Variable response by aquatic invertebrates to experimental manipulations of leaf litter input into seasonal woodland ponds

Aquatic invertebrates are crucial components of foodwebs in seasonal woodland ponds, and leaf litter is probably the most important food resource for those organisms. We quantified the influence of leaf litter inputs on aquatic invertebrates in two seasonal woodland ponds using an interception experiment. Ponds were hydrologically split using a sandbag-plastic barrier, and a mesh canopy was suspended over one-half of each pond to intercept autumn leaf fall for four years. Subsequently the mesh canopies were removed so recovery could be assessed. In one wetland pond, overall invertebrate biomass and the biomass of certain functional groups declined in the interception half-pond and then rapidly recovered after litter inputs were restored. In this pond, leaf litter was a crucial resource to invertebrates, which is consistent with findings in other detritus-dominated ecosystems. However, in the second wetland pond the relationship between litter and invertebrates was very different, and interception appeared to benefit rather than harm invertebrates. Invertebrates were sensitive to changes in leaf litter input in both ponds, but interactions were not consistent. Highly variable wetland conditions in ponds (seasonal drying, stagnant water) may complicate litter-invertebrate interaction in these habitats.