Fisheries trawling effects on the structure and functioning of marine sediment microorganisms

The EUs Marine Strategic Framework Directive (MSFD) mandates that member states must establish a programme of measures for achieving good environmental status (GES). A key descriptor of GES is that seafloor integrity is safeguarded to a level that ensures that the structure and functions of the seafloor are not adversely affected.

Fisheries trawling of the seafloor is widely acknowledged as mankinds most widespread physical disturbance in the marine environment. It can alter the physical properties of the benthic [seabed] habitat and impair the resident animals. Very little is known about how trawling affects the structure of the communities of microorganisms that inhabit marine sediments and the time they require to recover from such impacts. These organisms are primarily responsible for driving the rates and pathways of carbon and nitrogen cycling at the seafloor. The few empirical observations of trawl resuspension events suggest that benthic carbon and nutrient effluxes are affected, although comparison between studies yields contradictory results. These inconsistencies confound our ability to effectively manage the environmental impacts of fisheries on the provisioning of ecosystem services such as carbon sequestration and nutrient regeneration.

This project will take a major step towards closing the knowledge gap on the broader impacts of capture fisheries on ecosystem functioning, and how it affects the UK's ability to meet key descriptors of GES. It will investigate how different levels of disturbance intensity affect 1) the physical properties of the seafloor; 2) the structure of the resident microbial communities; 3) their capacity to recycle organic material back to carbon dioxide and dissolved nutrients; 4) the time they require to recover from physical disturbance. The proposed work is underpinned by observations and experiments made across different sediment types at spatial scales that range from the cm to the km. This will enable us to better understand how data derived from small- and medium scale laboratory studies relate to real-world effects. The project involves state-of-the-art stable isotope fingerprinting techniques and pulse-chase experiments.

The supervisory team brings together expertise in marine engineering, fishing gears, geotechnics and biogeochemistry, along with stable isotope techniques and statistical modelling. The CASE Partner, Marine Scotland Science (MSS), provides expert scientific, economic and technical advice on marine fisheries and the aquatic environment to the Scottish Government. They also work closely with the fishing industry in the development of sustainable fisheries, the formulation and development of national governmental policy in relation to the design, operation and deployment of commercial fishing gears and the identification of Marine Protected Areas (MPAs). Working with colleagues at the science-policy interface will ensure that our results directly contribute towards achieving the objectives of the MSFD and other EU directives, including the Water Framework Directive (WFD) and the Common Fisheries Policy (CFP). Our Project Partner, Plymouth Marine Laboratory (PML) is responsible for redeveloping the European Regional Seas Ecosystem Model (ERSEM), which includes benthic processes. Data generated by this studentship will help conceptualise and parameterise ERSEM, increasing national capability to predict the wider biogeochemical effects of trawling.

This multidisciplinary studentship will provide training in field, experimental and laboratory techniques, alongside tuition in generic skills such as problem solving, communication techniques and time management. The successful candidate will be integrated within one of the UK's largest biosciences cohorts of NERC funded students within the Graduate School at the National Oceanography Centre, Southampton (GSNOCS).