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Maerl
 
 
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Maerl is a collective name for two or three species
Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring....
 of red algae
Red algae

The red algae are one of the oldest groups of eukaryotic algae, and also one of the largest, with about 5,000?6,000 species  of mostly multicellular, ocean algae, including many notable seaweeds....
 in the Corallinacease. It accumulates as unattached particles and forms extensive beds in suitable sublittoral sites.

he British Isles
British Isles

The British Isles are a group of islands off the northwest coast of continental Europe that include Great Britain and Ireland, and numerous smaller islands....
 maerl is composed of three species of coralline algae
Coralline algae

Coralline algae are red algae in the Family Corallinaceae of the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls....
 growing loose in beds of fragmented nodules in the sub-littoral. The species generally involved are: Lithothamnion corallioides,Lithothamnion glaciale and Phymatolithon calcareum.

Maerl is dredged from the sea floor and crushed to form a powder.






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Maerl is a collective name for two or three species
Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring....
 of red algae
Red algae

The red algae are one of the oldest groups of eukaryotic algae, and also one of the largest, with about 5,000?6,000 species  of mostly multicellular, ocean algae, including many notable seaweeds....
 in the Corallinacease. It accumulates as unattached particles and forms extensive beds in suitable sublittoral sites.

Description

In the British Isles
British Isles

The British Isles are a group of islands off the northwest coast of continental Europe that include Great Britain and Ireland, and numerous smaller islands....
 maerl is composed of three species of coralline algae
Coralline algae

Coralline algae are red algae in the Family Corallinaceae of the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls....
 growing loose in beds of fragmented nodules in the sub-littoral. The species generally involved are: Lithothamnion corallioides,Lithothamnion glaciale and Phymatolithon calcareum.

Maerl is dredged from the sea floor and crushed to form a powder. It is still harvested around the coasts of Brittany
Brittany

Brittany is a former independent Celtic nations monarchy and duchy, now incorporated into France. It is also, more generally, the name of the cultural area whose limits correspond to the historic province and independent duchy....
 in France
France

France , officially the French Republic , is a country whose Metropolitan France is located in Western Europe and that also comprises various Overseas departments and territories of France....
 and off Falmouth, Cornwall
Falmouth, Cornwall

Falmouth is a town, civil parish and port in the Carrick, Cornwall District on the River Fal on the south coast of Cornwall, England, UK. It has a total resident population of 21,635....
  and Bantry Bay
Bantry Bay

Bantry Bay is a bay located in County Cork, southwest Ireland. The bay runs approximately 35 km from northeast to southwest into the Atlantic Ocean....
, Ireland, and is a popular fertilizer in these days of organic gardening investigated Falmouth maerl and found that L. corallioides predominated down to 6 m and P. calcareum from 6-10 m (Blunden et al., 1981).

Chemical analysis of maerl showed that it contained 32.1% CaCO3 and 3.1% MgCO3 (dry weight).

History

An early reference to maerl was made by John Ray in 1690 who reported it from Falmouth. Maerl is still harvested at Falmouth, Co.Cornwall, England, as well as elsewhere. In Ireland, maerl is extraced from subfossil beds in Bantry Bay by Celtic Sea Minerals . The maerl-forming species Lithothamion corallioides and Phymatolithon calcareum are listed in Annex V of the EC Habitats Directive .

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.