The Ecology of Two Aquatic Isopods Annina mesopotamica (Ahmed, 1971) and Sphaeroma annandale annandale (Stebbing, 1911) in the Intertidal Zone of the Garmat Ali River, Basrah, Iraq

During the period from January to December 2022, two species of Isopods Annina mesopotamica (Ahmed, 1971) and Sphaeroma annandalei annandalei (Stebbing, 1911) were studied in the intertidal zone of the Garmat Ali River. The current study aimed to assess the density, occurrence and distribution of the two species and their relationship to the surrounding environmental factors. Monthly samples from three fixed stations were collected, using a quadrate with an area of 0.0625m² at each station. The monthly rates of various environmental factors, including temperature, pH, salinity, current speed, light transmittance and DO, as well as the presence of these two species, were evaluated. The population density of S. annandalei reached 192 individuals/m² during May at station 3. The lowest value was 16 individuals/m² recorded during June and October at first two stations and in July at the third station. On the other hand, the highest values for A. mesopotamica reached 144 individuals/m² during May at station 3, no individuals were recorded during Sept. at station 2 and in Aug. and Sept. at station 3. The findings revealed no notable distinction between the linear regression equations for male and female animals, which allowed for their consolidation into a single linear equation for each species. At the three stations an inverse significant correlation was found between salinity, temperature and light transmittance with the numerical density of the two species. Additionally, the pH, DO and current speed had a significant positive correlation with the numerical density.