Ostrea edulis Beds
Habitat: Ostrea edulis Beds
Description: Beds of the oyster Ostrea edulis occurring at densities of 5 or more per m2 on shallow mostly sheltered sediments (typically 0‐10m depth, but occasionally down to 30m). There may be considerable quantities of dead oyster shell making up a substantial portion of the substratum. The clumps of dead shells and oysters can support large numbers of the ascidians Ascidiella aspersa and Ascidiella scabra. Several conspicuously large polychaetes, such as Chaetopterus variopedatus and terebellids, may be present as well as additional suspension‐feeding polychaetes such as Myxicola infundibulum, Sabella pavonina and Lanice conchilega. A turf of seaweeds such as Plocamium cartilagineum, Nitophyllum punctatum and Spyridia filamentosa may also be present
OSPAR Regions where it occurs: II, III, IV
OSPAR Regions where under threat and/or in decline: II, IV
What is the latest status of the feature? 
The status assessment describes the latest changes in distribution, abundance and range of the feature, as well as any changes in the threats and pressures impacting the feature. The status assessments are updated regularly and inform OSPAR’s consideration of the effectiveness of the measures and actions that have been adopted and implemented by Contracting Parties.
Why is this feature included on the OSPAR List? |  |  |
What protective measures and actions has OSPAR committed to taking? |  |  |
What actions have been implemented by OSPAR? | An implementation report will be published in July 2022 | |
Key message
Compared to the last report from 2009, the status of the European flat oyster is still critical in the OSPAR area, however, there currently is a great restoration effort in all regions to aid remnant populations and reintroduce O. edulis in suitable areas that were formerly populated. Key pressures like fisheries, habitat damage, introduction and further distribution of non-indigenous species or diseases/pathogens still pose a significant threat to oyster beds.
For more information on this habitat please visit the latest status assessment
Threats and impacts
Several factors have determined the decline of wild flat oyster populations down to marginal figures in many European areas: overexploitation of natural beds; introduction of non‐native oysters; adverse effects of climate change and specific epidemic outbreaks (Vera et al. 2019). However, besides these also microplastics are found to impact health and biological functioning of European flat oysters and the associated macrofauna (Green 2016), while alien species could also have negative effects like increased competition, predation or disease transfer. Pressures caused by predators especially Sea Bream, Starfish, Crustaceans, Oyster driller (Pouvreau et al., 2019) pose an additional threat on oyster populations. Habitat destruction and the loss of oyster beds due to bottom fishing are still relevant in some areas. Further, the lack of wild donor populations as well as the lack of suitable substrate hamper the recovery of most oyster populations within the OSPAR area (Pogoda et al. 2019).
For more information on this habitat please visit the latest status assessment
Measures that address key pressures from human activities or conserve the species/habitat
The European flat oyster historically was and still is subject to husbandry and cultivation practices (Colsoul et al. 2020) as well as fisheries target, which needs to be considered when developing management measures to mitigate key pressures.
Successful management therefore includes the regulation and control of fisheries (e.g. seasonal restrictions, quotas, minimum landing size, stock surveys), the limitation of the propagation of non-indigenous species, the diminution of pathogen and parasite transmission as well as measures to introduce suitable substrate and to preserve or restore suitable habitat for reproduction and successful spatfall (OSPAR 2009, Pogoda et al. 2019). Other useful measures could include the allocation of broodstock areas, the establishment of marine protected areas in regions with known severe damage/ loss or the restoration of oysters to promote recovery of the habitat (OSPAR 2009). For all these mitigation measures, a comprehensive, suitable long-term monitoring is indispensable to assess habitat quality and the development of the oyster beds over time (Zu Ermgassen et al., 2020).
For more information on this habitat please visit the latest status assessment
