Movements of upland invertebrates into drying seasonal woodland ponds in northern Minnesota, USA

Abstract

Pitfall trapping of terrestrial invertebrates in and around a seasonal woodland pond in northern Minnesota, USA revealed that large numbers of detritivorous and predaceous invertebrates from the forest floor were entering the pond as it dried. To assess the significance of terrestrial invertebrate foraging on litter processing and survival of aestivating aquatic invertebrates in dry pond basins, a small-scale exclusion study was conducted at two seasonal woodland ponds. Litter and invertebrates collected beneath pond waters were added to either 1-mm-mesh pouches (30×30×5 cm) that excluded large-bodied terrestrial invertebrates or 12-mm-mesh reference pouches that permitted entry. Pouches were left in dry basins for four weeks. Upon retrieval, I found that more aestivating aquatic invertebrates existed in exclusion than reference pouches (P<0.001), suggesting that predation from terrestrial invertebrates might influence aquatic forms. Impacts of excluding detritivorous terrestrial invertebrates on litter processing were equivocal. I argue, however, that the influence of terrestrial invertebrates on seasonal pond ecology has rarely been considered, and it might be significant in terms of overall ecosystem function.