Invasive red swamp crayfish (Procarnbarus clarkii) and native noble crayfish (Astacus astacus) similarly reduce oligochaetes, epipelic algae, and meiofauna biomass: a microcosm study

Human activities have led to the decline of native crayfish and promoted dispersion of invasive species in European freshwater ecosystems. Crayfish are well-known predators of benthic macroinvertebrates, but benthic communities in aquatic ecosystems also include an abundant and functionally important meiofaunal component. For these organisms, the effects of invasive and native crayfish species are poorly understood. In this study, the effects of predation by the invasive red swamp crayfish (Procambarus clarkii) and the native noble crayfish (Astacus astacus) on the density, biomass, and secondary production of meiofaunal assemblages were compared in a model ecosystem experiment. Both crayfish species reduced the overall density of oligochaetes; the biomasses of total meiofauna, oligochaetes, and microcrustaceans; and secondary production by total meiofauna and oligochaetes. Nematodes and rotifers were unaffected by either crayfish species. An analysis of the gut contents of P. clarkii and A. astacus indicated a high degree of omnivory, including the frequent consumption of meiofaunal organisms. Thus, at least for these 2 species, the effects of an invasive vs a native crayfish on meiofaunal assemblages, including their structure, did not differ markedly.