To cope with environmental challenges due to global change, organisms must modulate their physiology to survive. Various environmental stressors like heat and pollution have been suggested to cause increased oxidative stress in animals. However, in many organisms with multiple life-stages, like the Calanoid copepods, how different life-stages respond to environmental stressors remains unclear. The planktonic marine copepod Calanus finmarchicus is a low trophic species, an important food source to several commercially important fish, and a keystone species in the ocean. Therefore, it is important to understand how they respond to stress. To investigate the physiological and life-history effects of critical life-stages of C. finmarchicus to heat stress and oxidative stress, we exposed fertilised eggs and adult males and females to graded doses of paraquat, an oxidative stress inducer, at different temperatures. We measured the eggs’ hatching rate, defined the 96 hours LC50 of paraquat, and examined antioxidant mechanisms by measuring the transcription level of biomarkers genes involved in oxidative damage such as superoxide dismutase in both eggs and adults in response to both heat stress and paraquat treatments. Preliminary results showed no additive nor synergistic effects of heat and oxidative stress on the metabolic response of adult females. We hypothesised that early life stages and adult males are more sensitive to oxidative stress and temperature change than adult females. A better understanding of how copepods respond to environmental changes and the physiological mechanisms underpinning these responses will help us predict marine ecosystem dynamics in relation to global change.