Lithothamnion

Lithothamnion is a genus of crustose coralline red algae in the family Corallinaceae. Like other coralline algae, its cells secrete calcium carbonate, forming a hard calcareous crust that adheres to rocks and shells. These calcified thalli contribute to biogenic carbonate sediments and to maerl beds in some regions.

The thallus is typically encrusting or laminar, with a pink to purplish-red color. It forms thick crusts up to several millimeters or centimeters, depending on species, and has a rigid, calcified skeleton.

Distribution and habitat: Lithothamnion occurs in temperate and polar seas worldwide, usually in subtidal zones from the lower shore to shallow depths, on hard substrates such as rock and shells. It is a major constituent of maerl beds in some coastlines.

Ecology: By building calcium carbonate frameworks, Lithothamnion stabilizes sediments and provides habitat for invertebrates and juvenile fish. Maerl beds are slow-growing and vulnerable to physical disturbance, especially dredging and bottom-trawling.

Reproduction: Like other red algae, Lithothamnion reproduces sexually through conceptacles and may spread vegetatively by fragmentation of its crust, aiding recolonization after disturbance.

Taxonomy and human use: Lithothamnion belongs to Corallinaceae within the Corallinales. Studies using molecular data have refined species boundaries. Maerl produced by Lithothamnion and related genera has been harvested for lime and soil amendments, subject to conservation measures where beds are threatened.