Lesson Plan: Estimating the biomass of algae in water

1. Estimating the biomass of algae in water
1. Concept:  
1. Become familiar with Beer’s Law (optical density is directly proportional to dissolved/suspended materials).  The basis of using a spectrophotometer.
2. Become familiar with pros and cons of analytical methods that perform similar tasks.
3. 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.  
2. Materials
1. 3 liters of algae
2. Screen
3. Secchi Stick
4. Weight Boats, Aluminum
3. Methods
1. Optically estimate biomass
1. Dilute solutions of spirulina
2. Estimate biomass using secchi disk
3. Estimate biomass using spectrophotometer
2. Filter, Dry, weigh
3. Plot on paper
4. Plot on computer
1. Determine slope
4. Level-2
1. Dilute spirulina into multiple containers volumetrically

1. Determine SDD and all other possible biomass estimates
2. Filter out each one and create plots

We made a video that describes this dilution with the Secchi Disk.