Mesopelagic zone

Definition

The mesopelagic zone is the part of the ocean located between approximately 200 meters and 1,000 meters below the surface. This zone is characterized by a gradual decrease in temperature and light, and it plays a crucial role in the ocean's ecosystem as a transition layer between the well-lit surface waters and the dark depths below. Organisms in this zone are adapted to low light and are important for nutrient cycling and the transfer of energy within marine food webs.

5 Must Know Facts For Your Next Test

1. The mesopelagic zone is often referred to as the twilight zone due to the limited light penetration, making it a unique habitat for various species.
2. This zone is home to many important marine organisms, including lanternfish, squid, and various species of crustaceans that migrate vertically between layers at night.
3. The temperature in the mesopelagic zone can range from about 4°C to 10°C, which affects the distribution and behavior of marine life.
4. The mesopelagic zone serves as a crucial area for carbon cycling, as organisms here consume organic matter from above and contribute to the biological carbon pump.
5. Studies suggest that more than 90% of the ocean's biomass resides in the mesopelagic zone, highlighting its importance in global marine ecosystems.

Review Questions

• How does the mesopelagic zone serve as a transition area between the photic and bathypelagic zones?
  • The mesopelagic zone acts as a crucial transition area between the photic zone, where sunlight supports photosynthesis, and the bathypelagic zone, which is completely dark. In this zone, light diminishes gradually, creating an environment that supports unique adaptations among organisms. These adaptations include bioluminescence and vertical migration patterns that allow species to efficiently feed and evade predators as they move between layers.
• Discuss the role of vertical migration of marine organisms within the mesopelagic zone and its ecological significance.
  • Vertical migration involves many marine organisms moving up to shallower depths at night to feed on phytoplankton and then returning to deeper waters during daylight. This behavior helps link the upper layers of the ocean with deeper habitats by transferring energy and nutrients. This ecological strategy not only influences local food webs but also plays a significant role in nutrient cycling and carbon export from surface waters to deeper ocean layers.
• Evaluate the implications of climate change on the biodiversity and ecological functions of the mesopelagic zone.
  • Climate change poses significant threats to the biodiversity and ecological functions of the mesopelagic zone due to rising ocean temperatures and acidification. Altered temperature gradients can affect species distribution and migration patterns, potentially leading to shifts in community structure. Furthermore, changes in the availability of nutrients from surface waters could disrupt food webs. Understanding these impacts is essential for predicting future changes in marine ecosystems and ensuring their conservation.

Related terms

photic zone:

The upper layer of the ocean where there is enough sunlight for photosynthesis, typically extending to about 200 meters deep.

bathypelagic zone:

The part of the ocean below the mesopelagic zone, ranging from 1,000 meters to about 4,000 meters deep, where complete darkness prevails.

bioluminescence:

The production and emission of light by living organisms, common in deep-sea species found in the mesopelagic and deeper zones.