USGS - science for a changing world

South Atlantic Water Science Center - North Carolina Office

South Atlantic WSC Home Data Projects Publications Drought Floods Media About Us Contact

Picture of the main North Carolina Water Science Center office.


Annual Water Data Report

USGS Publications Warehouse


USGS Water Science Centers are located in each state.

There is a USGS Water Science Center office in each State. Washington Oregon California Idaho Nevada Montana Wyoming Utah Colorado Arizona New Mexico North Dakota South Dakota Nebraska Kansas Oklahoma Texas Minnesota Iowa Missouri Arkansas Louisiana Wisconsin Illinois Mississippi Michigan Indiana Ohio Kentucky Tennessee Alabama Pennsylvania West Virginia Georgia Florida Caribbean Alaska Hawaii New York Vermont New Hampshire Maine Massachusetts South Carolina North Carolina Rhode Island Virginia Connecticut New Jersey Maryland-Delaware-D.C.

Fixed- count and proportional benthic invertebrate subsampling methods: A comparison of efficacy and cost

Project Abstract
By Tom F. Cuffney, Stephen R. Moulton, II, James L. Carter, and Terry M. Short


The efficacy and cost of fixed-count (100-600 organisms) and proportional (1-25% of volume) subsampling methods were compared using computer simulations. Data from over 600 invertebrate samples collected by the USGS's National Water-Quality Assessment Program were used to define communities from which fixed-count and proportional subsamples were drawn. Subsamples were then compared to the original sample data to assess the efficacy of the method. Costs were assumed to be directly proportional to the number of organisms processed. The accuracy of fixed-count subsampling tended to decrease as the number of organisms and taxonomic diversity of the sample increased. Proportional subsampling provided a more accurate and more consistent representation of the underlying community over a wide range of sample richnesses and abundances. However, this increase in accuracy was accompanied by widely variable (800 fold) processing costs. Average processing costs were reduced only when the proportion of the sample processed was low. Under these conditions, the proportional method provided results that were not significantly different from the fixed-count method. Therefore, the fixed-count subsampling method is probably the more cost effective processing strategy for most monitoring programs.

Cuffney, T.F., Moulton, S.R., Carter, J.L., and Short, T.M., 2000, Fixed- count and proportional benthic invertebrate subsampling methods: A comparison of efficacy and cost [abs.]: Bulletin of the North American Benthological Society, v. 17, no. 1, p. 144.
For more information, contact To order printed copies
North Carolina Water Science Center
U.S. Geological Survey
3916 Sunset Ridge Road
Raleigh, North Carolina 27607
(919) 571-4000
Available from NABS Bulletin, Allen Press, 1041 New Hampshire Street, Lawrence, KS 66044, or from the NABS web site,

USGS Home Water Climate Change Core Science Ecosystems Energy and Minerals Env. Health Hazards

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: North Carolina Web Development Team
Page Last Modified: Tuesday, 06-Dec-2016 10:53:01 EST