Distribution outside the British Isles
All of the sea pen species and the major megafaunal burrowers have
distributions which extend beyond British and Irish waters. Aspects of the ecology of
several megafaunal burrowers have been studied elsewhere, notably in the Mediterranean
(eg. Dworschak, 1982; Pervesler & Dworschak, 1985; Ziebis et al., 1996), but there
have been fewer community-level studies using SCUBA or underwater video. However, recent
towed camera surveys have shown that heavily-burrowed muds exist in several areas of the
Adriatic and Aegean Seas (Marrs et al., 1996), indicating the presence of megafaunal
communities comparable to those known from British waters. In the Adriatic, crustacean
burrowers include Nephrops norvegicus, Jaxea nocturna, Upogebia spp. and the
mantis shrimp Squilla mantis (Atkinson et al., 1997). The fauna also includes a
large echiuran worm, Maxmuelleria gigas (Atkinson et al., in press). In much deeper
water (> 400m) in the Evoikos Gulf, Aegean Sea, the mud bottom is burrowed by Nephrops
norvegicus, Calocaris macandreae, Callianassa subterranea and (probably) Maxmuelleria
gigas (Marrs et al., 1996). Unusually, the burrowing community here also
includes large numbers of another echiuran worm, Bonellia viridis, a species
previously recorded only from hard substrata (Hughes et al., in press). These observations
suggest that analogues to the Sea pens and burrowing megafauna biotope complex
will eventually be found to be widespread on suitable substrata in the Mediterranean area.
Thalassinidean mud-shrimps are common and diverse in coastal and
continental shelf sediments throughout the world. They have been found to be important
agents of bioturbation in tropical lagoons (Suchanek & Colin, 1986; Suchanek et al.,
1986). Other groups of burrowing megafauna have been barely studied outside north-west
Europe, but there is no reason to doubt that future work will result in the identification
of new species (eg. Rogers & Nash, 1996) and confirm the importance of these animals
within sediment biotopes worldwide.
Various species of sea pen are common elements of the benthic fauna
throughout the worlds oceans, from shallow coastal waters to the deep sea (eg.
Langton et al., 1990). The few detailed studies of their ecology refer to species found on
the Pacific coast of North America (Birkeland, 1974; Kastendiek, 1976; Davis & Van
Blaricom, 1978). Where relevant to the British species, these will be discussed in
Chapters IV and V.