Hatching from the sediment egg-bank, or aerial dispersing? - the use of mesocosms in assessing rotifer biodiversity

Rotifer emergence from dry billabong sediments was studied from 3 sites on the River Murray floodplain, near Wodonga, northern Victoria, Australia. The sites had different flood histories, ranging from annual to approximately 25-year flooding intervals. Half of each sediment type was sterilized by γ-radiation to contrast the contribution of recruitment from the egg bank with recruitment from passive dispersal. A series of mesocosms was employed to assess differences between treatments, i.e. sediment sterilization and flood history. Analysis by Canonical Correspondence Analysis and Similarity Percentages suggested that some species were passively dispersed. Of the 54 species colonizing after 35 days, four were undescribed, one was a new record to Australia, three species had previously been recorded only from Tasmania and five more were new to the study area. Overall, 22% of species were previously unrecorded from the study area. This suggests that habitat poor mesocosms, may be more successful in locating passively dispersed taxa than examination of natural temporary waters.[PUBLICATION ABSTRACT]