On high alert for possible radioactive contamination in Russia's Far East, officials say they have enlisted natural allies -- mussels.

Water authorities in Vladivostok said fresh-water mussels installed in the city's water-purification plant to detect heavy-metal pollution also protect against radiation. The highly sensitive Unionidae mussels close their shells as soon as they encounter contaminants in the water, triggering sensors, the agency said.

'The biomonitoring system works well,' Tamara Rozhkova, chief scientist at Primorsky Vodokanal, said in a statement on Wednesday.

Officials said radiation levels in the city, which lies 500 miles northwest of Japan's stricken Fukushima nuclear plant, remain within normal ranges.

俄罗斯远东地区对可能的放射性污染高度戒备，官员说他们已经向大自然中的盟友──扇贝──求援。

符拉迪沃斯托克（Vladivostok）水务机构说，被置于该市水净化厂用来探测重金属污染的淡水扇贝也可防辐射。该机构说，高度敏感的蚌科扇贝一旦在水中遇到污染物就会合上外壳，从而触发探测器。

水务机构Primorsky Vodokanal首席科学家罗斯科娃（Tamara Rozhkova）在周三发表的一份声明中说，这套生物监测体系运行得很好。

官员说，该市的辐射水平仍在正常范围内。这里位于日本出事的福岛核电站西北方向500英里处。