Maerl is a hard seaweed with a purple-pink colour that forms reef-like carpets, known as maerl beds, in the dim light conditions of the shallow seas along the European coasts. While their calcium carbonate skeletons may cause them to be mistaken for corals (which are animals), maerl beds are constructed by photosynthesising algae that create a hard brittle skeleton in their cell walls. Within the Mediterranean Sea, maerl beds are ranked as one of the most important ecosystems as they offer vital services for both fisheries and carbon regulation. Unfortunately, the combination of destructive human activities (bottom trawling and recreational fishing, offshore construction and unregulated diving and anchoring), climate change (with increased high-temperature anomalies and storm) and invasive algal species is critically endangering these vital ecosystems.
In an effort to conserve maerl beds, this habitat has been added to the OSPAR list of threatened and/or declining species & habitats and was included in the EU’s Habitats Directive, that ensures the conservation of a wide range of rare, threatened or endemic animal and plant species. Furthermore, destructive fishing over Mediterranean seafloor supporting coral and maerl habitats is prohibited under European law. However, in order to allow the effective implementation of these policies through area-based management approaches (e.g. Marine Protected Areas), there is a need for reliable information on where maerl habits are located.
In order to address this need, a study in Nature has combined the available observations of maerl habitats with data on the environmental conditions in a state-of-the-art habitat modelling techniques. This approach allows to predict the locations where the environmental conditions are able to support maerl habitats. The map of the week shows the modelled spatial distributions of maerl beds across the Mediterranean Sea.
The data in this map are provided by EMODnet Seabed Habitats.