Predation and competition are recognised as strong community structuring forces, and these processes are often mediated by keystone species. However, the role of keystone species in the plankton of temporary wetlands has hardly been evaluated. In the present study, the potential structuring role of fairy shrimps (Anostraca, Branchiopoda) on temporary wetland zooplankton communities was assessed. Dry sediments were collected from randomly chosen temporary ponds in the Campo de Calatrava area (Central Spain), and these were rewetted in outdoor microcosms. Zooplankton community dynamics of three wetlands that lacked fairy shrimps (controls) were contrasted with three wetlands that contained Branchinecta orientalis (G. O. Sars) (treatment). ANOVA analyses showed no significant differences in zooplankton community metrics and in taxonomic groups between the controls and treatments. Analyses of similarity (ANOSIM) and similarity percentages (SIMPER) revealed significant differences and a high degree of community dissimilarity within and between treatment levels. The high degree of environmental variability between wetlands compromised the detection of the structuring role of fairy shrimps on zooplankton in the present study. Studies based on manipulative designs could be more appropriate to test for the keystone role of fairy shrimps in temporary wetland food webs. Replicated before-after control-impact (BACI) designs could be especially useful for understanding basic ecological processes and this knowledge could then be used for the development of sound management strategies of ecologically poorly understood temporary ponds.