The Berwickshire & North Northumberland Coast European marine site is noted for its extensive and highly diverse sea caves, both within the intertidal and shallow water. There are partly submerged sea caves both in the sandstone cliffs to the north of Berwick and in the limestone at Howick and on the north side of Lindisfarne. Submerged sea caves occur in the volcanic rock at St. Abbs and near the Farne Islands.

The types of plants and animals found in sea caves are influenced by several key factors. Height up the shore will determine how long the cave is uncovered by the tide. The orientation of the cave will determine the availability of light and the amount of wave exposure and scour, as small boulders and stones are washed around the cave floor. These factors can result in a zonation of marine life in a cave as the conditions gradually change from light and exposed near the mouth, to dark and sheltered further inside.

Those caves higher on the shore are often colonised by lichen and microscopic algae, which will be grazed by a variety of invertebrates such as limpets (Patella vulgata) and periwinkles (Littorina spp.). Colonies of mussels, along with barnacles (Balanus crenatus), ascidians such as (e.g. Dendrodoa grossularia) and purse sponges (Grantia compressa) may also be present depending upon the degree of scouring by pebbles, stones or sand. The zoned pattern of plants and animals in caves occurring on the lower shore often consists of a turf of algae near the entrance including the red encrusting algae Audouinella spp. occurring in dense red mats which trap sand. Further into the cave, the walls become dominated by sponges, hydroids and anemones.

Subtidal sea caves are generally subject to less water movement and may accumulate silt or sediment on the cave floor. Equally, these caves are not exposed as the tide goes out. Consequently, the communities of plants and animals found in subtidal caves tend to be more diverse. Sponges, soft corals, sea squirts and jellyfish larvae are found in deeper cave systems. These caves also provide shelter for crabs (Cancer pagurus) and lobsters (Homarus gammarus).

Within the moderately exposed reef system of the Berwickshire and North Northumberland coast, the shelter provided by these caves is an important part of the ecosystem.

The location of sea caves within the European marine site is shown in the Map Gallery

Pictures of some of the animals that live in sea caves can be seen in Sights and Scenes