Figure 1.
Location of shallow study areas.
Map showing locations of study lakes within parkland (north, 95°25′N 45°40′W) and prairie (south, 95°60′N 47°30′W) study regions in Minnesota, USA. Shaded area indicates extent of Prairie Pothole Region.
Figure 2.
Confidence intervals for parameter estimates from regression models of invertebrate variables.
Percentile-based 95% bootstrap confidence intervals for regression parameters associated with each of six invertebrate response variables: small cladocerans, large cladocerans, Amphipoda, Diptera, ETO = Emphemeroptera+Trichoptera+Odonata, Corixidae. For each response, the following predictors were included in the model: I(reg = 2) = an indicator variable equal to 1 if the lake is in the Parkland region and 0 if from the Prairie region [reference level]), I(fc = i) = an indicator variable equal to 1 if fish class = i and 0 otherwise (for i = 1, 2, 3), Pbms = planktivore+benthivore biomass (log transformed), Ps = submerged plant score, Lwaa = surface area of upstream lake watershed, Nwl = distance to the nearest permanent wetland or lake, Pagr = proportion agriculture within the upstream lake watershed. See Methods for additional details.
Figure 3.
Aquatic invertebrate abundance among lakes with different fish communities.
Box plots depicting relative abundance patterns for each of 6 invertebrate response variables (ETO = Emphemeroptera+Trichoptera+Odonata). Fish class indicates fish absence (value = 0) or whether community contained only planktivores (value = 1), planktivores +benthivores (value = 2), or planktivores+benthivores+piscivores (value = 3). Abundance estimates for fishless lakes include supplemental data (values in red = 1999; black = current study) and are included to allow comparisons with fishless lakes. See text for more explanation.
Figure 4.
Comparisons of observed and predicted values from regression models.
Observed vs. predicted values from fitted (robust regression) models, along with a 1∶1 line. Colors depict different fish classifications: green = fishless, black = planktivores, red = planktivores+benthivores, blue = planktivores+benthivores+piscivores.
Figure 5.
Relationships between large cladoceran model predictions and fish communities in study lakes.
Residual values from the large cladoceran model versus relative abundance (mass) of total piscivores, total planktivores, and fathead minnows. Lines depict smooth trends estimated using the “lowess” function in program R. Symbol depicts fish class or fish feeding guild present in lakes (0 = fishless, 1 = planktivores only, 2 = planktivores and benthivores, 3 = planktivores, benthivores, and piscivores).