12
R.E Dame et al.
bivalves are suspension feeders and specifically filter feeders. At the ecosystem level, suspension feeders form a functional group that may be composed of a number of similar species.
When suspension feeders are abundant in a particular ecosystem they have
the potential to directly modulate the availability of resources to other
organisms and groups by causing physical state changes in biotic and abiotic
materials (Carpenter and Kitchell 1988; Jones et al. 1994; Dame 1996). In this
process, suspension feeders can modify, maintain and create habitats, and, as
such, these animals are often referred to as ecosystem engineers (Jones et al.
1994). If they transform the environment via the structure of their bodies or
skeletons we view these operations as autogenic (Jones et al. 1994). If they
transform living or non-living materials from one physical state to another,
Jones et al. (1994) calls these processes allogenic. Some suspension feeders,
e. g., oysters in reefs, can exhibit both autogenic and allogenic characteristics
(Dame 1996).
The goals of this chapter are to (1) describe the main types of benthic
suspension feeders that can potentially control certain processes in shallow
coastal ecosystems; (2) compare the system-influencing properties of the
various types of benthic suspension feeders; (3) examine reports of these
suspension feeders transforming specific systems; and (4) through synthesis
suggest why suspension feeders are successful in specific ecosystems.
1.2 Reefs and Beds
1.2.1 Bivalve Molluscs (Bivalvia)
Bivalve suspension feeders can configure dense assemblages in the form of
beds or reefs. Epifaunal species like mussels and oysters may reach densities
with a biomass over 1000 g dry wt m- 2 (Table 1.1; Nixon et al. 1971; Craeymeersch et al. 1986; Asmus 1987; J0rgensen 1990). Infaunal species are less
conspicuous than epifaunal species, but they can also reach very high
densities (Table 1.1). Seed and Suchanek (1992) identified three important
components characterizing mussel beds, and probably also other bivalve
communities: (1) a physical matrix of living and dead shells, (2) a bottom
layer of sediments and biodeposits, and (3) a taxonomically diverse assemblage of associated flora and fauna.
The blue mussel, Mytilus edulis, forms beds on intertidal flats and rocky
shores, with a foundation of empty shells and biodeposited material and
living mussels attached to each other by byssus threads. The three-dimensional structure creates a special community, with a distinct faunal com-
R.E Dame et al.
bivalves are suspension feeders and specifically filter feeders. At the ecosystem level, suspension feeders form a functional group that may be composed of a number of similar species.
When suspension feeders are abundant in a particular ecosystem they have
the potential to directly modulate the availability of resources to other
organisms and groups by causing physical state changes in biotic and abiotic
materials (Carpenter and Kitchell 1988; Jones et al. 1994; Dame 1996). In this
process, suspension feeders can modify, maintain and create habitats, and, as
such, these animals are often referred to as ecosystem engineers (Jones et al.
1994). If they transform the environment via the structure of their bodies or
skeletons we view these operations as autogenic (Jones et al. 1994). If they
transform living or non-living materials from one physical state to another,
Jones et al. (1994) calls these processes allogenic. Some suspension feeders,
e. g., oysters in reefs, can exhibit both autogenic and allogenic characteristics
(Dame 1996).
The goals of this chapter are to (1) describe the main types of benthic
suspension feeders that can potentially control certain processes in shallow
coastal ecosystems; (2) compare the system-influencing properties of the
various types of benthic suspension feeders; (3) examine reports of these
suspension feeders transforming specific systems; and (4) through synthesis
suggest why suspension feeders are successful in specific ecosystems.
1.2 Reefs and Beds
1.2.1 Bivalve Molluscs (Bivalvia)
Bivalve suspension feeders can configure dense assemblages in the form of
beds or reefs. Epifaunal species like mussels and oysters may reach densities
with a biomass over 1000 g dry wt m- 2 (Table 1.1; Nixon et al. 1971; Craeymeersch et al. 1986; Asmus 1987; J0rgensen 1990). Infaunal species are less
conspicuous than epifaunal species, but they can also reach very high
densities (Table 1.1). Seed and Suchanek (1992) identified three important
components characterizing mussel beds, and probably also other bivalve
communities: (1) a physical matrix of living and dead shells, (2) a bottom
layer of sediments and biodeposits, and (3) a taxonomically diverse assemblage of associated flora and fauna.
The blue mussel, Mytilus edulis, forms beds on intertidal flats and rocky
shores, with a foundation of empty shells and biodeposited material and
living mussels attached to each other by byssus threads. The three-dimensional structure creates a special community, with a distinct faunal com-