Twilight Zone in the ocean

Source: This post on Twilight Zone in the ocean has been created based on the article “Visitors from the Ocean’s Twilight Zone” published in Indian Express on 18th October 2024.

Why in news?

Recent evidence suggests that there are more animals in Twilight Zone of the ocean by weight than in all of the world’s fisheries combined.

About Twilight Zone in the ocean

1. The Twilight Zone in the ocean is a fascinating layer of the marine environment that lies between the Epipelagic Zone (sunlit surface waters) and the Bathypelagic Zone (deeper, darker waters). It is also known as Mesopelagic Zone .

2. It extends from approximately 200 meters to 1,000 meters below the ocean’s surface. In this zone, sunlight is minimal and insufficient for photosynthesis, creating a dimly lit, shadowy realm, hence the name “twilight.”

Characteristics of the Twilight Zone

1. Light Penetration: Very little sunlight reaches the Twilight Zone, which gradually diminishes as depth increases. While it is not completely dark, the low light levels make it impossible for photosynthetic organisms to survive.

2. Temperature and Pressure: Temperatures in the Twilight Zone are significantly cooler than at the surface, often ranging from 4°C to 20°C. Pressure increases drastically with depth, which plays a role in the adaptation of organisms living here.

3. Oxygen Levels: The oxygen concentration in this zone is relatively low, especially at deeper levels, creating a challenge for marine life that must adapt to low-oxygen environments.

4. Marine Life: Despite the low light and harsh conditions, the Twilight Zone is home to a wide array of organisms.

Many species, including lanternfish, bristle mouths, squids, jellyfish, and zooplankton have evolved to survive in this environment.

Some animals are bioluminescent, producing light through chemical reactions in their bodies. This ability is crucial for communication, predation, and camouflage in the dim light of the Twilight Zone.

5. Diel Vertical Migration: One of the most remarkable phenomena in the Twilight Zone is the diel vertical migration, where vast numbers of creatures travel from the depths to the surface at night to feed, returning to the Twilight Zone by day to avoid predators.

6. Role in the Carbon Cycle: The Twilight Zone plays a crucial role in the global carbon cycle. Marine organisms, particularly zooplankton and small fish, feed on phytoplankton from the surface waters and transport carbon to deeper layers of the ocean when they excrete waste or die and sink.

Importance and Research:

1. The Twilight Zone is increasingly recognized for its importance in marine ecosystems and climate regulation.

2. Scientists are keen to understand how it functions as a carbon sink, helping mitigate the effects of climate change.

However, it is also under pressure from deep-sea fishing and climate change, making its preservation a growing concern for marine biologists.

UPSC Syllabus: Geography in news, Environment