0 a way of measuring the pollution (= dirty substances) in water, e.g. a river, by counting the organisms in it -- 生物指数
Biotic index surveys report mayfly and stonefly nymphs, caddis fly larvae, dragonfly and damselfly nymphs and crayfish.
Other historically important work sought to provide biotic indices for classifying waters according to the biotic communities that they supported.
