Stable free radical from plant litter decomposing in water.

The presence of a stable radical species in both fresh straw and that which had been submerged in aerated water for up to six months has been demonstrated using electron paramagnetic (spin) resonance (EPR or ESR) spectroscopy. A radical signal was associated also with material shown to contain straw lignin markers, which was leached from the rotting straw into surrounding water. Fresh straw treated with strong alkali to remove phenolics did not show a radical signal. The possible effect of a dissolved stable free radical is discussed in relation to the antagonistic effect of rotting straw on algal and cyanobacterial growth in water to which straw has been added as a nuisance algal control agent.