Song for Jasmine

Anthias on the reef

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!

soft 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.

gorgonian sea fan

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.

Coco-palm encourages tourists to preserve the environment

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.

Coral Island in the Maldives

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.

Blogging for Darwin

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.

Island and Atolls

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.

Maldivian reef

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.