Changes to the impacts of effluent from a large well-treated sewage discharge on a rocky shore in southern Australia were measured after it was upgraded from secondary to tertiary treatment. Two upgrades transformed a 13 year monitoring program into two BACI (Before, After, Control, Impact) experiments. A novel method was used to map changes to the distribution of space-occupying biota on six reefs on three occasions before, and 5 occasions after the first treatment upgrade. Two reefs were near (0–0.4 km) the outfall, two reefs were within the nutrient plume of the outfall (3.6–4.6 km) and 2 reefs were distant (7.5–14 km) from the outfall. The first upgrade resulted in a slow, but marked, increase in the dominant intertidal fucoid Hormosira banksii 3.6–4.6 km from the outfall, correlated with and probably ultimately driven by a decrease in dissolved inorganic nitrogen (DIN). Hormosira recovered or was always present on reefs where DIN was ≤2.0 μM, and never recovered on reefs where DIN was ≥2.5 μM, suggesting that large-scale ecological changes, associated with the loss of Hormosira, are resisted until a threshold mean DIN concentration of ∼2.0–2.5 μM DIN is reached.

澳大利亚南部一处岩石海岸经过良好处理的大型污水排放量在从二级处理升级为三级处理后，对其影响的变化进行了测量。两次升级将一个为期 13 年的监测计划转变为两个 BACI（之前、之后、控制、影响）实验。使用一种新方法绘制了 6 个珊瑚礁上占空间生物群分布的变化图，分别在第一次处理升级之前 3 次和 5 次。两个珊瑚礁靠近排污口（0-0.4 公里），两个珊瑚礁在排污口的营养羽流内（3.6-4.6 公里），两个珊瑚礁远离排污口（7.5-14 公里）。第一次升级导致占主导地位的潮间带岩藻类植物Hormosira bankii缓慢但显着增加距排污口 3.6-4.6 公里，与溶解无机氮 (DIN) 的减少相关并可能最终由其驱动。Hormosira恢复或始终存在于 DIN ≤ 2.0 μM 的珊瑚礁上，并且从未在 DIN ≥ 2.5 μM 的珊瑚礁上恢复，这表明与Hormosira丧失相关的大规模生态变化在阈值平均 DIN 浓度之前受到抵抗达到~2.0-2.5 μM DIN。