My two recent posts which dealt with rapid assessment using algae both largely ignored the elephant in the corner of the room: the need for a microscope to identify the organisms we find. “Rapid assessment” is protracted by the need to bring samples back to the laboratory in order to check their composition. I mentioned Rick Battarbee’s use of a field microscope in my post of 29 October, so perhaps we should look at this idea in a little more detail?
I have had a field microscope for a few years now. It is a Pyser-SG1 (which looks remarkably similar to the McArthur-type field microscope now available from Brunel Microscopes. It is an inverted microscope (i.e. the objectives are below the slide) with a built-in light source, and is very useful in the field. It lacks a condenser or field diaphragm, making control of the light source difficult, but this is rarely a major problem. It is great for field trips with students, when I have to persuade students that a brownish smear on a submerged rock really is a living organism. The biggest problem, in practice, is fiddling around with slides, Pasteur pipettes and cover slips in anything other than perfect weather conditions.
Left hand image: my Pyser McArthur-type field microscope. The turret contains 4x, 10x and 40x objectives which, combined with the 10x eyepiece, gives magnifications up to 400x. Right hand image: using my field microscope on a field course in County Mayo, Ireland, in 2008.
The major disadvantage is that the discipline itself is not focused on field identifications. My field microscope weighs 1270 grams, a little heavier than my digital SLR. However, the standard Flora of the freshwater algae of Britain and Ireland weighs in at a hefty 2830 grams, substantially more than the laptop on which I am writing. This book does not include the diatoms; identification of these requires you to pack another 2795 grams into your rucksack. I have to rely on memory as the type of portable, accessible field guides that are available for many other groups of organisms are simply not available for the algae. Progress with algal-based rapid assessment methods will almost certainly require better field guides. I have made a start on a booklet for the identification of the larger algae, and had some positive comments from those who have used it. Maybe I can condense the most important taxa onto a fold-out laminated sheet, such as those developed by the Field Studies Council? Or maybe we could put the key information into an app, so that it can be accessed via a smartphone or tablet? Think outside the box …
The two hefty identification guides I mention are:
Hofmann, G., Werum, M. & Lange-Bertalot, H. (2011). Diatomeen im Süsswassser-Benthos von Mitteleuropa. A.R.G. Gantner Verlag K.G., Rugell.
John, D.M., Whitton, B.A. & Brook, A.J. (2011). The Freshwater Algal Flora of the British Isles. 2nd Edition. Cambridge University Press, Cambridge.