The ocean is divided up into three different zones, the euphotic (sunlit zone), disphotic (twilight zone), and aphotic zones (midnight zone). These three zones harbor different types of creatures. You can find more of your normal fish in the sunlit zone, for example, clownfish, and you’ll find more bioluminescent creatures the deeper you go.
Euphotic Zone – 0m – 200m
The euphotic zone is the layer closer to the surface that receives enough light for photosynthesis to occur. The depth of this zone depends on the murkiness of the water. In clear water, the sunlit zone can be quite deep, but in murky water, it can be only 50ft deep. The temperature of this zone ranges from 27 to 104 degrees Fahrenheit.
Disphotic Zone – 200m – 800m
Also known as the Mesopelagic zone, this life zone is the midwater range and is noted for very low levels of sunlight and virtual darkness for human eyes. This layer ranges from 200 meters to about 800 meters down. The plankton, which occupies the sunlight layer in profusion and provides a food source for most of the creatures living in that layer, either directly or indirectly, does not live in the twilight zone. Plankton needs adequate sunlight to thrive. The type of foods available to creatures living at these depths tend to be energy-poor and usually are characterized by detritus and bacteria, the things that drift down from the sunny creatures teeming and thriving at the surface. Most of the sea creatures living in this layer have low-energy tissues and sluggish lifestyles to cope with low food energy since no algae can grow. Life here is noticeably sparse, the deeper you go.
Aphotic Zone – 800m – 2000m
The deepest, darkest regions of the ocean are found from about 2000 meters down to the seafloor. It is a realm of perpetual darkness, where even the faintest blue tendrils of sunlight cannot penetrate. It has been called the “Midnight Zone” because it is continually plunged in utter blackness, even when the brightest summer sun is perched high above the surface, there is no “daytime” here. Life that exists in the midnight zone relies indirectly on the benefits of sunlight; organisms thriving in the sunny upper layers of the sea die their eventual deaths and rain down upon the sea floor a steady flow of organic nutrients to feed the masses living at or near the bottom.