Analysis

h) The data that our group collected, along with the class data, as a whole, was quite varied.  There weren’t any definite patterns of trends in a majority of the data.  Still, the reason for this variation is most likely due to human error.  Throughout the duration of the lab, there were many things that could have accounted for the differing rates of dissolved oxygen and productivity.  Some examples of the possible errors that could have occurred were that there were air bubbles within the samples, and also while pouring the sample we could have added extra oxygen ultimately causing variation in results.  Also while performing the productivity part of the lab, our samples may all not have had the same amount of light which adds an extra variable to the experiment and affects the outcomes.  Albeit, we were still able to get a general understanding of the impacts of dissolved oxygen and productivity in an aquatic ecosystem.  Specifically, in the first part of the experiment, we were able test two different samples each with different temperatures.  As we used the Winkler method we were able to understand that as the temperature of the water increases, the concentration of the dissolved oxygen decreases.  This was tested by titrating both a 20 degree sample and a 0 degree sample of the same pond water. This then explains that no matter what body of water you are testing, there will be higher dissolved oxygen content within that body of water in the winter than in the summer.  The rate of dissolved oxygen can be affected by many other factors such as wind where oxygen gets mixed into the water as air blows, turbulence in which oxygen is mixed in at the water flow but is agitated by various obstructions such as rocks, fallen trees, and waterfalls, and trophic state which is when the amount of nutrients like calcium and nitrates effects the sustainability of animals in that aquatic ecosystem.  One other factor we tested in this lab was productivity and the effects of photosynthesis.  To do this we manipulated seven different samples to each absorb a different amount of light.  By putting different amounts of screens over the bottles we tested a control bottle, a dark bottle, a light bottle, a bottle with 65% light, a bottle with 25% light, a bottle with 10% light, and a bottle with 2% light.  Our data varied slightly due to the human error, but it was apparent that as the bottle became more exposed to light, there was a higher amount of both gross and net productivity.  This also then proved that the less light, the less dissolved oxygen.  This is because when light is limited photosynthesis becomes a difficult task, and sometimes even impossible.  For example, our dark bottle had the least amount of dissolved oxygen measuring only 2.2336 mg/L, whereas our initial bottle, that was not covered at all, had a dissolved oxygen rate of 3.5598 mg/L.  Overall, this experiment allowed us to analyze how different factors affect the amount of productivity and dissolved oxygen in an ecosystem.