Do Low-Mercury Terrestrial Resources Subsidize Low-Mercury Growth of Stream Fish? Differences between Species along a Productivity Gradient
Figure 1
Stable isotopes indicate that brook trout rely on terrestrial subsidies more than Atlantic salmon do.
Points on the scatterplots show the average carbon and nitrogen stable isotopes in brook trout (open circles) and Atlantic salmon (closed circles) at each site against carbon and nitrogen stable isotopes in aquatic prey (same prey value for both species at each site). Error bars are omitted for clarity; SEs of all estimates were less than 0.8 delta units for carbon and 0.6 delta units for nitrogen. The solid lines show the predicted stable isotopes for brook trout or Atlantic salmon with a diet consisting entirely of aquatic prey. The dashed line for carbon shows the predicted isotopes for brook trout or Atlantic salmon with a diet consisting entirely of terrestrially-derived prey.