Species composition, diversity and distribution of Gelatinous Zooplankton (Cnidaria, Cetenophora and Thaliacea) from coastal/estuarine waters, North of Bushehr- Persian Gulf

 Gelatinous zooplanktons are unknown, mysterious and widely distributed; they are known as key components of ocean ecosystems. In the past two decades, blooms have been observed in some parts of the world under the influence of various factors, including human activities, intensification of the eutrophication, climate changes, and increasing fishing activities, but some other studies did not achieve to severe and unusual blooms. Currently, there is no information about community structure and factors affecting the distribution pattern of gelatinous zooplankton in Iranian marine water bodies, therefore, in this research, the identification, spatial distribution and temporal succession of their different groups (Cnidaria, Cetenophora, Thaliacea) from northern surface-coastal waters of Bushehr were surveyed.

 In this survey, gelatinous zooplankton fauna from the northern coastal/estuarine waters of Bushehr were analyzed during summer of 2017 to spring 2018. Also, in each sampling, the water depth of the sampling site, Secchi depth, pH, and salinity were measured.

5 species of gelatinous zooplankton including three species from hydromedusae Eutima gegenbaueri, Eirene viridula and Clytia discoida, one species of salp Diphyes chamissonis and one combed species Pleurobrachia pileus were identified and reported for the first time from the Persian Gulf. Also, the density of Pleurobrachia pileus reached 3411 ind.m-3 at its blooming (end of September) and was introduced as the dominant species of gelatinous zooplankton in the region.

Based on results of the Multivariate MDS analysis on physical parameters comprising water temperature, dissolved Oxygen, salinity, Secchi depth, depth of sampling stations and Chla, a twice-yearly passage/seasons (two-season time differentiation pattern)  was detected in the region and based on PCO test, only Frake creek-estuary was differentiated from other studied stations. The results of CAP test on Gelatinous Zooplankton assemblages of the coastal and estuarine waters of Bushehr, two stations of Shif Creek- estuary  and Sea station, showed a different and discriminated dispersion pattern, Eutima gegenbaueri, Elrene viridula and Diphyes chamissonis  were determined as indicator species of Sea waters/station, and Pleurobrachia pileus  were identified as indicator/ discriminating species of Shif Creek- estuary. Finally, the results of SIMPER from BEST/BIOENV analysis proved that the dispersion of all identified species were affected by the depth of sampling station, salinity and temperature as the most important factors.