Ocean Acidification or Osteoporosis of the Sea?

Posted on September 14, 2016

Kate Leavitt  |  SSC Director of Mission Invitiatives

Image credit: ocean.si.edu
Image credit: ocean.si.edu

If you are unclear about what ocean acidification is and question if it’s occurring in the Gulf of Maine, you are not alone. I teach ocean acidification programs at the Seacoast Science Center and will walk you through the science, the implications for our ocean and for humans, and how it is all playing out right here in the Gulf of Maine. Personally, I’m not a big fan of the label ‘ocean acidification,’ but I invite you to read on and decide for yourself!

At its most basic and elemental, ocean acidification (OA) is being caused by the absorption of atmospheric Carbon Dioxide (CO2) into the ocean’s surface waters. Some call it Global Warming’s evil twin. Both global warming and OA are results of excess CO2 in our atmosphere, however with OA, all of this excess gas is being absorbed into the world’s largest Carbon sink: the ocean. You’ve probably realized by now that CO2 gets a bad rap when it comes to climate-related problems. You might be wondering how this can be, when we know that it is an essential part of many natural processes, like respiration, photosynthesis, and is a vital component of our own atmosphere! The short answer is that due to human-related, or anthropogenic causes, such as the burning of fossil fuels, we are causing an imbalance in the amounts of CO2 being generated, such that nature can’t keep up. CO2 is being produced faster and in greater quantities than it can possibly be absorbed through natural processes.

Graphic credit: www.oceanacidification.org.uk

Okay, so excess CO2 is the cause, but what is the result?

There are actually TWO results, that when acting together, create serious issues for our ocean’s health and ultimately, for us.

The first thing that happens is the direct chemical reaction or change to ocean chemistry, that occurs when CO2 is absorbed into the seawater. Upon absorption into the surface waters, CO2 reacts with water molecules (H2O) to form carbonic acid (H2CO3). Carbonic acid breaks down pretty quickly into a Hydrogen ion (H+) and a Bicarbonate (HCO3) anion. Since pH is actually the measure of hydrogen ion concentration in a liquid, an increase in H+ ions will result in a change in pH levels. The lower the pH, the more acidic something is, and the higher the pH, the more basic it is.

So, more H+ ions results in a more acidic solution. One might wonder, if we consume acids, like coffee and orange juice, on a daily basis that do not negatively impact our health, why do small changes in pH matter in the ocean? Living things have adapted to certain conditions over time. Changes in ocean acidity are happening faster now than some species can adapt. Because the pH scale is logarithmic, seemingly small changes, like from 8.1 to 8.0 are actually quite large. A one-unit change from pH 8.0 to pH 7.0 actually results in something becoming 10 times more acidic!

And, something else is going on in addition to changing pH levels. The changing ocean chemistry is reducing the amount of Calcium Carbonate in the ocean. So what, you ask? Well, just as we need calcium to build our bones, many sea creatures, and even some phytoplankton, need calcium carbonate to build their skeletons and shells. However, when there is too much CO2 in the water, it binds with water (H2O) to form carbonic acid (just like we talked about above), resulting in excess H+ ions. These excess H+ ions bond with the available carbonate in the water. This means that instead of bonding with the calcium to form calcium carbonate (the building blocks of shells), bicarbonate is being formed. When there is less calcium carbonate in the water, fewer “building blocks” are available, making it harder for organisms to build and strengthen their shells.

If animals and plankton have a harder time building their shells, there are all sorts of implications — they may have thinner, more fragile shells and not grow quite as large. In turn, their defense is weakened. Crabs, lobsters, snails and clams, for example, are showing this effect. Sometimes you see evidence of the calcium carbonate shells when you look at the animal, and with others, it might be hidden in the form of internal skeletons, feeding appendages, and other internal body parts.

Other organisms, like phytoplankton, might use calcium carbonate to build their outer shell. Phytoplankton are very important; they are base of the marine food chain, using CO2 during photosynthesis to produce oxygen, and also for providing food for hungry herbivores. Marine photosynthesizers, like plankton, play a huge role in our daily lives. Every breath we take contains oxygen produced in the ocean; over 50% actually! Where would we be without all of this phytoplankton? And where would all those hungry animals find food?

If organisms at the bottom of the food chain are not growing or thriving, then those that rely on them for food will not grow either. This effect ripples throughout the marine food web, effecting not just the little guys, but the largest animals in the ocean as well.

How does this all affect you and me? Humans are inextricably linked to the health of the ocean. In addition to the oxygen provided by the ocean, we rely on the ocean for food, recreation, transportation, and medicines. Some refer to the ocean as our climate’s heart, comparing its role in regulating global climate to the role our heart, regulating the flow of blood throughout our body. Our ocean controls the circulation of heat and moisture throughout the climate system and our global climate is changing. As you can see, there are connections between our personal health and the health of the ocean.

Ocean acidification is happening right now, and it is happening here in the Gulf of Maine. In fact, the Gulf of Maine is experiencing unprecedented change, and is one of the places on the planet that is most vulnerable to OA. Why? A few reasons. Shifting deep water current patterns, occurring since 2004, are resulting in the Gulf of Maine experiencing the 2nd most rapid warming on the entire planet. Many species are moving north or to colder, deeper waters. Cold water, the key to the Gulf of Maine’s healthy fisheries and great productivity, also tends to absorb CO2 at a higher rate than warmer waters. As you recall, from above, increased CO2 absorption results in acidifying conditions, and reduced calcium carbonate availability. Finally, the Gulf of Maine watershed is quite large, and all precipitation in this region ends up in the Gulf. This freshwater runoff from rivers brings pollutants and more acidic water straight to the estuaries and coastal waters, places where larval development is very important.

So, what can we do about it? Sometimes it might feel like some of these problems are too big for us as individuals to affect, but don’t worry, there is plenty we can all do and we can walk you through it. You are already doing one of the most important pieces: arming yourself with knowledge and learning more about the situation. Digging deeper and sharing what you learn with others is very important. Because excessive atmospheric carbon dioxide is the ultimate cause, reducing carbon emissions and reducing your carbon footprint are very important. Try to stay away from single use products, like plastic water bottles, straws, and do your best to reduce consumption, reuse when possible, and always recycle. Being mindful of your transportation choices, purchasing energy efficient appliances, and switching to solar power are a few great ways to reduce CO2 emissions. Check out this EPA guide for other ideas. Want to make some positive choices at home to keep your local waterways healthy? Check out this website to get ideas on ways to decrease and counteract coastal ocean acidification.

Humans have accelerated this process, but we have the ability, knowledge and capacity to slow things down and reduce the effects. Sharing our knowledge, and learning more about the interconnectedness between humans and the oceans is essential. We have one big ocean, it supports a great diversity of life, makes our earth habitable, and even regulates our climate. Let’s make good choices and Live Blue!

Watch this short animation about the potential impact of ocean acidification on sea life in the Gulf of Maine. Produced with support from Maine Sea Grant, Dalhousie University, MEOPAR (Marine Environmental Observation Prediction and Response Network), NERACOOS (The Northeastern Regional Association of Coastal Ocean Observing Systems) and NECAN (Northeast Coastal Acidification Network).

Are you a teacher?

Interested in exposing your students to ocean acidification programming? Contact Sarah Toupin at s.toupin@sscnh.org or 603-436-8043, ext. 20 to learn more about onsite and distance learning programs.

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