- Coral Bleaching
by Brad Cox
This year coral bleaching has once again
returned to the Great Barrier Reef and scientists are concerned that this is the warning
that signals the demise of our glorious natural wonder. Coral bleaching is already
responsible for killing more than 16% of the worlds coral reefs. Marine biologists
believe if these bleaching events continue, then within three decades the undersea gardens
of the Great Barrier Reef and the rest of the world will be destroyed.
To begin the fight to save the coral
world-wide scientists need to get a clear understanding of the exact reasons why bleaching
occurs. The Great Barrier Reef is more than 2000kms in length and there are tens of
thousand of square kilometres of reef on the planet. To gather knowledge essential in this
struggle over such a vast area, the scientist are now looking for assistance from the
people who will be the most affected by the loss of these beautiful marine structures -
Associate Prof Justin Marshall from the
University of Queenslands Heron Island Research Station is convinced that,
Coral Bleaching is linked to global warming. As sea temperatures rise around
the world these severe coral bleaching events occur in many reef systems. On Heron Island
scientists have recorded an increased frequency in bleaching events, with major
occurrences in 1998, 2002 and minor events as recently as July this year. At the same time
they have been monitoring the effect of global warming on the ocean temperatures and
believe the two are inextricably linked.
Heron Island lies on the Tropic
of Capricorn and is one of the first tropical coral cays at the southern end of the
majestic Great Barrier Reef chain. Located 72 kms North East of Gladstone on
Queenslands central coast, it has a historic and unique reputation for both its
leisure activities and scientific research. Associate Professor Justin Marshall with his
research team of two, including research assistant Kylie Jennings and Dr. Uli Siebeck, and
in close association with world coral expert and Director of Heron Island Research
Station, Prof Ove Hoegh-Guldberg, has recently made a major break though in being able to
measure the colour of coral and its direct relation to coral health.
Prof Marshall and his team have discovered
that while coral health can be calculated by measuring the number of living organisms
within, it can be more simply measured by checking the corals colour. Coral in our
imagination is all the hues of the rainbow. In fact when you strap on the flippers and
get wet with the researchers, you realise that our memory holds onto only the
most striking colours and shapes of the reef. The vast amount of corals are in fact more
conservative. The large outcrops of plate coral and the magnificent bommies rising metres
off the sea floor, along with rest of the marine super-structure are deep greens, rich
browns or dark yellows. These are the base tones that underscore a grand symphony layered
with the more spectacular coral colors and iridescent marine life.
The hard skeleton of coral is built by a
community of animals related to jellyfish, coral polyps. The secret to their huge success
in the worlds warm oceans, comes from their special lodgers, small plants or algae,
that each polyp houses within its own body tissue. While these plants provide food for the
coral, almost like a self-contained farm or garden, the coral polyp protects the garden
from hungry mouths outside. Coral colours that we see come largely from the number of
algae contained within the body of the polyp.
In 1998, 2002 and again this year various
parts of Heron Islands reefs went white. This loss of colour results from a
breakdown in the relationship between coral and plant and, for reasons only just becoming
understood, the algal lodgers were evicted. While this probably happens as a natural
course of events every now and then (tenants do become troublesome, move on or die) what
the scientists are now noticing are more frequent and more wide spread bleaching events.
Each of these happens when sea temperature stays unusually hot for too long and this is
the result of global warming.
What happens after a bleach? The tenants are
not rejected forever, gardens are re-grown and new algae taken in, but loss of nutrition
for the coral polyps takes its toll. 1998 saw 16% of the worlds reefs dead after a
bleach. Some coral recovered, much however was in such an exhausted state that their
annual breeding cycle was disrupted. The effect of the 2002 bleach is still being assessed
and understanding the effect of such a widespread phenomenon is difficult. Monitoring
bleach and recovery of coral on even a small reef is a huge time-consuming task. What is
needed is a quick, but also scientifically sound method of assessment.
The research team had already proved that they
could determine the number of algal lodgers in coral, based on the varying shades of
colour. For example, rich colours indicate millions of tiny of algae present, as the
corals colours slide toward the lighter shades there are fewer nutrition providers,
ending in white which may lead to starvation. A scale of these shades was assembled from
the darkest through to white. Each shade represented the number of organisms alive in the
coral and was given an individual code. When these shades were reproduced on a printed
chart, they immediately resembled something very familiar. Home renovators would recognise
it as a paint colour chart from the local hardware store. The scientists knew the
familiarity and simplicity of the chart could be the key to the massive data collection
task ahead of them. The charts were printed on waterproof plastic, with each edge
containing the range of shades for the main coral colours.
Taking these charts out on the reef, the
scientists only had to match the shadings from the chart with the coral being inspected,
and immediately they had a measure of algal numbers and coral health. A team of just four
scientists however, can cover only a small patch of the reef and to make this coral health
system work, hundreds of readings from a variety of sites must be gathered over time.
These findings, added to a database then give an overall measure of the stresses that
coral at Heron (or elsewhere) are under. Similarly the data matched to sea temperature
fluctuations, and other stresses, scientifically validates the cause of bleaching on reef
The question was; How to gather thousands more
people to go out to the reefs every day to snorkel, dive and walk around making colour
matches and recording codes? At the research station on Heron Island, swarms of tourists
take guided tours to see what work is being carried out to preserve their beloved coral
cay and everyday the visitors ask the same question of the researchers, What can I
do to help protect the reef?.
The answer to that question is now a Coral
Health Chart (pictured above). Tourists set off on their scheduled reef walks or diving
trips more than sight-seers, but as a willing army of data recorders. Some of the tourists make only a few recordings,
others fill the data sheet and ask for another. All the codes they record are either
entered into the database on the web site www.coralwatch.org by the tourists or delivered to the research team
who plug them into the computer database themselves, constantly enriching the quality of
information they now have on coral health.
In May this year a test program
was set up by the University of Queensland research team led by Prof Marshall and P&O
Resorts. Visitors to Heron Island are now offered the charts to take with them on their
daily activities as well as a specialised Coral Health Reef Walk. Michael Sheridon, Heron
Island General Manager says, This is a good new idea for the resorts guests. They
are always looking for something new since their last visit. We have always had an
excellent working relationship with the University of Queensland research station and I
think we need to see how these charts and the guided walks are taken up be the
All the activities officers on Heron are
qualified marine biologists. Theyre enthusiasm in guiding the Coral Health Reef
Walks is paramount to the success of this trial. Belinda Mann, one of P&O
Resorts activities officers decided to take up leading the Coral Health Reef Walk
because the first question from more than 90% of her guests is about coral bleaching.
Belinda now takes more than 20 tourists a week on Coral Health Reef Walks. Many of
our guests want to do something more than just look at the coral and other animals. This
coral health walk gives them the chance to not only participate in real research, but many
guests feel they have contributed to saving the environment. Rather than just hearing
about the problems of bleaching and the other threats this is something active,
Talking with some of the guests as they
prepared to set out with their charts in hand, Julia and Andrew Millen from Sydney say
they are glad to taking part. Being involved in the coral monitoring at Heron
Island gives us a great sense of doing something for the coral reefs and we're happy
to do this as a holiday activity says Julia. Prof Marshall knows that measuring
the health of the coral is not going to immediately stop coral bleaching. The facts
indicate that to have a real chance of saving the worlds reefs, countries around the
world must decide to do something about humankinds acceleration of global warming.
Prof Marshall carefully explains,
Its only when we change our consumption patterns that we can really contribute
to saving the worlds reefs from bleaching. And I think that these Coral Health
Charts can assist in raising awareness and working toward those outcomes. The
program of using charts we hope will become just another one of the enjoyable past-times
that people do when they visit a reef system. The data that is collected will certainly
help us monitor the health of coral and may even provide an early warning system if a
bleaching event was on the way.
But just as importantly it may assist in
letting people know that individual contributions to saving the environment can make a
global difference. Having seen the mind-boggling beauty of the reef and be faced with the
loss of such splendour, tourists helping out and then going home to think over their
holiday may even begin to change the way they do many other things in their lives.
The research team are now looking at expanding their coral health program to many other
islands throughout the Great Barrier Reef and have recently been funded by
Australias Cooperative Research Centre for Sustainable Tourism to take their
valuable and coral health to international destinations.
To contact the research team about the coral
health monitoring project visit www.coralwatch.org
or email Kylie Jennings on K.Jennings@uq.edu.au,
phone +61 (07) 3365 4063.
Author: Brad Cox, Communications
Manager, Co-operative Research Council for Sustainable Tourism, Queensland, Australia