Borkum Reef Ground NCA
Brief description
Measuring some 625 km², the NCA reaches depths of between 18 m and 33 m and is characterised by a large sandbank with interspersed reef-forming boulder fields. To the southeast, the sandbank extends into the Lower Saxony Wadden Sea National Park. To the west, the NCA meets the border with the Netherlands.
This is where the sandbank and reefs combine with the gravel, coarse sand and shell layers to form a species-rich mosaic on the sea floor. Despite the small area it covers, the NCA is home to an astonishing abundance of living organisms. The exceptional species diversity on the seabed provides a rich source of food for fish. These in turn attract a large number of harbour porpoise, harbour seals and grey seals.
The area also has a special function beyond its actual borders: in conjunction with the tidal currents, it serves as an important stepping stone for the spread of species in the southern North Sea.
Pressures and management
The southern part of the Borkum Reef Ground NCA is crossed by the busiest shipping lanes in the North Sea, the Terschelling German Bight traffic separation scheme. This takes up around one-third of the NCA. The impacts from shipping particularly affect harbour porpoise – one of the protected species in the NCA. A detailed study of the impacts of shipping on these marine mammals is currently underway. The results of the study will be used to develop recommendations for action to reduce disturbances and these will subsequently be presented to the federal authorities responsible for shipping.
Rules governing shipping traffic can only be agreed and adopted at international level. Measures to reduce and prevent noise are especially important, for example with regard to vessels passing through the NCA during construction and operation of offshore wind farms located outside the nature conservation area. To be able to implement such measures as quickly as possible, cooperation with the responsible institutions is sought even before binding international arrangements are agreed.
Other important human activities involve recreational fishing and the laying and operation of cables and pipelines that run through the NCA. Recreational fishing is only permitted in the south of the NCA; in the north it is prohibited all year round under the provisions of the legislation establishing the NCA.
Mobile bottom-contact fishing has been prohibited in the entire NCA since March 2023. Set net fishing (using gillnets and entangling nets) is prohibited all year round.
The BfN assists in efforts to reintroduce the European flat oyster into the Borkum Reef Ground NCA. Before its disappearance, the species had a geographical concentration in the German North Sea.
Facts and figures
| Name | Dogger Bank SAC | EU Code | Size |
|---|---|---|---|
| Borkum Reef Ground | SAC | DE 2104-301 | 625 km² |
| Habitats and species | Size or figures (2024) |
|---|---|
| Habitats and species | approx. 521 km² |
| Sandbank | approx. 23 km2 |
| Reefs | approx. 340 km² |
| Species-rich gravel, coarse sand and shell layers; habitat type under section 30 of the Federal Nature Conservation Act (BnatSchG) | 1,056 individuals (95% CI: 427-2,078) in summer |
| Harbour porpoise (Phocoena phocoena) | 500, area used as a feeding habitat |
| Common seal (Phoca vitulina) | Uses area as feeding habitat |
| Grey seal (Halichoerus grypus) | Recorded |
Character
The NCA is characterised by closely interlocking sandbanks and reefs with rich substrate and habitat diversity, resulting in rich species diversity. The species found there include several protected species listed in Annex II of the Habitats Directive.
The nature conservation area is home to the characteristic benthic communities found in coarse sand (Goniadella-Spisula association) and fine sand (Tellina-fabula association). The infauna (the communities living in the seabed) is largely dominated by mussels (molluscs) and bristle worms (polychaetes).
On the reefs, the characteristic epifauna (assemblage) can be found in various succession stages, with sea anemones, dead man’s fingers, sea cypress, ascidians, bryozoans, sponges and various crustaceans.
The closely interlocking sandbanks and reefs ensure a great number of species and individuals. Among the Borkum Reef Ground macrozoobenthos (bottom-living organisms > 1mm) alone, a total of 165 different species have been recorded since 1998 – including numerous Red List species.
These bottom fauna provide a rich source of food for fish, attracting a wide range of flatfish, gobies and other bottom-living fish such as rays and pelagic fish species. The twait shad listed in Annex II of the Habitats Directive has important marine habitats in the NCA, which it uses for foraging and wintering. This applies in particular to the twait shad population, which is concentrated in the outer Ems estuary. Twait shad belong to the anadromous migrating fish species which enter rivers only to spawn. In the sea, the adult fish stay mainly in the water column (pelagial), but swim to the bottom to forage, where they benefit from the myriad small fish and invertebrate organisms in the Borkum Reef Ground NCA.
Harbour porpoise, grey seals and harbour seals are found in the Borkum Reef Ground NCA. They benefit from the rich supply of food in the NCA, which is home to the abundant and species-rich fish fauna.
Harbour porpoise are sighted all year round in the Borkum Reef Ground NCA. Since 2008, monitoring conducted by the BfN has shown a rise in harbour porpoise numbers in spring and summer, along with increased sightings of calves. Similar growth has been observed in the Netherlands, which could indicate a relocation of the harbour porpoise southwards. In late spring and summer, population density reaches a maximum at >1 individual/km2.
For grey seals and harbour seals, the Borkum Reef Ground serves primarily as a feeding habitat and also as a migration corridor – for example for migration between breeding grounds in the Lower Saxony and Netherlands Wadden Sea and Heligoland, as well as more distant feeding grounds such as Dogger Bank.
n the Borkum Reef Ground NCA, the Federal Agency for Nature Conservation (BfN) with the support of scientists from the Alfred Wegener Institute for Polar and Marine Research (AWI) is currently introducing the European flat oyster (Ostrea edulis) back into the North Sea, where it is considered regionally extinct. The focus is not just on the species itself, but also on the important ecological service the European flat oyster performs as a biogenic reef builder. Oyster reefs create three-dimensional structures, filter sea water and are biodiversity hotspots. Following the large-scale prohibition of mobile bottom-contact fishing in the Borkum Reef Ground NCA in 2023, favourable conditions have been created for reintroduction of the oyster species.
