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Barrel Jellyfish off St. Michael's Mount

Barrel Jellyfish off St. Michael’s Mount

Barrel Jellyfish

Every year they appear off our Cornish coast in swarms. As big as a dustbin lid these aliens have been drifting through our oceans for over 500 million years. Jellyfish – the very name strikes terror – and these are giants!

Yet jellyfish are some of the most ancient and simple animals on the planet. Because they have no brain, heart or blood.  Their soft bodies are over 90% water, and they move in a mesmerising pulsing motion operated by a simple net of nerves.  Though infamous for their stinging tentacles, most species are harmless to humans.

Sea Monsters or Gentle Giants?

Several jellyfish visit UK waters. The Barrel jellyfish is our largest, with a diameter of up to 90cm and weights of up to 35 kilos. And in summer and autumn they swarm off the coast, sometimes washing up in large numbers.

These giant jellyfish swarms cause quite a stir. However they are gentle giants. Barrel jellyfish feed entirely on tiny plankton, so their sting is too weak to hurt humans. In fact so harmless is their sting that many have small fish living in their barrels, darting out to catch prey and then shooting back to the safety of their ever drifting home.

An ocean oddity

The Barrel jellyfish has a strange appearance, even compared to its relatives. It has no trailing tentacles around the bell, but has eight, thick arms underneath. Its arms end in paddles covered in frilly, cauliflower-like tissue where they meet the body. If you look close up, these frills are small, dense tentacles around hundreds of little mouths used to catch and eat their prey.

Close up of barrel jellyfish

Close up of barrel jellyfish

The swarms explained

Barrel jellyfish swarm in warmer summers when there are large plankton blooms offering a plentiful food supply. Usually they drift in the open ocean, but blooms in warm, shallow water bring the jellyfish towards the coast.  In winter they will return to deeper waters.

Part of the ecosystem

Barrel jellyfish are important for supporting other species. An amphipod crustacean Hyperia galba lives in the body cavities of Barrel jellyfish, feeding on the eggs and food scraps. Jellyfish are also prey for the Leatherback turtle (Dermochelys coriacea), which migrates to cooler northern waters to feed on the summer swarms. We did spot a leatherback turtle last year but he was too far away and by the time we got close enough to film he slipped below the surface. Maybe luckier this year…

Barrel Jellyfish Cornwall

Barrel Jellyfish Cornwall

Cuba Havana Sunset

We’ve recently got back from a trip to Cuba. This time scuba diving in a region located within the Ciénaga de Zapata Biosphere Reserve. Until recently the area has been closed to tourism due to it being a Military forbidden zone and close to one of Castro Fidel’s homes. It has been around 50 years since anybody has dived there.

Cuban Reef with Diver

Most of the trip was spent on a liveaboard which took us to different dive sites, some of which where unnamed. Some of the locations visited include the Russi Wall and Canon de Blanco near Cayo Blanco,  a tiny island no bigger than a strip of sand that drops abruptly into the blue.

Caribbean SpongesWe also dived Canon de Sigua a gradual sloping drop off which was covered in undamaged stunning Caribbean corals.

Cenote Diver

 

Another highlight was diving a cenote in Playa Larga, also known as ‘The Bay of Pigs’. The cenote (or casimba as they are called in cuba) was named ‘Casimba del Brinco’ meaning “jump”‘, in reference to the 2.5m jump required to enter the cavern. The cenote itself was visually stunning and ethereal, in particular the bright shafts of sunlight that shone through the crack in the top of the cave’s ceiling.

Cenote Cuba Divers