Specific information on temperature tolerance was not found for this
species, but its widespread distribution, from at least North of the Shetlands to the
Mediterranean Sea, together with its predominantly subtidal habit means that S.
spinulosa is likely to be much less sensitive to temperature changes than the
intertidal S. alveolata, which has been shown to be severely affected by low winter
temperatures - for example, S. spinulosa was not affected by the cold winter of
1963 although many S. alveolata mortalities resulted (Crisp, 1964).
Although individuals can certainly occur intertidally, very dense S.
spinulosa is found almost entirely subtidally; there are no reports of intertidal
reefs in Britain though sporadic dense intertidal reefs have been reported from the
Waddensee, southern North Sea (observations of Linke, 1951 discussed by Wilson, 1971; see
chapter IV). Dense crusts are reported in the infralittoral and may occur in only a few
metres of water; they are also found in the circalittoral but the maximum depth of dense
crusts is unclear. Dense reefs reported by George & Warwick (1985) in the Bristol
Channel were in 41 m of water while recently discovered reefs in the mouth of the Wash are
in 15-25 m (Foster-Smith et al., in prep February 1998).
Suspended sediment and water movement
S. spinulosa requires suspended sand grains in order to form its
tubes; reef communities therefore only occur in very turbid areas where sand is placed
into suspension by water movement. The relative importance of tidal versus wave induced
movements is unclear.
S. spinulosa reefs or crusts will form on hard substrata but this
does not preclude their formation on other substrata (Hiscock, 1991 and pers. comm.).
Several sources suggest that bedrock is not necessary for formation of Sabellaria
spinulosa crusts and reefs, though a somewhat firm substratum is presumably required.
Rees & Dare (1993) describe habitat/ distribution as being typically on shell
(especially oyster valves), sandy gravel or rocky substrata with moderate to strong tidal
flow. Larsonneur (1994) reported that Sabellaria spinulosa dominated communities
were present on rock/pebble bottoms in the Bay of Mont St Michel. He also reported sand
masons Lanice conchilega could sufficiently stabilise sand to allow colonisation by
S. alveolata. It can be speculated that the same process might be possible with Sabellaria
spinulosa too, since Lanice and S. spinulosa are sometimes found
together (e.g. Foster-Smith et al., 1997) and extensive S. spinulosa colonies are
known to occur in essentially sandy areas (see below); this has not been demonstrated,
however. Numerous studies have reported high densities of S. spinulosa in Day grab
or other grab samples which would be unlikely from hard bottoms (Foster-Smith et al.,
1997). Hoare & Hiscock (1974) reported the presence of S. spinulosa associated
with kelp holdfasts (which themselves require a hard substratum).
Larvae are strongly stimulated to settle by cement secretions of adult
or newly settled S. spinulosa (see chapter IV). In the absence of suitable
stimulation metamorphosis and settlement occurs but always more slowly (Wilson, 1970).
There is some suggestion from field observations that established
colonies can increase in extent by addition to the existing colony without the need for
hard substratum; Warren & Sheldon (1967), Schafer (1972) and Warren (1973) have
reported extensive Sabellaria spinulosa colonies in essentially sandy areas.
It is likely that stability of the reefs is to some degree a function
of stability of the substratum. The more transient crusts probably occur principally on
relatively unstable substrata such as mobile sands, while longer lasting reefs could be
limited to more stable substrata such as firm mixed sediments.
Little firm information was found on salinity requirements of S.
spinulosa although well developed reefs seem to be restricted mainly to deeper waters
where salinity would be expected to be more or less fully marine. However, McIntosh (1923)
referred to dense aggregations of Sabellaria (alveolata) being particularly
common in estuaries such as the Tees and Humber. Given that his drawings of the aggregates
of Sabellaria from the Humber looked more like S. spinulosa than S.
alveolata, and the known distribution of the Sabellaria species, it seems these
aggregations were almost certainly misidentified S. spinulosa.
The fragility, or otherwise, of substantial reefs is unclear, although
according to Wilson (1970) the tubes of Sabellaria spinulosa are harder and
stronger than those of S. alveolata. However, S. spinulosa reefs in the form
of widespread sheets are probably surprisingly fragile. George & Warwick (1985)
mention that reefs are broken up sufficiently easily to be sampled by a Day Grab, which is
usually unsatisfactory for obtaining samples on hard or stony grounds. Attrill et
al. (1996) also obtained samples of S. spinulosa reefs which they regarded
as quantitative using a Day grab, as did NRA (1994). R. Holt (pers. comm.) has observed
that crusts of S. spinulosa on cobble and boulders off the Northumberland and North
Yorkshire coasts often break up during winter storms. Elsewhere, however, they do seem to
be more permanent features, although this may be mainly related to the stability of the
physical environment in which they are found rather than any inherent biological
difference. The balls of S. spinulosa found by Attrill (pers. comm.)
are probably considerably more robust, although there is no published evidence for this.
There is much evidence that reefs can be very badly broken up by fishing (chapter VI). The
fragility, or otherwise, of substantial reefs is unclear.