Reproduction strategy of dominant cladocera species of the Sea of Marmara

In this dissertation study, the reproductive strategies and relations with environmental parameters of zooplankton species belong to Superorder Cladocera which have an important place in the zooplankton community characteristics of the Marmara Sea were investigated. Zooplankton samples were collected monthly between 2004 and 2008 from the upper layer water at DB1 station located in the northeast region. Primary factor, which is effect to abundance of Cladocera species, was found water temperature. Also, chlorophyll a was found the second factor affecting their abundance. Population structure of the species were examined according to their reproductive strategies, and it was determined that the parthenogenetic female individuals that provide rapid exponential reproduction were dominant at 60-100%. Birth rates of Cladocera species were assessed with significant differences in birth rate success between species and years. Increase in the number of embryos during the collapse periods of the populations is among the striking results. However, decreases were recorded in the populations of Cladocera species, which were highly affected by the holoplanktonic Geryoniidae species observed periodically after 2005. Following the mucilage event, which observed between October 2007 and February 2008 in entire Marmara Sea, the group collapsed completely between December 2007 and January 2008. As a conclusion, Cladocera species were sampled from the water column following the collapse was evaluated as having the advantage of the gametogenetic breeding strategy. The changing population structures of Superorder Cladocera species depending on their reproduction strategies in the Sea of Marmara and the role of environmental factors in their reproduction success will be an important contribution for the current knowledge and for the future studies.