Effect of AL-Tharthar Canal on the Zooplankton Composition and Diversity in the Tigris River

This study is considered the first in this sector of Tigris River after 2003, to evaluate the effect of Tharthar Canal on the composition and diversity of zooplankton in Tigris River. Six sampling sites were selected; two on the Tharthar canal and four sites along the Tigris River, one before the confluence as a control site and the others downstream the confluence. One hundred thirty-four taxa of zooplankton were recorded in this study, 129 taxa in Tigris River ,76 taxa in Tharthar Canal as well and 96 taxa shared between river and canal. The high value of zooplankton density in Tharthar Canal increased the density of Tigris River from 307989 Ind./m3 in site 1 upstream the confluence to 371427 Ind./m3 in site 4 immediately downstream the confluence. Also, the mean values of richness index, evenness index and diversity index decreased from 7.46, 0.69 and 2.40 bit/Ind. before the confluence to 6.46, 0.61 and 2.08 bit/Ind. after the confluence, respectively. Furthermore, the highest similarity percentage was between sites 1 and 6 reached 84.28% while, the lowest percentage was between sites 1 and 2 reached 65.97%. The highest value for the constancy index was 24 in site 6.