Life in Hot Waters: Live Fast, Die Young

Aquatic ecosystems are strongly affected by alterations in the thermal environment. Coffeen Lake, a cooling source for a central Illinois coal power plant, observes temperatures in excess of 35°C during the summer months due to discharge of thermal effluent. Lake Mattoon is a comparable lake system that is not impacted by thermal discharge. Previous studies demonstrated the average length and weight of bluegill sunfish (Lepomis macrochirus) in Lake Mattoon (132.3 ± 2.2 mm, 59.9 ± 2.0 g) to be greater than Coffeen Lake (75.1 ± 1.1mm, 9.4 ± 0.51g; p < 0.05),  and suggested the average age of a bluegill in Coffeen Lake to be significantly shorter (1 year) than in Lake Mattoon (2.3 years). However, the molecular, cellular, and whole-organism aspects of thermal adaptation in Coffeen Lake bluegill remain uncharacterized. We captured L. macrochirus from Coffeen Lake and Lake Mattoon and adapted the animals to two different temperatures (15° C and 31°C) for two week in laboratory tanks. Measurements of upper critical temperature were performed and respiratory capacity analyzed by using high-resolution respirometry on mitochondria extracted from liver tissue. Additionally, tissue samples were analyzed to determine expression levels of heat-shock proteins and molecular markers of oxidative stress.