197 Marchant box vs. Caton tray: A comparison of macroinvertebrate subsampling repeatability and cost effectiveness

Tuesday, May 19, 2009
Ambassador Ballroom
Gary Lester , EcoAnalysts, Inc., Moscow, ID
Steve Wells , EcoAnalysts, Inc., Moscow, ID
Dawn Hamilton , EcoAnalysts, Inc., Moscow, ID
The preferred subsampling device for the United States Environmental Protection Agency’s EMAP surveys is the Caton tray (EPA 2004, 2007), while Environment Canada prefers to use the Marchant box for the CABIN program (Reynoldson et al 2007). EcoAnalysts, Inc. has processed over 25,000 macroinvertebrate samples from all areas of the USA using the Caton tray and we have processed hundreds of samples across Canada using the Marchant box. Concerns raised by our laboratory staff indicated the Marchant box was relatively cumbersome and time consuming to use. In response to these concerns we initiated a comparability study to determine if the two devices could produce similar results. Thirty samples were selected for this study. Fifteen samples were first sorted using a Caton tray, invertebrates were identified to genus/species where possible and replaced into the original sample matrix, then the samples were sorted using a Marchant box and invertebrates were identified again. The remaining 15 samples were first processed with a Marchant box then with a Caton tray. We are now comparing taxa lists, similarity indices, bioassessment indices, and sample sorting times and will present these results at NABS.
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