The Primary Production Conditions of Wadi Al-Arab Dam (Reservoir), Jordan

The purpose of this study was to investigate the effect of the primary production of phytoplankton on water quality of Wadi Al-Arab Dam Reservoir in Northern Jordan. Species successive change and composition in addition to increased rain inflow and nutrient loading seems to be the major factors behind fluctuation of total chlorophyll a (chl a) content which, was positively correlated with the phytoplankton primary production (r = 0.63-0.68, P 0.05). The major phytoplankton species that contribute to the increase in the primary production were green algae and dinoflagellates. Below water surface, a gradual decrease in chl a concentration was observed with a lowest concentration (3.61 mg/L) being recorded at 10 m during August. Phytoplankton primary production followed a bimodel trend with two clear peaks, the first was in the wet season (March) and the second in summer (September). Total cell counts (mean count = 4040-4636 × 103 ± 1645 cells /L) showed higher values all over the year as attributed to the trophic status of the reservoir with diatoms being the highest proportion of the total counts. Phytoplankton production was significantly correlated with dissolved oxygen concentration (r = 0.76 ، P 0.05). However, surface water temperature, pH and electrical conductivity found to be negatively correlated with production (r = - 0.51, P 0.05; r = - 0.09, P 0.05 and r = - 0.24, P 0.05, respectively). Salinity and total alkalinity on the other hand, did not appear to have any particular influence on phytoplankton production.