Restoration
ReMEDIES is planning to restore a total of eight hectares of seagrass meadows – four hectares in Plymouth Sound National Marine Park and four hectares in the Solent Maritime Special Area of Conservation. Work on our first planting effort began in summer 2020, when we collected around 800,000 seagrass seeds from healthy meadows off the Cornish coast during a series of collection dives. The seeds were maintained and cared for over the winter at our cultivation facility at the National Marine Aquarium in Plymouth. In spring 2021, a team of volunteers spent time at National Marine Aquarium portioning the seeds into small hessian bags to be distributed on the seabed within Jennycliff Bay in Plymouth Sound.
Around 16,000 seed bags and 2,200 seedling bags were created in total. Over several planting days, these bags were loaded onto the Cattewater Harbour Commissioners’ barge and taken out into the bay.
The bags were dropped down four-metre-long tubes to avoid the propeller wash from the boat, allowing them to drift unhindered down to the seabed. We worked during Neap Tides when there is less tidal movement and the bags would be less affected by the currents as they drifted from the tube to the seabed.
The seed bags are from Bags of Ethics/Supreme creations, made from 100% natural hessian and are fully biodegradable, ethically and sustainable sourced and made.
A team of volunteers packed the seed bags at the National Marine Aquarium Plymouth, placing between 30 and 50 seeds within a small amount of sand in the bags. The seeds grow through the coarse hessian weave of the bags. The bags then break down leaving the seedling in place on the seabed. Seeds should start to germinate within three to four weeks, and we hope to see a flourishing meadow within 12 to 18 months.
Research published in March 2021 suggests that the UK may have lost as much as 92 per cent of its seagrass. Factors including wasting disease, pollution and physical disturbance have been identified as contributing causes. Seagrass meadows provide homes for juvenile fish and protected creatures like seahorses and stalked jellyfish. Seagrass also has an integral role in stabilising the seabed, cleaning the surrounding seawater and capturing and storing significant amounts of carbon.
Advanced Mooring Systems
There have been a number of trials which have evidenced that AMS designs do work and continue to work in UK conditions e.g. Cawsands, Salcombe Harbour, Lundy Island, Isle of Man, Torbay. AMS installations require careful design for local circumstances and different designs may be appropriate for different local conditions. An aim of the ReMEDIES project is to trial designs in more locations to increase the evidence and experience around using these systems more widely in the UK in different conditions. In winter 2020/21 ReMEDIES began trialling the Stirling system (developed by Ocean Conservation Trust) and Seaflex system in the Solent, near Yarmouth Harbour on the Isle of Wight. A double high tide and exposure to harsh weather conditions on the west of the island means a rigorous test for these AMS under the toughest conditions.
AMS don’t necessarily have to be more expensive than traditional moorings – the Stirling mooring design, for example, does not involve any high cost components. The cost of AMS also needs to take into consideration the significantly longer lifespan (if proper maintenance is ensured) compared to traditional moorings. ReMEDIES will be working with harbour authorities to provide funding to install new designs which will be at no extra cost to boaters.
There is no published evidence for this. Evidence does show that the pressures from anchoring and mooring activity such as abrasion and disturbance of the sediment have an impact on seagrass beds. Chronic abrasion results in the presence of ‘scars’- unvegetated patches within the seabed. Seagrass beds have a low resilience and high sensitivity to these types of pressures.
This very much depends on the design and type of advanced mooring system that is being used. Manufacturers report that systems require the same annual maintenance checks as a traditional concrete block and chain mooring. The lifespans of these AMS are also usually longer than a traditional mooring. The aim of the ReMEDIES project is to work closely with harbour authorities and manufacturers to understand and improve experience around the maintenance requirements of different designs.
The opinion of consultees to a study on the potential for eco-moorings as management options for Marine Protected Areas was that an eco-mooring installed by a well-trusted harbour authority may continue to be covered under the existing insurance policy and at the same price though this would be a “material change” that would have to be agreed with the insurance company in each case. One harbour authority in the Solent has already contacted their insurance company to confirm this for the Remedies project trials and it has been confirmed that the moorings are covered in the same way as any other mooring and at no extra cost.
Seagrass impacts
The potential impacts of anchoring on seagrass beds is summarised in Recreational and commercial anchoring and mooring impacts in marine protected areas in Wales and England. Direct studies in the UK are limited but one study in Studland Bay noted that patches that were considered to be anchor scars varied in area between 1-4m2. It was noted that a feature of these patches was a distinct step down (10-20cm) from the seagrass bed along at least one edge, leaving the rhizome mat exposed and undercut. Sidescan images of the same scars before and after winter also indicated expansion of the scars.
In seagrass beds, abrasion from the mooring chain removes leaves and shoots and also the rhizome system. Mooring scars have been observed for Zostera marina around the UK such as in Porth Dinllaen in the Pen Llyn a’r Sarnau Special Area of Conservation, Wales and in the Isles of Scilly. Rocking the Boat: Damage to Eelgrass by Swinging Boat Moorings examined swinging chain boat moorings in seagrass meadows across a range of sites in the UK to determine whether such moorings have a negative impact on the Zostera marina at the local and meadow scale. Evidence was provided from multiple sites that Z. marina is damaged by swinging chain moorings - each swinging chain mooring was found to result in the loss of 122 m2 of seagrass which was significant at a local scale. The scours from traditional moorings can be clearly seen in satellite images e.g. on Google Earth.
We cannot find any evidence of normal detached seagrass shoots reattaching. Zostera marina and Z. noltei do not have vertical rhizomes so may not be able to ‘root themselves into sediment’.
Rhizome elongation and seagrass clonal growth.
Seagrass may be able to disperse via the transport (several km) of reproductive shoots but only specifically with seeds attached. Seagrass rarely seed and to be successful and survive these shoots would have to not be damaged and be transported via specific currents, which allow them to settle in a location suitable for growth. https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/0012-9658(2002)083[3319:LDDPIA]2.0.CO;2
Published scientific journal articles reference articles dating from the 1930’s which document a Zostera bed decline by 90-99% due to wasting disease now known as ‘Labyrinthula zosterae’. A good summary of this is a review of the literature. Natural England carries out site specific condition assessments of the habitats of protected sites based on recent data, surveys and literature. Recent assessments have shown that a number of seagrass beds in our Marine Protected Areas e.g. in Plymouth Sound SAC and Solent Maritime SAC are in unfavourable condition. An assessment in 2016 examined the environmental health of seagrass in the British Isles and provided quantitative evidence that they were mostly in poor condition in comparison with global averages – although some were in good health, all were considered to be at risk from man-made impacts.
In 2012 the Government introduced a Revised Approach to the management of commercially licensed fisheries in European Marine Sites. This ensured all existing and potential commercial fishing activities are subject to an assessment of their impact on the features of designated sites and are appropriately managed to achieve the conservation objectives of the site. Management measures to prevent the impacts of fishing activities on seagrass beds such as trawling have therefore already been implemented by Inshore Fisheries and Conservation Authorities around the country. Impacts from any marine licensable activities or planning activities are also subject to similar assessments to ensure any potential impacts are mitigated or managed to prevent damage to sensitive habitats.
