Establishing An Algae-Brine Shrimp Ecosystem

This video will explain how to set up a
simple micro-ecosystem to investigate food web interactions In this experiment, the Brine shrimp Artemia salina will be our herbivore. Our producer will be from the genus Tetraselmis which is also known as Platymonas a genus of green algae. Here is a list of the materials you’ll need for this experiment You’ll need a spectrophotometer,
seawater, algae, a micropipetter graduated cylinder, jars, a transfer pipette, petri
dishes and a dissecting microscope. First, we will measure the concentration of our algae. If you’re unsure about this methods please refer to the video of how to use a
spectrophotometer. Pipette 2 millimeters of seawater into your curvette to use to
blank the spectrophotometer. Next your going to determine the concentration of your algae stock, using a clean pipette tip, transfer two milliliters of your algae solution into a
clean cuvette Place the cuvette in the spectrophotometer and
record the value of the absorbance Using the worksheet provided calculate the algae concentration of your sample using the standard curve. Next label your jars. On each lid place a piece of tape and label it with the group name, the day, the time of your
class as well as the treatment that will be inside that jar. Next you’re going add the
calculated amount of seawater to each jar. You’ll use your worksheet for
calculations of how much seawater to use to dilute your algae culture. Measure out the required volume of seawater remembering to from the meniscus minister in your graduated clyinder. In this case we’ve calculated that will need forty-five milliliters of seawater and five milliliters of algae. So we first add forty-five milliliters of seawater to the jar. Now we’ll add the appropriate amount of
algae to our jar. Now in this example will need to add five milliliters, so first we swirl the
algae to mix it, then we select one milliliter using our micropipetter and a clean tip. Add that the jar and then repeat four more times Next your going to add the
Brine shrimp to each jar First collect a sample from your Brine Shrimp. You see here that there is
a mixture of swimming, moving Brine Shrimp as well as some unhatched eggs, those are they small yellow spheres You’re going to collect some of that sample, transfer to a petri dish and then look at the sample using a dissecting microscope. This is an unhatched egg, you don’t want to select these to add to your ecosystem. Instead select the Brine Shrimp you see you see here. Carefully use the pipette to select
individual Brine Shrimp to transfer to your ecosystem jar You may need to dilute the brine
shrimp culture using additional seawater so that you’re able to pick up
just one individual The focus of this experiment is to investigate trophic
interactions. Let’s look into that further There are two types of interactions between trophic levels. Lets imagine an ecosystem that made up of plants insects and birds In this ecosystem the insects eat the plants and the birds eat the insects. Now in a bottom up interaction between trophic levels as the number of plants increases so does the number of insects. And as we increase the number of insects we see a higher number of birds. And so
if we look at the number of plants as that increases the number of birds increases too. Now in a top down interaction as the number of birds increases you’ll find fewer insects. And as the number of insects increases there will be fewer plants. And so if we look at the relationship between birds and plants as
number of birds increases the number of plants also increases. In a bottom-up if there are more plants there are more insects there are more birds. But in a top-down interaction if there more birds we see fewer insects and more plants. As you plan your experiment think about what you would need to manipulate to
study bottom-up and top-down interactions using algae and Brine Shrimp micro-ecosystems.

Comments 1

  • This video can be used as a way to "flip" the laboratory exercise To Build an Ecosystem: An Introductory Lab for Environmental Science & Biology Students by Daniel Hudon and John R. Finery in
    The American Biology Teacher (2013, Vol. 75 No. 3, pp. 186-192) DOI: 10.1525/abt.2013.75.3.7.
    It can be accessed at

    The Flipped Lab Video on using the spectrophotometer gives an introduction to use of a key piece of equipment needed for this study.

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