Study of distribution and abundance of meroplankton in the southern Caspian Sea, offshore Anzali

Study of meroplankton structure, abundance variationsanddetermined of bloom them were assessed in different years and seasons in the offshore Anzali, at the 4 stations. The samples have taken seasonal at the 5, 10, 20 and 50 m depth in 1996 and between 2001 and 2013. The fifteen meroplankton groups were identified. In the study, dominant meroplankton were Bivalvia larvae, Balanus improvisus and  Nereis diversicolor. The abundance of Bivalvia larvae increased sharply in 1996, average abundance of Bivalvia larvae was measured about 26000 ind.m-3. There were increased and declined in Balanus improvisus abundance after Mnemiopsis leidyi bloom between 2001 and 2013.The abundance of B. improvises varied from 98 to 4700 ind.m-3 in 2001 and 2010, respectively. In addition, the bloom of B. improvises was recorded amount 3100 ind.m-3 in spring. The abundance of N. diversicolor varied between 60 and 1500 ind.m-3 in 2001 and 2006, respectively. The N. diversicolor did not show before M. leidyi bloom (1996). The seasonal bloom of N. diversicolor was observed amount 500 ind.m-3 in summer. The vectoral distribution of meroplankton was observed at 50 m depth in surface layers. The finding displayed, meroplankton abundance decreased from inshore to off shore. The environmental parameters and exotic species could be important reason in temporal and spatial of meroplankton in the southern Caspian Sea.