ocean acidification on crab shells

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Re: ocean acidification on crab shells

Postby surferg1 » Sat Nov 16, 2013 11:51 am

My hypothesis was that If I put crushed Blue Crab shells in a Gulf of Mexico solution of decreased pH of 7.0 and 6.5, and control sample of 7.5pH for thirty days, then the mass of the shells will stay the same. My hypothesis was incorrect as the shell lost weight in all samples, including the control. The average loss in weight for 7.5pH sample was 4.6 grams. The average loss in weight for 7.0 pH sample was 4.7 grams. The average loss of weight for 6.5pH sample was 5.4 grams.
It's clear that my hypothesis was wrong and that the more acidic water made the crab shells loose more weight, but why? How do I explain the loss of weight in all of the samples? Can the loss of weight for the control and 7.0pH be attributed solely to organic breakdown, like detritus? Is that also why the samples smelled sulfurous and looked carbonated?
Did I somehow prove that the more acidic the water the more the shell breakdown? Or did I prove anything at all?

I still don't know any benefits to society for my experiment either.

Also,Do you know of a really simple graph maker?
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Project Question: ocean acidification effects on crabs
Project Due Date: nov 20,2013
Project Status: I am finished with my experiment and analyzing the data

Re: ocean acidification on crab shells

Postby heatherL » Sat Nov 16, 2013 12:29 pm

Hi surferg1,

It looks like you have some great results to discuss. First of all, it looks as if you do see a trend for more mass lost in lower pH water. Remember that pH is on a logarithmic scale, so small changes in pH represent large changes in hydrogen ion concentration. When you went from a neutral pH (7.0) to an acidic one (6.5), you saw the biggest difference in mass change.

SciB mentioned that, in addition to chitin, there is calcium in crab shells. It could be that the calcium is being leeched from the shells, and that this process occurs to a greater extent in more acidic water.

Ocean acidification is occurring around the world, largely because of the increase in CO2 levels in the atmosphere. Because many people rely on seafood for their livelihood, and lots of people just like to eat seafood, the effects of acidification on crabs is completely relevant to society. If small changes in pH are a problem for crabs, we could see problems with the crab fisheries.

Microsoft Excel is a fairly simple graph maker. You sometimes have to play around with the options to make the graph look the way you want, but it will make graphs very quickly within your spreadsheet.

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