Coral Reefs and What Ruins Them

Cornelia Dean, New York Times 26 Feb 08;

Researchers who studied a string of Pacific Ocean atolls are painting the first detailed picture of pristine coral reefs and how they can be disrupted by people — particularly, they said, by fishing.

The researchers, from the Scripps Institution of Oceanography and elsewhere in the United States and abroad, surveyed every form of life last summer in the northern Line Islands, a chain south of Hawaii. Their survey encompassed everything from microbes to sharks and other big fish at the top of the food chain.

“Reefs without people” were healthier than populated reefs, they say in a report to be posted Wednesday in the online Public Library of Science Biology.

The ecosystems at Kingman and Palmyra, the northernmost and least populated atolls, are dominated by large predators like sharks and groupers, and corals there are robust, they said, while Tabuaeran and Kiritimati to the south, the most populated atolls, are characterized by fleshy algae, small plankton-eating fish and degraded corals.

In a commentary also published online, Nancy Knowlton and Jeremy B. C. Jackson, coral experts at Scripps and the Smithsonian Institution, said the new work was notable because it produced data at sites “across a full spectrum of human impacts.” Without this kind of data, they write, studying coral reefs is like trying to discern the ecological structure of the Amazon rain forest by looking at the cattle ranches and soybean fields that have replaced much of it.

Actually, they write, it is even worse. Scientists can still visit vast areas of intact rain forest and have decades of data from earlier researchers. “The situation is very different for the oceans,” Dr. Knowlton and Dr. Jackson wrote, because degradation of ocean ecosystems is so pervasive, and underwater observation is relatively recent. As a result, they said, scientists disagree over the relative importance for coral of local factors like overfishing and pollution as against global problems like climate change and the acidification of oceans it causes.

The Line Islands work will not settle those arguments. But the scientists noted great differences in the fish communities at inhabited and uninhabited reefs, which they attributed to fishing pressure on shark, grouper, snapper and other large predators, said Enric Sala, an ecologist formerly at Scripps and now at the National Council for Scientific Research in Spain.

Kingman is unpopulated — in fact, none of it is permanently above water. Palmyra was dredged extensively in the 1940s, the researchers said, and fishing has occurred there, but today both atolls are protected by the United States Fish and Wildlife Service as part of the Pacific/Remote Islands National Wildlife Refuge. A camp at Palmyra, with a capacity of 20, has its own sewage treatment center.

Tabuaeran, with a growing population estimated in 2005 at 2,500, and Kiritimati, with 5,100 people and growing even faster, are part of the Republic of Kiribati. People there subsist on fishing and have no sewage treatment facilities.

At Kingman and Palmyra, the ocean ecosystem is dominated by large top-predator fish, species “virtually absent” at Tabuaeran and Kiritimati, also known as Christmas Island. The researchers said this was the typical pattern elsewhere in the world, except the northwestern Hawaiian Islands.

They attributed it to fishing pressure which, they said, “tends to disproportionately reduce densities of longer-lived, larger-bodied individuals.”

The pattern in the uninhabited atolls, though, “is similar to what we see in Yellowstone — the landscape of fear,” Dr. Sala said. “In Yellowstone there are all these wolves, and the deer are much more attentive.”

As a result, he said, small fish spend much of their time hiding. “When people see photos they say, ‘Well, the water is empty,’ ” he said. “For me, it’s prettier because the corals are healthy and clean and you don’t see seaweed in the reefs and you see these big snappers and sharks.” There are far more fish on degraded reefs, he said, but they are far smaller. “The percentage of the bottom cover by large corals declines, the seaweed takes over, then the microbes become much more abundant,” he said.

The researchers said coral cover, density and species richness were highest at Kingman and lowest at Kiritimati. Coral disease was most prevalent at Kiritimati, they said.

Dr. Sala acknowledged that by the standards of the Caribbean and other heavily exploited areas, Tabuaeran and Kiritimati are in pretty good shape. But, he added, “there are 5,000 people living in Christmas and fishing there,” enough “to transform the whole ecosystem.”

At the moment, the assessment leaves the researchers with questions as well as answers. For example, reefs like Tabuaeran and Kiritimati don’t seem to survive as well in episodes of disease or bleaching. Is it because of fishing? To find out, the researchers wrote, they will have to measure how coral growth and fish productivity respond to fishing pressure and how they all interact with episodes of warm water.

But for Dr. Sala, the reefs are like “ecological machines” whose parts include plants, fish, corals and microbes. “You can hit the system with a disturbance, but the system comes back,” he said. But if pieces — like big predatory fish — are removed, he said, “the machine is going to malfunction.”

As a result, he said, the new work “is an argument for marine reserves large enough to include healthy populations of top predators.”

Studies show scope of damage to reefs
Local researchers assess range of coral ecosystems
Mike Lee, SignOnSanDiego 26 Feb 08;

The few pristine coral reefs remaining in the world are teeming with biological diversity – a stark contrast to the damaged reefs where microbes, algae and small fish have replaced sharks, snappers and other large predators.

That's the conclusion of a landmark pair of studies to be published online tomorrow by a multidisciplinary team of researchers, including some from UCSD's Scripps Institution of Oceanography and San Diego State University.

Authors of the peer-reviewed reports, which will appear in the journal Public Library of Science ONE, described them as the first studies to assess a range of coral ecosystems from the top to the bottom of the food chain.

They said the findings form a comprehensive baseline for marine biologists and conservationists trying to preserve what's left of reefs, which are huge tourist attractions and major producers of seafood for people worldwide. The insights also underscore the sheer difficulty of restoring these habitats.

“Only now are we starting to realize that throughout the tenure of coral reef ecology as a discipline, we have been seeing the wholesale loss of entire ecosystems,” said Stuart Sandin, lead author of one of the papers and a scientist at Scripps.

Robert Warner, a professor and reef-fish expert at the University of California Santa Barbara, commended the Scripps team.

“This is our first view of how the changes due to human (activities) resonate through the entire ecosystem. The Scripps team did an incredibly good job,” said Warner, who did not help write the reports but was familiar with them.

Scientists traditionally have focused on specific aspects of reef ecology, often in areas where pollution and overfishing have badly degraded the environment. That's partly because most of the world's easily accessible reefs already were damaged by the time researchers possessed the tools to carry out sophisticated marine studies.

In recent decades, people have harmed coral reefs – and oceans in general – by dumping garbage, overharvesting large fish and fouling the waters with chemical-laced sewage and urban runoff. Also, reefs have declined as ocean temperatures rise because of forces such as global warming.

To explore reefs mostly untouched by humans, Sandin and his colleagues had to travel about 1,000 miles south of Hawaii to the Line Islands. They compared the uninhabited Kingman Reef with more heavily populated areas such as Kiritimati, also known as Christmas Island.

“We use Kingman as a window into the past, a time machine that allows us to understand what we have lost and how we lost it,” said Enric Sala, an author of the studies and an adjunct Scripps professor who is based at the National Council of Scientific Research in Spain.

Sala and his team made a milestone discovery: The world's typical reefs have far fewer top-level – or predator – species than what apparently was the norm before human activities damaged them.

For example, predators accounted for 85 percent of all the fish biomass at Kingman Reef but only 19 percent at the more degraded Kiritimati.

Perhaps not surprisingly, the researchers reported that healthy reefs are better than ailing ones at recovering from periods of warm water linked to climate change. Higher temperatures bring about “coral bleaching,” a process that causes the food chain to collapse.

Sandin said the new studies show that localized reef protections, such as restrictions on fishing and other seafood harvesting, can help the ecosystems survive temperature changes.

In addition to looking at the predator populations, team members assessed the microbiology of the water at the reefs – a whole new dimension in coral studies.

New technology allowed the scientists to gain an unprecedented look at waterborne microbes, said Elizabeth Dinsdale, a biologist at SDSU.

Dinsdale and other researchers discovered that Kingman Reef had 10 times fewer microbial cells and viruslike particles than the more degraded reef at Kiritimati.

The data suggest that human activities likely are connected to the high bacterial counts at Kiritimati, though scientists are still trying to figure out how the two are linked.

“Ecosystem-based management of coral reefs has traditionally focused on animals and plants. Our findings highlight the need to explicitly include microbial processes and their influence,” Dinsdale and her co-authors said in one of the studies.

Other contributors to the new reports include those from the National Oceanic and Atmospheric Administration, Princeton University, the University of Florida and the U.S. Fish and Wildlife Service.

Although the latest research highlights the poor condition of the world's reefs, scientists said, it also offers reasons for optimism.

“Despite the wholesale loss of reefs from the planet, there are still these gems left . . . (that) really do represent the last stand of all the coral reefs from the past,” Sandin said.

The research, he said, “highlights the importance of putting conservation dollars toward saving these areas.”