Reproductive seasonality is unclear, but spawning probably occurs largely over winter and settlement in early spring. George & Warwick (1985) found major settlement in the Bristol Channel to occur in March, which is in agreement with the observations of Wilson (1970; 1971) working in the Plymouth area, who generally found a spawning period from January - March and a settlement period from March to April. Bhaud (1972) reported larvae of Sabellaria spinulosa in the plankton from December - March in Mediterranean populations. However, according to Garwood (1982) on the north-east coast of England larvae were found in the plankton from August to November. The MBA (1957) reported the breeding season according to three separate authorities as "May", "September", and "Jan-Sept, fertilisations made and larvae reared" in the Plymouth area.

The larvae spend between six weeks and two months in the plankton (Wilson, 1970) and so dispersal range is likely to be considerable.

Experimental lab work by Wilson (1970) showed that Sabellaria spinulosa larvae are strongly stimulated to metamorphose and settle by cement secretions of adult or newly settled young S. spinulosa. Scallop shells, especially Pecten maximus, appeared also to have some slight settlement inducing properties; oyster shells, with which Sabellaria spinulosa are often associated in the southern North Sea, were not tested. While S. alveolata larvae were stimulated to metamorphose by cement secretions of S. spinulosa, the opposite was rare; S. spinulosa are clearly more choosy in this respect. It appeared that in the absence of suitable stimulation metamorphosis and settlement sometimes occurred but always more slowly.

Rees and Dare (1993) considered that Sabellaria spinulosa had low recruitment, awarding it 1 on a four point scale. Evidence from the Bristol Channel (George and Warwick, 1984) and the southern North Sea (Linke, 1951; Michaelis, 1978) suggests that fecundity and recruitment may be very variable, at least in some areas (see also under longevity and stability, below).

Detailed reports were not found but growth appears to be rapid. Where S. spinulosa acts as an annual species sheets up to 2-3 cm thick develop during a single growing season (essentially spring and summer) (R. Holt pers. comm.). Very rapid growth is also implied by the observations of Linke (1951) as translated by Wilson (1971).

Linke (1951) reported that spawning of intertidal S. spinulosa reefs in the southern North Sea took place during the first and second years.

From survey work on the Northumberland and North Yorkshire coasts, R Holt (pers. comm.) suggests that Sabellaria spinulosa often acts as a fast growing annual. Areas where S. spinulosa had been lost due to winter storms appeared to recolonize quickly up to the maximum observed 2-3 cm thick sheet during the following summer. Many thin crust-like forms of S. spinulosa are probably annual or transient features of this sort, but there are reports of more stable communities, as below.

The melon sized aggregations found in sandy areas by Attrill (pers. comm.) appeared to be of too great a diameter to be created in one year. However, it is also possible that they are seasonal features which are added to each year, whether or not individual worms are perennial.

The reefs found recently in the mouth of the Wash are clearly accumulations created over a number of years as they stand up to 30-60 cm proud of the seabed, and there is a well developed infauna and epifauna, but no detailed information on reef development is available (Foster-Smith, pers. comm.).

George & Warwick (1985) made seasonal observations in the Bristol Channel. They concluded that in the year of study the juvenile settlement was low and that the observed density of adults could not be maintained by that degree of recruitment. They reported that the majority of the reef was composed of S. spinulosa over one year old, but gave no further indication of potential ages. However, they observed that most of the species found within the reef matrix were slow growing and long-lived with a very low turnover rate, implying that the reef itself must have been relatively old and stable. They also pointed out that, since Sabellaria alveolata can live for nine years (Wilson, 1971), it is quite possible that S. spinulosa could also be long-lived.

Wilson (1971) also discusses the observations of Linke (1951, original reference not seen by present authors) on Sabellaria spinulosa in the southern North Sea. Linke apparently described the sudden appearance of massive colonies on stone-work of protective groynes uncovered at low water on the island of Norderney, Fresian islands. In 1943 no colonies were present (time of year of this observation is unknown) but by September 1944 there were reefs 6-8 m wide and 40-60 cm high stretching for 60 m along both sides of three groynes and for 10 m around their broad ends. Linke assumed that settlement took place in 1944. In the summer of 1945 many colonies were dead and those remaining ceased growth in the autumn. Spawning took place in both their first and second years. Small scattered clumps were alive in 1946 but it is not known if they were from the 1944 settlement. Local fishermen confirmed that such reefs did occur annually here and there in other localities, though Linke (1951) observed that in this particular locality there had been only scattered individuals for decades. Wilson (1971) attributed the mass settlement to a swarm of larvae which were induced into settling after having been washed into the area of the scattered individuals. This suggests that perhaps the ability of newly settled young to stimulate settlement of larvae can "accelerate" the settlement process once it has started.

Michaelis (1978) reports that during the 1950s such intertidal populations became rare in this area but gives no explanation. He mentions that S. spinulosa was still present subtidally in the area, however.

Neither of these authors appears to have considered the possibility that these reefs could have been Sabellaria alveolata misidentified as S. spinulosa. Sabellaria alveolata has not been reliably reported on the east coast of England (Cunningham et al., 1984) and so it must be assumed that the identifications were correct.

S. spinulosa is a filter feeder, but no detailed information on feeding was found (but see information on feeding in the related species S. kaiparaensis in the section on S. alveolata above).

No information on this subject was found.

The thicker, and probably more permanent, crusts or reefs seem to have a considerable influence on the benthic community structure (e.g. Connor et al., 1996). George & Warwick (1985) mentioned that Sabellaria spinulosa reefs contained a more diverse fauna than nearby areas, and NRA (1994) found sites in the Wash associated with S. spinulosa to have more than twice as many species and almost three times as many individuals (excluding the Sabellaria themselves) as sites with low, or no, S. spinulosa. In the NRA survey sites the distinction between ‘S. spinulosa sites’ and ‘low or no S. spinulosa’ was made at only 100 individuals per 3 grab samples (covering 0.3 m²), raising the possibility that even relatively sparse S. spinulosa can strongly influence community structure. Connor et al. (1997) describe S. spinulosa communities with attached Polydora tubes, and with an infauna of typical sublittoral polychaete species, as well as the bivalves Abra alba and Nucula nitidosa, and an epifauna including tubeworms, pycnogonids, hermit crabs and amphipods. All of the species reported are found widely in other communities.

The well developed reefs of S. spinulosa found recently in the mouth of the Wash (see chapter II) appear to have a rich associated infauna and epifauna, although detailed studies of the associated biota have not yet been published. A report on recent surveys is in prep (Foster-Smith et al., in prep) but has not been seen by the authors; the following is from Foster-Smith (pers. comm.). From a combination of video footage and grab sampling, errant polychaetes and crabs appear to be particularly numerous within the reef itself. Sedentary species such as anemones were also seen although these were not so obviously important. High densities of shrimp like organisms, probably mysids, could be seen immediately above the reef on video footage. There was an obvious increase in richness of the associated infauna and epifauna with increasing S. spinulosa cover.

It is clear that there is often a rich and probably diverse community associated with well developed S. spinulosa reefs but there are presently few details.

Pink shrimp Pandalus montagui are often closely associated with S. spinulosa reefs, to the extent that fishermen pursuing Pandalus have been reported to use small trawls to search for lumps of S. spinulosa which they regard as an indication of good fishing grounds (Warren & Sheldon, 1967).

Warren (1973) and Warren & Sheldon (1967) reported that Sabellaria spinulosa, probably along with other associated organisms, can be an important food source for pink shrimp Pandalus montagui. The likely importance of this in terms of potential influences on the reef or associated species is not known. No further information on predators was found.

George & Warwick (1985) have suggested from observations in he Bristol Channel that growth recruitment of S. spinulosa could be inhibited or even prevented, and fecundity possibly reduced, by dense populations of the brittle star Ophiothrix fragilis.

No information on this subject was found.

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