Abstract：
Control of algal blooms and associated biologically-induced water quality risks in drinking reservoirs is problematic. Copper sulphate (CuSO4) treatment is one intervention that has been utilised for >100 years. Evidence indicates a favourable short-term reduction in Cyanobacterial biomass (e.g. bloom termination), but here we indicate that it may also increase longer-term water quality risk. In 2022, we investigated the impacts of CuSO4 spraying on Cyanobacterial communities and nutrient levels within a drinking water supply reservoir using environmental DNA (eDNA) to assess community shifts, alongside monitoring nutrient fractions, orthophosphate (OP) and total phosphate (TP), post-treatment. CuSO4 application successfully reduced Cyanobacterial abundance, however elimination of Cyanobacteria resulted in a shift in bacterial dominance favouring Planctomycetota throughout the summer and a combination of Actinobacteriota and Verrucomicrobiota, throughout autumn. As Cyanobacterial abundance recovered post-treatment, Cyanobacterial genera demonstrated greater diversity compared to only three Cyanobacterial genera present across samples pre-treatment, and included taxa associated with water quality risk (e.g. taste and odour (T&O) metabolite and toxin producers). The increase in Cyanobacteria post-treatment was attributed to an increase in biologically available nutrients, primarily a significant increase in OP. Overall, findings suggest that the significant shift in biodiversity likely induces a less stable ecosystem with greater plasticity of response to changing environmental and biogeochemical variables. Legacy implications of CuSO4 spraying, in terms of shifts in ecosystem and nutrient balance over time, may have implications for drinking water quality, but importantly also for reservoir management options. As such, the effects of CuSO4 spraying should be considered carefully before consideration as a contender for in-reservoir biological control.
摘要：
控制饮用水库中的藻类水华和相关的生物诱导的水质风险是有问题的。硫酸铜(CuSO4)处理是一种已经使用了>100年的干预措施。证据表明蓝细菌生物量的短期减少（例如，水华终止），但在这里我们指出，它也可能增加长期的水质风险。2022年，我们使用环境DNA（eDNA）评估社区变化，调查了CuSO4喷洒对饮用水供应水库中蓝藻群落和营养水平的影响。除了监测营养成分，正磷酸盐（OP）和总磷酸盐（TP），后处理。CuSO4的应用成功地降低了蓝藻的丰度，然而，蓝细菌的消除导致细菌优势的转变，有利于整个夏天的Planctomycetota和放线菌群的组合，整个秋天。随着蓝细菌丰度在治疗后恢复，与样品预处理中存在的仅三个蓝细菌属相比，蓝细菌属表现出更大的多样性，并包括与水质风险相关的分类群(例如味道和气味(T&O)代谢物和毒素生产者)。蓝细菌治疗后的增加归因于生物可用营养素的增加，主要是OP的显着增加。总的来说,研究结果表明，生物多样性的显着变化可能会导致生态系统不太稳定，对环境和生物地球化学变量的响应具有更大的可塑性。CuSO4喷涂的传统影响，随着时间的推移，生态系统和养分平衡的变化，可能对饮用水质量有影响，但对于水库管理选项也很重要。因此，在考虑将CuSO4喷雾作为水库内生物防治的竞争者之前，应仔细考虑其效果。
