Deep sea life cannot escape global warming

The temperatures of the deep ocean may be warming at a slower pace, but a new study suggests that climate change will have a stronger impact on life in the deep sea. 

An international team of researchers led by the University of Queensland has found that animals in the deep ocean are more vulnerable to climate warming and will find it increasingly difficult to maintain their preferred thermal habitats.

The scientists analyzed future patterns of climate velocity, or the rate and direction that the climate will shift, across the deepest layers of the ocean below 1,000 meters. 

Climate velocity measures the speed at which species will have to migrate in order to remain in a suitable environment. By analyzing climate change velocity, the researchers can examine how deep sea creatures will respond to warming waters and estimate species extinction risks.

The study revealed that despite faster surface warming, the global average climate velocities in the depths of the ocean have been two to four times as fast as the surface velocities for decades. 

According to the study authors, the greater thermal homogeneity of the deep ocean environment is responsible for the larger climate velocities. 

Furthermore, even though climate change velocities are projected to slow down under certain emissions scenarios, the rate of shifting habitats will continue to accelerate in the deep ocean.

Study co-author Jorge Garcia Molinos is a climate ecologist at the Hokkaido University Arctic Research Center.

“Our results suggest that deep sea biodiversity is likely to be at greater risk because they are adapted to much more stable thermal environments,” said Molinos.

“The acceleration of climate velocity for the deep ocean is consistent through all tested greenhouse gas concentration scenarios. This provides strong motivation to consider the future impacts of ocean warming to deep ocean biodiversity, which remains worryingly understudied.”

By the end of this century, climate velocities in the mesopelagic ocean layer are projected to be between four and 11 times higher than current velocities at the surface. 

The mesopelagic layer contains a great abundance of small fish that support larger animals, including tuna and squid. If predators and their prey do not follow similar range shifts in this layer, it could present major challenges for commercial fisheries.

The researchers caution that while uncertainty of the results increases with depth, life in the deep ocean is also limited by many factors other than temperature, such as oxygen concentrations. 

“Without knowing if and how well deep ocean species can adapt to these changes, we recommend to follow a precautionary approach that limits the negative effects from other human activities such as deep-sea mining and fishing, as well as planning for climate-smart networks of large Marine Protected Areas for the deeper ocean,” said Molinos.

The study is published in the journal Nature Climate Change.

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By Chrissy Sexton, Earth.com Staff Writer