Table S1 Information for all lakes involved in the experiment. Data was collected from May 2012 to August 2012 (S.E. Arnott, unpublished data). Lake Opinicon was the source of all mesocosm water, while zooplankton were collected from the other four lakes.
Lake / Latitude (N)Longitude (W) / Area (ha) / Max Depth (m) / pH / DOC
(mg L-1) / Cond.
(μS cm-1) / Av. TP
(μg L-1)
Lindsay / 44°32'14.2"
-76°23'25.1" / 31.5 / 10.9 / 8.09 / 6.65 / 230.5 / 8.6
Long / 44°31'40.5"
-76°24'10.0" / 15.5 / 26.0 / 8.23 / 4.30 / 182.0 / 5.0
Opinicon / 44°33'35.4"
-76°19'41.0" / 788.0 / 11.3 / 8.17 / 6.37 / 192.0 / 13.3
Round / 44°32'16.9"
-76°24'00.3" / 15.0 / 30.1 / 8.14 / 4.00 / 164.0 / 6.0
Warner / 44°31'41.4"
-76°22'53.0" / 9.2 / 6.4 / 8.03 / 7.05 / 246.0 / 10.4
Table S2 Regression values used to calculate zooplankton biomass. Mean length values were derived from a N. Yan et al. unpublished database in which over 300 Ontario lakes were sampled, and all counted zooplankton were measured. References for regression coefficients are provided under the ‘Reference’ heading, and full references are listed following the table. A flat value of 0.2µg dry weight per individual was applied to the rotifers as we did not have mean length values for each species.
Zooplankton / Mean Length (mm) / α / β / Reference / Biomass (µg dry weight)Ancanthocyclops robustus / 1.175 / 9.27 / 3.23 / Rosen 1981 / 4.35
Bosmina freyi/liederi / 0.39 / 21.98 / 3.04 / Bottrell et al. 1976 / 1.25
Ceriodaphnia lacustris / 0.833 / 4.02 / 1.98 / Culver et al. 1985 / 2.8
Calanoid copepodid / 0.59 / 7.05 / 2.4 / Bottrell et al. 1976 / 1.99
Chydorus sphaericus / 0.33 / 14.08 / 1.98 / Culver et al. 1985 / 1.57
Cyclopoid copepodid / 0.44 / 7.05 / 2.4 / Bottrell et al. 1976 / 0.98
Daphnia mendotae / 1.7 / 4.34 / 2.83 / Bottrell et al. 1976 / 19.56
Daphnia pulex/pulicaria / 1.85 / 4.34 / 2.83 / Bottrell et al. 1976 / 24.75
Diacylops thomasi / 0.89 / 5.67 / 1.93 / Culver et al. 1985 / 4.53
Mesocyclops edax / 0.95 / 5.26 / 3.97 / Rosen 1981 / 4.35
Nauplii / 0.13 / 7.05 / 2.4 / Bottrell et al. 1976 / 0.053
Rotifera / NA / NA / NA / Bottrell et al. 1976 / 0.2
Scapheloberis mucronata / 0.58 / 17.66 / 3.08 / McCauley 1984 / 3.3
Skistodiaptomus oregonensis / 1.18 / 7.05 / 2.4 / Bottrell et al. 1976 / 10.42
Bottrell, H.H., Duncan, A., Gliwicz, Z.M., Grygierek, E., Herzig, A., Hillbricht-Ilkowska, A., Kurosawa, H., Larsson, P. and Weglenska, T. 1976. A review of some problems in zooplankton production studies. Norw. J. Zool. 24: 419–456.
Culver, D.A., Boucherle, M.M., Bean, D.J., and Fletcher, J.W. 1985. Biomass of freshwater crustacean zooplankton from length-weight regressions. Can. J. Fish. Aquat. Sci. 42(8): 1380–1390. doi: 10.1139/f85-173.
McCauley, E. 1984. The estimation of the abundance and biomass of zooplankton in samples. In A manual on methods for the assessment of secondary production in fresh waters. Edited by J.A. Downing and F.H. Rigler (2nd edition). IBP Handbook 17, Blackwell Scientific Publications. pp. 228–265.
Rosen, R.A. 1981. Length-dry weight relationships of some freshwater zooplankton. J. Freshwat. Ecol. 1(2): 225–229. doi: 10.1080/02705060.1981.9664034
Table S3 Minimum adequate model (MAM) structure and transformations for all experimental metrics and species from the final sampling date. ‘PA’ and ‘Gradient’ entries under the ‘MAM’ heading represent the categorical and continuous predictors for, respectively, EPA and EGrad that were retained in the MAMs. R2 values represent the variance explained by the overall model. For EGrad, ‘Gradient’ indicates a retained linear term for Hemimysis abundance, ‘Gradient2’ a retained quadratic term, and ‘*’ a retained interaction.
Experiment / Metric / MAM / Transformation / R2EPA / Total abundance / PA / Log / 0.61
Cladoceran abundance / PA / Log / 0.63
Copepod abundance / PA / Log / 0.55
Rotifer abundance / PA / Log / 0.41
Total biomass / PA / Log / 0.72
Cladoceran biomass / PA / Log / 0.76
Rotifer biomass / PA / Log / 0.42
Total richness / PA / Log / 0.41
Cladoceran richness / PA / Log / 0.80
Rotifer richness / PA / Log / 0.32
D. pulex/pulicaria
body size / PA / Log / 0.32
EGrad / D. pulex/pulicaria
initial – final abundance / Gradient2 / None / 0.19
D. mendotae initial – final abundance / Gradient2 / None / 0.29
Unidentified Daphnia initial – final abundance / Gradient / None / 0.32
Cyclopoid copepodid initial – final abundance / Gradient2 / None / 0.22
Euchlanis initial – final abundance / Gradient*Gradient2 / None / 0.34
D. pulex/pulicaria
body size / Gradient / Log / 0.017
Table S4 ANOVA tables for the minimum adequate models used for data from EPA.
Metric / Metric / Sum of squares / Mean square / F / df / P-value / R2Total abundance / PA / 0.48 / 0.48 / 15.59 / 1,10 / 0.0027 / 0.61
Residuals / 0.31 / 0.031
Cladoceran abundance / PA / 1.044 / 1.044 / 16.96 / 1,10 / 0.0021 / 0.63
Residuals / 0.61 / 0.061
Copepod abundance / PA / 0.32 / 0.32 / 12.49 / 1,10 / 0.0054 / 0.55
Residuals / 0.26 / 0.026
Rotifer abundance / PA / 0.21 / 0.21 / 6.98 / 1,10 / 0.025 / 0.41
Residuals / 0.31 / 0.031
Total biomass / PA / 1.54 / 1.54 / 25.56 / 1,10 / <0.001 / 0.72
Residuals / 0.60 / 0.060
Cladoceran biomass / PA / 2.10 / 2.10 / 32.12 / 1,10 / <0.001 / 0.76
Residuals / 0.65 / 0.065
Rotifer biomass / PA / 0.47 / 0.47 / 7.36 / 1,10 / 0.022 / 0.42
Residuals / 0.63 / 0.063
Total richness / PA / 0.022 / 0.022 / 6.91 / 1,10 / 0.025 / 0.41
Residuals / 0.031 / 0.0031
Cladoceran richness / PA / 0.15 / 0.15 / 39.87 / 1,10 / <0.001 / 0.80
Residuals / 0.038 / 0.0038
Rotifer richness / PA / 0.19 / 0.19 / 4.76 / 1,10 / 0.054 / 0.32
Residuals / 0.40 / 0.040
D. pulex/pulicaria body size / PA / 28.61 / 28.61 / 132.15 / 1,275 / <0.001 / 0.32
Residuals / 59.54 / 0.003
Table S5 Regression tables for the minimum adequate models used for data from EGrad.
Metric / Predictor / Estimate / SE / t / df / P-value / R2D. pulex/pulicaria
initial – final abundance / Intercept / -3.72 / 1.30 / -2.87 / 1,18 / 0.056 / 0.19
Gradient2 / 0.013 / 0.0064 / 2.05
D. mendotae initial – final abundance / Intercept / -0.11 / 0.057 / -1.96 / 1,18 / 0.013 / 0.26
Gradient2 / 0.0008 / 0.0003 / 2.75
Unidentified Daphnia initial – final abundance / Intercept / -5.42 / 1.05 / -5.17 / 1,18 / 0.009 / 0.32
Gradient / 0.25 / 0.084 / 2.93
Cyclopoid copepodid initial – final abundance / Intercept / 0.69 / 0.47 / 1.45 / 1,18 / 0.035 / 0.22
Gradient2 / -0.0054 / 0.0023 / -2.28
Euchlanis initial – final abundance / Intercept / -3.96 / 1.71 / -2.31 / 3,16 / 0.017 / 0.34
Gradient*Gradient2 / 0.0053 / 0.0020 / 2.65
D. pulex/pulicaria body size / Intercept / 0.18 / 0.035 / 5.31 / 1,371 / 0.029 / 0.013
Gradient / 0.0066 / 0.0030 / 2.18
Fig. S1 Daytime average temperature (solid line) and overall average (dashed line) air temperature for the QUBS area over the period in which the experiment was conducted. Note that the field site was shaded, and cover was provided to all tanks, which would lead to cooler temperatures than those shown and reduce daily fluctuations.
Fig. S2 Mid-day temperature variability of all mesocosms from EPA (n=12) and EGrad (n=20) on the initial and final sampling dates for each experiment.
Fig. S3 Changes in abundance (initial – final individuals L-1) of rotifers from EGrad across the Hemimysis treatment gradient (0.011, 0.022, 0.033, 0.044, 0.055, 0.067, 0.078, 0.089, 0.01, 0.011 individuals L-1). Abundance values below zero indicate species that increased in density between the initial (day 0) and final (day 5) sampling dates, while values above zero indicate a decrease in density. Best fit lines are only shown for species whose density was related to Hemimysis abundance (P<0.1, plotted based on the minimum adequate models for these species). Note the changing y-axes scales for each panel.