Cunningham et al. (1984) noted that placages (sheet-like structure) might impede the drainage of the shore, creating pools of standing water where there would otherwise be none. Further habitat modification, they noted, included stabilisation of mobile sand, shingle, pebbles, small boulders and an increased habitat heterogeneity of exposed barnacle dominated shores and sand scoured rocks.

Sabellaria alveolata larvae spend anything between 6 weeks and 6 months in the plankton (Wilson 1968, 1971) so that dispersal could potentially be widespread. Settlement occurs mainly in existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from S. spinulosa tubes as well as S. alveolata (Cunningham et al. 1984; Gruet 1982; Wilson 1971).

No information available.

There is little detailed mention in the literature of predation on S. alveolata, although Carcinus maenas was a troublesome predator of transplanted portions of reefs in Somerset (Bamber & Irving 1997). Herdman (1919) mentioned that flatfish such as plaice Pleuronectes platessa and sole Solea solea could easily obtain the worms by crunching up the brittle sand tubes. Worms are known to be able retract considerable distances down their tubes (Cunningham et al. 1994; Wilson 1971); it would therefore appear to be difficult for predators to extract worms easily from compact reef masses.

There is evidence to suggest that littoral reefs are, at least in many cases, unstable and there frequently appears to be a cycle of development and decay over periods of up to five years (Gruet 1985, 1986, 1989; Perkins 1986, 1988). Exceptionally, Wilson (1976) observed one small reef from its inception as three small individual colonies in 1961, through a period between 1966 and 1975 where it existed as a reef rather greater than 1 meter in extent and up to 60 cm thick, with major settlement of worms occurring in 1966 and 1970. This reef finally ‘died’ in the autumn of 1975, ironically a period of intense new settlement elsewhere on the same beach (Wilson 1976). In the long term, areas with good Sabellaria reef development tend to remain so.

A typical life span for worms in colonies forming reefs on bedrock and large boulders in Duckpool was 4-5 years (Wilson 1971), with a likely maximum of around 9 years (Gruet 1982; Wilson 1971). However, it is suspected that there are many colonies on littoral cobble and small boulder scars on moderately exposed shores where shorter lifespans are likely due to the unstable nature of the substratum. Wilson (1971) reported that it was possible to age worms to some degree by measuring the diameter of the tube.

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