DIVERSITY AND SPATIOTEMPORAL VARIATIONS OF ROTIFERA OF THE SAMARRA DAM, IRAQ

This investigation is the first of its kind in this reservoir for more than three decades, it aimed at evaluating the diversity, abundance, and spatiotemporal variations of rotifers in the Samarra dam during 2023. Three distinct sampling stations were selected to ensure a comprehensive coverage of the dam. The first station was located just below the river's entrance to the dam. The second station was situated near the Samarra Barrage, while the third was positioned close to the Tharthar Regulator. Fifty-seven taxa from fourteen families of rotifers were identified, classified into three orders: Ploima, Flosculariaceae, and Bdelloida, under the Eurotatoria class. Most abundant taxa were Synchaeta oblonga Ehrenberg,1832, Rotaria neptunia (Ehreberg,1830), Euchlanis dilatata Ehrenberg, 1832, Polyarthra dolichoptera Idelson,1925, Brachionus calyciflorus Pallas, 1766 (long and short spine), B. urceolaris Müller, 1773, and Keratella cochlearis (Gosse, 1851). Minimum and maximum densities were in winter and spring, respectively. Mean values for richness, evenness and diversity indices were 5.18, 4.75 and 6.37; 0.8, 1.8 and 0.8; 2.2, 1.8 and 2.4 bits/ind. At stations 1, 2 and 3, respectively. Seasonally, the highest and lowest values of evenness and diversity indices were in summer and winter, respectively, while the richness index it was observed in autumn and spring seasons. Also, the highest similarity index value was 68.78% between first and third stations. Whereas the largest difference of species composition observed between second and third stations reached 7.76%.