Intertidal Coral Gravel (Ireland)

Intertidal coral gravel from Mannin Bay (Ireland), where it’s known locally as “maerl”. Often referred to as a biogenic coral sand, it's primarily comprised of Rhodophyta (red algae), which is not a coral at all. The grain sizes are also frequently larger than 2mm, classifying this as a gravel rather than a sand. Besides the Rhodophyta, several gastropods can be seen in this image as well.

This sampled provided by RHCM.
References: www.sandatlas.org/maerl-from-ireland