European flat oysters on offshore wind farms: additional locations : opportunities for the development of European flat oyster (Ostrea edulis) populations on planned wind farms and additional locations in the Dutch section of the North Sea

To determine the relative suitability for development of self-sustaining European flat oyster (Ostrea edulis) beds, potential areas for offshore wind farms in the Dutch Exclusive Economic Zone (EEZ) were analysed following Smaal et al (2017). The studied locations are the new wind farm zones “Hollandse Kust (“noordwest”, “west” and “zuidwest”)”, “IJmuiden Ver” and the remaining lot of the North of the Frysian Islands Wind Farm Zone, but also 13 additional potential locations on the EEZ (i.e. CP4-CP6 and CP9-17) and, in addition, the nature area location Borkum Reef Ground (Borkumse Stenen). This research is performed within EZ-program Beleidsondersteunend Onderzoek (BO).Biotic and abiotic factors of importance for flat oyster survival, growth, reproduction and recruitment, were compared for the 8 wind farm locations of Smaal et al. (2017) and the 18 new locations. For the locations on the Dutch EEZ the following habitat factors are important for flat oyster beds: shear stress, suspended sediment, larval retention, temperature, sediment composition and food availability. Presence in historic distribution area was used as a verification. Average shear stress, suspended sediment and temperature are within the range considered suitable for the development of an oyster bed at all locations. Thus, these factors do not discriminate between locations. Maximum shear stress is too high at one location and the sediment is too silty at 7 locations. However, habitat restoration efforts may make the environment more suitable, e.g. by placing shell material or 3D structures which elevate the oysters from the bottom.Based on the analysis described in this report we recommend to select the following locations that are suitable for flat oyster restoration.1. Best: Borssele Wind Farm Zone, Buitengaats (part of the Gemini wind park) and CP9 (within historic distribution and high larval retention);2. Very good: Hollandse Kust (zuidwest) Wind Farm Zone (high larval retention);3. Good: Offshore Windpark Egmond aan Zee, Prinses Amalia Windpark, Windpark Eneco Luchterduinen, Hollandse Kust (zuid) Wind Farm Zone, Hollandse Kust (noord) Wind Farm Zone (medium larval retention);4. Suitable: the remaining lot of the North of the Frysian Islands Wind Farm Zone, Zee-energie (part of the Gemini wind park), Borkum Reef Ground (Borkumse Stenen) (within historic distribution, medium or high larval retention, but locally too high maximum shear stress or too silty);5. Suitable with introduction of substrate: CP5, CP6 (medium or high larval retention, but too silty without introduction of substrate)

The Native Oyster Restoration Alliance (NORA) and the Berlin Oyster Recommendation: bringing back a key ecosystem engineer by developing and supporting best practice in Europe

Efforts to restore the native oyster Ostrea edulis and its associated habitats are gaining momentum across Europe. Several projects are currently running or being planned. To maximize the success of these, it is crucial to draw on existing knowledge and experience in order to design, plan and implement restoration activities in a sustainable and constructive approach. For the development of best practice recommendations and to promote multidimensional knowledge and technology exchange, the Native Oyster Restoration Alliance (NORA) was formed by partners from science, technology, nature conservation, consultancies, commercial producers and policy-makers. The NORA network will enhance scientific and practical progress in flat oyster restoration, such as in project planning and permitting, seed oyster production, disease management and monitoring. It also focuses on joint funding opportunities and the potential development of national and international regulatory frameworks. The main motivation behind NORA is to facilitate the restoration of native oyster habitat within its historic biogeographic range in the North Sea and other European seas along with the associated ecosystem services; services such as enhancing biodiversity, including enhanced fish stocks, nutrient cycling and sediment stabilization. NORA members agreed on a set of joint recommendations and strongly advise that any restoration measure should respect and apply these recommendations: The Berlin Oyster Recommendation is presented here. It will help guide the development of the field by developing and applying best practice accordingly. NORA also aims to combine the outreach activities of local projects for improved community support and awareness and to provide educational material to increase knowledge of the key ecological role of this species and increase awareness among regulators, permit providers and stakeholders. A synthesis of O. edulis restoration efforts in Europe is provided and underlines the general significance in the field

A single genomic region involving a putative chromosome rearrangement in flat oyster (Ostrea edulis) is associated with differential host resilience to the parasite Bonamia ostreae

European flat oyster (Ostrea edulis) is an ecologically and economically important marine bivalve, that has been severely affected by the intracellular parasite Bonamia ostreae. In this study, a flat oyster SNP array (~14,000 SNPs) was used to validate previously reported outlier loci for divergent selection associated with B. ostreae exposure in the Northeast Atlantic Area. A total of 134 wild and hatchery individuals from the North Sea, collected in naïve (NV) and long-term affected (LTA) areas, were analysed. Genetic diversity and differentiation were related to the sampling origin (wild vs. hatchery) when using neutral markers, and to bonamiosis status (NV vs. LTA) when using outlier loci for divergent selection. Two genetic clusters appeared intermingled in all sampling locations when using outlier loci, and their frequency was associated with their bonamiosis status. When both clusters were compared, outlier data sets showed high genetic divergence (FST > 0.25) unlike neutral loci (FST not ≠ 0). Moreover, the cluster associated with LTA samples showed much higher genetic diversity and significant heterozygote excess with outlier loci, but not with neutral data. Most outliers mapped on chromosome 8 (OE-C8) of the flat oyster genome, supporting a main genomic region underlying resilience to bonamiosis. Furthermore, differentially expressed genes previously reported between NV and LTA strains showed higher mapping density on OE-C8. A range of relevant immune functions were specifically enriched among genes annotated on OE-C8, providing hypotheses for resilience mechanisms to an intracellular parasite. The results suggest that marker-assisted selection could be applied to breed resilient strains of O. edulis to bonamiosis, if lower parasite load and/or higher viability of the LTA genetic cluster following B. ostreae infection is demonstratedBiotechnology and Biological Sciences Research Council. Grant Numbers: BBS/E/D/20002172, BB/S004181/1. Ministry of Agriculture, Nature and Food safety. Grant Numbers: BO43-18, KB33-004S

A single genomic region involving a putative chromosome rearrangement in flat oyster (Ostrea edulis) is associated with differential host resilience to the parasite Bonamia ostreae

European flat oyster (Ostrea edulis) is an ecologically and economically important marine bivalve, that has been severely affected by the intracellular parasite Bonamia ostreae. In this study, a flat oyster SNP array (~14,000 SNPs) was used to validate previously reported outlier loci for divergent selection associated with B. ostreae exposure in the Northeast Atlantic Area. A total of 134 wild and hatchery individuals from the North Sea, collected in naïve (NV) and long-term affected (LTA) areas, were analysed. Genetic diversity and differentiation were related to the sampling origin (wild vs. hatchery) when using neutral markers, and to bonamiosis status (NV vs. LTA) when using outlier loci for divergent selection. Two genetic clusters appeared intermingled in all sampling locations when using outlier loci, and their frequency was associated with their bonamiosis status. When both clusters were compared, outlier data sets showed high genetic divergence (FST > 0.25) unlike neutral loci (FST not ≠ 0). Moreover, the cluster associated with LTA samples showed much higher genetic diversity and significant heterozygote excess with outlier loci, but not with neutral data. Most outliers mapped on chromosome 8 (OE-C8) of the flat oyster genome, supporting a main genomic region underlying resilience to bonamiosis. Furthermore, differentially expressed genes previously reported between NV and LTA strains showed higher mapping density on OE-C8. A range of relevant immune functions were specifically enriched among genes annotated on OE-C8, providing hypotheses for resilience mechanisms to an intracellular parasite. The results suggest that marker-assisted selection could be applied to breed resilient strains of O. edulis to bonamiosis, if lower parasite load and/or higher viability of the LTA genetic cluster following B. ostreae infection is demonstratedBiotechnology and Biological Sciences Research Council. Grant Numbers: BBS/E/D/20002172, BB/S004181/1. Ministry of Agriculture, Nature and Food safety. Grant Numbers: BO43-18, KB33-004S