Species-rich, vibrantly coloured reefs extend in the form of ribbon-like boulder fields along the sides of the Elbe glacial valley. Boulders and stone fields penetrate the sandy areas, including in the central area of the Amrum Bank. Epifauna associations of hard substrates are characteristic, with species such as sea anemone (Metridium dianthus), common sea urchin (Echinus esculentes), dead man’s fingers (Alcyonium digitatum), ascidians (Ascidaea), hornwrack (Flustra folicea) and sponges (Haliclona spp.).

No biogenic reefs have been recorded to date. However, according to historical sources, the European flat oyster (Ostrea edulis) was once widely distributed in the area.

In addition to the reefs, the sandbank off the coast of Amrum (Amrum Bank) is characterised by the occurrence of coarse sand and gravelly areas in an environment usually characterised by medium to find sands. As a result, various typical bottom-dwelling communities have developed in a comparatively small area, namely the coarse sand associations (Goniadella-Spisula association), the Tellina-fabula association with the bean-like tellin as its name-giving species and associations of long-lived mussel species.

The inflow of water from the Elbe to the south and mixing with the tidal current from the North-East Atlantic give rise to fluctuating salinity levels, swirls and thus fronts and upwelling. This creates particularly food-rich zones, for example with a high proportion of plankton and consequently numerous fish.

Due to the prevailing habitat types, the fish include species typical of sandbanks (such as many flatfish species), reef dwellers such as cod (Gadus morhua) and ‘open water’ species – pelagic species such as sprat (Spratus spratus) and herring (Clupea harengus).

As Habitat Directive Annex II species, twait shad (Alosa fallax) and river lamprey (Lampetra fluviatilis) are protected in the area, which provides them with important marine habitats for foraging and overwintering. These rare species belong to the anadromous migrating fish which live in the sea as adults and enter rivers only to spawn. After a period of time, the juvenile fish migrate to the sea.

The many different fish serve marine mammals and seabirds as a source of food. The protected area is of particular importance for harbour porpoise. The highest concentrations of harbour porpoise have been recorded in the German North Sea and the area plays a central role in the conservation of the species. Regular sightings of mother-calf pairs and concentrations of up to 50 individuals within an observation period of 10 minutes (known as ‘hotspots’) confirm that the area is of key importance in the mating, birth and rearing of harbour porpoise. The Sylt Outer Reef directly borders the harbour porpoise conservation area in coastal waters west of Sylt. This is so far the only cetacean conservation area in the North Sea. The high harbour porpoise densities allow inferences as to the favourable supply of potential prey or forage fish. However, populations of harbour porpoise have declined in recent years, possibly as a result of increasing underwater noise caused by the construction of offshore wind farms.

Harbour seals and grey seals use the area as an important feeding habitat and cross it on the way from their permanent feeding grounds to their resting and breeding places. Grey seals currently use the Knobsände off Sylt and Amrum, the Kachelotplate sandbank west of Juist and the largest German colony on the Heligoland dune as breeding grounds. Strong seasonal fluctuations in population suggest a large amount of movement between these locations and other resting sites and colonies around the North Sea, for example on the British coast. The NCA thus performs an important stepping stone function, making the protection of suitable migration corridors extremely important.
 

Many seabirds use the Sylt Outer Reef/Eastern German Bight to forage for food, wintering, moulting, passage and rest.

It is the most important wintering area for red-throated and black-throated divers in the offshore German North Sea. They mostly feed on small schooling fish to build fat reserves for their migration to the breeding areas in the north. Loons and divers are also at risk from the increasingly intensive use of the German marine areas for fishing, offshore wind farms and shipping. Observations show that migrating red-throated and black-throated divers often fly close to the sea surface and only rarely fly higher than 50 metres. This puts them at risk of colliding with engineering structures such as offshore wind farms. Divers are highly sensitive to disturbance and flee from approaching ships, even at a great distance. The Eastern German Bight SPA is of outstanding importance for safeguarding necessary resting and feeding grounds for disturbance-sensitive red-throated and black-throated divers. Vast numbers of common scoter – as many as 45,000 – also winter here.

True seabirds such as black-legged kittiwake, common guillemot, razorbill, northern fulmar and northern gannet, all of which breed in Germany only on Heligoland, use the area for hunting. A number of other protected species, such as predatory seabirds (great skua, Artic skua and pomarine skua), also frequent the area to forage for food. The lesser black-backed gull (Larus fuscus) uses the SPA to forage for food all year round.

The boundary of the SPA mainly follows the distribution hotspots of overwintering red-throated and black-throated divers (Gavia stellata und Gavia arctica) and the distribution of Sandwich terns, common terns and Artic terns (Sterna sandvicensis, Sterna hirundo und Sterna paradisaea), little gulls and common gulls (Hydrocoloeus minutus and Larus canus) that mainly use the area in winter. These species are specially protected as Birds Directive Annex II species.

Protection of the seabirds in the Sylt Outer Reef/Eastern German Bight NCA is supplemented by the adjacent Schleswig-Holstein Wadden Sea National Park and the neighbouring Heligoland seabird sanctuary.