Abyss papped by Autosub
Autosub6000 has undertaken the most detailed photographic survey of the abyssal ocean floor. Some half a million photos will be stitched together to form a ‘street view style’ map of the Porcupine Abyssal Plain and its inhabitants.
Forward and down-facing cameras mounted on the sub have provided continuous images of an area some 12 miles long by 4 miles wide (20km by 7km). This ‘landscape scale’ photo will give scientists a wealth of information about the communities and how they change with the different terrains. Coupled with advanced acoustic mapping, and samples taken of the ocean floor, Henry Ruhl’s team will have a complete picture of what lives at, on and in the ocean floor. Henry said: “The benefit of using Autosub6000 for collecting photos of the seafloor is that it can cover vast stretches of the seabed quickly while collecting a huge number of photos, along with other data about the environment.”
The downward facing camera takes photos directly below Autosub6000. These are used to assess the number and types of invertebrates that live on the seafloor in different areas of the plain. Sea cucumbers are the dominant type of large invertebrates in the abyss, and there are at least ten different varieties in the photos. Autosub6000 takes one photo every 0.8 seconds, and the photos overlap. This overlap means that photos can be stitched together into long strips, giving a continuous picture of the seafloor.
The forward facing camera is used to look at the numbers and distribution of abyssal fish. Fish decline in number rapidly with depth, with only a few species able to survive on the limited food supply in the abyss. The rarity and mobility of fish means that surveys must cover large distances to determine their distributions over the seabed, which is another reason why Autosub is such a valuable tool. Eels and rattails dominate fish species in the abyss. They are typically scavengers that can cover long distances using relatively little energy to try and find food. The forward-facing camera is used to monitor fish because they can be startled and swim away before being seen by the downward facing camera.
While Autosub6000 gathered data, the scientists took mud core samples to find out what is living in the seafloor. The cores confirm variation in sediment type as well as collecting microscopic worms, crustaceans,and bacteria.
In an area of cliffs too steep for Autosub6000, the scientists used SHRIMP (Sea floor High Resolution Imaging Platform) a towed camera system. The SHRIMP system had forward and downward video cameras and a downward facing still camera. SHRIMP has revealed rare rocky outcrops in the abyssal plain in an environment that is largely flat and covered in muddy sediment.
One of the key aims of this research is to find out the effect that climate change has on the deep ocean floor. With no sunlight penetrating these abyssal waters, the animals live on material that falls from the upper ocean, phytoplankton, zooplankton and faecal matter – plankton poo. The settling of this sinking food supply differs in different parts of the abyssal plain including the hills and flat areas. The research will help disentangle how projected changes in this sinking carbon food supply will differ on abyssal hills versus flat areas in the largest habitat on Earth.
Carousel image: Photo strip showing a Dumbo octopus