Meiofauna And Crabs In Mangroves And Adjoining Sandflats:

Abstract

Meiofauna distribute widely in most soft substrates in the marine and freshwater realms. Given their small body size (63 to 500 μm) and high density, meiofauna are potential food items for predators such as deposit-feeding brachyuran crabs. Crab bioturbation may also affect meiofaunal assemblages through effects such as translocation to unsuitable microhabitats. This study aimed to investigate the significance and nature of top-down control on the density of meiofauna based on their interactions with deposit-feeding crabs in a mangrove and adjoining sandflat; specifically, whether the interaction is primarily physical or trophic. Field manipulative experiments were conducted within the aggregation zones of soldier crabs (Mictyris longicarpus) and fiddler crabs (Uca vomeris) in a mangrove-lined creek in Southeast Queensland, Australia. Meiofaunal density in five experimental cage treatments (Exclusion, Inclusion with complete crab (‘Inclusion’), Inclusion with ‘disabled’ crab (feeding claw removed, ‘Disabled’), Half-cage, and Ambient) was compared. Removal of soldier crabs from the cages (Exclusion) increasedmeiofaunal density (426±46 ind./10cm2;mean±SE) by 50% over that in the Inclusion treatment (283±22).