Following urbanization, a large number of urban rivers were contaminated and turned to black-odor rivers. The traditional approach for detecting water quality is based on chemical or physical analysis. However, biological toxicity of black-odor water has been less addressed. As two typical black-odor rivers, Jiushanwai River (JS) and Shanxia River (SX) are tributaries of Wen-Rui Tang River in Wenzhou (south of China). The eco-safety of the urban rivers was evaluated by bioassay for water toxicity in this study. Ten and 5 sampling sites were respectively set along JS and SX. Water samples were collected monthly from October 2010 to October 2011. The general physical and chemical parameters of river water were monitored. In order to investigate the ecotoxicological effects of black-odor water, the following bioassays were used: (1) Fish acute toxicity test (Danio rerio, comprehensive toxicity), (2) luminescent bacteria bioassay (Qinghaiensis vibrio, toxicity to bacteria), and (3) tropical claw embryo assay (Xenopus tropicalis, embryo toxicity). Biotoxicity of black-odor rivers water was demonstrated by D. rerio, Q. vibrio, and X. tropicalis embryos. Toxicological effects of black-odor water were respectively shown by mortality of zebrafish, and by the relative inhibitory light rate of luminescent bacteria. However, luminescent bacteria were more sensitive to inspect biotoxicity than zebrafish. In X. tropicalis embryos test, toxicological effects of black-odor water were mostly shown by embryos' survival rate and teratogenic rate. Bioassay results showed that toxicity of SX water was higher than that of JS water, especially in summer. Statistical analysis of luminescent bacteria toxicity test showed that biotoxicity of SX and JS was high in summer, but low in winter and spring. The seasonal changes of water toxicity of the black-odor river were positively correlative with changes of water temperature (p < 0.05), and related to pH and ammonium nitrogen of water. Typical black-odor river water displays different degrees of biotoxicity to D. rerio, luminescent bacteria, and X. tropicalis embryos. The ecotoxicological risk of black-odor rivers was demonstrated in urban area, which suggests bioassay is necessary for evaluation of water quality. In the present study, spatial and seasonal bioassay for toxicity of JS and SX provides a complete example for evaluation of urban rivers.

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Sea surface temperature (SST) is a key marine ecological metric. An optimized split-window algorithm was used to invert the Yangtze Estuary’s temperature field during a cold wave process. Additionally, MODIS SST inversion results were used to explore the effects of typical cold waves on the Yangtze Estuary’s temperature field through the application of a temperature profile analysis method and a multiscale, multidirectional edge detection algorithm. According to the findings, (1) the cold wave altered the temperature field characteristics and the temperature front intensity, morphology, and spatial distribution pattern within the Yangtze Estuary for a short period. The strong temperature front displayed irregular edges and scattered patterns due to the combined effects of cold water masses produced by the cold wave and the tides and the warm water currents outside the mouth. (2) The cold wave caused significant short-term deviations in the Yangtze Estuary’s SST. The cold water tongue stretched across the entire Yangtze Estuary, where the temperature dropped sharply with time, with the maximum cooling occurring outside the mouth, at 12.2 °C, and the minimum cooling occurring inside the mouth, at only 5.5 °C. (3) The spatially gradual warming of the Yangtze Estuary’s SST from inside to outside the mouth became a low–lower–high pattern during cold waves. (4) The cold wave exhibited a greater influence on the strength, form, and distribution of the temperature front. Studying the effects of cold waves on the Yangtze Estuary’s temperature field has significant theoretical and practical implications for understanding the changes in the winter temperature field, environmental protection, disaster mitigation, and prevention.