Description: The European flat oyster (Ostrea edulis) is an ecosystem engineer that provides important biogenic reef habitat with associated ecosystem functions and services. Most stocks have been commercially exploited and degraded; some are functionally extinct. Ecological restoration now aims to recover these degraded, damaged or destroyed ecosystems. Availability of seed oysters and substrate for successful larval recruitment has been identified as a major limiting factor for restoration projects in Europe. In substrate‐limited areas, restoration approaches have to involve the restoration of suitable substrates. The present study provides an evaluation of such potential substrate types. Various categories were investigated through hatchery and/or field experiments: (1) marine bivalve shells; (2) inorganic materials; (3) sandy sediment; (4) 3D sandstone reefs; (5) wood materials; and (6) limed materials. The respective settlement rates (settled larvae per cm2) indicate settlement preferences. Hatchery experiments showed significant preferences for bivalve shells and inorganic materials. Best settlement rates were observed on Mytilus edulis shells, followed by O. edulis shells as well as on slaked lime and on baked clay. Settlement was significantly higher on bottom‐oriented areas of bivalve shells and 3D reefs in laboratory experiments; however, this was not substantiated in the field experiments. Field experiments showed significant settlement preferences between substrate categories (bivalve shells, inorganic materials and wood materials). Best settlement rates were observed on baked clay, followed by slaked lime and bivalve shells. Wooden materials did not perform. Settlement rates and substrate preferences of larvae in controlled environments (laboratory, hatchery) differed from rates in the natural environment (field). This study provides a list of substrate types considering these specific environments. The relevance of these results for ecological restoration in the field and potential applications in seed oyster production are discussed.

Description: Oyster reefs are among the most species-rich but at the same time among the most endangered marine habitats in the world. Once, huge areas of three-dimensional biogenic structures formed by the native European oyster (Ostrea edulis) provided a hard substrate on the seabed of the German North Sea, thus providing valuable ecosystem services and habitat for numerous species. Today, O. edulis and its biocoenoses are classified as functionally extinct in the German Bight. The successful and long-term reintroduction of this important ecological key species is currently being investigated and promoted by two projects of the German Federal Agency for Nature Conservation. The return of the European oyster to its former habitat, for which the exclusion of any bottom-contacting human interference is a general prerequisite, could lead to a significant increase in biodiversity. The initial results of the two projects provide an important basis for developing and implementing a large-scale German restoration programme to reinstall a healthy population of the native oyster and its valuable ecosystem services.

Description: The conservation and active restoration of European flat oyster (Ostrea edulis) populations are a major focus of ecological restoration efforts to take advantage of the wide‐ranging ecosystem functions and services this species provides. Accordingly, additional and new demands for seed oysters have arisen. In commercial aquaculture (mariculture), the production of O. edulis is still largely based on natural seed collection. Considering the specific requirements, related to ecological restoration, such as the absence of pathogens and the preservation of high genetic diversity, the current supply is insufficient. Despite the development of breeding and controlled reproduction techniques for this species since the late 1930s, seed production today is mainly based on empirical concepts. Several of the issues that producers still face are already subjects of research; many others are still unanswered or even unaddressed. This review provides a summary of all available knowledge and technologies of O. edulis seed production. Furthermore, it provides a detailed reflection on implications for restoration, future challenges, open questions and it identifies relevant research topics for sustainable seed supply. The study covers the following aspects on (i) biology of the species, (ii) stressors – including pathogens and pollutants, (iii) genetics, (iv) history of production technologies, (v) seed production in polls, (vi) seed production in ponds and (vii) seed production in hatcheries. Future research needs on sex determinism, gametogenesis, cryopreservation, nutrition, selective breeding, pathogens and disease, and the development of reliable protocols for production are highlighted.

Description: Contamination of the oceans with anthropogenic litter is a global environmental problem which currently receives increasing attention by scientists, policy makers, public authorities, media and the general public. Although research efforts have been intensified, they often do not provide stakeholders with easily understandable information about the dimensions and the extent of the problem. We have developed an online portal to provide easily digestible and continuously updated information on marine litter and microplastics to stakeholders based on scientific literature on a global scale. LITTERBASE gives insight about the distribution of marine litter and its effects on marine biota. Data from 1,905 scientific studies (status 26/11/2018) have been compiled into global maps and real-time graphs to make scientific knowledge accessible to the public. Bibliometric data of all publications were entered, as were metadata pertaining to litter type, litter size, litter quantity unit, aquatic system, biome and total litter quantity. Litter quantities were standardised to the most frequently used units to achieve comparability. Data on biological interactions with litter were also extracted: location of field records, number of species affected, percentage of individuals affected, type of interaction, effects on biota, litter type, litter size, aquatic system and biome. Currently, 2,220 species (status 26/11/2018) have been found to interact with marine litter resulting in mortality in almost 12% of the cases reported. Web statistics reveal that the information displayed in the LITTERBASE online portal is continuously being retrieved by users from all over the world.

Description: Bodenschleppnetz-Fischerei und die nicht nachhaltige Entnahme der heimischen Europäischen Auster Ostrea edulis führten dazu, dass die einst weit verbreitete Art in einigen Regionen als in- zwischen ausgestorben gilt. Als ökologische Schlüsselart hat sie jedoch viele positive Effekte für andere Pflanzen und Tierarten und leistet wichtige Ökosystemleistungen für ihre gesamte Umwelt. Nun tüfteln Wissenschaftler*innen daran, wie sich diese biogenen Strukturen, die Aus- tern nach und nach bilden, bestmöglich wieder ansiedeln lassen. Auch die kontinuierliche Nachzüchtung der dafür nötigen Larven ist geplant.

Description: 1. According to the EU Marine Strategy Framework Directive (2008/56/EC), marine protected areas (MPA) should contribute to a good environmental status of the Europeans seas. Measures maintaining or restoring a favourable conservation status of protected species and habitats are mandatory according to the EU Habitats Directive (92/43/EEC). 2. Identification of suitable sites for ecological restoration measures within MPAs is a crucial step towards successful conservation and sustainable MPA management. In terms of species restoration, it is important to restore the respective species with the best possible environment for growth, survival, fitness, and successful recruitment. 3. This study provides a comprehensive list of site-selection criteria for ecological species restoration. Three general categories were chosen: (1) ecological history: evidence for the historical distribution; (2) feasibility of restoration: regulating framework and logistics; and (3) environmental conditions: quality of abiotic and biotic factors. A total of 16 site-selection criteria were identified and applied to biogenic reef restoration, namely for reefs of the native European oyster Ostrea edulis, in the German Bight. 4. The Natura 2000 area Borkum Reef Ground was identified as a suitable site for oyster restoration. It is one of three MPAs in the German Exclusive Economic Zone of the North Sea, which have been declared as Nature Conservation Areas according to national legislation. The conservation objectives include maintenance or, if necessary, restoration of the habitat type ‘reefs’. As a reef-building species, the European oyster O. edulis is of particular importance for this habitat type in terms of nature conservation.

Description: Science communication is becoming increasingly important to connect academia and society, and to counteract fake news among climate change deniers. Online video platforms, such as YouTube, offer great potential for low-threshold communication of scientific knowledge to the general public. In April 2020 a diverse group of researchers from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research launched the YouTube channel "Wissenschaft fürs Wohnzimmer" (translated to "Sitting Room Science") to stream scientific talks about climate change and biodiversity every Thursday evening. Here we report on the numbers and diversity of content, viewers, and presenters from 2 years and 100 episodes of weekly livestreams. Presented topics encompass all areas of polar research, social issues related to climate change, and new technologies to deal with the changing world and climate ahead. We show that constant engagement by a group of co-hosts, and presenters from all topics, career stages, and genders enable a continuous growth of views and subscriptions, i.e. impact. After 783 days the channel gained 30,251 views and 828 subscribers and hosted well-known scientists while enabling especially early career researchers to improve their outreach and media skills. We show that interactive and science-related videos, both live and on-demand, within a pleasant atmosphere, can be produced voluntarily while maintaining high quality. We further discuss challenges and possible improvements for the future. Our experiences may help other researchers to conduct meaningful scientific outreach and to push borders of existing formats with the overall aim of developing a better understanding of climate change and our planet.