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article imageOp-Ed: Ocean acidity causes fish to go looking for their predators

By Paul Wallis     Apr 14, 2014 in Science
Sydney - Studies of the effects of carbonic acid, the CO2 related acid formed by carbon emissions and underwater volcanoes have shown that fish affected by the acid actually go looking for their predators.
In an interview with ABC Australia’s PM, scientist Philip Munday of James Cook University explained:
PHILIP MUNDAY: So what we've found is that in these areas where the carbon dioxide levels are similar to what we would expect later this century, that the behaviour of the fish is impaired.
They become attracted to the smell of predators, for example - a really maladaptive response; normally they would be repelled from the smell of predators, but here they are actually attracted. They are more active, and they actually venture further away from shelter, all of which would make them more likely to be exposed to predators.
…So, what we find is that these carbon dioxide levels - high carbon dioxide levels - actually interfere with a fundamental neurotransmitter in the brain of the fish, and it causes them to do all sorts of odd things, such as being attracted to smells that they would normally avoid, or taking riskier behaviour that might then end up meaning that they'd get eaten by a predator.
Interestingly, the fish are not physically impaired. They’re perfectly healthy, “irrational” fish. The ecological ramifications of the kamikaze fish aren’t clear, but any biological process which crashes survival instincts can’t be a minor event. It should also be noted that the “attraction” response is effectively the exact opposite of what would normally be the intended response, suggesting a polarized reaction in the neurotransmitters.
CO2 vs. neurotransmitters? What about humans?
More interesting is the idea that high CO2 levels interfere with neurotransmitters at all. A neurotransmitter is a chemical which is released at the end of a nerve fibre, transmitting a signal to another nerve.
It’s not hard to understand that if the neurotransmitter chemical is sabotaged by contaminants, the behavior of the animal is naturally affected. The signal is changed by the chemical composition of the contaminated signal.
Check out a list of neurotransmitters on, and you’ll see there are some critically important chemicals involved in neurotransmission:
Acetylcholine – involved in voluntary movement, learning, memory, and sleep
§ Too much acetylcholine is associated with depression, and too little in the hippocampus has been associated with dementia.
Dopamine – correlated with movement, attention, and learning
§ Too much dopamine has been associated with schizophrenia, and too little is associated with some forms of depression as well as the muscular rigidity and tremors found in Parkinson’s disease.
Norepinephrine – associated with eating, alertness
§ Too little norepinephrine has been associated with depression, while an excess has been associated with schizophrenia.
Epinephrine – involved in energy, and glucose metabolism
§ Too little epinephrine has been associated with depression.
Serotonin – plays a role in mood, sleep, appetite, and impulsive and aggressive behavior
§ Too little serotonin is associated with depression and some anxiety disorders, especially obsessive-compulsive disorder. Some antidepressant medications increase the availability of serotonin at the receptor sites.
GABA (Gamma-Amino Butyric Acid) – inhibits excitation and anxiety
§ Too little GABA is associated with anxiety and anxiety disorders. Some antianxiety medication increases GABA at the receptor sites.
Now- Take the logic of a situation where fish with impaired neurotransmitters caused by a common carbon compound one step further:
If fish are affected by chemically induced neurotransmitter contamination, what about people?
Do chemically sabotaged neurotransmitters switch on a type of stupidity, or “maladaptive” process? If they can’t do what they’re supposed to do, their actions must be anything but the intended neural process, systemically transmitted through the entire nervous system, because the neurotransmitters originate in the brain. They’re the system, in effect.
Lead, for example, has long been known to be a hazard to the human nervous system, as well as anything organic with which it comes into contact. Lead pipes have been considered unhealthy, and the cause of “dumb kids” for many years.
So why wouldn’t other neurotransmitter sabotaging chemicals have similar effects? Have fish proven the existence of a previously unknown neurological risk?
To make a point- Human brains and nervous systems aren’t the same thing as the fish equivalents. However, if you look at that list of neurotransmitters, most people will see a list of chemicals which are directly related to a lot of well-known mental disorders.
Is it possible that there are major environmental factors which are affecting human neurotransmitters this way? Depression and other disorders are related to imbalances of many neurotransmitters, with well-known effects which are still being researched long after their discovery. Incidence of these disorders is extremely high, by any standards, effectively universal, which points to the environment as a factor in any type of epidemiology.
Sources of free carbon and carbon compounds in the human environment aren’t exactly hard to find. These disorders are universal, regardless of place of residence, social status, or other health issues. That’s a very odd epidemiological pathology for a range of very common conditions.
The results of Munday’s research will be published in Nature Climate Change. It’ll be interesting to see if the research is expanded to study CO2 effects on other species, in other environments.
This opinion article was written by an independent writer. The opinions and views expressed herein are those of the author and are not necessarily intended to reflect those of
More about Philip Munday, James Cook University, CO2 effects on neurotransmitters, Dopamine, Serotonin
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