The effect of grazing gastropods on meiofaunal colonisation of pneumatophores in a temperate mangrove

A field experiment was run to assess how grazing affects meiofaunal colonisation of mimic pneumatophores in a temperate mangrove. The effects of two manipulated factors were tested: mimics (made from wooden dowel rods) were either implanted into the sediment, or suspended just above the substratum; and in addition were either fitted with an aluminium 'snail barrier' or left without. The abundance of meiofauna was estimated on the 4 treatments after 2, 4, 8 and 16 weeks in situ in the intertidal region. After 16 weeks the meiofaunal assemblage was dominated by copepods, and the effect of suspension was highly significant on abundance of the epibiotic assemblage. Mimics suspended above the sediment, out of reach of snails, were fouled with a green algal layer whereas implanted units were not. In contrast, 'snail barriers' were found to be relatively ineffective in preventing access by the dominant herbivorous gastropod Bembicium melanostomum. Meiofaunal assemblages were more abundant on suspended units, but there was greater taxonomic richness at levels of phylum and class on implanted units than on   suspended units. The colonising meiofaunal assemblage was less abundant on implanted mimics than in previous experiments at this study site, and this was attributed to the present experiment being carried out during the dry summer period, when meiofauna on pneumatophores is in decline.