LB 20-176 - How do introduced predators affect consumer-stress predictions along the estuarine gradient?

Successful invasion by stress-tolerant species could affect consumer-stress relationships along stress gradients, potentially changing the abundance of prey and ecosystem function. Some models, such as the Menge-Sutherland consumer stress model, suggest antagonistic effects between predation and physical or physiological stressors, while other models such as the Menge & Olson additive model suggest additive effects of these two structuring forces. To examine how predation pressure varies with environmental stress throughout estuaries, we deployed standardized baits to measure predation along the salinity gradient of five estuaries in Oregon. While results at one estuary lent support to antagonistic effects consistent with the consumer stress model, another lent support to additive effects. Contrary to either the environmental stress model or an additive model, most often, the relationship between stress and predation was non-linear and peaked mid-estuary, where there are more non-native green crabs, Carcinus maenas. This suggests a more complex model better suits stress gradients with stress-tolerant introduced predators and, perhaps, stress-tolerant native prey.