SUPPLEMENTARY INFORMATION
SI1. The effect of experimental treatments on phytoplankton and zooplankton community characteristics
Partial redundancy analyses (RDA) were used to assess the effect of fish stock treatment, artificial refuges and their interaction on phytoplankton and zooplankton community composition. Separate Two-Way ANOVA’s were applied to investigate the effect of experimental treatments and their interactions on phytoplankton biomass, zooplankton biomass and zooplankton body size. With the exception of zooplankton body size, all data were log-transformed (base-10) to improve distributional properties of the data.
Our analyses indicate that the experimental treatments had no effect on the variation in phytoplankton and zooplankton community composition (Table S1), nor did they affect phytoplankton biomass, zooplankton biomass and zooplankton body size (Table S2).
Table S1. The median standard body length and total biomass (in kg. ha-1) of the stocked fish species in each set of 6 ponds that received a different fish functional community treatment. PL= zooplanktivorous fish treatment, B= benthivorous fish treatment, PL+B= combined fish treatment, PL+B+PI= combined fish treatment with piscivorous fish.
median standard body length / PL / B / PL+B / PL+B+PI(min.- max.) / (n = 6) / (n = 6) / (n = 6) / (n = 6)
Perch (Perca fluviatilis) / 9.5 cm (8.5 - 13.5) / 6 / 0 / 3 / 3
Roach (Rutilus rutilus) / 16.3 cm (7.0 - 23.0) / 42 / 0 / 21 / 21
Rudd (Scardinius erythrophthalmus) / 12.0 cm (9.0 - 21.0) / 42 / 0 / 21 / 21
Ide (Leuciscus idus) / 8.5 cm (7.5 - 9.5) / 10 / 0 / 5 / 5
Common carp (Cyprinus carpio) / 11.5 cm (9.5 - 14) / 0 / 100 / 50 / 50
Pike (Esox lucius) * / 9 cm (7 - 13) / 0 / 0 / 0 / 0.63
Total fish biomass / 100 / 100 / 100 / 100
* 150 fingerlings per hectare (average individual body weight 4.2 gr), stocked in early May
Table S2. Results of partial RDA analyses testing for the effect of fish treatment, refuges and their interaction on phytoplankton and zooplankton community composition.
df / R2adj. / F / PPhytoplankton community
Fish / 3 / -0.07 / 0.525 / 0.988
Refuges / 1 / -0.01 / 0.789 / 0.573
Fish*Refuges / 7 / -0.16 / 0.555 / 1
Zooplankton community
Fish / 3 / -0.01 / 0.936 / 0.491
Refuges / 1 / -0.01 / 0.855 / 0.47
Fish*Refuges / 7 / -0.10 / 0.710 / 0.869
Table S3. Results of Two-Way ANOVA testing for the effect of fish stock treatment, artificial refuges and the interaction between both on phytoplankton biomass, zooplankton biomass and zooplankton body size.
Df / SS / MS / F / PPhytoplankton biomass
Fish / 3 / 0.471 / 0.157 / 2.260 / 0.121
Refuges / 1 / 0.031 / 0.030 / 0.439 / 0.517
Fish*Refuges / 3 / 0.234 / 0.078 / 1.123 / 0.369
Zooplankton biomass
Fish / 3 / 2.071 / 0.690 / 1.152 / 0.358
Refuges / 1 / 0.060 / 0.060 / 0.100 / 0.756
Fish*Refuges / 3 / 0.863 / 0.288 / 0.480 / 0.701
Zooplankton body size
Fish / 3 / 0.047 / 0.016 / 0.549 / 0.656
Refuges / 1 / 0.054 / 0.054 / 1.876 / 0.190
Fish*Refuges / 3 / 0.090 / 0.030 / 1.051 / 0.397
Table S4. Mean, median, minimum and maximum for total nitrogen, total phosphorus, N:P ratio, mean chlorophyll a concentration, submerged vegetation cover, zooplankton biomass, zooplanktivorous fish biomass, benthivorous fish biomass, piscivorous fish biomass and the biomass of other fish species in the 24 experimental ponds as measured in 2010.
Variable / Mean / Median / Minimum / MaximumTotal nitrogen (mg L-1) / 2.05 / 1.75 / 1.43 / 4.32
Total phosphorus (mg L-1) / 0.17 / 0.17 / 0.02 / 0.34
N:P (molar basis) / 5.31 / 6.96 / 2.57 / 35.10
Mean chlorophyll a (µg L-1) / 89.46 / 73.30 / 30.10 / 290.01
Submerged vegetation coverage (%) / 17 / 10 / 0 / 95
Zooplankton biomass (dry weight, µg L-1) / 575.10 / 265.64 / 2.95 / 3332.26
Daphnia biomass (%) / 2.80 / 0.01 / 0.00 / 45.21
Copepod biomass (%) / 74.78 / 86.63 / 7.15 / 99.77
Zooplanktivorous fish (kg ha-1) / 40.90 / 10.90 / 0 / 287.50
Benthivorous fish (kg ha-1) / 135.20 / 121.10 / 0 / 364.30
Piscivorous fish (kg ha-1) / 5.10 / 1.20 / 0 / 24.50
Other fish (kg ha-1) / 65.60 / 37.70 / 0 / 268.50
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Table S5. The five linear regression models with the lowest value for the second-order Akaike Information Criterion for small sample sizes (ΔAICc) and the null model for total nitrogen, total phosphorus, phytoplankton biomass, submerged vegetation coverage and zooplankton biomass in the experiment.
explanatory variables / AICc / df / ΔAICc / weight / R2adj.total nitrogen / submerged vegetation, other fish / -3.3 / 4 / 0 / 0.542 / 0.51
other fish, zooplanktivorous fish, submerged vegetation / -0.5 / 5 / 2.79 / 0.134 / 0.50
submerged vegetation / -0.3 / 3 / 3.03 / 0.119 / 0.40
benthivorous fish, other fish, submerged vegetation / -0.1 / 5 / 3.2 / 0.11 / 0.49
zooplanktivorous fish, submerged vegetation / 2.3 / 4 / 5.6 / 0.033 / 0.38
none / 10.6 / 2 / 13.88 / 0.001 / -
total phosphorus / none / 1.3 / 2 / 0 / 0.242 / -
benthivorous fish / 1.7 / 3 / 0.36 / 0.202 / 0.05
zooplanktivorous fish / 2.7 / 3 / 1.36 / 0.122 / 0.01
benthivorous fish, zooplanktivorous fish / 3.7 / 4 / 2.4 / 0.073 / 0.04
other fish / 3.8 / 3 / 2.51 / 0.069 / 0.00
phytoplankton biomass / benthivorous fish, total nitrogen / -5.9 / 4 / 0 / 0.112 / 0.57
benthivorous fish, total nitrogen, other fish / -5.8 / 5 / 0.07 / 0.109 / 0.61
benthivorous fish, other fish, submerged vegetation / -5 / 5 / 0.85 / 0.074 / 0.59
benthivorous fish, other fish, zooplanktivorous fish, zooplankton biomass, zooplankton body size / -3.9 / 7 / 2.02 / 0.045 / 0.66
benthivorous fish, other fish, zooplanktivorous fish, total nitrogen / -3.7 / 6 / 2.22 / 0.037 / 0.61
none / 11.1 / 2 / 17.02 / 0 / -
submerged vegetation / total nitrogen / 37 / 3 / 0 / 0.289 / 0.40
total nitrogen, other fish / 38.6 / 4 / 1.69 / 0.124 / 0.41
zooplanktivorous fish, total nitrogen / 39.3 / 4 / 2.33 / 0.09 / 0.39
phytoplankton biomass, total nitrogen / 39.5 / 4 / 2.57 / 0.08 / 0.38
benthivorous fish, total nitrogen / 39.8 / 4 / 2.89 / 0.068 / 0.38
none / 47.8 / 2 / 10.85 / 0.001 / -
zooplankton biomass / zooplanktivorous fish, submerged vegetation / 48.1 / 4 / 0 / 0.344 / 0.40
zooplanktivorous fish, submerged vegetation, other fish / 48.5 / 5 / 0.39 / 0.274 / 0.44
phytoplankton biomass, other fish, submerged vegetation / 51.2 / 6 / 3.07 / 0.074 / 0.06
phytoplankton biomass, zooplanktivorous fish, submerged vegetation / 51.3 / 5 / 3.22 / 0.069 / 0.37
benthivorous fish, zooplanktivorous fish, submerged vegetation / 51.3 / 5 / 3.23 / 0.069 / 0.37
none / 57.2 / 2 / 9.06 / 0.004 / -
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Table S6. Results of Kruskal-Wallis tests testing for differences in total nitrogen, total phosphorus, chlorophyll a, submerged vegetation coverage , zooplankton body size and zooplankton biomass between 'high density fish', ‘experiment’ and 'low density fish' ponds.
Chi-squared / df / pTotal nitrogen / 22.651 / 2 / <0.001
total phosphorus / 24.192 / 2 / <0.001
Chlorophyll a / 15.461 / 2 / <0.001
Submerged vegetation / 16.319 / 2 / <0.001
Zooplankton body size / 10.906 / 2 / 0.004
Zooplankton biomass / 5.053 / 2 / 0.080
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Table S7. The five linear regression models with the lowest value for the second-order Akaike Information Criterion for small sample sizes (ΔAICc) and the null model for phytoplankton biomass, submerged vegetation coverage and zooplankton body size and zooplankton biomass in the comparative study.
explanatory variables / AICc / df / ΔAICc / weight / R2adj.phytoplankton biomass / total nitrogen / 48.7 / 3 / 0 / 0.241 / 0.38
total nitrogen, total phosphorus / 49.6 / 4 / 0.85 / 0.158 / 0.39
total nitrogen, zooplankton body size / 50.8 / 4 / 2.05 / 0.087 / 0.37
total nitrogen,zooplankton biomass / 51.1 / 4 / 2.36 / 0.074 / 0.36
submerged vegetation, total nitrogen / 51.2 / 4 / 2.46 / 0.071 / 0.36
none / 66.9 / 2 / 18.21 / 0 / -
zooplankton biomass / submerged vegetation / 66.9 / 3 / 0 / 0.533 / 0.19
fish, submerged vegetation / 69.2 / 4 / 2.28 / 0.17 / 0.17
phytoplankton biomass, submerged vegetation / 69.4 / 4 / 2.45 / 0.157 / 0.01
fish / 71.6 / 3 / 4.65 / 0.052 / 0.09
phytoplankton biomass, fish, submerged vegetation / 71.7 / 5 / 4.77 / 0.049 / 0.15
none / 74.2 / 2 / 7.31 / 0.014 / -
zooplankton body size / fish / -122.9 / 3 / 0 / 0.352 / 0.12
fish, phytoplankton biomass / -121.04 / 4 / 1.92 / 0.135 / 0.11
phytoplankton biomass / -120.8 / 3 / 2.14 / 0.121 / 0.07
fish, submerged vegetation / -120.7 / 4 / 2.18 / 0.118 / 0.10
submerged vegetation / -120.6 / 3 / 2.34 / 0.109 / 0.06
none / -119.1 / 2 / 3.8 / 0.053 / -
submerged vegetation / total nitrogen / 64.3 / 3 / 0 / 0.393 / 0.53
total nitrogen, fish / 65.6 / 4 / 1.31 / 0.204 / 0.53
total nitrogen, total phosphorus / 66.8 / 4 / 2.45 / 0.115 / 0.52
phytoplankton biomass, total nitrogen / 66.8 / 4 / 2.46 / 0.115 / 0.52
fish, total nitrogen, total phosphorus / 68 / 5 / 3.69 / 0.062 / 0.52
none / 94 / 2 / 29.66 / 0 / -
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Figure S1. Mean biomass of the overall fish community, benthivorous fish, planktivorous fish, piscivorous fish and other fish in each fish stock treatment (PL= planktivorous fish treatment, B= benthivorous fish treatment, PL+B = treatment with planktivores and benthivores, PL+B+Pi= treatment with planktivores, benthivores and piscivores). Error bars denote the standard deviation of the mean.
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