In the exotic world of the "oxygen minimum zone," about one-half mile below the surface of the ocean, animals are specially adapted to live where the concentration of oxygen is extremely low.
But over the last twenty years, that oxygen level has been getting even lower.
"Everything in the ocean needs to breath oxygen in water just like we breathe in the air, so if oxygen goes down, things suffer or die in extreme cases," Stanford University Hopkins Marine Station biologist William Gilly said.
Gilly says climate change is definitely happening under water and many scientists believe it's linked to climate change above the surface.
"It appears the rate of change is increasing and it's getting more serious as time goes by," Bruce Robison of the Monterey Bay Aquarium Research Institute said.
So scientists and engineers are working together to try to measure the effect of declining oxygen on deep sea animals. They are using a remote control vehicle about the size of a Volkswagen bus that is equipped with a high definition camera and guided from a control room where the team watches for creatures they want to study.
Researchers have learned a lot just by looking at animals in their natural habitat thousands of feet below the surface. A barrel eye has holes above its mouth for breathing and its eyes -- big green balls -- are behind a transparent shield for protection. The eyes rotate to find food hanging in the tentacles of creatures called siphonophores.
"Then it pivots its body upwards, keeping its eyes focused on the food, plucks the food from the tentacles, pivots the body back down and swims along," Robison explained.
For the past four years the team has been developing an instrument called a respirometer to find out how deep sea animals are responding to lower oxygen levels.
"We just came back from a week at sea where we had two deployments of it," Robison said.
The pilot steers the instrument to scoop animals into individual chambers. They can live comfortably inside for a day or two while the device measures their oxygen intake. This allows scientists to study animals without subjecting them to the decompression that happens when they bring them to the surface.
It's too early for definitive results, but scientists already know low oxygen is forcing some creatures to find new habitats and their systems are stressed.
"We could certainly see the impact of declining oxygen on the physiological state of these animals," Robison said.
The low oxygen could have a big impact on the food chain in the ocean. If deep water animals are forced closer to the surface it could be much easier for predators to find and eat them and that could dramatically change the delicate balance of the ocean eco-systems.
Written and produced by Jennifer Olney