Biodiversity contrasts of the Great Barrier Reef

© Vincent Hilaire - Fondation Tara Expéditions

Scientific dives restarted for this second year of the Tara Pacific expedition and the sites observed on the Great Barrier Reef are very different. If Heron Island was an earthly and underwater paradise, sampling stations such as Paul Reef and now U.N. Reefs do not have the same biodiversity. A little more than 300 kilometers separate these 3 coral reefs, totally different from one another.


photo 3_ prelèvement autour de lune des trois espèces de coraux_Vincent HilaireSampling of one of the three coral species selected for Tara Pacific research. © Vincent Hilaire / Fondation Tara Expéditions


After sampling these 3 diving sites on the Great Barrier Reef, another station is planned for tomorrow morning. Christian Voolstra, our lead scientist until we reach Noumea, is satisfied with our results: “We’re very pleased, everything went really well. Tara is truly operational. Every time we found what we were looking for, even when there wasn’t much biodiversity. It’s the purpose of the Tara Pacific expedition to compare reefs, even when they’ve become depleted”.

At Heron Island, the reef was of exceptional quality and healthy. Biologists found at the selected site a normal presence of predators such as sharks, and many different corals, even if they noticed a few infections on polyps. In addition, there was no trace of recent or past bleaching.


2- photo 4_ Paul Reef vue de drone_ Vincent HilairePaul Reef from the sky. © François Aurat / Fondation Tara Expéditions


Barely a day of navigation later, the turquoise waters at Paul Reef offered a stark contrast. After returning from his dive, François Aurat, deck officer since the beginning of the expedition, shared his impressions: “You can’t find anything underwater, there’s almost no life left. I don’t recall ever seeing such desolation”. According to Christian Voolstra, “What we are seeing here is the result of a long process. Most of the colonies died a long time ago. As a result, there’s no more fish either”.

Two days later, at U.N. Reefs, another scenario is unfolding around the coral heads. In waters of exceptional clarity but subject to strong currents, we dived early in the morning on Sunday, September 3. Six meters underwater, we discovered an intermediate situation between that of Heron Island and Paul Reef, healthy colonies side by side with stretches of dead corals. There again, the lifeless corals didn’t reveal any recent bleaching, but an old event. This reef therefore provides a mixed diagnosis.


UN ReefReefs very mixed with many coral debris at the bottom at U.N. Reef. © Vincent Hilaire / Fondation Tara Expéditions


Tara Pacific is Christian Voolstra’s second scientific research campaign on the Great Barrier Reef since the beginning of his career: “What we’ve seen over the past few days actually looks better than what I expected. We’re currently south of the largest reef in the world where damages are not as extensive as in the north”.

According to Chris — Christian’s nickname aboard the schooner — our last diving site on the Great Barrier Reef should be of similar quality to that of Heron Island. After this last station, Tara will sail to Mackay, on the Australian east coast, to complete the customs formalities to leave this country.


The Taranauts will then resume their journey, eastward this time, to Chesterfield Islands first, then New Caledonia.


Vincent Hilaire

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