Experiments aid in the restoration of seagrass in Plymouth Sound

Tests in our COAST Laboratory have looked at how seagrass planting units are influenced by hydrodynamic forces
Seagrass The Ocean Conservation Trust and the University of Plymouth have been carrying out experiments in the University’s COAST (Coastal, Ocean and Sediment Transport) Laboratory

Two of the South West’s leading marine organisations have joined forces to enhance seagrass restoration in the Plymouth Sound National Marine Park.

The Ocean Conservation Trust and the University of Plymouth have been carrying out experiments in the University’s COAST (Coastal, Ocean and Sediment Transport) Laboratory to look at how seagrass planting units are influenced by hydrodynamic forces.

The seagrass planting units are made from a cotton layer, with a hessian intertwined mat topped with sand. The experiments are assessing how the planting units cope with shear stress from waves and currents, and how resistant the hessian mats are to these different hydrodynamic conditions.

They have highlighted the physical limitations of the planting units and found the best formation to place the planting units on the seabed, so they protect each other and the seagrass seedlings within from waves and currents, allowing the seagrass to grow.

Armed with this new knowledge, the Ocean Conservation Trust’s Commercial Dive Team will be deploying the planting units in Plymouth Sound, using metal pegs to secure the units into the sediment.

This will form part of their work in restoring seagrass beds as part of the four-year LIFE Recreation ReMEDIES Project, which aims to plant a total of eight hectares of seagrass meadows – four hectares in Plymouth Sound and four hectares in the Solent Maritime Special Area of Conservation.

Dr Rob Schindler (left) carried out the research on seagrass with MSc Applied Marine Science student Lizzy Binks
Dr Rob Schindler (left) carried out the research on seagrass with MSc Applied Marine Science student Lizzy Binks
Dr Rob Schindler , Research Associate within the University’s School of Geography, Earth and Environmental Sciences, has been working on the project with Professor Daniel Conley and MSc Applied Marine Science student Lizzy Binks.

Dr Schindler said:
“The COAST lab provides a means of controlling the wave and currents we would expect on the seabed. Trying to undertake the equivalent at the restoration sites may takes months in order to experience all the flow conditions we have been able to recreate in the lab. Here, we have been able to very rapidly establish the physical limits of the planting units. For instance, the experiments have shown that the planting units are particularly susceptible to wave damage. The findings will help the Trust determine the locations where they can be confident the planting units won’t be damaged and understand how the arrangement of the units can help enhance their survivability, allowing the seagrass plants to become established.”

Mark Parry, Development Officer at the Ocean Conservation Trust, said:

“Seagrasses are one of the most valuable ecosystems on the planet. It’s great that we are able to use the state-of-the-art facilities at the COAST Laboratory to carry out these experiments to aid in our approach to restoration and ensure a healthy future for this important species.”

Seagrass is one of the ocean’s most important habitats, providing a nursery ground for commercial fish stocks and acting as a haven for many marine animals, including rare seahorses. Seagrasses also stabilise sediments and prevent coastal erosion, as well as having the capacity to absorb carbon more efficiently than terrestrial habitats, making it an important player in the fight against climate change.

Despite the importance of these habitats, since the 1930s 90% of Zostera marina seagrass beds have been lost, and they are still in decline. In 2014, the International Union for the Conservation of Nature (IUCN) estimated that seagrasses are still declining by 7% globally, with this estimate making it the fastest disappearing habitat on the planet.

This research has been made possible by the University of Plymouth’s Seale-Hayne Educational Trust and Marine Institute Pump Priming Fund, alongside match funding from the Ocean Conservation Trust.

OCT seagrass research 1
OCT seagrass research 2
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View across Plymouth Sound from Mount Edgcumbe