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Unique and Topical Science Fair Project Idea: Ocean Acidification

Posted by on September 9, 2012

Question: How will changes in ocean water chemistry affect animals that live in the ocean?

Step 1: Research

Examples of animals without backbones include the animals that made these shells

Search for “Ocean Acidification” and look for websites by NOAA or NSF or from a University/College.

DO NOT get overwhelmed by the chemistry. The essential idea is that ocean water is naturally basic (pH ~ 8) but with all the carbon dioxide in the atmosphere, some of it diffuses into the ocean and shifts the pH to something lower (i.e. less basic = more acidic). The name is a bit of a misnomer in that the ocean is becoming more acidic, but it is not necessarily becoming an acid. Regardless, this project looks at the effect of pH changes on marine life.

Note: acids have a pH of less than 7 and bases have a pH of more than 7. Ocean water has a pH about 8 – and that might not sound like much of a difference from neutral (= 7), but because pH is a logarithmic scale (just like earthquakes), each change of 1 unit = 10x. A change of 2 units is really a 100 fold (10 x 10) difference.

Also decide which animals you want to determine the potential impact on – the best choices are mollusks, crustaceans, or echinoderms depending on what you have access to. Go to a seafood restaurant or seafood department of the supermarket and ask for left-over oyster, mussel, clam or scallop shells (all mollusks), or crab, shrimp, or lobster shells (crustaceans), or sea urchin shells (echinoderms).



Step 2: Design your own unique experiment

Question: How will changes in ocean water chemistry affect animals that live in the ocean?

The question is already in the right format: How will X affect Y?

X is your independent variable so it will be the one that you manipulate.

Y is your dependent variable so it will be the one that you measure.

Therefore, the experiment will need to change water pH and measure a change to the shells. If you don’t have access to real ocean water, you can make your own by buying the salts at a pet store or online. You can also buy pH strips or pH test kits anywhere aquarium supplies are sold.

Figure out a way to change the pH of ocean water (hint: vinegar is an acid and bleach is a base – be careful with bleach!).

Now figure out a way to measure a change to the shells — think about: if the shell dissolves how will you measure the change in size? (hint: differences can be measured as absolutes or percentages).

Don’t forget replication. You will need 3 shells for your control condition (ocean water with no change in pH) and 3 shells for your experimental condition (ocean water with a different pH).

Creative twists: compare different animals or different types of animals, compare different pHs, compare different times, etc.

Final hint: Take photographs!

Good Luck – Oh and it may take a few weeks to months (depending on pH selected) to see noticeable changes, so set it up in a place that it will not be disturbed – NOT THE KITCHEN TABLE!!!

20 Responses to Unique and Topical Science Fair Project Idea: Ocean Acidification

  1. Compression Wear

    My sister saved this website for me and I have been reading through it for the past several hours. This is really going to assist me and my friends for our class project. By the way, I like the way you write.

  2. geetha krish

    My daughter wants to do a project on “ocean acidification and its effect on coral reef. ” She is a eight grader. Her science fair is in third week of march. Do you think there is enough time for this project.

  3. aleeza

    hi my daughter is doing a project like this and she wanted to know how we can prove to the judges that the acidification affected the animals( she is using shells). Now if we were to weigh it
    how much would the difference be ?? should it be lower or higher.

  4. Meera

    Hello, My son and his buddy want to study the effect of sunscreen on aquatics, as they researched that oxybenzone which is present in most sunscreens is harmful to aquatic animals and coral reefs. But they do not know how to test the same. They want to know if they can use pond snails for this experiment and experiment adding different amounts of sunscreen in the water and study the effect on the snails and coral reefs.Do you think they can use shells instead of animals? and would that cover coral reefs too or do they have to use real coral reefs? Can they use similar experiment for ocean acidification?

    • Dr. Maille Lyons

      First, make sure they have permission to work with animals. Although snails are not vertebrates, some schools prohibit working with all live animals.

      So… I like the idea of using shells instead of animals since it looks like they’d be looking for a negative effect (i.e. harming the snails); but I do not think the effect would be measurable on shells (unlike pH which results in a measurable difference in shell size). The problem with many harmful sunscreens is their interaction with the soft tissues of aquatic organisms.

      I don’t know how they would use “real” coral reefs as keeping live corals in a tank is a skill (and an expensive one at that). I don’t know a single person who maintains saltwater tanks that would allow anyone to dump a toxic chemical into their tanks.

      So… how about looking at effects on aquatic plants? They could set up tanks with the same aquatic plant (elodea maybe; or really anything sold at a local pet shop) and then put different amounts of sunscreen in each tank. They could have 2 tanks, 1 with and 1 without sunscreen; but would be better to have at least three tanks – no sunscreen, a lot of sunscreen and 1/2 as much – so a zero, medium and high amounts. They could take photos and document color loss (yellowing of leaves) and count the number that “die”.

  5. Meera

    Thanks a lot for your valuable inputs. Really appreciate it. His school does permit experiment on invertebrates, with due permission obtained before starting the project.But agree with you that aquatic plants would be right bets. He plans to use many jars, one with zero amount, one with medium, one with high amount and also one with a sunscreen without oxybenzone and another with coconut oil, which is supposed to be an alternative to sunscreen. Do you think it is a good idea to have so many jars/variables??

    Also, he is also considering the ocean acidification experiment on shells as an alternative, as you mentioned that it results in a change in size of the shells. If he does choose to do you suggest to use the shells picked up from oceans or the store bought ones? and is it better to use ocean water rather than make our own?And is weighing the shells is a better option than just pointing with pictures out that they became smaller? Pls advice.

    • Dr. Maille Lyons

      Remind him that he will need 3 jars per treatment (i.e. sunscreen) per dose. So just doing one type of sunscreen a zero, medium and high is already 9 jars (which might require aeration depending on how long it takes to see an effect). The more he does, the more complex the experiment, the more data … usually results in a better (i.e. more advanced) project.

      For acid acidification, you can measure the shells with photos or by weighing. I recommend going to your local seafood supplier and asking for left over clam, oyster, mussel, scallop etc. shells. (use all the same kind or test different types of shells)

      If you have access to “real” ocean water you could use it, but you’ll need to filter it to make it as homogenous as possible. You can also buy Instant Ocean TM and make your own.

  6. Meera

    Also, do you advice using daphnia along with plants for this project?

  7. Meera

    Thank you very much for all your guidance and recommendations. Yes, we do have easy access to ocean water, but I guess the filtering process can be tedious. So he might stick to salt pellets. Thanks once again.Appreciate it.

  8. Meera

    My son and his team of 3 have finally decided to do the ocean acidification experiment on shells. They want to test the acidification in ocean water by carbonating it and thus making it acidic. They would like to know –

    1. Would 16 oz of water be enough?
    2. Should they have a separate jar each for each type of shell they collect?
    3. How long should they leave the shells in the jars? One month? If yes, should they weigh them every week or only at the end of the month/experiment?
    4. Can they use different variations of acidic water with different PH like adding soap solution to a separate jar, vinegar in the other etc? Or is it better to stick to just the carbonated water with a specific PH?
    5. Should they use distilled water in the jar meant for comparison?
    6. Can they consider the temperature of water for variation? For example placing one jar in the refrigerator or sun?
    7. Can they use water plants along with shells? If yes, should they have a separate jar for plants or is it OK to have the plants along with the shells in each jar?
    8. Is it OK to experiment using the carbonated water? Or is it better to stick to adding vinegar to make it acidic?

    Highly appreciate your inputs.

    • Dr. Maille Lyons

      OK – part of their project will be figuring out these things for themselves 🙂

      Overall, figure out how they will measure pH and how precise the measurement is. I am not sure the carbonation will change the pH by a measureable amount unless you have access to sophisticated equipment. That’s why I recommend vinegar – a little bit will have a large effect on pH.

      The best design would be one shell per container; at least three shell/container for each condition they are testing. Ocean water without vinegar is the best control because the shell will not dissolve on the time scale the experiment will be conducted. The amount of time it takes to see a difference will depend on many factors… pH, type of shell, size of shell, volume of water, etc. Plan for at least 1 month; check the shells once per week.

      Temperature could also be evaluated but remember that they need 3 containers each with one shell per treatment; so looking at both pH and temperature will double the number of containers and shells (for two temps – room temp and refrigerated; putting some in sun will add too many other variables). No, I wouldn’t do plants and shells in same containers it will introduce too many issues and then you’d need salt water plants which are more expensive than fresh water plants.

      Good Luck

  9. Meera

    Thanks a lot once again for all your valuable inputs. Since it is their first time doing the science project, they are a bit lost about how to get started! They now understood that Vinegar is the best option and have decided to stick to it and with just the shells only. Thanks a lot for giving them such valuable guidance to get a head start. I have just made a minimal donation in support of your great cause and would love to continue doing more in future too.

  10. Meera

    Hello, I’m glad the boys are getting to a good start, thanks to all your guidance. They are using 16 jars, with 4 different types of shells. The sea water is their control and measures a PH of 7.75. It was pretty clear and they filtered it too and picked up shells from the beach. They added vinegar in proportions of 5ml, 10 ml and 40 ml in jars containing one pint of sea water each and arrived at PH of 5.28, 3.25 and 2.57 respectively. They want to know
    1. Should they set the PH of the jars to rounded numbers or is it OK to just leave at these numbers.
    2. Should they really consider the amount of vinegar added as a variable or no, as it is secondary here.
    3. What method is best to dry the shells before weighing them each week? Leave them in the sun to dry? Blow dry them? or air dry them ? or Wipe with paper towel? Would heat and other methods affect the weight of the shells?
    4. Is it OK to mark the weight of the shells on the inside of them with a fine marker? Would the small amount of marker ink affect the shells in any way?
    5. Is it better to take pictures of all the shells individually each week to record the changes along with the weight?

    • Dr. Maille Lyons

      They do not need rounded numbers for pH, but remember pH is a log scale so when they graph pH vs. any of their measurements they will need to have the correct axis

      The amount of vinegar causes the pH change, so it is the independent variable as far as it is used to change pH.

      They should decide on how to dry the shells, or could measure them wet.  Whatever they decide, as long as they are consistent will be fine.

      Unless you have access to incredibly sensitive equipment, your scale should not be able to distinguish the difference with and without ink on the shell, so they can write on the shells.  However, check to see if the marker will survive the soaking (it may dissolve off especially in the lowest pH)

      Yes, I recommend photos… it will make for a better display and can be used after the fact to measure other metrics (length, % loss, etc.). 

      MAKE SURE THERE ARE 3 SHELLS IN EACH JAR – otherwise, there is no replication at the appropriate level and the design is flawed.  Make sure the 3 shells are as similar as possible (e.g. total weight is similar) OR find 12 shells that are as similar as possible and RANDOMLY distribute them between the jars.

      You can photo the group of three for each jar (don’t need 3 photos per jar).  Put the same shells in the photo in the same way each time they weigh them.  You’ll have a visual for change over time.

  11. Meera

    Can you also suggest what could be the dependent and independent variables in this case? Some dependent variables that they can think of is the time,the PH, and the wieght of the shells. Can the amount of vinegar be a dependent variable too? And can the appearance of the shells be an independant variable?

    • Dr. Maille Lyons

      There are only two independent variables:

      pH (as determined by the volume of vinegar added)
      shell type (assuming… oyster, clam, mussel, scallop, crab, etc.???)

      The primary dependent variable appears to be weight. 

      With photos you will also be able to assess changes in length and % loss of shell.

      Constants are the temperature, time, volume, type of shell (within the same series of pH jars), and pH (within the same series of same type shell jars). 

      Also each time the shells are take out to be weighed RECORD THE PH of the jar…. spoiler alert… it will change as the shells dissolve.

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