Description: The Marine Strategy Framework Directive (MSFD) requires EU Member States to achieve and maintain good environmental status (GES) across their marine waters. WKBENTH3 convened as a hybrid meeting to evaluate benthic assessment methods and indicators for their potential to meet the criteria described under the MSFD Descriptor 6 (seabed integrity). They evaluated a suite of indicator methods, proposed by participants. Those included five indicator methods de-scribing the ‘Condition of the Benthic Habitat’, primarily linked to D6C5, and six indicator meth-ods for ‘Physical Disturbance on Benthic Habitats’, primarily linked to D6C3. Variants of some of the indicators as well as some other commonly used diversity indices were also assessed. A common dataset with broad regional representation was used to compare and contrast indi-cator performance with 17 benthic invertebrate datasets drawn from a range of pressure gradi-ents (14 over gradients of commercial bottom trawling intensity, 2 over gradients of eutrophica-tion and 1 over a pollution gradient). A meta-analysis of the mean response to trawling across all locations showed that most indicators had, on average, declined at the high trawl impact rel-ative to the baseline and a significant effect of trawling was detected for the indicators Commu-nity Biomass, Species Richness, Fraction of long-lived species, Median longevity, Fraction of sen-tinel species - SoS, Relative Margalef diversity index DM’, Shannon Index and Inverse Simpson. The complementarity of the different indices was computed using Spearman correlation coeffi-cients between each of the indices for all gradients, ordering indicators with Ward’s hierarchical clustering. One of the key findings was the identification of four groups of indices that showed clear patterns of association. Considering the link of indicators to different benthic community properties, WKBENTH3 proposed that the assessment of D6 should be carried out selecting a number of indicators drawn from different cluster groups to ensure that components of diver-sity, species sensitivity and abundance (density and/or biomass – or other proxy linked to benthic habitat functioning) are addressed. WKBENTH3 further ranked model-based benthic sensitivity and impact outputs across broad habitat types (BHTs) in eight different subdivisions in order to contrast indicator responses. The ranking showed a broad congruence, however, every subdivision had variation in ranking of BHTs among indicator methods. Further work is needed to determine the cause of those discrep-ancies and to look more closely at the values and the response curves generated. WKBENTH3 developed a worked example of how to estimate thresholds for GES based on the approach of ‘detectable change’. The approach was applied to each of the different pressure gra-dients and to muddy sand habitats. It was not able to estimate thresholds for all gradients da-tasets as the confidence intervals around some relationships were very wide. Experts highlighted that the assessment of seabed integrity needs to ensure that cross-regional, regional, national and local scale assessments can “talk” to each other and that they are complementarity in terms of what aspects of the ecosystem the respective indicators are capturing and what pressure they are tracking (linked to manageable human activity). Cross-regional assessments will inform whether assessments are measuring the same or similar things, allowing for such crosschecking.

Description: ICES

Description: Published

Description: Refereed

Description: Eutrophication is a serious threat to aquatic ecosystems globally with pronounced negative effects in the Baltic and other semi-enclosed estuaries and regional seas, where algal growth associated with excess nutrients causes widespread oxygen free “dead zones” and other threats to sustainability. Decades of policy initiatives to reduce external (land-based and atmospheric) nutrient loads have so far failed to control Baltic Sea eutrophication, which is compounded by significant internal release of legacy phosphorus (P) and biological nitrogen (N) fixation. Farming and harvesting of the native mussel species (Mytilus edulis/trossulus) is a promising internal measure for eutrophication control in the brackish Baltic Sea. Mussels from the more saline outer Baltic had higher N and P content than those from either the inner or central Baltic. Despite their relatively low nutrient content, harvesting farmed mussels from the central Baltic can be a cost-effective complement to land-based measures needed to reach eutrophication status targets and is an important contributor to circularity. Cost effectiveness of nutrient removal is more dependent on farm type than mussel nutrient content, suggesting the need for additional development of farm technology. Furthermore, current regulations are not sufficiently conducive to implementation of internal measures, and may constitute a bottleneck for reaching eutrophication status targets in the Baltic Sea and elsewhere.

Description: Predictive species distribution models are mostly based on statistical dependence between environmental and distributional data and therefore may fail to account for physiological limits and biological interactions that are fundamental when modelling species distributions under future climate conditions. Here, we developed a state-of-the-art method integrating biological theory with survey and experimental data in a way that allows us to explicitly model both physical tolerance limits of species and inherent natural variability in regional conditions and thereby improve the reliability of species distribution predictions under future climate conditions. By using a macroalga-herbivore association (Fucus vesiculosus - Idotea balthica) as a case study, we illustrated how salinity reduction and temperature increase under future climate conditions may significantly reduce the occurrence and biomass of these important coastal species. Moreover, we showed that the reduction of herbivore occurrence is linked to reduction of their host macroalgae. Spatial predictive modelling and experimental biology have been traditionally seen as separate fields but stronger interlinkages between these disciplines can improve species distribution projections under climate change. Experiments enable qualitative prior knowledge to be defined and identify cause-effect relationships, and thereby better foresee alterations in ecosystem structure and functioning under future climate conditions that are not necessarily seen in projections based on non-causal statistical relationships alone.