El Niño-Southern Oscillation (ENSO) events activate long-distance teleconnections through the
atmosphere and ocean that can dramatically impact marine ecosystems along the West Coast of North
America, affecting diverse organisms ranging from plankton to exploitable and protected species. Such ENSOrelated
changes to marine ecosystems can ultimately affect humans in many ways, including via depressed
plankton and fish production, dramatic range shifts for many protected and exploited species, inaccessibility of
traditionally fished resources, more prevalent harmful algal blooms, altered oxygen and pH of waters used
in mariculture, and proliferation of pathogens. The principal objective of the Forecasting ENSO Impacts on
Marine Ecosystems of the US West Coast workshop was to develop a scientific framework for building an ENSOrelated
forecast system of ecosystem indicators along the West Coast of North America, including major biological
and biogeochemical responses. Attendees realized that a quantitative, biologically-focused forecast system is a
much more challenging objective than forecasting the physical system alone; it requires an understanding of
the ocean-atmospheric physical system and of diverse organism-level, population-level, and geochemical
responses that, in aggregate, lead to altered ecosystem states