近日，美国《国家科学院院刊》发表题为《蓝藻水华逆转的早期预警响应》的文章，展示了一个能识别藻华发展态势的自动化监测系统，如水体中藻类的快速生长及氧气的消耗。该系统能提前预测藻华的全面爆发，为及时阻止藻华进一步发展提供了帮助。

　　来自美国弗吉尼亚大学和新泽西州立大学等机构的研究人员测试了未发生藻华的早期预警是否可被用来作为干预（即停止营养的增加），以阻止向蓝藻细菌占主导地位的条件转变。研究人员利用密歇根的彼得湖和保罗湖作为实验场所进行3组实验：第一个湖中每日添加无机氮和磷逐步使其富营养化而诱发藻华（实验湖）；第二个湖没有进行富营养化处理（参照湖）；第三个湖持续进行富营养化处理（周二湖）。他们测量了3个生态系统变量-色素叶绿素a、藻青蛋白、溶解氧的百分饱和度，并计算了两个弹性指标。

　　当弹性指标超过预设界限，马上停止实验湖泊中营养物质的流入。此时，海藻色素、溶解氧饱和度和pH值迅速下降，实验湖泊最终的水体状况与没有进行富营养处理的湖泊相似，而持续进行富营养化的湖泊形成了大规模藻华。该监测系统能在藻华爆发前两周作提前预警。一旦营养物质停止流入，则藻华可被逆转。

　　Michael L. Pacea; Ryan D. Battb; Cal D. Buelo; et al.

　　Directional change in environmental drivers sometimes triggers regime shifts in ecosystems. Theory and experiments suggest that regime shifts can be detected in advance, and perhaps averted, by monitoring resilience indicators such as variance and autocorrelation of key ecosystem variables. However, it is uncertain whether management action prompted by a change in resilience indicators can prevent an impending regime shift. We caused a cyanobacterial bloom by gradually enriching an experimental lake while monitoring an unenriched reference lake and a continuously enriched reference lake. When resilience indicators exceeded preset boundaries, nutrient enrichment was stopped in the experimental lake. Concentrations of algal pigments, dissolved oxygen saturation, and pH rapidly declined following cessation of nutrient enrichment and became similar to the unenriched lake, whereas a large bloom occurred in the continuously enriched lake. This outcome suggests that resilience indicators may be useful in management to prevent unwanted regime shifts, at least in some situations. Nonetheless, a safer approach to ecosystem management would build and maintain the resilience of desirable ecosystem conditions, for example, by preventing excessive nutrient input to lakes and reservoirs.

　　（来源：PNAS, 2017, 114(2): 352-357）