Smithsonian Science » climate change

Heavyweight trees are forest champs at sequestering carbon

John Barrat — Thu, 03 May 2012 16:36:41 +0000

Big trees three or more feet in diameter accounted for nearly half the biomass measured at a Yosemite National Park site, yet represented only one percent of the trees growing there.

This means just a few towering white fir, sugar pine and incense cedars per acre at the Yosemite site are disproportionately responsible for photosynthesis, converting carbon dioxide into plant tissue and sequestering that carbon in the forest, sometimes for centuries, according to James Lutz, a University of Washington research scientist in environmental and forest sciences. Lutz is lead author of a paper on the largest quantitative study yet of the importance of big trees in temperate forests being published online May 2 on PLoS ONE. The research was funded by the Smithsonian Center for Tropical Forest Science.

Image right: A handful of large-diameter trees per acre, such as these incense cedars, together with remains of big trees like the three-foot-wide white fir snag and downed debris account for half the forest biomass at a Yosemite National park study site. (Image by James Lutz)

“In a forest comprised of younger trees that are generally the same age, if you lose one percent of the trees, you lose one percent of the biomass,” he says. “In a forest with large trees like the one we studied, if you lose one percent of the trees, you could lose half the biomass.”

In 2009, scientists including Lutz reported that the density of large-diameter trees declined nearly 25 percent between the 1930s and 1990s in Yosemite National Park, even though the area was never logged. Scientists have found notable numbers of large trees dying in similar areas across the West.

The new 63-acre study site is one of the largest, fully-mapped plots in the world and the largest old-growth plot in North America. The tally of what’s there, including the counting and tagging of 34,500 live trees, was done by citizen scientists. The site is part of the network of the Smithsonian Center for Tropical Forest Science, a global network of 42 tropical and temperate forest plots including the one in Yosemite.

Image left: Washington State University’s Mark Swanson pulls a tape tight around a 4-foot-wide sugar pine, one of the 34,500 live trees counted and tagged for long-term study in a Yosemite National Park study plot. (Washington State University)

One implication of the research is that land managers may want to pay more attention to existing big trees, the co-authors said. In some younger forests that lack big trees, citizens and land managers might want to consider fostering the growth of a few big-trunked trees, Lutz added.–Source: University of Washington.

Global forest science research center moves from Harvard to the National Museum of Natural History, Washington, D.C.

John Barrat — Wed, 02 May 2012 14:32:22 +0000

In May, the Center for Tropical Forest Science-Smithsonian Institution Global Earth Observatory is moving from its headquarters at Harvard University to the Smithsonian’s National Museum of Natural History in Washington, D.C. The move enhances coordination efforts for the 46-plot research network, which partners with more than 75 institutions in 21 countries, including the Smithsonian’s Natural History Museum, the Smithsonian Conservation Biology Institute and the Smithsonian Environmental Research Center.

CTFS-SIGEO is a global network of forest research plots committed to the study of tropical and temperate forest function and diversity. The multi-institutional network includes plots across the Americas, Africa, Asia, and Europe, with a strong focus on tropical regions. Ecologists at the Smithsonian Tropical Research Institute established the first forest dynamics plot on Barro Colorado Island in the Panama Canal in 1980.

Image left: Daniel Johnson, a biology graduate student at Indiana University, measures the diameter of a white ash tree in the University’s Lilly-Dickey Woods. The 550-acre woods were recently added to CTFS-SIGEO’s global network of forest research plots. (Photo by F. Collin Hobbs)

Stuart J. Davies, CTFS-SIGEO director and senior staff scientist at the Smithsonian Tropical Research Institute, will make the move along with David Kenfack, CTFS-SIGEO Africa Program coordinator. Davies sees the need for increased presence at the Smithsonian in Washington, D.C. as the network continues to build partnerships within different Smithsonian units.

The scale and intensity of the CTFS-SIGEO research program remains unprecedented in forest science. Scientists monitor the growth and survival of about 4.5 million trees of approximately 8,500 species in 21 different countries. The work aims to increase the scientific understanding of forest ecosystems, guide sustainable forest management and natural-resource policy, monitor the impacts of climate change, and build capacity in forest science. Most recently CTFS-SIGEO added the Lilly-Dickey Woods–a 550-acre forest in Brown County Indiana that is a research and teaching preserve for Indiana University–to its network of forest research plots.

Because of its extensive biological monitoring, unique databases, and the expertise of its partners, CTFS-SIGEO enhances society’s ability to evaluate and respond to the impacts of global climate change. Monitoring so many forest plots at once is providing a comprehensive, yet locally detailed perspective on how the world’s forests are being transformed by global change. Research on tropical forest dynamics continues, but is joined by new initiatives studying carbon fluxes, temperate forests, ecosystem services, and biodiversity. CTFS-SIGEO and its many institutional partners are leveraging huge intellectual horsepower to transform our understanding of forest-ecosystem structure and function. The network has been so successful that the Smithsonian is now planning to extend its system of earth observatories to the near shore marine realm. –Source: The Plant Press, newsletter of the Department of Botany, National Museum of Natural History.

Panda habitat to be lost, shifted by climate change

John Barrat — Thu, 05 Apr 2012 12:51:57 +0000

Fewer than 1,600 giant pandas are left in the mountain forests of central China. Now a new study published in the International Journal of Ecology by scientists at the Smithsonian Conservation Biology Institute at the National Zoological Park, predicts that 16,000 square kilometers of giant panda habitat will likely be lost by the year 2080 as climate change causes panda habitat systems to shift to higher elevations and latitudes.

In other words, less than half of the giant panda’s already decreased habitat will be suitable to sustain them in 70 years. The research team used two different global climate models to make this prediction, taking into account remaining habitat, lost habitat, potential new habitat and current protected areas for giant pandas.

The study also found that habitat fragmentation will likely increase, leading to smaller areas that can support fewer pandas farther away from each other, increasing the risks of inbreeding and population collapse.

“Our research predicts that climate change will substantially decrease the amount of suitable giant panda habitat within the species’ current distribution,” said Melissa Songer, lead author of the paper and an SCBI wildlife ecologist. “But also we may see new areas becoming suitable for giant pandas,” Songer adds. “The question remains as to whether giant pandas will have the capacity and opportunity to shift to new areas.”

In addition to calling for the development of more protected areas that are aligned with climate predictions, the paper emphasizes the importance of creating corridors to reduce fragmentation. The study also has land-use implications, as agricultural land and land near human settlements are unsuitable for pandas.

Photos: Giant pandas at the Smithsonian’s National Zoo.

In addition to Songer, the authors of the panda ecology study from SCBI are Melanie Delion and Alex Biggs. The partnering author is Qiongyu Huang in the geography department at the University of Maryland. Friends of the National Zoo helped fund this research.

Smithsonian paleobotanist Scott Wing discusses ancient global warming & what it portends for the future

John Barrat — Thu, 29 Mar 2012 19:48:54 +0000

New invasive species database allows public to ID marine invaders with a home computer

John Barrat — Mon, 12 Mar 2012 14:53:42 +0000

Mitten crabs, zebra mussels and rock vomit: These and hundreds of other non-native species have invaded coastal regions throughout the United States, often causing dramatic changes to coastal ecosystems and significant economic costs. The Smithsonian Environmental Research Center has now created NEMESIS (National Estuarine and Marine Exotic Species Information System), an online public database to provide key information about the non-native marine species throughout the nation.

Image right: Tunicate Botryllus planus. Colonial tunicates like this one are made of hundreds of tiny zooids that act as a single organism. (Photo: Rosana Rocha, Universidade de Federal de Paraná, Brazil)

The rate of new marine invasions along U.S. coasts has risen sharply in recent decades due to human-aided introductions, often unintentional. Organisms can attach directly to the hulls of ships or be taken up and transported in ballast water (water used by large ships to provide stability and trim during sailing). They can also be introduced with imports of seafood, bait and packing materials. In addition, some species have been deliberately introduced to create new fisheries, though this practice is now very rare. As trade and globalization have increased, so has the opportunity for invasions.

No part of the country is untouched by non-native species. Although most people recognize a few of the common and conspicuous invaders in nearby waters, the full scope of invasions that lurk beneath the water often go unnoticed.

Image left: Chinese mitten crab.

NEMESIS aims to provide comprehensive and synthetic information on hundreds of individual marine species in the continental United States. Created by SERC’s marine invasions lab, the database includes information on how and when invasions occurred, distribution maps and what is known about their impacts. For example, the tunicate Didemnum vexillum (commonly known as D. vex or “rock vomit”) has created serious problems on the West and East Coasts of the United States. This mat-like species grows rapidly and can completely cover aquaculture nets, shellfish beds and sensitive marine environments. The database also includes an interactive map of the U.S., where visitors can search for invaders impacting their own coastlines.

NEMESIS launched March 5 with tunicates, a group that includes the destructive rock vomit. Tunicates, also known as ascidians or sea squirts, are filter feeders that grow on hard surfaces such as docks, rocks or sandy marine sediments. Information for other groups of species will become publicly available over the next year as NEMESIS continues its rollout, starting with crabs, shrimp and crayfish.

Photo right: Tunicate Styela clava, the club sea squirt. It has caused major headaches in Canada, where fouling of fishing and aquaculture equipment cost anywhere 34 to 88 million Canadian dollars per year. (Photo: Melissa Frey, Royal BC Museum, Canada)

NEMESIS was designed in partnership with the U.S. Geological Survey. NEMESIS focuses on invasions in marine and estuarine waters, while the USGS Nonindigenous Aquatic Species database focuses on invasions in freshwater habitats of the U.S. The complementary databases were designed to be compatible, allowing for joint syntheses across marine and freshwater habitats in the U.S.

The NEMESIS database is a long-term and dynamic program that will continue to grow over time. Records are updated regularly as new species are discovered and new research becomes available. For more information on NEMESIS or recent updates, visit the NEMESIS home page and the NEMESIS Interactive Invasions Map.

Largest snake the world has ever seen is being brought back to life by Smithsonian Channel

John Barrat — Tue, 06 Mar 2012 12:58:31 +0000

Slithering in at 48 feet long and weighing an estimated one-and-a-half tons, the largest snake the world has ever seen is being brought back to life. Sixty million years ago, in the mysterious era after the mass extinction of the dinosaurs, scientists believe that a colossal snake related to modern boa constrictors ruled a lost world. With exclusive access to what one scientist called “a once-in-a-lifetime discovery,” Smithsonian Channel(TM) will tell the extraordinary true story in TITANOBOA: MONSTER SNAKE, a two-hour special premiering Sunday, April 1 at 8 p.m. ET/PT.

The startling discovery of Titanoboa was made by a team of scientists working in one of the world’s largest open-pit coal mines at Cerrejon in La Guajira, Colombia. It is a snake that dwarfs the largest anaconda found today, and it has the size and character to challenge T-Rex in the public’s imagination.

The story behind this significant scientific revelation began in 2002, when a Colombian student visiting the coal mine made an intriguing discovery: a fossilized leaf that hinted at an ancient rainforest from the Paleocene epoch. Over the following decade, collecting expeditions led by the Smithsonian Tropical Research Institute and the Florida Museum of Natural History, University of Florida opened a unique window into perhaps the first rainforest on Earth. Fossil finds included giant turtles and crocodiles, as well as the first known bean plants and some of the earliest banana, avocado and chocolate plants. But their most spectacular discovery was the fossilized vertebrae of a previously undiscovered species of snake, one so large it defied imagination.

Together with their research teams, Jonathan Bloch of the Florida Museum of Natural History, University of Florida and Carlos Jaramillo of the Smithsonian Tropical Research Institute, joined forces with one of the world’s foremost experts in ancient snakes, Jason Head of the University of Nebraska, to unlock the mysteries of this ancient time and discover exactly how Titanoboa appeared, lived and hunted. The fossilized remains revealed that, after the extinction of the dinosaurs, the tropics were warmer than today and witnessed the birth of the South American rainforest, in which huge creatures battled it out to become the planet’s top predators. Dominating this era was Titanoboa, the undisputed largest snake in the history of the world.

Most of the fossil record of ancient snakes is comprised of vertebrae like the one that launched the Titanoboa investigation. Snake skulls are almost never found as they are extremely fragile and usually disintegrate – making it almost impossible to create a full and accurate picture of these extinct creatures. But during the filming of TITANOBOA: MONSTER SNAKE, the scientists managed to uncover not just one, but fragments of three skulls, allowing them to derive for the first time what this ancient giant looked like.

A scientifically accurate, life-sized replica of Titanoboa appears in the film and will go on display for the first time at the National Museum of Natural History beginning March 30, 2012. The exhibition will travel to museums across the country beginning in fall 2013. Titanoboa: Monster Snake is a collaboration between the Florida Museum of Natural History at the University of Florida in Gainesville, the University of Nebraska-Lincoln, and the Smithsonian Tropical Research Tropical Research Institute, and is circulated by the Smithsonian Institution Traveling Exhibition Service.

The two-hour special explores how this monster snake would have lived by visiting its living cousins, boa constrictors and anacondas, in the Florida Everglades and the Venezuelan Grasslands. The scientists’ research yields some intriguing and terrifying insights, including the climate in which it lived and size of the snake. All of these clues come together to paint a picture of Titanoboa’s world, which is brought back to life in stunning CGI. Here we see how the colossal snake ruled as an ancient apex predator among a land of tropical mega-beasts.

TITANOBOA: MONSTER SNAKE follows the scientific sleuths back to the mine, into the labs, and on an expedition to understand modern giant constrictors. It creates a picture of the then largest predator on the planet – a creature that until now has only populated fiction and nightmares, but can finally be displayed as a marvel of nature.

Evolution of earliest horses driven by climate change

John Barrat — Mon, 27 Feb 2012 18:45:22 +0000

Paleontologists studying an extreme short-term global warming event have discovered direct evidence about how mammals respond to rising temperatures. In a study that appeared recently in the journal Science researchers from eight institutions including the Smithsonian’s National Museum of Natural History found a correlation between temperature and body size in mammals by following the evolution of the earliest horses about 56 million years ago. As temperatures increased, their body size decreased. Shown here are the are the teeth of the prehistoric horse Sifrhippus at its larger size (right) with teeth from the same species after its size shrank. (Photo by Kristen Grace, University of Florida.)

Rising seas, development are altering prehistoric artifacts in the Chesapeake’s tidal zone

John Barrat — Mon, 09 Jan 2012 13:22:36 +0000

Some 1,500 to 1,000 years ago, the Chesapeake Bay region was dotted with the tiny settlements of prehistoric Indians who harvested the bay’s bounty of fish, shellfish and other animals. Today, numerous stone tools buried in sediments, shell middens and the outlines of their dwellings are all that remain of these little-known people.

As a coastal archaeologist and expert in prehistoric and historic settlement sites in the Chesapeake Bay region, Darrin Lowery of the Smithsonian’s National Museum of Natural History and University of Delaware, is carefully watching the effects of coastal erosion and rising sea levels on coastal archaeological sites. As sea levels creep slowly upward, scores of these sites are slipping under water and becoming more difficult, if not impossible, to excavate and study.

Image right: Darrin Lowery examines soils and peat marsh for evidence of ancient landscapes and sea level rise on the Mockhorn Island in Virginia. (Photo by Mike Hardesty, Washington College)

Of equal concern, says Lowery, are the chemical processes that accompany rising seas, which can modify and deteriorate the stone tools that early Americans used to hunt and prepare food and clothing hundreds of years ago. Lowery is co-author of a recent paper in the Journal of Archaeological Science on the geochemical impacts to prehistoric artifacts in coastal zones. He recently answered a few questions about his work.

Q. How do the chemical processes of sea level rise affect primitive stone tools?

A. Slowly rising sea levels result in the regular input of sediment and organic matter into low-lying areas, essentially creating areas covered in tidal marsh. Sulfidization in a tidal marsh is a process that reduces iron to its ferrous state and produces pyrite, turning stone artifacts black. A prehistoric projectile point made of jasper that has been exposed to sulfidization looks like it is made of a different type of stone called chert. This is a challenge to archaeologists because it is generally assumed that broad lithic categories can be distinguished between stone tools that are made of either chert or jasper. Over time this process can change the look of a stone artifact both inside and out.

Image left: Jasper (A) and chert (B) projectile points found at eroding shoreline sites in the Middle Atlantic. (Images courtesy Darrin Lowery)

A second process common in salt marshes is sulfuricization, which creates sulfuric acid. Highly corrosive, this acid attacks the silicate structure of a stone tool, first staining the rock with a reddish brown color and eventually causing the artifact to decompose. Having these artifacts disappear from the historic record is also of great concern to archaeologists. For a museum curator, safely storing iron-rich stone tools or artifacts that have been exposed to acid sulfate is problematic.

Q. Is sea level rise the only culprit in these changes?

A. No. The widespread practice of dredging sediment from the bottom of estuaries or along the coast and using it to build up shorelines and create living coastlines and areas for housing developments can create a situation that results in a sulfuric-acid producing machine. Marine sediments that have been oxygen-starved for several millenia are dredged up, brought to the surface and exposed to oxygen. Aerobic bacteria working on the sulfates in the sediments create sulfuric acid, as well as a series of iron oxides. If the acid is dissolving silica in iron-rich prehistoric stone tools from archaeological sites on the coast, as I have witnessed, I can only imagine how it is impacting marine life in the area adjacent to the dredge spoils.

Image right: This freshly broken projectile point made of jasper reveals the gradual precipitation of pyrite into its core, a process that has dramatically changing its color.

Q. Can you determine how much sea levels have risen since prehistoric times in North America 1,000 years ago?

A. Humans don’t like to get their feet wet so we know that prehistoric coastal sites now underwater or buried in a tidal marsh were once terrestrial, and that people were once eating, sleeping and living on these spots. Because we know that some prehistoric settlement sites in the Chesapeake Bay area are situated beneath a meter of tidal marsh peat, we can use certain “known-age” iron-rich artifacts from these submerged coastal sites to assess rates of sea level rise, as well as the rates of acid sulfate chemical change. From this we can also gauge the accuracy of the reported sea level rise rates over the past few centuries.

Surveying a large number of drowned prehistoric sites gives us the opportunity to understand those rates and the reported magnitudes.

Q. Are your projects in the Chesapeake region only focused on prehistoric settlement sites?

A. With one of my research projects, I am trying to assess the reported historic rates of sea level rise using, in part, farm fields next to tidal marshes that were first plowed long ago. We have numerous detailed historic maps showing the topographically low tidal marsh areas around the Chesapeake Bay. These maps, which encompass the last 165 years, show many tilled upland hummocks surrounded by tidal marsh. Agriculturally mixed soils are a distinctive archaeological feature formed when the thin organic soil has been turned and thickened by the plow. Back in the 17th, 18th, and 19th centuries, farmers in these low tidal marsh areas around the Chesapeake Bay didn’t have much land and they cleared every upland area right up to the edge of the marsh for cultivation. The 1840s and 1850s coastal survey maps clearly show the tilled field boundaries and historic structures on these upland hummocks.

Image left: The chemical processes that accompany rising seas is evident on the two halves of this jasper biface projectile point. The top of this artifact was found along the eroded forested upland (B). The bottom part (C) was altered by geochemical processes in the eroded upland area surrounded by tidal marsh (D) where it was found.

I’m geo-referencing these historic maps and overlaying them with recent satellite images to form a single comparative map. By doing this I can see the historic distribution of plowed fields and farms in these low coastal areas and compare them with today. Fieldwork in these areas has allowed me to relocate the historic plowed or tilled field boundaries. Many of the shorelines have been eroded by the effects of wind and waves. However, the historic plowed fields have not been inundated or covered by tidal marsh peat over the past 150 years.

What I’ve observed is that sea levels in the Chesapeake Bay may have come up a little bit in the last 150 years but I don’t believe they have risen as much as one foot, as some groups are reporting. In all my years of shoreline surveys I have never seen a 17th, 18th, or 19th century domestic site beneath a covering of tidal marsh peat. I think people are mistaking shoreline erosion and land loss, caused by wind and water chewing away at unconsolidated terrestrial sediments, with sea level rise.

For example, currently at Kent Narrows in the Chesapeake, a series of hummocks above sea level appear as upland landscapes with the same dimensions on the earlier 1840s coastal maps. Also on the Chesapeake’s Hoopers Island are a series of hummocks that were being tilled in the 1840s, the plowed landscape features are still there adjacent to the marsh and above sea level. I have observed the same conditions on Messongo Creek on Virginia’s eastern shore.

If sea levels had risen as much as one foot over the past century, the aerial extent of these isolated upland landforms should have shrunk in size and the historic plow zones associated with the hummocks should have been covered or partially covered by expanding tidal marsh.

It is important to remember that sediment erosion along shorelines does not equate to sea level rise and sediment accretion along shorelines does not equate to a sea level fall. As an example, Sharp’s Island at the mouth of the Choptank River consisted of more than 700 acres of land in 1847, but by the mid-1950’s the island had completely eroded away. Meanwhile, in 1849, Fisherman’s Island at the mouth of the Chesapeake Bay on Virginia’s eastern shore did not exist. Fisherman’s Island today consists of more than 1,800 acres of land and the island also has an extensive forested upland.

Cold spells spell trouble for warm-weather invasives

John Barrat — Fri, 06 Jan 2012 19:17:44 +0000

Aided by a recent increase in ocean surface water temperatures, new marine invaders from the Caribbean have been observed spreading northward along the southern and mid-Atlantic coasts of the United States. This northern migration of marine species—called the “Caribbean Creep”—is occurring because many of these non-native species can tolerate a broad range of temperatures.

Image left: SERC scientist João Canning Clode observes a green porcelain crab in his laboratory at the Smithsonian Environmental Research Center.

But what happens to these fair-weather travelers during a severe cold snap, such as the one that occurred in January 2010 across much of the southeastern and eastern United States? To investigate, Smithsonian Environmental Research Center scientist João Canning Clode and colleagues at the Environmental Research Center in Edgewater, Md., tested the cold-water tolerances of invasive green porcelain crabs (Petrolisthes armatus) in their laboratory. Crabs were collected in Georgia and brought to the lab where they were subjected to one of three temperature treatments. The first was a control treatment of constant moderate winter temperature. The second was treatment in which the temperature was dropped to mimic the cold snap of January 2010, and the third treatment consisted of the extreme cold temperatures of a severe winter.

Canning-Clode and his colleagues found that most of the crabs in the control treatment survived (83%), but many of the crabs in the second cold treatment (61%) and all of the crabs in the third extreme cold treatment (100%) died. Crabs that survived cold treatment number two were sluggish, possibly making them more susceptible to predation and impacting their ability to feed, the scientists determined.

The scientists determined that prolonged exposure to cold temperatures also may compromise the green porcelain crab’s ability to overcome cumulative cold events, such as the two other record cold snaps that occurred in February and March of 2010.

Image right: A green porcelain crab (Photo by Juan Antonio Baeza)

The loss of more than 60% of their population during each cold period might explain the recent dramatic decline of the green porcelain crab in Georgia in 2010, suggesting that extreme cold spells may limit or prevent the northward spread of this invasive species.

Several climate models used to predict how species will react to climate change in the next 100 years have projected a continued decline of global biodiversity and increased spread of introduced species. Many of these models focus on temperature increases, but few have evaluated the impact of severe weather like cold snaps, Canning-Clode and his colleagues write in a paper on their study recently published at PLoS ONE.

For Canning Clode “the core message of this paper is that yes, climate change is happening, but cold is also part of this change. We believe these periodic cold events will limit the range expansion of Petrolisthes armatus as well as other Caribbean creep species” –Monaca Noble, SERC

New DNA study suggests coral reef biodiversity is seriously underestimated

John Barrat — Wed, 02 Nov 2011 13:21:10 +0000

The first DNA barcoding survey of crustaceans living on samples of dead coral taken from the Indian, Pacific and Caribbean oceans suggests that the diversity of organisms living on the world’s coral reefs—one of the most endangered habitats on Earth—is seriously underestimated.

Image right: The coral reef crustacean Sadayoshia edwardsii (Photo by Gustav Paulay)

At depths of between 8 and 12 meters (26 to 39 feet), scientists collected dead coral heads from five different locations. At two sites where removing coral is prohibited, the scientists collected man-made sampling devices that had been left in the water for one year. Combined, the coral heads and devices had a surface area of just 6.3 square meters (20.6 square feet), yet 525 different species of crustaceans were found living on them.

Image left: Laetitia Plaisance searches for crustaceans on a dead coral head. (Photo by Christine Hoekenga)

“So much diversity in such a small, limited sample area shows that the diversity of crustaceans in the world’s coral reefs—and by implication the diversity of reefs overall—is seriously under-detected and underestimated,” says Nancy Knowlton, the Sant Chair for Ocean Science at the Smithsonian’s National Museum of Natural History, co-author of the survey that was just published in the journal PLoS ONE.

“We found almost as many crabs in 6.3-square meters of coral as can be found in all of the seas of Europe,” explains Knowlton. “Compared to the results of much longer and labor-intensive surveys we found a surprisingly large percentage of species with a fraction of the effort.” This shows, says Knowlton, that the statistical uncertainty of estimates of the numbers of animals living in the world’s coral reefs “is huge.”

Image right: Nancy Knowlton dismantles a dead coral head in search of crustaceans living inside.

The study is the first biodiversity survey of coral reefs from three tropical oceans to use DNA barcoding. Lead author Laetitia Plaisance of the Smithsonian’s National Museum of Natural History and the Scripps Institution of Oceanography, explains: “Given the urgency of the state of the world’s coral reefs we used DNA barcoding because it is very fast and very cheap,” she says. “We just need to take a bit of tissue from a specimen and sequence it.”

Image left: The coral-reef crustacean Thor ambionensis (Photo by Gustav Paulay)

“DNA barcoding provides a standardized, cost effective method of coming to grips with the staggering diversity of the world’s oceans,” Knowlton explains. “It has enormous potential for use in broad global surveys, allowing us to find out what is living in the ocean now, and to keep track of it in the future.”

Crustaceans collected for the survey were only those the scientists could see, and ranged in size between 5 millimeters and 5 centimeters (0.2 to 1.9 inches) long. All animals from which DNA was sequenced were preserved so they could be examined by taxonomists at a later date.

Image right: A coral-reef crustacean known as Raoulserenea ornata (Photo by Gustav Paulay)

“We collected dead corals because live corals defend themselves from being inhabited by other invertebrates,” Plaisance says. “Live corals have only symbionts—crabs and shrimp—living with them and these animals also defend their coral.”
Once a coral dies its structure becomes covered with algae, sponges, crustaceans, worms, mollusks and other creatures.

Image left: The coral-reef crustacean Pilumnus tahitensis (Photo by Gustva Paulay)

Given the complexity and extent of the world’s coral reefs, the survey covered only a very limited depth and habitat range, Plaisance explains, “and yet we have so many more species than we ever expected.”

Present estimates of reef species diversity are between 600,000 to more than 9 million species worldwide. “We cannot give a new estimate today but we may be able to in a few years,” Plaisance says.

Using man-made sampling structures at some 50 sampling sites around the world, Plaisance is now working with the Smithsonian and the National Oceanographic and Atmospheric Administration on another survey that will include all of the many organisms that live on coral reefs.

“The Diversity of Coral Reefs: What Are We Missing?” was co-authored by Laettia Plaisance, Nancy Knowlton, M. Julian Caley of the Australian Institute of Marine Science; and Russell E. Brainard of the National Oceanic and Atmospheric Administrating.

Sampling locations for this study were: Indian Ocean—Ningaloo, western Australia. Western Pacific Ocean—Lizard and Heron Islands, Great Barrier Reef, Australia. The central Pacific—French Frigate Shoals, northwestern Hawaiian Islands; Moorea, French Polynesia; and the northern Line Islands. The Caribbean—Bocas del Toro, Panama.