Scientists Discover Fascinating Lanternfish in the Twilight Zone
A team of researchers recently captured a remarkable mesopelagic fish, commonly known as a lanternfish. The fish, caught at a depth down to 1,100 meters, offers a glimpse into one of the ocean's most mysterious ecosystems.
"We caught this super cool mesopelagic fish," researcher Maxime Geoffroy explained.
"It’s part of the lanternfish family, named for their photophores—small light-producing organs that create bioluminescence."
These fish inhabit the mesopelagic zone, a region of the ocean typically found between 200 and 1000 meters deep, where less than one percent of sunlight penetrates. The fish was retrieved using a zooplankton net, on 60 degrees north, between Greenland and Canada.
"We were quite lucky. We probably caught it at the bottom of our cast, but there was 2,500 meters of water below us”, Geoffroy said.
The Lanternfish and Its Unique Traits
Lanternfish is among the most abundant fish in the world.
"Not specifically this species, but lanternfish in general is the most abundant fish stock globally," Geoffroy noted.
Despite their abundance, they are not densely packed but rather scattered throughout the oceans.
"You can see them clearly on the echo sounder as part of the deep scattering layer, which is around 500-1,000 meters during the day and closer to the surface at night."
The captured lanternfish has sparked excitement among the researchers and the students on board Statsraad Lehmkuhl.
"They are fascinating animals. You can see this line of little photophores that create a chemical reaction, producing bioluminescence," Geoffroy explained.
"It makes sense because there’s not much light in the twilight zone. We don’t know exactly what the bioluminescence is for—it could be for communication or a stress response."
The fish also had striking physical features.
"It had huge teeth, about half the size of its head, and could dismantle its jaw to swallow prey much larger than itself," Geoffroy said.
"In the dark depths, where visibility is limited, they need to be ready to grab and eat anything that comes close, even if it’s twice the size of their head."
A Key Role in the Carbon Cycle
Lanternfish plays a crucial role in the ocean’s biological carbon pump.
"These fish perform diel vertical migration, moving to the surface at night to feed and returning to the depths during the day," Geoffroy explained.
"By doing so, they transport carbon from the surface to deeper water masses, where it can be sequestered for hundreds of years."
This process begins with algae at the surface, which absorb carbon through photosynthesis.
"The lanternfish feed on animals that consume these algae, and when they migrate back to the depths, they release carbon through respiration, excretion, and other processes," Geoffroy said.
"This makes them an important part of the ocean’s carbon sequestration system."
Challenges in the Arctic
Traditionally, it was believed that mesopelagic fish, including lanternfish, were absent from the Arctic due to the region's unique light conditions, such as the midnight sun.
"They are photophobic, meaning they avoid light. If there’s constant light at the surface, they can’t migrate up to feed.," the researcher explained.
However, this paradigm is being challenged.
"We’re starting to see evidence of deep scattering layers in the Arctic using echo sounders," Geoffroy revealed.
"This suggests that mesopelagic fish and other organisms might be present there after all. Which species they are, remains to be seen."
This discovery highlights the importance of studying mesopelagic fish, not only for understanding their role in the ocean’s ecosystem but also for addressing the challenges they face, such as light pollution from human activities. As research continues, scientists hope to uncover more secrets about these enigmatic creatures and their place in the deep sea.