C FLOOR – Exploring the Hidden Carbon Cost of Bottom Trawling in UK Shelf Sea
How an interdisciplinary team is using AI, robotics, and field data to guide marine carbon policy
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Professor Martin Solan (UoS) - Professor of Biodiversity and Ecosystem Function
Professor Susan Gourvenec (UoS) - Deputy Director of Southampton Marine Maritime Institute & Professor of Offshore Geotechnical Engineering
Professor Simon Cox (UoS) - Professor of Computational Methods
Professor Jasmin Godbold (UoS) -Researcher in Seafloor Biodiversity and Ecosystem Functioning
Professor Blair Thornton (UoS) - Researcher in Seafloor Imagery and Robotics
Dr Wassim Dbouk (UoS) - Research fellow involved in a multi-disciplinary project researching the legal and regulatory aspects of CO2 in support of the UKs Carbon Capture Utilisation and Storage plans
Professor Kerry Turner (UEA) - Researcher in environmental and ecological economics
Nadiya Catel-Arutyunova (UoS) - Specialist Policy Officer for the Southampton Marine and Maritime Institute supporting the Policy Associate and deliverables relating to public policy Southampton (PPS)
Isabelle White (UoS) - Policy Associate supporting the delivery of variety of UKRI-funded projects and activities across the University through stakeholder analysis, policy synthesis and other activities
Dr James Strong – marine ecologist with a specialism in habitat and species mapping
Professor Dan Jones – Head of Ocean BioGeosciences Research Group
Dr Anna Lichtschlag – Benthic biogeochemists in the OceanBiogeosciences Group
Dr Sarah Briemann – Ocean biogeochemist with an interest in anthropogenic impacts on the aquatic environment
Dr Vas Kitidis – Ocean biogeochemist with interests in trace gas cycling
Dr Yuri Artioli – Coordinator of PML Science to Impact challenge area “Understanding and mitigating climate change” at PML
Under the Climate Change Act 2008, the UK pledged to achieve net zero carbon emissions by 2050. This pledge has subsequently been embedded in policies such as The Net Zero Strategy (2021), Energy Act (2023), and the Labour government’s A Plan For Change (2024). Complimenting this legal commitment, the UK also has the ambition of protecting at least 30% of its land and sea for biodiversity by 2030 (’30-by-30). However, both targets may be at risk without a more holistic approach towards ocean practices like bottom trawling, especially in the highly dynamic and ecologically rich shelf seas.
Shelf seas are particularly important in this context as they are exceptionally biodiverse areas and account for 81.7% of the area covered by the world’s largest 100 MPAs. Bottom trawling is the most widespread anthropogenic physical disturbance of the seafloor with an estimated release of 1.47 pg/year of DIC from the seafloor – equivalent to 15-20% of annual atmospheric CO2 uptake. It also increases the rate of breakdown of organic matter by increasing oxygen content and therefore has the potential to cause bottom-up ecosystem disruptions, ultimately undermining the ocean’s role as a carbon sink.
Despite the high-risk nature of this environment, its complexity and remoteness make it hard to study. Delineating the individual impact of factors from sediment type and biodiversity, to fishing intensity and gear type, is therefore notoriously difficult. Understanding how these interact with one another is yet another further knowledge gap.
The C-FLOOR project aims to bridge this gap. By decreasing uncertainty surrounding carbon stores, fluxes, and subsequent GHG emissions in shelf seas, the project will provide the scientific evidence needed to support spatial management strategies to reduce the impact of bottom trawling. C-FLOOR will then use the evidence collected and newly acquired knowledge to build a natural capital-based decision support system which will focus on site-specific trade- offs and to help guide UK policymakers in the development of evidence-based legislative and policy frameworks
Four key interdisciplinary research modules are designed to encapsulate the core of C-FLOOR.
1. The Seasonality of Sediment Carbon Release
When bottom trawling disrupts the seabed, it causes a primary loss of carbon through resuspensions and transport of DOC and DIC followed by secondary losses via respiration and decomposition. These both control greenhouse gas and carbon cycling, however, the extent and duration of water the local ecosystem response depends on multiple factors. By sampling scales from nutrient exchange to organism classification the project will work to understand the role of trawling frequency and historic stresses on faunal activity and seabed carbon concentration.
2. Chemistry in The Water Column
Local water chemistry is altered when trawling occurs as the pH, oxygen content, and redox potential is increased. This impacts the carbon accumulation and storage rate. As the project spans, from November 2023 to October 2027, multi-season sampling combined with pre- and post- fishing vessel surveys can be used to understand and separate the effects caused by natural vs anthropogenic events.
3. Seafloor to Atmosphere Pathways
The ocean’s interaction with the atmosphere plays a key role in its function as a carbon sink. Disturbance of the seafloor by bottom trawling may release nutrients into the water column, potentially enhancing primary productivity and temporarily offsetting carbon impacts through photosynthetic CO₂ fixation. However, this process involves a time lag, and the turbulent fishing plumes that drive it are difficult to observe and quantify in the field, leaving their long-term effects poorly understood. C-FLOOR will address this gap by monitoring primary productivity in three dimensions across a trawled area and comparing these data to NEMO-ERSEM model simulations. This will support the development of improved, less impactful fishing gear and enable broader regional application of the findings.
4. Recovery Potential
The previous modules all culminate in this question: can damaged seabeds bounce back and how quickly? In this module C-FLOOR will estimate the capacity for functional recovery of seabed systems and use this information to develop a decision support system for policymakers. This tool will apply a balanced sheet approach to assess the full environmental and societal costs of bottom trawling – emphasizing which parties benefit and which lose at each site. In doing so, the project will confront current challenges around sustainability, scalability, transferability and uncertainty of bottom trawling practices.
C-FLOOR combines state-of-the-art technologies and interdisciplinary expertise to investigate the impact of bottom trawling on carbon storage and greenhouse gas dynamics in shelf sea. This work will be supported through multi-year seasonal fieldwork across UK shelf seas, analysis of historic datasets, autonomous vehicle use, high-resolution seabed imaging, and laboratory experiments. Advances in artificial intelligence (AI) and machine learning (ML) will help process the large datasets produced by long-term and comprehensive observation. Modelling will be used to simulate ecological processes and predict long-term impacts before producing a site-specific decision-making support system.
Bottom trawling – Fishing practice that herds and captures marine life by towing a net along the ocean floor
Shelf Sea – Coastal waters surrounding a continent, typically with a depth less than 200 m
Benthic environment – The lowest ecological zone in a water body
MPA – Marine Protected Areas. These are areas of the ocean established to protect habitats, species and processes essential for healthy, functioning marine ecosystems
Dissolved Organic Carbon (DOC) – Carbon originally associated with living organisms which has been dissolved, in this case in water.
Dissolved Inorganic Carbon (DIC) – Carbon that exists outside of organic compounds (typically found in minerals) which has been dissolved, in this case in water.
As well as furthering system understanding C-FLOOR will provide a natural capital-based decision support system for UK shelf seas which will use confidence bound evidence to understand the environmental and societal impact of bottom trawling. It will quantify the need for impact mitigation and work will industry, regulators and policy makers to ensure this product will support informed decision making with full situational understanding.