November 07, 2012
Coral surveying in a cloud of fish. Photo by: Joshua Feingold.
The Galapagos are a tough place for coral to grow. Directly on the equator in the eastern Pacific, the islands sit at the intersection of five major ocean currents, both warm surface currents and cool, deep currents. The result is a marine climate that changes rapidly from island to island and season to season—not an ideal situation for organisms that are especially sensitive to changes in water temperature.
Nonetheless, in the 1970s researchers discovered that numerous places in the 16-island archipelago did have coral, some of which had accumulated into reefs, especially in the warmer waters around the northernmost islands. Then, the unusually strong 1982-83 El Niño climate event brought abnormally warm waters that killed over 90% of corals in parts of the Galapagos. (Warm waters cause corals to lose their crucial symbiotic algae, which causes bleaching and leaves them more prone to disease.) Another strong El Niño in 1997-98 threatened to seal their fate, but some managed to survive.
Pink spots disease on coral at Wolf Island, Galapagos. Photo by Andy Bruckner.
"The Galapagos offered a unique field laboratory to help us better understand how temperature extremes and increasing acidity will affect the survival and growth of reef building corals in the future," says Andrew Bruckner, chief scientist for the expedition.
Overall, the team found hopeful signs of coral recuperation at three northern islands: Marchena, Wolf and Darwin. "That's encouraging," says team member Peter Glynn, co-author of the 1983 treatise. "The southern islands, though, are showing very little in the way of recovery to pre-1983 levels. On the other hand, the most common large corals were surprisingly abundant in the central and southern islands, even though they weren’t aggregated into reefs."
Team member Derek Manzello of NOAA was looking at how the relatively higher levels of carbon dioxide (CO2) in the waters around the Galapagos affected coral growth rates. The islands owe their wealth of marine life to the deep, cold currents that bathe them in nutrients brought up from the ocean depths. These same currents also bring high amounts of CO2, a byproduct of decomposition. This situation could make the islands a window into the future of reefs around the world, since about a quarter of the CO2 we’ve produced in the past century has ended up in the ocean, where it makes the waters more acidic. Acidic waters weaken reefs by interrupting the creation of calcium carbonate, the substance that provides their hard structure.
Manzello found CO2 levels in the northern islands were about 40 percent higher than they were in preindustrial times, based on samples taken from ice cores, which is similar to levels researchers are finding throughout the tropics. In comparison, CO2 levels around the southern islands have roughly doubled since the industrial revolution, which could explain why corals there are not recovering as well as they are farther north.
Another member of the expedition, Iliana Baums of Penn State University, examined how two similar species of reef-building coral reproduce, and how this depends on the reef community surrounding them. Porites lobata reproduces sexually, by releasing sperm and/or eggs into the water, which are carried off to found new coral. Its identical-looking relative Porites evermanni often reproduces asexually, which can happen when pieces break off—in its case, from certain species of triggerfish biting off pieces of coral in search of mussels that live inside—and form new corals nearby. Asexual fragmentation is limited to the immediate vicinity, while sexual reproduction can "reseed" new coral communities over much longer distances. In the Galapagos, the mussels are common but the right species of triggerfish isn’t. Baums found that fragmenting Porites evermanni doesn’t grow there as often, possibly because they need the fish to reproduce. So climate change could affect the coral not only by raising the water temperature, but also by how it affects the mussels and fish directly.
The Global Reef Expedition is a project of the Khaled bin Sultan Living Oceans Foundation in Landover, MD. The goal is to survey and map remote coral reefs, often in countries who aren’t able to do it themselves, to help identify high-priority sites for protection. Local scientists team up with researchers brought in by the foundation, which assumes all the costs. All data and maps are turned over to the host countries at the end of each mission.
The expedition started its 6-year mission last year in the Caribbean, surveying reefs in the Bahamas, St Kitts & Nevis, Jamaica, Navassa, Colombia and the Galapagos. The Golden Shadow is currently in the South Pacific, and will work its way west around the globe until 2017.
A sea lion plays coy. Photo by: Joshua Feingold.
Derek Manzello drills a coral core. Photo by: Joshua Feingold.
Great Barrier Reef loses half its coral in less than 30 years
(10/01/2012) The Great Barrier Reef has lost half of its coral cover in the last 27 years, according to a new study released today in the Proceedings of the National Academy of Sciences (PNAS). Based on over 2,000 surveys from 1985 to this year the study links the alarming loss to three impacts: tropical cyclone damage, outbreaks crown-of-thorns starfish that devour corals, and coral bleaching.
Coral diversity off Madagascar among the world's highest
(09/24/2012) The western Indian Ocean, especially the waters between Madagascar and mainland Africa, may be among the world's most biodiverse for coral species, according to a new study in PLOS ONE. Conducting dive surveys in the region for nearly a decade, David Obura with the Coastal Oceans Research and Development in the Indian Ocean (CORDIO) identified 369 coral species in the western Indian Ocean and predicts there may be nearly another 100 unidentified. If so, this would make the region as biodiverse as the Great Barrier Reef, but still behind the Coral Triangle which has over 600 species.
Coral reefs in Caribbean on life support
(09/11/2012) Only 8 percent of the Caribbean's reefs today retain coral, according to a new report by the International Union for Conservation of Nature (IUCN). With input and data from 36 scientists, the report paints a bleak picture of coral decline across the region, threatening fisheries, tourism, and marine life in general.
Deforestation is killing Madagascar's coral reefs
(09/05/2012) Sediment carried by rivers draining deforested areas in Madagascar is smothering local coral reefs, increasing the incidence of disease and suppressing growth, report new studies.
Coral calcification rates fall 44% on Australia's Great Barrier Reef
(09/04/2012) Calcification rates by reef-building coral communities on Australia's Great Barrier Reef have slowed by nearly half over the past 40 years, a sign that the world's coral reefs are facing a grave range of threats, reports a new study published in the Journal of Geophysical Research - Biogeosciences.
Strangest island in the Caribbean may be a sanctuary for critically endangered coral
(07/16/2012) Don't feel bad if you‘ve never heard of Navassa Island, even though it's actually part of the U.S. according to the Guano Islands Act of 1856. This uninhabited speck between Haiti and Jamaica, barely bigger than New York City’s Central Park, has a bizarre and bloody history—and may be a crucial refuge for endangered coral in the Caribbean.
2,600 scientists: climate change killing the world's coral reefs
(07/10/2012) In an unprecedented show of concern, 2,600 (and rising) of the world's top marine scientists have released a Consensus Statement on Climate Change and Coral Reefs that raises alarm bells about the state of the world's reefs as they are pummeled by rising temperatures and ocean acidification, both caused by greenhouse gas emissions. The statement was released at the 12th International Coral Reef Symposium.