Seasonal fluctuations of the copepod resting egg bank in the middle Seine estuary, France: Impact on the nauplii recruitment

In order to determine the role of resting eggs in the plankton dynamic of the main calanoid copepods species of the Seine estuary, 30 sediment cores of approx. 10 cm were sampled over one year in the subtidal area of the middle Seine estuary (France). The resting eggs of calanoid copepods were extracted from the 10 surficial cm of sediment, quantified (abundance), and then incubated, either immediately after extraction or after one month at low temperature, in order to determine the hatching success, the type of eggs (quiescent, diapause) and species. Viable resting eggs were found, with total abundances ranging from 0.06 ± 0.05 to 2.33 ± 1.40 × 107 eggs m−3 and higher values in early summer and mid autumn. This study indicated that the production of resting eggs may act in both short-term (continuous emergence, reinforcement of post winter production) and long-term survival (formation of an egg bank) for the key copepod species of the Seine estuary (Acartidae, Eurytemora affinis and Temora longicornis). With a hatching success of 3.5%, 11,644, 710,267 and 52,397 nauplii m−3 month−1 were estimated emerging from surficial sediments respectively for Acartia spp., T. longicornis and E. affinis; demonstrating the significant role of resting eggs in the population dynamic of the main calanoid copepods species in the Seine estuary.