HR: 08:45h
AN: NB51F-02    [Abstracts]
TI: Controlling Bias and Managing Effort in Benthic Macroinvertebrate Sorting and Subsampling
AU: * Pavlik, K L
EM: Kristen.Pavlik@tetratech.com
AF: Tetra Tech, Inc., 400 Red Brook Blvd., Ste. 200, Owings Mills, MD 21117 United States
AU: Gallardo, C
EM: Carolina.Gallardo@tetratech.com
AF: Tetra Tech, Inc., 400 Red Brook Blvd., Ste. 200, Owings Mills, MD 21117 United States
AU: Stribling, J B
EM: James.Stribling@tetratech.com
AF: Tetra Tech, Inc., 400 Red Brook Blvd., Ste. 200, Owings Mills, MD 21117 United States
AB: Laboratory benthic macroinvertebrate sample processing is an important yet time-consuming aspect of biological assessments. Using a 30-grid square Caton sorting tray, many protocols specify that grids are selected and organisms picked until the target number is reached. We evaluated level of effort expenditures for 5 different county, state, and national level projects comprising a total of 730 samples with target levels of 100, 200, 300, and 500 organisms. Up to 26% of the samples did not reach the project-specific target level, even when the entire sample was sorted. Reasons vary for the sparseness of samples, ranging from extremely heavy impairment, naturally low productivity, or potentially poor field sampling. In these cases it is often obvious, after only a portion of the sample has been sorted, that the target will not be attained. We describe the capturing of QC information or sorting and subsampling bias, quantified as the proportion of missed specimens recovered by independent re-checks, and suggest a performance characteristic of sorting efficiency >90%. We also propose a potential stop-sort criterion, where, if used in the projects we evaluated, would have saved approximately 1650 person-hours.
DE: 9810 New fields (not classifiable under other headings)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly