Lakes
Lakes and ponds range in size from tiny temporary pools to the Great Lakes of North America, which contain more than 20% of all freshwater habitats in the world. They range geographically from the equator to above 80° N. Their chemistries vary with the types of terrain in which they are found, and nutrient levels can be low to extremely high. Aquatic plants and macroscopic green algae live along the shallow margins of lakes, and both algae and cyanobacteria are primary producers throughout the photic zone. Zooplankton include small arthropods and rotifers, whereas the nekton is dominated by fish. Turtles and birds also play an important role as grazers and predators in many lakes.