In the aphotic zone, there is no photosynthesis, as sunlight is not available to support the growth of phytoplankton. Consequently, the aphotic zone is very low in biological diversity compared to the photic zone. The organisms that live in the aphotic zone are generally adapted to the darkness, cold, and high pressure of their environment.
Here are some specific characteristics of the aphotic zone:
Low light levels: The amount of light reaching the aphotic zone is extremely low, and may be almost completely absent. This means that plants cannot grow in this layer of water.
Cold temperatures: The water in the aphotic zone is very cold, ranging from near freezing to a few degrees above. The lack of sunlight means that there is no surface heating in this zone.
High pressure: The pressure in the aphotic zone is much higher than it is at the surface, this due to the weight of the overlying water.
Despite the absence of sunlight, there can still be pockets of life in the aphotic zone. The most well-known denizens of the aphotic zone are animals such as deep-sea fish, hydrothermal vent organisms, and deep-sea corals. These creatures have adapted to living in total darkness and often use alternative adaptations for locomotion (like echolocation) and to obtain food (like bioluminescence) in such profound water depths.
