206
10. Life-Stage-Based Recovery Dynamics of Mar ine Invertebrates
will hasten the recovery of a species to its predisturb ance den sity, relative
to species with opposite life-history traits. When patches are small and
post-settlement immigration is high, however, both types of species can recover in a comparable amount of time 0-2 weeks). Furthermore, the interaction between species life-history and patch size has implications beyond
recovery time. Compo sitionally, large patches will gene rally be dominated
by opportunistic species (e.g, Polydord), whereas small patches will have a
mixture of early and late successional species types (e.g, both Nepb tys and
Polydord). Although the present model does not include interactions between the two species, such interactions may be very important in facilitating or arresting the recovery process (e.g. Gallagher et al. 1983; Whitlatch
and Zajac 1985).
Another implication of the model is the importance of juvenile life-stages
(newly settled recruits) in the recovery process . As post-settled colonists, juveniles are relatively more important than adults. Most likely, this is because
(1) juveniles are more abundant than adults in the ambient area; and
(2) adult immigrants are allowed to die of old age. The model, which treats
each life-stage independently, provides a more holistic view of recovery dynamics by these polychaete specie s. Experimental studies are often forced to
limit their focus to a single size or life-stage, and recently-settled stages (recruits) are usually neglected in favor of studying factors influencing larval
supply or adult-adult interactions. Because we currently possess relatively
little information on recruitment processes to the sea floor, researchers may
be missing a significant contributor to the dynamics of benthic systems.
Relatively little is known as to whether immigration is primarily active or
passive, and virtually nothing is known about the magnitud e of immigration.
Late successional species (e.g. Nepbtys) that are large and tend to live deeper
in the sediment column, may not be as susceptible to passive advection (i.e.
moving with currents over the seabed). In addition, species may have structural or behavioral characteristics that promote post-settlement dispersal. For
example, Nepbtys is an active swimmer and other large, deep-dwelling
specie s have been caught in near-shore plankton tows at night (e.g. Dauer
et al. 1982). Early successional species , in contrast, are generally small, surface deposit feeders. These forms are much more likely to be dislodged
from the sediment-water interface and passively advected with currents (e.g.
Shull 1997).
While disturbance of the sea floor occurs at a variety of spatial scales,
most of the large-scale benthic disturbances are anthropogenic in origin
(e.g. hypoxic events due to sewage discharge, disposal of dredge spoils ,
dragging of mobile fishing gear across the seabed). An assumption of the
model is that even "large" disturbed patches are relatively small compared
with ambient areas. In nature , with ambient populations intact and contributing both larvae and post-settled colonists, recovery will probably
roughly follow model predictions. Unfortunately, the effects of anthropogenic disturbances on sea floor habitats may often fall outside the realm
10. Life-Stage-Based Recovery Dynamics of Mar ine Invertebrates
will hasten the recovery of a species to its predisturb ance den sity, relative
to species with opposite life-history traits. When patches are small and
post-settlement immigration is high, however, both types of species can recover in a comparable amount of time 0-2 weeks). Furthermore, the interaction between species life-history and patch size has implications beyond
recovery time. Compo sitionally, large patches will gene rally be dominated
by opportunistic species (e.g, Polydord), whereas small patches will have a
mixture of early and late successional species types (e.g, both Nepb tys and
Polydord). Although the present model does not include interactions between the two species, such interactions may be very important in facilitating or arresting the recovery process (e.g. Gallagher et al. 1983; Whitlatch
and Zajac 1985).
Another implication of the model is the importance of juvenile life-stages
(newly settled recruits) in the recovery process . As post-settled colonists, juveniles are relatively more important than adults. Most likely, this is because
(1) juveniles are more abundant than adults in the ambient area; and
(2) adult immigrants are allowed to die of old age. The model, which treats
each life-stage independently, provides a more holistic view of recovery dynamics by these polychaete specie s. Experimental studies are often forced to
limit their focus to a single size or life-stage, and recently-settled stages (recruits) are usually neglected in favor of studying factors influencing larval
supply or adult-adult interactions. Because we currently possess relatively
little information on recruitment processes to the sea floor, researchers may
be missing a significant contributor to the dynamics of benthic systems.
Relatively little is known as to whether immigration is primarily active or
passive, and virtually nothing is known about the magnitud e of immigration.
Late successional species (e.g. Nepbtys) that are large and tend to live deeper
in the sediment column, may not be as susceptible to passive advection (i.e.
moving with currents over the seabed). In addition, species may have structural or behavioral characteristics that promote post-settlement dispersal. For
example, Nepbtys is an active swimmer and other large, deep-dwelling
specie s have been caught in near-shore plankton tows at night (e.g. Dauer
et al. 1982). Early successional species , in contrast, are generally small, surface deposit feeders. These forms are much more likely to be dislodged
from the sediment-water interface and passively advected with currents (e.g.
Shull 1997).
While disturbance of the sea floor occurs at a variety of spatial scales,
most of the large-scale benthic disturbances are anthropogenic in origin
(e.g. hypoxic events due to sewage discharge, disposal of dredge spoils ,
dragging of mobile fishing gear across the seabed). An assumption of the
model is that even "large" disturbed patches are relatively small compared
with ambient areas. In nature , with ambient populations intact and contributing both larvae and post-settled colonists, recovery will probably
roughly follow model predictions. Unfortunately, the effects of anthropogenic disturbances on sea floor habitats may often fall outside the realm