Comprehensive analysis of cyanobacterial secondary metabolites distribution and toxicity in urban water bodies.

This study addresses the increasing concern regarding cyanotoxin contamination of water bodies, highlighting the diversity of these toxins and their potential health implications. Cyanobacteria, which are prevalent in aquatic environments, produce toxic metabolites, raising concerns regarding human exposure and associated health risks, including a potential increase in cancer risk. Although existing research has primarily focused on well-known cyanotoxins, recent technological advancements have revealed numerous unknown cyanotoxins, necessitating a comprehensive assessment of multiple toxin categories. To enhance the cyanotoxin databases, we optimized the CyanoMetDB cyanobacterial secondary metabolites database by incorporating secondary fragmentation patterns using the Mass Frontier fragmentation data prediction software. Water samples from diverse locations in Shanghai were analyzed using high-resolution mass spectrometry. Subsequently, the toxicity of cyanobacterial metabolites in the water samples was examined through acute toxicity assays using the crustacean Thamnocephalus platyurus. After 24 h of exposure, the semi-lethal concentrations (LC50) of the water samples ranged from 0.31 mg L-1 to 1.78 mg L-1 (MC-LR equivalent concentration). Our findings revealed a critical correlation between the overall concentration of cyanobacterial metabolites and toxicity. The robust framework and insights of this study underscore the need for an inclusive approach to water quality management, emphasizing continuous efforts to refine detection methods and comprehend the broader ecological impact of cyanobacterial blooms on aquatic ecosystems.

[Effect of cultivation for snail control on schistosomiasis in Changsha urban section of Xiangjiang River].

OBJECTIVE: To study a reliable, friendly environmental and sustainable Oncomelania snail control method in marshlands of the Xiangjiang River. METHODS: According to the special characteristics of the marshlands of the Xiangjiang River, smoothing and cultivating in beaches were applied for snail control. In sections with scarce distribution of snails, lowering parts of 4.4 beaches and raising other parts were added. RESULTS: Since 2003, the project has been practiced for 8 years. The average snail density declined by 99.83% with the simple smoothing beaches and then cultivation there. The average snail density declined by 100% with lowering parts of beaches and raising other parts and then cultivation. The schistosome infection rate was 0.31% with a declined rate of 93.84% in residents in 2006. The schistosome infection rate was 1.03% in 2010. The test result of water contamination was negative. CONCLUSIONS: The method of simple smoothing beaches and then cultivation can control the density of snails in marshlands and the method of lowering parts of beaches and raising other parts and then cultivation is more effective.