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Deep ocean ecosystems not shielded from global warming impacts

New study says ‘trickle-down’ impacts likely to have profound effect on seafloor organisms 

A Patagonian toothfish, sometimes sold in stores as Chilean sea bass. Photo by Monterey Bay Aquarium Seafood Watch.

Fish dwelling deep in the ocean will also feel the impacts of global warming, according to a new study by scientists with the National Oceanography Centre. Photo by Monterey Bay Aquarium Seafood Watch.

By Summit Voice

FRISCO — Warming ocean temperatures will have a cascading effect reaching even the deepest parts of the ocean, researchers with the UK’s National Oceanography Centre warned in a new paper published in the scientific journal Global Change Biology.

Their study quantifies future losses in deep-sea marine life, finding that marine life on the ocean floor will decline by up to 38 percent in the North Atlantic and by more than 5 per cent globally during the next century.

These changes will be driven by a reduction in the plants and animals that live at the surface of the oceans that feed deep-sea communities. As a result, ecosystem services such as fishing will be threatened.

The researchers used the latest suite of climate models to predict changes in food supply throughout the world oceans. They then applied a relationship between food supply and biomass calculated from a huge global database of marine life.

“There has been some speculation about climate change impacts on the seafloor, but we wanted to try and make numerical projections for these changes and estimate specifically where they would occur,” said lead author Dr. Daniel Jones.

“We were expecting some negative changes around the world, but the extent of changes, particularly in the North Atlantic, were staggering. Globally we are talking about losses of marine life weighing more than every person on the planet put together,” Jones said.

Even two miles down, seafloor organisms will feel the impacts mainly because their food supply in the upper layers of the ocean is expected to dwindle. Deep sea organisms feed on the remains of surface ocean marine life that sink to the seafloor, but nutrient supplies will suffer because of climate impacts such as a slowing of the global ocean circulation, as well as increased separation between water masses — known as stratification — as a result of warmer and rainier weather.

The projected changes in marine life are not consistent across the world, but most areas will experience negative change. Over 80 per cent of all identified key habitats — such as cold-water coral reefs, seamounts and canyons — will suffer losses in total biomass. The analysis also predicts that animals will get smaller. Smaller animals tend to use energy less efficiently, thereby impacting seabed fisheries and exacerbating the effects of the overall declines in available food.

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