RISING carbon dioxide (CO2) emissions  threaten the survival of some 
fish species by sending their central nervous systems haywire.
            
Researchers from the Australian Research Council Center 
of Excellence for Coral Reef Studies and James Cook University say 
concentrations of CO2 are predicted to reach between 700 and 900 
microatmospheres before the end of the century, interfering with the  
ability of the fish to hear, smell, turn and evade predators.
            
''It is now pretty clear that they sustain significant 
disruption to their central nervous system, which is likely to impair 
their chances of survival,'' Professor Philip Munday said yesterday.
                
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''We've found that elevated carbon dioxide in the oceans 
can directly interfere with fish neurotransmitter functions, which poses
 a direct and previously unknown threat to sea life.''
            
The team examined how baby clown and damsel fish and 
their predators dealt with water enriched by carbon dioxide. While the 
predators were slightly affected, the baby fish suffered to a much 
greater degree.
            
''They found it harder to locate a reef to settle on or 
detect the warning smell of a predator fish,'' Professor Monday said.  
The team looked more closely and found the hearing of the fish was 
affected as well as its smell. Then they started to lose their natural 
instinct to turn left and right.
            
''All this led us to suspect it wasn't simply damage to 
their individual senses that was going on but rather that higher levels 
of CO2 were affecting their whole central nervous system.''
            
The team concluded that high levels of  carbon dioxide 
stimulates a receptor in the fishes' brains called GABA-A.   The 
receptor's function is reversed and some nerve signals become 
overexcited.

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