martes, 15 de noviembre de 2011

Un difícil Edén - An Uneasy Eden by Brian Skerry

Brian Skerry is a photojournalist specializing in marine wildlife and underwater environments. Since 1998 he has been a contract photographer for National Geographic magazine, covering a wide range of subjects and stories.
An award-winning photographer, Skerry is praised worldwide for his aesthetic sense as well as his journalistic drive for relevance. His uniquely creative images tell stories that not only celebrate the mystery and beauty of the sea, but also help bring attention to the large number of issues that endanger our oceans and its inhabitants.

Spectacle of color and shape, hard coral carpets a shallow seafloor on Kingman Reef. Scientists visiting the remote Pacific Ocean atoll reef describe it as a "time machine," an ecosystem that has survived in an almost pure state of nature.

Sharks—whitetip and gray reef—and red snappers prowl Kingman's waters for food. Cloud-like schools of fish, a common sight at most reefs, hardly exist here. The healthy abundance of large predators, accounting for 85 percent of the fish biomass, forces most prey fish into hiding.

Ambush specialist, a blackside hawkfish lurks amid coral to surprise smaller fish and crustaceans. A mid-level player in the food web, the hawkfish must strike swiftly and retreat to its hiding place, or else a red snapper, larger and equally vigilant, may grab it.

Parading colors of sun and sky, a lemonpeel angelfish shows itself in the lagoon at Kingman Reef. Photographer Brian Skerry said that at no other reef has he worked so hard to get pictures of small fish: "I didn't see the huge schools I was used to on less healthy reefs." At his approach, fish would usually retreat into the coral. "They must have thought I was a shark," Skerry said.

On a gorgeous reef perfect for idle sightseeing, researchers dutifully focus on work. Ecologist Jennifer Smith (foreground), of the University of California at Santa Barbara, deploys a photoquadrat frame above lobe coral to document meter-square segments along a transect line. Back on ship, Smith will analyze the images to create a profile of the various species inhabiting the reef bottom. In the background, Jim Maragos, a coral specialist with the U.S. Fish and Wildlife Service, counts, sizes, and identifies coral along the same transect. "I've been privileged to visit thousands of reefs in more than 30 countries," said Maragos, "and Kingman is truly the most pristine reef I have ever visited."

The divers who found it said that from a distance it looked like a flying saucer. On closer examination, ecologist Enric Sala sees a stupendous lobe coral that may be 500 years old. According to reef expert Jim Maragos, the species is likely new to science.

Gray reef sharks and red snappers hover above a patch of table coral, waiting for prey fish to emerge. "They go after everything that moves," observed Enric Sala, a marine ecologist on Spain's National Council for Scientific Research and a National Geographic fellow. Because of their abundance and the resulting competition for food, the sharks and snappers at Kingman Reef, Sala said, "are always on the verge of hunger."

Wary of being eaten, a fang blenny, just a few inches long, feels safe in its coral hideout. Fang blennies do take risks, venturing out to feed on scales, fins, and even mucus coating the skin of larger fish.

A combtooth blenny, only a few inches long, hides from predators.

Needle-sharp teeth matched with voracious hunger make the red snapper the reef's most aggressive predator. Reaching lengths of 30 inches, snappers sometimes attacked the divers, biting at ears and hair. "They wanted to taste us," says Sala.

A blue damselfish doesn't swim far from a sheltering coral colony. Compared with reefs that have lower numbers of predators, the prey at Kingman Reef, marine ecologist Enric Sala said, "spend less time in the open, less time eating, more time watching. They are afraid."

A thicket of tentacles belonging to Heteractis magnifica, the magnificent sea anemone, provides cover for a transparent shrimp the size of a rice grain. The sea anemone, anchored to the reef, ignores shrimp but nabs small fish and other passersby.

This is how a healthy reef looks: corals lush and various covering the seabed; water as clear as air; and a large native predator—a red snapper—hunting for elusive prey. Kingman Reef's secret? Not a human predator in sight.

Clearing everything in their path, crown-of-thorns sea stars hungrily advance across a lobe coral, stripping it to a bony white skeleton. Periodic sea star infestations occur naturally on reefs, joining with other biological processes and wave action to determine the layout of coral. Recent surveys of Kingman confirm that healthy reefs withstand sea star predation much better than sites exposed to fishing and pollution because such predators as triton's trumpet snails, still common on healthy reefs—and prevalent at Kingman—kill the sea stars.

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