22
R.E Dame et al.
the structure of their bodies creates and alters a habitat based on their
modulation of water currents.
1.2.3 Sabellids (Polychaeta)
Segmented worms in the Sabellariidae build tubes of agglutinated sand particles composed of quartz and heavy mineral grains, shell fragments, tests,
fecal pellets and sponge spicules (Kirtley and Tanner 1968). These animals
typically construct their tubes on top of one other, forming honey-comb-like
aggregations. With densities of 25,000 individuals m- 2 (Table 1.1), these structures are sometimes categorized as reefs (Herdman 1920; Multer and Milliman 1967) but, because the glue that holds the particles of the tube together
loses its binding capabilities after the animal dies, geologists prefer not to use
the term reef (Wood 1999).
Sabellid worm aggregations are generally found on sandy beaches in the
intertidal and· near subtidal zones where turbulence generated by waves or
fast currents resuspends sand-sized particles that are needed for tube construction (Multer and Milliman 1967). Structures built by Sabella ria alveolata, sometimes more than 1 m across, are known from the English Channel,
eastern Atlantic coast and western Mediterranean coast (Wilson 1971; Gruet
1986). Even larger reef-like structures, up to 100 m wide, are built in the surf
zone by Phargmatopoma lapidos along the southeastern coast of Florida
(Multer and Milliman 1967; Kirtley and Tanner 1968). In both types of aggregations, some type of hard substrate, beach rock, boulders, etc., is thought to
be necessary for reef initiation by the settlement of planktonic larvae. As
sabellid larvae are highly gregarious, this attribute usually establishes a succession of generations that ensures community persistence over long periods
of time (Gruet 1986). There is some evidence that with time each of these
aggregation types develops its own specific community of species (Gore et al.
1978; Porras et al. 1996).
Sabellids are filter feeders that have a specialized feeding structure, the
funnel-shaped fan or crown-filament pump (Riisgard and Ivarsson 1990).
This structure is covered with ciliated tracts that move water through the
filter and convey particles of detritus and plankton to the mouth. Before
entering the mouth, the particles are sorted with fine particles progressing to
the mouth and large particles being rejected. In many sabellids there are three
particle size categories and the medium-size grains are stored for tube construction. Sabellids efficiently remove particles between 3-8 fim {J0rgensen et
al. 1984). Laboratory estimates of filtration rates by sabellids, none of which
are reef builders, range from about 0.5 to 1091 g-l h-l (Table 1.1; Dales 1957,
1961; Shumway et al. 1988; Riisgard and Ivarsson 1990). However, Riisgard
and Ivarsson (1990) argue that the majority of these estimates are low because
R.E Dame et al.
the structure of their bodies creates and alters a habitat based on their
modulation of water currents.
1.2.3 Sabellids (Polychaeta)
Segmented worms in the Sabellariidae build tubes of agglutinated sand particles composed of quartz and heavy mineral grains, shell fragments, tests,
fecal pellets and sponge spicules (Kirtley and Tanner 1968). These animals
typically construct their tubes on top of one other, forming honey-comb-like
aggregations. With densities of 25,000 individuals m- 2 (Table 1.1), these structures are sometimes categorized as reefs (Herdman 1920; Multer and Milliman 1967) but, because the glue that holds the particles of the tube together
loses its binding capabilities after the animal dies, geologists prefer not to use
the term reef (Wood 1999).
Sabellid worm aggregations are generally found on sandy beaches in the
intertidal and· near subtidal zones where turbulence generated by waves or
fast currents resuspends sand-sized particles that are needed for tube construction (Multer and Milliman 1967). Structures built by Sabella ria alveolata, sometimes more than 1 m across, are known from the English Channel,
eastern Atlantic coast and western Mediterranean coast (Wilson 1971; Gruet
1986). Even larger reef-like structures, up to 100 m wide, are built in the surf
zone by Phargmatopoma lapidos along the southeastern coast of Florida
(Multer and Milliman 1967; Kirtley and Tanner 1968). In both types of aggregations, some type of hard substrate, beach rock, boulders, etc., is thought to
be necessary for reef initiation by the settlement of planktonic larvae. As
sabellid larvae are highly gregarious, this attribute usually establishes a succession of generations that ensures community persistence over long periods
of time (Gruet 1986). There is some evidence that with time each of these
aggregation types develops its own specific community of species (Gore et al.
1978; Porras et al. 1996).
Sabellids are filter feeders that have a specialized feeding structure, the
funnel-shaped fan or crown-filament pump (Riisgard and Ivarsson 1990).
This structure is covered with ciliated tracts that move water through the
filter and convey particles of detritus and plankton to the mouth. Before
entering the mouth, the particles are sorted with fine particles progressing to
the mouth and large particles being rejected. In many sabellids there are three
particle size categories and the medium-size grains are stored for tube construction. Sabellids efficiently remove particles between 3-8 fim {J0rgensen et
al. 1984). Laboratory estimates of filtration rates by sabellids, none of which
are reef builders, range from about 0.5 to 1091 g-l h-l (Table 1.1; Dales 1957,
1961; Shumway et al. 1988; Riisgard and Ivarsson 1990). However, Riisgard
and Ivarsson (1990) argue that the majority of these estimates are low because