Field Trip: Can Corals Survive Warming Ocean Temperatures? [Slide Show]

Data from remote coral reefs in the central Pacific suggest that, although many corals are harmed by heat, certain kinds can adapt to warmer water

18 While we were off on our trip to Marakei and Butaritari, a high tide broke a seawall around the rest house where I stay in Tarawa. A healthy outer reef is critical to protecting the shoreline from erosion by waves and tides, especially given the rapid rate of sea-level rise. Simon Donner
17 Toaea and Tonana hand-line for tuna on the ride home during a typical afternoon storm. Despite being only 160 kilometers north of Tarawa, Butaritari receives three times as much rainfall. Most days at sea feature at least one period of torrential rain and strong winds. Simon Donner
16 Colonies of massive Porites corals of this size (1.8 meters high), and hence older age, are rare in the Gilbert Islands. On a previous field trip, we extracted long cores from such Porites in order to reconstruct past coral growth and climate. Toaea and I mark the location of this large Porites in northern Butaritari, just in case we conduct another coring project in the future. Simon Donner
15 Breakfast the next day: rice, two types of tuna, salted fish and cassava. Simon Donner
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14 With translation provided by my colleague Tuake, I present the results of our past research to the Butaritari community in the Catholic church meeting house. We brought a projector from Tarawa and made a screen out of a sheet and a couple pieces of furniture. Tonana Tioti
13 The end of the day provides a chance to dry gear and refill dive tanks outside the rest house in Butaritari. Simon Donner
12 We mark the location of temperature loggers with pink surveyor's tape. Loggers need to be hidden to guard against theft or accidental damage by curious spear fishermen, but not hidden so much that we can't find them again. Toaea Beiateuea
11 For long-term data, I install a small temperature logger underneath a coral rock. Toaea Beiateuea
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10 Here I record the diameter of individual coral colonies along an underwater transect. Toaea Beiateuea
9 These various branching corals of the genus Acropora, common in the past on the Butaritari outer reefs, tend to be sensitive to heat stress. Here, a mix of colonies surrounds a large Acropora table (red-gray) that was partially killed by heat stress during one of the recent El Niño events. Simon Donner
8 Valuable, exploitable species like this giant clam (one meter wide) are more common on the outer atoll of Butaritari than elsewhere in the Pacific. Simon Donner
7 On Marakei Atoll I provide an offering (tobacco, the green package inside the statute) to the ancestral gods, customary for first-time visitors to an outer atoll. Simon Donner
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6 A lot of time and energy doing research in remote ocean locations is spent simply negotiating transportation, managing underwater equipment, making sure boats don't sink, coordinating dives and trying to not get hurt. Here we load gear onto Te Tia Akawa (the Fisherman), a research vessel operated by Kiribati's Ministry of Fisheries and Marine Resource Development, for an overnight trip to Marakei and Butaritari. Simon Donner
5 The "weedy" coral Porites rus dominates the outer reefs in much of South Tarawa. We suspect that water pollution and frequent heat-stress events have allowed this more heat-resistant and less physically complex coral to outcompete other species. Simon Donner
4 With no winch available, my local colleague Timon and I use an improvised system to deploy an instrument that collects data on water temperature, salinity and quality at different depths. Simon Donner
3 Much of Kiribati consists of narrow strips of land, such as here in southern Tarawa Atoll. In the foreground is a shallow lagoon; in the background is the open ocean. Simon Donner
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2 Data we took in May across Kiribati's Gilbert Islands (right) will tell us how various types of coral are faring, compared with data taken over the past seven years. Simon Donner
1 Acropora coral in Tarawa Atoll in the central Pacific Ocean can thrive or die depending on the water temperature, which is likely to rise as global warming continues. White "bleaching" generally indicates that a coral is dying from within. Simon Donner