The primary function of the photic zone in aquatic ecosystems is to support photosynthesis, which is essential for primary production. This top layer of water, typically extending down to about 200 meters, receives sufficient sunlight for phytoplankton, marine plants, and algae to thrive. The productivity of the photic zone underpins the entire food web, supporting a diverse range of aquatic life, including fish and larger marine animals. Healthy photic zones are critical for maintaining marine biodiversity and the overall health of aquatic ecosystems.