Final answer:
The photic zone of a lake with little flow, low salt concentration, and high oxygen concentration has a large variety of organisms due to the availability of light and nutrients. Phytoplankton serve as the base of the food web in this zone.
Step-by-step explanation:
The photic zone of a lake with little flow, low salt concentration, and high oxygen concentration has a large variety of organisms because of the availability of light and nutrients. Light can penetrate within the photic zone, allowing photosynthetic organisms like phytoplankton to thrive. These phytoplankton serve as the base of the food web, providing food for zooplankton and other organisms. The high oxygen concentration also supports a diverse range of organisms that require oxygen for survival.