HR: 1330h
AN: NB33B-03    [Abstracts]
TI: Evaluating the Relative Magnitude of Intra- and Inter-annual Metric Variability
AU: * Carter, J L
EM: jlcarter@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd. MS465, Menlo Park, CA 94025 United States
AU: Fend, S V
EM: svfend@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd. MS465, Menlo Park, CA 94025 United States
AU: Weissich, P
AF: California State University, East Bay, 25800 Carlos Bee Boulevard, Hayward, CA 94542 United States
AB: Understanding the magnitude of both short- and long-term temporal variability in metrics derived from lotic macroinvertebrate assemblages is important for both the design and analysis of water quality assessments. Sampling on an annual or even longer interval is common in programs that assess many sites over large geographic areas. These sampling regimes often lead sampling periods that extend over several months. Extended sampling periods can potentially influence the assessment because of phenological change in the benthic assemblage. To address the question of the effects of short- and long-term variability in common metrics, we collected benthic invertebrates every two weeks for a year from 6 sites. Within-site samples were grouped into 2 month intervals. We also collected annually from 9 sites for a period of 4 years. In general, the range of variation in metrics was similar regardless of temporal scale evaluated. For example, within-site, within-group % mayflies had coefficient of variations that ranged from 6 to 104 and within-site, among-year annual variability ranged from 9 to 111. The similarity in the ranges indicates that short-term temporal variability has the potential to confound the interpretation of long-term variability when evaluating annual or greater changes in benthic assemblage structure.
DE: 4239 Limnology
DE: 4815 Ecosystems, structure and dynamics
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly