Difference Between Photic and Aphotic Zone

The key difference between photic and aphotic zone is that the photic zone is the portion of the ocean that receives sunlight while the aphotic zone is the portion of the ocean that does not receive sunlight.

The ocean is the largest aquatic biome that can be categorized into different zones. Photic zone and aphotic zone are two oceanic zones categorized vertically based on the penetration of light. Photic zone receives sunlight, and this portion of the ocean extends from the surface of the ocean to 200 m deep. In contrast, the aphotic zone does not receive sunlight, and this portion extends from 200 m deep to the bottom of the sea.

CONTENTS

1. Overview and Key Difference
2. What is Photic Zone
3. What is Aphotic Zone
4. Similarities Between Photic and Aphotic Zone
5. Side by Side Comparison – Photic vs Aphotic Zone in Tabular Form
6. Summary

What is Photic Zone?

Photic zone, as its name implies, receives sunlight. Sunlight penetrates the photic zone, enabling photosynthesis. The photic zone extends from the surface to a depth about 200m. Therefore, photosynthetic organisms, mainly phytoplankton, can survive in this zone. Since they are the primary producers of marine food webs, most of the other marine organisms come and visit the photic zone at least once for food.

The photic zone is more favourable for life than the aphotic zone. Therefore, the diversity of organisms is high in the photoic zone. Moreover, the number of organisms in the photic zone is high compared to the aphotic zone.

What is Aphotic Zone?

The aphotic zone is the portion of the ocean that does not receive sunlight. Sunlight does not penetrate this zone. This zone extends from 200m in the deep of the ocean to the bottom of the ocean vertically.

Since this zone does not receive sunlight, photosynthetic organisms cannot survive in this zone. Moreover, this zone has a low temperature and high water pressure, unlike the photic zone. Hence, the diversity of organisms is low, and a few numbers of organisms live in this zone.

What are the Similarities Between Photic and Aphotic Zone?

• Photic and aphotic zones are two zones in an oceanic environment based on the presence and absence of light.
• They are vertically categorized zones.

What is the Difference Between Photic and Aphotic Zone?

The photic zone is the vertical zone of the ocean that receives sunlight. Meanwhile, the aphotic zone is the portion of the ocean that does not receive sunlight. So, this is the key difference between photic and aphotic zone. Furthermore, the photic zone extends up to 200m from the surface of the ocean, while the aphotic zone extends from 200m to the bottom of the ocean. Therefore, this is also a significant difference between photic and aphotic zone.

Moreover, photosynthetic organisms live in the photic zone while the aphotic zone does not allow photosynthesis due to the absence of light.

Below infographic shows more details on the difference between photic and aphotic zone.

Summary – Photic vs Aphotic Zone

Photic zone and aphotic zone are two vertical zones of the ocean categorizes based on the presence and absence of light. That is; the sunlight penetrates the photic zone, so it is the portion of the ocean that receives sunlight. In contrast, sunlight does not penetrate the aphotic zone. It is the darkness layer. Because of that, the photic zone allows photosynthesis while the aphotic zone prevents photosynthesis. Therefore, photosynthetic organisms live in the photic zone, and this zone is rich in biodiversity compared to the aphotic zone. So, this is the summary of the difference between photic and aphotic zone.

Reference:

1. Fisher, Matthew R. “Environmental Biology.” 3.4 Aquatic Biomes | Environmental Biology, Available here.

Image Courtesy:

1. “Sea Fish Underwater Free Picture” (CC0) Needpix.com
2. “Oceanic divisions” By Chris huh(Original text : K. Aainsqatsi) / K. Aainsqatsi – self-made(Original text : self-made) (Public Domain) via Commons Wikimedia