Benthic animals – Trap The Faroe Islands

Sea cucumber (*Cucumaria frondosa*) is among the most common benthic animals that live off the Faroe Islands, especially in areas where the bottom is hard.
RIGHTS MANAGED/RITZAU SCANPIX, 2007

The seabed around the Faroe Islands can be roughly divided into the intertidal zone, fjords and sounds as well as the deep water. Within the three areas, the benthic fauna can be divided into different animal communities, each of which is characterised by a few dominant species.

In the intertidal zone, land and sea meet in a changeable environment, where the bottom is exposed at low tide and flooded at high tide. Despite the Faroe Islands’ relatively modest size, tides differ quite significantly in several places. In the west, the difference between high and low tide is thus approx. 1.5 m, and at spring tide even higher, while the tidal amplitude at Tórshavn is only about 20 cm. In addition, the intertidal zone varies with the degree of exposure, just as there can be differences in the salinity of the water.

On the exposed rocky coasts, you can find common barnacle (Semibalanus balanoides) and common limpet (Patella vulgata) as well as rough periwinkle (Littorina saxatilis) and flat periwinkle (Littorina obtusata), the latter, however, only in more sheltered areas. Inside the fjords, where the water is often slightly fresher, the intertidal zone is often characterised by banks of blue mussels (Mytilus edulis). The mussel banks are habitat for many other small animals; shore crabs (Carcinus maenas) live under stones, and there are also many sand-hoppers.

The Faroese fjords and sounds are rarely more than 100 m deep with a current speed of around 5‑10 cm/s. However, the current varies significantly and is decisive for the bottom conditions in the fjords. Where the current is strong, the bottom is hard as the sediments are washed away. At low current speeds, the fjords, on the other hand, have a softer bottom. Here you will find the 10‑15 cm long orangefooted sea cucumber (Cucumaria frondosa) and the soft coral known as dead man’s fingers (Alcyonium digitatum), together with sea urchin (Echinus esculentus) and green sea urchin (Strongylocentrotus droebachiensis). Starfish are also abundant. The two most common species are common starfish (Asterias rubens) and sun star (Crossaster papposus).

In areas with stronger current, the common brittle star (Ophiothrix fragilis) and black serpent star (Ophiocomina nigra) can also be seen. The most common crabs on the hard bottom are the downy hermit crab (Pagurus pubescens) and Atlantic lyre crab (Hyas araneus). Various sea anemones live in shallow waters, while the sandy bottom in the deeper parts of the fjords is home to red whelk (Neptunea antiqua), queen scallop (Aequipecten opercularis), blunt gaper (Mya truncata) and razor shell (Ensis ensis).

In sounds and fjords, stones and rocks are in many places covered by macroalgae, which often form large, extensive seaweed forests. The macroalgae are habitat for a variety of small animals. Colonies of bryozoans grow on the leaves, just like you can find small, colourful nudibranchs together with flat periwinkle (Littorina obtusata) and various species of isopods and sand-hoppers. In addition, spiral tubeworm (Spirorbis spirorbis) often builds its white, approx. 5mm wide, coiled shells on the algae.

As you move away from the coast into deeper water, the bottom changes first to a sandy bottom and then to a softer mud bottom. On the sandy bottom you will find species such as sandworm (Arenicola marina), common whelk (Buccinum undatum) and red whelk, Atlantic lyre crab, various species of hermit crab, ocean quahog (Arctica islandica) and European prickly cockle (Acanthocardia echinata). The softer mud bottom is mainly habitat to various bristle worms and mussels, and it is also here that the Norway lobster (Nephrops norvegicus) digs its holes in the sediment. In areas where the current is a little stronger, you can find banks of northern horse mussel (Modiolus modiolus), which generally resemble very large blue mussels. Even further from shore, you will encounter smaller banks of queen scallop. Various sea sponges can be seen in the deep water, and at approx. 500 m, where the warm and cold water meet, you can encounter the deep-water coral Desmophyllum pertusum.

Further reading