Above: Buoy barnacles on a feather
Below: A marine isopod, Sea chervil and Columbus crab. All photos © Julie Hatcher
Recent storms have brought ashore lots of drifting litter, some of it having travelled from North America. This long-haul litter often carries passengers in the form of goose barnacles, whose long, flexible stalks and shell-enclosed bodies can look rather bizarre, especially if still alive when washed up on the beach.
Goose barnacles belong to the Crustacea, as do crabs, lobsters and prawns, although their life-style is quite different, relying on ocean currents to carry them around while they filter planktonic food from the water using their feathery legs as a sieve. The legs are enclosed within the white protective shell which opens to allow them to reach out and then closes again when they retract. Five different types of goose barnacle have been found recently in Dorset, including the Common goose barnacle, Buoy barnacle, and a rare species with a stripey covering giving it the nickname 'Pyjama barnacle'.
During the autumn months it is usual for large amounts of seaweed to be ripped from the seabed by stormy seas while at the same time there is a certain amount of die-back as the amount of daylight available is reduced. Much of this is stranded on the shoreline or left floating around in the shallows. It provides ample food for a number of species and in particular tends to be occupied by large numbers of isopods, the most familiar of which family are the woodlice. There are many different types of marine isopod of which several have appeared in our nocturnal light trap at Kimmeridge this autumn. Although these are common animals all around the coast of Britain, now is a good time to take a closer look.
A fair amount of sea chervil has been washing up along the beach at Studland and in other locations recently. This spongy, golden or brown coloured item is a detached colony of bryozoans normally found living on the seabed in slightly deeper water. Its form is quite variable and can be like elongated fingers or broad lumps, smooth or knobbly with lobed fingers or smooth edges. The bryozoan is called Alcyonidium diaphanum, and forms an erect colony of microscopic animals which feed on passing plankton. In rough seas the colony can be dislodged from its seabed anchor and end up on a beach strandline. Avoid handling sea chervil as it can cause skin irritation and is responsible for what has become known by fishermen as 'Dogger bank itch'.
At this time of year we sometimes have the privilege to see some exotic visitors to our shores, animals that have travelled across the Atlantic ocean from their home in the Sargasso Sea. Columbus crabs live a nomadic life never coming into contact with the seabed but living on floating rafts of seaweed, driftwood or plastic litter, and even sometimes on turtles! Three Columbus crabs were found recently living on an American fishing buoy which had washed ashore in Worbarrow Bay near Lulworth Cove. Although two of the crabs had died, one was still alive and taken to the Fine Foundation Marine Centre at Kimmeridge, where it was placed with our live goose barnacles in the aquarium.