Supplementary Material– Dionne, K., F. Dufresne & C. Nozais. Variation in δ13C and δ15Ntrophic enrichment factors among Hyalella azteca amphipods from different lakes. Hydrobiologia.
Corresponding author: Kaven Dionne
Université du Québec à Rimouski, Département de biologie et centre d'études nordiques, 300 Allée des Ursulines, Rimouski, QC, Canada, G5L 3A1
E-mail:
Phone number: 1-418-723-1986 # 1175
Fax number: 1-418-724-1849
Appendix 1. Physical and chemical characteristics of each lake (Cond = conductivity, DOC = dissolved organic carbon, Chl a = chlorophyll a).Water conductivity and pH were measured in situ with a Hydrolab MS5 multiparameter sonde (Hach Hydromet, Loveland, Colorado), dissolved organic carbon (DOC) was measured using the protocol of Whitehead et al. (2000)* and chlorophyll a concentration was measured using the protocol of Welschmeyer (1994)*.
Lake / Area(km2) / pH / Cond
(μS cm-1) / DOC
(mg L-1) / Chl a
(mg m-3) / Sediment
type
des Baies / 6.09 / 7.74 / 112.5 / 3.72 / 0.93 / Sand
and gravel
Ferré / 1.14 / 7.90 / 193.3 / 4.63 / 1.08 / Sand
France / 0.18 / 7.60 / 105.6 / 5.65 / 2.28 / Sand
and cobbles
*Welschmeyer, N.A., 1994. Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and pheopigments. Limnology and Oceanography 39: 1985–1992.
Whitehead, R.F., S. de Mora, S. Demers, M. Gosselin, P. Monfort & B. Mostajir, 2000. Interactions of ultraviolet-B radiation, mixing, and biological activity on photobleaching of natural chromophoric dissolved organic matter: a mesocosm study. Limnology and Oceanography 45: 278–291.
Appendix 2.Head lengths of amphipods at the start and at the end of the TEF measurement experiment and number of survivors for each treatment (number of amphipods at the start of the experiment for each treatment = 12).
Lake / Treatment / Head length (mm) / Number of survivorsdes Baies / Start of the experiment / 0.34 ± 0.06
Conditioned birch leaves / 0.36 ± 0.04 / 10
Periphyton / 0.36 ± 0.03 / 11
Cyanoperiphyton / 0.37 ± 0.03 / 11
Ferré / Start of the experiment / 0.32 ± 0.08
Conditioned birch leaves / 0.38 ± 0.02 / 7
Periphyton / 0.35 ± 0.03 / 7
Cyanoperiphyton / 0.36 / 1
France / Start of the experiment / 0.31 ± 0.04
Conditioned birch leaves / 0.36 ± 0.03 / 11
Periphyton / 0.39 ± 0.06 / 8
Cyanoperiphyton / 0.31 ± 0.02 / 4
Appendix 3.Isotopic compositions (in ‰) and C:N ratios of amphipods from the TEF measurement experiment (mean ± SD, n = 5 for all samples except for amphipods feeding on cyanoperiphyton from Lake France (n = 4) and from Lake Ferré (n = 1)).
Lake / Diet / δ13C / δ15N / C:Ndes Baies / Conditioned birch leaves / -23.7 ± 0.5 / 1.5 ± 0.5 / 4.8 ± 0.3
Periphyton / -18.8 ± 1.1 / 5.4 ± 0.4 / 4.9 ± 0.3
Cyanoperiphyton / -25.1 ± 0.6 / 7.4 ± 1.0 / 4.9 ± 0.2
Ferré / Conditioned birch leaves / -26.1 ± 0.5 / 4.4 ± 0.9 / 4.9 ± 0.5
Periphyton / -22.0 ± 1.1 / 7.4 ± 0.3 / 4.5 ± 0.3
Cyanoperiphyton / -26.7 / 9.0 / 5.2
France / Conditioned birch leaves / -25.0 ± 0.8 / 2.0 ± 0.8 / 4.8 ± 0.2
Periphyton / -21.5 ± 1.1 / 4.2 ± 0.6 / 4.8 ± 0.1
Cyanoperiphyton / -23.6 ± 1.0 / 4.7 ± 1.2 / 4.5 ± 0.2
Appendix 4.Isotopic composition for carbon and nitrogen of the food items before and after a soaking treatment of 96 h (mean ± SD, n = 5). White symbols represents pre-soaking composition, black symbols represents post-soaking composition. Circle = conditioned birch leaves, triangle = periphyton, square = cyanoperiphyton.
Appendix 5.Carbon and nitrogen composition of foods (mean ± SD, n = 5).
Food / δ13C (‰) / δ15N (‰) / %C / %N / C:NConditioned birch leaves / -31.8 ± 0.4 / -1.9 ± 0.2 / 46.3 ± 0.4 / 2.6 ± 0.0 / 20.7 ± 0.4
Periphyton / -18.3 ± 0.4 / 1.5 ± 0.1 / 14.0 ± 0.2 / 0.9 ± 0.1 / 18.2 ± 1.0
Cyanoperiphyton / -24.1 ± 0.2 / 4.3 ± 0.5 / 24.3 ± 0.0 / 1.4 ± 0.0 / 20.3 ± 0.3
Appendix 6. Isotopic change parameters estimated using nonlinear curve fitting for amphipods from Lake des Baies feeding on conditioned birch leaves during the diet-switch experiment.
Isotope / δ∞ (‰) / λ (d-1) / Modelestimation (mean ± SE) / t value / p / estimation (mean ± SE) / t value / p / RSS / df
Carbon / -22.7 ± 0.3 / -72.5 / <0.001 / 0.088 ± 0.030 / 3.0 / 0.007 / 6.56 / 19
Nitrogen / 1.7 ± 0.3 / 5.0 / 0.001 / 0.057 ± 0.020 / 2.9 / 0.009 / 9.75 / 19
Appendix 7. Parameters estimated using linear curve fitting for amphipods from Lake des Baies feeding on periphyton during the diet-switch experiment.
Isotope / Intercept (‰) / slope / Modelestimation
(mean ± SE) / t value / p / estimation
(mean ± SE) / t value / p / r2 / F / p
Carbon / -18.9 ± 0.2 / -113.2 / <0.001 / 0.02 ± 0.01 / 2.2 / 0.04 / 0.1482 / 4.872 / 0.04
Nitrogen / 5.7 ± 0.2 / 30.5 / <0.001 / -0.005 ± 0.012 / -0.04 / 0.7 / 0.005 / 0.1495 / 0.7
Appendix 8. Discussion on the δ13C enrichment of amphipods from the controls over the course of the diet switch experiment
There was a slight but significant enrichment in δ13C over the course of the experiment for amphipods feeding on periphyton during the diet switch experiment. It is possible that this slight enrichment in δ13C reflects that amphipods had slightly different feeding habits during acclimation and during the experiment. During the acclimation period before the diet switch experiment, many amphipods from Lake des Baies were kept together in a tank and were fed large chunks of periphyton from the same batch used for the experiments. These large chunks of periphyton may have enabled amphipods to better select the elements they preferred in this food than the smaller chunks of periphyton they were offered during the experiment. This is suggested by the fact that measurements at the start of the experiment are less variable for carbon than latter measurements. We consider that the slight increase in δ13C is negligible in the interpretation of the results of this experiment.
Appendix 9.Two-way ANOVAs to assess if amphipods grew over the course of the diet switch and the TEF measurement experiments. Treatment = amphipods fed on conditioned birch leaves, on periphyton or on cyanoperiphyton or amphipods from the start of the TEF measurement experiment.
Analysis / Effect / df / SS / F / PDiet switch experiment / Period of the experiment / 1 / 0.02 / 7.1 / 0.01
Food / 1 / 0.002 / 0.8 / 0.4
Moment × food / 1 / 0.003 / 1.4 / 0.3
Error / 20 / 0.04
Without cyanoperiphyton / Treatment / 2 / 0.02 / 4.3 / 0.02
Lake of origin / 2 / 0.002 / 0.3 / 0.7
Treatment × lake / 4 / 0.009 / 1.7 / 0.3
Error / 59 / 0.1
Without Lake Ferré / Treatment / 3 / 0.02 / 3.8 / 0.02
Lake of origin / 1 / 0.0007 / 0.04 / 0.8
Treatment × lake / 3 / 0.003 / 0.6 / 0.6
Error / 54 / 0.09
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