Epilithic diatom samples are collected annually (June -September) by ENSIS/ECRC where the samples are also prepared and analysed.
At stream sites, five cobble size stones are selected from pools at a depth below that of minimum flow, in three discrete locations -upstream, middle and downstream of a surveyed 50 m reach. At lake sites five cobble size stones are selected from the permanently submerged littoral at three or four surveyed locations around the shore, with areas close to inflow or outflow streams being avoided. Epilithic diatoms are removed by brushing into a clean funnel and plastic vial then preserved immediately. From the start of monitoring to 2014 Lugols Iodine was used as the preservative. In 2015 this was changed to 100% ethanol in order to future-proof archived samples for eDNA analyses.
Samples are prepared using standard techniques (Battarbee et al. 2001) and examined by light microscopy at x1000 magnification. Three hundred valves are counted from each sample and identified to species level and the abundance of each taxon is expressed as a percentage of the total count. Identification and nomenclature follows that developed by the Royal Society SWAP programme (Munro et al. 1990) and subsequently maintained and updated in DIATCODE at the ECRC. Slides and suspensions are archived for quality control.
All diatom count data are stored on the central Amphora biological database. For the purpose of the UK UWMN annual data reports, results from all locations at a particular site are combined and a list of taxa comprising > 1% of the total count is presented, together with other summary statistics for each site.
- Battarbee, R. W., Jones, V. J., Flower, R. J., Cameron, N. G., Bennion, H., Carvalho, L. & Juggins, S. (2001) Diatoms. In: Tracking Environmental Change Using Lake Sediments: Volume 3. Terrestrial, Algal and Silaceous Indicators, 155-202, Kluwer Academic Publishers, Dordrecht, The Netherlands.
- Munro, M. A. R., Kreiser, A. M., Battarbee, R. W., Juggins, S., Stevenson, A. C., Anderson, D. S., Anderson, N. J., Berge, F., Birks, H. J. B., Davis, R. B., Flower, R. J., Fritz, S. C., Haworth, E. Y., Jones, V. J., Kingston, J. C. & Renberg, I. (1990) Diatom Quality-Control and Data Handling. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences, 327, 257-261.