Scientists Believe Coral Death A Form Of Suicide, ABC, 03/20/07
By Barbara Miller
Source: ABC News
ELEANOR HALL: Marine scientists in Queensland have come up with an intriguing explanation for the rapidly emerging coral reef killer known as "white syndrome".
The researchers say the syndrome is not caused by bacterial attack from the outside, but by a self-destruct mechanism inside the coral. And they say what they regard as a form of coral suicide is a reaction to stress.
Barbara Miller reports.
BARBARA MILLER: Rising sea temperatures, water pollution and over-fishing can all make life just a long hard slog for a coral reef.
And if as a result they suffer bleaching, the researchers say, it can become downright unbearable.
Professor Ove Hoegh-Guldberg is Director of the Centre for Marine Studies at the University of Queensland.
OVE HOEGH-GULDBERG: The effect of coral bleaching is that you lose the energy reserves of the coral. And as a result, as they go into the winter months when food becomes short and there's not as much sunshine, and if they've been stressed out by bleaching, essentially they run out of energy.
And we suspect what's happening here is that this is a cell process that corals have when they're short of supplies. So, they essentially withdraw themselves back to a smaller colony size in the hope that they can then survive to the next summer and then start to regrow.
BARBARA MILLER: So, if we try and put in sort of human terms, could we say that basically the corals realise in some way that they're under threat and that some of them self-sacrifice to ensure that the population does continue?
OVE HOEGH-GULDBERG: I think that is the way we're seeing it. It is literally cells that are committing hari-kari for the sake of the rest of the colony. And so, it's really interesting.
It hadn't been reported in corals before, but the more we look now and the more we find it.
BARBARA MILLER: Programmed cell death occurs to some extent in all organisms. But the researchers say it's happening to a far greater extent than normal in corals.
OVE HOEGH-GULDBERG: I think under normal circumstances corals are ... they're having a little bit of sort of self-regulation of the colony in cell numbers and polyps and so on.
I think when they're under stress though, they turn it on big time and in fact what we've discovered is this type of disease, it's seen across corals across the world, something called "white band" is in fact probably due entirely to this type of process as opposed to what people were thinking in the past was that these white zones on coral were in fact war zones, that it was where the coral was battling bacteria and so on.
BARBARA MILLER: Professor Hoegh-Guldberg says the findings of his PhD student Tracy Ainsworth have turned around thinking on cell disease.
OVE HOEGH-GULDBERG: Science often does that to you. You can absolutely believe in an idea and then suddenly it gets turned on its head. And it just takes that little insight like the one that Tracy has discovered to now suggest a whole series of other avenues of investigations.
BARBARA MILLER: But he cautions the results don't mean we should think corals can adapt to the pressures they're under.
OVE HOEGH-GULDBERG: With rising sea temperatures and so on we're going to see more and more of this. And I feel that we're going to see that a lot of these processes will eventually be exhausted.
And that's in fact what happened in the Caribbean when they lost their staghorn corals, especially off a country called Belize where they have the second largest barrier reef system in the world, and they had, you know, die off of corals due to coral disease.
So, no it doesn't really give us that sort of strong glimmer of hope that somehow they can handle this sort of stress.
ELEANOR HALL: Scientist Ove Hoegh-Guldberg from the University of Queensland, speaking to Barbara Miller.