19 April 2010
A sampling station in the crystalline waters of Gan island, one of the last island chains south of the Maldives. Our scientists cheer up after 2 days of constant rain.
Tara’s orange prow follows in the wake of another expedition that crossed the Indian Ocean over a century ago – the HMS Sealark, led by the zoologist John Stanley Gardiner. In 1905, this lively Englishman sailed around islands and atolls to catalogue the marine flora and fauna. He was one of the first to study the symbiosis between coral and micro-algae – the same micro-algae found in plankton. Called zooxanthellae, these organisms are capable of photosynthesis. They create organic matter using sunlight, and nourish the coral in exchange for shelter and protection.
Gardiner was also interested in the way coral reefs formed…and he wasn’t alone. Our mentor Charles Darwin, whose round-the-world voyage inspired the Tara Oceans Expedition, had an intuition in the 1830s about the geological history of atolls. He wrote in his journal: “General laws must determine the marked difference between the reefs fringing the coasts, and those emerging from the ocean depths in the form of rings, distant one from another. We have demonstrated that by a sinking movement, the first category of reefs gradually evolves into the second, and into other even more remarkable structures.”
Not bad Mr. Darwin! Modern science has given us a more precise understanding of the mechanism of reef formation. It all begins with a volcano emerging in the middle of the ocean. When the volcano cools off, it becomes an island, and then a ring of coral grows in the shallows all around its coastline. At this stage, two changes can happen: the level of the sea rises, or the ancient volcano gradually collapses. Water then penetrates between the fringe of coral and the land, forming a lagoon. The third stage suggested by Darwin is the atoll. The remains of the volcano disappear completely under the sea, leaving a ring of coral barely emerging at the water’s surface.
We’re hoping to add to the scientific heritage of these historic discoveries during our two weeks of research around St Brandon. Don’t believe those photos of paradisical dives: we’re here only to serve Science!