Biological Enhancement of Estuarine Beds through Microbial Activity

In the UK today, one in six of all properties are exposed to some degree of flood risk and on average, the annual damage to properties and their contents from coastal and river flooding amounts to around £1.3 Billion (Defra, 2011). Sea-level rise and severe rainfall events as a result of climate change, may accelerate coastal erosion and the deterioration of coastal flood defences. Hence there is an urgent need for adaptation measures for flooding and erosion protection which is recognised by regulatory authorities.

While the important role of saltmarshes in reducing coastal erosion and providing protection against coastal flooding is well-known (e.g. managed realignment is now a preferred form of coastal protection to more costly hard engineering, e.g. Steart Marshes, UK), the process of bonding between sediment particles and biogenic polymers, known as biostabilisation, is less well appreciated within managed realignment schemes. Biostabilisation is the precursor to saltmarsh establishment/expansion, and is the result of microalgal (principally diatoms) extracellular polymer production. The combination of this binding process together with the hydrodynamics and estuarine morphology controls bed erosion threshold and sediment loadings.

This project will comprise laboratory and field investigations into the enhancement of bed stability by microbial growth, in particular to understand how the presence of microbial exudates and subsequent biostabilisation affects the threshold of motion. The field study site will be the Newport Wetlands which is a mudflat on the western side of the Severn Estuary, where significant intertidal benthic microalgae are present. Current understanding of the threshold of motion has been developed from empirical studies where the bed mobility is considered only in terms of the flow properties and the bed particles. Important objectives include the determination of properties of sediment/microbial aggregates and the impact of spatially heterogeneous biostabilisation on flow processes and subsequent patterns of bed erosion.

The student will benefit from training in three disciplines - experimental fluid mechanics, environmental geotechnics and microbiological experimentation. This will include specialised techniques such for velocity and turbulence characteristation such as Acoustic Doppler velocimetry and Particle Image Velocimetry (PIV), microbial culture and maintenance and interdisciplinary experimental design. This project will involve both laboratory and fieldwork. The student will be a member of two research centres in Engineering and will have opportunities to collaborate with industrial and Policy makers through the Severn Estuary Partnership.

Candidates should hold or expect to gain a first class degree or a good 2.1 and/or an appropriate Master’s level qualification (or their equivalent).

Applicants whose first language is not English will be required to demonstrate proficiency in the English language (IELTS 6.5 or equivalent)