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Monday, May 26, 2008 - 3:30 PM
93
Implications of temporal variation for confidence of bioassessments
Ralph T. Clarke1, John Davy-Bowker2, and John F. Murphy2. (1) Centre for Conservation Ecology and Environmental Change, Bournemouth University, Christchurch House, Talbot Campus, Poole, BH12 5BB, England, (2) River Communities Research Group, Centre for Ecology & Hydrology, c/o Freshwater Biological Association, East Stoke, Wareham, BH20 6BB, England
An estimate of the ecological quality status for a water body (section of river or lake) is usually intended to represent the quality of the water body as a whole over a period of time. The estimate is obtained by sampling/surveying taxonomic components of the biota at one or more locations within the water body at one or more points in time during the period. Sample biota (and thus derived values of biotic indices and quality measures) vary due to the procedures used, natural spatial and temporal variation and changes in response to stress.
Future estimates of the ecological status of river stretches for UK national surveillance monitoring will be based on some measure of “average” quality over three-year periods. To help assess the uncertainty associated with such estimates based on macroinvertebrates, we analysed a combination of datasets spanning 1990-2004 and estimated the relative contributions of local-scale replicate sampling (38-55% total period variance), short-term within-season temporal (17-45%) and longer-term inter-year variability (5-28%) on the precision of a range of biotic indices designed to measure general, organic-, flow- and acidity-related stress. Sampling design and index inter-correlations have implications for confidence of bioassessments.
Web Page: bioassessment, temporal, variability
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See more of The Nabs 56th Annual Meeting (25-28 May, 2008)
See more of Contributed Sessions
See more of The Nabs 56th Annual Meeting (25-28 May, 2008)