There are two main sources of oxygen to the photic zone: atmospheric mixing and photosynthesis. Unlike the profundal zone, the limnetic zone is the layer that receives sufficient sunlight, allowing for photosynthesis.[1] For this reason, it is often simply referred to as the photic zone. The limnetic zone is the most photosynthetically-active zone of a lake since it is the primary habitat for planktonic species.[2] Because phytoplankton populations are densest here, it is the zone most heavily responsible for oxygen production within the aquatic ecosystem.[2]