Impact of hydroperiod on seasonal dynamics in temporary pool cladoceran communities

Abstract

We studied seasonal dynamics in cladoceran communities in relation to changing habitat characteristics and biotic interactions in 18 temporary freshwater pools in Kiskunsag (Hungary), with an inundation period varying from less than ten weeks (short) to 10-13 weeks (medium long) and more than 16 weeks (long). Pools were sampled for cladocerans and macroinvertebrates and habitat characteristics were monitored starting two weeks after snow melt (end of March 2005) until July. Analysis of early-season dynamics (March-April), when all three hydroperiod classes were represented, did not reveal differences in cladoceran communities recolonizing pools with a different hydroperiod. Species turnover later in the season (May - July) resulted in the association of some species with the medium and long hydroperiod class. Cumulative species richness increased with hydroperiod length from an average of ten species in short hydroperiod to 15 species in long hydroperiod pools. The longer time available most likely allowed more species to gradually occupy available niches in pools with a longer hydroperiod. With time, feeding and growth conditions became more favorable for predominantly small and/or plant-associated species, while the absence of large Daphnia may have been due to predation risk. A decline of pools with a long inundation cycle, through drainage and/or climate change, may adversely affect cladoceran communities and needs particular attention in the conservation of temporary pools and their inhabitants.