Goal of research is to evaluate effects of habitat change and flow regulation on historic and current estuarine food webs that support diverse juvenile salmonid estuarine life histories.  We will document the existing food web linkages supporting juvenile salmon in the Columbia River estuary, relate these results to their estuarine life histories, and evaluate potential food web responses to historic habitat change and flow regulation. This research will combine stable isotope analyses of organic sources, prey species, and salmon tissues with independent analyses of salmon diet and habitat associations to resolve potential changes in the estuarine food-web pathways supporting salmon and in the organic matter sources of alternate micro- and macrodetritus-based food webs.