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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