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.

部分水生植物即便处于亚适宜条件下，仍拥有较快的代谢与生长速率，可在大型水库等静水生境中成为优势类群，进而扰动养分循环并降低环境质量。当前亟需明晰水生生态系统中入侵物种的生态影响过程，其中与有机质分解相关的研究尤为关键。本研究以巴拉那盆地波尔图普里马韦拉水库（Porto Primavera）与朱皮亚水库（Jupiá）中的沉水植物为研究对象，开展厌氧分解实验，受试物种包括本土种伊乐藻（Egeria densa Planch）与外来入侵种黑藻（Hydrilla verticillata (L.f.) Royle）。研究测定了分解过程中的有机质降解量、沥出物腐殖化程度、电导率与pH值，并采用数学模型拟合不同时间尺度下的植物分解模式。两种受试植物均呈现出一致的有机质降解与碳矿化非均一模式。碳矿化模型与实验实测数据拟合效果良好。两种植物的分解过程无显著统计学差异。两种植物的培养实验结果显示，其颗粒态有机碳（Particulate Organic Carbon, POC）矿化的半衰期较短，而溶解态有机碳（Dissolved Organic Carbon, DOC）矿化速率较低。