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Hull-mounted multibeam systems collect bathymetric data (i.e., information about the topography of the seafloor) over large seabed areas that can be used to undertake a preliminary evaluation of important or potential endangered habitats. More detailed complementary data on these target habitats will be collected by instruments mounted on remotely operated vehicles (ROVs), such as sidescan sonar, high-resolution multibeam systems, and mobile camera systems. Together, these can provide high-resolution mapping information on different species or communities in a specific area.
The acquisition of environmental data is also crucial to establish the environmental baseline of these habitats. This baseline data collection exercise should include the sampling of the uppermost layers of sediment on the seafloor, and near-bottom water sampling. CTD profiles through the entire water column are also an important element to consider for the environmental baseline.
On the iMirabilis2 expedition, the AUV Autosub6000 and ROV Luso will be used to undertake habitat mapping and sampling. The Luso is equipped with a video system that comprises a set of 6 cameras, including an ultra HD 4K camera that is used to record the entire dive. The video system is accompanied by an independent digital still camera that can take 10 Mpx photos with a flash – important in the low light conditions of the deep sea.
The video observations made during each dive will later be used in conjunction with the information from the camera recordings in order to confirm the presence/absence of species and to classify different types of seabed based on local bottom fauna. High-resolution bathymetry will be collected using the new multibeam system mounted on ROV Luso’s frame.
In general, ROVs offer high sampling precision and allow the use of non-destructive data collection methods. The ROV Luso is equipped with two arms with different manipulators. Sampling accuracy is provided by a 7-function arm with a delicate claw, working together with a more multipurpose 5-function arm. This configuration is particularly suitable for sampling the hard rock substrate and delicate benthic fauna specimens.
Additionally, the ROV Luso can collect nine sediment corers (~30 cm long) per dive. Water samples can be stored in four Niskin bottles, and a CTD profiler with extra sensors can provide good characterization of the entire water column, collecting data during the dive down to the seafloor and on the way back to the surface (including temperature, salinity, pressure, oxygen concentration, turbidity, pH, redox potential, fluorescence, CO2 and CH4).
Autosub6000 will contribute to the seafloor mapping dataset with seafloor imagery and multibeam bathymetry data.
By combining data from different sources – bathymetry and other parameters extracted from the multibeam (backscatter data), geological samples (rock and/or sediment), biological and water samples and other environmental parameters – it is possible to extrapolate the information over a wider area of seafloor using predictive mapping techniques.
Written by Monica Albuquerque
In this video tutorial, iAtlantic Fellows Kelsey Archer Barnhill and Bea Vinha explain how video annotations are made during ROV dives using the ocean floor observation protocol.