عنوان مقاله [English]
Variety and frequency of Ascidians were studied seasonally (during four seasons through 2010-2011) in five different transects around the Khark Island. In each transect three stations were sampled in high-tide, mid-tide and low-tide, at each sampling period, environmental factors such as temperature, salinity and total organic maters (TOM) were measured. In this study only one species (Pyura vittata) was indentified in the area. This species was only observed in spring (2 in a square meter) and fall (1 in square meter) and in midtide level in the northern part of the Khark Island. Pyura vittata unlike other species of Ascidiacea has more strength and capability to environmental changes, physical conditions and pollution compare to other Ascidiacea species. The main reason for reducing the density and diversity of Ascidiacea is this region, probably is oil pollution.