What triggers Acartia species egg production in a Mediterranean lagoon?

Environmental conditions triggering egg production and hatching success of copepod species are essential to better understand their population dynamics and consequently their contributions to the production of higher trophic levels. A monitoring station was sampled during 2 years in the Thau lagoon (Mediterranean Sea) to study temporal successions of 3 Acartia congeneric species (Acartia clausi, Acartia discaudata and Paracartia grani). Seasonal patterns defined the dominance of one Acartia species over the two others. There were two perennial species A. clausi and A. discaudata with maximum abundance in winter and in spring, respectively. The third species P. grani occurred in summer and was absent from the water column from February to April. Egg production and hatching success experiments were conducted at each sampling date to determine the different reproductive strategies of the Acartia species. Maximum egg productions (∼25–31 eggs fem−1 d−1) and mean hatching success (∼65%) were similar between species but occurred at different periods depending on environmental triggers. Model averaging based on field data showed that temperature prevailed over other variables and that Acartia responses were different regarding the species. Temperature was the main trigger for egg production of A. clausi (negative effect) whereas temperature and salinity should be considered jointly to predict A. discaudata egg production. P. grani egg production described an uni-modal relationship with temperature. The effect of temperature on hatching success explained strongly the three species dynamics, especially the production of P. grani resting eggs.