We have joined forces with another leading marine organisation to enhance seagrass restoration in the Plymouth Sound National Marine Park.

We are delighted to have partnered with the University of Plymouth, and we 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, as pictured below. 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.

Photo credit: Alan Stewart, University of Plymouth

The experiments are highlighting the physical limitations of the planting units and they have trialled the best formation to place the planting units on the seabed, so they protect each other and the seagrass seedlings from waves and currents, allowing the seagrass to grow.

Armed with this knowledge, our Commercial Dive Team have deployed the planting units in Plymouth Sound, using metal pegs to secure the units into the sediment. This will form part of our work restoring seagrass beds in 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.

The COAST Laboratory 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 take 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 Ocean Conservation 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.

Dr Rob Schindler, Research Associate within the University’s School of Geography, Earth and Environmental Science
Photo credit: Alan Stewart, University of Plymouth

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.

Mark Parry, Development Officer at the Ocean Conservation Trust

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