Figure 2.

Feedbacks between size-specific individual responses to warming and population size structure and biomass. Example of warming effects on European perch (Perca fluviatilis), where (a) size-specific effects of warming on individual energy acquisition (black lines and circles) and use (grey lines) in small (full lines and filled circles) and large individuals (hatched lines and open circles) influence (b) body growth responses to warming, being different for small (full lines, circles) and large (hatched lines, triangles) perch individuals in the whole-ecosystem heating experiment (i) and in the lake temperature gradient study ((ii) and (iii)), and subsequently their (c) mean size-at-age ((i): the heating experiment, (ii) and (iii): the lake gradient). This affects (d) population size structure; (i,ii) show catch in numbers per unit effort per length class in the heating experiment (ii) and control area (i) and mean body size (in mm) for year 1984 and 2003 is inserted as text, in (iii, iv) black dots indicate perch in the lake temperature gradient, and coloured dots the whole-ecosystem experiment in heated (red) and control (blue) areas 4 (open circles) or 23 years (filled circles) after the onset of heating. Changes in (e) population biomass production over temperature result from responses in individual body growth at size (b) and numbers of individuals at size in the population (d), and lead to variation in (f) population biomass with temperature. The total biomass (f) and size composition (d) of individuals in the population impact their (g) prey at lower trophic levels (in addition to the direct influence by temperature on prey individuals). The amount of prey and its variation across temperature (g), in turn, influence the food intake rate of individual consumers (a). (i) in (b,c) are redrawn from Huss et al. [7], while (ii) and (iii) in (b,c), (iii) and (iv) in (d), and (e,f) are redrawn from Van Dorst et al. [4].