Shore Lab Discovery Center Blog
Our Acid Seas
Climate Change, you hear the term daily. It is poorly understood and has split opinions around the globe. However, CO2 emissions are degrading our atmosphere and oceans at an alarming rate. Our planet can no longer keep up with the continued industrialization of the planet. We need to find solutions or we will face a tragic future. The great astrophysicist Steven Hawkins has estimated that humankind, in the next 1000 years, will have irreversibly alterated the planets atmosphere and depleted Earth’s resources. Humankind and our planet will go extinct. Well you say that’s a pretty long time from now but why does that mean to me today? To answer that we have to go back to the beginning of this story and look at the root causes. It started at the beginning of the 20th century with the industrial age. Let’s back up even further to talk about climate changes that our earth has experienced over the millennia. The planet has been on a roller coaster ride of cooling and warming for billions of years. In fact we are coming out of a glaciation period that ended about 12,000 years ago.
To find a period analogous to what is going on now, you have to go back at least 55 million years, to what is known as the Paleocene-Eocene Thermal Maximum. During the PETM huge quantities of carbon were released into the atmosphere. The source of the carbon is still under speculation but it may have come from seeps under the ocean floor. Temperatures around the world soared by around ten degrees Fahrenheit, and marine chemistry changed dramatically. The ocean depths became so corrosive that in many places shells stopped piling up on the seafloor and simply dissolved.
The PETM, while extreme, was not as extreme as what's happening today. The PETM took place over thousands of years, slow enough for the chemical effects to spread through the entire ocean. Today the rate of carbon emissions is roughly ten times as fast, and there's not enough time for the water layers to mix. In the coming century acidification will be concentrated near the surface, where most shell building organisms and all tropical corals reside.
So what makes this all so different today versus 55 million years ago? The emergence of humankind and Industrialization. Humankind is the largest consumer of resources on the planet. Our numbers are growing by the billions and the planet’s resources are finite. We are entrepreneurs. We make up crazy stories like “if you eat the gill cartilage of a Manta Rays it will cure your cancer”. So we try and kill every last Manta Ray on the planet to make a sale, under the pretenses of a cure. Then we lobby for protection for Manta’s to CITIES who controls the financial trade in the Manta’s. Crazy, right?
Since the start of the industrial revolution in the 20th century, enough fossil fuels coal, oil, and natural gas have been burned to emit more than 500 billion tons of CO2 into the atmosphere to eventually wind up in our oceans. The atmosphere now has a higher concentration of CO2 today than at any point in the past 800,000 years.
Carbon emissions are changing the oceans. In the 1990s an international team of scientists undertook a project that involved collecting and analyzing more than 77,000 seawater samples from different depths and locations around the world. The project lasted for over 15 years. It showed that the oceans have absorbed 30 percent of the CO2 released by humans over the past two centuries. They continue to absorb roughly a million tons every hour.
So it’s not just that these epoch events are cyclical and will happen anyway. It’s that this one is racing us to extinction and fueled by the CO2 we put into our atmosphere. For life on land; every ton of CO2 the oceans remove from the atmosphere is a ton that's not contributing to global warming. But for life in the ocean a great disaster is unfolding. The head of the National Oceanic and Atmospheric Administration, has called ocean acidification global warming's "evil twin."
The pH scale, which measures acidity in terms of the concentration of hydrogen ions, runs from zero to 14. At the low end of the scale are strong acids, such as hydrochloric acid, that release hydrogen readily (more readily than carbonic acid does). At the high end are strong bases such as lye. Pure, distilled water has a pH of 7, which is neutral. Seawater should be slightly basic, with a pH around 8.2 near the sea surface. So far CO2 emissions have reduced the pH by about 0.1. Like the Richter scale, the pH scale is logarithmic, so even small numerical changes represent large effects. A pH drop of 0.1 means the water has become 30 percent more acidic. If present trends continue, surface pH will drop to around 7.8 by 2100. At that point the water will be 150 percent more acidic than it was in 1800. The acidification that has occurred so far is probably irreversible. Even if CO2 emissions were somehow to cease today, it would take tens of thousands of years for ocean chemistry to return to preindustrial condition.
The biggest losers in our acid seas are the corals. Coral polyps are tiny animals that form a thin layer of living tissue on the surface of a reef. They're shaped like flowers, with six or more tentacles that captures food. External sources of food are a small fraction of what coral polyps consume. They get a majority of their food from algae that lives symbiotically within the polyp. The algae photosynthesize inside the polyp providing food for the coral. Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can be later released to fuel the organisms' activities. This chemical energy is stored in carbohydrate molecules such as sugars, which are synthesized from carbon dioxide and water.
Corals are also builders, each polyp surrounds itself with a protective, cup-shaped exoskeleton of calcium carbonate that contributes to the collective skeleton of the whole colony. To make calcium carbonate, corals need two ingredients: calcium ions and carbonate ions. Acids react with carbonate ions, in effect tying them up. So as atmospheric CO2 levels rise, carbonate ions become scarcer in the water, and corals have to expend more energy to collect them. Once a reef can no longer grow fast enough to keep up with erosion, this community will crumble.
Corals are just one kind of calcium dependent that is being affected by ocean acidification. There are thousands of others. Crustaceans like barnacles, sea stars, sea urchins, clams, oysters and coralline algae (their calcium carbonate secretions help cement coral reefs together). Scientists are beginning to explore the ways that ocean acidification is affecting more complex organisms such as fish and marine mammals. Changes at the bottom of the marine food web will inevitably affect the animals higher up.
So what this means to you is that your children’s children will live in a different world then you or I live in today. It will be barren of all that we currently take for granted. The beauty and majesty of our blue water planet will be gone. We would have destroyed their heritage. It's still possible to change all this by dramatically reducing CO2 emissions. At the moment, our oceans face a global economy built on cheap fossil fuels. By 2050 CO2 concentrations in the atmosphere will be roughly double what they were in preindustrial times. We need to halt or greatly curtail CO2 emissions and find alternatives to fossil fuels. Humankind needs to find ways to live sustainably. The time to correct the destruction to our planet is now in the 21st century. We owe our children their inheritance. There is no wiggle room. It’s now or never.