In a lab experiment, a student wants to test the amount of dissolved oxygen produced by algae. Dissolved oxygen refers to microscopic bubbles of gaseous oxygen (O2) that are mixed in water. The student’s experimental design is described below: Flask A: Contains photosynthetic green algae and 1 hermit crab
Flask B: Contains photosynthetic green algae and 0 hermit crabs

Both flasks are placed under a light bank. The lights are set to cycle between 12 hours of dark and 12 hours of light. The dissolved oxygen concentrations in both flasks are recorded daily. A diagram of the experimental set-up is shown below:

Which flask will have a higher concentration of dissolved oxygen after one week?