Cooking with Foraminifera Part I

Adriane here-

Stirring a solution of tap water and Miramine for use in our experiment.

A lot of the research my lab and I do is related to understanding how the oceans worked in the past, the ocean’s response to climate perturbations, and understanding plankton evolution. Every now and then, we find the need to do a different type of research: testing a new or old method. This fall, my lab mate Serena, my advisor, Mark, and myself have developed a little experiment to see if boiling foraminifera in different solutions has any effect on their shells. Specifically, we’re interested to see if boiling affects the isotopic measurements of the shells. This has not been tested thoroughly before, which is surprising. In this post, I’ll talk about the first part of the experiment, and I’ll elaborate on the other part of this experiment in a subsequent post.

Our samples split into three different solutions. Notice how different the contents of each beaker look! This is because the sediment types we chose have very different colors.

You may be thinking ‘why on Earth would you boil foraminifera in the first place?” When we, scientists, get in sediment samples from deep sea sediment cores, sometimes the sediment is very hard or full of fine-grained sediments. These hard and/or fine-grained sediments have a tendency to not want to break down and release the foraminifera shells contained inside. To aid in breaking down tough sediments, we often turn to boiling the sediment in tap water or other solutions.

To begin the experiment, Serena and I chose four different sediment samples from different places around the world and of varying ages. We split each sample into quarters to be tested in our boiling experiment. We then chose three different solutions in which to boil our samples: tap water, Sparkleen (a mild detergent) mixed with tap water, and Miramine (an oily substance used as a emulsifier and corrosion inhibitor, but also good for breaking down rocks) mixed with tap water. Each quarter of the samples we chose were placed in these solutions in a beaker, which were then placed on a hot plate. The samples were brought to a slow boil and left for an hour.

Eight of our samples boiling on the hot plate. We place a piece of venting over the hot plate and beakers to keep the beakers from falling off the plates.

The fourth quarter from each sample was used as a control for which to compare everything else against (from here out I’ll call these the ‘control quarters’). The control quarters were simply rinsed over a screen using tap water. Doing this removes the small sediment particles, but holds back the foraminifera shells.

This is what one of samples that was boiled in Miramine looked like under the microscope! It’s hard to see here, but the rounded bits of sediment are actually foraminifera. The large chunk to the right is a piece of sediment.

After the samples were finished boiling, we then washed each one over a screen in our sink, just like we did with the control quarters. These were placed in an oven overnight at a very low temperature to dry. Once the samples were dried, Serena and I picked out three different species of foraminifera from each sample: a species that lived at the very top of the water column, a species that lived deeper in the water column, and a benthic foraminifera species that lived on the seafloor.

The last step was to put the species we had picked from each sample into a vial for further analysis. The next step will be to put these vials in our mass spectrometer, a device used to measure the isotopic signature from each sample. We’ll then compare the measurements from the boiled samples to the control quarter samples to determine if the isotopic measurements from foraminifera shells are affected by boiling!

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