The Role of Patchiness and Disturbance is the heading at the top of the sheet. The students work in pairs. Each pair has five plain white ridged plastic cups half filled with water. The students believe that each cup represents a pond and that a pond can represent a larger ecosystem. Four out of five cups float a single green frond of a single species of water-borne plant. In the final cup the four different types of waterweed are all growing together. The final cup is completely covered with greenery so that it is impossible to see any of the water. This is the control cup.
In the beginning around one fifth of the surface of the water in any given cup was covered. Several weeks into the experiment many of the cups contain only dead matter. Only the control cups have become more full of life than they were.
I ask one of the students why the plants when grown on their own don’t grow. He says that we’d assume it would be something to do with the complexity of the ecosystem involving their relationship with one another. But also it could be microbes it could be light – actually Miss it could be anything. The names of the different plants are written on the cups. Sometimes the same plant has different names. Salvinia, Fairy Fern, Ivy Leaf Duckweed, Lemna Minor, Lesser Duckweed, Duckweed and Azolla are written.
There is a layer of azolla compacted beneath the bed of the Atlantic Ocean. It is forty-nine-million years old, dating back to the Eocene era when the Atlantic was a freshwater sea. It has been proposed that large colonies of azolla bloomed on the surface of the ocean before sinking to the floor and becoming incorporated into the sediment. Azolla can consume carbon dioxide and so as the blooms sank they drew carbon dioxide down out of the atmosphere and trapped it at the bottom of the sea. It has been suggested that this process contributed to the planet’s transformation – it turned from a tropical greenhouse state into the cooler climate in which we currently live. They call it the Azolla Event. It has even been suggested that it might be possible for humans to engineer massive algal blooms to draw carbon dioxide out of the atmosphere in the near future.
The lecturer strides casually up and down the central alleyway. ‘I like this experiment because it is elegant and simple’, he tells me. ‘There is not much to see. No need to travel. And hardly any equipment at all.’ He raises his voice. ‘What have you found out?’ he asks into the atmosphere. ‘What is going on here?’ The students are all busy either examining contents of their cups or recording their findings and none of them appear to be listening.