The Twilight Zone, also known as the mesopelagic zone, refers to an oceanic layer of water that stretches around the globe. Beginning at 200 meters below the surface and ending at 1,000 meters down, not much is known about this mysterious reservoir.
However, recent studies have revealed a shocking revelation: the Twilight Zone is severely iron-deficient, which drastically limits bacterial growth. To survive in these conditions, researchers have found that these bacteria produce specialized molecules called siderophores that help them scavenge trace amounts of iron from the water.
This discovery offers groundbreaking insights into the ocean’s role in carbon absorption– a critical process for regulating Earth's climate. In the face of a climate crisis, understanding how bacteria in the deep ocean contribute to carbon storage could have significant implications for tackling this global challenge.
Bacteria and Siderophores: The Fight for Iron
Iron is essential for several biological processes, including respiration, DNA synthesis, and metabolism. For this reason, bacteria must constantly acquire iron from their environment to survive. However, as previously mentioned, iron levels in the Twilight Zone are extremely low. To adapt to these harsh conditions, bacteria in this region have evolved specialized mechanisms over time.
One such adaptation is the production of siderophores— which are specialized compounds that bind to iron with high affinity, as can be seen in the diagram below.
Now, once a siderophore captures iron, the bacteria absorbs the siderophore-iron complex– bringing the iron into their cells where it is used for essential functions like respiration and DNA synthesis. This adaptation enables bacteria to survive and thrive in the Twilight Zone, despite the limited availability of iron.
Contribution to the ‘Biological Carbon Pump’
Tim Conway, an associate professor of chemical oceanography at the USF College of Marine Science, emphasizes the significance of these findings as follows:
“Understanding the organisms that facilitate carbon uptake in the ocean is important for understanding the impacts of climate change. When organic matter from the surface ocean descends to the deep ocean, it acts as a biological pump that removes carbon from the atmosphere and stores it in seawater and sediments. Measuring the rates and processes that influence this pump gives us insight into how and where the ocean stores carbon.”
Siderophores, though primarily involved in iron acquisition, play an indirect yet vital role in the biological carbon pump. By allowing bacteria in the Twilight Zone to survive in iron-deficient waters, siderophores enable these bacteria to break down sinking organic matter— releasing some of the carbon back into the water. While part of this carbon is recycled into the ocean's ecosystem, much of it continues sinking into deeper waters, where it can be stored for long periods.
As Conway explains, this process is a key part of the biological carbon pump, which helps remove carbon from the atmosphere and store it in the deep ocean. By supporting bacterial activity through siderophore production, these microbes indirectly aid in regulating carbon levels, contributing to the fight against climate change
Implications for Climate Change Research
Understanding the role that bacteria and other organisms in the ocean play in regulating Earth's climate is more crucial than ever. As research on the twilight zone and microbial processes like siderophore production continues to unfold, it becomes clear that the ocean is a vital component in the fight against climate change– but it must not stop there. By further exploring how the ocean absorbs and stores carbon, we can develop better strategies to protect our planet's climate system, ensuring a sustainable future for generations to come.
Reference list
EurekAlert! (2024). New study: Deep-sea discovery shines light on life in the twilight zone. [online] Available at: https://www.eurekalert.org/news-releases/1058870 [Accessed 2 Oct. 2024].
Interesting Engineering (2024). Photos: Deep sea bacteria use clever tricks to scavenge iron in twilight zone. [online] Interesting Engineering. Available at: https://interestingengineering.com/photo-story/twilight-zone-iron-deficiency-ocean-bacteria [Accessed 2 Oct. 2024].
Ribeiro, M. and Simões, M. (2019). Advances in the antimicrobial and therapeutic potential of siderophores. Environmental Chemistry Letters, 17(4), pp.1485–1494. doi:https://doi.org/10.1007/s10311-019-00887-9.
Us-ocb.org. (2024). Carbon sequestration by the biological pump is not exclusive to the deep ocean :: Ocean Carbon & Biogeochemistry. [online] Available at: https://www.us-ocb.org/bp-sequestration-above-deep-ocean/ [Accessed 2 Oct. 2024].
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