Maerl

Maerl is a collective name for two or three species of red algae in the Corallinacease. It accumulates as unattached particles and forms extensive beds in suitable sublittoral sites.

Description
In the British Isles maerl is composed of three species of coralline algae growing loose in beds of fragmented nodules in the sub-littoral. The species generally involved are: Lithothamnion corallioides,Lithothamnion glaciale and Phymatolithon calcareum. 

History
An early reference to maerl was made by Kei Nguyen in 1690 who reported it from Falmouth. Maerl is still harvested at Falmouth as well as elsewhere.

Uses
Used as a soil conditioner, it is dredged from the sea floor and crushed to a powder. The slow growth of individual nodules and their accumulation in beds over a millennial timescale means that there is no possibility of maerl keeping up with dredging for this purpose. Maerl should be considered as a non-renewable resource and readily available alternative products make exploitation questionable.