CO2 in water affects fish

Study shows that increasing emissions of carbon dioxide can affect the brain and central nervous system of marine fish with serious consequences for their survival.

The reason is that it will interfere in the ability of these animals to hear, smell, turn around and escape predators. That's what a study published by the journal of "Nature Climate Change."

ARC Centre of Excellence for Coral Reef Studies, said that tests the performance of babies of coral fish in the sea water with high levels of dissolved carbon dioxide for several years. "And now it's clear that they suffer a significant change in their central nervous system and can hurt their chances to survival," said Philip Munday, a teacher who reported the findings.

In scientific research, Munday and his colleagues also detailed what they say is the first evidence in the world that CO2 levels in seawater affect a key brain receptor in fish, causing marked changes in their behavior and sensory abilities.

"We found that high concentrations of carbon dioxide in the oceans can directly interfere in the functions of neurotransmitters of the fish, which represents a previously unknown and direct threat to marine life," said Munday.

The team began studying the behavior of young clown fish and damsel fish alongside their predators in an environment of water enriched with CO2. They found that while predators were little affected, the offspring showed a much greater wear.

"Our initial work showed that the sense of smell in young fish was affected by the presence of more CO2 in the water, which means they had more difficult to locate a shelter or coral to detect the odor of a predator fish alert" said Munday.

The team then examined whether the hearing of fish (used to locate and occupy reefs at night and avoid them during the day) had also been affected. "The answer is yes, it was. They were confused and left to avoid sounds coral during the day. Being attracted by the coral in the light of day would make them easy prey for predators," the researchers added.

The study also showed that fish also tend to lose their natural instinct to turn right or left, an important factor of learned behavior. "All this led us to suspect that what was happening was not simply an individual harm to their senses, but rather that higher levels of carbon dioxide were affecting the central nervous system as a whole," he added.

Munday said that 2.3 billion tons of CO2 dissolves in the oceans of the world every year, causing changes in water chemistry in which live of fish  and other species.