I had to dig out some old papers today as background reading for a report I am writing. In the process, I came across one by Horst Lange-Bertalot written in 1979 which implied that, with a knowledge of the ecological requirements of 50 – 100 species of diatom, the condition of almost any river in Europe could be assessed. About a decade later, Frank Round made a similar assertion, going on to suggest that, for a group of organisms to be useful as environmental indicators “… the species should be easily identifiable (modern floras must be available), quantifiable (preferably without time consuming labour and preferably by workers who can be trained to perform the analyses without the need for detailed knowledge of the biology of the organisms”.
How times change. Both Lange-Bertalot and Round played a major role in the paradigm shift that has overwhelmed diatom taxonomy over the past three decades. My own view is that Round’s statement is broadly correct, as I have tried to illustrate in earlier posts (“Lago di Maggiore under the microscope”, “Subsidiarity in action”, “’Speed dating’ with diatoms”). Many of my colleagues around Europe would contest this, and a veritable flood of books and papers describing new species has pushed the process of accurate identification of diatom species out of the reach of the generalist biologists Round was envisaging, to highly-specialised individuals with very expensive microscopes.
However, here is a problem: assume that the community of European diatom analysts is a finite resource, and that effort is disproportionately directed towards taxonomy. Something else has to sacrificed, doesn’t it? To test this idea, I scanned the abstract booklet for the most recent International Diatom Symposium and made a rough classification of the subject matter for the oral presentations. 49 papers dealt with freshwater diatoms. Of these, 20 (41%) were concerned with taxonomy and a further 26% dealt with the spatial or temporal distribution of diatoms with no reference to other groups of organisms. Only two papers dealt with physiology and none at all with functional ecology. Lots of people are interested in the microscopic structure of the diatom cell wall yet almost no-one seems to care about the role that these actually play in freshwater ecosystems.
So we have two problems: the first is that the use of diatoms for ecological assessment has got much more complicated than when Lange-Bertalot and Round were writing their pioneer papers. This has pushed the work into the realm of “experts” who take longer (and cost more) whilst, at the same time, producing outputs that are harder for lay people to digest. The second problem is that the work on which this is based is barely, now, connected to the ecosystem functioning that we claim to want to preserve. Diatomists, it seems, may end up knowing the shape of everything yet the meaning of nothing.
Lange-Bertalot, H. (1979). Pollution tolerance of diatoms as a criterion of water quality estimation. Nova Hedwigia 64: 285-304.
Round, F.E. (1991). Use of diatoms for monitoring rivers. pp. 25-32. In: Whitton, B.A., Rott, E. & Friedrich, G. (editors) Use of Algae for Monitoring Rivers. E. Rott, Institut für Botanik, Universität Innsbruck, Austria.