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.

部分水生植物即便在亚适宜条件下仍具备较快的代谢与生长速率，可在大型水库等静水生态系统（lentic environments）中成为优势物种，进而改变系统养分循环并损害环境质量。当前亟需阐明水生环境中入侵物种的生态影响过程，其中与分解相关的过程是核心研究内容之一。本研究针对巴拉那盆地波尔图普里马韦拉水库与朱皮亚水库中的入侵沉水大型植物（submerged macrophytes）——本土种伊乐藻（Egeria densa Planch）与外来种黑藻（Hydrilla verticillata (L.f.) Royle）的厌氧分解（anaerobic decomposition）过程展开评估。研究测定了有机质降解、淋溶产物的腐殖化程度、分解过程的电导率与pH值，并利用数学模型描述了随时间变化的分解模式。两种植物均表现出相似的有机质降解与碳矿化异质性模式；碳矿化模型与实验获取的数据拟合效果良好。两种植物的分解过程无显著差异。两类植物的培养实验均显示，其颗粒态有机碳（Particulate Organic Carbon, POC）矿化半衰期较短，而溶解态有机碳（Dissolved Organic Carbon, DOC）矿化速率较低。