Copepods come in first: rapid colonization of new temporary ponds

The sequence in which new colonists reach an empty habitat can be crucial for future development and species structure of communities. It is therefore important to assess species composition and abundance in the initial stages of habitat existence. In the present study we focussed on colonization of newly constructed temporary ponds in Dohana, Southwest Spain, created by removing 30 or 60 cm of top soil. To confirm that no egg-bank was present, we conducted hatching experiments using sediment cores from six new ponds and two reference sites. Hatching was not recorded in the sediment of the new ponds with the exception of two rotifer individuals. In contrast, in the reference sites a maximum of 103 individuals per sample hatched, including cyclopoids, cladocerans, ostracods and rotifers. In the field, water samples were collected from seven ponds after 19 days of their first hydroperiod. Cyclopoid copepods, mostly Metacyclops minutus, had arrived and dominated all sampled ponds. Other taxa were the monogonont rotifer Brachionus plicatilis in four ponds, and the cladoceran Moina brachiata in one pond. The abundance of zooplankton was negatively correlated with conductivity, suggesting that ponds with higher conductivity undergo delayed colonization. We suggest that fast dispersal and dominance of certain cyclopoid copepods during early colonization is related to their ability to store sperm and fast individual development. Given that cyclopoid copepods can survive drought periods in the sediment of temporary ponds, first and early colonization by cyclopoids is likely to have a profound effect on the propagule bank and future plankton communities when the ponds refill.