Tanks for Everything

Coral reefs are dying off around the world. To further his work on the issue, Dr. Stephen Palumbi, director of Stanford’s Hopkins Marine Station, Pew Fellow in Marine Conservation, and OWOO Science Advisor is in American Samoa and the Cook Islands in search of the corals most likely to survive. This is the eighth in a series of special reports from the field that will continue throughout his team’s three-week expedition.

The stress tank had finally been reconstructed with its new voltage converter, and then a deluge soaked everything. I was drying it all in the oven, hoping to bring it back to life as my daughter and dive buddy Lauren gave me quizzical looks. A few hours later the tank was re-built and functioning again, minus one chiller.

It was three days till the end of our Cook Island trip, and data finally started to flow. I tested small coral fragments collected from a back reef area near Black Rock in eastern Rarotonga; they survived 32 degrees C (89.6 F). I was surprised because the area is awash in waves and does not heat up much above 28 degrees C (82.4 F). The samples began to show effects when the stress tank hit 33 degrees - and could not survive even a brief exposure to 34 degrees.

Here is a glimpse of the wave-washed area.



On Ofu most corals were at least partially resistant to 34 degrees C, and were stress free at 33 degrees for 2 hours. Ofu is quite a bit closer to the equator than Rarotonga and sees warmer water, sometimes above 34 C. It turns out coral heat resistance generally follows geography: an equatorial area has about 2 degrees higher resistance than one further from the equator. Of course this is just one comparison from a pilot experiment, and there may be other factors that account for the differences between the islands. But the results mirror some early studies done in the 1970s in a few places, and this whets our appetite for more information.


I want to conduct stress tank studies as close to the equator in the Cook Islands as possible and move south island by island till we get to the cooler waters of Rarotonga. The islands are far apart though, and only one of the northern group, the black pearl farming atoll of Manihiki, has regular air service.

We talked with master Cook Island navigator Tua Pittman about a slower but better expeditionary route. A fleet of newly made Polynesian voyaging canoes, under Tua’s guidance and built by the Okeanos Foundation, is making it’s way towards Samoa for the 50th anniversary of Samoa independence in June. The canoes carry young Polynesians under the guidance of a master navigator; they are vessels for the preservation of ancient Polynesian culture, and it’s knowledge of navigation. After the Festival of Pacific Arts in the Solomon Islands in August, one of these canoes will return home to Rarotonga. Tua suggested a route that could take a canoe, equipped as a science lab and classroom, along the Cook Island chain from south to north. Along the way, coral scientists could test the reefs and sample parts of the world that have literally never been visited by science. And for the inhabited islets, we could bring educational materials, teachers and the old art of traditional Polynesian navigation. A hybrid of modern science and ancient Polynesian worlds.

Perhaps all this was born of too much enthusiasm for long conversations with people on Rarotonga: Tua and Teina Rongo and Edwin Pittman, watching the sun set on the lagoon behind the reef and imagining the value of knowing where in this dusting of coral islands the strongest corals live.

The Cook Islands is designing the world’s largest marine protected area, and may be poised to set up a protected zone in the southern islands that could be an important refuge for corals when the oceans heat up due to climate change. The waters there are now a bit cooler than more equatorial islands, and our tanks show the corals can withstand water a bit warmer than usual. A protected area that preserves reefs from local harm and houses heat-toughened corals might be a place corals could survive the next century. To have Polynesian corals and culture survive together would be a fabulous goal, and a journey worth taking.

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