Costs of living in metal polluted areas: respiration rate of the ground beetle Pterostichus oblongopunctatus from two gradients of metal pollution

To address the question about costs of living in polluted areas, biomarkers linked to metabolism were measured in Pterostichus oblongopunctatus (Coleoptera: Carabidae) collected along two metal-pollution gradients in the vicinity of the two largest Polish zinc smelters: 'Bolesław' and 'Miasteczko Śląskie' in southern Poland. Both gradients covered a broad range of Zn and Cd concentrations in the humus layer (109-6151 and 1.48-71.4 mg kg(-1), respectively) and body metal concentrations increased with increasing soil metal concentrations. The whole-organism respiration rate was measured as oxygen consumption with Micro-Oxymax respirometer, and cellular energy consumption-as the activity of electron transport system, which is linked to cellular respiration rate. The significant increase in the whole-organism respiration rate with the body metal concentration was found when taking into account other factors such as body mass, gradient (or year of sampling as the beetles were collected on the gradients in different years) and the interactions: body metal concentrations × collection date, body metal concentrations × body mass, and body mass × gradient/sampling year. However, no relationships between metal concentrations in soil or body metal concentrations and the whole-organism or cellular respiration rate could be detected when using mean values per site, underlining the crucial importance of incorporating individual variability in such analyses. The observed increase of the whole-organism respiration rate with increasing body contamination with metals suggests that P. oblongopunctatus incurs energetic expenditures resulting from the necessity to facilitate metal elimination or repair of toxicant-induced damage.