A mobile lab methodically charts deep-sea carbon cycles
Like the robotic rovers Spirit and Opportunity, which wheeled tirelessly across the dusty surface of Mars, a new robot spent most of July traveling across the muddy ocean bottom, about 40 kilometers (25 miles) off the California coast. This robot, the Benthic Rover, has been providing scientists with an entirely new view of life on the deep seafloor. It will also give scientists a way to document the effects of climate change on the deep sea. The Rover is the result of four years of hard work by a team of engineers and scientists led by MBARI project engineer Alana Sherman and marine biologist Ken Smith.
About the size and weight of a small compact car, the Benthic Rover moves very slowly across the seafloor, taking photographs of the animals and sediment in its path. Every three to five meters (10 to 16 feet) the Rover stops and makes a series of measurements on the community of organisms living in the seafloor sediment. These measurements will help scientists understand one of the ongoing mysteries of the ocean—how animals on the deep seafloor find enough food to survive.
Most life in the deep sea feeds on particles of organic debris, known as marine snow, which drift slowly down from the sunlit surface layers of the ocean. But even after decades of research, marine biologists have not been able to figure out how the small amount of nutrition in marine snow can support the large numbers of organisms that live on and in seafloor sediment.
This autonomous system collects high-resolution color images that allow identification of animals to the species level and visual records of significant seafloor features. Using the successful, Dorado-class AUV as its starting point, the Benthic rover is comprised of a high-resolution still camera, two xenon strobe lights, an obstacle-avoidance sonar, an acoustic modem and a navigation sonar. The rover can conduct benthic animal time-series surveys in one third the amount of time it takes to run them with the ROV. The benthic rover will also be used for exploratory investigations in tandem with the mapping AUV.
The rover’s camera fires every 1.6 seconds and produces overlapping images four meters wide that can be merged into one continuous mosaic. The resolution of each image at that altitude is sharp enough to resolve even the tiniest of crab antennae. The light from the twin strobes is carefully controlled to evenly illuminate the seafloor beneath the AUV. The high resolution images and illumination greatly enhance the manual animal identification tasks as well as the accuracy of the computer-based Automated Visual Event Detection system.