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COmplex Deep-sea Environments: Mapping habitat heterogeneity As Proxy for biodiversity

Final Report Summary - CODEMAP (COmplex Deep-sea Environments: Mapping habitat heterogeneity As Proxy for biodiversity)

The deep ocean is considered the last frontier on Earth, holding resources such as food, minerals and hydrocarbons that increasingly attract human attention as potential alternatives for dwindling stocks on land. However, the deep sea is poorly understood: many areas are yet to be explored, and new species are still found on a regular basis. This lack of understanding hampers our ability to assess the potential impact of human activities in these waters, and limits our capability to design effective management strategies for future activities. Biodiversity, the main indicator of ecosystem status and functioning, is the key parameter underpinning most ecosystem-based approaches to marine spatial planning and conservation, but is difficult and expensive to measure in deep waters. Traditional methods can only cover very limited areas, or provide information at the wrong spatial resolution. Complex deep-sea environments such as submarine canyons and cold-water coral reefs are particularly challenging in that respect: their steep and irregular terrain limits the use of standard, downward-facing acoustic methods and over-the-side sampling gear.
CODEMAP gathered a multidisciplinary and international team to combine the latest developments in marine robotics with state-of-the-art approaches in the fields of marine geology, geophysics, biology, ecology and spatial statistics in order to tackle these challenges. The aim was to develop robust and objective methodologies to map complex deep-sea environments in 3 dimensions, quantify habitat heterogeneity and to test if that could be used as an approximation of biodiversity.
Deep-diving marine robots were engineered in a way that enabled them to map the shape of the seabed around them, including under overhangs and along vertical cliffs. This involved the installation of echosounders in a sideways-looking configuration, in addition to the more traditional downward mapping, and allowed the team to create true 3D models of submarine canyons. For ultra-high resolution 3D reconstructions, the team adapted photogrammetry techniques, creating 3D models of coral reefs and canyon cliffs from high-definition video records. Given that different robotic vehicles can provide information at different levels of detail, we developed an approach where a series of vehicles was used simultaneously, in a coordinated and ‘nested’ way, observing all the characteristics and processes in a submarine canyon at the scale they occur.
To make data analysis easier and more robust, a number of new approaches were developed. Automated mapping of marine landscapes at a broad scale (entire submarine canyon, for example) was the first step. For more detailed analyses of focus areas, the ‘RSOBIA’ software tool was created, which helps the operator to segment and classify the seafloor into different habitat types. Existing statistical models were expanded and combined into ensembles to create more robust predictions of biodiversity than were possible before. For the quantification of habitat heterogeneity, the team used an index measuring ‘contagion’, and they demonstrated that seafloor heterogeneity indeed has a broad relationship with biodiversity.
Overall, the CODEMAP project has developed a series of innovative tools that can map and quantify the variability in the deep ocean at the scale it occurs. The observations made during the project demonstrate seafloor heterogeneity is high, and that seafloor communities in these complex deep-sea environments are sensitive: recovery from damage is slow. This puts forward a strong argument for the application of the precautionary principle to seafloor management: until sufficient information can be gathered that a human activity will not have substantial impacts on the seafloor community (for example by using the mapping approaches developed through CODEMAP), any developments on the seafloor should be planned with extreme caution.