Ocean acidification creeps up on marine ecosystem in cooler, northern waters

Bristol Bay Under Siege is a three-part series that examines environmental and industry factors affecting Bristol Bay. Parts 2 and 3 focus on oil exploration and the Pebble Mine project.

Bristol Bay doesn’t look like a battleground; there are no obvious battle scars — yet. And there is little development on the shores surrounding the bay that attracts fishermen, hunters, naturalists, environmentalists, photographers and others wanting to visit the area’s state and national parks.

Every summer, the largest run of salmon in the world rushes up its pristine, unspoiled waters into more than a half dozen rivers to spawn.

Bristol Bay is also home to dozens of marine mammal species and one of the world’s largest concentrations of seabird colonies. The endangered Steller sea lion and North Pacific right whale call the bay home.

A study completed for Trout Unlimited says evidence indicates “Bristol Bay has been continuously inhabited by humans at least since the end of the last major glacial period, about 10,000 years ago.”

Its constant high winds, high seas and floating ice make it a harsh environment.

Now, the area is under siege.

Participants in the war include politicians, the oil industry, mine developers, commercial fishermen and environmentalists.

The oil industry wants to develop what they believe to be large pockets of oil and natural gas. The mining industry wants to develop what they believe is one of the largest mineral mines in the world, and the fishing industry just wants to fish in the unspoiled waters for its cut of the $2 billion fishery derived annually from the bay.

Looming over everybody like the Four Horsemen of the Apocalypse is one of the side effects of global warming, ocean acidification — and it threatens to be worse then all other perceived threats.
Ocean acidification

Just a few short decades ago, global warming was an uncertain science. Now, its effects are disputed by only a handful. Last week, the Wal-Mart in Kodiak had a display of films for sale featuring environmental documentaries produced by actor Leonardo DiCaprio, former vice president Al Gore, CNN and HBO.

However, there is another side effect of global warming just now coming to light — a more insidious side effect called ocean acidification. And because cold waters will be affected first, Bristol Bay will be one of the first to see its potential detrimental effects.

Science 101

Oxygen may be the breath of life, but there is a price.

Every time a person or creature breaths, it releases carbon dioxide into the atmosphere. In heavy concentrations, carbon dioxide can kill. Plants have always been able to keep carbon dioxide levels in balance by absorbing gas and releasing oxygen.

That is only a fraction of what is referred to as the carbon cycle.

Then came the industrial revolution and the balance was tilted in carbon dioxide’s favor.

What many of us didn’t learn in high school science classes or have forgotten is that the ocean plays an important part to reduce carbon dioxide levels on earth.

Oceans are a natural absorber of carbon dioxide. In the past 200 years, the oceans have absorbed more than 500 billion tons of carbon dioxide.

“Forty percent of all the carbon that we pull out of the earth goes up into the atmosphere,” Robert Foy, research director of the National Oceanic and Atmospheric Administration research center in Kodiak, said during a workshop at ComFish in March. “Thirty-five percent is a terrestrial sink. It comes back. Trees have to grow. So a lot of that carbon is going right back down into the earth.”

The ocean absorbs the rest.

“Up until now, we’ve been pretty excited about that,” Foy said. “It is what has kept us, since the industrial revolution, pretty steady in terms of the earth’s ability to absorb the impact of humans putting more carbon into the atmosphere.”

Until recently, scientists weren’t sure what effect carbon absorption was having on oceans. Slowly, through experiments, scientists have come to understand and are alarmed about the future of the oceans. The waters off Alaska will be the first to feel those effects.

“Has it impacted us up until now?” Foy said. “Not extremely. This issue is about what it’s going to do (to the oceans) in the future.”

A simple formula

“We call it ocean acidification, meaning the ocean is becoming more acidic,” Foy said. “We probably shouldn’t. We should probably call it removal of carbonate, which is really the issue biologically.”

If you’re not a science major, the actual formula may seem complicated, but the simple version is, if you combine carbon dioxide with water it dissolves into hydrogen ions and bicarbonate ions. That release of ions causes another chemical reaction that removes carbonates and leaves an excess of hydrogen. That excess of hydrogen causes the ocean to become more acidic by decreasing the ocean’s pH level.The lower the pH level, the more acidic water is.

“In the last 200 years, the ocean has decreased its pH by 0.1 pH unit (because of carbon dioxide absorption),” Foy said. “You might think, so what? That’s the difference between milk and water or a Coke. It turns out, biologically, that a pH change by that amount is actually quite large.”

Higher acidification levels can dissolve shells that creatures use for protection.

“A simple example,” Foy said. “Take a can of Coke. Take a shell or piece of chalk or something that is made out of calcium carbonate and stick it in that glass of coke. It’ll dissolve right in front of you.”

Creatures great and small

Pteropod sounds like some sort of huge dinosaur. It’s the opposite. A pteropod, or as they are more often called, sea butterflies, are snail-like creatures and one of the smallest animals in the ocean. They float freely in the water and are carried in currents as they feed on plankton.

There are about 100 different species of the sea butterfly and they are almost at the bottom of the food chain, described by biologist researcher Gretchen Hofmann as the “potato chip of the ocean.”

These sea butterflies use carbonate to build shells.

The Alaska Marine Conservation Council reported that in recent experiments exposing live pteropods to certain carbon emissions, the pteropods showed evidence of damage within 48 hours.

That damage may lead to mass mortality.

If acidity levels continue to increase and pteropods are removed from the food chain, researchers agree it will have a devastating effect on the ecosystem.

Foy said a 10 percent decrease in the sea butterfly would result in a 20 percent drop in mature salmon body weight.

“Pteropods make up 45 percent of the diet of salmon,” Foy said.

Researchers also say that crabs, which use carbonate to build shells, will also be affected.

The May-July 2007 Alaska Fisheries Science Center quarterly report published by the National Marine Fisheries Service states research indicates lower pH levels hurt survival and growth.

It won’t happen overnight.

“Crabs and corals aren’t just going to dissolve one day,” Foy said. “What’s going to happen long before that is their physiology is going to change. They’re not going to be able to grow. We’ll have recruitment failures.”

Foy said fish that end up living in a carbon dioxide-rich layer will most likely not grow as large as before. This will affect their commercial value.

However ocean acidification ends up affecting the oceans, it will affect colder regions first.

According to the quarterly report, “The fishery resources managed by NMFS in the North Pacific are among the most vulnerable to the effects of ocean acidification. The North Pacific has conditions less favorable for calcification due to the increased solubility of calcium carbonate at lower temperatures and the inflow of carbon dioxide-rich waters from deep ocean basins.”

Ralph Gibbs , KodiakDailyMirror.com, 16 April 2008. Article.

Technorati Tags: , ,

  • Reset


OA-ICC Highlights

%d bloggers like this: