The 2009–2010 “El Niño”-Southern Oscillation (ENSO) event was characterized by a warm-phase leading to a five-fold increase in the Río de la Plata river flow and an associated change in trophic state because of organic enrichment. We analyzed the biotic response of benthic communities to such an increased trophic state during this ENSO event using community and biotic indices (diversity indices and AMBI). Polychaeta exhibited the highest richness and second the most abundant values while the small gastropod Heleobia australis was the most abundant and frequent species. An increase in richness and diversity of Polychaeta was associated to a concomitant increase of RdlP flow and the organic enrichment of the macrobenthic species. Community indices (richness and diversity) showed variability at both temporal and spatial scale but only AMBI exhibited spatial variability without significant differences between contrasting environmental conditions (ENOS phases).

2009-2010 年“厄尔尼诺”-南方涛动 (ENSO) 事件的特点是暖期导致拉普拉塔河流量增加五倍，并且由于有机物富集而导致营养状态发生相关变化。我们使用群落和生物指数（多样性指数和 AMBI）分析了在这次 ENSO 事件期间底栖群落对这种增加的营养状态的生物反应。多毛纲的丰富度最高，丰富度次之，而小腹足动物Heleobia australis是最丰富和最常见的物种。多毛纲丰富度和多样性的增加与 RdlP 流量的增加和大型底栖动物物种的有机富集相关。群落指数（丰富度和多样性）在时间和空间尺度上都表现出变异性，但只有 AMBI 表现出空间变异性，而对比环境条件（ENOS 阶段）之间没有显着差异。