Abstract
Sediment samples were collected at low tide from six stations around the coastline of the Saudi Arabian Gulf Island of Tarut on five occasions during 1995 for the study of the marine interstitial ciliate fauna of the Island. Temperature, salinity and pH of the sediments were measured at the time of collection. The interstitial water, total organic matter and the granulometric properties of the sediment samples were analyzed. The interstitial ciliates were identified and enumerated and the seasonal fluctuation in their number of species and desnity throughout the year were discussed. Fifty eight species belonging to 39 genera and 27 families of marine interstitial ciliates were identified, 43 of which represent new records of the fauna of the Arabian Gulf and Saudi Arabia and five of them were present at all collection sites. Loxophyllum pseudosetigerum, Frontonia marina, Protocruzia depressa, Pleuronema coronatum, Diophrys appendiculata and Uronychia setigera were recorded from all sampling stations throughout the year. The ciliate abundance ranged from 170 to 8,500 cells cm(-3) of sediment. The distribution of each species around the island was recorded and compared to those in similar habitats worldwide.