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Invertebrate larvae, those of polychaetes in particular, are known to be capable of
complex settlement behaviour and substrate selection (see reviews by Wilson, 1958,
and Scheltema, 1974). The significant positive correlation of new recruits with P.
elegans adults during June (replicates 1 and 2) indicate that adult-juvenile
interactions, or at least the hydrodynamics associated with adult's tubes, may perhaps
have helped generate the P. elegans micro-scale patches. Eckman (1983) proposed,
using field observations and experimental manipulation experiments, that species
heterogeneity at this scale may be created by the localised hydrodynamic effects of
polychaete tubes. Facilitation of larval colonisation by tube-builders on intertidal
sandflats has previously been demonstrated (Gallagher et al., 1983; Savidge and
Taghon, 1988; Thrush et al., 1992). Eckman (1979) suggested that local flow patterns
were important in producing the observed micro-scale gregariousness of several
species in Skagit Bay, Washington. In the present study, a significant positive
correlation between new recruits and adults only occurred during June 1997, when
adult densities, and presumably hydrodynamic effects of adult's tubes, in micro-scale
patches reached their highest. Hadfield (1986) and Bachelet (1990) pointed out that
one must be careful when inferring processes responsible for larval recruitment
patterns from field observations. Since some time must elapse between larval
settlement and subsequent sampling, the patterns observed will have resulted from not
only initial settlement but from a number of subsequent processes, each capable of
affecting juvenile distribution patterns. Therefore, it is not possible to suggest
whether the non-random patterns and positive correlations of new recruits with adult
micro-scale patches resulted from non-random larval settlement patterns or from
differential mortality/survivorship of juveniles (Woodin, 1986).
The lack of a significant correlation between P. elegans adults and any other species
indicated that the micro-scale patchiness of P. elegans adults within patches were
probably not generated by interspecific interactions. All other species present within
P. elegans patches were of relatively low abundance and it is likely that none of them
were present in sufficient abundances to significantly affect the spatial distribution of
P. elegans. One possible explanation for the lack of association between P. elegans
and other species (or at least those with planktonic larvae) may be the high densities
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