摘要：Problem statement: Al-Khadoud spring is one of the most important water resources in Al- Hassa Governorate, Saudi Arabia. However, much of its biotic information is still unknown. This study presented preliminary ecological information of this aquatic body. The aim of this research was to study the water characteristics and the planktonic organisms inhibiting Al-Khadoud spring and its irrigational channels for a period of 1 year. Approach: A regular visit was monitoring the spring over a period of 1 year (June 2007 to may 2008). Physico-chemical characteristics of spring water were determined. Quantitative and qualitative analysis of Plankton (Phytoplankton or zooplankton) were also investigated. Results: All the water quality variables measured showed considerable seasonal variation. The data of this study showed that there were marked seasonal differences in the quantitative and qualitative composition of the phytoplankton communities in Al-Khadoud spring and its irrigation canal. The changes in total algal counts throughout the investigation coincided closely with in Chlorophyceae abundance. Thirty six species were identified allover the period of the investigation. Out of these, 9 species belong to Chlorophyceae, 17 belong to Bacillariophyceae, 7 to Cyanophyceae and 3 to Euglenophyceae. Cyclotella meneghiniana Kützing, Nitzschia closterium Ehernberg, Fragilaria capucina Desmazieres, Surirella ovalis Breb, Actinastrum sp., Chlorella vulgaris Beyerinck, Scenedesmus quadriquda Breb, Oscillatoria sp. and Oscillatoria subbrevis Schmidle were observed in a high rank of occurrence. The phytoplankton crop showed a remarkable increase as compared with the previous records. The data showed that the zooplanktonic fauna identified in this aquatic body is a typical of the permanent freshwater and brackish water. Eleven species were recorded, 5 belonged to Cladoceran, 4 belonged to Rotifera and 2 belonged to Chironomid. Zooplankton species like Thermocyclops hyalinus , Mesocyclops sp., Moina micrura , Brachionus caudatus , B. falcatus and Filina longiseta were recorded at all sites investigated allover the study period. The scarcity of zooplankton species from Al-Khadoud spring and its irrigation canal could be due to the nature of these reservoirs as both receiving reuse-drainage and treated sewage water. Conclusion: These results indicated that after receiving water from the outlets either treated sewage water or of re-use drainage water, the spring water had an obvious increase in electrical conductivity, COD, total alkalinity, nitrates, phosphorus, chloride and potassium. These features indicated pollution with organic wastes, increased salinity and deteriorated oxygenated state. Based on this we can say that all these factors can be affected both soil and plants cultivated in the area of Al-Hassa.
