Overcoming Ostrea edulis seed production limitations to meet ecosystem restoration demands in the UN decade on restoration

The European flat oyster, Ostrea edulis, is a habitat-forming bivalve which was historically widespread throughout Europe. Following its decline due to overfishing, pollution, sedimentation, invasive species, and disease, O. edulis and its beds are now listed as a threatened and/or declining species and habitat by OSPAR. Increasing recognition of the plight of the oyster, alongside rapidly developing restoration techniques and growing interest in marine restoration, has resulted in a recent and rapid growth in habitat restoration efforts. O. edulis seed supply is currently a major bottleneck in scaling up habitat restoration efforts in Europe. O. edulis has been cultured for centuries, however, research into its culture declined following the introduction of the Pacific oyster, Crassostrea gigas to Europe in the early 1970 s. Recent efforts to renew both hatchery and pond production of O. edulis seed for habitat restoration purposes are hampered by restoration project timelines and funding typically being short, or projects not planning appropriately for the timescales required for investment, research-and-development and delivery of oyster seed by commercial producers. Furthermore, funding for restoration is intermittent, making long-term commitments between producers and restoration practitioners difficult. Long-term, strategic investment in research and production are needed to overcome these bottlenecks and meet current ambitious restoration targets across Europe

Biological site suitability for exposed self-regulating cultivation of blue mussel (Mytilus edulis): A Belgian case study

peer reviewedSeveral reasons, from stakeholder conflicts to water quality issues, are pushing bivalve cultivation to less accessible, exposed, and offshore waters. Because sheltered areas are absent along the Belgian coastline, the possibility to culture mussels with self-regulated systems in exposed conditions has been explored by various research projects. Farmers consider offshore environments unsuitable on the assumption that spat densities are low, and growth is insufficient for commercialization. This study evaluates the potential for self-regulated mussel cultivation in an exposed North Sea environment based on data collected from several research projects that evaluated the biological and technical feasibility of commercial longline cultivation in Belgium. The cultivation methods were variable, but always relied on wild spat that was grown to market size. No husbandry practices such as seed harvesting, thinning, grading, or socking were performed. This cultivation technique, also called self-regulating cultivation, reduces operational costs when extreme weather and exposed conditions limit handling. A 3D hydro-dynamic larvae dispersal model (LDM) was used to simulate the spatial variability in arrivals and the timing of the arrival peak. In addition, a locally validated metabolic model (DEB) for the blue mussel (M. edulis) was forced with 10 year optimized remote sensing observations (Copernicus, Sentinel-3/OLCI) to predict industry-relevant information such as site suitability, inter-annual growth variability, and cultivation time. This study concludes that exposed mussel cultivation near the Belgian east coast is characterised by fast growth. Mussels grown in this area will reach a marketable size (6 cm) after 12–15 months of cultivation, which is just in time for the peak consumption season (July-August). Moving offshore prolongs the cultivation cycles to 17–25 months, but provides more stable growth conditions with less inter-annual variability. When considering a cultivation period of 12 months, the mussels originating from offshore cultivation are comparable in size to the smaller Dutch “Smitse” and French "Bouchots".MultiSyn

Comparing life history traits and tolerance to changing environments of two oyster species (Ostrea edulis and Crassostrea gigas) through Dynamic Energy Budget theory

To predict the response of the European flat oyster (Ostrea edulis) and Pacific cupped oyster (Crassostrea gigas/Magallana gigas) populations to environmental changes, it is key to understand their life history traits. The Dynamic Energy Budget (DEB) theory is a mechanistic framework that enables the quantification of the bioenergetics of development, growth and reproduction from fertilization to death across different life stages. This study estimates the DEB parameters for the European flat oyster, based on a comprehensive dataset, while DEB parameters for the Pacific cupped oyster were extracted from the literature. The DEB parameters for both species were validated using growth rates from laboratory experiments at several constant temperatures and food levels as well as with collected aquaculture data from the Limfjorden, Denmark, and the German Bight. DEB parameters and the Arrhenius temperature parameters were compared to get insight in the life history traits of both species. It is expected that increasing water temperatures due to climate change will be beneficial for both species. Lower assimilation rates and high energy allocation to soma explain O. edulis' slow growth and low reproductive output. Crassostrea gigas' high assimilation rate, low investment in soma and extremely low reserve mobility explains the species' fast growth, high tolerance to starvation and high reproductive output. Hence, the reproductive strategies of both species are considerably different. Flat oysters are especially susceptible to unfavourable environmental conditions during the brooding period, while Pacific oysters' large investment in reproduction make it well adapted to highly diverse environments. Based on the life history traits, aquaculture and restoration of O. edulis should be executed in environments with suitable and stable conditions

Northern Europe’s suitability for offshore European flat oyster (Ostrea edulis) habitat restoration based on population dynamics

Introduction: European and member state legislation encourage the sustainable development of offshore environments, with the restoration or creation of flat oyster (Ostrea edulis) habitats offering potential solutions to enhance biodiversity and provide ecosystem services. The site selection and identification of suitable habitats for flat oyster habitat restoration projects remains a significant knowledge gap. Methods: By combining seabed substrate information with a coupled population (Dynamic Energy Budget - Individual-Based Models) and particle tracking model (for larvae dispersal), critical insights can be gained into the spatial distribution of suitability indicators such as population growth, fitness, reproduction, and self-recruitment. By applying this model to the English Channel and the North Sea over a ten-year period, suitable locations for flat oyster habitat restoration, restorative aquaculture, or oyster-related nature-inclusive designs can be identified. Comparing historical oyster bed locations with model outputs offers insights into why these locations were suitable for oyster bed development and allows for validation of the proposed approach. Results and discussion: Coastal and nearshore environments are generally more suitable for flat oyster habitat restoration, and populations will grow more quickly in these areas. Offshore restoration in the North Sea presents challenges if it relies solely on self-recruitment. Besides site selection purposes, the model can be used to evaluate the effect of management strategies (e.g., initial population size) or environmental pressures (e.g., climate change, pollution) on restorations success

The impact of increased shellfish cultivation in the North Sea on the carbon cycle: A what-if scenario for the European Digital Twin Ocean

For the European Commission, the EDITO consortium is creating the European Digital Twin Ocean, a platform that integrates coastal and oceanic modelling tools with ocean observation databases and computing infrastructure. Building on EMODnet and CMEMS, EDITO Model Lab will contribute by making the next generation of ocean models more accessible.This work demonstrates one of the capabilities of the Digital Twin Ocean, focussing on human exploitation impacts on carbon fluxes. More specifically this what-if scenario is about the impact of upscaling the cultivation of shellfish in the North Sea on the carbon cycle. Upscaling the cultivation of shellfish is part of the envisioned “blue economy” and a promising option for multi-use of offshore wind parks. As shellfish are respiring organisms, they are a carbon source. At the same time shells are a carbon storage as they are built through biocalcification, a process that turns dissolved carbon and calcium into calcium carbonate.The research aims to quantify the effects of upscaling shellfish cultivation in the North Sea on the carbon cycle. This is done by implementing a biocalcification module (Stechele & Lavaud, manuscript submitted for publication in 2024), in the Dynamic Energy Budget (DEB) module integrated in Delft3D-FM’s water quality process library (Troost et al., 2010; Deltares, 2023). Our work includes assumptions about how harvesting accounts for calcium carbonate leaving the sea and is therefore sequestrated.Mathematical Physic

H2020 UNITED : is scour protection suitable for flat oyster restoration in Belgium?

Once a key habitat in the North Sea, European flat oyster (Ostrea edulis) reefs have completely disappeared in the Belgium part of the North Sea (BPNS) due to a combination of factors, including overexploitation, destruction by bottom trawling and diseases such as bonamiosis. Across Europe, a number of projects and initiatives are being deployed to bring back this iconic species and the associated ecosystem, but Belgium is trailing behind this wave of renewed interest in flat oyster restoration. However, with the UNITED project, a first and important initiative has started to restore flat oyster reefs in the BPNS. UNITED (2020-2023) is a research project co-funded by the European Union’s Horizon 2020 programme. The acronym UNITED stands for Multi-Use offshore platforms demoNstrators for boostIng cost-effecTive and Eco-friendly proDuction in sustainable marine activities. By installing specific test pilots at five different marine sites in five European countries, UNITED aims to assess the feasibility and added value of marine multi-use. The Belgian pilot focuses on a combination of flat oyster restoration and aquaculture, and sugar kelp (Saccharina latissima) aquaculture in an offshore wind farm. Belgian offshore wind farms might offer a unique environment for both flat oyster aquaculture and restoration. Bottom-disturbing activities such as trawling are forbidden here, while the scour protection around the wind turbine foundations might serve as a suitable substrate for oyster settlement. Recruitment from the aquaculture individuals can initiate and sustain natural oyster reef development on this scour protection, and as such restore a lost ecosystem in the BPNS. An overview of the oyster restoration activities within UNITED will be presented, including the latest, promising results of the nearshore experiments and the successful offshore (within an offshore wind farm) installation of oyster restoration structures, which house broodstock animals. Before moving offshore, the nearshore experiments have tested and optimised the restoration structures and investigated the settlement of flat oyster spat on different materials as well as the survival, growth and reproduction of flat oysters in aquaculture systems

Site selection for European native oyster ( Ostrea edulis ) habitat restoration projects: An expert‐derived consensus

The European native oyster (Ostrea edulis) is a threatened keystone species which historically created extensive, physically complex, biogenic habitats throughout European seas. Overfishing and direct habitat destruction, subsequently compounded by pollution, invasive species, disease, predation and climate change have resulted in the functional extinction of native oyster habitat across much of its former range. Although oyster reef habitat remains imperilled, active restoration efforts are rapidly gaining momentum. Identifying appropriate sites for habitat restoration is an essential first step in long-term project success. In this study, a three-round Delphi process was conducted to determine the most important factors to consider in site selection for European native oyster habitat restoration projects. Consensus was reached on a total of 65 factors as being important to consider in site selection for European native oyster habitat restoration projects. In addition to the abiotic factors typically included in habitat suitability models, socio-economic and logistical factors were found to be important. Determining the temporal and spatial variability of threats to native oyster habitat restoration and understanding the biotic factors present at a proposed restoration site also influence the potential for project scale-up and longevity. This list guides site selection by identifying: a shortlist of measurable factors which should be considered; the relevant data to collect; topics for discussion in participatory mapping processes; information of interest from the existing body of local ecological knowledge; and factors underpinning supportive and facilitating regulatory framework