Deaf Fish? An Ocean Acidification Update

Of all the threats to the planet’s ocean (climate change, plastic pollution, overfishing) none may be more insidious or have longer-term impact than acidification. It is also the least understood of all the potential harms.

Photo: BrianMay/Creative Commons

Admittedly, it is far easier to visualize plastic afloat on the surface of the Pacific or vast tracts of the Atlantic nearly devoid of fish than a chemical imbalance. But it is the change of acidity which may already be the ocean’s worst enemy.

Try this for a visualization, maybe it will help: Twenty four million tons of carbon dioxide created by the burning of fossil fuels—or the equivalent of 24 million Volkswagens—are dumped into the world’s ocean every single day.

During the 20 million years before man began burning coal and oil, the acidity of the ocean was relatively stable. Over the last 250 years, the ocean has absorbed 530 billion tons of CO2, triggering a 30 percent increase in ocean acidity. Researchers predict that if carbon emissions continue at their current rate, ocean acidity will more than double by 2100.

On top of destroying coral reefs (the equivalent of wiping out rainforests on land) and killing off shellfish beds, including mussels and oysters, a new report out of the U.K. suggests that the so-called “evil twin” of global warming is responsible for some fish losing their sense of smell.

Specifically, baby clownfish, which use hearing to both detect and avoid predator-rich coral reefs during the day are proving to be impaired by the change in ocean acidity.

A pair of scientists, Dr. Steve Simpson of the University of Bristol and Professor Philip Munday of James Cook University, studied juvenile clownfish that had been exposed to salt water with CO2 added, bringing it to levels equivalent to predictions by the Intergovernmental Panel on Climate Change. After 17 to 20 days of exposure, they monitored the juveniles as they swam near to coral, crustaceans, and other fish; those reared in today’s conditions swam away from the noise, but fish reared in future conditions showed no response.

On a slightly hopeful note, researchers suggest that the fish that survive the increase in acidity may adapt to new levels. That’s if they survive, of course.

The cynical out there might suggest that a few deaf clownfish may not be the worst tradeoff for cheap energy, nor something demanding immediate attention.

But another change thanks to more acid in the ocean—a boom in jellyfish populations around the globe—should be more alarming. The rapid growth of jellyfish herds, which thrive in warmer waters, is being attributed to a combination of warming sea temperatures and ocean acidification, both driven by climate change.

As well as making summer beach-going tricky when masses of jellyfish wash up on shores from the Mediterranean to Florida, the jellyfish have also caused the recent shutdowns of three nuclear power plants, in Israel, Scotland, and Japan. The plants suck water out of the ocean for cooling, and though fitted with filtration devices, the “jellies” are overwhelming the systems, causing the plants to shutdown. Desalination plants around the world are suffering similarly.

What makes acidification trickier to deal with than other ocean threats is simply its invisibility, prompting researchers at the University of Alaska Fairbanks to construct the first “ocean acidification buoys”; these are anticipated to be the best tools yet to measure just how pH levels are changing.

The seas most impacted by acidification are in the Polar Regions, especially the north, due to unique circulation patterns and cold-water temps. This spring, scientists launched the first such measuring buoy in Resurrection Bay near Seward, Alaska; a second will be deployed in the Bering Sea this month, and a third in the Chukshi Sea in October.

Floating on the ocean surface and anchored to the seafloor, real-time monitoring via satellite will feed info back to Fairbanks. One big question the scientists have is whether the acidity levels of the ocean change from season to season.

But prioritizing environmental threats is always difficult and acidification is not always at the top of the list. Just south of Alaska, in the waters off Washington state, there is concern that not enough science is being devoted to the problem despite that the state’s wild oyster beds have failed to reproduce for the past six years—which most scientists agree is directly linked to increases in pH levels. Last week the state’s Department of Ecology failed to include acidification on its priority list of water-quality problems.

“No one can afford to have their head in the sand when it comes to ocean acidification,” said Miyoko Sakashita, oceans director at the Center for Biological Diversity. “Ocean acidification is the biggest threat facing our oceans and is already killing off Pacific shellfish. To ignore the problem of acid seas is a risk to wildlife and communities that depend on healthy oceans.”

As with so many environmental ills, perhaps only when the problem truly impacts man—an exploding nuclear plant, perhaps?—will acidification earn its proper place at the table.

(For the rest of my dispatches, go to

Posted in Ocean Acidification

One comment to “Deaf Fish? An Ocean Acidification Update”

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