Australia’s Great Barrier Reef

From tiny coral polyps grew a marvel: Australia’s Great Barrier Reef.

“Reefs for me are places for solitude and thought,” says Australian marine scientist Charlie Veron, here admiring a garden of stony corals on the northern Great Barrier Reef. “But I know there is fragility in their existence. I fear what lies ahead.”

 

The peculiar humphead wrasse is among the reef’s many thousands of species.

 

Wide ribbons of coral, visible off Australia’s east coast, divide the continental shelf from deep, darker waters farther out to sea.

 

Rhythmic currents in Challenger Bay push and pull a school of diagonal-banded sweetlips. Members of the grunt family, these fleshy-lipped fish feed at night, plucking invertebrates from the sandy sea bottom.

 

A whitetip reef shark cruises over Great Detached Reef.

 

The clownish grin of a bridled parrotfish reveals its power tools: grinding teeth used to scrape algae from rock. Though sometimes destructive to individual corals, the fish’s efforts are mostly beneficial. Without them, algal growth could smother the reef.

 

Cardinalfish zip by a hawksbill turtle as it rests among feathery invertebrates called hydroids. Illegally harvested for their shells, hawksbills are declining globally. Some 3,000 nest along the northern Barrier Reef.

 

Following a full-moon night or two each year, immobile stony corals like Acropora millepora release egg and sperm bundles simultaneously in an orgy of mass spawning. Fertilized eggs, once they have settled near and far, are the stuff of new colonies.

 

Blue-green chromis take refuge in a hard-coral thicket on Great Detached Reef. Fusiliers pass overhead.

 

An anemonefish peers out from among the toxic tentacles of its sea anemone home.

 

Drawn to the smell of a dead sperm whale, a ten-foot tiger shark arrives at the edge of the reef to feast on floating flesh. Bits of food left undevoured will fall to feed the reef’s tinier residents.

 

A two-foot-long sea cucumber shoots thousands of ova into the current. These sea star kin—whose bumpy papillae are sensory—spawn en masse, boosting the chance of reproductive success.
Holothuria fuscopunctata

 

Slender cardinalfish gleam against a gorgonian, or sea fan, on a northerly reef. The soft coral’s vivid color likely suggests toxicity to those passersby tempted to nibble at its branches.
Rhabdamia gracilis (Fish); subergorgia sp. (Coral)

 

A bumphead parrotfish and a grouper, also known as a potato cod (at top), hover near the sandy sea bottom.

 

Tightly packed hard corals, mostly Acropora species, vie for space and energy-giving sunlight off Cairns. Though highly vulnerable to changing sea chemistry, these master builders of Indo-Pacific reefs have persisted for millions of years.

Moray eels battle for a hiding spot in Challenger Bay, Australia.

 

A swollen Australian river carries thick plumes of sediment (brown, at center) into the sea off Queensland in this NASA satellite image. Major flooding in December 2010 and January 2011 sent an influx of poor-quality water near the Great Barrier Reef. The full impact isn’t yet known, but heavy doses of nutrients from fertilizers can lead to harmful algal blooms, while sediment can block light, halting photosynthesis and smothering the coral.