HR: 1330h
AN: NB33B-13    [Abstracts]
TI: The Effects of a Large/Rare Sub-sample on a Macroinvertebrate Index of Biological Integrity (IBI) and Associated Metrics.
AU: * Chirhart, J
EM: joel.chirhart@pca.state.mn.us
AF: Minnesota Pollution Control Agency, 520 Lafayette Road, St. Paul, MN 55155 United States
AB: It has become common practive among those who collect macroinvertebrates for water quality assessment to use a two-phase subsampling procedure, including a fixed count subsample and a large and/or rare subsample. For the past 8 years the Minnesota Pollution Control Agency has supplemented a 300 organism fixed count subsample with a 15-20 minute scan for large/rare taxa. The decision to use this process was based on previous work indicating that the inclusion of a large/rare subsample substantially increased taxonomic richness. The MPCA is currently completing a statewide survey, with the intent of developing regional Indices of Biological Integrity (IBI) for the state of Minnesota. Before begining another statewide sampling rotation we decided that it would be wise to investigate the effect that the large/rare sub-sample component has on our current data set. Specifically, we wanted to examine the possibilty that the large/rare sub-sample was contributing unwanted variability to our data set, resulting in a less reliable IBI. Comparisons between each data set were made to determine the variance effects on individual metrics and IBI score.
DE: 0400 Biogeosciences
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly