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epresent those found establishing in that environment. For this reason, a weed survey
was carried out during 1997 to investigate the effects of V. subsimplex mats which
established naturally on Drum Sands. The results from this survey indicated that V.
subsimplex, at the biomass which naturally established, had an enriching effect on the
faunal communities present. The numbers of P. elegans particularly increased mainly
due to increased larval recruitment. The results of this survey suggested that natural
weed establishment on Drum Sands was very important in structuring the benthic
communities. V. subsimplex, although significantly increasing the numbers of P.
elegans, did not lead to the formation of new P. elegans patches during 1997 since the
accumulated sediments and increased numbers of P. elegans they created were
washed away in the winter storms. However, this could potentially be attributed to the
late development of V. subsimplex during the year of the study. The link between
weed mats and patch formation was further supported by their matching spatial scales,
V subsimplex mats which developed during 1997 were approximately the same spatial
scale as P. elegans patches. Although V. subsimplex led to increased P. elegans
numbers during 1997, it is not known whether this species established at the same
biomass during previous years. Therefore, the link between weed mat establishment
and P. elegans patch formation cannot be proven.
Noji and Noji (1991) suggested that populations of spionid polychaetes have been
commonly found to increase rapidly following disturbances to form high densities and
display typical opportunistic life history patterns. They therefore implied that
sediment disturbance was a precursor in the formation of patches. This was
investigated in Chapter 6. Two aspects of the effects of sediment disturbance were
investigated. Firstly, the response of P. elegans to small-scale sediment disturbance
was investigated, and secondly, P. elegans larval and adult recruitment following a
disturbance in established patches was compared with non-patches. While the first
specifically relates to the possibility of a link between P. elegans patch formation and
sediment disturbance, the latter pertains to the maintenance of established high-
density patches.
The response of P. elegans to the simulated sediment disturbances was related to its
reproductive behaviour. During periods of high larval availability, P. elegans was
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