Description: Within the COST action EMBOS (European Marine Biodiversity Observatory System) the degree and variation of the diversity and densities of soft-bottom communities from the lower intertidal or the shallow subtidal was measured at 28 marine sites along the European coastline (Baltic, Atlantic, Mediterranean) using jointly agreed and harmonized protocols, tools and indicators. The hypothesis tested was that the diversity for all taxonomic groups would decrease with increasing latitude. The EMBOS system delivered accurate and comparable data on the diversity and densities of the soft sediment macrozoobenthic community over a large-scale gradient along the European coastline. In contrast to general biogeographic theory, species diversity showed no linear relationship with latitude, yet a bell-shaped relation was found. The diversity and densities of benthos were mostly positively correlated with environmental factors such as temperature, salinity, mud and organic matter content in sediment, or wave height, and related with location characteristics such as system type (lagoons, estuaries, open coast) or stratum (intertidal, subtidal). For some relationships, a maximum (e.g. temperature from 15–20°C; mud content of sediment around 40%) or bimodal curve (e.g. salinity) was found. In lagoons the densities were twice higher than in other locations, and at open coasts the diversity was much lower than in other locations. We conclude that latitudinal trends and regional differences in diversity and densities are strongly influenced by, i.e. merely the result of, particular sets and ranges of environmental factors and location characteristics specific to certain areas, such as the Baltic, with typical salinity clines (favouring insects) and the Mediterranean, with higher temperatures (favouring crustaceans). Therefore, eventual trends with latitude are primarily indirect and so can be overcome by local variation of environmental factors.

Description: The Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD) are the European umbrella regulations for water systems. It is a challenge for the scientific community to translate the principles of these directives into realistic and accurate approaches. The aim of this paper, conducted by the Benthos Ecology Working Group of ICES, is to describe how the principles have been translated, which were the challenges and best way forward. We have tackled the following principles: the ecosystem-based approach, the development of benthic indicators, the definition of ‘pristine’ or sustainable conditions, the detection of pressures and the development of monitoring programs. We concluded that testing and integrating the different approaches was facilitated during the WFD process, which led to further insights and improvements, which the MSFD can rely upon. Expert involvement in the entire implementation process proved to be of vital importance.

Description: The North Sea Benthos Project 2000 was initiated as a follow-up to the 1986 ICES North Sea Benthos Survey with the major aim to identify changes in the macrofauna species distribution and community structure in the North Sea and their likely causes. The results showed that the large-scale spatial distribution of macrofauna communities in the North Sea hardly changed between 1986 and 2000, with the main divisions at the 50 m and 100 m depth contours. Water temperature and salinity as well as wave exposure, tidal stress and primary production were influential environmental factors on a large (North Sea-wide) spatial scale. The increase in abundance and regional changes in distribution of various species with a southern distribution in the North Sea in 2000 were largely associated with an increase in sea surface temperature, primary production and, thus, food supply. This can be most likely related to the North Sea hydro-climate change in the late 1980s influenced by the variability in the North Atlantic Oscillation (NAO). Only one cold-temperate species decreased in abundance in 2000 at most of the stations. Indications for newly established populations of offshore non-native species were not found.

Description: In 2015, we have collected more than 60,000 scavenging amphipod specimens during two expeditions to the Clarion-Clipperton fracture Zone (CCZ), in the Northeast (NE) Pacific and to the DISturbance and re-COLonisation (DisCOL) Experimental Area (DEA), a simulated mining impact disturbance proxy in the Peru basin, Southeast (SE) Pacific. Here, we compare biodiversity patterns of the larger specimens (〉15mm) within and between these two oceanic basins. Nine scavenging amphipod species are shared between these two areas, thus indicating connectivity. We further provide evidence that disturbance proxies seem to negatively affect scavenging amphipod biodiversity, as illustrated by a reduced alpha biodiversity in the DEA (Simpson Index (D)=0.62), when compared to the CCZ (D=0.73) and particularly of the disturbance site in the DEA and the site geographically closest to it. Community compositions of the two basins differs, as evidenced by a Non-Metric Dimensional Scaling (NMDS) analysis of beta biodiversity. The NMDS also shows a further separation of the disturbance site (D1) from its neighbouring, undisturbed reference areas (D2, D3, D4 and D5) in the DEA. A single species, Abyssorchomene gerulicorbis, dominates the DEA with 60% of all individuals.

Description: Marine benthic ecosystems are difficult to monitor and assess, which is in contrast to modern ecosystem-based management requiring detailed information at all important ecological and anthropogenic impact levels. Ecosystem management needs to ensure a sustainable exploitation of marine resources as well as the protection of sensitive habitats, taking account of potential multiple-use conflicts and impacts over large spatial scales. The urgent need for large-scale spatial data on benthic species and communities resulted in an increasing application of distribution modelling (DM). The use of DM techniques enables to employ full spatial coverage data of environmental variables to predict benthic spatial distribution patterns. Especially, statistical DMs have opened new possibilities for ecosystem management applications, since they are straightforward and the outputs are easy to interpret and communicate. Mechanistic modelling techniques, targeting the fundamental niche of species, and Bayesian belief networks are the most promising to further improve DM performance in the marine realm. There are many actual and potential management applications ofDMsin the marine benthic environment, these are (i) earlywarning systems for species invasion and pest control, (ii) to assess distribution probabilities of species to be protected, (iii) uses in monitoring design and spatial management frameworks (e.g. MPA designations), and (iv) establishing long-term ecosystem management measures (accounting for future climate-driven changes in the ecosystem). It is important to acknowledge also the limitations associated with DM applications in a marine management context as well as considering new areas for futureDMdevelopments. The knowledge of explanatory variables, for example, setting the basis for DM, will continue to be further developed: this includes both the abiotic (natural and anthropogenic) and the more pressing biotic (e.g. species interactions) aspects of the ecosystem.

Description: This review of published and unpublished information demonstrates that offshore wind farms (OWFs) have major effects on the benthos; that is, the seabed flora and fauna. By adding artificial hard substrata to the marine ecosystem, OWFs create new habitat for colonising benthic species, allowing attachment and attraction of hard-substratum species, in ‘the artificial reef effect’. The general exclusion of fisheries further creates flourishing soft-sediment benthic communities. Although wind farms hardly extend the distribution range of hard-substratum species, they may be stepping stones for non-indigenous and nuisance species. Such an increase in benthic diversity, however, is countered by the loss of, disturbance to and/or alteration of the natural seabed. Despite this, it may be concluded that OWFs create local hotspots of benthic diversity, directly influencing the local marine food web. During construction, the biomass of forage species decreases, affecting predatory and scavenging species negatively and positively, respectively. Mobile predatory species tend to leave the area during construction. Once installed, the flourishing benthic communities greatly increase in benthic foraging species and attract predators. The surrounding natural sediments are affected by the deposition of organic matter from the epibionts on the turbine monopoles and scour protection and by the altered predator community. Given that a new ecological equilibrium in the benthic system will develop over 20–30 years, it is arguable whether a return to the pre-construction state following full decommissioning would be feasible or desirable. In contrast, a ‘renewables-to-reefs’ decommissioning scheme involving only partial removal of the wind farm could ensure protection for ecologically valuable sites. While many data already exist, it is difficult to detect significant effects because these are proportional to the degree of change and the changes may take place at different spatial scales. This should be taken into account in OWF monitoring. Benthic communities are of significant ecological and socio-economic importance at a global level. This includes acting as habitat for numerous species at all life-cycle stages, and as a feeding ground for a range of predators. From a socio-economic perspective, these predators can include species of commercial importance. Benthic communities operate both directly and indirectly as food resources for such species. Therefore, the study of the benthic environment around any activity in the marine environment, including offshore renewable energy, is vital to identify potential effects and their significance. All human activities in the marine environment have the potential, by their very nature, to affect its natural structure and functioning. Because of both the direct effects on the seabed and the intimate links between the water column and benthos (Gray & Elliott 2009), the seabed will always be directly or indirectly affected. The effects of offshore wind farms (OWFs) on seabed communities comprise one of the most important elements when considering the potential impacts of such developments, due to the inevitability of effects arising, especially from monopiles bored into the substratum or gravity supported on the seabed, their surrounding erosion protection layer and the installation of cable routes (Wilson et al. 2010). Even developments in floating wind technology still require anchor points and the connection of associated infrastructure, such as inter-array and export cables (e.g. Butterfield et al. 2005; Statoil ASA 2017; see Chapter 1 in this volume). Therefore, an understanding of the ways in which seabed communities are affected by OWFs is vital, in part, so that appropriate mitigation measures can be identified and deployed. A set of key hypotheses have been generated for this chapter: •Changes in seabed ecology as a result of installing a wind farm in the marine environment are viewed as neither positive or negative in ecological terms. but just different. • The inherent variability of the seabed biota and hydrodynamic conditions may prevent the subtle effects of OWFs being detected, in particular in current wind-farm locations around the North Sea. • Hard structures associated with OWFs are available as colonisation sites and ‘stepping stones’ for non-indigenous species. • A focus on the structure of the benthos rather than its ecological functioning does not satisfactorily assess impact. • The effect of a wind-farm structure on the seabed is mirrored by an effect of the seabed and its biota on the structure. • Given the many human activities and pressures, there are in-combination synergistic and antagonistic effects of all aspects of the same development, and cumulative effects of different developments in the same area, which need to be disentangled. • Location provides opportunities (for habitat creation) as well as threats (to the local biota and habitats), and both need to be considered together. • Climate change will increase the variability of an already highly variable system, making it increasingly difficult to detect the effects of the wind farm and its structures.

Description: Benthic habitat condition assessments are a requirement under various environmental directives. The Marine Strategy Framework Directive (MSFD),for example, challenges member states in a European sea region to perform comparable assessments of good environmental status and improve coherence of their monitoring programmes by 2020. Currently, North Sea countries operate independent monitoring programmes using nationally defined assessment areas. Lack of an agreed OSPAR or EU scale monitoring method and programme has been identified as a priority science need. This paper proposes a method for the development of a coherent and efficient spatial sampling design for benthic habitats on regional level and gives advice on optimal monitoring effort to get more accurate assessments. We use ecologically relevant assessment areas (strata) across national borders and test spatial sample allocation methods.

Description: The sustainable development of the marine environment has resulted in the introduction of man-made structures (MMS) in the North Sea. These structures range from oil and gas platforms, buoys, wrecks to wind turbines, offering additional artificial habitat over predominantly soft-sediment areas. The expected effects from MMS in shallow shelf seas will modify benthic communities over various spatial and temporal scales with repercussions for overall ecosystem functioning. Research on large offshore structures have identified a suite of unique effects ranging from biodiversity changes with repercussions on local ecosystem functioning to the provision of habitat for fouling communities, acting as stepping stones and many other ecological modifications. Consequently, MMS might induce structural, functional and process-driven changes, which are different from those expected in natural soft bottom benthic systems. This study considers soft-sediment and introduced hard-substrate epifouling communities. The combination of these systems provides a unique ecological opportunity to ascertain biodiversity changes triggered by loss and gain of species provided by the addition of MMS. To date, our current understanding of how ecological functioning might be modified by the addition of these MMSs is still in its infancy. Our current analysis aimed at evaluating functional changes with a combination of biological traits analysis and energy flow changes calculated via modelled secondary production. Further, our study compared the different types of introduced MMS among the natural soft sediment communities, disentangling how the ecological functioning of the macrobenthos may be altered by the introduction of these structures, which provides improved concepts for current monitoring assessments.