Fine scale meiofaunal distribution around burrows of ocypodoids (Decapoda, Ocypodoidea) in tidal flat sediments

In tidal flat sediments, larger invertebrates often modify the sedimentary environment in a manner that causes smaller animals, such as meiofauna, to become more abundant. In other words, macrofauna can “promote” meiofauna. In summer (August) and autumn (November/early December) 2007, we investigated centimetre-scale horizontal and vertical profiles of total metazoan meiofaunal abundance and community structure around burrows of Uca lactea (De Haan, 1835) (fiddler crabs) and Scopimera globosa (De Haan, 1835) (sand bubbler crabs) on an intertidal sandflat of the Amakusa Islands, western Japan. Meiofaunal community structure changed significantly with sediment depth around burrows of U. lactea in both seasons, whereas vertical differences were less clear for S. globosa. Although no evidence was found that total meiofaunal abundance or the abundances of certain taxonomic groups were positively influenced by burrows of S. globosa, the abundance of nematodes in subsurface sediment around burrows of U. lactea was significantly higher than in controls in autumn. High concentrations of fresh organic matter had not accumulated in the sediment around burrows of either species of crab. Uca lactea, however, made its burrows in significantly finer sediment than did S. globosa. One possibility is that differences in meiofaunal distribution in sediment around the burrows of the two crabs were the result of habitat and behavioural differences between the species.