Algae Lab
The experiment we conducted in lab used three different species of algae, Macrocystis (brown), Plocamium (red) and Ulva (green). Before we conducted anything, we first measured the initial oxygen concentration in the water that was used to house each alga. This was done because in the water that we used there happened to be phytoplankton which can respire and photosynthesize. If we didn’t take them into consideration our results would end up skewed. Once that was known we took a piece of each algae that had a surface area of 39.26 cm² and placed them in individual flasks filled with the water we had previously measured. Each algae was placed into two bottles that were labeled dark and light. The bottle labeled dark was covered with aluminum
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foil and mixed indoors to simulate a night scenario. The other bottle, light, was taken outside and placed in the sun while sitting in ice water to maintain a consistent temperature. Each individual bottle was placed under its specific condition for 45 minutes to a little over an hour. Once their time was up they were brought to the front of class and their final oxygen concentration was recorded, final temperature and the final fresh weight of the algae. Once we had the initial and final concentrations of oxygen, temperature, weight and time we were able to conduct our calculations. The next step was finding the change in oxygen measured in milligrams. The way we found this was by taking the final concentration of oxygen and subtracting the initial concentration. Once that was done we multiplied it by the liters of water that was used to house the algae during the experiment. This gave us the total amount of oxygen that was produced by the algae and the phytoplankton in the water. In order to find the true amount of oxygen produced just by the algae itself we had to figure out how much the phytoplankton produced on their own. Luckily in our experiment we used controls that consisted of just the water. Once the total amount of oxygen was found in the controls we were to subtract that number from our already calculated amount of oxygen for each condition. Once that was done we had the total amount of oxygen that was produced by the seaweed itself. This number was then used in helping us calculate the amount of oxygen produced by a gram of fresh weight per hour, which is net photosynthesis. In order to calculate that we took the amount of oxygen produced by the algae and divided it by its fresh weight then took that number and divided it by the amount of time spent in the treatment. The numbers that came out negative represented the dark bottles which found out the respiration rate which is the amount of oxygen consumed by the plant. During dark respiration the plant is able to break down glucose and make ATP. In order to figure out the gross photosynthesis we took the net photosynthesis represented by the light condition and added it to the positive dark respiration value.
This was done for each algae species. The next step was solving for the surface area comparison which can be labeled at mg of oxygen produced by cm squared per hour or micro grams of oxygen produced per hour by cm squared. First we took the number that we calculated previous which represented the total amount of oxygen produced by the algae itself and divided it by the surface area of that specific algae. Once that was done we were able to take that number and divide by the time that algae spent in its condition whether it was outside or inside. To make things easier on us we then converted this number to micrograms so the numbers were quite larger. Once the surface area comparison was conducted for the dark and light for each species we would calculated the gross photosynthesis measured in micrograms of oxygen produced each hour per each centimeter squared. In order to get this number we added the dark and light surface area comparison together for each species. The last and final calculation that was done was in regards to photosynthesis vs. dark respiration. We wanted to know if the algae were producing more in one area vs. another. We did this by subtracting the dark gross photosynthetic rate from the
light.
foil and mixed indoors to simulate a night scenario. The other bottle, light, was taken outside and placed in the sun while sitting in ice water to maintain a consistent temperature. Each individual bottle was placed under its specific condition for 45 minutes to a little over an hour. Once their time was up they were brought to the front of class and their final oxygen concentration was recorded, final temperature and the final fresh weight of the algae. Once we had the initial and final concentrations of oxygen, temperature, weight and time we were able to conduct our calculations. The next step was finding the change in oxygen measured in milligrams. The way we found this was by taking the final concentration of oxygen and subtracting the initial concentration. Once that was done we multiplied it by the liters of water that was used to house the algae during the experiment. This gave us the total amount of oxygen that was produced by the algae and the phytoplankton in the water. In order to find the true amount of oxygen produced just by the algae itself we had to figure out how much the phytoplankton produced on their own. Luckily in our experiment we used controls that consisted of just the water. Once the total amount of oxygen was found in the controls we were to subtract that number from our already calculated amount of oxygen for each condition. Once that was done we had the total amount of oxygen that was produced by the seaweed itself. This number was then used in helping us calculate the amount of oxygen produced by a gram of fresh weight per hour, which is net photosynthesis. In order to calculate that we took the amount of oxygen produced by the algae and divided it by its fresh weight then took that number and divided it by the amount of time spent in the treatment. The numbers that came out negative represented the dark bottles which found out the respiration rate which is the amount of oxygen consumed by the plant. During dark respiration the plant is able to break down glucose and make ATP. In order to figure out the gross photosynthesis we took the net photosynthesis represented by the light condition and added it to the positive dark respiration value.
This was done for each algae species. The next step was solving for the surface area comparison which can be labeled at mg of oxygen produced by cm squared per hour or micro grams of oxygen produced per hour by cm squared. First we took the number that we calculated previous which represented the total amount of oxygen produced by the algae itself and divided it by the surface area of that specific algae. Once that was done we were able to take that number and divide by the time that algae spent in its condition whether it was outside or inside. To make things easier on us we then converted this number to micrograms so the numbers were quite larger. Once the surface area comparison was conducted for the dark and light for each species we would calculated the gross photosynthesis measured in micrograms of oxygen produced each hour per each centimeter squared. In order to get this number we added the dark and light surface area comparison together for each species. The last and final calculation that was done was in regards to photosynthesis vs. dark respiration. We wanted to know if the algae were producing more in one area vs. another. We did this by subtracting the dark gross photosynthetic rate from the
light.