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The size of the defaunated sediment core was chosen to approximately represent the
area disturbed by small-scale disturbances such as the pits created by feeding flatfish.
The scale of disturbance has been shown to result in different successional dynamics
only when the disturbed area varies in size by many orders of magnitude (Wilson,
1992; Ragnarsson, 1996). Therefore, although the size of the disturbed areas in this
experiment was slightly larger than those created by flatfish, similar successional
dynamics would be expected. The sediment cores were implanted without the corers
so as not to restrict immigration of infauna from below the sediment surface which
would be possible after a natural disturbance. The treatment and implanting of the
sediments were identical for both patch and non-patch plots.
The treated sediments were left for 3 weeks before sampling. This time interval was
chosen from the results of preliminary studies carried out in March 1997, together
with the information obtained on colonisation rates following disturbances at this
scale provided by literature review (e.g., Zajac and Whitlatch, 1982a; 1982b; Levin,
1984a; Savidge and Taghon, 1988; Frid, 1989; Hall et al., 1991; Wilson, 1992; 1994;
Ragnarrson, 1996). Preliminary studies involved implanting defaunated sediments for
1, 2, and 3 weeks - only after 3 weeks was there a large increase in colonists (C.
capitata and P. elegans) in both P. elegans patches and non-patches (n=6).
Furthermore, since one of the aims of this experiment was to determine mode of
colonisation, it was important to allow colonisation to proceed for as short a time as
feasibly possible.
The implanted sediments were sampled after 3 weeks by an 8cm internal diameter
corer to a depth of 12cm. Each sample was then sectioned into 2 parts. The top 3cm
were removed and preserved in neutralised 10% saline formaldehyde solution with
0.01% Rose Bengal. These samples were later washed through a 500pm and 212pm
mesh sieve stack in the laboratory. An elutriation method was used to help remove
the fauna from the sediment retained by the 2121.1,m mesh sieve before sorting. This 4-
decantation elutriation method separated all the fauna from the sediment (n=25) apart
from a small number of nematodes which were not analysed. The elutriant was again
sieved on a 2121.1m mesh sieve and juvenile P. elegans and C. capitata removed under
a dissecting microscope (x10 magnification). These were the only two species
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