Gosh, nearly went in. I think that's about three minutes now, so shall we call it a day? Yup. So I just tip it all in? Yeah, tip it in. Push it around a bit. There's all sorts of little creatures whizzing about all over the place. This is a flat-bodied stone clinger. Looks a bit scorpion-like in a way. Yeah. These are the ones that are very sensitive to pollutants, so they'd be the first things that would disappear. I mean, this is an olive, so the olives will tend to stay in the river after the stone flies and the flat-bodied ones have gone. So are people expected to actually to look at a tray like this and count every single one? Presumably not. No. We estimate the abundance, and then if this number suddenly dropped from hundreds to tens or from tens just to singles, then you know there might be a problem. To an untrained eye this looks like a healthy river. Would you say it is? Yeah? Well, I wouldn't say you're untrained, you've been on the course all day. No, I agree, it looks pretty healthy, you've got high abundance of most of the groups, and all of the target groups are present there. Yeah. So can't really hope for anything better.


天，差点掉下去。现在差不多有三分钟了，这样就够了吗？ 是的 -倒出来就行了吗 -是，倒出来，稍微晃晃。这里有各种小生物嗖嗖地游来游去。这是种黏着在石头上的扁体虫，长得有点像蝎子。 是的，它们对污染物非常敏感。所以如果有污染，它们会首先消失。这是只榧螺，榧螺更喜欢待在河里。即使污染严重到石蝇和扁体昆虫消失，所以人们真准备看着这个托盘，对每种昆虫计数吗？ 应该不会吧 不，我们对数目进行估计。如果数目突然从几百骤减至几十，或者从几十减至几个，那么就可能存在污染问题了。对于未经训练的我，这条河好像挺健康的。你觉得呢？ 是吗？我觉得你算经过训练吧。你整天都泡在这个研究上。 不，我同意，它看上去挺健康。毕竟你已取得大部分种群的大量样本，我们预期的种群都在。 -没错 -所以情况很不错了