PARENT SESSION
Tuesday, August 8, 1:30-5:00 pm
COS 34 - Food webs II: environmental and habitat factors
L-11, Lobby Level, Cook Convention Center
Presiders: G Uzochukwu
Influence of crayfish on macroinvertebrate assemblages in a heterotrophic, sandy-bottom stream.
Mitchell, Richard*,1, Feminella, Jack1, 1 Auburn University, Auburn, AL
ABSTRACT- Omnivorous crayfish have been shown in small stony streams to influence both basal resources (e.g. algae, leaf litter) and benthic macroinvertebrate assemblages; however, there have been no similar studies of crayfish trophic role within more heterotrophic, sandy-bottom streams where leaf detritus is the primary basal resource. We conducted a 6-wk enclosure-exclosure experiment in a sandy stream in western Georgia, USA, to assess effects of the crayfish Procambarus versutus on leaf litter breakdown and macroinvertebrate assemblage structure. We used hardware cloth cages (3 mm-mesh, 50 x 50 x 35 cm) to delineate experimental units in a complete randomized design, with 3 cages/block containing 3 crayfish densities (3, 1, and 0 individuals per cage,12, 4, and 0/m2, respectively); 2 additional cages/block that were only partially enclosed served as cage controls. We used male crayfish (size range 15-20 mm carapace length), and artificial American beech leaf packs (Fagus grandifolia, 9.8—10.3 g dry weight), and quantified breakdown and associated invertebrate density, biomass, and richness. Preliminary results indicated that crayfish density did not significantly affect breakdown, but did influence macroinvertebrate assemblages. Macroinvertebrate density, biomass, and richness all were significantly lower in the high– (vs. low–) density crayfish treatment. Our findings suggest that P. versutus, like other crayfish species, is an important determinant of macroinvertebrate assemblage structure. However, unlike other crayfish, P. versutus does not affect basal resources by omnivory, a process that appears to be limited in this species.
Key words: crayfish, omnivory, assemblage structure