Dry weight and chemical changes during decomposition of tropical macrophytes in lobo reservoir — São Paulo,Brazil

During decomposition, petioles and leaf blades of Nymphoides indica (L.) O. Kuntze and stems and leaves of Polygonum ferrugineum Wedd. from the Lobo Reservoir, Sao Paulo, Brazil, showed an initial phase (first seven days) of loss of dry weight, soluble carbohydrates, lipids, polyphenols, phosphorus, potassium and ash content. In both species, the decomposition of leaves and leaf blades was faster than that of stems and petioles. At the end of the experiment (after 149 days) leaf blades of N. indica had lost 98% of the initial dry weight. Except for nitrogen and ash, which increased, all the other components showed two distinct phases during the process with intensive loss during the initial phase and a gradual and reduced loss during the longer second phase.The nutritional value of the detritus and the consequence of nutrient re-cycling in the metabolism of Lobo Reservoir are discussed.