Home » Seagrass: Vital, Valuable and Vanishing

Seagrass: Vital, Valuable and Vanishing

Anchoring your boat, either for a few hours overnight or for an opportune lunch break, is an elemental part of boating. However, as recreational boaters it is essential to be aware of the protected seabed habitats that lie hidden under the surface of the sea. Understanding why the seabeds are so important and adopting best practice when carrying out boating activities, such as anchoring and mooring, can play a big role in securing the biodiversity future of our seas.

What is seagrass?

Seagrasses form a key habitat of the seabed, they are most at risk from damage and are currently classed as critically endangered species as their habitat is one of the most rapidly declining on earth. The habitat that seagrass provides is essential to the marine ecosystem, it acts as a key breeding, feeding and resting ground for a variety of protected species such as seahorses, cuttlefish, stalked jelly fish, as well as rare seaweeds.

Seagrass beds globally are estimated to store 10-15% of global ocean carbon, helping to keep significant amounts of carbon out of the atmosphere that would otherwise contribute towards climate change. Unlike seaweed, seagrass has its own root system which helps to anchor and stabilise underwater sediment, therefore reducing coastal erosion by playing an important role in buffering coastlines from storms.

Another important role of seagrass is as a nursery ground for fish, providing stock for a fifth of the world’s twenty-five largest fisheries. At least nine commercially important fish species spend juvenile years in seagrass beds, the most abundant of which are plaice, pollock and herring.

Restoration project

The Royal Yachting Association has partnered with Natural England along with other organisations as part of a four year EU LIFE funded project, known as the LIFE Recreation ReMEDIES Project. ReMEDIES stands for Reducing and Mitigating Erosion and Disturbance Impacts affEcting the Seabed.

The project has three key aims:

To improve the condition of at-risk Special Areas of Conservation in five project sites across the South of England;
To reduce the impact and disturbance of recreational activities;
To evaluate the project’s results and share successful methods with projects managing similar habitats under threat across Europe.

Image credit: Paul Kay

What are the challenges?

Seabed habitats such as seagrass are fragile and can easily become damaged if care is not taken when anchoring a boat. Traditional swing moorings are most commonly used in UK waters, these moorings consist of an anchor, chain and a float. A common problem with traditional anchors is the movement of the metal chain between the float and the concrete block on the seafloor. The chains are prone to moving with the tide and in doing so, often scour and abrade the seabed as it pivots around the anchor point. Repetitive damage from anchoring and mooring can result in a significantly lower chance of regrowth of seagrass in that area.

A similar problem can also occur when the base of an anchor is being repositioned and dragged along a seabed, causing an uprooting and degrading of the seagrass bed underneath. Actions such as these can have a strong adverse effect on the longevity and reproduction of seagrass fronds and roots.

How you can help…

As boaters we can have a significant positive effect on seagrass beds just by making minor changes to our boating practices. One example of this is using a designated slipway whenever possible to land and launch your boat. This will avoid the hull, your feet and trailer wheels coming into direct contact with sensitive habitats in shallow waters and along the shoreline.

In order to minimise the impacts that traditional swing moorings can have on seabed habitats Advanced Mooring Systems (AMS) have been designed to have less impact on the seabed. There are various AMS designs that exist, with changes often made to the chain (such as through using an elastic component that does not lie along the seabed) or the anchor (through using for example a helical screw pile component rather than a block).

When anchoring ensure that you deploy your anchor correctly to prevent drag. This can be avoided by using the appropriate length of chain and warp to help reduce scouring of the seabed. If you do feel that your anchor is dragging, raise it and re-anchor. If it continues to drag, choose a different anchorage.

Raising your anchor correctly when leaving is also good boating practice. Firstly, check to see how the boat is lying. If the boat is pulling back away from the anchor, you may need to slowly motor towards the anchor as the crew pulls in the slack and raises the anchor. Good crew communication is essential to avoid overrunning and fouling the prop. Then, bring the anchor and line on-board.

Avoiding shallow waters and being conscious of low tides will help to ensure that your boat avoids coming into contact with or running aground on seabed vegetation – if in doubt, remember to slow down and use extra caution. If you do run into seabed vegetation, stop immediately and lift your engine. You should then paddle away until you are clear of the vegetation. Similarly, if you accidentally run aground on seabed vegetation, simply wait for the tide to lift you off again. You should never use your engine to force your way out as it will damage the habitat and your engine!

One square metre of seagrass can produce (roughly) ten litres of oxygen a day, but to enable them to carry out this important work, seagrass requires clean, well-lit waters in which to grow. Adding a drip tray under your boat’s engine, installing a bilge filter, maintaining your boat’s fuel lines and ensuring that you refuel over 10 metres from the high water mark unless in a bunded area are all easy actions which can prevent water pollution.

Seagrass beds are rapidly declining and are becoming especially scarce in UK waters, but if all water users make a conscious effort to ensure that actions such as anchoring cause as little damage as possible, then there is a chance that we may be able to save this essential habitat.

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