Bleaching study seeks aid
Rashelle Predovnik Science Alert 18 Feb 11;
WA citizens have been enlisted to help scientists monitor the extent of coral bleaching on the 300km long Ningaloo Reef.
The Department of Environment and Conservation (DEC) has detected patches of coral bleaching due to abnormally high sea temperatures.
The DEC uses satellite technology to assess water temperatures however Ningaloo Marine Park visitors are also being asked to report sightings of bleached coral.
DEC marine science program leader Dr Chris Simpson says over the next three months observations by the public will greatly assist in determining the spatial extent and severity.
“By continually monitoring [the reef] we can look at changes over time and determine the significance of temperature induced bleaching events,” he says.
Coral bleaching is a phenomenon where algae, which gives coral its colour, is expelled from inside the reef's tissue because of stress, leaving the white skeleton of the coral behind.
Surface ocean temperatures at Ningaloo reef have been 3°C higher than average since October and peaked at 29°C recently, the ‘trigger level’ for bleaching.
The reef has experienced minor coral bleaching events caused from both elevated and lowered sea surface temperatures in the past 20 years with no apparent long-term effects.
However, the spate of recent high temperatures concerns scientists.
Dr Simpson says Ningaloo Reef has not experienced widespread bleaching to date.
“In the past, sea temperatures [at Ningaloo] above 29°C were considered uncommon and temperatures above 31°C, very rare,” he says.
“The threat of elevated sea temperatures being an early symptom of climate change, and coral bleaching a clear sign temperature stress, has prompted concerns we are seeing a disturbance on Ningaloo Reef that has not occurred before.”
“Atypical weather patterns such as the recent cyclonic activity can suppress normal weather patterns causing a higher residence times of lagoon waters and less flushing by cooler oceanic waters.”
Dr Simpson says one of the important factors for recovery is the presence of source reefs. This generates new larvae to repopulate, but requires good water quality and a strong herbivorous fish population to prevent algae colonising the reef.
“We are trying to understand the significance of this event on Ningaloo Reef and the future impact of climate change on coral reefs.”
