Mysteries of Cape Canyon seafloor habitats explored
A TEAM of researchers from the Department of Environmental Affairs (DEA) has returned from a four-week expedition with the first visuals of the rocky habitats of the Cape Canyon seafloor.
The team aimed to document and explore some of the uncharted areas of the largest-known submarine canyon off the South African west coast – the Cape Canyon.
The team of experts returned from their trip aboard the R/V Algoa, after covering an area of more than 100x300km2, where information on the biodiversity, oceanography and geology of the canyon was collected.
Among other successes, the team returned with the first visuals of the rocky habitats of the canyon seafloor.
South Africa boasts a spectacular number of canyons on land as well as a notable number of underwater canyons.
Such underwater features are reported to potentially play a significant ecological role in the life history of some commercial resources, including hake, and their unique structure connects the coastline to the deep-sea environment.
Apart from their ecological functions, intensified upwelling events have been noted in submarine canyons and these in turn may power cetacean and seabird feeding grounds.
The DEA’s Oceans and Coast branch initiated a three-year collaborative project to provide insights on the functionality of the Cape Canyon in relation to near-shore and offshore areas.
The survey design undertaken followed an array of ship-based sampling methods, including a tow-camera system that takes images and videos of the seabed; a bottom sampler collecting sediment from the seafloor; a dredge which collects invertebrate animal samples from above the seabed; and a conductivity temperature depth (CTD) device package that records information on conductivity, temperature and salinity, and collects water samples to analyse environmental variables at different depths throughout the water column.
An acoustic device which releases sound at varying rates was used to produce a map outlining the topography of the canyon.
Cetacean and seabird observers also participated and provided information on the distribution and abundance of the different species recorded within the canyon.
These datasets, collected between 2016 and 2018, will collectively provide insight in characterising the area and complement South Africa’s marine spatial planning efforts.