Song for Jasmine

Issue 54 of Underwater Photography magazine dropped into my inbox recently. Underwater Photography magazine is a free electronic publication by Peter Rowlands (thanks Pete!). Don’t be fooled by the cost, it’s a highly polished publication, worthy of attention by anyone serious about getting into the water with a camera.

When it comes to taking photographs underwater, there’s lots of good advice out there about technique and equipment. I don’t consider myself to be an expert in underwater photography, but I’ve picked up a few simple tips that I haven’t found mentioned anywhere else, so I’d like to share them with you.

I’ve used two cameras underwater, a Nikon Coolpix 990 in an Ikelite housing with an attached strobe, and a Canon Ixus 400 in Canon’s own WP-DC800 housing.

The Ikelite housing is a work of art, but it’s big, and when you dive with it, you can’t ignore it. The controls are big and chunky, easy to manipulate even if you’re wearing thick gloves – which I wasn’t, since I only used it in the Maldives, where you’re not supposed to dive with gloves. It doesn’t wobble around in your hand, you can get a good grip on it thanks to its large handles.

The Canon housing is much smaller, and has correspondingly smaller controls. It could conceivably fit into the pocket of your BCD, though I wouldn’t recommend that as it can be uncomfortable when you inflate your BCD. I prefer the Canon housing for it’s compactness, though I found the Ikelite easier to use in some ways, precisely because of its size.

So what have I learned about using them? Firstly, one of the most important pieces of kit for underwater photography is your dive-buddy. A buddy who knows what you want to photograph, and helps you find it, is a great asset. It’s all too easy to get engrossed in taking photos and to forget to look out for your buddy as you do so, so it’s important to have your buddy in tune with what you’re doing and how you dive.

Your buddy can help in other ways too. For static subjects, having your buddy illuminate the scene with a diving-lamp is a great help. You shouldn’t rely on flash alone to light your subject for several reasons. For one, it’s not nice to the fish to just set off a flash in front of them, if there’s a constant source of illumination they can at least adapt to it, and the flash is then less of a glare. Using flash to supplement the light, instead of as the main source of light, is kinder to them.

It’s also very hard to frame the photo well in the viewfinder if it’s poorly lit. With your mask and the camera-housing between you and the screen, your view is somewhat restricted. Having the scene well lit by a buddy helps enormously. Of course, many shy creatures won’t stay around for the light, but if anything, the noise of your bubbles will probably scare them more than the light.

If you’re relying on autofocus, again, a well-lit scene is important. But even then, modern cameras can easily get confused underwater. Floating particles in the water can distract the camera, and it may have a hard time identifying the subject. This is especially true if you are trying to photograph something at the back of a hole, or hidden away somewhere in a coral reef. If you know what you are looking for before you dive, you might want to lock the camera focus at an appropriate distance, and simply press the button when you are at the right distance from your subject. That still leaves some guesswork, but at least the camera isn’t hunting for focus, draining the battery all the time.

If you do leave autofocus enabled, you can help the camera by setting it to focus only on the centre of the scene, instead of letting it guess which part of the scene you are interested in. It’ll probably guess wrongly underwater, and you can always crop the finished photograph to re-frame the subject.

Perhaps the best tip I have come across, thanks to Antonio, formerly of Ocean-Pro Dive-Team in Coco Palm resort, is to dive without the camera in the housing!

No, seriously, if you haven’t used the camera housing for a while, since your last diving holiday for example, consider taking the housing down without the camera in it first. That way, if there are any aging defects that will cause leaks, you get to find out about them without ruining your camera. You should test the housing to the maximum depth that you intend to use it, just to be sure. Thanks for the advice, Antonio!

These suggestions may not help you take the greatest photos ever seen, but I find they increase my success-rate for casual shots considerably. I hope you find them useful!

On Monday, my blog will be one year old. It seems to be traditional to celebrate your first ‘blogiversary’ by reflecting on the previous year, asking people what they think of your blog, analysing your statistics, stuff like that. I’m not going to do that, … much.

By far the most popular article on my blog this past year has been Charles Darwins’ first theory of evolution, with Songs about Pollution a distant second. Quite why people are so fascinated with singing about pollution is beyond me, I’m not sure I really want to know, so I’m not going to analyse my stats more than that.

So, I’ve decided to celebrate my blogiversary by asking “What do you see in my blog”, but with a twist. Here are some photos of fish and other creatures that live on coral reefs. Some, like the black-cheeked moray at the top, are always easy to spot. Others manage to hide themselves well, even when you’re looking straight at them. That’s what these photos are about, and I invite you to see if you can identify them. Thanks to Earth, Wind & Water for giving me the idea.

As always, if you click on the photo you will get a larger version, which will definitely help in some cases. I’ll add a comment in a few days identifying everything, in case you can’t make them out.

Looking at these pictures again makes me wonder how many times I’ve looked at a reef and missed something. I’m sure it’s happened a lot, there’s so much life down there that I must surely have missed more stuff than I can imagine. That’s part of the magic of diving, you can dive the same place time and time again and still find new things to enjoy.

These photos were all taken in the Maldives, the only place I’ve dived with a camera. It takes a lot of practise and luck to get good underwater pictures. Some of the subjects are hard to see because the shots capture the way in which it blends in well with its surroundings, others are hard to identify because the photos are not really all that good. Never mind, here goes!

This first one is easy enough. It takes some practise to be able to spot them when you first start diving, but when you get the measure of them it’s often easy to find them – some of them, at least. In the Maldives, if not elsewhere, they can get quite large, 12-18 inches (30-45 cm), and often hide right on top of the reef at 15-30 feet (5-10 metres) depth, where the light is good.

This one is rather harder. I dived several times at this location, in Ari Atoll, but never once found this fish for myself. Even when you know where to look for them they’re hard to find. Like many smaller fish, they have a habit of turning themselves to present a narrow profile to larger creatures (such as me) to better avoid being spotted.

This one is even harder to identify. If you don’t know this fish exists, you probably won’t see it. Like the fish in the photograph above, it insisted on turning itself narrow-side on to me, making it harder to get a good picture of it. I wonder how many of these I’ve overlooked, this is the only one I’ve ever seen.

This one is the hardest of the lot. Even I have trouble making it out. I can see a fin easily enough, but to figure out exactly where the head is, the body, and the tail, that takes some scrutiny. If I recall correctly, I only saw this one because it moved.

This one is fairly easy. This is the only one of these I’ve ever seen, and it was big, about the size of a watermelon. I like diving close to the reef, moving slowly along it looking for small things hidden away. Finding myself almost eyeball-to-eyeball with this guy came as quite a surprise. Incidentally, this is one good reason not to touch the reef while diving. These things are poisonous to the touch, and well camouflaged.

Lastly, this is one of my favourite photos, though not one of my best. I wanted to get a picture of the banded boxer shrimp, but the camera chose to focus on something else instead, and I’m glad it did. So the question is, how many shrimps can you see in this photo? I’ll give you a hint, there are more than two.

The Maldives claims to be the place where “even the sharks are friendly”. I’m not too sure I’d want to meet a ‘friendly’ shark, I’d settle for ‘indifferent’. In my experience, the sharks in the Maldives are definitely that, I’ve seen several dozen and they’ve never shown the slightest interest in me. That’s not the only reason why the Maldives is a fantastic place to dive, though it certainly helps. If you’re thinking of going there for a diving holiday, I can recommend it.

I’ve visited four islands on diving holidays, some of them two or three times. I learned to dive with Sea Explorer, at Reethi Beach (Baa atoll), back in 2000. I’ve dived at Machafushi (Ari atoll), where they have an impressive wreck, deliberately sunk on the house reef. I’ve also dived with Ocean-pro dive-team, at Coco Palm (Baa atoll) and Mirihi (Ari atoll).

It has to be said, none of the websites for the islands or their dive-schools do them justice. They are very pretty to look at, but don’t really give any idea of what it’s like to dive in those places. Hopefully, I can go some small way to filling that gap, with this and future articles.

The Maldives is a great place to learn. Shallow lagoons make for easy first lessons, and warm waters mean no messing around with thick wetsuits. The resorts all have a large variety of dive-sites to choose from, normally with a good range for all levels of ability and all interests, from beginner to expert diver. Many (if not all) of the resorts are PADI dive-centres, though I believe they also accept most other internationally recognised certificates. Your tour-operator can probably check for you if you are in any doubt.

Although PADI certify divers to 40 metres (120 feet) (with the Deep Diver certification), the Maldives imposes its own limit of 30 metres (90 feet). Diving below that is not permitted in order to limit disturbance to the environment. That’s not really a handicap, there’s plenty to see in that 30 metres. That said, it’s true that the scenery does change with the depth, and if you are limited to shallower depths by your certification, you might want to consider taking an extra course while you’re there, to get the full value from your dives.

You can dive on the house-reef of your resort, but most of the diving happens from boats. Depending on your resort, there may be one or two boats in the morning, and one or two in the afternoon. Reethi Beach, for example, run two boats in the morning, one which leaves early and does two dives (with an hour’s rest between them) and one which leaves later, doing only one dive. That lets you choose the pace you want for your holiday.

You have to sign up for the boat you want the day before, so they know how many people to expect. Places are limited on each boat, and some popular dive-sites get fully subscribed quickly, so depending on how fanatical your fellow holiday-makers are, you may have to be quick! If you miss out on a site you wanted to visit, just ask the dive-centre. They’ll be willing to re-schedule it soon enough, after giving a day or two to avoid over-diving at the same site, and you’ll get your chance.

Some resorts, Coco Palm is one of them, also organise all-day trips. The boat leaves Coco Palm early in the morning and takes in three dive-sites. You eat lunch on board, and because it’s a longer trip, you get to go to some of the farther sites, places that you might otherwise not get to. It can be quite tiring, but it’s great fun!

House reefs can also be a lot of fun. If you want a rest from the boats, a house-reef is a more leisurely dive. In fact, the house reef at Machafushi is the place I’ve dived at most in the Maldives. The ship sunk there attracts a great deal of life, and it was always a pleasure to dive there.

For first-time divers, there are a couple of specific tips I can think of. These apply anywhere, not just to the Maldives. First, if you’re hiring equipment from the dive-centre, check the pockets of your BCD when you collect it, in case there are extra weights in them. It’s quite possible that the previous user had bouyancy problems, in which case his or her instructor may well have put an extra kilo of weight in the pockets to help them. If they forgot to remove that weight, it could upset your own diving.

Second, if you’re assigned an instructor or divemaster to follow, make sure you know what they look like. That sounds trivial, but if you’re on your first open water dive, it’s quite possible to forget that, for example, your instructor is bald, and discover that the person you are following is not. Yes, I did that! Some instructors make a point of having mis-matched fins, one blue and one yellow, for example. This makes them easy to identify underwater.

Such mistakes are probably very rare, and you should not be put off from diving because I mention them. For divers of all levels, the Maldives has a lot to offer. There’s the big stuff, sharks, mantas, morays, fish and corals, which are always fun to see. But there’s also a lot of small stuff hidden away, and it’s a great incentive to improve your diving. Many of the smaller creatures live in small holes or under ledges, and you need good bouyancy control to be able to approach them without disturbing them or damaging the reef. I personally prefer looking for the smaller creatures, and find that diving slowly and close to the reef is more relaxing than swimming hard to cover a lot of ground.

The Maldives is a place where strong currents can occur, and some of the best diving is to be had where the current runs fast. Small fish come out from the reef to feed, big fish come to feed on the small fish, and corals will sometimes open, even during the day. Fighting against a current is hard work, so unless you know how to stay close to the reef and minimise your exertions you may soon find you are using up your air too quickly, or that you have reached the end of the reef early.

Either way, your dive will be over, and you will be back on the boat while other people are still enjoying their dives. Of course, if you’re going to stay close to the reef, you need to be very careful not to damage it, so you need to know what you are doing. The dive-centre staff will be happy to give you tips (thank you Robert Schneider!), and you should take every opportunity to talk to them and learn from them.

Even if you are certified to dive on your own, you may want to follow the divemaster or instructor, at least for a few dives. They will know the best places to look for small creatures and interesting things, which can help you learn how to find things for yourself. If you are more confident, heading out on your own away from other divers (but always with your buddy!) means there will be less people near you disturbing the animals you are looking for, which may make them easier to find.

One thing you really must try, even if you are a beginner, is a night-dive. The boat will leave around sunset, and you enter the water as twilight descends. You can still see where you are going and get your bearings, so there’s no difficulty in orienting yourself. Soon, the light disappears, and you and your buddy are left with your torches to explore a reef that looks very different to its daytime appearance. I once dived on the reef at Thiladhoo, in Baa atoll, in the afternoon and night of the same day. They could have been two completely distinct reefs, things were so different. Oh yes, I thoroughly recommend night-dives!

If you are planning to visit the Maldives in winter, you should consider getting flu vaccinations well before you fly. The last thing you want is to be paying 5-star rates to stay in bed with a cold, and you certainly can’t dive with a congested nose.

For a diving holiday, you will need at least two weeks, one week is just too short. You need a day to get over the jet-lag of getting there, and you can’t dive for 24 hours before your return flight, so a week just wouldn’t give enough time to dive.

More importantly, once you’ve dived in the Maldives, you’ll want to do it again. Even as you board the plane to come home, you’ll be trying to figure out when you can come back again. Take my word for it. Or better yet, don’t take my word, go there and find out for yourself!

Zemanta recently won second prize in the Change the Web Challenge for web-innovation, and they are giving away the prize money to whichever charities most people vote for. Zemanta, in case you haven’t heard of it, is a tool for suggesting content (photos and links to related articles) to add to your blog, based on whatever you’ve already typed in. It works for WordPress, Blogger, TypePad, and a wole bunch of other blogging platforms. If you’re using FireFox, you can run it as a plugin in your browser, so you don’t need to install it on your blogging host.

You can try the interactive demo on their website. Just cut and paste the text from one of your old blog posts to replace the sample text they put there, hit the ‘run demo’ button, and see what pops out. I’m willing to bet you’ll be impressed. Oh, and did I mention it’s free?

So, Zemanta, congratulations on winning that prize, and thank you for a great tool. Now on to my vote. I would like you to donate to the Marine Conservation Society UK, to help them with the work they do. The Marine Conservation Society UK is involved in a large number of activities around the British coast, and beyond. Coastline is something that Britain has lots of, so it’s an important charity!

They actively campaign to persuade the UK government to establish Marine Protected Areas, and encourage people to get involved at several levels, such as reporting sightings of basking shark, turtles, pink sea fan and many other creatures that can be seen in the seas around Britain. They encourage divers to become better observers by learning about their marine environment so they can in turn provide more accurate and useful observations to help drive conservation efforts.

They have a lot of educational resources for schools and project-suggestions for college students. They even organise coral reef surveys in the Maldives for recreational divers.

For the less well-heeled visitor to the British seaside, they monitor the state of beaches and publish an annual guide to the best beaches in the UK. This is not just cosmetic, many beaches pose health risks for swimmers, so knowing where to go is important. To help you get there, they even provide downloadable maps for your in-car GPS. How’s that for service!

Zemanta have had over 50 charities proposed to them so far, and will donate to the five that get the most votes. If you think that the Marine Conservation Society UK deserves a donation from them, all you need do is blog about it yourself, to add your vote.

This blog post is part of Zemanta’s “Blogging For a Cause” campaign to raise awareness and funds for worthy causes that bloggers care about.

Verena Wiesbauer is a marine biologist, with particular knowledge of coral propagation and restoration techniques. In March 2009, she gave a lecture to the Maldives Science Society. Someone in the audience filmed it, and was kind enough post it on google-video, so now you can all enjoy watching “The Coral Reefs of the Maldives” as I have.

I learned a lot from this presentation, it’s very educational and entertaining. There’s a ‘pop-quiz’ early on, in which you are asked to identify what type of plant or animal is being shown. I pride myself on having correctly recognised Coriocella (though I did have to look up how to spell it), having seen them in Baa Atoll a few years ago.

Verena tells us that the Maldives sits on a volcanic chain which forms the basement of the islands. These volcanoes were active around 67 million years ago, so around the time the dinosaurs were dodging asteroids. Coral first started growing on these volcanoes some 55-57 million years ago. Since then, sea-level has changed several times, most recently after the last ice-age when it rose dramatically as the ice melted and retreated. The Maldivian atolls were flooded at that time, and the upward growth of coral only succeeded in creating islands around 3000-4000 years ago. The actual coral growth in the Maldives now forms a layer about 2000 metres thick. That’s a lot of coral!

Having shown us some of the animals that live in and around the Maldivian reefs, Verena goes on to tell us about some of the problems that are affecting the reefs today. Beach erosion is a serious problem. With two monsoons each year, coming from different directions, it is natural for the sand to shift from one side of an island to the other during the year. In 2000, half of the islands were sufferring from beach erosion. There are simple measures that the Maldivians can take to protect themselves from the worst effects of such erosian, such as not building too close to the shoreline and using sand and aggregates imported from India for construction (instead of dredged from their own reefs).

They can also protect the islands by protecting the living reef. A living reef will protect against beach erosion by reducing the force of the waves as they come inshore, a dead reef will soon be destroyed by the waves and offer little or no protection. A reef needs at least 50% live coral-cover to provide adequate protection, few of the Maldivian reefs have that at this time.

There are other threats to the reefs too. The Maldivians themselves generate a lot of waste, and they have nowhere to put it. The island of Thilafushi is a municipal landfill, and there is concern that all sorts of toxic waste from it may leak into the ocean and harm the environment.

Discarded fishing-lines cause a lot of damage too. One horrible slide in the presentation shows a turtle that became entangled in a fishing-line while it was young. It survived, and grew up with the fishing-line constricting its growth. I’ve never seen a turtle with an hour-glass figure before, and I hope I never do again.

Another major cause of damage to coral reefs is the tourist industry. Divers, even experienced ones, can cause a lot of damage. Verena gives a personal account of diving with tourists who lay down on the reef to watch sharks, and who were upset with her for not doing the same because she might scare the sharks away! I’ve seen divers who allowed their diving lamps to trail along the bottom of a reef like a wrecking-ball while they were concentrating on getting closer to a few manta-rays nearby.

Not surprisingly, divers with cameras cause more damage than those without, they’re focussed (literally!) on what they’re looking at, not what they’re bumping into. Diving from shore causes more damage than diving from boats, and night-diving causes more damage than diving during the day. Even without direct physical contact, reefs can be damaged by divers who kick up sediment with their fins, smothering the corals they have paid so much to see.

It’s not only divers, but also snorkellers, that damage reefs. Snorkellers will often stand on the reef to adjust their equipment, and can do a great deal of damage by careless contact. Verena cites a paper by W.R.Allison in 1996 which showed that snorkellers can can do an immense amount of damage in a short period of time.

Verena says that the dive-schools could give better briefings, for both divers and snorkellers. Her own experience is that people appreciate being reminded of the simple things they can do to reduce their personal impact. I know some dive-schools don’t like to impose on their divers, so will not mention such things in their briefings. You can always invite them to say something when they ask if there are any questions. Put your hand up and say “I have a question, do we have to be careful about what we touch on this dive?”. It’s worth a try!

Dive-schools should also respect the ‘carrying-capacity’ of dive-sites, and not visit them too frequently, so they have time to recover from each invasion. This is a particular problem in the Red Sea, where many reefs are seriously degraded by divers. Of course, that’s not easy when there are many dive-schools competing to take people to the most popular sites.

Individually, divers can take steps to reduce their impact even more. Those of you that dive with PADI can take the Peak Performance Buoyancy course (other organisations probably have something similar). You’ll find you dive better (i.e. use less air, are more relaxed) and do less harm to the reef because you have more control. You’ll see more on each dive, too, because you will spend less time fighting with your equipment and frightening fish with your thrashing, and more time looking around.

Tourism can also be a positive force. wildaid.org invented the slogan “When the buying stops, the killing can too“, and used it in their campaign against shark-finning. You can kill a shark for its fins only once, but if you leave it alive, tourists will pay again and again to come and see it when they dive.

Verenas’ presentation has an optimistic tone, she clearly loves her work. There are things that can be done to help the reefs, and she mentions some of the many restoration and conservation projects in the Maldives. She herself has assisted in the creation of an artificial reef at Huvafenfushi. I’ll end this post with a quotation she gave at the beginning of per presentation. It’s from Baba Dioum, a Senegalese environmentalist or poet (depending on who you ask):

It would be good if people were taught more about the world we live in today.

Charles Darwin was born 200 years ago, on February 12th 1809. Possibly the most famous scientist ever, his fundamental and beautiful theory of evolution has stood the test of time. Darwin formed his theory as a result of his observations during the voyage of the Beagle, but it was many years from then until he actually published his ideas.

It is less well-known that, in the same voyage, Charles Darwin produced another theory of evolution, not of life but of coral reefs. The formation of coral reefs was a matter of some debate at that time, in fact, one of the mission objectives for the Beagle voyage was to study their nature. Darwin’s theory was published in his book The Structure and Distribution of Coral Reefs in May 1842, some 6 years after the Beagle came home, and 17 years ahead of his more famous work, On the Origin of Species.

Darwin’s theory of coral reef formation is all the more remarkable for having been thought out completely before he had ever seen a reef. In his own words:

Such a statement could imply that Darwin was biased in his views, and it would be natural to believe that he sought only such evidence as supported his theory. That this is not the case becomes apparent on reading the book. Darwin was a meticulous and thorough observer, seeking as much information as he could from a wide variety of sources. The appendix of his book, fully one third as long as the main text, contains a detailed description of a large number of coral reefs, all of which he examined in the light of his theory. The book also includes a map of the world, showing the locations of all these reefs.

Darwin accumulated such a wealth of information on reef structure and history that his theory emerges as almost an inevitable consequence. He tests his theory for its ability to explain the features of a variety of reefs and atolls, as well as the distribution of different types of reef in different parts of the world.

The theory states that, in conditions where coral can survive, it will form fringing reefs (reefs close to shore) around islands and other land masses. If that land is rising over time, the reef will grow outwards as the land rises, and the fringing reef will be stable. If the land is neither rising nor sinking, the reef will expand outwards over time, forming a barrier reef (a reef enclosing an island, at some distance from it). If the land is subsiding, the coral will grow upwards in consequence, and eventually a barrier reef, then an atoll (a more or less circular reef with no land enclosed), will be formed.

Darwins evidence was drawn from a great many sources. Using plumb-lines, he measured the depth of the sea around many reefs, at different distances from the reef. This showed him a slope too steep to be consistant with reefs being formed on volcanic craters, as was thought at the time. By using soft wax on the bottom of the lead weight, he was able to gain clues to the nature of the sea-bottom. Sand and other fragments would become embedded in the wax, hard rock would simply leave impressions in it. This helped him deduce the limits of depth at which coral can grow.

Some of his soundings were as deep as 7200 feet (2160 metres), so he was definitely doing more than just scratching the surface!

Darwin noted the importance of sediment, both in forming islands as it is washed up by the waves, and in inhibiting coral growth by smothering corals or preventing them from getting a good anchorage inside lagoons. He dissected several parrotfish to investigate their stomach contents, verifying that they do indeed eat coral, pass it through their bodies, and excrete fine sand which contributes to the sediment.

Darwin saw that the types of coral on the outer margins of a reef were different from those inside the lagoon. On the outside of the reef, larger corals grow well. Inside the lagoon, corals are less vigorous. This is largely because the outside margins have the full force of the current, bringing nutrients to the coral. Inside the lagoon, the currents are weaker, so the coral does not grow as fast. He was able to identify some of the corals in the outer margins by walking the beaches after storms and looking at the new types of coral fragments that were washed ashore.

Darwin also investigated the channels that cut through many reefs. He saw that the channels tend to form on the side away from the current. Channels facing the current would tend not to accumulate as much sediment as those on the other side, so corals could take hold and grow into the channel, closing it up over time.

Darwin was able to deduce the growth-rate of corals from many sources. He used accounts of one ship that grew a 2 foot (60 cm) thickness of coral on its hull in 20 months, as well as information about ship-anchors that had become embedded in reefs over the years, and direct observations from other naturalists.

Having been led to his theory by his intuition, and having backed it up with observation, Darwin then goes on to test his theory in many ways.

Many atolls have deep lagoons, which can be best explained by upward growth at the rim while the whole of the land subsides. If the land were rising, there is no reason for the rim to rise faster than the interior, so a deep lagoon would not be formed.

Many atolls occur in the open ocean, rising steeply from depths beyond which coral cannot grow. There is no obvious explanation that could cause such a reef to rise from the depths, but if the reef were growing upwards at the same pace as the land is sinking, these isolated reefs are to be expected.

There are smaller, irregular reefs in many places, and these too can be accounted for. As a land-mass sinks and its peaks become separated islands, linear reefs may form between them, which may persist as irregular reefs long after the land subsides.

The larger reefs of the Maldives appear to be slowly separating into smaller reefs. Darwin accounts for this by noting that particularly large atolls may be breached by wide channels. Coral can grow at the edges of these channels, and if the channel is wide enough the coral growth may eventually cut the atoll in two.

Fringing reefs occur near land that is stable or rising, but atolls and barrier reefs are formed where the land is sinking. The map shows clearly that fringing reefs tend to be apart from atolls and barrier reefs. For the same reason, volcanoes should not often be close to atolls and barrier reefs, and indeed they are not.

Darwin’s theory of reef formation and development, like his other theory of evolution, has stood the test of time. Unlike his other theory, it was well received by the scientific community and the public from the moment it was published. If it had been the only thing he published, it would still be an important work. Darwin produced many other books and papers, you can find his complete works online at darwin-online.org.uk. I think I’ll read a few more, though the one on fossilised barnacles will not be near the top of my list. You can read more about Darwin and his work at Blog for Darwin, the site that inspired this post.

Happy birthday, Charles Darwin.