Seasonal variation in physico-chemical properties and zooplankton biomass in Greater Zab River -Iraq

Seasonal variation of zooplankton biomass has been carried out at two selected sites on Greater Zab River. Monthly samples of water were collected during period from January to December 2008. Some physico-chemical properties of water were studied including water temperature (from 8 to 30.5 ◦C), hydrogen ion concentration (from 6.3 to 8), EC (from 255 to 821 μs.cm-1), turbidity (10- 85 NTU), dissolved oxygen (from 4.2 to 12.35 mg.l-1), BOD5 (from 0.6 to 24 mg.l-1), COD (from 15 to 294 mg.l-1), ammonium level (from 0.51 to 1.66 μg NH4-N.l-1), nitrite (from 29.1 to 71.3 μg NO2-N.l-1), nitrate (from 112.9 to 327.4 μg NO3-N.l-1), reactive phosphate (from 195.7 to 558 μg PO4-P.l-1) and calcium concentration (from 24.7 to 72 mg.l-1). Concerning planktonic communities, the results showed that the total zooplankton number was ranged from 100 individuals.l-1 to 6650 individuals.l-1 and the total phytoplankton population was 18773 cell.l-1 to 269448 cell.l-1. Statistical analysis showed that there was a positive correlation between total count of zooplankton and total count of phytoplankton during studied period with r = 0.38 in site (1) and r = 0.31 in site (2). However, the results of water quality of Greater Zab River showed that the values of WQI were 66.15% and 64.61% respectively in both studied sites which can be considered as fair according CCME (2001) and medium according EU (1975).