A new, non-invasive method to measure and monitor seagrass biomass on the seabed around England’s South West coast is being developed as part of an ongoing, collaborative project.
The innovative technique is being trialled by HydroSurv and Valeport, working with the University of Plymouth and Natural England, and supported by a grant of more than £266,000 (€320,000) from Innovate UK’s Smart Grants programme.
It builds on the concept of the acoustic reflectivity of seagrass providing valuable information to characterise submerged aquatic vegetation. A full-stack solution consisting of a Valeport VA500 altimeter installed onto a HydroSurv REAV-28 Uncrewed Surface Vessel (USV), specifically developed for this project, provides a non-invasive, cost-effective platform to survey seagrass sites.
A large, validated signal library and deep learning algorithm, developed by the University of Plymouth, deciphers the survey data to predict seagrass distribution. The data is visualised and interpreted within a cloud application created by HydroSurv.
The USV platform facilitates accurate repeat surveys that can be compared to monitor temporal changes in seagrass coverage for the planning of protection and regeneration projects at biodiversity-rich worksites. The full solution, which was demonstrated successfully to project stakeholders for the first time in May this year, is set to change the way seagrass meadows are monitored in the future, complementing traditional diver surveys to cover much larger areas and enable rapid re-survey work as required.
Versatile 2.8m package
Launched in 2021, Hydrosurv’s REAV-28 aims to offer open water performance in a versatile 2.8m package. The USV is proving a popular choice for hydrographic, oceanographic and environmental data acquisition within inland navigation, ports and harbours or nearshore coastal worksites.
Built out of marine-grade aluminium alloy, the REAV-28 has proven stability and buoyancy combined with excellent seakeeping characteristics, which aim it squarely towards survey contractors and coastal scientists.
With twin Torqeedo Ultralight 1103 electric outboards, the REAV-28 may be configured with either two or four 915Wh propulsion batteries providing full dayworks endurance. The autopilot system supports steering in combined vectoring and rudder modes. It also provides monitoring of the outboard motor and battery status by integrating directly with Torqeedo’s TQ-Bus, providing alarms to notify operators when the batteries are low. A separate 1,280Wh general service battery offers uninterrupted power to the embedded survey PC and command, control and communications equipment.
Live monitoring and visualisation of the mission and sensor data quality control is performed from NaviSuite Kuda on a separate base control station PC. For docking, or when otherwise needed, it is possible to take control of the USV using a radio-controlled joystick.
Fiona Crouch, Natural England ReMEDIES Project Manager, said: “To effectively conserve and restore seagrass meadows we need innovative solutions to enable cost effective, repeatable surveys of established meadows, plus areas being restored through projects such as ReMEDIES, to monitor change. I’m really excited to see where this new technology will take us in supporting our seagrass conservation efforts.”
Emerging cluster
HydroSurv, Valeport and the University of Plymouth form part of a fast-emerging Southwest England maritime innovation cluster. The project partners are engaging with the Environment Agency and Natural England to develop the solution further, with a second phase of demonstrations planned for September.
Dr Tim Scott, Associate Professor of Ocean Exploration at the University of Plymouth, said: “When combined with the advantages of lightweight autonomous survey platforms, this new combined survey solution introduces a step-change in accurate and repeatable seagrass mapping.”
The UK has lost around half of its seagrass since the mid-1930s due to factors ranging from seagrass wasting disease (SWD) and pollution to physical disturbance from the anchoring, launching and mooring of leisure boats. The £2.5 million LIFE Recreation ReMEDIES partnership ‘Save Our Seabed’, led by Natural England and funded by the EU LIFE Programme, was launched in July 2019 to protect and restore these sensitive habitats.
Seagrass meadows are a crucial part of the marine ecosystem and are increasingly being recognised for their essential carbon capture abilities. As well as being as effective at storing carbon as woodland, seagrass also provides vital habitat for young fish, seahorses and jellyfish. It also cleans surrounding seawater and helps to stabilise the seabed, thereby reducing coastal erosion.
