title: Effective long-term ecological monitoring using spatially and temporally nested sampling.
abstract: Effective environmental management requires documentation of ecosystem status and changes to that status. Without long-term data, short-term natural variability can mask chronic and/or cumulative impacts, often until critical levels are reached. However, a trade-off generally occurs between sampling in space and time. This study analyses a spatially and temporally nested long-term (12 years) monitoring programme conducted on benthic macrofauna in a large harbour. Sampling was carried out at six sites for 5.5 years, after which only two sites were sampled for the next 5 years. After this period, all six sites were sampled for another 2 years. While ecology is frequently thought of being highly variable, this design was able to detect trends, and cycles, in abundance, with only around 10% of species at each site exhibiting unpredictable temporal variability. Sites exhibiting similar trends in the abundance of a species over the 12.5-year period were generally spatially contiguous, and the spatial scale of change could be assessed. Continuous sampling at two sites identified whether changes in unsampled sites were related to long-term cycles. Moreover, this sampling provided a long-term background of temporal fluctuations against which to assess the ecological significance of observed changes.
authors.affiliation: National Institute of Water and Atmospheric Research, P.O. Box 11-115, Hamilton, New Zealand. j.hewitt@niwa.co.nz
authors.forename: J E
authors.initials: JE
authors.lastname: Hewitt
authors.forename: S F
authors.initials: SF
authors.lastname: Thrush
mesh_terms: D000818:Animals; D004463:Ecology; D004784:Environmental Monitoring / Q000379:methods*; D012494:Sampling Studies; D012621:Seasons; D013045:Species Specificity