Quantifying kelp detrital pathways: what is potentially locked away as Blue Carbon?

Kelp forests have some of the highest plant production rates globally of between 460 g C m2 yr to 3000 g C m2 yr per unit area [1] and are important for the biodiversity of our coastal systems. It has been estimated that 80% of the biomass produced by kelp systems is exported to shallow- and deep-water systems primarily as detrital material [2]. Yet very little is known of the dynamics of the detrital pathway [3], in particular, the rate of breakdown of the material into decreasing size fractions and the effect of this on particle transport and remineralization rates in situ.

This information is of significance when determining the proportion of the detrital carbon that will be remineralised, releasing CO2 into the coastal waters and what is potentially exported to the sediments to be locked away as blue-carbon.

The aim of this interdisciplinary PhD is to determine the rate of kelp biomass breakdown under varying environmental conditions such as hydrodynamics (waves vs current velocity), temperature, and light using both laboratory and field experimental approaches. Additionally, the biogeochemical dynamics of kelp from senescence and shedding will be elucidated through field-based sampling to determine how these processes affect the production and composition of the dissolved organic carbon and particulate organic carbon pools are broken down further by invertebrates in coastal and shelf seas.

The PhD candidate would be based at Queen's Marine Laboratory (QML) in Portaferry, Northern Ireland where QML's facilities are comprised of indoor and outdoor aquarium facilities with running seawater as well as being close to field locations. The candidate would work closely alongside Dr Louise Kregting (QUB), a phycologist with expertise in productivity and eco-physiology macroalgae merged with biophysical interactions, Prof Jamie Dick (QUB) who will provide expertise on biological breakdown processes by, for example, herbivorous and detritivorous crustaceans, which can contribute immensely to conversion of course to fine particulate organic matter, Prof Ursula Witte (UoA), a biological oceanographer with expertise on experimental methods to elucidate and trace the early diagenesis of carbon fundamental to understanding how kelp-derived organic matter is preserved in marine sediments and Dr William Hunter (AFBI, NI) who's expertise is in marine biogeochemistry, with a specific interest in how environmental changes affects carbon and nutrient cycling.

The research would provide training in a wide range of areas including chemical, physical, and biological processes that govern the detrital pathway.

Full training will be given to the student, however, a background in marine biology, quantitative ecology, data analysis, and water chemistry with an appreciation of coastal fluid dynamics and biophysical interactions will be desirable.