Species diversity, spatial distribution pattern, and temporal succession of Chaetognaths assemblages in north coastal waters of Bushehr- Persian Gulf

Chaetognaths (arrow worms) are strong predaceous mesozooplankton; which feed on other more abundant zooplankton’s groups; their most important preys are Copepods and Appendicularians. So they are considered as one of the most important groups among mesozooplankton communities, especially in the pelagic food web, also widely distributed in the neritic zone of all the oceans. Considering the fisheries activities and ecological aspects of economically and traditionally important ecosystems of the northern coastline of Bushehr, this study aimed to identify, introduce and assess the temporal and spatial distribution patterns of the Chaetognaths in the Persian Gulf, restricted to coastal waters of this area. Chaetognaths were collected during seven sampling programs, from Frake river-estuary, three sites of large creek-estuary of the Shif, one site in the sea, and one site in the Lashkari creek-estuary, at the middle and last day of each season. During all surveys, the depth of the sampling location, Secchi depth, water temperature, pH, and salinity were measured. Finally, 4 species were identified, Flaccisagitta enflata, Aidanosagitta neglecta, Aidanosagitta regularis, and Zonosagitta pulchra, with relative abundances of 56.56%, 29.42%, 11.25% and 2.87% respectively. The highest total density was observed in the sea station at the cold season, for two species of F. enflata and A. regularis. A. neglecta and Z. pulchra reached to the highest density in coastal stations and shif creek at summer. Based on dbRDA (distance based Redundancy Analysis), the depth of sampling location explained effectively the distribution pattern of F. enflata and A. regularis, with a positive correlation,   but salinity demonstrated a negative effect. Also based on the results of dbRDA, depth of the habitat is the most important factor which explains negatively the distribution pattern of A.neglecta and temperature was the correlated factor with the distribution pattern of Z. pulchra in our study area.