The meaning of … nothing

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.


Wonders in my own backyard …

One of my many half-worked out and not-fully-proven theories is that the golden age of Victorian microscopy coincided with an era when many educated British men were heading off to the colonies and sending back reports of weird and wonderful flora and fauna that they encountered.   The microscope was, for those left behind, a similar portal into hitherto unexplored worlds; one that, furthermore, could be found without leaving your own grounds.

A case in point: here is a photograph of some moss on my driveway.  I have walked past these mosses thousands of times without giving it a second thought.   Today, however, I have a point to prove.   The second photograph is a close up of the same moss, taken with the extreme macro lens on my new Olympus TG2 compact camera.   This reveals the colonies to consist of tongue-shaped leaves, each terminating in a long hair-like projection.   My somewhat dated guide to mosses tells me that these are plants of Bryum capillare.   Even at barely a millimetre across, these leaves are enormous compared to the algae I normally write about here.


A row of bright green colonies of Bryum capillare beside my driveway in County Durham, with a lens cap (five cm across) as an indication of scale.

The next step is to strip a few of the leaves off the plants using a pair of forceps and blade and mount these in a drop of water to examine under my high power microscope.   Ironically, the lowest magnification lens I have on this microscope (10x) is too powerful and I cannot get all the leaf into a single image, but we can see the hair point as an extension of the “nerve” that extends the length of the leaf.   Just visible, too, are the long, narrow cells which form a border around the leaf edge.  The cells, themselves, are just a single cell thick, each parallelogram-shaped, about 50 micrometres long and containing a number of small chloroplasts.

I wrote about the tops of boulders being like miniature deserts last year (“Upper Teesdale In March”) and the same applies to man-made habitats such as paths and driveways.  The cushion-like growth forms contains networks of tiny spaces which turn the whole plant into a miniature sponge, soaking up and retaining water, enabling it to continue to grow long after the ground around it has dried up.   In the past, I presume, mosses such as Bryum capillare would have been rare but, with our modifications to the landscape, including building walls and driveways, we have greatly expanded the habitat available to this species.   As a result, our sedentary Victorian naturalist had just as many opportunities to explore deserts as Richard Burton, Charles Montagu Doughty and Wilfred Thesiger.


Bryum capillare.  The left hand image is taken with a macro lens; the right hand image was taken under a microscope; the scale bar is 100 micrometres (1/10th of a millimetre).   The hair is roughly double the length of the portion included in the image.