  While much has been learnt about the impacts of specific stressors on
individual marine organisms, considerable debate exists over the nature and
impact of multiple simultaneous stressors on both individual species and marine
ecosystems. We describe a modelling tool (OSIRIS) for integrating the effects
of multiple simultaneous stressors. The model is relatively computationally
light, and demonstrated using a coarse-grained, non-spatial and simplified
representation of a temperate marine ecosystem. This version is capable of
reproducing a wide range of dynamic responses.Results indicate the degree to
which interactions are synergistic is crucial in determining sensitivity to
forcing, particularly for the higher trophic levels, which can respond
non-linearly to stronger forcing. Stronger synergistic interactions sensitize
the system to variability in forcing, and combinations of stronger forcing,
noise and synergies between effects are particularly potent. This work also
underlines the significant potential risk incurred in treating stressors on
ecosystems as individual and additive.
