Wednesday, November 26, 2008
At the beginning of the semester Dr. Baines gave us an exam in which one of the essay questions required quite a bit of explanation, but it was interesting so I remember it. She asked us to, "discuss how light, temperature and oxygen levels change with depth and season in aquatic environments and describe any interactions among these factors." So I wrote the following: "During the summer, thermocline occurs which may be described as a rapid decrease in the temperature of woater at a particular depth. during Fall turnover the ater on the top is heated, (by solar radiation), so it becomes more dense thn the water below it and sinks to replace the water at the bottom. In this way htere is an exchange of nutrients within the movement of the water. Furthermore, during the winter months decomposing organisms contribute to a decreased amount of oxygen gas diffusion due to the fact that they needconsume oxygen as they perform respiration. At increased depths there is less penentation of light and so the rate of photosynthesis is decreased. In general, at higher temperatures the rate of oxygen gas diffusion into water decreases (the two elements are inversely proportional). It made sense to me this way at the time I took the exam, but then Dr. Baines returned our exams and saw that she wrote in a comment. What she wrote was that in the portion where I said that, "...during the Fall turnover the water on the top is heated," she commented that I should have said the water is cooled instead. That confuses me because then a good chunk of my response doesn't make sense. So I don't understand why she gave me full credit for my answer, but I'm not going to complain. I haven't taken the time to go back and ask her about it or reread the section of the notes that covers aquatic environments so it's still not exactly clear to me. I just need to go visit her and ask for further clarification on the matter.