Spatial and seasonal variability of the planktonic ciliates assemblages along the Eastern Mediterranean Coast (Sfax coast, Tunisia)

Abstract

In the present study we investigated the effects of restoration (northern coast) and anthropization (southern coast) on the spatial and seasonal distribution of ciliates communities in relation to environmental factors in coastal Sfax area. The low pH value was attributed to anthropogenic waste inputs around the southern coast. The nutrients concentrations, recorded in the southern coast, were higher than those recorded in the northern coast. Analyses demonstrated that ciliates communities’ structures showed significant differences between the northern and southern parts of the sampling coast (F = 6.54, df = 12, p < 0.001). Ciliates diversity was significantly more important in the southern coast (65 taxa) than in the northern coast (40 taxa). The ciliates abundance was 6.33 ×102±3.38× 102 cells L−1 in northern stations. The abundance of ciliates was high over the whole southern coast (12.12×102±3.78× 102 cells L−1), which increased during summer (27 × 102 cells L−1at station 1), and decreased during the spring (3 × 102 cells L−1at station 3). Tintinnids abundance was higher than naked ciliates abundance reported for all seasons, both in the north and south Sfax coast. Some tintinnids species, like Tintinnopsis beroidea, Tintinnopsis nana and Tintinnopsis parvula attained important abundance in the southern area, because they are able to survive under adverse conditions owing to its adaptive strategies. Tintinnidium balechi was a dominant and common species, with high occurrence and represented an important contributor to the ciliate communities. Pearson’s correlation coefficients showed that the seasonal ciliates variations were significantly correlated with nutrients (total nitrogen with tintinnids and orthophosphate plus total phosphate with naked ciliates).