking at the relation between abundance of zooplankton and particles, or calculating variations in particle fluxes on high spatial and temporal scales. Your work will greatly advance our understanding of the biological carbon pump from both a technical and ecological perspective.

The NEXUSS CDT provides state-of-the-art, highly experiential training in the application and development of cutting-edge Smart and Autonomous Observing Systems for the environmental sciences, alongside comprehensive personal and professional development. There will be extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial / government / policy partners. The student will be registered at the University of Southampton, and hosted at the National Oceanography Centre. Specific training will include:

- familiarization of state-of-the-art imaging techniques and devices

- calibration and intercalibration of optical imaging devices in the lab and in the field

- deployment of imaging devices at sea and the health and safety aspects associated with it

- automated image processing

- simple statistics

- data presentation at international meetings; networking and collaboration with international partners

- biogeochemistry of the biological carbon pump