Ocean Acidification

The science behind ocean acidification is not as complicated as it may sound, but it will help to refresh your memory about the basic concepts of the pH scale and how it relates to the chemistry of the world’s ocean.  Many people will forget this information as soon as they pass their chemistry exam, and will never think about pH again unless it relates to their fish tanks, swimming pools, or deodorant for women.  pH is a measurement of the amount of hydrogen ions in a solution, and the scale goes from 0 to 14.  pH values between 0 and 7 are considered acidic.  Values between 7 and 14 are basic.  A solution with a pH of 7 is considered neutral.  It is important to remember that being labeled an acid or a base is not a bad thing, many things that we consume regularly (like orange juice and soda) are acids.  What is important is that living things have adapted to cope with specific pH ranges, and the pH of ocean water is decreasing faster than many animals can adapt.

• The pdf resource included in this lesson is a huge overview of ocean acidification and its effects on coral reefs.  For the purposes of this lesson: go over pages 11-14 for a brief explanation about ocean pH.
• There is also a video of this same presentation with the speaker, Dr. Dwight Gledhill, discussing the science of ocean acidification.  The video is 30 minutes long, but you can watch the first six minutes of this talk to focus on the chemistry and science of ocean acidification.
• For kinesthetic learners, check out the first lab activity from the “Ocean Acidification Lab Activities” pdf file.  The experiment is called Student Activity 1: Is Seawater More Like Lemons or Bleach?”  The pH testing activity can be done with students, staff, volunteers and visitors!
• Stanford University’s virtual urchin lab is a fun and easy way to refresh about acids, bases and the pH scale.  You can familiarize yourself with familiar acids and bases, and also see how ocean pH has changed since the industrial revolution.  http://virtualurchin.stanford.edu/AcidOcean/AcidOcean.htm

Ocean acidification represents a direct chemical change to global ocean chemistry in response to rising levels of atmospheric carbon dioxide (CO2).

Carbon dioxide is responsible for many of today’s climate change-related issues.  Because CO2 gets blamed for global warming and ocean acidification, this essential gas gets a bad reputation.  Remember, plants need CO2 for photosynthesis, so it is a valuable component to our atmosphere.  Historically, there has been a balance between CO2 being generated, and CO2 being taken in.  The problem now is that CO2 is being created faster than it can be absorbed through natural processes.   It is excess carbon dioxide that is the problem.

Ocean acidification occurs when CO2 is absorbed into the water at a high rate.  It reacts with water molecules (H2O) to form carbonic acid (H2CO3).  This compound then breaks down into a hydrogen ion (H+) and bicarbonate (HCO3-).  The presence of all these hydrogen ions is what decreases the pH, or acidifies the ocean.  This can be summed up with a nifty chemical equation:

CO2 + H2O -> (H+) + (HCO3-)

The saga does not end here, unfortunately.  That carbonate molecule (HCO3-) is going to go on to cause trouble for marine organisms. This will be discussed in unit 2.

• Read pages 3-12 of the pdf Ocean Acidification: Coral Reefs In The Balance.  It has good diagrams and graphs of the global carbon cycle.
• Also, check out Stanford University’s virtual sea urchin lab for a fun and interactive lesson about atmospheric CO2 levels and also about how CO2 is absorbed by the ocean. http://virtualurchin.stanford.edu/AcidOcean/AcidOcean.htm
• The lab activities pdf has an experiment where you can cause ocean acidification on a small scale in an indivual cup of seawater.  It is called “Student Activity 2: Ocean Acidification in a Cup”.

Many organisms that form the basis for the marine food chain are going to be affected by ocean acidification.  It turns out that changing the pH of the ocean is not the only impact from this phenomenon.  There is another, equally impactful side effect.  When carbon dioxide (CO2) mixes with water molecule (H2O) it forms carbonic acid (H2CO3) that then breaks down easily into hydrogen ions (H+) and bicarbonate (HCO3-), those available hydrogen ions bond with other carbonate ions to form more bicarbonate.  The problem here is that marine organisms possessing shells (many mollusks, crustaceans, corals, coralline algae, foramaniferans) need available carbonate ions to form the calcium carbonate (CaCO3) that comprises their shells.  In essence, ocean acidification is robbing these organisms of their necessary building blocks.

There have been scientific experiments focusing on how the projected acidity of the oceans will affect different organisms.  Marine pteropods already have thin shells, and these shells literally dissolve over 30 days in seawater with a 7.8 pH.  Studies on sea urchins and mollusks show similar results.

There are many resources included in this lesson, and many of them are going to say the same things, but each resource does a good job of explaining a certain part of the ocean acidification story.

• Start with the pdf slideshow called Ocean Acidification: effects on marine organisms.  It is the best overview and it has informative slides which can be presented or printed.  It covers the whole topic and even has some great solution pages.
• Ocean Acidification is a short 2-minute video from North Carolina Aquarium that explains how marine organisms build shells from calcium carbonate, and how ocean acidification impedes that process.
• NOAA’s Ocean Acidification: The Other CO2 Problem video is 4 minutes long and shows the results of acidifying water on marine pteropods, one of the delicate creatures at the bottom of the food chain.
• NOAA Ocean Acidification Intro and Classroom Demonstrations is a 15-minute video that has some really great hands-on and visual representations of calcium carbonate dissolving in acid, and of CO2 turning water more acidic.
• For a more hands-on approach, or if you’re interpreting for the classroom or in a lab-like setting, download the Lab Activities pdf.  The third experiment “Group Demonstration: I’m Melting!  Seashells in Acid” is focysed on the effects of increased acidity on seashells.
• Watch the 6-minute Acid Oceans video to get a good feel for how Ocean Acidification will affect sea urchins.  There are scientists doing research on the effects of acidity on urchin larval development.
• Climate Training Activities shows some actual interpretation from Aquarium staff, using props and visuals to show visitors about the impacts of ocean acidification to shellfish and corals.

Most people are familiar with the concept that compares coral reefs to underwater rainforests.  Coral reefs form the most biodiverse habitats in the ocean, and their presence is essential to the survival of thousands of other marine species – many of which we rely on for food.

Hard corals are the reef-building corals, and their stonelike structures are composed of calcium carbonate, the same substance found in the shells of many marine organisms including oysters, clams and snails.  Like these mollusks, corals must have access to available calcium in the seawater in order to build their hard skeleton.  This is especially important in the early stages of a coral polyps’s life, when it settles onto a hard substance and starts “building” its skeleton.  Some studies have shown a 52-73% decline in larval settlement on reefs that are experiencing lower pH levels.  Scientists can also measure the calcification rates of hard corals, and ocean acidification has had a negative impact on the rate at which corals calcify.  This means that coral colonies in the future may be more brittle and less resilient to other factors influencing their survival.

Ocean acidification is just one more threat to the success of hard corals.  Coral reefs are already being affected by many other pressures, some human-related and some natural.  Warming ocean temperatures are contributing to coral bleaching and making them more susceptible to diseases.  Nutrient and chemical pollution coming into the oceans from rivers is also making suitable coral habitat very scarce.  Natural threats impacting coral reefs include predation from urchins and a variety of fishes, and also tropical storms.  Coral reefs are naturally very resilient to many of these threats, but now their ability to recolonize and grow sturdy structures is being compromised by ocean acidification.  Sometimes, coral habitat is gradually being replaced by non-calcifying organisms, like seagrass, once the coral has been killed off.

The resources included in this lesson will describe many of these processes, and will also provide suggestions for how to protect coral habitats.  Protecting oceans as a whole will help corals maintain resiliency in the face of these threats.

• PBS created a 7-minute documentary titled “Coral Reefs Die as Ocean Temperatures Rise, Water Acidifies”.  This is a great video to watch because it shows scientists researching corals in lab conditions, and trying to “forecast” how corals will respond to acidity changes in their water.
• The majority of the 30-minute talk “Ocean Acidification: Coral Reefs in the Balance” deals with the impacts of OA on coral reefs.  Much of this information goes beyond what we need to interpret for general audiences, but it may be good to know if you want to be prepared for anything!  Pages 15-35 of the powerpoint focus on coral reefs.  The coral reef topic is covered in the video from 6:00-25:45.
• “Climate Training Activities” shows Aquarium interpreters explaining why ocean acidification is detrimental to hard corals, and how suitable coral habitat is shrinking in the near future.
• The short animation shows the past, present and future of suitable coral reef habitat.  It only plays for 16 seconds, so you may need to pause it or slow it down to catch what’s happening.

Ocean acidification will have drastic effects on shelled organisms and on coral reefs, but what about its effects on humans?  Many people mistakenly believe that the oceans may be turning to acid, and that it will no longer be safe for humans enter the water.  This is not true, even in the most extreme scenarios for the next century.  An ocean pH of 7.8 is in not directly harmful to humans, in fact many swimming pool maintenance guides suggest that people keep their pool pH between 7.2 and 7.8.

So, why would ocean acidification be detrimental to human health?  The previous two lessons were focused on the marine food chain and on the coral reef ecosystem.  Humans are inextricably linked to the health of the ocean.  We have always relied on the ocean’s resources for food, recreation, transportation and medicines.  From an interpretive standpoint, the important thing is to help people realize how they are personally connected to the ocean, and then to be able to explain to them how that connection is being jeopardized by ocean acidification.  One of the most obvious connections people have with the ocean is seafood.  Most of the shellfish we eat are going to be negatively impacted by ocean acidification due to the fact that they will be unable to build sturdy shells.  Some oyster hatcheries in the Pacific Northwest have already been impacted, and have seen declines in larval settlement and survival rates.  Pteropods may seem insignificant to many people, but since they are a major food source for fish, their survival is very important to us.

Most people recognize the aesthetic qualities of coral reefs, but it is important that people realize the vital role reefs play in our daily lives.  There is a good chance that people are already connected to at least one of these roles, and NOAA’s coral reef website  http://coralreef.noaa.gov/aboutcorals/values/ breaks it down in a user-friendly manner by dividing the value of coral reefs into five categories:

Biodiversity http://coralreef.noaa.gov/aboutcorals/values/biodiversity/

Coastal Protection http://coralreef.noaa.gov/aboutcorals/values/coastalprotection/

Fisheries http://coralreef.noaa.gov/aboutcorals/values/fisheries/

Medicine http://coralreef.noaa.gov/aboutcorals/values/medicine/

Tourism and Recreation http://coralreef.noaa.gov/aboutcorals/values/tourismrecreation/

Ocean acidification is occurring because too much carbon dioxide is being released into the atmosphere.  Carbon dioxide is nothing new, and its presence in moderate quantities is not a concern.  The rate at which we are pumping it into our atmosphere is a concern, however.  There are two major sources for this influx of atmospheric CO2: fossil fuel emissions and deforestation.

Fossil fuel emissions are the gases that are spewed out of most cars, airplanes, power plants, and factories that are burning fossil fuels (coal, oil or gas).  Since the industrial revolution, fossil fuel consumption has risen exponentially to create many climate change-related issues, including ocean acidification.

Deforestation is a two-fold issue.  Burning down forests is similar to burning fossil fuels, it emits a lot of carbon dioxide into the atmosphere.  Forests are important because large expanses of plantlife (even in the ocean) are known to be “carbon sinks”,  taking in carbon dioxide for photosynthesis.  Historically, carbon dioxide levels have been balanced; the CO2 being produced was in turn being absorbed.  Deforestation not only creates more CO2, but it also destroys one of the very things that helps absorb it!

The silver lining here is that ocean acidification is just one more symptom of ailments that people are already aware of.  Most people know that deforestation is bad for the environment.  And most people know that they should try to drive less, and consume less energy.  Ocean acidification brings the problem into the ocean, and to a world many people are not familiar with.

• “Acid Test” is a video narrated by Sigourney Weaver.  It does a fairly good job of explaining how people are responsible for ocean acidification, as well as providing some urgent calls to action.
• “Ocean Acidification: Coral Reefs in the Balance” features human causes right at the beginning.  Pages 3-10 of the pdf document focus on where all this excess CO2 is coming from, and shows the relative amounts that are coming from emissions and from deforestation.
• “Switch Energy Project: Oil” is a succinct film about why we rely on oil as the main source of transportation fuel.

Now that we know some of the anthropogenic sources of CO2 in the atmosphere, what can we do about it?  All of the things we have been doing since the industrial revolution to put CO2 into the atmosphere should be examined to find more efficient uses.   There are many solutions available, and there are things that people can do on almost any level to make an impact.  People should understand that some of these changes need to be made on an individual basis, some on the community level, and all the way up to corporations, governments and global organizations.

The burning of fossil fuels is the major contributor to ocean acidification.  Fossil fuels are burned to produce energy, and to make vehicles run.  One of the easiest ways for people to have a positive impact on an individual level is to use less energy.  Many people already think of energy as electricity, so convince people that conserving electricity will save them money and will also reduce the amount of energy their power plant needs to produce.  But fossil fuels are also burned in factories to make products that we use every day.  The saying “reduce, re-use, recycle” also applies to the ocean acidification crisis.  Using less products will lead to a decreased demand to create new product out of new materials.  Every person should be able to think of a way they can consume less in their daily lives.   Transportation is a huge concern, and is one that is difficult for people to make adjustments to.  Driving less and using public transportation may not be a realistic option for everyone, but people can make sure their automobiles run efficiently by keeping the tires properly inflated, getting their cars serviced regularly, and by choosing fuel efficient vehicles.  There are many resources listed below which offer some tips, and also offer ways to engage people in learning about their daily energy choices.

Protecting wildlife has many benefits, but most people don’t know that it’s an important factor in how the Earth responds to climate change.  Natural places are very resilient to change, but now there are far fewer natural places in most areas.  It is important to preserve existing habitats and to identify more areas that need protection.  Visiting natural parks is a great way to experience nature, but also provides funding for protecting those areas.  Monitoring pollution and nutrient run-off helps protect coral reefs, so they can be healthy enough to withstand global warming and ocean acidification.  Purchasing products that are grown in coexistence with forests and rainforests decreases the need for deforestation for agriculture.  Even eating sustainable seafood can make a difference, because healthy fish populations are essential to the overall success of the coral reefs and the ocean.

Since ocean acidification is yet another side effect of excess CO2, there are many things that people are already doing that help make a difference.  In short, most things that are considered “green” options, or are environmentally friendly, will also help fight the effects of ocean acidification.

• “The Acid Test” video will discuss some ways to help fight ocean acidification, from individual to big-picture solutions.
• Pages 28-30 of “Ocean Acidification: effects on marine organisms” show ways to emit less CO2.
• The Nature Conservancy’s carbon footprint calculator is a user-friendly website, and a good place to start for people who are not aware of their impact on the environment.  It will provide them with some options in different aspects of their daily lives.
• Ocean and Climate Defender is a really fun way to get some ideas about lessening your carbon footprint.  It allows you to make all types of “green” modifications in your community, and also provides a pledge form to encourage people to make a change now!
• Watch the “Kill-A-Watt” video about how University of Central Florida students started a campus competition to encourage dorm residents to use less energy.  It also provides some really simple, cheap ways to conserve.  If you’re interpreting to teens and young adults, these ideas will be really useful!
• There are several Climate Training Activities listed below, and all feature great interactive ways to interpret to general audiences about their impacts on climate change.
• Alex Laskey’s TED talk about what motivates people to make changes will surprise you!  This video may have an impact on how you encourage visitors to take that next step into action.
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