Rising CO2 Levels Lead To Bigger Fish Ears

For years scientists have observed the deleterious effects of rising levels of carbon dioxide in the oceans on shellfish and corals. Now, a new study by the Scripps Institution of Oceanography has provided evidence that the physiological development of fish ears is also impacted by the gas.

In the June 26 edition of the journal Science, researchers from the San Diego-based institute published a short paper outlining the results of experiments in which young white seabass were continuously exposed to high levels of CO2. The most dramatic change observed was the aberrant enlargement of the fish’s ear bone, or otolith, which plays a critical role in helping the animals to sense their surroundings and swim upright.

The results were particularly surprising to the researchers, whose initial hypothesis had predicted the shrinking of the otolith in response to elevated carbon dioxide levels. In general, there was no increase in the overall size of the fish, only in the relative size of their otolith.

“At this point one doesn't know what the effects are in terms of anything damaging to the behavior or the survival of the fish with larger otoliths,” explained lead author of the study, David Checkley.

“The assumption is that anything that departs significantly from normality is an abnormality and abnormalities at least have the potential for having deleterious effects.”

As carbon dioxide levels around the planet are on the rise, ostensibly due to human activities, one of the many effects has been an increased acidification of the world’s oceans.

Environmentalists and oceanographers alike have watched with horror as falling pH levels in the oceans have brought on the massive erosion of coral reefs and a dramatic shrinking of plankton populations.

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