‘Maerl is a collective term for several species of calcified red seaweed. It grows as unattached nodules on the seabed, and can form extensive beds in favourable conditions. Maerl is slow-growing, but over long periods its dead calcareous skeleton can accumulate into deep deposits (an important habitat in its own right), overlain by a thin layer of pink, living Maerl.’
‘Maerl is of commercial value as a soil conditioner on acidic ground, as an animal food additive, for the filtration of acid drinking water and in pharmaceutical and cosmetic products. In 1978 a licence was issued by the Crown Estate Commissioners (CEC) to dredge 30,000 tonnes per year of dead Maerl from the Fal Estuary. The area dredged avoids the live Maerl of the St Mawes Bank.’
Extracts from the UK Biodiversity Action Plan.
The St Mawes Bank
The eastern bank of the Carrick Roads is the area described above as the ‘St Mawes Bank’. At the top of the bank in less than 12m, is where the Maerl beds are.
Swimming over the beds you see loads of different creatures, in, on or buried within it. There are so many it would be boring to list them all, but in the main there are a lot of crabs, Velvet Swimming Crabs, Harbour Crabs, Hermit Crabs and Decorator Crabs. There are also several different types of anemones and Tube Worms all living within the Maerl Beds. Compared to most photographic dives, this area is very different, a nice change.
The St Mawes Bank is the most well known of the Maerl beds in the area. There are other beds, including one in the Percuil River, off Pendennis and in the Helford River. The water quality is so good around Falmouth that live Maerl can be found as deep as 20m or more. Outside of the areas listed above, the sites would be listed as having a light covering, rather than a bed of Maerl.
We have extensively dived all the Maerl beds and can help you find what you are looking for.