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mortality and/or erosion were likely to have been factors in this study, i.e., those
larvae settling into patches are less likely to have been eroded in the stabilised
environment of patches and presumably benefit from the increased food supply.
Zajac and Whitlatch (1982a) demonstrated that initial colonisation following small-
scale sediment disturbances were predominantly dependent on the temporal changes
in ambient populations. Although such temporal changes in the ambient communities
on Drum Sands were important in initial colonisation and presumably in later
successional dynamics in the present study, the interspersion of the two plot types
demonstrated that the early stages of succession can vary at small spatial scales
concurrently.
Does the successional stage of a community affect the colonisation mode of early
colonisers?
Two species, i.e., the polychaetes P. elegans and C. capitata, colonised in numbers
sufficiently high for size-frequency analyses. Although no significant differences
were observed in the size distributions of P. elegans colonising azoic sediments of the
two habitat types during April 1997, significant differences during August and
December 1997 were observed due to higher numbers of adults colonising patch azoic
sediments relative to non-patch sediments. There were significant differences
between the size distributions of C. capitata colonising the two habitat types in
December 1997 which suggested that colonisation in patch azoics was predominantly
via adults while that to non-patch azoics was via larvae. The results of the present
experiments, therefore, indicated that in addition to affecting initial community
composition following a disturbance, dense assemblages of P. elegans also affected
the colonisation mode of some species. These patches of increased P. elegans
densities reflected different successional stages from surrounding sediments (Noji and
Noji, 1991).
Many studies have found that post-larval immigration can play a substantial role in
colonisation after a small-scale disturbance (Dauer and Simon, 1976a; Levin, 1984a;
Frid, 1989; Smith and Brumsickle, 1989; Wilson, 1992; 1994). This has been found
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