ABSTRACT Knowledge of trophic status is fundamental to understanding the condition and function of lake ecosystems. We developed regression models to predict chlorophyll a concentrations (chl a) in New Zealand lakes for reference and current states, based on an existing dataset of total nitrogen (TN) and total phosphorus (TP) concentrations for 1031 lakes. Models were then developed to predict Secchi depth based on chl a and a sediment resuspension term applicable to shallow lakes. Estimates of all four Trophic Level Index (TLI) variables (chl a, TN, TP and Secchi depth) were analysed to estimate reference and current state TLI for the nationally representative sample of 1031 lakes. There was a trend of eutrophication between reference and current states, with systematic differences among lake geomorphic types. Mean chl a increased 3.5-fold (2.42 mg m−3 vs. 8.32 mg m−3) and mean Secchi depth decreased (indicating lower clarity) by approximately one-third (9.62 m vs. 6.48 m) between reference and current states. On average, TLI increased by 0.67, with the TLI increase >1 in approximately one-third (31%) of lakes. This study informs the status of lake ecosystems in NZ and provides benchmarks to guide management and assessment.

中文翻译：

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新西兰湖泊的参考和当前营养水平指数：为湖泊管理和评估提供信息的基准

摘要 营养状态的知识是了解湖泊生态系统状况和功能的基础。基于 1031 个湖泊的总氮 (TN) 和总磷 (TP) 浓度的现有数据集，我们开发了回归模型来预测新西兰湖泊中的叶绿素 a 浓度 (chl a) 以供参考和当前状态。然后开发了基于 chla 和适用于浅湖的沉积物再悬浮项来预测 Secchi 深度的模型。分析了所有四个营养水平指数 (TLI) 变量（chla、TN、TP 和 Secchi 深度）的估计值，以估计 1031 个湖泊的全国代表性样本的参考和当前状态 TLI。参考状态和现状状态之间存在富营养化趋势，湖泊地貌类型之间存在系统差异。平均 chl 增加了 3.5 倍 (2. 42 mg m-3 与 8.32 mg m-3）和平均 Secchi 深度在参考状态和当前状态之间减少（表明较低的清晰度）约三分之一（9.62 m 与 6.48 m）。平均而言，TLI 增加了 0.67，其中大约三分之一 (31%) 的湖泊的 TLI 增加 >1。这项研究为新西兰湖泊生态系统的状况提供了信息，并提供了指导管理和评估的基准。