Sublethal 6ppd-Quinone Exposure Impairs Swimming Performance and Aerobic Metabolism in Juvenile Lake Trout (Salvelinus Namaycush)

Abstract

6PPD-quinone, an environmental oxidation product of the rubber tire antioxidant 6PPD, has recently gained recognition as a chemical of concern. Frequently detected in road runoff and surface waters, studies have reported this compound to cause acute lethality in several salmonid species at extremely low concentrations, including lake trout (Salvelinus namaycush; 24-h LC50 = 0.51 μg/L). Following exposure, species sensitive to acute lethality show characteristic symptoms such as gasping, spiraling, increased ventilation, loss of equilibrium, erratic movements, and tumbling. However, there is a deficit of research targeted at understanding sublethal toxicities of 6PPD-quinone exposure, particularly concerning swimming capability and metabolic function. To evaluate these effects, juvenile lake trout were exposed for 20 hours to a measured concentration of 0.46 μg/L 6PPD-quinone in a swim tunnel respirometer to assess temporal changes in standard metabolic rate (SMR) compared to controls. Following exposure, fish underwent a swim trial to determine critical swimming speed (Ucrit), oxygen consumption rate (MO2), active metabolic rate (AMR), aerobic scope (AS) and energetic cost of transport (CoT), followed by analysis of white muscle triglyceride and glycogen concentrations. Results showed that 6PPD-quinone exposure impaired swimming performance, evident by a decrease in Ucrit. Additionally, exposure resulted in decreased AMR, although alterations in SMR were not observed. Decreased concentrations of white muscle triglycerides of swam fish were also observed. These findings suggest that environmentally relevant concentrations of 6PPD-quinone disrupt aerobic metabolic capacity in juvenile lake trout, producing adverse effects that diminish endurance and maximum swim speeds, which may affect survival of fish populations.

Keywords: N-(1, 3-dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone, tire rubber antioxidant, swim tunnel, energy homeostasis, critical swimming speed, energy stores