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MAPPING SEAGRASS FOR GREENER OCEANS
Hidden away beneath the waves, meadows of seagrass provide amazing benefits for us and our planet. Seagrass beds help protect coastal areas from flooding and erosion by reducing the energy of waves as they head to shore and holding the sand together. They store and capture carbon, helping to combat climate change. They provide a habitat for marine life including the Spiny Seahorse, one of two species found in UK seas.
The seagrass mapping project, funded by Southampton Geospatial and the Southampton Marine and Maritime Institute (SMMI) and led by Dr Hachem Kassem from the School of Ocean and Earth Science, is using autonomous surface and underwater vessels (ASV/AUV), diver surveys and machine learning to help protect seagrass in the Studland Bay Marine Conservation Zone.
Surveying with autonomous vessels and machine learning
The sheltered conditions of Studland Bay in Dorset, just along the coast from Southampton, make it perfect for sailing. On the plus side, this boosts the local economy – but it also puts the seagrass beds at risk. When boats drop their heavy anchors onto the seabed, they are dragged through the seagrass and cause lasting damage. One proposed solution is the eco-mooring, a small screw which goes into the seabed, tied to a floating buoy at the surface where boats can be secured. Ten of these have been installed on a trial basis, with a proposal to install up to 100 more. The Southampton team set out to provide evidence that they really do prevent damage to the seagrass.
“I assembled a team of experts from my own school, Ocean and Earth Sciences –I’m a coastal engineer – along with marine biologists, geographers and engineers with expertise in autonomous vessels and mapping techniques,” explained Hachem. The project used more traditional surveying techniques, with divers physically counting and measuring seagrass leaves, whilst also setting out to demonstrate the benefits of new technology.
“We used two autonomous vessels,” said Hachem. “The first was a surface vessel called PicoCAT, which sends out sound beams and allows us to construct a 3D image of the seabed, including the distribution of vegetation and the height of the seagrass canopy.
“The second was Smarty200, an underwater vessel which takes hundreds of images of the seabed whilst communicating with GPS. You can stitch the images together and reference them accurately in space thanks to geospatial data.”
‘Semi-supervised’ – that is, human aided –Artificial Intelligence gave a helping hand with analysing the images provided by Smarty200. Given around 10,000 stereo image pairs from a single survey, the algorithm was able to group these into representative clusters showing different types of seabed conditions. A human expert looked at a selection of representative images and labelled the conditions shown, from 100% seagrass cover to lower coverage to bare sand. Assisted by these labels, the algorithm was then able to accurately classify the density of seagrass in each part of the surveyed area.
Geospatial trailblazers
This project, in partnership with the Dorset Coastal Forum and the Studland Bay Marine Partnership, has highlighted the advantage of eco-moorings in protecting seagrass meadows against traditional anchoring. It has thus informed a marine planning application for the next phase of ecomooring installations in the bay. It has also engaged the local community – including a live video link from the University lab in Southampton to Swanage School as part of their Environmental Challenge Day. Year 10 Geography students learnt about the vital role that seagrass plays in supporting the ecosystem at Studland. The work was also featured in the local yachting magazine.
The research was highlighted in the UK Government’s Geospatial Strategy 2030. This aims to unlock the opportunities offered by location data technologies. The strategy document spotlights the University of Southampton as ‘trailblazers in driving research using location data with emerging technologies to bring geospatial data into the forefront of innovation’. The Southampton Geospatial initiative is hailed for bringing together interdisciplinary expertise in computer science, engineering, geography, mathematical sciences, and ocean and earth sciences to address important societal and environmental challenges.
“Nature-based Solutions can help address the climate emergency and biodiversity loss crisis,” concluded Hachem. Protecting seagrass ecosystems and the many benefits they bring to the planet and human society is one such solution – giving hope for greener oceans in the years to come.
