Team+7

Team 7 Madison Palmer, Shon Koren, Robbie Papapietro, Sam Scott  Mrs. McLoughlin   May 7, 2012 __Temperature’s Effect on Dissolved Oxygen Concentration in Water__
 * Purpose:** The purpose of this lab is to investigate the effect of temperature on the concentration dissolved oxygen and on the ability of water to hold dissolved oxygen.


 * Hypothesis:** If temperature has an effect on dissolved oxygen concentration in water then water with a higher temperature will have a higher concentration of dissolved oxygen and water of lower temperature will have a lower concentration of dissolved oxygen.


 * Materials:**
 * 3 BOD bottles
 * Manganous sulfate
 * Starch indicator
 * Sulfamic acid
 * Measuring spoon
 * Alkaline potassium iodide azide
 * Sodium thiosulfate
 * Titration syringe
 * 20mL sampling vial
 * Graduated cylinder


 * Methods:**

First, three containers of water were left to equilibrate at different temperatures. The temperatures were at 10°C, 20°C, and 32°C. Then, three BOD bottles were labeled corresponding to the different temperatures of water. Then, each BOD bottle was filled with water of the matching temperature by submerging it in the sample, allowing it to fill, then capping it while it was still submerged. This eliminates any air that might get trapped in the bottle. Also it is important to avoid introducing any turbulence. Improper filling will mix air into the sample and increase the dissolved oxygen level. The following procedure (The Winkler Method) was used in determining the amount of dissolved oxygen. First, the BOD bottle was uncapped. Then, eight drops of manganous sulfate solution was added to the bottle. Then, 8 drops of alkaline potassium iodide azide was added to the bottle. The bottle was then capped and was mixed. Time was then allowed for the precipitate to settle to the shoulder of the bottle before proceeding. Then using a 1g spoon, 1 gram of sulfamic acid powder was added to the bottle. The bottle was then capped and was mixed until reagent and precipitate dissolved. Next 20mL of the contents of the BOD bottle were measured in a graduated cylinder and poured into the titration sampling vial. Next a titration syringe was filled to the top of its scale (1.0mL) with sodium thiosulfate. Then, one drop of sodium thiosulfate was added at a time to the sample, while swirling in between each additional drop until the sample became a faint yellow color. Then the titration syringe and cap were removed. Next, eight drops of starch indicator solution were added and was swirled. Then, the titration was continued with the sodium thiosulfate already in the syringe. One drop was added at a time while swirling the sample after each additional drop, until the blue color disappeared. The syringe may be needed to be refilled. Then the total amount of sodium thiosulfate that was used was calculated. This procedure was repeated for each BOD bottle of the different temperatures of water. The independent variable is the concentration of dissolved oxygen. The dependent variable is temperature. The amount of each sample were kept constant


 * Data and Observations:**


 * Table 1: Temperature and Dissolved Oxygen**


 * **Temperature °C** ||  **Dissolved oxygen (ppm)**  ||  **% Saturation**  ||
 * 10 ||  9.7  ||  87.5  ||
 * 20 ||  10  ||  110  ||
 * 32 ||  7.6  ||  100  ||


 * Graph: ^the graph cant be copied onto this for some reason**

The results showed that at 10°C there was 9.7 ppm of dissolved oxygen, at 20° there was 10ppm of dissolved oxygen and at 32°C there was 7.6ppm of dissolved oxygen. This indicates that water holds the most dissolved oxygen at an optimal temperature of 20°c. However in this lab the temperatures of the water may not have been kept constant while performing the exeriment. Also there may have been human errors in performing the titrations or calculating the dissolved oxygen level. Percent Saturation was also calculated beacause water is rarely saturated with oxygen, therefore usually the amount of dissolved oxygen in a water sample is only part of what the water could hold.
 * Analysis:**

Since the amount of dissolved oxygen was highest at a temperature of 20°C, then results indicate that temperature has an effect on the concentration of dissolved oxygen in water. The results do not support our hypothesis.
 * Conclusion:**

Intensity of Light's Effect on Oxygen Production in Chlorella The purpose of this lab is to model and understand the primary productivity of a pond ecosystem by measuring the amount of oxygen production by the photosynthetic protist //Chlorella// under various light intensities.
 * Purpose:**


 * Hypothesis**: If light intensity affects the amount of oxygen produced in a sample of //Chlorella//, then a culture exposed to the most light will produce the most oxygen and have the highest gross productivity and the culture exposed to the least light will produce the least amount of oxygen and have the least amount of gross productivity.


 * Materials:**
 * 7 BOD bottles
 * //Chlorella// culture
 * manganous sulfate
 * Starch indicator
 * Sulfamic acid
 * Measuring spoon
 * Alkaline potassium iodide azide
 * Sodium thiosulfate
 * Titration syringe
 * 20mL sampling vial
 * Graduated cylinder
 * 17 fiberglass screens
 * square of aluminum foil
 * tape

On the first day a BOD bottle was filled with water from the //Chlorella// culture by submerging it in the sample, allowing it to fill, then capping it while it was still submerged. This eliminates any air that might get trapped in the bottle. Also it is important to avoid introducing any turbulence. Improper filling will mix air into the sample and increase the dissolved oxygen level. Next, the amount of dissolved oxygen was determined by using the Winkler Method Protocol as follows. First, the BOD bottle was uncapped. Then, eight drops of manganous sulfate solution was added to the bottle. Then, 8 drops of alkaline potassium iodide azide was added to the bottle. The bottle was then capped and was mixed. Time was then allowed for the precipitate to settle to the shoulder of the bottle before proceeding. Then using a 1g spoon, 1 gram of sulfamic acid powder was added to the bottle. The bottle was then capped and was mixed until reagent and precipitate dissolved. Next 20mL of the contents of the BOD bottle were measured in a graduated cylinder and poured into the titration sampling vial. Next a titration syringe was filled to the top of its scale (1.0mL) with sodium thiosulfate. Then, one drop of sodium thiosulfate was added at a time to the sample, while swirling in between each additional drop until the sample became a faint yellow color. Then the titration syringe and cap were removed. Next, eight drops of starch indicator solution were added and was swirled. Then, the titration was continued with the sodium thiosulfate already in the syringe. One drop was added at a time while swirling the sample after each additional drop, until the blue color disappeared. The syringe may be needed to be refilled. Then the total amount of sodium thiosulfate that was used was calculated.
 * Method:**

Next, six BOD bottles were filled with the //Chlorella// culture following the same method. One bottle was wrapped in aluminum foil, another was left untouched. Then another bottle was wrapped with one screen, a second wrapped with 3, another wrapped with five and the last one wrapped in eight screens. Each were secured with tape. Then, each botttle was layed on their sides under a fluorescent light, seam side down and were left over night. On the second day the amount of dissolved oxygen was determined for each of the bottles following the Winkler Method Protocal explained above. Results were recorded. The dependent variable was the amount of dissolved oxygen produced and the independent variable was the light intensity. The control was the 100%light and dark bottles. The amount of samples were kept constant.

Figure 2.1 - Net and Gross Productivity Calculations from Dissolved Oxygen Concentrations in Algal Cultures Screens ||= 6.6 ||= -6.4 ||= 1.8 || Screens ||= 6.0 ||= -7.0 ||= 1.2 || Screens ||= 5.9 ||= -7.1 ||= 1.1 || Respiration = 8.2 ppm
 * Data:**
 * = Bottle ||= Dissolved Oxygen (in ppm) ||= Net Productivity ||= Gross Productivity ||
 * = Baseline (initial) ||= 13.0 ||= -- ||= -- ||
 * = Dark ||= 4.8 ||= -- ||= -- ||
 * = Light (0 screens) ||= 17.5 ||= 4.5 ||= 12.7 ||
 * = 1 Screen ||= 17.8 ||= 4.8 ||= 13.0 ||
 * = 3
 * = 5
 * = 8

Overall the results were conclusive and accepted the hypothesis. As visible from the table, dissolved oxygen decreased (generally) as more light was blocked. At 0 screens, dissolved oxygen (DO) was 17.5 ppm and second highest to when only one sheet was covering the sample. From then on, the more sheets added to the bottle samples the less DO concentration there was. Unfortunately, however, the dark sample had a level of dissolved oxygen. Since it was covered by a sheet of aluminum and no light may have penetrated that, the oxygen must have been created before the experiment started since no light was available to carry out photosynthesis. As visible from the table, gross productivity decreases substantially between 0 or 1 screens to 8 screens as expected. Since more light is blocked with 8 screens than with none or one, it is expected that less oxygen is created due to less photosynthesis occurring. It is unclear as to why the sample with 0 screens had less dissolved oxygen than the sample with one but it is possible that there were mistakes in the original calculations. However even with the outlier it is possible to say the general trend fits the hypothesis.
 * Analysis:**

Since the dissolved oxygen concentration and gross productivity values generally decrease as more light is blocked, then it is likely that a higher intensity of light will produce a higher dissolved oxygen concentration and gross productivity value since more photosynthesis is occurring.
 * Conclusion:**