The rational eutrophication management largely depends on the knowledge of the dynamics in the dissolved inorganic nutrients especially nitrogen forms which trigger exponential primary productivity in eutrophic systems. The present study investigated the phytoplankton interactions with the dissolved N forms, nitrate (NO₃) and ammonium (NH₄) in a sub-tropical Yangtze River tributary, China vulnerable to multiple anthropogenic stressors following the impoundment of the largest hydraulic structure, the Three Gorges Dam. Results indicated strong NO₃ inhibition by the low NH₄ pool exerting toxic effects on the major phytoplankton groups, particularly the Bacilliariophyta (relative abundance < 1%) while significant Cyanophyta proliferation prevailed (relative abundance ≥ 90%). Strong N limitation exacerbated by NH₄ deficit and P replete condition characterizes the summer bloom in the tributary. The biomass attenuation kinetics revealed significantly fast NH₄ metabolism, half-life ($t_{1/2}$= 1.4 d, K = 0.00750 ± 0.004 d⁻¹) as the first-order rate adequately fitted into the experimental data although, the second-order rate also demonstrated considerable goodness of fit. The growth responses induced by the Si enrichment potentially suggested possible secondary limitation by Si with the likelihood of intensification should the ecosystem phytoplankton community dominance shifts from Cyanophyta to the Bacilliariophyta. The response of P enrichment on growth was attributed to luxury consumption rather than limitation as responses only became significant towards the end of the study. The study, therefore, presents the first report of biomass ageing rate worthy of incorporation into the recent bloom management protocol for the development of predictive ecosystem dynamics.

合理的富营养化管理很大程度上取决于对溶解的无机养分（尤其是氮形式）的动力学知识，而氮形式会触发富营养化系统的指数初级生产力。本研究调查了在亚热带长江支流中易受多种人为胁迫因素影响的浮游植物与溶解的N形态，硝酸盐（NO ₃）和铵盐（NH ₄）之间的相互作用，这是由于最大水力结构的蓄积导致的。三峡大坝。结果表明，低NH ₄抑制NO _3的能力强池对主要的浮游植物群，特别是芽孢杆菌属（相对丰度<1％）产生毒性作用，而主要的蓝藻增殖则占优势（相对丰度≥90％）。NH ₄亏缺和P充足的条件加剧了强N限制，这是支流夏季开花的特征。生物质的衰减动力学表明，NH ₄代谢明显加快，半衰期（${Ť}_{\mathrm{1个}/2}$尽管一阶速率足以满足实验数据要求，但一阶速率= 1.4 d，K = 0.00750±0.004 d ^-1），二阶速率也显示出相当好的拟合度。如果生态系统的浮游植物群落优势从蓝藻移到芽孢杆菌，则由硅富集诱导的生长响应可能暗示了硅可能继发的局限性，并可能加剧。磷富集对生长的反应归因于奢侈品消费而非限制，因为这种反应仅在研究结束时才变得重要。因此，该研究提出了第一份有关生物量老化速率的报告，值得将其纳入用于开发预测性生态系统动态的最新绽放管理协议中。