‘Speed dating’ with diatoms …

The day after the meeting about RAPPER, I was supposed to lead an informal workshop on rapid ecological assessment using algae.  However, heavy rain earlier in the week and especially on the night before meant that the streams were turbid and swollen, making it impossible to see what was growing on the river bed.  The few stones that we did manage to pull out from the stream margins suggested that most of the algae had been scoured away by the spate.

Instead, we retreated to the classroom after lunch for an alternative exercise that I had thought up.  The idea was this: Maria and I had diatom slides from seven sites which we circulated around the group.   Each person had five minutes to look at a slide, make some notes on its composition and then to guess the quality of the stream that the sample came from.   When I explained this in the pub the night before, a colleague said “ah … .like speed dating, but with diatoms.”


“Speed dating” with diatoms: rapid assessment of ecological status, Penrith, October 2013.

The dozen or so participants varied in experience; some of those with experience came from outside UK or had previously worked on lakes rather than rivers, and I gave them very little background information about the type of streams each sample came from.  Nonetheless, we found 60% of these “speed dating” analyses gave the same result as the detailed analyses that Maria and I had already performed.  People tended to make lists of the most common genera, occasionally picking out the more distinct species, and based their judgements on these.   Even fairly basic knowledge of diatom ecology allowed them to recognise that a sample with lots of Nitzschia was likely to come from a polluted stream whilst one with Tabellaria and Achnanthidium was more likely to come from a clean one.

I told Rick Battarbee about this exercise in the bar later in the evening and he recalled a similar experience in the early days of his research on acidification.  Asked whether a forest in Scotland was responsible for acidifying a water course, he had taken a field microscope and walked up through the catchment, taking samples from the stream at intervals and checking their composition.   He said that it was easy to see to pick out key indicators and whether or not there were marked changes in composition.  In this case, the composition of diatoms from reaches in and below the forest were the same as those in the moorland stretches above the forest, quickly ruling out the original suspicion.

Like RAPPER, which I mentioned in the previous post, approaches such as this have the potential to make biologists much more flexible and reactive.   We need to adjust techniques, for sure, but more important, perhaps, we need to adjust attitudes, both of the biologists themselves and of their managers.   Quick “look-sees” performed in the field with a portable microscope could quickly rule out some hypotheses whilst focus attention on areas within catchments where more detailed investigations are needed.   We are already in a good position to adopt this approach as many biologists already have the basic diatom identification skills plus some ability to differentiate the larger algae.  We just need that attitude shift.  As is so often the case, better science is not always the answer; better use of existing knowledge could yield just as much sooner and at a lower cost.

One thought on “‘Speed dating’ with diatoms …

  1. Pingback: The meaning of … nothing | microscopesandmonsters

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