Under the sea: exploring Skomer's marine life

For much of the spring and summer, Skomer is a hive of activity with over a million seabirds filling the cliffs and burrows, many of them busily raising chicks. The sights, smells and sounds of this breeding rush are hard to miss, from puffins diving into burrows with beaks full of sandeels to the cacophony of calls from the cliffside colonies. This abundance of life, however, is only the tip of the iceberg; equally impressive natural wonders reside beneath the waves.

Shanny © Becci Jewell

Blue jellyfish © Becci Jewell

Moon jellyfish © Becci Jewell

Dive in and take a moment to recover from the shock of the chilly Atlantic waters. Once your breath has slowed and your eyes adjusted, a multicoloured world awaits. Seaweeds in all shades of brown, red and green rise from the seabed, keeping time with the wash of the waves. Splotches of bright pink encrusting algae coat the rocks beside cushions of vibrant orange breadcrumb sponge and clusters of lemon-yellow dogwhelk eggs. A pulsating rainbow appears before you as a translucent comb jelly propels itself through the water, beating rows of combs scattering the light in all directions. On encountering a tasty morsel (friends and family included), this seemingly featureless creature yawns wide and engulfs their prey in a flash. Smaller and more spherical but equally as alien, sea gooseberries trail two long tentacles, fishing on the go. There’s life everywhere you look.

Comb jelly © Becci Jewell

The seas around Skomer are so rich in marine life they’ve been protected by a Marine Conservation Zone since 2014 and were recognised as a Marine Nature Reserve for 24 years before that. The incredible biodiversity here is due to the variety of habitats found around the island, the strong tidal flows, and the influence of warm and cold currents. Steep and exposed cliffs, wave-swept rocks and sheltered bays provide a multitude of homes for many different species, the strong tidal flows deliver food and nutrients, and oceanic currents bring warm-water species from the south and cold-water species from the north. You’ll find bright red multi-armed sunstars from the north living alongside scarlet and gold cup corals and yellow trumpet anemones from the south in a colourful cocktail of marine life.

Two metres tall and with broad brown blades, kelp is a giant among seaweeds. What’s more, it’s an ecosystem engineer creating habitat and boosting species richness by providing shelter, habitat and food for a whole host of marine species. In North Haven, spider crabs shelter amongst the kelp, clutching at the stipes or lumbering slowly across the seabed on their long, long legs. Wrasse briefly emerge from the kelp canopy whilst, if you have the patience to look for them, tiny blue-rayed limpets cling to the blades. These miniature limpets, with electric blue stripes on their fingernail-sized shells, graze the algal film found on kelp fronds. What’s more, kelp also absorbs and stores carbon dioxide, improves water quality and helps buffer the shoreline from stormy seas – a real champion of our oceans.

Spider crab © Becci Jewell 

Blue-rayed limpet © Becci Jewell

Kelp forests © Becci Jewell

There’s more. North Haven is home to seagrass (also known as eelgrass), the only underwater species of flowering plant found in Britain, and it’s another ecosystem engineer. Its roots stabilise the sediment in which it grows, in turn improving water clarity. It provides food and shelter to many species, and it absorbs and sequesters carbon. Perhaps most importantly though, seagrass beds are important nursery grounds for a huge number of species including the juveniles of many commercially important species of fish. Seagrass is very rare in Wales and is now being actively restored all around the UK, including in nearby Dale. With such an impressive skillset, it’s little wonder.

Eelgrass © Becci Jewell

Eelgrass © Becci Jewell

Sea Gooseberry © Becci Jewell

Comb jelly © Becci Jewell

The range and breadth of marine species that inhabit and depend on the waters around Skomer is vast. From the tiny Cornish sucker fish sheltering beneath boulders as the tide retreats, to the much feared (but incredibly beautiful) jellyfish, the summer schools of mackerel, the seals that haul out on the beaches, and the squid-scarred Risso’s dolphins that visit the Sound. All play their part in the dynamic marine ecosystem, the very same ecosystem on which Skomer’s seabirds depend. Let’s show them some appreciation on our next visit to Skomer and keep doing all we can to save our seas.

Cornish sucker fish © Becci Jewell

Blue jellyfish © Becci Jewell

 - Becci Jewell, Skomer Volunteer