What is the defining characteristic of the photic zone in an ocean biome?

The defining characteristic of the photic zone in an ocean biome is that it is closest to the sun and supports phytoplankton. This layer is typically up to about 200 meters deep in the ocean and receives sufficient sunlight to enable photosynthesis, which is vital for the growth of phytoplankton—tiny, photosynthetic organisms that form the base of the marine food web. The presence of light in this zone allows for a rich and diverse ecosystem, as phytoplankton produce not only oxygen but also serve as a primary food source for many marine organisms, including small fish and zooplankton.

In contrast, the other options describe characteristics of different oceanic zones or conditions. The deepest part of the ocean is the abyssal zone, which is located far below the photic zone and does not receive sunlight. The absence of photosynthetic life is a trait of the aphotic zone, where light does not penetrate enough to support photosynthesis. Extreme pressure and temperature are conditions typical of the deep ocean, also below the photic zone, rather than the illuminated layers where life thrives due to sunlight. Therefore, the photic zone’s unique feature is its capacity to support photosynthesis due to the presence of sunlight, allowing for a