Estuary ecological resilience can be gauged by response of estuary trophic state to abatement of nutrient pollution. Changes in trophic indicators were studied in the Avon-Heathcote Estuary (AHE) in Christchurch, New Zealand, over 6 years, spanning diversion of city wastewater inputs to an offshore outfall in 2010, and to temporary enrichment caused by the 2011 Christchurch earthquake. It was hypothesised that the tidally well-flushed and sandy AHE would not harbour a ‘legacy’ of eutrophication and would rapidly gain improved ecological function following the diversion. AHE sediments were coarse (156 μm median grain size) with low organic matter (OM 1.2%, N 0.03%, C 0.3%), which changed little either with diversion or earthquake. Upon diversion, median water column and porewater ammonium (36, 185 μmol) decreased by 87% and 57%, respectively, benthic microalgae (269 mg chlorophyll-a m⁻²) fell by 58%, and enrichment-affiliated polychaetes (3700–8000 m⁻²) fell by 60–80% at sites with largest benthic microalgal reductions, all within < 1–2 years. Oxygen and ammonium fluxes were usually oligotrophic and changed little upon diversion, except near the historic wastewater discharge site. Denitrification became more important for N loss, increasing from 5 to 29% of estuary N load. Responses to earthquake-driven enrichment were transient. Despite decades of heavy N loading and eutrophic growths of benthic microalgae and macroalgae, the AHE did not store a eutrophic legacy in its sediments. It reacted rapidly to improved water quality allowed by the outfall, showing that this common estuary type (sandy, well-flushed tidal lagoon) was resilient to eutrophication upon stressor removal.

中文翻译：

---

引水和地震扰动后的潮汐泻湖河口生态恢复的营养指标

可以通过河口营养状态对减少养分污染的响应来评估河口的生态适应力。在过去的6年中，在新西兰克赖斯特彻奇的Avon-Heathcote河口（AHE）中研究了营养指标的变化，其范围包括将城市废水输入转移到2010年的海上排污口，以及2011年克赖斯特彻奇地震造成的临时浓缩。据推测，潮汐流沙质的AHE不会富营养化的“遗留”，并且在改道后会迅速获得改善的生态功能。AHE沉积物较粗（中值粒径为156μm），有机质含量较低（OM 1.2％，N 0.03％，C 0.3％），无论是分流还是地震，其变化都很小。转移后，中位水柱和孔隙水铵（36、185μmol）分别减少了87％和57％，a  m ^-2）下降了58％，富集关联的多毛羚（3700–8000 m ^-2）在底栖微藻减少量最大的地点（均在1-2年内）下降了60-80％。氧气和铵的通量通常是贫营养的，在转移时变化不大，除了历史悠久的废水排放点附近。反硝化对于氮损失变得越来越重要，从河口氮负荷的5％增加到29％。对地震驱动的富集的反应是短暂的。尽管数十年来氮负荷沉重，底栖微藻和大型藻类富营养化，但AHE并未在其沉积物中保留富营养化的遗产。它对排水口允许的水质改善做出了快速反应，表明这种常见的河口类型（沙质，冲洗良好的潮汐泻湖）在去除压力源后具有富营养化的能力。