LAUSR

Fish in northern European lakes must cope with climate change, including frequent extreme weather events, and eutrophication. In terrestrial vertebrates the disruption of local environmental stability can evoke a stress response, with potentially adverse outcomes for growth, reproduction and survival, but the effect of extreme weather events on aquatic vertebrates is not understood. As part of a mesocosm scale multiple-stressor study we investigated (i) whether three-spined sticklebacks (Gasterosteus aculeatus L.) exhibited an acute stress response (by measuring the steroid hormone cortisol) to simulated rainfall events, and (ii) whether any such response was modified by elevated temperature and nutrient concentrations. On two occasions, sticklebacks were sampled 1 h and 24 h following the simulated rainfall event. Cortisol levels were elevated within 1 h of the rainfall event in November in fish from heated tanks (with and without nutrient augmentation). In May, cortisol increased within 1 h of the rainfall event but only in fish from nutrient-enriched mesocosms (heated and unheated). Cortisol had declined to control levels within 24 h on both occasions. This outcome suggests that the acute effect on fish of transient stressors, such as extreme rainfall events, may be modified by other environmental factors, but that interactions between these variables may be difficult to predict.