Temas Especiales

19 de Jan de 2021

Nacional

Oceans on acid: life at risk

CALIFORNIA. When we burn fossil fuels, we are not just putting carbon dioxide into the atmosphere. A lot of it goes into the sea. The...

CALIFORNIA. When we burn fossil fuels, we are not just putting carbon dioxide into the atmosphere. A lot of it goes into the sea. There, carbon dioxide turns into carbonic acid. And that turns ocean water corrosive, particularly to shellfish and corals.

Biologists are now coming to realize that rising acid levels in the ocean can affect many other forms of sea life as well.

Visit Moss Landing, Calif., in the spring and at first blush it seems marine life is flourishing. Sea lions, weighing in at 600 pounds or more, jostle for space and spar with one another as they try to cram themselves onto docks that groan under their weight.

Marine biologist Eric Pane looks on approvingly at what seems to be part of a Pacific success story. Up and down the coast, biologists see healthy populations of marine mammals, fish and other wildlife.

But as we cross the street and head into his laboratory at the Monterey Bay Aquarium Research Institute, Pane's outlook about the future of life in the sea takes a dark turn. His budding career as a marine biologist is framed by an ominous trend: civilization is venting carbon dioxide from tailpipes, smokestacks and chimneys at a prodigious rate.

"And at least a third of it so far, has actually ended up in our oceans," Pane says. "(That's) sort of good and bad news because it has prevented more CO2 from accumulating in the atmosphere but it comes at a price. More CO2 in the ocean leads to it being acidified." Acidity is measured on the pH scale. Already, the oceans are a tenth of a unit more acidic. And by the end of the century, the pH is expected to change by half a unit. But don't be fooled by these modest-sounding numbers.

"So we say 'only' — 'only' half a unit. What's the big deal about that? Well, that's a tripling of acidity," Pane says. "That's a three-fold increase. That's because the pH scale is logarithmic, so each unit increase actually represents a ten-fold increase in acidity.

EXAMINING ACIDITY'S EFFECTS ON ANIMALS

Over the past half-dozen years, marine biologists studying ocean acidification have focused mostly on the animals they assume will be the most vulnerable, such as coral reefs and shellfish. If acid levels in the ocean get too high, their shells can literally dissolve.

Pane is part of a second wave of research on ocean acidification as biologists try to understand the consequences for all the life in the sea. A change in acid can actually impose a subtle "energy tax" on marine animals. They already use some energy pumping acid out of their cells to maintain a healthy pH. As the oceans get more acidic, Pane says, the animals will be forced to expend more energy to maintain that balance.

That means less energy for such things as growing and reproducing, Pane says.

Marine biology sounds to most people like an exciting career, but Pane says his work is actually a bit depressing. "Within a few years there's going to be change basically, and I'm not sure how it's going to work out."

CHANGING THE OCEAN'S CHEMISTRY

There are just a few people in the world who have actually been thinking about ocean acidification for decades. And one of those is down the hall from Pane. Peter Brewer realized that something was amiss with the ocean's chemistry back in the 1960s, and he's seen the problem grow much, much worse.

"The quantity of carbon dioxide we've put in the ocean is now well over 500 billion tons," he says. "And you can't just transfer that much mass without making changes to the physical properties as well as the biological properties."

Scientists may simply have to wait and watch to see how that unintentional human experiment evolves. Hopefully before the oceans suffer irreparable harm.