L1.61 - Algal balls, only - Southern Biological

Immobilising algae in alginate balls provides a relatively new experimental context for investigating photosynthesis. The balls are fun to make, easy to handle and if made the same size constitute a fixed ‘unit’ of photosynthesis for comparing across different values of an independent variable. Instructions for SAPS are provided, with ideas for experiments, and ordering details for a kit from their partner in developing the protocol, NCBE at the University of Reading. The importance of phytoplankton algae as the base of marine food chains is easy to introduce in the context of this work.

In this practical, students use a potometer to measure the rate of transpiration

Using immobilised algae, students investigate photosynthesis. They can start the activity by preparing immobilised algae (in alginate jelly balls), by dripping an alginate solution, containing the algae, into calcium chloride solution. This is a quick method for generating consistent sized beads in a short time. For the investigation, the beads are placed in indicator solution and positioned at various distances from a light source. Students plan how to measure the quantity of algae used, where to position the samples and how to record their data. The samples are allowed to stand for several hours, after which the effect of changes in carbon dioxide concentration can be observed. Changes in the indicator may be measured using colorimetry, comparison to colour charts or standards or by measuring changes in pH using a pH meter.

Investigating Photosynthesis | Ph | Photosynthesis

The algae are 'immobilised' in sodium alginate, and then used for the experiment. 'Algal balls' - Photosynthesis using algae wrapped in jelly balls.