Report of the Working Group on Biodiversity Science (WGBIODIV)

The ICES Working Group on Biodiversity Science (WGBIODIV) has held three annual meetings in 2016–2018.WGBIODIV worked on theoretical concepts of diversity indicators along several lines. The quantification of changes in biodiversity is often considered central to the assess-ments of human impacts on marine ecosystems, but this quantification has been proven as an exceptionally difficult task. WGBIODIV developed a generic protocol on how indi-cators need to be underpinned conceptually to provide indicators of biodiversity with meaningful assessment targets. WGBIODIV also analysed the impacts of sampling de-sign on estimates of species diversity. And finally, WGBIODIV developed a trait-based sensitivity indicator for benthic community in response to bottom trawling.The generic protocol on indicator development identified seven steps that should be con-sidered when developing indicators for environmental status assessments. Especially the development of a theoretical indicator framework is crucial, because it helps to develop meaningful assessment benchmarks. At the moment, many status indicators used for environmental status assessments by the regional seas conventions are missing this framework or using a non-quantitative theoretical background, which impairs the defini-tion of quantitative assessment targets.The influence of sampling design on estimates of diversity metrics was analysed in four different case studies: (i) comparing different methods for calculating species accumula-tion curves, (ii) analysing the influence of sampling size on North Sea fish species, (iii) analysing the impact of spatial resolution on plankton indicators and (iv) analysing the relationship between sampling effort and species number in soft bottom benthos. These case studies show that patterns of diversity strongly depend on the sampling scheme, which therefore requires careful consideration to provide the adequate data to feed into assessments.WGBIODIV used traits-based data on benthic invertebrate communities to develop a community physical disturbance indicator. This indicator combines functional character-istics of benthic species, including their sensitivity to physical perturbations (i.e. their response through injury or death) and their recoverability (i.e. the self-sustainability of a population when damaged and/or its recolonization potential following mass mortality). The behaviour and performance of the indicator was examined using two independent case studies from the Dutch EEZ and the Bay of Biscay. Future investigations of WGBIODIV will focus on comparison of the distribution of indicator values between different geographical areas and, for some locations, over time. We will use the indicator to test hypotheses on the relationship between trawl effects and function of benthic communities.