Evaluation of cyanobacterial blooms in water supply rivers from Joinville city

ABSTRACT The proliferation of cyanobacteria in waters, especially in rivers, is associated with anthropic action, wastewater from industries, agriculture, and the lack of basic sanitation. Many health problems occur due to the cyanotoxins produced by these microorganisms. The present study aimed to evaluate the densities of cyanobacteria and their possible correlations with physical-chemical parameters in waters from supply rivers of the city of Joinville, in order to verify which factors are involved in the growth of these organisms between the years 2015 to 2019. The amount of cyanobacteria cells per milliliter of water were analyzed from the last 5 years of the Cubatão and Piraí rivers, based on the certificates of analysis provided by the current water supply service of Joinville. It was found that the cyanobacteria density values increased in both rivers from the year 2018. The physical-chemical parameters analyzed showed a low correlation with the cyanobacteria density from 2015 to 2019 for the Cubatão and Piraí rivers. To understand this increase in cyanobacteria, other climatic factors such as precipitation and average annual temperature were studied. The expressive increase in precipitation in January 2018, followed by a period of reduced rainfall, in addition to the gradual rising temperature in recent years, might be related to this elevation in the density of cyanobacteria between 2018 and 2019, requiring monitoring of this evolution in the supply rivers of the Joinville city.

摘要 水体中蓝藻（cyanobacteria）的大规模增殖，尤其在河流环境中，与人类活动、工农业废水排放及基础卫生设施缺失存在密切关联。此类微生物分泌的蓝藻毒素（cyanotoxins）可引发多种健康问题。本研究以巴西若因维利市（Joinville）的供水河流为研究对象，旨在评估其蓝藻密度，并探究蓝藻密度与水体理化参数（physical-chemical parameters）的潜在相关性，以明确2015至2019年间驱动此类微生物增殖的影响因素。
研究基于若因维利市当前供水服务机构提供的分析检测报告，对2015至2019年五年间库巴唐河（Cubatão）与皮赖河（Piraí）每毫升水体中的蓝藻细胞数量进行了分析。
结果发现，两条河流的蓝藻密度均自2018年起出现上升。对2015至2019年的理化参数分析显示，其与库巴唐河、皮赖河的蓝藻密度仅存在较弱相关性。
为厘清蓝藻密度上升的成因，本研究进一步考察了降水量与年平均气温等其他气候因子。2018年1月降水量的显著激增，叠加随后一段降雨偏少时段，加之近年气温逐步升高的趋势，或与2018至2019年蓝藻密度的上升存在关联，这提示需对若因维利市供水河流的这一演化趋势开展持续监测。