An international study led by the Institute of Environmental Science and Technology of the Autonomous University of Barcelona (ICTA-UAB) indicates that the decrease in oxygen in the oceans threatens the survival of deep water fish and the health of the oceans themselves.
The conclusions of this study were published in the Journal Communications Earth & Environment, and suggest that “the progressive decrease in oxygen levels in the oceans is intensifying due to climate change.”
This significantly affects marine ecosystems, including populations of Mesopelagic fish and, in addition, it can alter marine trophic networks, fishing, ocean health and their ability to store carbon.
This phenomenon can have serious repercussions on sea food chains, global fisheries, and in the balance of oceanic ecosystems.
The study analyzed how marine ecosystems reacted to deoxygenation episodes occurred in the past and, to carry it out, the researchers studied fossils of flashlight fish, one of the most abundant and important species of the deep ocean.
These fossils are more than 10,000 years old and were preserved in marine sediments of the Eastern Mediterranean.
Lantern fish are very small fish of deep waters of the Myctophidae family, named for their ability to produce light by bioluminescent organs.
Despite their small size, lantern fish are extremely abundant in the global ocean, with a biomass estimated at 600 million tons, which possibly makes them the most abundant vertebrates of the planet if the weight is taken as a measure.
During the day the lantern fish live in the dark Mesopelagic area (between 200 and 1,000 meters deep) to hide from predators, while at night they swim towards the surface of the ocean to feed on zooplankton.
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An important role in climate regulation for ocean oxygen
Due to both their great biomass and their daily vertical migration, the lantern fish play a very important role in climate regulation and oceanic food networks, because they connect the surface with the deep ocean.
Therefore, lantern fish are widely considered as a good group indicator of the Mesopegic ecosystem.
The fossils analyzed show that these species disappeared almost completely during the periods in which the ocean oxygen fell to very low levels, and only reappeared (and in large quantities) when the oxygenation of the sea was restored, about 6,000 years ago.
The team conducted by the study includes researchers from the UAB, of the Institution of Oceanography and Woods Hole Oceanographic Institution of the US, Sinica Academia de Taiwan, the McGill University of Canada, the Free University of Berlin and the University of Heidelberg of Germany.
The researchers used the so -called otolites (fish -ear structures) to track how marine populations changed over time.
The impact of marine deoxygenation
The sediments of the Eastern Mediterranean, a region that alternated high and low oxygenation phases, allowed to clearly observe the impact of these events on marine biodiversity.
The main researcher of the study, Sven Pallacks, explains that “the case of lantern fish is a clear example of what can happen on a large scale if marine deoxygenation continues.”
“If these so abundant species may disappear, many others are also at risk,” warns the researcher.
The Twilight Zone – the Mesopelagic Zone, located between 200 and 1,000 meters deep – plays a fundamental role in the climate system of the Earth, mainly due to its influence on the global carbon cycle.
The results suggest that Mesopelagic ecosystems are especially vulnerable to oxygen loss.
Its collapse could destabilize the ecological balances of the ocean, reduce the capacity of the sea to absorb CO2 and endanger the food security provided by oceanic fisheries.
With EFE information
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