Pelagic prey and benthic predators: impact of odonate predation onDaphnia

Abstract

AbstractInteractions between benthic predators and pelagic prey, such as larval odonates and Daphnia, are often used to describe classic predator–prey relationships in laboratory studies. However, few field studies explore the potential impact of benthic predators on pelagic prey. Recent studies of cladocerans document diel horizontal migration (DHM), where large-bodied zooplankton (i.e., Daphnia) decrease their exposure to pelagic predators by seeking refuge among macrophytes. However, daphnids undergoing DHM may simultaneously increase their likelihood of encountering benthic predators that commonly occur in littoral zones. In laboratory experiments, we showed that dragonfly nymphs (Epitheca cynosura) effectively eliminated all Daphnia within 24 h, regardless of macrophyte presence or architecture. We also tested whether additions of larval damselflies (Ischnura elegans, Coenagrion puella, C. pulchellum) and dragonflies (Somatochlora flavomaculata) (total odonate density of 35–55/m2) significantly reduc...