Science Buddies: "Ask an Expert"

Hello!

For my research project, I want to conduct an experiment that involves ocean acidification. Specifically, I was looking into how ocean pH affects the calcification rate of phytoplankton. I want to use phytoplankton because if increased levels of anthropogenic CO2 disrupts their growth, it would set off a domino effect in the ocean food web since they're the primary producer. However, the problems I have with my experiment is I am not sure how to calculate their calcification rate or how to grow phytoplankton. (I want to see how different levels of pH affect the calcification rates of phytoplankton). I got my idea from http://www.epoca-project.eu/index.php/r ... -2010.html ,as they measured the calcification rates of phytoplankton in their research. But this is difficult for me to understand as I'm unfamiliar with most of the scientific terms and methods used, so is there anyway you could explain to me in simpler terms how to do it? Or would this be impossible without professional help from a research or university?

(I already looked at the ocean acidification experiment that science buddies recommended, but I want to do something more challenging than measuring shells.)

Thank you so much for your time and consideration in helping me develop my research project.

Hi Victoria,

Your choice of subject is excellent and will make a great science project. There have been studies of the effects of ocean acidification on growth rate of phytoplankton but I don’t know of any that measured calcification in those species that have calcium carbonate shells. I did find one published scientific paper about calcification of a phytoplankton: http://rstb.royalsocietypublishing.org/ ... 7/20130049

I tried opening the pdf file from your link but it would not open. Maybe you could attach the file to another post if it's not too large.

There are numerous species of phytoplankton but since you want to measure calcification you need to get one that uses calcium to make a ‘skeleton’. A good example of this type are the coccolithophores which are unicellular algae that have calcium carbonate plates: http://en.wikipedia.org/wiki/Coccolithophore
The most abundant species is Emiliania huxleyi http://en.wikipedia.org/wiki/Emiliania_huxleyi
http://www.soes.soton.ac.uk/staff/tt/ It is also the fastest growing in lab cultures.

I think these coccolithophores are remarkably beautiful critters under the microscope and well worth studying but the question is where can YOU get them. Carolina Biologicals is my usual supplier for all types of organisms and they do have marine algae for sale as well as the seawater medium to grow them. They don’t say which species are present in their algae kit, however, so call them and find out: http://www.carolina.com/catalog/search- ... SearchForm

Also, I checked the Methods section of the paper I cited above and found that the authors obtained their culture of E. huxleyi from the Provasoli-Guillard National Center for Marine Algae - https://ncma.bigelow.org/ I went to their website and searched for Emiliania huxleyi and they do sell it, but one culture costs $175! They have an educational services tab and said to contact them if you want to partner with them for educational purposes. Maybe if you or your teacher call them and tell them how much you want to do this research and that if you only had some E huxleyi you could do a great study they might donate a culture to your school.

If you live near the ocean you could get a plankton net and gather phytoplankton yourself from sea water. That would be a really cool way to do the experiments but I don’t know how you would isolate E huxleyi from the mix of phytoplankton species.

The only other possibility would be to check around with marine biology departments at universities and try to find a lab that works with E huxleyi and is willing to send you a culture of the algae. If you could find a lab to work in and a mentor to guide you that would make it much easier for you to do experiments.

I have given you a lot of information and I hope some of it is helpful. Please post back and we will try to help you do this study.

Good luck!

Sybee

Hello again!

Thank you so much for the idea! I am going to test how ocean acidification affects the growth rate of E. huxleyi.

https://www.usc.edu/CSSF/History/2009/P ... /S1717.pdf was where I initially got the idea from after reading your reply about E. huxleyi! The difference in mine is that I am changing the pH of the water instead of changing the CO2 concentration of the jar the E. huxleyi. I have a few unanswered questions regarding my overall project though. How would I count the number of cells for E. huxleyi? I know I would look under a microscope, but how? Also, this student said that to measure the calcification rate they filtered and dried the samples to calculate the total mass. I told my teacher this, but he said he's not sure if it would work. I also don't know how this would work (E. huxleyi is in fact a microorganism, isn't it??) Also, how does the whole "strain" of E. huxleyi work? If I were able to obtain a strain, how do I separate it into the different glass jars? These are all the problems/questions I have as of now...

Although my project idea was approved, however, there was a major problem to my proposal: how we are going to attain E. huxleyi. I haven't tried contacting that website on the educational purposes tab that you recommended to met yet, but I will do that soon. In the meantime, are there any other organisms I can test that are similar to E. huxleyi? Like, maybe a type of seaweed or algae? I'm not sure.

My teacher said that we will narrow everything down eventually as time goes on, but he likes my initial idea and how it relates to OA. I just don't know if what I want to do will work out or not.

Also, thank you again so much for your help!

Hi Victoria,

I think you have some really great ideas for your project. You mentioned possibly using algae or seaweed, and I think this might be a great way to conduct the same experiment but on an organism that is easier to maintain. I just did a little bit of research and found some interesting results on ocean acidification effects on algae. It seems that some algae may grow better in acidic environments, and others may become calcified. I think you should look into it more for yourself and see if you like the idea of using algae. Here is a link to a review with extensive information on how they looked at algae in acidic ocean environments:

https://www.google.com/url?sa=t&rct=j&q ... 0786,d.eXY

(if the link doesn't work you can just google the title: Contrasting effects of ocean acidification on tropical fleshy and calcareous algae)

Also, here is a good link for growing your own algae: http://www.education.com/science-fair/a ... ing-algae/

Hope that helped, Keep posting with your ideas and questions!

Hello again!

Thank you for your post about the algae! I was thinking about working with species other than Ehux, but now that getting the strain isn't a problem, I will definitely be using Ehux in my experiments!

Now, I have another problem. I don't know if my responding variable is something that can be measures. Okay, so I was planning to to have three separate jars filled with different pH levels (manipulated variable). I wanted to measure the calcification rate of the Ehux, but I don't know if I can do that without high tech lab gear or something. So then I was thinking about counting the amount of cells the Ehux produces in however many weeks my experiment will be. How would I do this? If I want to count the amount of cells under a microscope, how would I if it's not in a certain place within the jars? Would I have to filter it out or something?

https://www.usc.edu/CSSF/History/2009/P ... /S1717.pdf I posted this earlier, but I wanted to bring it up here again. So this student said that he/she measured the calcification rate by filtering and drying the samples to calculate the total dry mass. How would I do this/ How would this work? (This is also where I got my initial idea from counting the amount of cells Ehux produces, but, again, I'm not sure how he/she went about doing this.)

I have no idea what my responding variable should be and how it would work!

Please help. Thank you!

Hi Victoria,

You have a problem common to most science experiments—what to measure and how to do it accurately. In your case you don’t have the fancy equipment, so as you suggest, one thing you can do is to count the number of Ehux cells at the beginning and end of your experiment to determine the effect of pH on growth. To do this accurately requires a special microscope slide called a hemocytometer. This glass device has very fine lines ruled on it to form a number of tiny squares that are visible through the eyepiece of the microscope. You place a small drop (10-15 microliters) of your Ehux culture on the slide and count the number of cells in the boxes. The resulting number can be used to calculate the number of cells per milliliter of culture.

You are correct that you need to have a uniform suspension of the cells to get an accurate count and this is usually done by shaking, but you will have to check on Ehux cultures in the scientific literature to make sure the plankton are suspended in the liquid and do not stick to the container.

The best way to learn how to use a hemocytometer is to have someone show you how in the lab. There are also many tutorials on youtube that show how to use the hemocytometer and how to do the calculations. This one is by the LifeTechnologies Company, but there are many others: http://www.youtube.com/watch?v=WWS9sZbGj6A

Your other dependent variable could be the degree of calcification because that is really what you are interested in. From what I have read about Ehux, it produces a complete calcium ‘skeleton’ only when the ocean conditions are right. If there’s not enough calcium available then the calcification may only be partial. The acidity of the water would affect calcium availability so should also affect the rate and amount of calcification. While I have never worked with plankton, I would think you could check the formation of the skeleton under the microscope and observe the effect of pH directly. You might even be able to count the numbers of cells with complete skeletons vs the number with incomplete. You’ll have to do some reading on this to find out.

What you said about the other person measuring the dry mass of the cells in the culture would be one way to see the calcification effect, but I think cell counts and microscopic observation, especially if you can attach a camera to the microscope and take photos, would be all the dependent variables you need to test your hypothesis.

I think you have a great project here and look forward to hearing how it comes out. If you need more help with the details, let us know.

Good luck!

Sybee