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This reliance upon the early establishment of macroalgae and sediment accumulation
has been proposed for L. conchilega mound development at Tentsmuir Beach, St.
Andrews, by Carey (1987). Carey (1987) suggested that the formation of high-density
patches of L. conchilega, together with accumulated sediments, were facilitated by
Enteromorpha spp. development and that their survival during winter storms were
dependent upon the presence of the weed to enhance spring recruitment of L.
conchilega. Similarly, Fager (1964) recognised that increased larval recruitment,
allowing worm numbers to build up before periods of high water movement, was a
prerequisite for 0. fusiformis patch formation in Mission Bay.
The present study on Drum Sands did not give any insight as to the possible reasons
why V. subsimplex establishment was spatially heterogeneous. One would have
expected that algal mats would most likely establish on P. elegans patches since the
hydrodynamic effects of the worm tubes and stabilised sediments (see Chapter 8)
encountered there may have facilitated algal spore settlement. However, this was
clearly not the case: although macroalgal mats did establish on P. elegans patches
many of the patches remained weed-free and weed covered many non-patch
sediments. This suggests that algal V. sumbimplex mat development, at least during
the year of study, reflected a cause of the observed faunal changes rather than an effect
of the ambient faunal assemblages. It could be concluded that V. subsimplex mat
formation was determined by other, non-investigated factors.
In conclusion, this study has indicated that V. subsimplex, a green filamentous alga
with a very different morphology from algal species previously investigated by
surveys (Perkins and Abbott, 1972; Nicholls et al., 1981; Wiltse et al., 1981; Reise,
1983a), had an enriching effect on the faunal communities of the intertidal sandflat
Drum Sands. It is likely that this effect, which contrasts with those observed in other
descriptive surveys (and the controlled algal-implantation experiment in Chapter 4),
was due to a relatively low weed biomass although the effect of weed morphology
may have also been an important factor. Increased numbers of the most abundant
species, P. elegans, was due to increased larval recruitment either via increased
settlement and/or increased larval survivorship. This study also indicated that a link
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