192
10. Life-Stage-Based Recovery Dynamics of M arine Invertebrates
biological structures and vertical relief provided by sessile epifaunal invertebrate communities (Auster and Langton 1999). In add ition to the direct reduction in adult fish stocks, such practices can potentially decrease the survival of juvenile fish and othe r mobile faun a by red ucing prey refuges and
increasing pred ator strike efficiency (Lindholm et al. 1999). Infaunal invertebrates are also capab le of producing biogenic structures and are an important food source for a multitude of species. Despite the importance of
invertebrates in soft-sediment habitats and their susceptibility to human impacts, considerable information is needed before we can accurately assess
and predict how soft-sediment popul ations and communities respo nd to
hum an-induced perturbations.
Current conceptual models describing the disturbance-recovery dynamics
of invertebrates in soft-sediment habitats are largely based on species' adaptations to the abiotic environment (e.g. Rhoads et al. 1978; Pearson and
Rosenb erg 1978). For example, early colonists possess life-history traits
(e.g. fast growth , high rep roductive effort) that facilitate rapid responses to
recently disturbed areas, while other species characteristic of the latter
phases of the recovery process typically have much slower growth rates,
longer times to maturation and reduced reproductive output. The traditional
view has been that recovery process is largely controlled by larval inputs to
disturbed sites from populations residing in surrounding undisturbed portions of the habitat. However, it is increasingly recognized that the recolonization process is actually influenced by two, often indep endent , sources of
colonists- larvae that settle from the water column, and post-settlement life
stages (juveniles and adu lts) that are laterally advected across the seabed
(Gunter 1992). Differences in the relative dispersal ability of the two colonist
pools are predicted to result in scale-depende nt differences in disturbance
recovery rates, variations in population size structure and subseque nt differences in within-p atch popul ation dynamics (Whitlatch et al. 1998, 2000).
The purpose of this chapter is to present a generalized model to assess
the dynamics of patch recovery in relation to 0) the spatial scale of the disturbance and (2) the life-history strategies of the invertebrate species. The
results of the mod el described here provide a basis for und erstanding the
impacts of large-scale anthropogenic disturbances for marine biodiversity,
and will assist managers interested in conserving valuable marine resource s.
10.2. Life-Stage-Based Invertebrate Model
10.2.1. General Model Structure
In this section we describe a simple model to examine the interplay of several factors likely to contribute to recovery dynamics in disturbe d (defaunated) soft-sediment habitats. Specifically, the model examines (1) the influence of background advection rate on transport of post-settlement
10. Life-Stage-Based Recovery Dynamics of M arine Invertebrates
biological structures and vertical relief provided by sessile epifaunal invertebrate communities (Auster and Langton 1999). In add ition to the direct reduction in adult fish stocks, such practices can potentially decrease the survival of juvenile fish and othe r mobile faun a by red ucing prey refuges and
increasing pred ator strike efficiency (Lindholm et al. 1999). Infaunal invertebrates are also capab le of producing biogenic structures and are an important food source for a multitude of species. Despite the importance of
invertebrates in soft-sediment habitats and their susceptibility to human impacts, considerable information is needed before we can accurately assess
and predict how soft-sediment popul ations and communities respo nd to
hum an-induced perturbations.
Current conceptual models describing the disturbance-recovery dynamics
of invertebrates in soft-sediment habitats are largely based on species' adaptations to the abiotic environment (e.g. Rhoads et al. 1978; Pearson and
Rosenb erg 1978). For example, early colonists possess life-history traits
(e.g. fast growth , high rep roductive effort) that facilitate rapid responses to
recently disturbed areas, while other species characteristic of the latter
phases of the recovery process typically have much slower growth rates,
longer times to maturation and reduced reproductive output. The traditional
view has been that recovery process is largely controlled by larval inputs to
disturbed sites from populations residing in surrounding undisturbed portions of the habitat. However, it is increasingly recognized that the recolonization process is actually influenced by two, often indep endent , sources of
colonists- larvae that settle from the water column, and post-settlement life
stages (juveniles and adu lts) that are laterally advected across the seabed
(Gunter 1992). Differences in the relative dispersal ability of the two colonist
pools are predicted to result in scale-depende nt differences in disturbance
recovery rates, variations in population size structure and subseque nt differences in within-p atch popul ation dynamics (Whitlatch et al. 1998, 2000).
The purpose of this chapter is to present a generalized model to assess
the dynamics of patch recovery in relation to 0) the spatial scale of the disturbance and (2) the life-history strategies of the invertebrate species. The
results of the mod el described here provide a basis for und erstanding the
impacts of large-scale anthropogenic disturbances for marine biodiversity,
and will assist managers interested in conserving valuable marine resource s.
10.2. Life-Stage-Based Invertebrate Model
10.2.1. General Model Structure
In this section we describe a simple model to examine the interplay of several factors likely to contribute to recovery dynamics in disturbe d (defaunated) soft-sediment habitats. Specifically, the model examines (1) the influence of background advection rate on transport of post-settlement