What is the term for the layer of the ocean where light penetration is sufficient for photosynthesis?

The euphotic zone is the correct term for the layer of the ocean where light penetration is sufficient for photosynthesis to occur. This zone is typically found in the upper part of the ocean, roughly extending from the surface down to about 200 meters (656 feet), though the exact depth may vary depending on water clarity. In this zone, sunlight penetrates deep enough to support photosynthetic organisms, such as phytoplankton, which serve as the foundation of the marine food web.

The other zones mentioned are classified differently based on depth and light availability. The profundal zone refers to the deeper parts of a body of water where sunlight does not reach, and therefore, photosynthesis is not possible. The bathypelagic zone lies below the euphotic and mesopelagic zones and extends to about 4,000 meters (13,123 feet), characterized by total darkness and lack of light for photosynthesis. The hadal zone is the deepest part of the ocean, encompassing depths greater than 6,000 meters (19,685 feet), and similarly, it does not support photosynthesis due to the absence of light. Thus, the euphotic zone is specifically defined by its ability to support photosynthetic life, making it