Above: Baby Cuttlefish © Hazel Munt
Below: Honeycomb worm reef © Hazel Munt, Japanese seaweed © Julie Hatcher
The cuttlefish is not actually a fish but is in fact a mollusc and the species most often seen here is the common cuttlefish, Sepia officinalis, whose white bone can be found strewn on beaches at this time of year. Cuttlefish are closely related to squid and nautili, the latter being an exotic mollusc closely resembling fossil ammonites. Like squid, they are carnivores, preying on fish and small crustaceans such as shrimps and crabs. They use their skin to camouflage themselves from predators and also to ambush their prey; changing colour and texture, to blend in with the plain sandy or dark, seaweed-covered seabed wherever they are. Cuttlefish are one of the most highly developed and intelligent of invertebrates. In early summer cuttlefish gather in coastal waters to breed, after which they die leaving their cuttlebones to wash ashore in large numbers. They are often spotted by divers and snorkelers at this time.
Honey comb worms
In Dorset we are lucky enough to have the reef building honeycomb worm, Sabellaria spinulosa. These worms build tightly packed tubes using suspended sand particles and fixing them onto hard substrates such as the ledges found along the west Dorset coast. They create beautiful reefs with a honeycomb structure which are usually found on the lowest part of the seashore. The reefs, once established, provide wonderful habitat for other species creating crevices for small rockpool fish such as blennies but also providing habitat for seaweed, crabs, other worms and a variety of molluscs. Honeycomb worm reefs are a UK Biodiversity Action Plan habitat and are vulnerable to pollution, coastal development, high intensity storms and from trampling. So be careful where you step whilst viewing these intricate reefs.
Japanese seaweed or wireweed has become prolific not just in the UK but throughout Europe and is now well established. As the name suggests it originates from the Pacific Ocean around Japan and first arrived in the UK in the 1970s. Its range in Europe is steadily expanding as it is able to out-compete many native species. This is a shallow water seaweed usually found from rockpools on the low shore to about 10m depth, attached to rocks and pebbles. It can spread rapidly, growing from pieces that break off from the parent plan and with the right conditions can reach a length of 12m in just one season. On the plus side Japanese seaweed provides shade and shelter for small fish and rockpool creatures although it can shade out our smaller native algae. It can be found growing in the shallows and rockpools of Kimmeridge Bay and at other sites in Dorset.