Diving at St. Abbs
The outstanding scenery of the Berwickshire coastline extends much further than a coastal walker might imagine. Although the cliffs stand in places around 100m high, they also extend up to another 30m below the sea. And if anything, their shape and form is even more dramatic than on land
The rocks of St. Abbs Head are primarily a combination of soft red sandstone and much harder volcanic upthrusts. Because the headland juts out significantly into the North Sea, it forms a major obstruction to the tidal flow. Twice a day in both directions, the pent up water pours round the headland. This movement, coupled with the action of the waves and swell when the sea is rough, has over aeons of time, carved walls, tunnels, gullies and archways that form some of the finest underwater scenery around the British coast.
Typical of this, just a short swim from the harbour wall at St. Abbs, an insignificant, seaweed covered rock shows above the water at about half tide. It gives no hint of what lies below the surface and before divers came on the scene it was known to the local fishermen as the Sluts. Nothing could be more inappropriate and by common consent, it is now universally referred to as Cathedral Rock - a huge arch rising from the sea bed in which you could park a double deck bus with room to spare! Above it is a smaller flatter arch which a diver can swim through comfortably. The walls are covered in an amazing range of encrusting marine life and when the sunlight pours through it, it makes a marvellous spectacle. This rock coupled with other excellent dive sites just off the harbour wall has led to this becoming the most popular shore diving site in Britain.
Diversity & Visibility
The geographic position of the Marine Reserve means that it benefits from a flow of Atlantic water entering the North Sea around the northern tip of Scotland but also from a cooler Arctic influence. This results in a diverse mix of marine species from both cold and relatively warm water. For instance, the Devonshire cup coral which is very common on western shores is found here in small numbers but probably does not exist much further south in the North Sea. Similarly, species such as the beautiful Bolocera anemone and the Wolf-fish are primarily Arctic species but they are found off the Berwickshire coast in good numbers.
The Marine Reserve is situated well away from major centres of population and industry and consequently, effluent discharges into the sea are minimal. Water quality is improving as new sewage treatment plants are being installed up and down the coast at various locations and as a result, the underwater visibility in the area can be excellent. Spring tides, on-shore winds and plankton blooms can affect this but ten to twelve metres visibility occurs regularly whilst at some point each year, twenty metres visibility can be found.
The Kelp Forest
On a typical dive off St. Abbs Head from the surface to a depth of about 30m, you will go through a whole cross section of marine life zones. Firstly, attached to the rocks is a thick band of shiny, greeny-brown kelp down to a depth of about 8m. These large plants stand erect and swaying in the current. With sunlight dappling the rocks around their holdfast root systems and small fish darting around, it has a beauty all of its own and it is easy to see why this zone is known as the kelp forest. Kelp fronds are very slippery and only a few specialised animals such as hydroids and sea mat can make a home on them. So too can one or two sea slugs which prey on them. A large fish, the Ballan Wrasse, is often found amongst the kelp. These are well accustomed to visiting divers and often will swim up to them looking for hand outs.
The rocks between the kelp holdfasts can be a blaze of colour. Often it is a rich mauve due to the encrustation of a brittle algae called lithothamnion but it will be interspersed with other creatures of contrasting colours such as white and yellow anemones, red sea squirts, yellow and green sponge and feathery hydroids.
Down to 15 metres
Below 8m the rocks are less well colonised partly due to reduced light levels but also due to the activities of the edible sea urchin which exists here in huge numbers. On its underside, the urchin has a beak-like mouth and as it steadily progresses across the rocks, the beak grazes the surface. Very few encrusting animals can resist this and many rocks remain bare as a result. However, this does mean that other creatures which occupy this area are more easily visible. The common topknot - a type of flatfish that lives exclusively on rocks - can be found here. It relies on total immobility to avoid detection and it is very easily overlooked. So confident is it that it will not be seen that it does remain still even when you are just centimetres from it allowing superb opportunities to observe and photograph it. The lesser octopus is often seen here and nowadays is extremely common due to the overfishing of cod which were one of its main predators. The grotesque angler fish is common in some years around this depth but again is a master of disguise as it lays in wait for its prey. Capable of swallowing fish up to its own size by inflating its body with water, these fish (which grow up to 25kg) are known on occasions to swim up to the surface and take sea birds with one powerful gulp!
At a depth of about 15m. the ground falls steeply away and particularly off the SE and NW corners of St. Abbs Head where the tidal flow can be quite strong, the rocks and walls are covered in soft corals. In orange or pure white and standing about 20cms in height, they make a magnificent sight covering every surface in such profusion that it is impossible to see the rock surface itself. Each soft coral colony consists of several fleshy projections which are surrounded by a haze of polyps trapping tiny planktonic prey from the mass of water moving past these exposed locations. The polyps give the corals a swollen puffy appearance and it is not difficult to see how they got their common name of dead man's fingers.
The Tide Exposed Zone
Many of the animals and plants found in the shallow zones are not present in this near vertical world as it is difficult to find space or secure an anchorage. However, other species are better adapted and thrive. Delicate, feathery brittle stars entwine around the soft corals. The huge thirteen armed common sunstar pushes it way purposefully through them. The eel-like butterfish is able to curl from one to the next as it hunts for food. Edible crabs and velvet fiddler crabs press in amongst the corals and in some places there are huge groups of plumose anemones. Gliding along the cliff walls are many Pollack - a member of the cod family whose sinister expression and jutting lower jaw give it the appearance of some cold water version of the barracuda. The male lumpsucker can be also found here. Up to about 30cms in length, this bulbous, fleshy-lipped fish is one of the more colourful and bizarre inhabitants of the North Sea. In the Spring, they move inshore to breed and the male adopts its breeding colours - anything from pink with black dots to yellow with red fins and lips. Once the female has secured her egg mass into a suitable crevice, the male fertilises them. He then clamps himself to the rock next to the eggs with a large sucker on his underside and stands guard duty for several weeks, fending off marauding crabs and starfish until the eggs hatch.
At about 25m the ground starts to level off and soft corals thin out. In some years many ling (an elongated member of the cod family) will move inshore and this zone is a good place to spot them. This is also the best area to find Wolf-fish - the fish that just about all divers visiting the Marine Reserve wish to see. Mature fish are thick and powerful and with a huge head, permanently projecting front teeth and an unusual blue colouration, they cannot be mistaken for any other fish. In excess of a metre long, the Wolf-fish feeds on crabs and sea urchins which it grinds up with masses of molar type teeth which line its jaws. Despite its formidable appearance, it is quite shy and retiring and almost invariably disappears down a hole as a diver approaches.
Brittle star numbers now increase dramatically and by the time you get to 28m they can totally dominate the bottom. Piled several deep - some yellow, some black but the majority grey with red bands - there are acres of these animals which form a living, moving carpet making an eerie sight as countless millions of waving arms writhe in the current. The only thing that interrupts them are the occasional deep water anemone which can be up to 30 cms diameter and in a range of the most amazing colours.
Diving within the Marine Reserve can be an exhilarating and rewarding experience. Not surprisingly, divers come from all over the UK and increasingly from mainland Europe to enjoy what must surely be some of the most spectacular yet least known wildlife habitats in the country.
Text and Images by Jim Greenfield.