Seasonal variations in species composition, abundance and biomass of tintinnids (Protozoa: Ciliata) were investigated in the Western Harbour, seasonally during 2012. There were remarkable seasonal variations in environmental parameters, phytoplankton concentrations and abundance and biomass of tintinnids: highest in spring and lowest in autumn. Annual average abundance and biomass of tintinnids were 8.435 ind. l(-1) and 3.725 μg C l(-1), respectively. A total of 29 species of tintinnids belonging to 11 genera was identified. Of which, Tintinnopsis was the most abundant genus in terms of number of species (9), but Favella was the best quantitatively (89% of the total tintinnids). The overall mean abundance and biomass were highest (mean 24.415 ind. l(-1) and 10.355 μg C l(-1), respectively) during spring than the remaining seasons. Due to significant positive relationship between the total biomass of tintinnids and phytoplankton concentrations, food supply is not a problem for tintinnids harbouring in the Western Harbour. Hence, predation loss by meso- and macrozooplankton might be the possible reasons for the estimated low biomass of tintinnids in the present study. Some of the seasonal environmental factors as water salinity, nitrite, dissolved oxygen and pH values exert an influence on the species composition, abundance and biomass of tintinnids.

On its route from the Mediterranean in the north to the Red Sea in the south, the Suez Canal crosses three different lakes which represent different habitats, and in some cases, hinder the migration of the fauna and flora from one sea to the other. Tintinnid species–specific abundance was determined at monthly intervals from 10 stations in the Suez Canal. A total of 18 species were recorded in the canal water, all Indo-Pacific in origin. Six of these species have been introduced to the Mediterranean, while 11 are new geographical records for the Suez Canal. Most species exhibited a seasonal cycle with low winter and high spring and summer densities. Tintinnid affinities and differences between the eastern Mediterranean and the Red Sea were discussed in the light of the results of distribution studies of the eighteen species of Tintinnid carried out over a complete year. These observations point to the role of the canal as a selective barrier and/or as a link in the migration of Tintinnid protozoa. While cases of migration from one sea to the other are more likely to occur in either direction, those concerning species of Indo-Pacific origin are more successful and numerous. Meanwhile, the Suez Canal acts as a local endemic habitat by itself.