Aquatic bio-assessment and uncertainty
Water Framework Directive (WFD)
The WFD of the European Union requires all member countries to assess, monitor and where necessary improve, the ecological quality and condition of its water bodies (rivers, lakes and estuaries). The assessment should be based on the observed taxonomic composition for one or more of macro-invertebrates, fish, diatoms/phytoplankton and macrophytes, and habitat condition, in relation to that expected for that physical type of site if it was in a high quality reference condition. The WFD requires all individual water bodies to be classified to one of five ecological status classes (high, good, moderate, poor and bad) with the aim of achieving good or better status of all water bodies by 2015.
RIVPACS (River InVertebrate Prediction And Classifcation System)
RIVPACS provides a standardised methodology for assessing the ecological quality of UK rivers. It is based on a statistical model relating the environmental features of a wide range of types of high quality river sites to their macro-invertebrate fauna, which is used to predict the fauna to be expected at any particular UK river site if it was also unstressed and in reference condition.
Comparing the observed (O) fauna (sampled using the same protocols) with the site-specific expected (E) fauna, provides standardised measures of the ecological quality for a river stretch.
RIVPACS is used by the Environment Agency, Scottish Environment Protection Agency (SEPA) and Environment Heritage Service (EHS) Northern Ireland to assess and monitor the biological condition of all UK rivers.
Uncertainty in WFD aquatic bio-assessments
A measure or index of the biological quality of a river site or lake is of little value without some knowledge of the levels of uncertainty in its estimates. What are the chances that the quality of a site classified as good WFD status could have been moderate ? When index values vary between years, is this a result of real change or simply due to sampling variation and predictive modelling errors ?
Experience
Ralph Clarke, formerly of CEH, has been involved in the long-term development of RIVPACS, and continues his collaboration with CEH.
Ralph Clarke has led the statistical aspects of research projects funded by the EA, SNIFFER and EU involving replicated sampling programmes and the development of simulation procedures to assess the uncertainty (i.e. potential error) in classifying river and lakes to Water Framework Directive (WFD) ecological status class.
He also produced STARBUGS (STAR Bioassessment Uncertainty Guidance Software) within the EU FP5 project STAR involving 14 countries
Current research projects:
A new joint research project with CEH /NERC, funded by SNIFFER, aims to improve the RIVPACS predictive models for UK rivers and derive simulation methods and parameter estimates to assess uncertainty involving temporal sampling variability and change.
Develop statistical methods to assess the precision of WFD indices of lake condition which allow for seasonal sampling effects (with the EA).
Publications
Clarke, R.T., Furse, M.T., Gunn, R.J.M., Winder, J.M. & Wright, J.F. 2002. Sampling variation in macroinvertebrate data and implications for river quality indices. Freshwater Biology, 47, 1735-1751.
Clarke, R.T., Wright, J.F. & Furse, M.T. 2003. RIVPACS models for predicting the expected macroinvertebrate fauna and assessing the ecological quality of rivers. Ecological Modelling, 160, 219-233.
Davy-bowker,j., Clarke, R.T., Johnson, R.K., Kokes, J., Murphy, J.F. & Zahrádková, S. 2006.. A comparison of the European Water Framework Directive physical typology and RIVPACS-type models as alternative methods of establishing reference conditions for benthic macroinvertebrates. Hydrobiologia, 566, 91-108.
Clarke, R.T. & Hering, D. 2006. Errors and uncertainty in bioassessment methods – major results and conclusions from the STAR project and their application using STARBUGS. Hydrobiologia, 566, 433-440.
Staniszewski, R., Szoszkiewicz, K., Zbierska, J., Lesny, J., Jusik, S. & Clarke, R.T. 2006. The macrophyte survey sensitivity and assessment of error sources, Hydrobiologia, 566, 235-246.
Clarke, R.T., Lorenz, A., Sandin, L., Schmidt-kloiber, A., Strackbein, J., Kneebone, N.T. & Haase, P. 2006. Effects of sampling and sub-sampling variation using the STAR-AQEM sampling protocol on the precision of macroinvertebrate metrics. Hydrobiologia, 566, 441-460.
Clarke, R.T., Davy-bowker, J., Sandin, L., Friberg, N., Johnson, R.K. & Bis, B. 2006. Estimates and comparisons of the effects of sampling variation using European ‘national’ macroinvertebrate sampling protocols on the precision of metrics used to assess ecological status. Hydrobiologia, 566, 477-504.
Clarke, R.T. & Murphy, J.F. 2006. Effects of locally rare taxa on the precision and sensitivity of RIVPACS bioassessment of freshwaters. Freshwater Biology, 51, 1924-1940.
For further information, contact Ralph Clarke
| School of Conservation Sciences | |
| Bournemouth University Christchurch House Talbot Campus Poole Dorset BH12 5BB UK |
Email: consci@bournemouth.ac.uk Website: www.bournemouth.ac.uk/cceec/ Tel: +44 (0) 1202 965178 Fax: +44 (0) 1202 965530 |
