Description: 1.Bivalve habitat restoration is growing in geographic extent and scale globally. While addressing the wide-scale loss of these biogenic habitats is still a key motivation behind restoration efforts, increasingly stakeholders and funders are drawn to shellfish restoration for the many ecosystem services these habitats provide. 2.There is clear evidence for the provision of ecosystem services from species targeted for restoration in the USA, in particular Crassostrea virginica. Ecosystem services remain, however, largely unquantified or even undescribed for the majority of other species targeted for restoration. 3.A structured review of the literature was undertaken and supplemented by expert knowledge, to identify which ecosystem services are documented in the following other bivalve species targeted for restoration: Ostrea edulis, Ostrea angasi, Crassostrea rhizophorae, Perna canaliculus, Modiolus modiolus, Mytilus edulis, Mytilus platensis, Crassostrea gigas, Ostrea denselamellosa, Crassostrea ariakensis, and Crassostrea sikamea. 4.Key knowledge gaps in quantifying ecosystem services and the ecosystem engineering properties of habitat building bivalves contributing to the provision of ecosystem services were identified. Ecosystem services with the potential to be widely applicable across bivalve habitat building species were identified. 5.While there is evidence that many of the ecosystem engineering properties which underpin the provision of ecosystem services are universal, the degree to which services are provided will vary between locations and species. Species-specific, in situ, studies are needed in order to avoid the inappropriate transfer of the ecosystem service delivery between locations, and to further build support and understanding for these emerging targets of restoration.

Description: Oyster reefs are among the most threatened marine habitats globally. In Europe, oyster reefs have been extirpated from most locations within their historical range. Active restoration of the native oyster (Ostrea edulis) in Europe has grown substantially in recent years. In sharing experiences between oyster restoration projects in Europe at the Native Oyster Restoration Alliance conference, NORA2, in Edinburgh in May 2019, it became apparent that a number of similar barriers are experienced. This study identified the top 40 questions, which, if answered, would have the greatest influence on the policy and practice of oyster restoration in Europe. Initially 71 people were consulted across 28 institutions and 11 European countries to generate 194 questions. An established process of one round of pre‐workshop voting followed by a one‐day online workshop and two post‐workshop rounds of voting resulted in the final 40 questions. Questions were broadly grouped into the following 10 themes: baselines, site selection, restoration methods, quantifying benefits, disease management, biosecurity, genetic diversity and population differentiation, policy and management, novel technologies, and current and future threats. We anticipate that this list will provide a starting point for developing collaborative projects across the NORA network, as well as assisting policy makers and funders with identifying key areas that need to be addressed in order to overcome existing barriers to scaling up oyster restoration in Europe.

Description: The European oyster (Ostrea edulis) is under significant threat across its natural distribution range and even functionally extinct in some regions, such as in the German North Sea. Due to its ecological significance in terms of biodiversity and other ecosystem services, the species, and the habitat it provides, are defined as highly endangered by the OSPAR Convention. Restoration measures are gaining momentum in Europe and conclusive recommendations for large‐scale biogenic reef restoration are relevant for example within the Marine Strategy Framework Directive and the Habitats Directive. This study examined whether present‐day environmental conditions of sublittoral offshore waters are ecologically suitable for the return of European oysters. Seed oysters (shell length ~2 mm) were deployed in cages in offshore field experiments in 10–26 m water depth. Survival, growth, and condition were investigated over the course of 2 years. Survival was high, even over winter. Growth was excellent, with oysters reaching a mean length of 55.0 ± 7.2 mm shell length and 19.2 ± 6.1 g wet weight after 2 years. The formation of firmly aggregated oysters was observed and confirms O. edulis as a reef‐building species. The overall condition of oysters in the field was excellent, identified by high condition indices and early reproductive activity. These findings are highly relevant for future restoration measures in the North Sea as they confirm that present‐day environmental conditions and small, hatchery‐produced seed oysters are suitable of supporting sustainable and successful restoration efforts even in sublittoral offshore waters.

Description: Detecting changes of sediment boundaries on the seafloor is important for a better understanding of sediment dynamics and related impacts to benthic habitats. Side-scan sonars (SSS) perform more cost-effectively in shallow waters than other acoustic systems because of their larger swath widths, and the resolution of its images does not change with varying water depth. However, as they are generally towed behind the survey vessel, they tend to have lower positioning accuracy, which makes them unreliable for change detection analyses. In this study, we present a workflow that processes SSS data in a way that makes them fit for change detection analyses. To test the capacity of SSS mosaics for change detection, we used a free software called “Digital Shoreline Analysis System”, which was developed by the United States Geological Survey for ArcGIS version 10.4 onwards. The methods were applied in three areas in the Sylt Outer Reef, German Bight, North Sea. Our results showed that with appropriate processing, SSS mosaics could be used for change detection of sharp sediment boundaries. We found a common trend in the sediment distribution patterns of coarse sediments by monitoring the movement of their boundaries. The boundaries moved in northeast-southwest direction and boundary movements of less than 20 m were typically observed. The methods presented here are semi-automated, repeatable, and replicable, which has potential for wide-scale monitoring of sediment distribution patterns.

Description: We investigate factors influencing European winter (DJFM) air temperatures for the period 1979?2015 with the focus on changes during the recent period of rapid Arctic warming (1998?2015). We employ meteorological reanalyses analysed with a combination of correlation analysis, two pattern clustering techniques, and back-trajectory airmass identification. In all five selected European regions, severe cold winter events lasting at least 4 days are significantly correlated with warm Arctic episodes. Relationships during opposite conditions of warm Europe/cold Arctic are also significant. Correlations have become consistently stronger since 1998. Large-scale pattern analysis reveals that cold spells are associated with the negative phase of the North Atlantic Oscillation (NAO?) and the positive phase of the Scandinavian (SCA+) pattern, which in turn are correlated with the divergence of dry-static energy transport. Warm European extremes are associated with opposite phases of these patterns and the convergence of latent heat transport. Airmass trajectory analysis is consistent with these findings, as airmasses associated with extreme cold events typically originate over continents, while warm events tend to occur with prevailing maritime airmasses. Despite Arctic?wide warming, significant cooling has occurred in northeastern Europe owing to a decrease in adiabatic subsidence heating in airmasses arriving from the southeast, along with increased occurrence of circulation patterns favouring low temperature advection. These dynamic effects dominated over the increased mean temperature of most circulation patterns. Lagged correlation analysis reveals that SCA? and NAO+ are typically preceded by cold Arctic anomalies during the previous 2-3 months, which may aid seasonal forecasting.

Description: The ongoing environmental changes in the Southern Ocean may cause a dramatic decrease in habitat quality. Due to its central position in the food web, Antarctic krill (Euphausia superba) is a key species of the marine Antarctic ecosystem. It is therefore crucial to understand how increasing water temperatures affect important krill life-cycle processes. Here, a long-term (August – March) laboratory acclimation experiment at different temperature scenarios (0.5 ◦C, 1.5 ◦C, 2.5 ◦C, 3.5 ◦C, 5 ◦C, 7 ◦C) was performed and the effects of elevated temperatures on whole animal parameters (O2 consumption, body length, length of the digestive gland) were analyzed. The response of krill oxygen consumption to different experimental temperatures differed between acute/short-term and long-term acclimation. After 8 months, krill oxygen consumption remained unchanged up to temperatures of 3.5 ◦C and was significantly higher at temperatures 〉 3.5 ◦C. Krill acclimated to temperatures ≥ 3.5 ◦C were significantly smaller at the end of the experiment. Limited food intake and/or conversion may have contributed to this effect, especially pronounced after the onset of the reproductive period. In addition, the seasonal growth pattern in males differed from that of females. Together, our findings indicate that warming Southern Ocean waters are likely to increase metabolic rate in krill, possibly altering the amount of energy available for other important life-cycle processes, a finding directly related to future population dynamics and fisheries management.

Description: The Ocean Floor Observation and Bathymetry System (OFOBS) is an underwater survey plat-form, which is designed and developed for research in the Polar Regions by the Alfred Wegener Institute (AWI). The tailored deep tow system brought a new perspective and clarity from Arctic Ocean by its optical and acoustic sensors. During the PS101 expedition at the Karasik seamount, OFOBS provides a novel picture of megafauna’s habitats. In this study, we develop a methodology to convert the imagery dataset to micro-bathymetry in order to provide primary data for object detection and habitat mapping which will provide a better understanding of arctic benthic habitats. The methodology is based on the underwater photogrammetry workflow and two different point cloud classification methods adopted for sponge detec-tion in 3D point clouds, to facilitate habitat mapping with a focus on the central of Kara

Description: 1. The Native Oyster Restoration Alliance (NORA) supports the protection and ecological restoration of the native European oyster, Ostrea edulis, and its habitat across its current and historical biogeographical range. NORA works to overcome barriers to the conservation, restoration, and recovery of the European oyster by providing a platform for the NORA community to collaborate and participate in knowledge exchange. NORA seeks to support responsible restoration practice, in compliance with biosecurity and sustainability. 2. Against this background, the NORA community formulated a series of specific recommendations, the Berlin Oyster Recommendation, to support native oyster restoration by developing and applying best practice with the aim to recover healthy and resilient marine ecosystems. In combination with the Standards for Ecological Restoration (SER) and the Restoration Guidelines for Shellfish Reefs, the Berlin Oyster Recommendation is a relevant tool for successful and sustainable oyster restoration in Europe. 3. The establishment of NORA working groups will support the implementation and further development of the six corresponding recommendations. Current NORA working groups cover site selection, biosecurity, production, and monitoring. The site selection working group will address the identification of suitable sites for oyster restoration to support policy relevant decision making and the conservation, reinforcement, or reintroduction of native oysters. The biosecurity working group will develop biosecurity guidelines for native oyster restoration in Europe. The production working group will assess the potential of standards for seed oyster production and supply in order to enhance production appropriate for restoration purposes. In close collaboration with the Native Oyster Network – UK & Ireland (NON), the monitoring working group will produce a monitoring guidelines handbook to provide metrics and methods that will be suitable across the range of O. edulis projects in Europe for the documentation of restoration success and ecosystem recovery. 4. The Berlin Oyster Recommendation was examined and interpreted by NORA experts in the context of the further development of joint guidelines for the practice of successful and sustainable native oyster restoration.

Description: 1. There is a growing effort throughout Europe to restore populations of native oysters (Ostrea edulis), with the ecological objective of enhancing ecosystem biodiversity and resilience. 2. The introduced parasite, Bonamia ostreae, caused catastrophic mortalities during the 1980s, furthering the decline of this species, and is now present throughout much of the natural range of O. edulis. It is therefore important that restoration attempts avoid further introduction and spread of this parasite, which can cause lethal infections of O. edulis. 3. This article presents a comprehensive overview of the scale and distribution of current infection, transmission pathways, and preventive measure guidelines, focusing on the seas, inlets, and estuaries of north‐west Europe, where most ecological restoration attempts for the native European oyster have occurred so far. 4. This is critical information for restoration project planning in which the risk of Bonamia infection must be taken into account.