In the first instance the student will quantify the effects of physical disturbance, in terms of initial change and recovery to pre-disturbance conditions, on different benthic biological groups (macrofauna, meiofauna, microbes) and biogeochemical properties (e.g. oxygen content) and processes (e.g. denitrification), using existing scientific literature and empirical datasets. Relevant studies from peer-reviewed and grey literature will be identified following standard systematic review methodology  and synthesized using quantitative methods such as meta-analysis . The scope of the review will be global and will focus on anthropogenic activities that disturb the seafloor through direct physical contact (e.g. abrasion, ploughing, extraction), and include activities such as boat anchoring, fishing using bottom towed gear, marine aggregate extraction, hydraulic and suction dredging used in some deep sea mining practices. In addition to generating estimates of depletion and recovery for different biological groups and ecosystem functions following different types of bottom disturbance, this review will identify key evidence gaps that are not well-studied and limit our understanding of the effects of anthropogenic activities on benthic ecosystem functioning.
The second part of the PhD will examine how changes in the biological and physico-chemical characteristics of the sediment following physical disturbance effect organic matter remineralization. The student will conduct ‘physical disturbance simulation experiments’ in the lab using undisturbed sediment collected from the field (intertidal) and the advanced benthic flux chambers available at the Lyell Centre, to examine the effect of different disturbance frequencies and intensities. Changes between the pre- and post-disturbance macro-, meiofaunal and microbial (bacteria & archaea) assemblages will be measured in terms of biomass, density, community composition and mortality using standard benthic ecology and molecular analytical procedures at Heriot-Watt University (HWU) and University of Glasgow (UoG), respectively. Changes to ecosystem functioning responses such as oxygen consumption dynamics and organic matter processing will be measured using stable isotope tracer techniques (isotopically enriched 13C algae) at HWU, to trace carbon throughout the benthic assemblage and quantify the change of fresh organic carbon processing following disturbance .
CEFAS will provide existing spatio-temporal datasets of macrofauna and biogeochemical data (e.g. oxygen penetration depth, apparent redox potential discontinuity depth, nutrients, organic carbon) across different gradients of physical disturbance in the UK. These datasets will be included in the meta-analysis of empirical data on the effects of physical disturbance on benthic ecosystem functioning.
Bangor University (BU): Models co-developed by Dr Sciberras (HWU) and Prof Hiddink (BU) to quantify initial macrofauna depletion (% loss of biomass), recovery rate and time to pre-disturbance levels following bottom trawling disturbance will be used to quantify impact of different physical disturbance activities on meiofauna and microbes. Training support will be available to the research student by Prof Hiddink.