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CHAPTER 3
THE POPULATION STRUCTURE AND REPRODUCTIVE
BIOLOGY OF PYGOSPIO ELEGANS ON DRUM SANDS
INTRODUCTION
Natural and anthropogenic disturbances have been shown to be important factors
influencing the structure of marine soft-bottom communities (Levin, 1981; 1984a;
Zajac and Whitlatch, 1982a; 1982b; Dobbs and Vozarik, 1983). The effect of a
disturbance on the marine benthos is partly determined by the scale and intensity of
the disturbance. A disturbance such as a natural storm, for example, can result in the
large-scale defaunation of the sediment (Dobbs and Vozarik, 1983). Increased wave
and current action resulting from storms erode the sediment surface causing high
species mortality and/or the redistribution of infauna (Rees et al., 1977) or severe
reductions in salinity and dissolved oxygen concentrations cause the mortality of
many species (Boesch et al., 1976; Santos and Simon, 1980a). Such a disturbance
often results in a heterogeneous environment (Levin, 1984a).
A number of species have developed opportunistic life histories enabling them to
exploit disturbed habitats (Grassle and Grassle, 1974). In general, opportunists are
characterised as having a low reproductive age, high fecundity, strong dispersal ability
and a short life span (Pianka, 1994). These characteristics enable opportunists to
rapidly colonise an area under favourable conditions, although they tend to be unable
to compete with non-opportunists. Many polychaete species such as Capitella
capitata (Warren, 1976) and the spionids Pygospio elegans (Muus, 1967; Anger,
1977), Polydora cornuta (formerly P. /igni)(Zajac, 1991) and Streblospio benedicti
(Levin and Creed, 1986) have been shown to rapidly increase in numbers following a
disturbance (Grassle and Grassle, 1974; Pearson and Rosenberg, 1978). These
polychaetes, with the exception of P. elegans, have been particularly well studied in
relation to their opportunistic nature.
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