Ecotoxiclogical risk from multiple stressors covers any situation where
org- isms are exposed to a combination of environmental stressors. These
include physical and chemical pollutants as well as other stressors such
as parasites and environmental impact (e. g., climate change or habitat
loss). The combi- tion of stressors can result in increased risk to
organisms (either additive or synergistic effects) or decreased effects
(protective or antagonistic effects). The multiple stressor challenge is
an international, multi-disciplinary problem requiring an international,
multi-disciplinary approach. The c- rent approach to multiple stressors
is to examine one stressor at a time and assume additivity. Little work
has been done on combinations of stressors such that potential
interactions can be determined. The problem is very complex. Multiple
stressors pose a whole spectrum of challenges that range from basic
science to regulation, policy and gove- ance. The challenges raise
fundamental questions about our understanding of the basic biological
response to stressors, as well as the implications of those
uncertainties in environmental risk assessment and management. In
addition to the great breadth, there is also great depth in the research
ch- lenges, largely due to the complexity of the issues. From a basic
science point of view, many of the mechanisms and processes under
investigation are at the cutting edge of science -- involving new
paradigms such as genomic ins- bility and bystander effects.