Environmental assessment of spatial distribution of zooplankton community in Lake Manzalah, Egypt

Lake Manzalah is the largest of the four Nile Delta lakes in Egypt. It provides more than 50% of the total inland fisheries of the country. During the last two decades the Lake has been exposed to multiple changes mainly due to local human activities. Monthly zooplankton samples were collected during an integrated environmental monitoring program within the MELMARINA Project that extended from July 2003 to September 2004 to study the distribution and occurrence of zooplankton community in Lake Manzalah. Results showed that, the average zooplankton standing crop was 1277 x 103 individuals m-3 . Spring was the most productive season (2127 x 103 individuals m-3 ) representing 41.65% to the total zooplankton counts. Five groups dominated zooplankton community; Rotifera, Copepoda, Ostracoda, Protozoa and Cladocera. The meroplanktonic larvae of Polychaeta, Cirripedia, Mysidacea and Gastropoda as well as free living nematods were rarely recorded. Rotifera contributed 81.89% to the total zooplankton community. They were represented by 38 species belonging to 19 genera dominated by genus Brachionus (86.65% of the total Rotifera) followed by genus Keratella (8.68%). Keratella species has been indicated as an indicator of pollution. Copepoda (including their larval stages) was the second group in order of abundance forming about 14.28% of the total zooplankton counts and represented by seven species. Acanthocyclops americanus was the dominant species. The productivity of Lake Manzalah decreased from 1979 to become highly eutrophic lake during the present study, but with higher production than the other Egyptian lakes. Management is needed to stabilize the Manzalah lake ecosystem in a way that promotes the sustainability of the system.