Freesteel Blog » Aran Islands Marine ID course


Aran Islands Marine ID course — June 2004

Does this sound good?: If you are keen on diving, go on a marine identification course.

This was one of those experiences where I came out knowing a heck of a lot less than when I went in– subjectively speaking.

Still– I’m not sure what the science of Marine Identification is for exactly. It’s too closed and complete, in a sense, without a statement of purpose.

There’s been a cultural agreement in the biological sciences for how to decide what is and what is not a species, even though everyone knows the boundaries can be quite blurry. Scientists make the effort to discover species and publish judgments with the required level of evidence. This has gone on cumulatively since the Victorian era without the sort of revolution that would cause the whole database to get deleted. Since the science doesn’t go far beyond the the realm of direct observation, much of the information remains valid.

The science of Geology, on the other hand, also begins with a lot of observation, but the theories based on these observations has been thrown out several times, most recently with the discovery of plate tectonics. Cheap and widespread genetic sequencing may yet make a difference to the taxonomic sciences. But that’s for later.

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nudi3 nudi4
A matrix of unidentified little sea slugs, called Nudibranchs after their exposed gills.

We caught the overnight ferry from Birkenhead to Belfast. The two hour boarding process was an extra drag because we were within sight of home across the water. Both the ferries to Dublin and to Belfast load at the same time from opposite sides of the same pier. The free evening meal (served at 11pm) was excellent and big enough to feed a hungry trucker, although unfortunately we’d blown it by having a huge meal beforehand. Stuffing ourselves with a full meal in spite of this proved to be rather painful.

The ferry deposited us in Belfast at seven o’clock in the morning with lots of time for the long drive across Ireland. It’s not as small as it looks. Five hours later, on the harbour in Rossaveal, County Galway, we found Rohan from Bangor, who was running the course. He was sheltering in the front seat of his tiny land rover with two passengers and the back crammed to the ceiling with as much stuff as I take when moving house. Much of it was teaching material: slide projectors, text books, microscopes, specimen trays, photographic equipment. It all had to be hoiked over the railings and stacked inside the ferry in a great pile by the door. We didn’t drop anything in the water. Everything goes to the island by ferry, including a great number of boxed orders from the supermarket, so there is no need to keep the local shops on the island in business anymore. We stashed our kayaks on the top deck.

cenview wturbine
Wind Turbine making fresh water for the island. As you can see, it completely ruins the view, and totally clashes with the natural surroundings of telephone poles, stone walls, brick buildings and tarmac. It’s an utter disgrace. And what are those big white lumpy things in the sky? Clouds. Don’t they have any taste when they formed as to the shape of the local architecture? Get rid of them too. They’re awful. Rain and electricity. We don’t want any of this sort of thing.

The Aran Island Dive Centre is run by Nick Pfieffer who has red hair and is huge. I recognized him from a previous trip to the islands in 1997 with the Cambridge diving club. I suppose it’s no a coincidence he was there. At that time we’d stayed in cottages on Inishmore, the largest of the islands. The weather was terrible and I spent most of the week bicycling up the stony tracks, hiking through the stony fields, across stone walls, to visit the stone ruins of stone forts. I never made it to the other two islands, Inish Oirr (closest to the County Clare coast) and Inish Meain (in the middle).

So here we were on Inish Meain, the least populated of the three, since historically the tourist ferries from the mainland tended to dock on the outer two islands because they were closer and had better harbours. There seemed to be a lot of cars and not many roads. Some of the houses and one of the pubs had inexplicably huge parking lots out front. In the morning, since the weather was fine, Becka and I paddled most of the way round the island, clockwise from the main East pier, to the incomplete North pier, down the hill from the dive centre. The final stretch, through Gregory sound, between Inish Meain and Inish More, was a hectic slosh of wave reflections, like a busy swimming pool before they invented those undercut gutters along the sides that soak up the splashes. The noise of the waves slapping against the hollow plastic canoes was deafening.

We got back just in time to go out on Nick’s boat for a sunny dive.

And so, we became familiar with the routine. It’s an amazing feat that, on an island a mere two by three miles, they managed to situate the dive centre twenty minutes walk from the sea. But there it was. Luckily, a minibus taxi service was available for carting the diving gear and all the other people to and from the harbour while Becka and I walked and watched out for traffic. Also in our group was Sharon (from that original 1997 trip) and Martin (they guy I work with, not a diver, but who was persuaded to stay on for extra kayaking the following week). Sharon, as were all the other half dozen people on the course, was a professional ecologist. You could phone her up on her mobile in the evening and she’d be staking out some bushes recording bat signals. She accused me of pigeon holing her as an expert like all the others when she’s not a marine specialist. But that’s like a trumpet player complaining to a non-musician that they are not going to be any good on the trombone.

The course, in short, went through the teaching us the marine phyla in order of furthest to closest to the human species. That puts sponges are at the bottom and vertebrates at the top. Subsequent lessons went through each major phylum in more detail. Here is a list:

Using no more sophisticated technology than plastic sandwich bags and fingernails, we collected little samples for identification back in the centre. It requires a microscope to see what’s really going on — a great deal more than it appears. There’s life down there, all wriggling and fiddling in the water, like a busy city seen from a mile in the air. When you’re up there you see everything without seeing it at all.

Porifera (Sponges),
Cnidaria (Hydroids and Anemones),
Platyhelminthes (Flatworms),
Ribbon Worms,
Annelida (Segmented Worms),
Phoronids (Horseshoe worms),
Sea Squirts,

Some of these phyla have hardly anything in them, and some are huge.

Rambling about Cnidaria:

The name is derived from the greek word “cnidos” for “stinging nettle”. Cnidarians have nematocytes, which are complex the stinging cells that spring out and inject poison into anything that touches them. Pretty handy thing to have. Do they all use the same sort of poison? Cnidarians vary in size from microscopic hydroids to metre in diameter free-swimming jellyfish. They can be isolated individual anemones, or form colonies that have have hard skeletons like coral, or soft skeletons like sea pens that are able to move and retract down into the ground as though it was a single animal.

Ignoring the external structures, considered to be on the outside of the animals, all cnidarians are circular with a mouth in the middle and tentacles around the rim. They have no anus, so food matter, when they are done with it, comes back out the mouth. Other than that, their variety is vast. Some are free-swimming (jellyfish) and some are stuck to the rock. Not only do they vary in size, shape, colour and transparency, they can form colonies and grow external skeletons. Some colonies are soft with a spongy texture, some are like ferns, some form huge luscious quill feather shapes. And some form calciferous skeletons called “hard coral” that can grow to the size of houses.


It really blew a gale one day, so we were driven to digging for rockpool life under the seaweed.

All have nematocytes. The large cnidarians can eat fish, but mostly they entrap plankton, whatever that is. Does plankton need to be stung before it gets eaten? Clearly not, because there are many animals that eat plankton without stinging them.

There are many animals that look and feed as cnidarians do, if you are not dogmatic about it. Some worms have umbrellas of tentacles that they hold up in the water to catch stuff drifting by. The single species of Phoronid, the horseshoe worm, looks exactly like an anemone. Starfish upside down are very anemone-like, especially given the same lack of a gut: one mouth and no other way out. Even an octopus, were it to glue its head onto a rock and live on what it snagged with its arms, would be like an anemone.

But none of these animals have nematocytes.

No other marine animals have stinging cells. You’d think that if nettles, wasps, and snakes could work it out, and it’s useful, at least one lowly worm would get this facility in four hundred million years of evolution. Why not? Nematocytes are useful enough that there’s even one kind of sea slug that eats hydroids (a tiny kind of cnidarian) and, instead of digesting the nematocytes to which it has grown immune, transports them intact through its flesh until they poke out of its bare back.

The theory of evolution will be a heck of a lot more fascinating if people actually questioned why things don’t evolve rather than only why they do. They treat the spectrum of species as if it’s the definitive answer, not open to criticism. We’ve fallen for that one, of making up animals that don’t exist, once before. We don’t go there now. Everything functions perfectly in its niche, optimally; there are no obvious changes that would make them work much better. And if you think there are, you’re wrong by the axiom of optimality of evolution. If it was an improvement it would have happened already. Therefore it would not be an improvement, no matter what the evidence looks like. Case closed.

beckil colsquirt
Divers doing what they do in the murk of Killkerney bay. It was very currenty at the end of the dive. Usually recreational dives are safer because you can drop everything you’re doing and go into survival mode when you get scared. But when you’re there to do a job (of collecting samples) that’s not a natural option. On the right is a colonial sea squirt.

Why, for example, have the ancient classes of animals, birds and fish, never developed echo-location, while bats and dolphins — very much more recent entrants to those environments of flight and swimming — have?

How hard can it be? Some fish can fly, others live at the bottom of the sea and glow in the dark or deliver electric shocks. There are birds that live on the ice and dive to great depths, and are warm blooded. The variety is wide. Among mammals, you don’t get much further across the spectrum than bats and cetaceans. What is the common factor? It’s not listed among those properties that define a mammal, such as hair, milk and a placenta. These are spurious coincidences, like the presence of nematocytes and no anus, which show up a vast orthogonalized equipment gap that lies between the phyla. The answer is deep. Maybe too deep to discuss.

monkfish sole
On the right, a flatfish, probably sole. Marine identification isn’t much into fish because they’re generally easy to distinguish, and they’re mobile, so they don’t necessarily tell you much about the local ecosystem. Also, they swim away and hide, so you can’t count them even if they do belong where they’re found. In the field of economics, nothing matters except the fish. The one on the left is a monkfish, sometimes known as an angler fish because it sits on the sand and attracts its prey by waving it’s lure. It’s mouth is so huge that when it opens it, everything gets sucked in. In very expensive restaurants, rich people eat their tails, but I think they’re missing something remarkable which no mere chewy taste, not even with the most expensive wine in the world, can match.

Back to reality. Sponges are spongy and have no internal organs. That in itself is a strangeness. It’s a multicellular organism where all the cells are the same, but they can build bizarre shapes like barrels and columns that help them filter the water. Rohan liked to show how you could tell a shredded carrot sponge wasn’t something else that just looked orangey: you took a piece and squeezed it until it dripped orange juice. There’s another kind which, when you do this to it, compresses down and sticks your fingers together like glue. The boring sponge is big and yellow and full of holes. It’s boring because it bores through the rock as it grows and makes a firm anchor. I don’t see why they don’t grow hearts that beat. They’re not plants, after all.

The default answer to everything if you ask what it eats, is: it filter feeds. Sea squirts are gelatinous objects that suck and blow water through two different holes. They vary in size from light bulbs down to bits of moss that are colonies of microscopic animals. Most divers mistake these colonies for sponges. The expert knows they’re not, and is able to name the species, thus closing the question by proving he knows more words than anyone else. Perhaps the name is a key for looking it up in an encyclopaedia to find out the rest of the information that’s not visible. But usually, the entry just lists its set of identifying properties and the areas and habitats the species can be found. You read this and nod your head: it’s right, it looks like they say, and it lives where you found it. The circularity of investigation is momentarily gratifying.

bryzo bugula
I think these on the left are actually hydroids, but many bryozoans, including Bugula look kind of like this. On the right is a magnification of one of its strands. It’s got many moving parts of unknown function. Perhaps they are there for stirring the water.

The stuff that’s stuck to the rocks and is not plant is called “animal turf”. Let’s imagine that things underwater are much bigger than they would be on land, because they don’t have to protect themselves against the gravity and the harsh changes in temperature.

Examine a rotting carcass on land, when it’s got all kinds of fungus, mould, bacterial structures and tiny worms and crunchy insects crawling on it. Suppose you took everything, all that activity and life, and made it one hundred times bigger. That’s kind of like what it is underwater.

This is a crayfish, not a lobster. See, no claws. What do lobsters use claws for, if these guys don’t need them? How do crayfish pick up their food? The tail is used as a scoop paddle to swim backwards because they’re too unstreamlined to go forwards. But their eyes cannot see in that direction. Nice feelers, though.

In the future we will save the effort because we will have a DNA scanners. All you’ll need to do is snip a piece of a starfish or a tentacle off an anemone, pop it in the scanner, and it will quickly sequence a few thousand DNA base pairs until there’s enough to match the pattern to its library of species genomes. Like identifying a fingerprint, it will accurately print the name of your species without needing to look further. Job done. Whatever it is.

You can do this to whole ecosystems. Lift an entire reef using a crane, grind it up and dissolve the life from the rocks. Feed the material into the DNA spectrometer. It’ll say we have 90% bacteria, 5% Cnidarians, 2% bryzoans, 2% crustaceans, 1% the rest, and give a list of all the species present, and the number of individuals of each species, and the organic mass of each animal. Clones unfortunately get miscounted towards the same individual since this mechanism won’t be able to tell them apart.

Biology, then, will become an information processing science. The DNA — which is pure information — is out there doing something in the physical world, and the good stuff merely comes back as more DNA because it has managed to convert matter into more successful bodies. This all there is to life.

Some say it’s true.

Life is the tool that DNA requires to make more DNA. We are the slaves to our genes. Our human nature is a product of evolution. We must breed, propagate, make way for our selfish desires and our kids, and to hell with the consequences as long as there is more DNA of the same type a generation later.

However, who says slaves can’t get an education and break free? This can happen. Evolution is not a perfect all seeing all knowing force. It makes mistakes. We’re too brainy for our genes to maintain control, except by fluke. If we over-ride the messages from our genes — as it appears we can — then we are awake and on the outside. We make our own choices without following the laws of our masters. Genes then can work for us, rather than the other way round. Think about self-medicating with psycho-active chemicals. It’s a whole other thing. For all time until now, only the genes could squirt chemicals into our heads and make us feel and do what they wanted us to. Now people can squirt chemicals into people’s heads, and they’ll do what they want. A person can squirt chemicals into their own head and they’ll follow their own chosen desires, if they don’t make any mistakes. What would they choose? They want to be free and have a good time.

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kilk3 kilk4
A gentle dive in Kilkeran Bay, with Zostra sea grass and maerl (a calcified red algae that’s almost like coral) and a thornback ray for embelishment. I couldn’t understand how there could be lumps of living sponge rolling around the place without being attached to anything, but it’s a weird world.

See the sea as a big dark volume. Terrestrial life is thin: one tree can span the entire thickness of the non-aquatic bio-blanket. It has roots that go down as deep into the ground as life ever goes, and it pulls water and nutrients up to the heights of its leaves. The ecosystem is in continual communication. All parts are connected.

The sea doesn’t work like that. There’s nothing that stretches down to the abyssal depths and brings up the nutrients that have sunk into the darkness. Everything heavier than water sinks to the bottom, 4000 metres down in most places. For reference, it’s totally dark by about 100 metres. It’s full of life at the bottom, because that’s where the food fell. There’s no reason for anything that can live down there to swim up to the top because there’s less up here, and it’s more likely to be seen and get eaten. Still. On a dive in the southwest corner of New Zealand, Becka and I saw a Hag Fish curled up behind a rock. I knew them from drawings in a book. When I looked it up later, I found out that it was a deep water species that fed on carcasses of meat. It’s only ever found in the shallows in the southwest corner of New Zealand.

What happens to the organic matter that’s down in the deep? Things keep eating things, they die and get eaten by other things. It’s a closed system that cycles and gets larger and larger all the time as material rains down from the surface, and as long as not too many animals fall into trenches and get turned into oil.

What should happen is eventually there’s no room. There’s a layer of worms, cucumbers and crabs two thousand metres thick across all the deep oceans. One day something touches them and they all rise up and take over the land mass of the planet like a plague of locusts.

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Jewel anemones. All different colours. Thus showing that the colours are random. What are the colours for? These things aren’t flowers; they eat anything that goes into them. There are no bees. And anyway, you can’t see the colours until you shine your electric torch at them because everything is blue at depths below ten metres. Hey, is anyone answering these questions?

My species identification skill is now a Known Unknown, rather than an Unknown Unknown. I still don’t know much, and I can’t remember latin names. Anyways, the whole Linnaean hierarchy of species categorization is shortly to undergo a revolution, and with good reason. The data is structured into a fixed hierarchy of levels: Kingdom, Phylum, Order, Class, Family, Genus, Species. All life that counts is assumed to have come from one ancestor. This tree represents the approximate clusters of divergence along each branch. That’s the idea. Apparently it doesn’t work since in some parts the species have diverged more than seven times since the primordeal life form. Maybe the divergence doesn’t always cluster; you have a central stem and the genera and species spawn off from it further and further along the tree rather than fanning out all at once.

What it means is that the structure keeps getting broken. They have to rewrite Genera as Families, or recast a Family as a Genus to get the picture to fit this Victorian structure. Vertebrates form a Phylum, and in that phylum are fish, reptiles and mammals, which are Orders. There’s a lot more room in the mammals section than there is in the fish section, since there is so much more diversity among fish, if you stick rigidly to the datastructure.

So, we hope, the whole thing is being refactored. Just as we do in computer programming when the structure is no longer sufficient. Look forward to a more free-form database. I want to see a totally common worldwide taxonomic reference online and for free that’s wikified. Any time there’s a disagreement about how it’s laid out, scan the DNA and upload the sequence so we can compare the similarities and the evidence of divergence.

seaspid spidcrab
Sea spider vs spider crab. I’d never spotted a sea spider before and didn’t know they existed. They’re like a normal spider, but with absolutely no body at all. How on earth does that help them, and do they spin silk?

The truth is there. Although I don’t know what’s to be done with it.

Our last dive was just for fun. Nick drove us to an obscure dive site just off the beach in Gregory sound where there is a drop off to around fifteen metres from the kelp. There’s then a huge crevice at the base that goes in horizontally about three metres and is in most places wide enough to swim under. It’s an extreme overhang with all kinds of life and lobsters wandering around in there. Everyone else except for Becka and me missed it, either by swimming in the wrong direction in the kelp, or hitting the sand beyond the ledge and heading in the right direction from the wrong place and finding nothing but deeper water and gravel.

I wonder if I’ll get back there one day.


Julian Todd 2004-09-01