Maerl

Maerl develops when coralline red algae, which have a hard calcium carbonate skeleton, become free-living due to fragmentation. Large maerl thalli are amongst the oldest marine plants in Europe. Although they are very slow-growing, the maerl thalli sometimes accumulate into flat beds, ripples or large banks of live and dead maerl, or dead maerl only. The three-dimensional structure of maerl thalli forms an interlocking lattice that provides a wide range of niches for infaunal and epifaunal invertebrates. Therefore these beds can harbour a very high diversity of organisms, some of which are more or less confined to the maerl habitat. Maerl beds are also an important source of calcium carbonate grains for other coastal habitats, especially beaches and dunes. Maerl species are very slow-growing algae, and some maerl beds are estimated to be about 8000 years old.

Nature and importance of maerl beds

Synopsis of maerl distribution in Europe and in the UK

Relevance to MNCR biotope classification

References