ICES release advice on a seafloor assessment process

How should we assess physical disturbance and loss of the seafloor and its habitats?
Published: 5 December 2019

​​​​ICES has today released advice that presents a seafloor assessment process for physical loss and physical disturbance on benthic habitats. This advice relates to the EU's Marine Strategy Framework Directive (MSFD), specifically Descriptor 6 on Seafloor integrity (D6). The aim of D6 is the sustainable management of human activities affecting our seas so that the integrity of the seabed is at a level that ensures the structure and functions of ecosystems are safeguarded and benthic ecosystems, in particular, are not adversely affected. As such, ICES sees Ecosystem-based Management (EBM) as the guiding principle behind the MSFD and the primary way of managing human activities affecting marine ecosystems.

Assessment process

To define and quantify pressures in a way that allows their use in the assessment of adverse effects on seabed habitats, pressures need to be relatable to changes in biological processes, e.g. growth and mortality of populations of benthic invertebrates. Hence, intensity of physical disturbance should reflect mechanisms through which activities affect benthic ecosystems and should be quantified in ways relevant to the subsequent assessment of adverse effects. ICES notes that this consideration is not needed for physical loss because by definition physical loss leads to a complete loss or removal of the natural habitat.

The seafloor pressure assessment process advised by ICES assigns each human activity into one of four subtypes of pressure – abrasion, removal, deposition, and sealing. These physical pressure subtypes were identified by ICES as the only pathways from activities to physical loss or physical disturbance. Physical disturbance can become so pronounced that it results in unsealed loss. All lost habitat is excluded from the assessment of disturbance. The dominant activities associated with each pressure subtype are removal: aggregate extraction; abrasion: fishing with mobile bottom-contacting gears; deposition: disposal of (dredged) material; sealing: physical structures. 

The development of this seafloor assessment process and advice is timely, due to the parallel work of the EU Technical Group on seabed habitats and sea-floor integrity that is currently revising MSFD Article 8 guidance with regard to D6. The assessment process supports these developments and facilitates an overarching regional framework that allows for the benchmarking of national assessments against regional assessments, thereby providing further consistency.


The advice provides pragmatic steps for how data should be compiled and coordinated between countries. The development of agreed definitions is an important factor and allows for consistency throughout the regional seas and provides a way to operationalize the framework.

The advice draws on ICES Data Centre's long record of managing large data sets and adherence to FAIR principles.

Steven Degraer, WKBEDLOSS Chair and Royal Belgian Institute of Natural Sciences, notes that the process was more challenging that first thought, "What could have been considered a piece of cake at the very start of the process, turned out to be a tough scientific challenge. With many ICES scientists involved, we however succeeded in not only defining but also operationalizing an assessment process for physical loss and disturbance. A major step forward in assessing seafloor integrity and hence marine management".

The Working Group on Fisheries Benthic Impact and Trade-offs  (WGFBIT) will take the assessment forward in their ongoing work. Gert van Hoey, WGFBIT Chair and ILVO, states that, “For ICES work on assessing impacts on the benthic ecosystem, this advice on a common understanding and tackling of physical disturbance and loss is very important. The ongoing challenge remains to implement this across all regions with appropriate data and take further steps to refine it."

This work was possible due to the input of a wide range of fisheries and environmental expertise, involving more than 90 experts from 18 countries covering the North East Atlantic, the Baltic Sea, the Black Sea, and the Mediterranean Sea. Detailed records of this input is available from the reports of the three specifically ​ICES convened expert workshops WKBEDPRES1WKBEDPRES2, and WKBEDLOSS and the reports of the ICES Working Group on Spatial Fisheries Data (WGSFD) and the Working Group on the Effects of Extraction of Marine Sediments on the Marine Ecosystem  (WGEXT).   Workshop participants included experts involved in national level implementation of MSFD, Regional Sea Conventions, European Environment Agency, Joint Research Centre, ICES Data Centre, and Data Information Group, as well as drawing on science deliverables from several EU-funded/EU-wide projects.​

Read the full advice: EU request to advice on a seafloor assessment process​ for physical loss (D6C1, D6C4) and physical disturbance (D6C2) on benthic habitats.   

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Top image: Pressure - Translating human activities (e.g. different fishing types) into a common measure of pressure on the seafloor and its seafloor habitats.

Bottom image: Impact - Evaluating seafloor impact and benthic habitats that are at greatest risk from human activities disturbing the seafloor​.

Click on the images to enlarge.

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ICES release advice on a seafloor assessment process

International Council for the Exploration of the Sea (ICES) · Conseil International pour l'Exploration de la Mer (CIEM)
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