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study. These individuals would not all have been sexually mature adults (see Chapter
3) but here refer to those individuals which had established a fully-formed tube.
Due to the large total number of samples and the small size of the corers, it was not
possible to measure the sediment characteristics of each core and thus correlation
analysis between the numbers of P. elegans and sediment variables was not possible.
Instead, 3 separate transects of 32 contiguous cores were taken from P. elegans
patches for sediment analysis in the same way as for the fauna during February 1998.
Although it would not be possible to carry out correlation analysis of these sediment
results with faunal densities, the results would give an indication as to whether the
sediment variables were spatially heterogeneous within P. elegans patches.
The cores for sediment analyses were taken to a depth of lcm as this was the
minimum depth to provide sufficient sediment for organic and silt/clay content
analyses. The samples were then frozen at -20°C for storage. The water and organic
contents were determined in the same way as described in Chapter 2 while the silt/clay
fractions were determined in the same way as described in Chapter 6.
Data analyses - The spatial distribution of P. elegans individuals was determined
using the same indices of dispersion as those described in Chapter 2. These were the
variance : mean ratio (/), Morisita's index (Id) and the standardised Morisita's index
(Ip). These gave an indication of the intensity of pattern. For new recruits, indices of
dispersion were only calculated for those plots in which their mean densities were 3
individuals per core in order to limit analyses to those months when settlement was
relatively high. These indices were calculated using the NEGBINOM program
(Krebs, 1989) and tested for significance in the same way as described in Chapter 2.
Density plots were produced for P. elegans numbers from the pilot survey and the
adults and new recruits from the monthly samples. These were produced using the
Golden Software Inc. SURFER package version 6.04. The gridding method used for
both the pilot survey and the transect survey abundance data was the nearest-
neighbour gridding method since this is the most suitable for data from contiguous
cores (T. Bresnahan, SURFER; pers. comm.). This method does not interpolate data
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