Algue Feuille De Pierre Encroûtante

Overview

Lithophyllum incrustans is a calcified red alga that forms thick, hard crusts on rocky substrates. It is a key structuring species in many marine environments, often dominating rocky surfaces and creating complex micro-habitats for other organisms.

Appearance

This species appears as a thick, calcareous crust that can reach over 30 cm in diameter. Its appearance changes significantly with age: young specimens are typically pink, smooth, and circular, adhering tightly to the substrate. Older individuals develop a rough, mauve-grey surface with raised, convoluted margins that may detach from the rock. In some cases, the alga can form thick, irregular concretions. Areas that have died often appear as bleached, yellowish-white patches.

Distribution & habitat

It is widely distributed across the temperate Atlantic, from Scandinavia to South Africa, and is also found throughout the Mediterranean. It typically inhabits well-lit rocky areas, including the lower intertidal zone, rock pools, and subtidal regions. It is often found in exposed environments where it can withstand wave action, sometimes forming notable reef-like structures in high-energy zones.

Biology & behavior

As a photophilic, calcifying organism, it requires sufficient light and calcium to thrive. It grows relatively slowly, with young crusts expanding by approximately 7 mm per year. The species is known to be a foundational element of its ecosystem, providing a stable surface for various small invertebrates and other marine life. It can be difficult to distinguish from other encrusting coralline algae in the field without microscopic examination.