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Ecological integrity assessment and degradation diagnosis are used globally to evaluate the health of water bodies and pinpoint critical stressors. However, current studies mainly focus on separate evaluation or diagnosis, leading to an inadequate exploration of the relationship between stressors and responses. Here, based on multiple data sets in an urban lake system, a synchronous evaluation-diagnosis model with quantitative stressor-response analysis was advanced, aiming to improve the accuracy of evaluation and diagnosis. The weights for key physicochemical stressors were quantitatively determined in the sequence of NDAVI adj > COD Mn > TP > NH 4 + -N by the combination of generalized additive model and structural equation modeling, clarifying the most significant effects of aquatic vegetation on the degradation of fish assemblages. Then, sensitive biological metrics were screened by considering the distinct contributions of four key stressors to alleviate the possible deviation caused by common methods. Finally, ecological integrity was evaluated by summing the key physicochemical stressors and sensitive biological metrics according to the model-deduced weights instead of empirical weights. Our system's diagnosis and evaluation results achieved an accuracy of over 80% when predicting anthropogenic stress and biological status, which highlights the great potential of our multiple-level system for ecosystem management.

The spatial and temporal distributions of short-, medium-, and long-chain chlorinated paraffins (SCCPs, MCCPs, and LCCPs) were studied in sediment cores and surface sediment from nine lakes in China. The highest total CP concentrations in surface sediment were found in the plateau lakes of southwest China, followed by lakes in the northeast, east, and remote northwest. The concentrations of three CP groups in cores showed an increasing trend from the 1970s to 2014, with the most rapid increase occurring from the late 2000s to 2014, consistent with the statistics on historical production of CPs in China. The three CP groups showed site-specific profiles in sediments from the nine lakes, and their percentages changed with sedimentary years. In sediment samples with dated year after 1980, MCCPs were dominant in sediment from Lakes Sihailongwan maar, Taihu, Erhai, and Chenghai, and LCCPs were predominant compounds in the other five lakes. The proportions of LCCPs rapidly increased after 1980, reflecting the increasing production and usage of LCCPs in China. The total burdens of ∑SCCPs, ∑MCCPs, and ∑LCCPs in sediment prior to 2006 were estimated to be 0.26-5100, 0.29-21000, and 0.07-4300 kg, respectively, which were 1.4-440-fold higher than those of ∑PBDEs.