Anaerobic decomposition of a native and an exotic submersed macrophyte in two tropical reservoirs.

Some aquatic plants have fast metabolism and growth, even at sub-optimal conditions, and become dominant in lentic environments such as large reservoirs, altering the nutrient cycle and impairing their environmental quality. There is great need in the knowledge impact processes of invasive species in aquatic environments, among the major, those related to the decomposition. This study evaluated the anaerobic decomposition of invasive submerged macrophytes Egeria densa Planch, native, and Hydrilla verticillata (L.f.) Royle, exotic in Porto Primavera and Jupiá reservoirs, Paraná basin. We evaluated the decay of organic matter, humification degree of the leached material, electrical conductivity and pH of the decomposition process. Mathematical models were utilised to describe the decomposition patterns over time. Both species showed the same heterogeneous pattern of decay of organic matter and carbon mineralisation. The models of carbon mineralisation, compared with the experimentally obtained data presented were adequate. Both species show no significant differences in the decomposition processes. Incubations of both species presented rapid t ½ for POC mineralisation and low DOC mineralisation.