The poor diversity of the zooplankton community and of copepods appears to be a characteristic feature of several small basins on the Egyptian Mediterranean coast, particularly those receiving land-based effluents (e.g. Abdel-Aziz & Dorgham 2002, Abdel-Aziz 2004). The number of

zooplankton species recorded DZNeP purchase during the present study (42 taxa including larval stages) is slightly higher than that recorded (37 taxa) by Abou-Zeid (1990) and El-Serehy et al. (2001). This may be because their studies did not take into account the western lagoon connected with the lake, or the continuous dredging activities in the main lake and shipping lane, which renew the lake’s water masses. In general, the low number of species recorded in the lake can be attributed to the continuous discharge of wastewater, which leads to increasing nutrient concentrations and hence the dominance of just a few

species. This was confirmed by Ludsin et al. (2001) and Prepas & Charette (2003), who concluded that the biodiversity of most aquatic systems decreases with increasing nutrient load as a result of increasing eutrophication. During the study period, the zooplankton standing crop in Lake Timsah showed an annual average zooplankton of 22 026 individuals m−3. This average is comparable with the study of Abou-Zeid (1990) in the lake (23 419 individuals m−3), even though his vertical samples did not cover the whole lake. Also, this value indicated that the lake is less productive than Lake Buroullus (183 000 individuals m−3) during 1987 (Aboul-Ezz ioxilan 1995), http://www.selleckchem.com/products/AZD2281(Olaparib).html Lake Maryout with approximately 117 000 individuals m−3 during 1996–1997 (Abdel-Aziz & Aboul-Ezz 2004), Lake Idku with 326 000 individuals m−3 during 2000 (Aboul-Ezz & Soliman 2000) and Lake Manzalah with 5 × 106 individuals m−3 (El-Sherif et al. 1994).

The seasonal pattern of the zooplankton standing crop was characterized by conspicuously high numbers in summer and a lower peak in autumn, with minimum densities being recorded in winter. Copepods were by far the most important group of zooplankton in the study area, comprising 77.7% of the total population, and the seasonal variation in the total zooplankton population was governed mostly by variations in this group. This dominance of copepods was documented previously in the same area (Abou-Zeid 1990, Ghobasy et al. 1992), in the Suez Canal area (El-Serehy et al. 2001), in the eastern Mediterranean (e.g. Nour El-Din 1987, Dowidar 1988) and at other coastal sites of the Arabian Gulf (Yamazi 1974, Michel et al. 1986, Dorgham & Hussein 1997). The Pearson correlation revealed that temperature and pH were the common factors controlling copepod abundance in the Lake Timsah (r = 0.617 and 0.541 respectively). This is in agreement with Goldman & Horne (1983) and Rodriguez et al. (1995), who found that temperature was the main factor affecting zooplankton production.