Effect of ocean acidification on copepods

[deleted-368194]

Hi,
I am starting to plan out my science fair project for the year and I am running into some problems. Realize that this is still in its infancy so I will not be providing information such as my hypothesis. I am thinking of testing the effects of ocean acidification on copepods. I have already figured out how I am going to culture the copepods, but I have some questions about the water. Firstly, how do I change the acidity of the water? If I take water out of the tap and add an acid (I live in a place with hard water) the water will just jump back to the same PH level because it is buffered. Also, what should I do to change the acidity? Should I add carbonic acid to replicate the conditions in the ocean? What kind of copepod and algae will be the best? I want an algae that won't be affected by the higher acidity.

Thanks!
MC

[SciB]

Hi MC,

Studying effect of decreasing ocean pH on a copepod is a great idea and an important area of research today as atmospheric CO2 levels continue to climb. Most people don't realize how important the oceans are to the survival of all animal species including humans. Most of the oxygen that we need to breathe comes from phytoplankton in the sea. If they die we are in BIG trouble.

I have never tried to grow copepods but some people who have salt water aquariums apparently can do this to produce food for their fish: http://www.advancedaquarist.com/2003/2/breeder
You can check that site to find out what type of copepod they used.

Changing the pH of sea water is a challenge as it contains carbonate and bicarbonate ions that act as buffers that neutralize acid to keep the pH in the 7-9 range. If you live near the ocean you can use sea water for your experiments. Buy an inexpensive pH meter to use for measurements as it is much easier and more accurate than pH paper. There's a lot of information on the web about measuring pH, but this site is specifically about salt water aquaria: http://www.advancedaquarist.com/2004/2/chemistry

Many ocean researchers use a standard 'salt water' called Instant Ocean for experiments. This is available commercially as a powder that you dissolve in distilled water: http://www.instantocean.com/

To lower the pH you could try bubbling CO2 through sea water for some length of time. This would mimic the actual conditions where atmospheric CO2 is dissolving in the ocean. I don't know how much this would lower the pH and for how long the pH would remain at the same level. You want sea water that has a constant pH at the level that you have chosen--say 6 to 6.5. What I think you should do is call the Instant Ocean company and ask to talk to tech support. They are experts in controlling and adjusting pH in sea water and they can tell you how to create an ocean at the pH you desire. They may even have special Instant Ocean formulas at different pH's for researchers.

If you have no luck with commercial sea water sources then the alternative is to search Google Scholar and PubMed for ocean pH research papers. Some researchers must have done the same thing as you are trying and will have a method for creating artificial sea water at a constant, defined pH.

Keep posting your questions as your project develops. We can help you designing experiments that are statistically meaningful and well-controlled. Your results will be meaningless if you do not include the proper controls and statistical tests. These are what make science science!

Good luck!

Sybee

[deleted-368194]

Thank you so much! Ill look over the links you sent and think about what you said and get back to you. Luckily, I already have drop ph testers because I have some aquariums. I will also be able to test the hardness, since I already have one of those too.

[SciB]

You're welcome! It's great that you already have aquariums set up. If you have a couple of extra tanks you could fill them with salt water at different pH's, add some copepods and see what happens.

Keep us posted on your progress and of course if you have any questions, that's what we are here for.

Good luck!

Sybee