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Size-frequency analysis - Only 2 species were considered sufficiently abundant to
carry out size-frequency measurements, these were P. elegans and C. capitata. The
sizes of the bivalves C. edule and M. balthica were examined and it appeared that for
both these species colonisation was via adults and that no differences between patches
and non-patches were apparent.
Figures 6.3(i-vi) show the size-frequencies of the P. elegans individuals after 3 weeks
colonisation for each of the 3 experiments. In April, colonisation of azoic sediments
in patches and non-patches produced similar size-frequency distributions (p=0.389,
p>0.05; x2 goodness of fit and K-S tests, respectively; see Table 6.1(i)). Colonisation
of azoic sediments occurred predominantly via larval settlement with very low
numbers of adults appearing in the azoic sediments after 3 weeks, even within P.
elegans patches. Since the size-frequency distributions of juveniles in the azoic
sediments were very similar to those from ambient sediments at this time (see Chapter
8, Figure 8.2(i-ii)), the beginning of intense larval settlement at Drum Sands probably
started at approximately the same time as the azoic sediments were implanted, i.e.,
18th April 1997.
In contrast to the results from April, in August there were statistical differences
between the P. elegans size-frequencies in the patch and non-patch azoic samples
(p=0.001, p