How Global Warming Is Dissolving Sea Life (And What We Can Do About It)

March 25, 2014 by admin  
Filed under Featured, Global Warming

How Global Warming Is Dissolving Sea Life (And What We Can Do About It)S

The last time Earth’s oceans were this acidic, a six mile-wide sulphur-rich space rock had just smashed into the Yucatan Peninsula, unleashing a deluge of acid rain that exterminated all sea life in the the top 400 meters of the water column. Now, some 65 million years after the Cretaceous extinction, human activity is threatening to similarly decimate the ocean’s ecosystem—this time, from the bottom up.

How the Oceans Went Out of Whack

Under natural conditions, carbon dioxide is continuously transferred between the ocean, atmosphere, and continents in a delicately balanced process known as the carbon cycle. CO2 is pulled from the atmosphere by photosynthetic plants, which form the base of both terrestrial and oceanic food webs. It’ then subsequently sequestered in sediment when those plants—as well as the animals that feed on them—die and decompose. It’s a nice trick and it helps keep us all breathing.

Simultaneously, a roughly equivalent amount of carbon enters the atmosphere due to air-sea gas exchanges, as well as the respiration of sedimentary microbes as they decompose dead organic matter. Along with the nitrogen and water cycles, this carbon cycle is one of the primary facilitators of life on Earth, constantly recycling the limited supply of carbon that forms the base of every organism alive today.

But since the dawn of the industrial revolution, human activity—specifically, burning coal to produce energy—has upended the balance of the carbon cycle. The concentration of CO2 in the atmosphere has jumped from 280 ppm prior to industrialization to nearly 400 ppm today. We’re pouring more CO2 into the atmosphere than the system can sequester. This excess of atmospheric greenhouse gas has not only resulted in global warming but wreaked havoc on the ocean’s chemistry as well.

How Global Warming Is Dissolving Sea Life (And What We Can Do About It)S

When carbon dioxide enters the ocean, it reacts with seawater to create carbonic acid. This acid in turn produces a secondary reaction, splitting into separate bicarbonate and hydronium ions, which lower the water’s pH level. The more CO2 present in the atmosphere, the more gets absorbed by the oceans, and the lower the water’s pH will become.

Current scientific estimates suggest that the oceans are absorbing roughly 25 percent of the CO2 we produce each year, with another 45 percent remaining trapped in the atmosphere, and the rest being absorbed by terrestrial plants. Between 1751 and 1994, the surface ocean pH has dropped from an estimated 8.25 to 8.14. That may not seem like much but remember pH is logarithmic, just like the Richter Scale, so a .11 decrease constitutes a 30 percent increase in acidity. And if acidification rates continue at their present pace, the pH of the world’s oceans could drop another .5 units—roughly triple the acidity they are right now—by 2100. This would be cataclysmic for sea life and humanity alike.

What This Means for Sea Life

How Global Warming Is Dissolving Sea Life (And What We Can Do About It)S

While an added abundance of atmospheric C02 may be a boon to plant life, the resulting acidification it causes is seriously impairing the development of oceanic calcifying organisms—everything that lives in a calcium-based shell from the phytoplankton, zooplankton, and corals that form the base of the food web to mollusks and crustaceans like clams, oysters, crabs, and lobsters.

Normally, there’s a supersaturation of carbonate ions, which these animals process into aragonite for use in their shells. However, as the pH decreases, calcium carbonate becomes more soluble which reduces the concentration of available carbonate ions. And not only does this reduce the rate at which organisms can build their protective structures, it also increases the rate at which existing shells dissolve. They’re literally being melted away by increasingly corrosive seawater.

How Global Warming Is Dissolving Sea Life (And What We Can Do About It)S

And it’s not just shellfish that are at risk. Decreased pH levels have been linked to a number of other adverse effects—both direct and indirect—such as the CO2-induced acidification of body fluids, known as hypercapnia, the reduced metabolism in jumbo squid, slowed embryonic development in Atlantic longfin squid, the inability of juvenile clownfish (poor Nemo!) to hear and smell approaching predators, and the diminished echolocation capacity of dolphins and whales.

Nowhere, though, is the effect more clearly illustrated than in coral. Both tropical and deep sea coral species, whose calcium carbonate homes form reefs that support entire ecosystems—acting as both nurseries for a number of commercial fish stocks as well as habitat for countless other species—are showing slower rates of growth than in the past and are suffering from the effects of coral bleaching at unprecedented levels. In 2005, for example, nearly half of the coral around the Virgin Islands and Puerto Rico were lost in a single year to mass bleaching events.

How Global Warming Is Dissolving Sea Life (And What We Can Do About It)S

Image: Acropora

The loss of their coral homes only serves to amplify the pressure exerted on existing fish and crustacean populations from overfishing, habitat loss, pollution, and rising sea temperatures. It won’t be long before humanity is directly affected too.

What This Means for Humans

The ocean acts as the primary source of protein for over a billion people worldwide. The US commercial fishing industry exported more than $5.1 billion of fish products in 2012 alone while providing employment for more than a million Americans. We are the fifth-largest seafood producer behind China, Peru, India, and Indonesia—catching just 3.8 percent of the global total annually.

Ocean acidification threatens to topple this industry in the near term if steps are not taken to correct it. The populations of popular shellfish like lobsters, crab, scallops, shrimp, oysters, mussels, and clams are in danger of collapse as the concentration of carbonate ions continues to decline. What’s more, the increased water acidity is doing strange things to crab stocks.

How Global Warming Is Dissolving Sea Life (And What We Can Do About It)S

Image: Sasha Isachenko

Alaskan Red King Crabs—the centerpiece of the Alaskan crabbing industry, which fetched $92.5 million for just 14.8 million pounds in 2011—show a 100 percent increase in larval mortality (twice as many die) when raised in acidified water, though the less sought-after dungeness crabs, which live in the same areas as King Reds, are less unaffected by the pH change. Maryland Blue crabs, on the other hand, will grow three times their average size when raised in lower pH waters and become extremely aggressive predators. Still, should these populations collapse, the damage to the regional fishing industry—not to mention the prices at your supermarket—will take decades to repair.

What We Can Do About It?

Since ocean acidification (like global warming) is the result of human activity, it therefore can be mitigated by changing the way we interact with the environment.

One obvious answer is to simply reduce the amount of CO2 we’re discharging into the air, though that is far easier said than done. While the world’s governments continue t0 work towards a political solution (see: the Kyoto Protocol) and coastal fisheries simultaneously strive to both slow the rate of acidification and adapt to changing water chemistry, there are a number of steps individuals can take to reduce their carbon footprint. And while reducing your personal carbon emissions may not make a very big impact, the actions of 6 billion individuals taken together could very well save the world. [PhysOrg - Wiki 1, 2, 3 - NOAA 1, 2, 3, 4 - NRDC - WHOI - EPA - Seattle Times - Real Science]

top image: Ethan Daniels

Article source: http://gizmodo.com/how-global-warming-is-dissolving-sea-life-and-what-we-1532266705

Calcium, building block for the world

March 4, 2014 by admin  
Filed under Global Warming

It’s the fifth most abundant element on earth - and the world’s building block. Do we fully appreciate the value of calcium?

Most of us are familiar with the idea that our bodies need calcium. I remember being told to drink up my milk because the calcium in it would make my bones strong.

And calcium is indeed the key element in our bones. In fact, it is the most abundant metal in the human body - and in those of most other animals too.

Many organisms use calcium to build the structures that house and support them - skeletons, egg shells, mollusc shells, coral reefs and the exoskeletons of krill and other marine organisms.

And calcium is also the key ingredient in man’s most important structural material - cement.

These days virtually all our architecture, all our great building and engineering projects start with calcium, because cement is the basis of the most widely used man-made substance on earth - concrete.

Fortunately there’s a lot of calcium about - the soft grey metal is the fifth most abundant element in the earth’s crust.

There is plenty dissolved in the sea. For millennia, marine organisms have been combining it with carbon dioxide they fix from the atmosphere to make shells of calcium carbonate.

When they die, their shells and skeletons sink down to the bottom of the sea and collect in great drifts. Over millions of years they have been compacted to form limestone, chalk and marble.

Continue reading the main story

Calcium - key facts

  • Found in sedimentary rocks, including limestone, and minerals such as calcite, dolomite and gypsum
  • Comes from Latin word calx (lime)
  • Used in the making of cement and cheese
  • Pure calcium is a silvery metal, a little harder than lead

When you get the chance, take a close look at a piece of limestone. You’ll probably see the tiny fossils of the ancient marine creatures of which it is composed.

Some 10% of all sedimentary rock is limestone, which is pretty extraordinary when you consider that it represents the concentrated bodily remains of living creatures.

So how do we get from limestone to concrete?

The key is extracting the calcium from limestone. It’s a trick mankind learned very early on.

In principle the process is pretty simple - you just need to heat limestone up.

What you do is place your limestone - calcium carbonate - in a fire where the temperatures are high enough to drive out the carbon atoms as carbon dioxide into the atmosphere. That leaves you with calcium oxide - more commonly known as lime.

Lime is the basis of most cements - the glue that hold rocks and particles of sand together to make concrete.

Recent archaeological discoveries show some prehistoric people created concrete, even before they’d discovered the first metals.

Over the last two decades, a German archaeologist working in Turkey has uncovered what he believes is the world’s first temple. It is a complex of carved stones erected about 11,000 years ago - 6,000 years before Stonehenge.

An early “concrete” was used on the Pont du Gard, constructed out of soft yellow limestone blocks

The site is called Gobekli Tepe - Pot-bellied Hill in Turkish - and features floors made of very early cements.

The technology was refined over the millennia. Two magnificent Roman buildings, the Pantheon and the Pont du Gard at Nimes, showed the potential of concrete.

They used it to enclose space with an unsupported dome, and to bridge considerable spans without reinforcement.

Continue reading the main story

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Nevertheless, these early concretes remained brittle and weak, which is why most buildings continued to be made of stone and brick.

The breakthrough came in the 1840s.

On a rainy February afternoon I went to see the site of this momentous advance. It could hardly be less cherished.

I had an expert guide in Edwin Trout, the chief archivist of the Concrete Society. We met outside WE Roberts’ cardboard box factory on the banks of the Thames Estuary in Kent. Our destination lay deep within the factory complex.

We were led down an alleyway between two big buildings and in through a low door.

We had to duck under a cardboard corrugating machine - a surprisingly large contraption - and then through a door in the wall of the factory.

Portland cement was created inside a bottle kiln

It opened out on to a small courtyard almost entirely taken up by a looming brick structure. It was hard to get a good view, because it was surrounded on all sides by the walls of the factory. Nevertheless, it was clear that Edwin was excited by what he was seeing.

“Portland cement was first developed at this site by a chap called William Aspdin,” he told me.

The brick circular structure, he explained, is one of the earliest kilns used to produce this new cement.

It is known as a bottle kiln, because of its shape, and it was here that Aspdin experimented - burning the limestone by baking it with clay at the then unthinkable temperature of 1450C. The result was a solid amalgam of the two materials known as “clinker”.

Aspdin discovered that when this was ground to a fine powder, it produced an exceptionally powerful cement. And very soon, he got the perfect opportunity to test out his new product.

It came about because of what became known as “The Big Stink”.

At the time, the Thames was essentially an open sewer. The booming population of London, the spread of industry, and the development of the flush toilet, all meant the volume of waste flowing into the river had risen dramatically.

In the hot summer of 1858, the stench became unbearable and there was a public outcry. The London boroughs finally agreed to commission the great network of new sewers that had been proposed by the visionary engineer Joseph Bazalgette.

The builders performed rigorous tests of the various cements on the market in order to choose the very best one for their vast scheme - the greatest public works project ever undertaken.

Portland cement, Edwin Trout tells me proudly, won easily. It was, he says, “stronger, more durable and - by that stage - more widely available too”.

And it is a testament to the strength of the cement - and the power of calcium - that, 150 years later, Londoners are still using the sewers Bazalgette built to flush away their waste.

Indeed, the incredibly strong concrete Portland cement creates has transformed the building industry across the world - as the skyline of every major city shows.

The world produces about 3.5bn tonnes of cement a year. Given that cement is usually between 10% and 15% of the mix in concrete, that’s enough cement to produce about four tonnes of concrete for every person on earth each year.

The problem is that creating all the cement for all that concrete is doubly polluting.

You need vast amounts of energy to get your kiln hot enough to bake all that limestone, and that usually means burning fossil fuels. And the limestone itself produces vast amounts of greenhouse gases, as all the carbon dioxide fixed by those ancient sea creatures is driven into the atmosphere.

Every ton of cement produces almost a ton of CO2. That’s why the concrete industry is reckoned to be one of the most polluting on earth, responsible for up to 5% of total CO2 emissions.

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Article source: http://www.bbc.co.uk/news/magazine-26416749