An Unexpected Turn and Experimentation

Well, as stated in my last post, Mr. Soderblom and I had hoped that the Cyclotella species would be the diatom to survive the best, as it is the easiest to observe, but alas, not everything goes as planned. Unfortunately, all of our Cyclotella cultures turned clear after one week of allowed growth, aerated or not, meaning a majority of the cells died due to unknown causes.

Our Chaetoceros cultures, however, have taken really well. Their bottles are a darkish yellow color, even the cultures that ended up taking 5 days to ship, meaning they are thriving quite well. The aeration seems to have aided in growth rate, so we will be using this method in our experiment.

We officially began experimentation today!! To start, we expanded our best culture (the one that took 5 days to ship, surprisingly) by diluting it with more medium (in a 1:1 ratio) to allow it to grow. In the end, we had 1 liter of the expanded culture. Then, we separated the culture into 5 bottles, each getting around 200mL. 

Two of the bottles we designated as controls. The other three were contaminated with the oil. Now after having sifted through some research, I found that oil concentrations in the ocean water of the Louisiana Bay were about 160-260 ppm near the time the drill was capped off. We decided that in order to get noticeably different results for each bottle, we would have one bottle be within the range of the actual spill, and two with more exaggerated levels. In the end, the bottles held 250, 750, and 2500 ppm of crude oil (or 1, 3, and 10 drops from a pipette). I hypothesize that the 250 ppm won't cause much difference, the 750 ppm will have accelerated the growth rate, and that the 2500 ppm will precipitate, turn clear, and kill all of the plankton. The oil sat on top and looks really sludgy. (I thought it was funny the researchers who gave us the sample labeled it "sweet crude").

We took pictures of Chaetoceros yesterday. They're notably smaller than the Cyclotella at about 8 micrometers by 4 micrometers. They also aren't very neatly-shaped. (The third is from Google and apparently, they enjoy sticking together but it's hard for us to tell if ours are exhibiting that behavior). (At 4X and 40X objective respectively).

We also took pictures of the Thalassiosira and plan on using this species if we have the proper amount of time. (at 4X and 40X)

As you can see, they're small and hard to count, but we'll just have to do our best.

Signing off till next time, this is Erin Butcher.