Ex-cyclone Olga kills Cairns crabs
HUNDREDS of ghost crabs, a species of sand crab, have been found dead along the mudflats lining the Esplanade Lagoon in the wake of ex-cyclone Olga.
The dead crustaceans have created a fishy smell and an environmental eyesore for tourists and locals in recent days.
Pictures: Cyclone Olga
James Cook University crab researcher Chaoshu Zeng said recent torrential rain was the most likely reason for the mass deaths.
Dr Zeng said too much fresh water lowered the iron levels of the crabs and led to over-hydration – the opposite
of dehydration.
"Some species where the water gets too fresh migrate to deeper water where the salinity levels are higher but ghost crabs don’t have the capacity for long distance travel," he said.
"Their immune systems weaken straight away and they’re liable to all sorts of diseases."
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Most species of aquatic organisms have their own unique range of tolerance for high and low salinity environments, which is called osmoregulation.
Dr Zeng said most sand crabs, including ghost crabs, had a weakened ability to survive in areas with high levels of fresh water.
He also said mud crabs were better equipped to survive in broader salinity conditions.
The crabs’ plight is expected to continue with predictions ex-cyclone Olga will develop in strength and drift further south east across the Gulf this week, causing more rain.
More than 80mm of rain fell over Cairns on Wednesday and weather experts have predicted a similar deluge for tomorrow.
The weather bureau’s Janine Yuasa said an increase in showers and storms was imminent.
"There’s a pretty good chance rain will be continuous on Saturday, I’d say there’s a good chance we’ll get a lot," she said.
http://www.cairns.com.au/article/2010/01/29/90385_cyclone.html
