Hypotheses

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Hypothesis 1: The bacteria will survive longer than the algae in the DOC consumption experiment.

Justification: Since we are incubating the bottles and cutting off their light source, the algae will only be able to live off the DOC they have stored, whereas the bacteria do not need light and can live off the DOC available until they consume all of it.

Hypothesis 2: The forested mesocosm samples will experience a greater loss in DOC than the sunny mesocosm.

Justification: Since the algae is likely to die off in the sunny mesocosm samples, I predict that the forested mesocosm samples will experience the greatest loss in DOC. The forested mesocosm after the leaves fall would have the most available DOC to feed the bacteria, but my hypothesis is just from our two samples.

Hypothesis 3: There will be more DOC remaining in the sunny mesocosm samples after our 28 day experiment than in the forested mesocosm.

Justification: I’m going to guess that there may be DOC remaining after we have tested on the last day due to the death of the algae, because they will stop consuming the DOC and release the carbon they had stored. The data from previous years suggests that the sunny mesocosm starts out with more DOC as well.

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2 responses to “Hypotheses”

  1. mckennast says :

    I like the image you put in there. I wish I knew how to do something like that. I agree that the bacteria will be able to survive without the sunlight. I wonder for how long though? Does their rate of consumption lessen over time as a result of bacteria death? Do these specific types of bacteria rely on sunlight at all? Most organisms in my experience do rely on sunlight to an extent. Do we know what kinds of bacteria we are dealing with? I think that this could give us some insight into their respective rates of metabolism and maybe help us explain why they prefer a certain kind of DOC.
    I agree that the forested mesocosms will see a greater loss than the sunny mesocosm as well. However, I had a difficult time explaining why the forested post leaf fall would experience the greatest loss of DOC. Why would the bacteria prefer these fresh deposits of carbon rather than already decaying matter? I’m still not sure the answer to this.
    In the past the sunny mesocosm does start with a greater amount of DOC so it would make sense that it would end with the greatest amount as well. I don’t think there are as much bacteria inhabiting this mesocosm that could aid in DOC consumption.

  2. carbonconnections says :

    I think we have a little confusion here:

    Take a step back and think about what we are testing. We are not testing how long the algae will live relative to the bacteria. Since we are removing light, we can expect that the algae will die.

    Algae do NOT get there carbon from DOC!!! They are autotrophs! And where do autotrophs get their carbon from?

    Siobhan – the rate would also lessen over time as all the “good” food gets consumed (hint for thinking about fresh vs decaying leaves). It would be interesting to study the bacterial populations, but it would take time and money that we do not have for the project unfortunately.

    What about the River Samples?????

    Make sure you hypothesize about the questions our methods can answer! We are measuring the carbon consumed in four different samples. Those are the comparisons you should be hypothesizing about.

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