Marine plankton capable of photosynthesis and predation ("mixoplankton") comprise up to 50% of protist plankton and include many harmful species. However, marine environmental management policies, including the European Union Marine Strategy Framework Directive (MSFD) and the USEPA, assume a strict dichotomy between autotrophic phytoplankton and heterotrophic zooplankton. Mixoplankton often differ significantly from these two categories in their response to environmental pressures and affect the marine environment in ways we are only beginning to understand. While the management policies may conceptually provide scope for incorporating mixoplankton, such action is rarely implemented. We suggest that the effectiveness of monitoring and management programs could benefit from explicit implementations regarding the ecological roles and impact of mixoplankton. Taking the MSFD as an example of marine management guidelines, we propose appropriate methods to explicitly include mixoplankton in monitoring and marine management. Integr Environ Assess Manag 2024;20:1366-1383. © 2024 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

This study focussed on the long-term, sediment-driven changes of macrobenthic assemblages in dredged harbour sediment from Rotterdam harbour disposed of in excavated sand extraction pits off the Dutch coast. Macrobenthic species and sediment grain size composition were studied in samples from two disposal sites and the surrounding environment over ten years after the cessation of disposal activities.There was a strong association between the sediment granulometry and the benthic assemblage composition. Shortly after the last discharge, the top layer of the sediments in the pits contained 20%-60% mud (particles <63 mu m) and was colonised by benthic species typical for these sediments. The pit sediments and benthic assemblages contrasted strongly with the surrounding medium-coarse sediment, extremely low in mud (<0.01%). Over eight to ten years, the top layers of the disposal sites became significantly less muddy (ca. 5%-15% mud), and the benthic assemblages changed over this period from mud-favouring species dominated by annelids to species preferring fine sand with relatively low mud percentages dominated by molluscs. The two different disposal sites converged in sediment composition and benthic assemblages over the ten years of monitoring. The contrast with the medium-coarse sediments with very low mud percentages remained even after this period. The use of sand extraction pits as disposal sites for dredged harbour sediments may be seen as an economically sound beneficial use option in dredged material management, albeit with long-term ecological effects.

Regulatory monitoring of the Dutch part of the southern North Sea does not provide sufficient information to understand the observed changes in the physical, chemical and ecological environment. As a result, the Dutch North Sea policy and management is not appropriately supported by data. The monitoring lacks explicit objectives for integrated management and knowledge enhancement about system functioning. Ecological processes are not included in the programs. There is neither integration of monitoring of physical, chemical and biological parameters, nor is there integration of regulatory monitoring, project monitoring and applied in-depth research. In the meantime, the effects of climate change, the upscaling of renewable energy, and plans for intensifying offshore aquaculture make appropriate monitoring even more urgent. The Dutch North Sea management is therefore faced with the challenge of adapting the current monitoring without compromising continuity. This can be done by making monitoring hypothesis-driven, setting up an integrated monitoring strategy based on regulatory and project-based monitoring, combining structure and process measurements, applying new smart automated techniques, increased use of modelling and remote sensing, and conducting in-depth measurement campaigns. As the North Sea is bordered by several countries, such a renewed effort should be done in coordination with these countries.

Recent papers have suggested that epifaunal organisms use artificial structures as stepping-stones to spread to areas that are too distant to reach in a single generation. With thousands of artificial structures present in the North Sea, we test the hypothesis that these structures are connected by water currents and act as an interconnected reef. Population genetic structure of the blue mussel, Mytilus edulis, was expected to follow a pattern predicted by a particle tracking model (PTM). Correlation between population genetic differentiation, based on microsatellite markers, and particle exchange was tested. Specimens of M. edulis were found at each location, although the PTM indicated that locations >85 km offshore were isolated from coastal subpopulations. The fixation coefficient FST correlated with the number of arrivals in the PTM. However, the number of effective migrants per generation as inferred from coalescent simulations did not show a strong correlation with the arriving particles. Isolation by distance analysis showed no increase in isolation with increasing distance and we did not find clear structure among the populations. The marine stepping-stone effect is obviously important for the distribution of M. edulis in the North Sea and it may influence ecologically comparable species in a similar way. In the absence of artificial shallow hard substrates, M. edulis would be unlikely to survive in offshore North Sea waters.

Jennifer Dannheim *, Lena Bergström, Silvana N. R. Birchenough, Radosław Brzana, Arjen R. Boon, Joop W. P. Coolen , Jean-Claude Dauvin, Ilse De Mesel, Jozefien Derweduwen, Andrew B. Gill, Zoë L. Hutchison, Angus C. Jackson, Urszula Janas, Georg Martin, Aurore Raoux, Jan Reubens, Liis Rostin, Jan Vanaverbeke, Thomas A. Wilding, Dan Wilhelmsson, and Steven Degraer Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Science, Am Handelshafen 12, Bremerhaven 27570, Germany Helmholtz Institute for Functional Marine Biodiversity at the University of Oldenburg (HIFMB), Ammerländer Heerstraße 231, Oldenburg 26129, Germany Department of Aquatic Resources, Swedish University of Agricultural Sciences, Skolgatan 6, Öregrund 74242, Sweden Cefas Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK Institute of Oceanography, University of Gdansk, Al. Marsz. J. Pilsudskiego 46, Gdynia 81-378, Poland Deltares, Unit Marine and Coastal Studies, P.O. Box 177, Delft 2600 MH, The Netherlands Wageningen Marine Research (Formerly IMARES), P.O. Box 57, Den Helder 1780 AB, The Netherlands Aquatic Ecology and Water Quality Management Group, Wageningen University, Droevendaalsesteeg 3a, Wageningen 6708 PD, The Netherlands Normandie Univ, UNICAEN, Laboratoire Morphodynamique Continentale et Côtière, CNRS, UMR 6143 M2C, 24 Rue des Tilleuls, Caen 14000, France Operational Directorate Natural Environment (OD Nature), Marine Ecology and Management (MARECO), Royal Belgian Institute of Natural Sciences, Vautierstraat 29, Brussels B-1000, Belgium Institute for Agricultural and Fisheries Research (ILVO), Ankerstraat 1, Oostende B-8400, Belgium PANGALIA Environmental, Ampthill, Bedfordshire, UK Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA Centre of Applied Zoology, Cornwall College Newquay, Wildflower Lane, Trenance Gardens, Newquay, Cornwall TR7 2LZ, UK Estonian Marine Institute, University of Tartu, Mäealuse 14, Tallinn 12618, Estonia Flanders Marine Institute, Wandelaarkaai 7, Oostende 8400, Belgium Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll PA37 1QA, UK Swedish Secretariat for Environmental Earth System Science (SSEESS), Royal Swedish Academy of Science, Box 50005, Stockholm 104 05, Sweden *Corresponding author: tel: þ 49 471 4831 1734; e-mail: jennifer.dannheim@awi.de.

As the EU's commitment to renewable energy is projected to grow to 20% of energy generation by 2020, the use of marine renewable energy from wind, wave and tidal resources is increasing. This literature review (233 studies) (i) summarizes knowledge on how marine renewable energy devices affect benthic environments, (ii) explains how these effects could alter ecosystem processes that support major ecosystem services and (iii) provides an approach to determine urgent research needs. Conceptual diagrams were set up to structure hypothesized cause-effect relationships (i.e. paths). Paths were scored for (i) temporal and spatial scale of the effect, (ii) benthic sensitivity to these effects, (iii) the effect consistency and iv) scoring confidence, and consecutively ranked. This approach identified prominent knowledge gaps and research needs about (a) hydrodynamic changes possibly resulting in altered primary production with potential consequences for filter feeders, (b) the introduction and range expansion of non-native species (through stepping stone effects) and, (c) noise and vibration effects on benthic organisms. Our results further provide evidence that benthic sensitivity to offshore renewable effects is higher than previously indicated. Knowledge on changes of ecological functioning through cascading effects is limited and requires distinct hypothesis-driven research combined with integrative ecological modelling.

The removal of thousands of structures associated with oil and gas development from the world's oceans is well underway, yet the environmental impacts of this decommissioning practice remain unknown. Similar impacts will be associated with the eventual removal of offshore wind turbines. We conducted a global survey of environmental experts to guide best decommissioning practices in the North Sea, a region with a substantial removal burden. In contrast to current regulations, 94.7% of experts (36 out of 38) agreed that a more flexible case-by-case approach to decommissioning could benefit the North Sea environment. Partial removal options were considered to deliver better environmental outcomes than complete removal for platforms, but both approaches were equally supported for wind turbines. Key considerations identified for decommissioning were biodiversity enhancement, provision of reef habitat, and protection from bottom trawling, all of which are negatively affected by complete removal. We provide recommendations to guide the revision of offshore decommissioning policy, including a temporary suspension of obligatory removal.

Collision of birds with wind turbines is an important negative effect of wind energy generation. Assessments of the potential numbers of bird collisions are required prior to the construction of wind farms. Collision rate models (CRMs) are used as a tool to estimate numbers of collision victims for wind farm initiatives. In the past couple of decades various CRMs have been developed. These models are all based on the theoretical calculation of collision probabilities (theoretical models). In this paper we introduce an empirical model, the Flux Collision Model (FCM), in which actual knowledge of species (group)-specific collision probabilities collected in existing wind farms on land is used to calculate collision rates for planned wind farms. An important quality of the FCM is that it provides a means to use empirical information to assess collision rates in Environmental Impact Assessments (ETAS) for wind farm initiatives. In addition, no detailed information on bird behaviour close to the rotor is needed, as this information is already incorporated in the empirical collision probability. In two case studies, one offshore and one on land, we compare and discuss the use and performance of the empirical FCM and the theoretical SOSS Band model for predicting collision rates of birds at wind farm initiatives. To date, no actual collision rates are known for the offshore situation. Accordingly, in the FCM, collision probabilities derived from wind farms on land were used. Nevertheless, in the offshore case study, the results of the FCM were comparable with those of the SOSS Band model. Basic sensitivity analyses for both the FCM and the SOSS Band model showed that purely theoretically both models are equally sensitive to changes in avoidance rates. However, because lower values for avoidance are applied in the FCM (wind farm avoidance) than in the SOSS Band model (overall avoidance), in practice the effect of realistic variation in avoidance rates on the resulting collision rates is much smaller for the FCM than for the SOSS Band model. Our results show that the FCM provides a valuable addition to the existing suite of (theoretical) CRMs. The predictive value of the theoretical SOSS Band model is constrained by the limited availability of knowledge on species (group)-specific (wind turbine) avoidance rates, which is not the case for the FCM. By contrast, the reliability of the empirical FCM is determined only by variation in the availability and quality of information on species (group)-specific collision probabilities. The choice of which CRM to use (theoretical or empirical) seems not to depend on the location of the wind farm initiative as being offshore or on land, but on the availability and reliability of species (group)-specific information in existing wind farms. The availability of a reliable collision probability supports the use of the FCM, while the availability of information on (overall) avoidance rates in the absence of a species (group) specific collision probability supports the use of a theoretical CRM like the SOSS Band model. Synthesis and applications. The predictive power of collision rate models relies in the first place on the quality of the input information, and second on the theoretical details of the model calculations. Although the FCM is less dependent on measurements of avoidance rates, an urgent need remains to obtain information on actual collision rates and corresponding collision probabilities as well as avoidance rates in existing wind farms both offshore and on land in order to accurately determine the impact of wind energy on bird populations.

A 600 MW offshore wind farm is under construction in the Netherlands Exclusive Economic Zone at a site called Gemini situated 55 km north of the Wadden Sea island of Schiermonnikoog and 85 km from the nearest Dutch port of Eemshaven. This chapter investigates the option of introducing a multi-use design for the Gemini site by adding mussel cultivation (48 kt wet weight per year) and seaweed cultivation (480 kt wet weight per year) to the wind farm. An institutional analysis indicates a political will in the Netherlands to support the development of adding uses to offshore wind farms, but a number of implementation obstacles are also identified. Those obstacles include an absence of licences for multi-use production and legal restrictions against third-party access to wind farms. There is therefore a need for a regulatory framework for multi-use and trust-building among actors involved in multi-use installations. A financial and economic assessment, and a cost-benefit analysis also taking into account monetized changes in CO2 emissions, indicate that adding mussel cultivation to the wind farm is likely to be both financially and socio-economically viable. Including a seaweed cultivation function is probably not financially and socio-economically viable under current technical and economic conditions. Knowledge gaps and uncertainties in these assessments with respect to, for example, missing site-specific data and non-monetized externalities suggest further research, also including pilot cultivations of mussels and seaweed in planned single-use or multi-use installations.

We compared and contrasted 11 European case studies to identify challenges and opportunities toward the operationalization of marine and coastal ecosystem service (MCES) assessments in Europe. This work is the output of a panel convened by the Marine Working Group of the Ecosystem Services Partnership in September 2016. The MCES assessments were used to (1) address multiple policy objectives simultaneously, (2) interpret EU-wide policies to smaller scales and (3) inform local decision-making. Most of the studies did inform decision makers, but only in a few cases, the outputs were applied or informed decision-making. Significant limitations among the 11 assessments were the absence of shared understanding of the ES concept, data and knowledge gaps, difficulties in accounting for marine social–ecological systems complexity and partial stakeholder involvement. The findings of the expert panel call for continuous involvement of MCES ‘end users’, integrated knowledge on marine social–ecological systems, defining thresholds to MCES use and raising awareness to the general public. Such improvements at the intersection of science, policy and practice are essential starting points toward building a stronger science foundation supporting management of European marine ecosystems.EDITED BY Sebastian Villasante

Marine renewable energy developments (MREDs) are rapidly expanding in size and number as society strives to maintain electricity generation whilst simultaneously reducing climate-change linked CO2 emissions. MREDs are part of an ongoing large-scale modification of coastal waters that also includes activities such as commercial fishing, shipping, aggregate extraction, aquaculture, dredging, spoil-dumping and oil and gas exploitation. It is increasingly accepted that developments, of any kind, should only proceed if they are ecologically sustainable and will not reduce current or future delivery of ecosystem services. The benthos underpins crucial marine ecosystem services yet, in relation to MREDs, is currently poorly monitored: current monitoring programmes are extensive and costly yet provide little useful data in relation to ecosystem-scale-related changes, a situation called ‘data-rich, information-poor’ (DRIP). MRED –benthic interactions may cause changes that are of a sufficient scale to change ecosystem services provision, particularly in terms of fisheries and biodiversity and, via trophic linkages, change the distribution of fish, birds and mammals. The production of DRIPy data should be eliminated and the resources used instead to address relevant questions that are logically bounded in time and space. Efforts should target identifying metrics of change that can be linked to ecosystem function or service provision, particularly where those metrics show strongly non-linear effects in relation to the stressor. Future monitoring should also be designed to contribute towards predictive ecosystem models and be sufficiently robust and understandable to facilitate transparent, auditable and timely decision-making.

This chapter provides an introduction to the MERMAID project. MERMAID focused on developing concepts for offshore platforms which can be used for multiple purposes, such as energy and aquaculture production. These concepts were developed with input from experts as well as societal stakeholders. MERMAID consortium comprised of 28 partner institutes, including Universities, Research institutes, Industries and Small and Medium Enterprises from several EU countries. Consortium members brought a range of expertise in hydraulics, wind engineering, aquaculture, renewable energy, marine environment, project management, as well as socioeconomics and governance. Within the scope of MERMAID it has been developed and applied an Integrated Socio-Economic Assessment of the sustainability of Multi-Use Offshore Platforms, using the results from the natural and engineering sciences as inputs, boundaries and constraints to the analysis.

Marine renewable energy projects (MREs) are supported by mandatory environmental monitoring programmes due to assumed environmental impacts. These programmes concentrate on the resultant effects of single industrial projects onto biological and physical components contributing to the local ecosystem structure. To date, impact assessments at the ecosystem functioning level (e.g. trophic interactions, nutrient cycling) are largely lacking. This critical knowledge gap hampers our ability to answering the “so what” question when assessing environmental impacts, i.e. whether the observed impacts are classified as good, bad or neutral, and/or acceptable or unacceptable. When assessing MREs, there is a fundamental need to focus on ecosystem functioning at relevant spatial and temporal scales to properly understand ecological impacts and its consequences. Here, we make a science-based plea for an increased investment in large scale impact assessment of MREs focused on ecosystem functioning. This presentation will cover a selection of examples from MRE monitoring programmes, where the current knowledge has limited conclusions on the “so what” question. Further, applications will demonstrate how a proposed ecosystem functioning approach at an appropriate spatial and temporal scale could advance our current assessment. These examples will illustrate the need to expand the current level of MRE monitoring beyond that of community structure and of individual industrial projects. This work will advance and strengthen collaborative MRE monitoring strategies, facilitating scientists, developers and regulators to answer the much needed “so what” question when undertaking environmental assessments, and reassuring stakeholders with high confidence over these assessments.

Offshore marine renewables energy developments (MREDs), particularly in the light of extensive offshore wind farm development in shallow shelf seas, are expected to affect the structure and functioning of marine ecosystems. Several activities linked to the installation and operation of MREDs each have their differential impacts onto the ecosystem. The benthos plays key roles in the ecosystem, supporting numerous ecosystem goods and services such as long-term carbon storage and food resources for higher trophic groups (e.g. fish, birds, mammals and including humans). Development of MREDs will initiate processes which are expected to affect benthic assemblages over various, currently unknown, spatial and temporal scales. This work provides a structured overview of ecological cause-effect relationships related to MREDs, based on a set of hypothesis-driven pathways supported by literature (>230 publications reviewed). Furthermore, this work evaluated the sensitivity of benthic causeeffect relationships to potential effects of MREDs on different spatial and temporal scales and weighted the assessment by confidence in existing knowledge and the consistency of effects among habitats. The outcomes allowed identification of knowledge gaps about ecological processes, in order to prioritize the ‘known-unknowns’ and highlight priority research areas. Our results suggest that the sensitivity of the benthos to MREDs is much higher than previously indicated, particularly where cascading effects lead to changes in ecological functioning. Filling existing knowledge gaps and understanding ecological processes and patterns occurring at low-trophic levels, including those within the benthos, are essential to maintain ecological integrity key to the ecosystem and to society even under MREDs developments.

Monitoring of the environmental effects of a harbour extension and the compensation measures is a very complex task. The Voordelta area has high natural values, but is also of high economic importance. To implement a monitoring strategy for this area a multidisciplinary consortium has been formed, consisting of a number of institutes and companies. A central data management facility was set up for data storage and management. This chapter illustrates the data management approach using the Voordelta monitoring programme for the years 2004 to 2013. A central data management facility was set up for data storage and management. A repository gives access to raw data files to all team members. From the analysis of the raw data a number of information products have been developed and disseminated to the authorities and the public through Google Earth. It will be shown, that the presence of a strong multidisciplinary team and good collaboration is the key to success in this complex programme. The way the data have been managed supports this process enormously.

a Rijkswaterstaat, Ministry of Infrastructure and the Environment, Zuiderwagenplein 2, 8224 AD Lelystad, The Netherlands b Deltares, P.O. Box 177, 2600 MH Delft, The Netherlands c Gimaris, BioScience Park Leiden, J.H. Oortweg 21, 2333 CH Leiden, The Netherlands d Alterra, Wageningen University & Research Centre, P.O. Box 47, 6700 AAWageningen, The Netherlands e NIOZ, P.O. Box 59, 1790 AB Den Burg, The Netherlands f National Institute for Public Health and the Environment, P.O. Box 1, 3720 BA Bilthoven, The Netherlands

The Benthic Ecosystem Quality Index 2 (BEQI2) is the Dutch multi-metric index (MMI) for assessing the status and trend of benthic invertebrates in transitional and coastal waters for the Water Framework Directive (WFD). It contains the same indicators, i.e. species richness, Shannon index and AMBI, as in the multivariate m-AMBI. The latter MMI has been adopted by several European countries in the context of WFD implementation. In contrast to m-AMBI, the BEQI2 calculation procedure has been strongly simplified and consists of two steps, i.e. the separate indicator values are normalized using their long-term reference values resulting in three Ecological Quality Ratios (EQRs), which are subsequently averaged to give one BEQI2 value. Using this method only small numbers of samples need to be analysed by Dutch benthos laboratories annually, without the necessity to co-analyse a larger historical dataset. BEQI2 EQR values appeared to correlate quantitatively very well with m-AMBI EQR values. In addition, a data pooling procedure has been added to the BEQI2 tool which enables the pooling of small core samples (0.01–0.025m2) into larger standardized data pools of 0.1m2 in order to meet the data requirements of the AMBI indicator and to obtain comparable reference values. Furthermore, the BEQI2 tool automatically and efficiently converts species synonym names into standardized species names. The BEQI2 tool has been applied to all Dutch benthos data monitored by Rijkswaterstaat in the period of 1991–2010 in the transitional and coastal waters and salt lakes and these results are reported here for the first time. Reference values for species richness and Shannon index (99 percentile values) and AMBI reference values (1 percentile values) were estimated for all water body–ecotopes and are discussed. BEQI2 results for all these water bodies are discussed in view of natural and human pressures. The pressure sensitivity of the BEQI2 for sewage and dredging/dumping, via the state variables oxygen and suspended matter respectively, was demonstrated.