Development of cladoceran egg banks in new and isolated pools

The development of cladoceran egg banks was monitored in new and isolated freshwater pools during their first year of existence. Sediment samples of 24 newly created pools were collected six months and one year after creation, and screened for dormant eggs of cladocerans. The build-up of the egg bank was compared with the patterns in the corresponding active community as presented in LOUETTE T DE MEESTER (2005). In all but one of the pools, a cladoceran egg bank started to build up within the first year. Up to 104 dormant eggs were found per square meter (average: 1,710 eggs/m(2)), mainly originating from Daphnia species, Chydorus sphaericus and Simocephalus vetulus. The production of extensive dormant egg banks in the first year after colonization may have substantial consequences, both for the ecology and the evolution of the recently founded populations. Yet, our results suggest that the direct numerical impact of spring-time hatching on the dynamics of active populations is likely to be limited in the young pools.