Lesson Plan: Estimating the biomass of algae in water
- Estimating the biomass of algae in water
- Concept:
- Become familiar with Beer’s Law (optical density is directly proportional to dissolved/suspended materials). The basis of using a spectrophotometer.
- Become familiar with pros and cons of analytical methods that perform similar tasks.
- It is somewhat difficult to determine the ‘mass’ of algae in water, because the cells are often very small and difficult to filter. Spirulina is a algae like cyanobacteria that is large enough to be filtered with a simple screen. Its larger size makes it a great candidate for experiments as separation is fast and easy.
- Materials
- 3 liters of algae
- Screen
- Secchi Stick
- Weight Boats, Aluminum
- Methods
- Optically estimate biomass
- Dilute solutions of spirulina
- Estimate biomass using secchi disk
- Estimate biomass using spectrophotometer
- Filter, Dry, weigh
- Plot on paper
- Plot on computer
- Determine slope
- Level-2
- Dilute spirulina into multiple containers volumetrically
bottle |
mL Algae Culture |
mL culture media (clear) |
1 |
50 |
0 |
2 |
45 |
5 |
3 |
40 |
10 |
4 |
35 |
15 |
5 |
30 |
20 |
6 |
25 |
25 |
7 |
20 |
30 |
8 |
15 |
35 |
- Determine SDD and all other possible biomass estimates
- Filter out each one and create plots
We made a video that describes this dilution with the Secchi Disk.