Riddles about the "halos" of the coral reef: Strange rings of bright material that can be seen from space could be a sign of the health of the reef, experts say
- . "Halos" are rings of bare sand that extend outward to algae that surround reefs
- Scientists confirmed that they were first produced by grazing fish
- Other puzzles were identified in their study by discrepancies in logic
- popped up
After a decade-long survey, the researchers have some secrets behind the "halos" of sand surrounding the coral reefs, and what they could mean for the battles , revealed health of habitats.
The so-called "halos", which can be observed from satellite imagery, are rings of bare sand located between algae and algae surrounding the coral reefs.
Since the 1960s, theories have claimed that the halos are created by hungry creatures that live in the reefs.
In order to avoid exposure of predators in open water, it was believed that sea urchins and fish on the green would selectively chew with the algae as a shield and hollow out paths while remaining enveloped by the remaining patches.
After decades of research, researchers have discovered some secrets behind the "halos" of sand that surround the coral reefs. and what they could mean for the health of the contested habitats
Although this theory was proposed 60 years ago, researchers have not been able to document the phenomenon so far.
Elizabeth Madin, scientific assistant at the Hawaiian Institute of Marine Biology, and her team set up a series of cameras surrounding a reef of Heron Island in Australia.
What they observed was exactly what had been predicted – the theory called the "Grazer Hypothesis" was correct.
Researchers saw for the first time specific features of the theory. Some species of fish on the algae and algae from the inside, and others – much larger and less afraid of predators – ate outwardly.
Even with these enlightened secrets, others have appeared.
Halos should be more abundant when fishing is limited, if the halos are exclusively caused by grazing fish.
They should also be smaller, as fishing preserves large predators, so more creatures would be forced to hide in their algae to eat the algae.
Neither of the two results proved true, a tandem of researchers planning to continue studying the reefs to find the puzzles.
For Madin, the discoveries, though exciting, may be only the beginning.
"This will pave the way for the development of a novel, technology-based solution for monitoring large coral reef areas, and for managing sound reef ecosystems and sustainable fisheries," she said in a statement.
WHAT IS CORAL BLEACHING?
Corals have a symbiosis with a tiny marine alga called "Zooxanthellae" that lives and nourishes inside.
When the water temperature rises on the surface, corals eject the colorful algae. By losing the algae they are bleached and white.
These bleached conditions can last up to six weeks, and as the corals recover, when the temperature drops and the algae return, heavily bleached corals die off and are covered by algae.
In both cases it is difficult to differentiate between healthy corals and dead corals from satellite imagery.
This bleach has recently killed up to 80 percent of coral in some areas of the Great Barrier Reef.
Bleaching Events of this kind take place four times more frequently worldwide than before.
. Aerial view of the Australian Great Barrier Reef. The corals of the Great Barrier Reef have undergone two consecutive bleach events in 2016 and early this year, raising experts' concern about reef survival under global warming.