Fig 1.
Illustrates a typical sampling event using the Field method and presents two sources of variability related to citizen-generated invertebrate data.
In this example, four groups collected a total of 147 invertebrates (mean density = 36.8 per m2) from a 100 m stream reach. Participants collected three 0.1m2 D-net benthic samples from the left, center and right of a stream riffle (a). The invertebrates were composited into a plastic tub (b), transferred to the subsampling tray (c) and invertebrates from five randomly-selected cells in the tray (X) were sorted and counted. Sample-level variability is related to the process of subsampling. Reach-level variability is due to both sample-level variation and reach-scale spatial differences in the invertebrate community. Variability is hierarchically structured with sample-level variability nested within the reach-level samples.
Fig 2.
Map of study watersheds and data collection sites in Oregon, United States.
Black circles show data collection sites. Map scale is indicated within each watershed map.
Table 1.
Summary data from the investigation comparing the Field and Lab methods.
Table 2.
Summary of long-term invertebrate data collected by participants from 2005–2015.
Annual sampling did not occur on the same day each year, so the range of sampling days over the 11-year study period is shown as fall and spring Sampling dates. Total area sampled is the combined area sampled by all groups during each sampling event. Sample event abundance is the total number of invertebrates collected during each sampling event. Mean density is expressed as number of invertebrates per 0.1 m2.
Fig 3.
Mean taxon deviation of the Field method as a function of subsample count.
Fig 4.
Ordinations of invertebrate assemblage at both Balch Creek (n = 6) and Clear Creeks (n = 6).
Ordinations for the Field method (triangles, n = 6) and Lab method (circles, n = 6) are shown with the corresponding Null model assemblage (X, n = 6 at each creek). Symbols represent an individual sample collected at Clear Creek (closed symbols) and at Balch Creek (open symbols). Variance explained by each axis shown in the axis label.
Fig 5.
Partitioned invertebrate density CV for both within-reach spatial and long-term temporal citizen-generated data at Balch and Lookout Creeks.
Within-reach spatial CV was partitioned into subsampling and unexplained components. Long-term temporal CV was partitioned into environmental (ENSO MEI + Sample-Year) and unexplained components.
Fig 6.
Ordinations for both streams (Panel A), Balch Creek (Panel B) and Lookout Creek (Panel C). Participants generated data for the ordinations by sampling the same reach biannually from 2005–2015. Season is indicated for fall (filled symbol) and spring (open symbol) samples. The two-digit number indicates sampling year.
Fig 7.
Linear models and R2 values of invertebrate density as a function of water-year ENSO MEI at Balch Creek (Panel A) and Lookout Creek (Panel B). Sample points are represented by text with season and year indicated.
Table 3.
CV for common families collected in Balch and Lookout Creeks from 2005–2015 for taxa present in at least 5 samples in each season.
Some taxa were only present in either Balch Creek (+) or Lookout Creek (*).
Table 4.
Results of the linear model and variance partitioning for the long-term temporal data.
R2 values are shown for both the linear and LMG regression models. Model parameters (ENSO MEI and sample-year) are expressed as percent explained for the LMG and multiple-linear regression models.