Blue Planet II – ‘Green Seas’

From blue, to green.

In the far North, it is spring after 3 months of winter. Starfish wake up and spawn, and many creatures eat starfish eggs! A seacucumber, essentially a mouth with ten arms, stuffs itself with starfish eggs like a glutton. Sea pens, which look a bit like an old fashioned TV ariel covered in frost, come up from underground and soon a whole marine forest of kelp is there.

In Southern Africa there are also forests of kelp. An octopus camouflaged herself to hunt for crabs. But once again, the hunter can become the hunted, as octopus are prey to pyjama sharks. A pyjama shark gets the octopus, but she slides her tentacles into the shark’s gills. This means it can’t breathe, so will have to let go if it wants to live! Very clever of the octopus. She then disguises herself using lots of shells. The shark can sense that food is there, but the disguise seems to confuse it, it keeps sniffing at the shells even after the octopus has escaped.

The Into The Blue “behind the scenes” segment at the end which showed how the crew filmed these natural events, showed that this octopus loved the camera! She became
one of their favourite individuals, so they were pleased she escaped her encounter with the shark. They referred to her as “a rock star”.

A bright orange and yellow garibaldi fish is shown to be a bit like a gardener. Many human gardeners have had to remove snails, and this garibaldi fish does too. He has to get rid of snails that come to eat his algae, chases off a stingray, and has to remove sea urchins, which look a bit like a ball covered in long spikes. Those spikes are apparently needle-sharp. There are lots and lots of sea urchins, so it’s rather like removing weeds from a garden, they keep coming up. The garibaldi fish has to hide at nightfall, as that’s when dangerous predators come out, leaving the sea urchins to have the algae to themselves for the night.

The sea urchins were compared in the programme to locusts, eating all the vegetation. We see a close-up of their mouths, which are full of pointy teeth!

Sea otters are a very popular cute animal. A mother sea otter has to eat “over 40% of her body weight every day” to produce enough milk for her pup. Their favourite food appears to be shellfish, so they prey on sea urchins. Sea otters were almost hunted to extinction for their fur. As always, this sort of thing has a knock-on effect. With no predator, this left the sea urchins free to consume all the kelp forests, and so what was once forest became a barren wasteland filled with sharp spikes. When the sea otters became a protected species, their numbers recovered, they preyed on the sea urchins, and the kelp forests returned.

Australia has sea grass, and it does look just like the grass on land! A green turtle was seen grazing on it. The turtles can’t relax too much though, as there are tiger sharks about. Again, it’s a delicate but efficient food chain. The turtles know they have to keep moving to get out of the way of tiger sharks, which means the turtles don’t eat too much sea grass, so it balances out. The sea grass doesn’t become overgrown, but there is enough left.

A huge army of spider crabs march on, hundreds and thousands of them to the point they are clambering over each other. They have come here to literally break out of their shells. The new shells take a few days to harden, so that makes them easy prey, as they are easier to eat. They are also weaker physically once they are “reborn”, so they hide in the middle of the pile under the harder-shelled crabs. This is why they group together, safety in numbers. And it works, most of the crabs survive. The old discarded shells that litter the ocean floor at first glance might look like dead crab bodies, but far from a sign of a slaughter, it’s a sign of survival, that so many crabs have moulted and gone onto the next stage.

A giant cuttlefish, a big male, has mated with a female. He won’t allow smaller males to mate with her… but that doesn’t mean the female won’t mate with them, or indeed that the smaller males can’t find a way. They would have no chance if it came to a fight, but the smaller males can make themselves appear female by changing colour and making themselves appear smaller. This fools the big male, so the smaller male can mate with the female. Multiple, varied partners are a good for survival of a species, as it ensures genetic diversity.

The sea dragon is extraordinarily pretty and colourful. A male has mated with a female, and is carrying the fertilised eggs with him. Algae has grown over the eggs, but the babies still hatch. Soon there are lots of sea dragons. It’s an enchanting sight, they look like fantasy dragons flying in the sky over a forest.

Mangrove forests show the unusual sight of roots and fish swimming among them. It looks surreal, you wouldn’t normally put tree roots and fish in the same place. When the tide goes out though the fish have to leave the shelter of roots, and they can be taken from below the sand by zebra mantis shrimp.

The male zebra mantis shrimp is collecting food for his mate. She relies on him, staying underground as she is putting all her energy into the eggs. They may have been together 20 years… but one day, one we see goes elsewhere, to another female. She is bigger, and will therefore produce more eggs. This will mean she will want more food, but in turn means he will father more offspring. As for why he went to her in the first place, the larger female will have lost her mate, either to another female or to a predator, so she sends a signal out to catch any other males attention.

Phytoplankton makes a sea look very green. Anchovies come to eat them. Then many sea creatures come for the anchovies! Sea lions, sea birds, and humpback whales. But like all food chains, it depends on the starting point. A bit like the ecosystem in general, it’s like a house of cards, remove the foundations, and the whole thing collapses.

‘Green Seas’ was one of the most fun episodes to watch, certain individual creatures such as the amazing octopus, the gardening garibaldi and the beautiful sea dragon made it one of the most enjoyable episodes in the series.

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