Imagine if the air you breathed changed your behavior. You might become reckless or disoriented, even experience loss of sight or sound. Yet, what if you had to breathe that bad air anyway, just to survive? This is a scenario that many fish and other aquatic animals could actually face in the near future, with the very seawater that they rely on to exist.
The ocean’s acidity is 30 percent higher today than it was before the Industrial Revolution began a mere 200 years ago. That transformative era of intensive agriculture, manufacturing and transportation has caused the amount of carbon dioxide emitted into the air to skyrocket. And, since our life-giving ocean is known to absorb more than a quarter of the atmosphere’s CO2, the impact of all that greenhouse gas is being felt in our planet’s underwater habitats.
Worse, when CO2 dissolves in water, it forms carbonic acid, causing the pH value of the oceans to drop. This rapid increase in the ocean’s acidity, called acidification, is not without consequence. Researchers have discovered it hinders the development of everything from corals and shellfish to sea urchins and fish eggs. Scientists are now finding it can even alter brain function in marine creatures, causing unusual shifts in behavior.
For example, consider the clownfish—Nemo’s namesake. Scientists found that as the water’s acidity rose, clownfish began to act in an odd manner. Instead of remaining close to their anemone home as they usually do, they began throwing caution to the water and swimming farther from safety. This, in turn, increases the risk of becoming someone’s meal. Even their own sense of smell couldn’t be trusted, and rather than flee from the scent of predators, clownfish in highly acidic waters were attracted to it.
Acidification has also been shown to impair the vision of spiny damselfish, inhibit the ability of snails to reattach themselves when dislodged, make rockfish more anxious, and cause hermit crabs to retract into their shells more slowly when encountering potential predators.
So, how is acidification getting into their heads? A popular theory revolves around GABA, a neurotransmitter that modulates activity in the brain and nervous system of nearly all animals, including humans.
Scientists hypothesize that the increase in CO2 prevents the GABA receptor from working properly, resulting in changes to an animal’s cognitive capacity. If this theory checks out, it could spell trouble for whole classes of organisms, since this particular receptor exists in the brains of both vertebrates and invertebrates.
Acidification has continued to escalate over the centuries, though only in the relatively recent past have we begun to understand the complex and significant changes now underway. Some projections show surface oceans waters becoming nearly 150 percent more acidic by the year 2100, a pH level that hasn’t been experienced for more than 20 million years.
Although acidification is not going away, the good news is that there is still time to address its effects. A study by scientists at Stanford University recently noted that it’s neither too late, too costly nor too complicated to counter the impact of ocean acidification—not yet. The researchers outlined numerous commonsense strategies, both local and regional, to mitigate and adapt to the changing environment.
Scientists and policy-makers are joined in this fight through NOAA’s Ocean Acidification Program, part of a broader U.S. research effort to increase our understanding of this shift in our ocean’s chemistry. Here in Maryland, a forward-looking law was just passed to empower a task force to study this critical issue and its effects on our state’s waterways, and to propose solutions. All are a good start.