Living Reefs

In 2021, Scotland celebrates the Year of Coasts and Waters, and COAST celebrates 25 years of the community of Arran’s efforts to protect our seas.

Here we bring you a little bit closer to what lies beneath our waves with a focus on the rare Living Reef habitats found in Scotland’s seas.

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If the word ‘reef’ conjures up a vision of warm, tropical seas full of colourful corals and fish, you could be forgiven as this is the sort of reef that we more commonly see on TV and in news stories. It may therefore come as a surprise to learn that we have equally wonderful underwater seabed habitats in the cooler waters around Arran and other parts of Scotland.

These living reefs, or beds, are only made by a few marine animals and plants and are very specialised marine habitats. As with coral reefs, the living organism creates the reef structure, sometimes secreting tubes that combine to form the reef or by binding seabed material together to form a raised structure. Scotland’s living reefs come in a variety of forms, from beds to maerl, flame shells or horse mussels, to those created by horse mussels or the reefs of different worms!

The importance of Living Reefs

Living reefs are some of the most amazing habitats we have in Scotland’s seas; their complex, multi-dimensional structures are just one of the characteristics they possess and is a key reason as to why they provide such an important contribution to biodiversity.

The reefs form a multi-story home for many other plants and animals that can live on and amongst the reef, ultimately meaning these habitats support a greater diversity of life than would be found if they were not present. The cacophony of life living on these reefs is spectacular: seaweeds, sponges, anemones, sea squirts, marine slugs and snails, sea urchins, starfish, octopus, crabs and fish are just some of the more visible species that can be found, with many more cryptic species living within the reef.

Special Species

It’s difficult to pick a specific living reef species to shout about. We’ve already shouted pretty loud about flame shells thanks to the amazing discovery within the South Arran MPA last year.

We’re therefore going to shout about some of the less heard of living reefs. There are recently confirmed records of Ross worm reefs off the Scottish east coast and, off the west coast, spectacular cold-water coral reefs formed by the only reef-forming coral in British Waters, Lophelia pertusa. Most of the Lophelia reefs are found of depths over 200m, but near Barray and Mingulay reefs over 4,000 years old have been found in shallower water above 150m!

Scottish waters are particularly important for horse mussels, hosting 85% of all horse mussel beds in the UK from Shetland and Orkney down the west coast and Outer Hebrides. Known as ‘Clabby Doo’s’ (from the Gaelic, Clabaidh dugha), the largest known largest reef in the UK is at Noss Head in the north east of Scotland. We highly recommend this blog to find out more about them!

Juvenile cod use maerl beds as nursery grounds. Many other species also rely on maerl.

Human Benefits

We are only just starting to understand more about the vital role that our marine habitats have in sequestering carbon from the atmosphere. Living reefs are what we would deem “Blue Carbon” habitats, as they process and store carbon in the living tissues of the marine life they support, and also promote longer term carbon storage in shells and sediment, thus helping us in our fight against climate change.

Living reefs play a significant role in the life cycles of many commercially important species that us as humans consume. Queen scallops are actively attracted to live maerl to lay their spat, and horse mussel beds act as nursery for juvenile common whelk. By providing key nursery habitat, for species such as juvenile cod and haddock, these living reefs help the recovery of stocks further up the food chain which have long since been deemed ‘commercially extinct’.

Scotland’s native oysters are of key economic and environmental importance to us as humans. They significantly improve water quality in areas they are present, and have the ability to remove excess nutrients from the water column – particularly nitrogen which can be the instigator of toxic algal blooms.

Threats to Living Reefs

Scotland’s living reefs encompass the weird and the wonderful. Sadly, many of them are far less extensive than they used to be. They are highly sensitive to physical damage such as from bottom towed fisheries – we all remember the Loch Caron Flame shell reef devastation – and many of the reef builders are slow growing and long-lived, so reef structures take a long time to develop and recover.

Native oyster beds were once a really important fishery in Scotland, however overfishing and an infestation of oyster parasite devastated these beds meaning Loch Ryan is the last natural oyster fishery in Scotland.

Climate change is, probably unsurprisingly, another huge threat to our living reefs. Scotland is the European stronghold for maerl beds, but a recent study predicts that – worst case scenario – we could lose 84% of them by the end of the century if we don’t drastically cut our greenhouse gas emissions. Climate change is driving ocean temperatures upwards as such a pace that this slow-growing species (just 0.2mm a year in Scotland!) simply cannot adapt. Even the best case scenario predicts distribution of maerl beds in Scotland could shrink by 38% come 2100 unless major changes occur, threatening not just maerl but all the flora and fauna that call the habitat home.

Can we protect Living Reefs?

There are a number of projects across Scotland looking at actively restoring oyster beds so we can once again benefit from their ecosystem and biodiversity value, as well as their potential to support sustainable local fisheries. Check out the DEEP ProjectSeawilding and the Wild Oysters Project to find out more.

Marine Protected Areas and other spatial management measures have been used to protect what the Scottish Government deem “Priority Marine Features”. Many of our living reefs are classified as PMF’s and therefore – in theory – should be protected by laws prohibiting unsustainable and destructive fishing methods from damaging them. In reality, many are still at serious risk of being damaged which is why we, along with 89 other groups/organisations as the Our Seas coalition, are calling for a modern Inshore Limit around Scotland, to protect and allow recovery of precious habitats like Living Reefs.

Get involved to make a difference!

Scotland’s seas are home to some of the more unusual but beautiful reefs on our planet. We need to protect our living reefs – they play an extremely valuable role in the wellbeing of our marine ecosystems and as part of the marine food web, in turn supporting businesses such as fisheries and wildlife tourism that rely on a healthy and productive marine environment.

You can help make a difference in the protection and restoration of these amazing ecosystems by getting involved with numerous projects.

Seasearch – if you are a scuba diver, record what you see whilst out in our seas. Data from you feeds into a national database, informing Marine Scotland and the top-level administration that these things are here. This helps inform fisheries management policies.

Support local marine conservation projects in your areaCoastal Communities Network is a good place to start looking to see if there is a group near you.

Attend events to learn more!

Feature image courtesy of Paul Kay