From catchment to sea: Changes in particles characteristics using novel in situ and space technologies

This studentship provides an exceptional opportunity for an applicant to join a team with internationally recognised expertise in (optical) aquatic biogeochemistry and Earth observation. The candidate will primarily be based at Stirling, but will collaborate and spend periods of time working with scientists from the Centre for Ecology and Hydrology (CEH).
Background and tasks: The Earth’s surface waters are a fundamental resource and encompass a broad range of ecosystems that are core to global biogeochemical cycling and food and energy production. River-sea systems comprise river catchments, estuaries, lagoons and near-shore marine environments and are important interfaces between continents and seas. Processes in these systems influence the flux of particulate and dissolved materials from the catchment to the sea. Nevertheless, rivers and seas have been modified progressively over the years with environmental consequences, which are cumulative and pervasive and can lead to extreme impactful events including drought and flood.
Knowledge of particle size distributions and composition in these highly complex systems is crucial for understanding many facets of ecosystem structure, variability and change, such as sediment fluxes, phytoplankton dynamics, that incluence the underwater light climate and biogeochemical cycling in addition to geomorphological change.
Recent developments in sensor technology (in-situ and space-borne) enable a more detailed characterisation of aquatic systems at high temporal frequency and large scales. For example, laser-diffraction based sensors now allow the in-situ determination of particle size and concentration in aquatic systems, while electron microscopy coupled with energy dispersive capabilities can adequately characterise submicron particle populations in the lab. Flow cytometry is able to rapidly characterise and quantify phytoplankton / bacterioplankton communities. In parallel, Earth observation (EO) satellite missions such as ESA Sentinel-2, -3 offer a great opportunity of basin-scale monitoring of water properties over the surface water continuum. In order to enable the use of the abovementioned technologies for characterising suspended particles in river-sea systems, methodologies need to be tested, refined and/or advanced.
The main aim of this PhD is twofold: 1) to understand sediment sources and their conveyance through river-sea systems; and 2) to establish functional relationships between optical properties and sediment characteristics in these systems.
This PhD will focus on two contrasting UK river-sea systems:
1) Tay - North Sea
2) Thames - North Sea
The methodology will mainly include:
• In-situ characterisation of bio-geo-optical properties and sediment size distributions: attenuation, absorption and scattering at 5 different size fractions; spectral backscattering; determination of particle size; Subsurface irradiance reflectance and above water-leaving reflectances; Chlorophyll; coloured dissolved organic material, turbidity.
• Detailed particle characterisation in the laboratory: This will include single particle size and chemical composition determined by a scanning electron microscope equipped with energy dispersive X-ray. Samples will be also analysed for concentration of organic/inorganic suspended material, particle size, phytoplankton cell abundances (Beckmann Flow Cytometer) and specific absorption coefficients.
• Earth observation: Both ESA Sentinel 2 and 3 satellites along with archived Envisat data will be exploited to retrieve information on suspended sediments from these environments. Simulated (Hydrolight) spectra will also be generated to fill gaps in the in situ data record, to contribute to algorithm

The studentship: The student will have access to state-of-the-art instrumentation and facilities and will receive specialist training through IAPETUS2 training package, Stirling Graduate Research School and other targeted courses.