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the survey area, one must be cautious. The significant positive correlations between
P. elegans abundance and the levels % silt/clay, % organics and sorting coefficient are
supported by the contour plots.
40m survey - spatial patterns
Figures 2.9(i-xi) present the contour maps of the non-randomly distributed species
from the 40m survey and Figures 2.10(i-ix) display the significant correlograms. The
distance classes 1-6 for these correlograms represent inter-sample distances 0-40m,
40-60m, 60-80m, 80-100m, 100-120m and 120-140m respectively. These Figures
suggest that P. elegans, E. cfflava, M. balthica and C. edule formed patches between
40-60m2. Some species, S. martinensis, A. marina, L. conchilega and B. sarsi for
example, formed patches which were located at the edge of the survey area and so it is
difficult to estimate their patch sizes. Although not formally tested, none of the
species appeared to form patches which were spatially correlated with any other
species. The significant positive correlation between P. elegans and M. balthica
(Table 2.5) is not strongly supported by the contour plots, although their patch sizes
were similar they were not spatially correlated.
Figure 2.9(xii-xv) show that the sediment variables appear to have had increased
levels approximately across the middle region of the survey area. The correlograms
indicated that these patches were approximately 80-100m2. The significant positive
correlations between P. elegans and % organic carbon, % silt/clay and sorting
coefficient (Table 2.5) were better supported by the maps for the 40m survey than they
were for the 8m survey with high levels of these variables occurring at approximately
the same areas as the P. elegans patches. The contour plots support the significant
positive correlations between P. elegans and % silt/clay, % organics and sorting
coefficient and suggest that no other species was positively correlated with them.
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