Our ability to map the seabed has been greatly enhanced by a suite of technologies. Satellite technology can detect underwater mountains and trenches by measuring bumps and dips on the ocean surface. Sonar technology determines depth by measuring the time it takes for sound to travel between a vessel and the seafloor, and back again, with the ‘strength’ of the echo providing information on whether the substrate is rock or sediment. Light Detection And Ranging (LIDAR) technologies, typically attached to aircraft, use infrared and blue-green pulsed laser beams pointed down towards the sea. Whilst the infrared is reflected off the surface, the blue-green is able to penetrate the water column up to a depth of 30 meters (depending on water clarity). The difference in the time it takes for the two lasers to return back to the aircraft indicates the depth. Submersibles, remotely operated vehicles (ROVs) or autonomous underwater vehicles (AUVs) can be deployed with underwater cameras as well as designed to capture physical samples of the sea bed.
Mapping marine benthic habitats is vital for many different purposes, not least for supporting marine spatial planning and ecosystem based management of the marine environment. Benthic maps also support industrial endeavours such as offshore oil and gas developments, mining, and fisheries management, ensuring safety for mariners by identifying hazards and designing safe shipping channels, for conservation purposes such as designing marine protected areas, identifying critical habitats, and of course improving our knowledge of benthic ecosystems... The full article was published in – and can be read in – The Marine Professional, a publication of the Institute of Marine Engineering, Science & Technology (IMarEST).
Image: Map of ocean floor based on earths gravity field. Credit NASA (Public Domain)