The tube-dwelling Burrowing Anemone is common in the Fal Maerl
harass a hermit crab out of its hard-earned meal. Meanwhile, a large dragonet with striking reddish colouration that matches the Maerl scoots past.
Back to Maerl itself, it is actually a collective term that applies to( around the UK) three species, which can be hard to distinguish from each other. The nodules grow extremely slowly, less than 1mm per year, and can live for up to 100 years with beds developing over the millennia. For example, the one in the Fal is thought to be at least 4,000 years old. Maerl needs shallow well-lit water with enough current to wash away silt so the Scottish west coast, with its numerous sea lochs and channels between islands, is home to the majority of the UK’ s extensive beds.
Maerl beds face serious threats, most dramatically from bottom-trawling, dredging and other types of seabed disturbance. This not only damages them directly but, if carried out in nearby areas, has the potential to mobilise contamination which may also cause harm. Overgrowth of other smothering seaweeds on beds is
a worryingly increasing hazard, and it can be enhanced by the nutrients in land runoff, elevated water temperatures and the presence of non-native algal species.
These unique and largely unseen ancient habitats certainly need and deserve our care and protection. Beyond their intrinsic beauty and vibrancy, Maerl beds are important nursery grounds for commercial fish and numerous invertebrates such as
juvenile scallops because of their unusual three-dimensional structure. Recent research suggests that due to the way it develops, with a living Maerl layer covering over dead deposits, an undisturbed bed can be even more effective at locking up carbon than seagrass. But … having said all that, I think a single dive on a rich maerl bed in clear conditions would convince anyone of the marvels of Maerl! �
Mating Sea Hares
Paul’ s photos and video clips capturing UK marine life stories are on Instagram @ paulnaylormarinephoto
Wrinkled Swimming Crabs are a regular sight on the Fal Maerl but I rarely see them elsewhere
Harbour Crab adopting a typical defensive stance
Pre-mate pair of Risso’ s Crabs
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