Figure 5. Two hypothetical scenarios of how stressor effects can propagate across trophic levels leading to complex community outcomes and disruption of species interactions. (Scenario A)Stressor A may disproportionately affect a single functional level (e.g. a keystone predator) which has positive indirect benefits for a consumer and negative
indirect benefits on a producer. Stressor A, for example, may cause high physiological stress in the predator leading to reduced activity and hunting, thus releasing the consumer from density and trait mediated effects of the predator. Even though stressor A also has a physiological cost on the consumer, this cost is exceeded by the benefits associated with lower predation risk and increased foraging opportunities. Conversely, the direct negative effects of stressor A combined with increased top-down effects from consumers, may lead to negative synergistic effects on producers. (Scenario B) Stressor B disrupts the sensory capability of a specialist pollinator leading to decreased foraging activity and pollination of ‘plant A’. A key seed disperser which prefers a diet of ‘plant A’, switches their primary diet to fruits of ‘plant B’ due to a reduction in the availability of ‘plant A’. ‘Plant B’ now benefits both from increased seed dispersal and decreased space competition from ‘plant A’ leading to a fundamental shift in the composition of the plant community. Line thickness denotes size of the stressor effect. Positive/negative symbols represent stressor net effects on each trophic node.