Ali Freibott and Belli Valencia of the Landry lab are starting their dilution experiments for Cycle 2.

Here’s Ali explaining what she studies, in her words:

What are you researching:

I research plankton food web interactions, or in other words, what plankton are eating what other plankton and how fast it’s happening. I specifically study plankton that are smaller than 200 micrometers, which is 0.2 mm. You definitely can’t see anything I study without a microscope, unless there are a ton of them blooming, in which case they turn the water a different color (sometimes brown or red). Some plankton that I study behave like plants, creating their own energy using photosynthesis, and some act like animals that eat the plant-like plankton. One tiny cell of these microplankton can grow and duplicate itself in one day, so they can eat, grow, and die really quickly. They also respond very rapidly to changes in ocean conditions.

How I study it:

We use many methods to study these tiny plankton and what they are doing. We use microscopy, pigment analysis, and DNA analysis to determine what kinds of plankton are in different areas of the ocean and how many there are. We also run special experiments, called dilution experiments, in which we add filtered seawater with no plankton to normal seawater that has plankton in order to “dilute” the concentration of plankton in the samples. After diluting multiple bottles of seawater at different concentrations and incubating these diluted samples in seawater for 24 hours, we measure how many plankton are still in each bottle and use that information to calculate rates of growth and mortality for the different plankton. In these pictures, Belli and I are filtering seawater through a very small filter to remove all plankton from the water to use in our dilution experiments.


Ali, Belli, and Mariana fill bottles from the CTD rosette with water for their dilution experiments. The bottles are first filled with filtered water (0.2 micron filters) from each depth, and then differing amounts of unfiltered seawater.


Ali’s pretty tiny bottles that will go into the incubators to let the organisms grow for 24 hours.


Ali teaches Belli all the tricks of running the normal dilution and the size-fractioned dilution.