Reproductive strategies and population characteristics of key Cladocera species in the Sea of Marmara

Zooplankton is an essential component of marine ecosystems, with Copepoda and Cladocera being the most important zooplankton groups in all the world’s seas. In the Sea of Marmara, Cladocera has the highest participation in zooplankton abundance. Here we investigated reproductive strategies and population characteristics of four Cladocera species; Penilia avirostris, Pleopis polyphemoides, Evadne nordmanni, and Pseudoevadne tergestina in the Sea of Marmara, northeastern part of Mediterranean Sea. Reproduction strategy, fecundity, and embryonic development of four Cladocera species were achieved. During our study period from 2004 to 2008, there was an extreme jellyfish bloom caused by Liriope tetraphylla and following mucilage event occurred between the years 2006 and 2008. Thus, we also compared the change in phenology and reproductive strategy of cladocerans amongst periods characterized by extreme events and against a suite of environmental parameters. The most dominant Cladocera species in the Sea of Marmara were Penilia avirostris and Pleopis polyphemoides. The population structures of Cladocera species according to their reproductive strategies, parthenogenetic female individuals provided rapid exponential reproduction, and were dominant at 60%–100%. Parthenogenetic fecundity success was found significantly different among Cladocera species. The most remarkable result during the study period was observation of increase in embryo production while populations were in decrease.