Decomposition is when organisms like bacteria and fungi break down dead organic matter (remains of dead plants and animals). When the bacteria break down dead matter, gases and water are released. During decomposition, the release of water causes the organic matter to look more wilted as it loses its water content. Have you seen a fruit go mouldy before? It is usually quite squishy, isn't it? The reason for this is because some of the water has been released due to decomposition of the fruit. Also, the mouldy fruit smells bad because of the gases released by the decomposition process.
Decomposition happens faster where there is lots of oxygen. In aquatic ecosystems, like ponds, there isn't much oxygen in the water. Therefore, in water, decomposition of dead matter happens more slowly than if it were exposed to the air.
The following experiment will test the differences in decomposition due to temperature and moisture. As a control we use inert plastic.