Maerl Beds

What are Maerl Beds?

"Living maerl is a purple-pink hard seaweed that forms spiky underwater ‘carpets’ on the seabed, known as 'maerl beds’. As a type of 'coralline’ algae, maerl deposits lime in its cell walls as it grows, creating a hard, brittle skeleton." - NatureScot

Why are Maerl Beds important?

Maerl Beds are unique underwater habitats. They support a wide variety of marine life, including communities of red seaweeds and invertebrates such as bivalves, urchins, sea cucumbers, anemones and worms. Young scallops, in particular, seek out living maerl beds as nursery areas. Maerl beds also act as a nursery for juvenile fish of many species.

Maerl beds also sequester carbon, which we all know is of great importance to trying to prevent further climate damage.

Why are Maerl Beds at risk?

Maerl beds develop very slowly over centuries and can take years or decades to recover from damage. They can be easily damaged by the physical effects of anchors and moorings. The deposition of fish wastes and surplus feed from aquaculture cages can have a blanketing effect, blocking the light that is necessary for photosynthesis. Chemicals used by the fish farming industry also have detrimental effects on maerl. Due to the slow growth of maerl beds and the rate of recovery following removal being extremely slow, they should be treated as a non-renewable resource.

How are Maerl Beds Protected?

In 2014, Scottish ministers adopted 81 Priority Marine Features (PMFs). These are habitats and species which are considered to be priorities for marine nature conservation in Scottish waters. Maerl beds are a PMF. Specific maerl beds are protected in 11 areas around Scotland in designated Marine Protected Areas (MPAs). Protecting the maerl beds in Veantrow Bay would protect the young of a wide variety of species.

The Orkney Local Biodiversity Action Plan (supported by OIC, SEPA, Nature Scotland and other organisations) mentions that data from Marine Nature Conservation Review surveys (JNCC) indicate that maerl is concentrated in a variety of localities in Orkney waters, including Veantrow Bay.

OIC’s Local Development Plan 12 Coastal Development and Supplementary Guidance Aquaculture requires benthic surveys to be undertaken to identify any presence of PMFs such as maerl beds to inform the location of new aquacultural developments. There are maerl beds in Veantrow Bay and the benthic surveys done by Scottish Sea Farms Ltd (as part of their environmental monitoring) as well as other sources, show that further development in the area should not be permitted.

Where is the Mearl?

Maerl beds cover much of Veantrow Bay but precise data is limited. This map is shows positional data points pulled together from public data, Scottish Sea Farms Ltd's own environmental survey of the area and data from a more recent survey of the area done by researchers from Heriot-Watt University (not yet published, I contacted them directly).

Every point means maerl is definitely present below it. Absence of a point means there is no data for that spot so it is unknown if maerl is present but from talking to people that have looked/surveyed down there, maerl covers much of the bay.

The green triangle in the middle of the map is the position of the current salmon farm in Veantrow Bay. As you can see, there is evidence that the maerl beds come right up to the farm, putting them at risk from salmon farming outputs e.g. faeces, excess food, medicines and other chemicals used by Scottish Sea Farms Ltd.