Forest of sea fans at the drop-off outside Plymouth Sound |
Manacles coral garden ; sea fans with soft corals and cup-corals |
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the way that an intact forest suggests a wonderfully long-standing safe haven for marine life . It also means that we , as divers , need to be very careful with our fins and SMB lines while admiring the scenery , because a dislodged and killed fan would take a long time to replace !
An intriguing aspect of a group of sea fans is that they are generally all orientated the same way and across the current . This means that all the polyps that make up a fan get good access to passing planktonic food . The occasional more bush-like fan without a clear orientation probably reflects an unpredictable swirling current at that spot . Each polyp has eight tentacles ( sea fans are octocorals ) for grasping food and , when actively feeding , these give the fan its attractive fuzzy appearance .
The polyps and therefore the live fans are generally pink-orange but sometimes a more buff colour and occasionally white . Underneath their coloured fleshy parts , is a dark-brown skeleton of tough protein ( gorgonin ) reinforced with calcium carbonate . A washed-up skeleton gives no clue to the exotic nature of a live colony so , when it prompts the question of ‘ what is the odd brown antler thing on the strandline ’ from a non-diver , they are utterly amazed to see underwater photos of live sea fans in all their glory .
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Sea fans of different sizes along the base of a Devon reef |
A young sea fan , yet to branch , in Plymouth Sound |
The pink sea fan has been a legally protected species since 1992 and it is illegal to kill , injure or collect them . Their principal man-made threat is from bottom-trawling and dredging , with initiatives such as the Lyme Bay Reserve showing the great value of protection against such activities . While natural events such as severe storms can also cause damage , research in Lyme Bay showed the sea fan population recovered much more quickly from the 2013 / 14 winter storms than it had from the previously allowed bottom towed fishing . Fascinating research is also being done on how other sea fan populations can be protected , on their genetics and how their distribution might be affected by climate change and variations in oceanic currents .
Finally , a marine biologist ’ s confession … pink sea fans are home to three well-known and rather famous associated species , a sea anemone , a nudibranch sea slug and another small mollusc , but I have never spotted any of them ! Multi-tasking is not my strong-point and I think I ’ m always too busy gawping and enjoying sea fan scenery , trying to capture a wide-angle shot that does it justice and watching where I put my fins ! �
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