Can large branchiopods shape microcrustacean communities in Mediterranean temporary wetlands?

Abstract

It was recently suggested that large branchiopods may play a keystone role in temporary aquatic habitats. Using a microcosm experiment manipulating microcrustacean communities of Mediterranean temporary wetlands (Camargue, Southern France), we tested the following hypotheses: (i) large branchiopods (the notostracan Triops cancriformis and the anostracan Chirocephalus diaphanus) can limit microcrustacean densities through both competition and predation; (ii) notostracans create high suspended-matter concentrations through bioturbation, which can negatively impact microcrustaceans; and (iii) the outcome of these biotic interactions is more detrimental at high salinities. We found a strong predatory impact of T. cancriformis on active microcrustacean populations, but also on dormant populations through the consumption of resting eggs. They also preyed on anostracans and their conspecifics and can indirectly have a negative effect on microcrustaceans through bioturbation, probably by impeding filtering capacities. The presence of C. diaphanus also limited most microcrustacean groups, probably through competition and/or predation. We did not find a significant effect of the tested salinity range (0.5–2.5 g L–1) on the biotic interactions. Our study shows that large branchiopods can shape microcrustacean communities under a wide range of environmental conditions and confirms their potential for a keystone role, especially one of notostracans as top predators.