It’s a vast, frigid abyss, where light rarely penetrates, and oxygen is in short supply. It’s very otherworldliness has helped it seep into cultural awareness through science fiction an horror stories, but for most people the deep sea barely seems like a real place, let alone an important one.
That’s why the news this week that climate change is expected to lead to staggering losses in deep-sea life, may not have seemed nearly as relevant as the traffic report or weather forecast.
Whether or not it’s public knowledge, however, the deep sea is home to thousands of commercially important species and is one of the last frontiers for new species discovery. The creatures of the deep are also key to the cycling of nitrogen, carbon and silicon in the ocean, a process that maintains the delicate balance of ocean life.
An international team of scientists from the UK, Australia, Canada and France have, for the first time, quantified the decline in seafloor life predicted by some of the most recent Intergovernmental Panel on Climate Change’s (IPCC) climate models. They found that globally, about five percent of deep-sea life will be lost over the next century, while up to 38 percent of benthic life will disappear in the North Atlantic.
“I know a five percent loss doesn’t sound like a lot,” said lead author Daniel Jones of the National Oceanography Centre in England, in an interview with Climate Progress. “But when you understand the amount of life that represents, its huge. We are talking about losses of marine life weighing more than every person on the planet put together. That gives you a sense of just how much is down there.”
The research was published online in Global Change Biology.
How does climate change cause such devastation in one of the most remote places on the planet? Unfortunately for deep-sea creatures, which might seem isolated, all of the ocean’s ecosystems are profoundly intertwined. Life on the ocean floor depends on the steady rain of dead marine life from the surface waters. And all marine life ultimately depends on phytoplankton, the microscopic plants that drift in the sunlit surface waters. Phytoplankton are expected to be hit hard by climate change, which is leading to greater stratification of the oceans. When the water column mixes less, because of sharp differences in salinity and temperature at different depths, the key nutrients phytoplankton need to grow stay locked at the bottom of the ocean. Fewer phytoplankton in turn lead to less food on the ocean floor and a sharp reduction in deep-sea life.
Dr. Jones explained that a lot of the most commercially important species found at the bottom of the oceans won’t be missed at grocery stores or on menus.
“A lot of what is harvested from the sea floor actually ends up in fish meal so people aren’t familiar with those species” said Dr. Jones. “But orange roughy, blue ling and scabbard are all fish species that frequently end up on plates.”
Much of what will be lost in the deep sea as less food filters down, however, are species which no one has heard of, because they have yet to be discovered.
“The deep sea is one of the last truly wild places left on Earth, where we never know what we are going to find,” said Dr. Jones. “We don’t even know what we are destroying.”