ICES was asked to provide scientific advice to support the implementation of the European Union's Marine Strategy Framework Directive (MSFD) Descriptor 6 Criterion 5 (D6C5), which focuses on seafloor quality and the impacts of human activities on marine habitats.
Specifically, ICES was asked to develop and test options for threshold-setting methods to determine when human impacts on the seafloor are considered acceptable or when they indicate ecosystem degradation requiring management action.
ICES was also asked to provide examples of applications across EU marine waters to show the spatial consequences of different threshold and indicator combinations, and to suggest ways to address uncertainty and risk and to combine indicators.
Providing science-based advice on quantitative threshold options now means that the EU's Technical Group on Seabed (TG Seabed) has a solid foundation to develop a harmonized threshold package for adoption across the EU, supporting its mandate in relation to the MSFD.
The resulting advice is the endpoint of a stepwise process of data collation, scientific analyses and knowledge building. This involved collating and analysing data on the state of seabed habitats and the pressures affecting them, a review of threshold-setting methods, and an analysis and interpretation workshop.
This substantial collective achievement was made possible through collaboration and expertise from individuals and teams across Europe and beyond. “Developing and testing so many options for quantitative thresholds for seabed integrity at this scale had not been done before,” says Samuli Korpinen, member of TG Seabed, “but if anyone could attempt it, it was through ICES.”
Indicator choice strongly influences assessment outcomes
To provide the knowledge basis for the advice, ICES Workshop to Evaluate Options for Setting Seafloor Quality Thresholds (WKBENTH4), gathered experts who evaluated six different methods for defining quality threshold values using a range of ecological evidence. To provide options for thresholds, participants had to understand the effect of each human pressure and how it changed the seabed.
“It is such a difficult question to answer", says Maider Plaza, Instituto Español de Oceanografía and participant at WKBENTH4, “To know the effects of trawling frequency, for example, there are so many other variables to control for first: depth, salinity, sediment type and size, etc. Separating one from the other is difficult. And what we have teased out is the effects of the increased human pressures, and when it becomes too much".
The workshop found that assessment outcomes were influenced more strongly by the choice of ecological indicators and the treatment of uncertainty and risk than by the threshold-setting method applied.
Building on previous ICES advice
“Because of previous science and advice, the techniques in this area are quite advanced", says Colm Lordan, Chair of ICES Advisory Committee, “We are happy with the outcome as it provides a wide range of new evidence and options to help TG Seabed establish quality thresholds for D6C5".
Decisions on the values for quality thresholds will ultimately affect how much the seafloor in EU marine waters is considered healthy or degraded by human pressures, and potentially where conservation or restoration measures are needed.
Linking to the Nature Restoration Regulation
As part of this advice request, ICES was also asked to evaluate whether the assessment and threshold-setting methods developed under MSFD D6 can also support implementation of the EU Nature Restoration Regulation.
The advice concludes that they do, and highlights that at least one approach enables estimation of ecological recovery times under specific conditions, providing valuable information for monitoring design and assessment of progress over time.
View and download ICES advice to EU on seafloor integrity thresholds (MSFD D6C5): operational methods and application to the Nature Restoration Regulation from our library.
Read the Workshop to evaluate options for setting seafloor thresholds (WKBENTH4) Report.
