Zooplankton refers to the weak swimming animals or those which move under the mercy of water current. They occupy a central position in the food chain in the aquatic ecosystems between primary producers and higher consumers. Zoo-plankton plays an important role in a lake's ecosystem and food chain. Unlike algae, or phytoplankton, zoo-planktons are microscopic animals that do not produce their own food.The need for such a book arises from the fact that few previous attempts were made to record zoo-plankton in the North West region of Saudi Arabia. In addition that the region can be considered...