Water chemistry is altered by the biological processes of phytoplankton (microscopic photosynthetic organisms). The first two activities begin with an inquiry into what some of these water chemistry changes are, and what influences these changes (type of water, exposure to light, etc.) and an opportunity for the students to design an activity based on experience gained from the first activity.
The last two activities explore the effect of greenhouse gases on heat absorption in the atmosphere and the effect of the biological processes of phytoplankton on these greenhouse gases. These two activities can be used in conjunction with the first two or as inquiry by themselves.
Teacher Preparation for
*Directions: Add liquid plant food in the amount given for hydroponic growth to
live (pond or aquarial) water. Expose solution to intense sunlight
and/or sunlamp. Water should be green, indicating an algal bloom.
Teacher Preparation for
*Directions: Add liquid plant food in the amount given for hydroponic growth to live (pond or aquarial) water. Expose solution to intense sunlight and/or sunlamp. Water should be green, indicating an algal bloom.
The process of photosynthesis reduces the availability of hydrogen for ionization therefore reducing the acidity of the solution (pH goes up). When the organisms are removed, changes in dissolved oxygen and pH will no longer be observed because they are the agents of those changes. Chemical formula:
CO2 + H2O <=>CH2O + O2
where CH2O is the organic carbon. The H2 is tied up in that molecule, no longer able to disassociate from the O2 and therefore creating the H+ ions used to determine acidity. As O2 goes up, so does the pH in this system Conversely, as pH goes down, CO2 goes down.
Chris Carillo University of Hawaii
Biological Oceanographic Processes 3rd Edition; T.R. Parsons, M. Takashi, B. Hargrave; Butterworth-Heineman, 1995.
Secret Agents of Dissolved Oxygen - Part I
BOTTLE 1 2 3 4 5 6 T PH CD DO T PH CD DO T PH CD DO T PH CD DO T PH CD DO T PH CD DO Initial Reading (teacher) Trial 1 (Your data) Trial 2 (Other groups) Trial 3 Trial 4CD = Carbon Dioxide DO = Dissolved Oxygen
Average each bottle numbers trial value.
Graph the above data using color codes for each bottles data for initial and final value
In the first activity, you tested water collected by your teacher that came from various sources. You tested this water for dissolved oxygen, pH, and temperature to determine the impact that natural processes, such as photosynthesis and respiration, had on the water chemistry.
You are to design an experiment that will determine if the time of day or the amount of time exposed to sunlight affect the amount of dissolved oxygen, CO2 and/or the pH of the water. Decide first what the overall plan is that will test only the one thing you want to be tested. Then select your materials and write up your procedure in a clear step-by step format. Have your plan approved by the teacher before proceeding any further. The teacher will let you know if you are to implement the test.