Saving seagrass in Plymouth

Widely-used, traditional boat moorings have been found to damage large areas of seagrass, sometimes leaving a 'halo' 5m in circumference. The chains which run from the buoy on the surface to a concrete or metal block on the seabed become slack at low tide, meaning the chain rests on the seabed. As the wind and tide change, the chain is dragged along the seabed, causing destruction in its wake and uprooting valuable seagrass meadows at the same time.

The seagrass project in Plymouth worked to install new mooring systems which lift the chain off the seabed using buoys. The chain is attached to a corkscrew-like mechanism on the seafloor to further reduce potential damage.

Why are we protecting seagrass?

Seagrass and rich sediment inshore seabeds can lock in huge amounts of carbon. Not only that, seagrass also stabilises the sand around exposed coasts, protecting beaches from erosion. They are important nursery grounds for cuttlefish, feeding grounds for bass, crab and snails and they strip the water column of excess nutrients.

In order to make a real difference to the recovery of carbon storage habitats like seagrass beds, we need to repair the ones we have, and grow new beds. We also need the recreational boating community to demand a change to mooring systems that don’t damage the seafloor. We need to make as many boaters as possible aware of the implications of anchoring on seagrass beds to avoid unwanted damage.

We worked alongside Natural England, The Ocean Conservation Trust, The Royal Yachting Association, Plymouth City Council and Tamar Estuaries Consultative Forum as part of the ‘ReMEDIES’ (Reducing and Mitigating Erosion and Disturbance Impacts affEcting the seabed) project to achieve these goals.

For our part in the ReMEDIES project, we raised awareness of seagrass conservation issues through our Sea Champion network and online training and events. The wider ReMEDIES project is tasked with replanting and protecting up to 8 ha of seagrass in five English south coast Marine Protected Areas by the end of 2023.

After four and a half years of monitoring the seabed around the moorings, we've recorded at 212% increase in the density of seagrass (May 2023 dive surveys). We believe that a natural recruitment event has occurred, with the necessary conditions for growth of new seagrass likely to have been helped by our introduction of Advanced Moorings.

We've written a report about the ecological findings, taken on board the opinions of key boat users in the research, and introduced the findings at a local workshop which was held in Cawsand on November 7th 2023. You can read more on the Save Our Seas website.