Maerl is a collective name for non-geniculate coralline red algae with a certain growth habit. Maerl grows at a rate of c. 1 mm per year. It accumulates as unattached particles and forms extensive beds in suitable sublittoral sites. The term maerl originally refers to the branched growth form of Lemoine (1910) and rhodolith is a sedimentological or genetic term for both the nodular and branched growth forms.
Maerl off the coast of the Isle of Arran
Calcified remains of maerl, on the "coral beach" in the Isle of Skye
Maerl in Lanildut.
Pieces of popcorn-like maerl from Fuerteventura island.
Rhodoliths are colorful, unattached calcareous nodules, composed of crustose, benthic marine red algae that resemble coral. Rhodolith beds create biogenic habitat for diverse benthic communities. The rhodolithic growth habit has been attained by a number of unrelated coralline red algae, organisms that deposit calcium carbonate within their cell walls to form hard structures or nodules that resemble beds of coral.
Characteristic mauve coloured rhodolith
Benthic communities found in rhodolith beds Example of the seaweed and zoobenthic communities found in rhodolith beds on the Brazilian coast. This picture highlights the presence of gastropods, echinoderms and a turf algae assemblage.
Vertical and latitudinal changes observed in the size and density of rhodoliths on the floor of the continental shelf off Espírito Santo in Brazil
Rhodoliths on the northern shore of Fuerteventura
